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حيوان

الكلية كلية العلوم للبنات     القسم قسم علوم الحياة     المرحلة 1
أستاذ المادة هادي مزعل خضير الربيعي       3/27/2011 7:30:16 AM

lecture   1

 

introduction to biological science:

 

                  biology is considered one of the natural sciences, which deals with the study of living organisms. the term biology is derived from the greek word (bios, life + logos, study).

 

                  biology has been divided into two main branches, botany which deals with the study of plant and plant life, and the word is derived from the greek word (botanikos means the herbs). the second, a branch that deals with the knowledge of animal life called zoology, which is derived from the greek word (zoon, animal + logos, study).

 

                  zoology and botany have a large number of specialized branches and no one can know the entire field of biology precisely. they again divided into major fields, that include:

 

1-      anatomy: the study of the structure of living organisms.

 

2-      cytology: the science which deals with the study of structure, function, growth and reproduction of cell components.

 

3-      ecology: the study of the interrelationship between living organism and its environment.

 

4-      embryology: the study of development of the organism from the zygote or fertilized egg.

 

5-      entomology: the science which deals with the study of insects.

 

6-      genetics: the science is concerned with biological inheritance.

 

7-      histology: the study of the structure and arrangement of the tissues of organisms.

 

8-      microbiology: the science which deals with the study of a microscopic organisms, a bacterium, virus or protozoan.

 

9-      molecular biology: this science which attempts to interpret biological events in terms of molecules in the cell.

 

10-                                          parasitology: the study of parasites.

 

11-                                          physiology: this science which studies the life processes and function in cells, organs, and whole organism.

 

12-                                          taxonomy: a study aimed at producing hierarchical system of the classification of organisms, or the naming of organisms.

 

13-                                          virology: the science which deals with the study of virus, and it is specialized part of clinical microbiology.

 

 

 

 

 

manifestation of life:

 

                  although both living and nonliving things are subjected to the common physical and chemical laws, there are several biological manifestation which clearly distinguish. them and are considered the most important biological activities which characterize the living things, and they include:

 

1-      feeding (nutrition): the assimilation of materials for use in metabolism, producing of energy and synthesis of molecules and structures for growth development and reproduction.

 

2-      respiration: the release of energy by oxidation of food molecules to perform many functions (e.g. metabolism, movement).

 

3-      excretion: elimination of metabolic by products and other substance present in excess of requirements.

 

4-      movement (locomotion): either movement of the whole organism or part of it.

 

5-      sensitivity: ability to respond to changes in the environment.

 

6-      growth: the increase in size (development) leading to full mature individual.

 

7-      reproduction: the production of new offspring.

 

 

lecture   2

 

the composition of living matter

 

introduction:

 

                  all plants and animals, including the smallest bacteria, are widely diverse organisms that differ functionally and morphologically but have a very similar chemical composition. all cells contain water, minerals, carbohydrates, lipids, proteins, and nucleic acids. all biological phenomena are ultimately based on biochemical processes. therefore, it is important to understand the nature of the biochemical reactions that occur in the cell. such important processes as photosynthesis, nitrogen fixation, cellular energy transformations, and the genetic control of cell structure and function can best be explained at the molecular level.

 

                  matter and energy are the components of our universe. matter is anything that occupies space and has mass. it can assume the form of a solid (ice), a liquid (water, gas (water vapor), or plasma. whatever from it assumes, it will always occupy space and have mass. energy is defined as the property of matter that enables it to do work. the forms of energy are potential, kinetic, electrical, magnetic, chemical and radiand. chemical energy of food enables the bodies of organisms to perform work. biological systems most often use stored chemical bond energy in order to grow, reproduce, and move.

 

 

composition of matter:

 

                  matter is composed of submicroscopic discrete particles called molecules. these molecules are in constant motion. molecules in turn are composed of elements. the smallest unit of an element that retains the chemical properties of that element is called an atom. using abbreviations, scientists write formulas to represent molecules. a molecule of water is written h₂o. this indicates that water molecules contain two atoms of hydrogen and one atom of oxygen (fig. 2-1).

 

 

 

atomic structure:

 

                  atoms are tiny particles composed of a nucleus with a positive charge and an orbiting election cloud with a negative charge (fig. 2-2).

 

 

the nucleus is composed of protons, which have a positive charge and neutrons, which are uncharged or neutral. the electrons are some distance a way from the nucleus and more in orbit. the addition or subtraction of an electron from an atom creates a charged particle, which is called an ion. all atoms of one element have the same number of protons in the nucleus, and the proton number is different for different element (table 2-1).

 

 

table 2-1: comparison of atomic weights.

 

 

the number of protons in the atomic nuclei of the atoms of an element is called the atomic number of that element.

 

the atomic weight of an element, a relative measure based on assigning a weight of 12 to normal carbon, is computed by the summation of the protons and neutrons in the atomic nucleus (table 2-2).

 

table 2-2: atomic weight of common elements found in biological substances.

 

 

when using atomic weights, one customarily records off these numbers to the nearest whole.

 

                 

 

however all atoms of an element do not necessarily have the same atomic weight, but they do have the same number of proton (atomic number). this small variation found in the atomic weight is caused by a difference in the number of neutron present. some atoms of an element have either more or less than the normal number of neutrons. atoms with the same atomic number but different atomic weight are called isotopes (table 2-3). some isotopes emit radiation and are called radioactive isotopes. the first isotopes discovered were those of heavy oxygen, ¹⁷o and ¹⁸o. the radiation isotope of carbon, ¹⁴c has been most useful in many biological investigations, particularly photosynthesis.

 

 

 

table 2-3: isotopes of hydrogen.

 

 

atoms have properties known as the laws of chemical combination. for instance, when two of more elements combine to form a particular molecule, the unite in a constant and definite way, depending on the valence, or combining power of the element. the valence of an element is the number of electrons each of its atoms has gained, lost, or shared in a combination with other atoms. valence numbers can be positive or negative (fig. 2-3).

 

 

 

 

 

 

 

 

 

 

sodium atom

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

na

na+

cl

cl-

     

sodium ion

chloride ion

chloride atom

molecule sodium chloride ion

 

 

 

 

 

 

 

 

 

fig. 2-3: the chemical union between an atom of sodium and an atom of chlorine to form a molecule of sodium chlorine.

 

chemical reactions:

 

chemical reactions- exchanges of electrons among atoms- can be compactly described by chemical equations. for example, the equation for the formation of sodium chloride is:

 

na⁺ + cl^-                              nacl

 

a + b                                        ab

 

the arrow in the equation designates “forms” or “yields” and shows the direction of chemical change. examples of this sort of reaction are the combination of two ions or two elements. a reaction may also take the form of a dissociation:

 

ab                            a + b

 

2h₂o                        2h₂ + o₂

 

a reaction may also involve an exchange, taking the form:

 

ab + cd                                ad + cb

 

naoh + hcl                            nacl + h₂o

 

lecture   3

 

cell structure, function and division

 

introduction:

 

                  cytology is defined as the science, which deals with the study of the cell structure and function.

 

                  the cell is considered as a fundamental structural and functional unit of living organisms (plants and animals).

 

                  the word cell was used first by an english scientist robert hooke (1665) when he described a tiny little room found in a section of cork by means of magnifying lens. in 1838 matthias schleiden, a german botanist, announced that all plant tissue was composed of cells. a year later, theodor schwann, described animal cells as being similar to plant cells. in 1840 purkinji, a czechoslovakian biologist gave the name to the granutar, gel- like mixture found in the cell, the protoplasm. these studies were carried out with the aid of microscope invented by a dutch microscpist a. van leeuwenhoek (1674). most cells are mictoscopie and some, however, can be, seen with the naked eye, they are many different types of cells, our own tissue and organ are constructed of about 200 different types of cells, it is estimated that there are about 40 billion cells in a human body weighting 75 kilograms. most cells have a diameter ranging between 0.5 to 40 mm (micrometer 1/1000 mm, micron).

 

 

types of cells:

 

                  although most of the cells are microscopic, there are some greater in size, thus the frog egg cells are 1500 mm in diameter, others like never cells may be very small in some of their dimensions but extremely long, it reaches over a meter in length.

 

                    the cells have many different shapes, which entirely depend on their function (fig. 3-1). some are flat circular cells (epithelial cells) from lining of the mouth some are spindle like cells in smooth muscles, irregular like amoeba.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 3-1: types of cells.

 

from the structural and functional point of view, there are two different types of cells. they are prokaryotes, meaning “before the nucleus” are found only in bacteria and blue- green algae. these cells are small (1-5 mm long), they contain a single chromosome consist of a single- large molecules of dna not located in a bound nucleus, but found in a nucleus region, in addition prokaryotes have no histones (specific basic proteins) bound to their dna, and membranous organelles are usually not present, from an evolutionary viewpoint, prokaryotes are considered to be an cestores of eukearyotes. in contrast, eukaryotic meaning good or true nucleus, have cells larges distinct nucleus surrounded by a nuclear envelope, and numerous membranous organelles in the cytoplasm (fig. 3-2). eukaryotes are generally larger than prokaryotes, and probably appeared one billion years ago.

 

   

 

 

 

 

 

 

 

 

fig. 3-2: comparison of prokaryote and eukaryote cells. the prokaryote cells is about one tenth the size of the eukaryote cell.

 

 

general organization of eukaryote cells:

 

                  the cell consists two compartments. the nucleus which is considered the control unit of the cell, and the cytoplasm outside the nucleus, which include the rest of the cell components (fig. 3-3).

 

                   

 

 

 

 

 

 

 

 

 

 

 

 

fig. 3-3: structure of animal cell.

 

 

nucleus:

 

                  it is a large spherical body, which plays the central role in cellular reproduction. it is surrounded by two membranes, that form the double layered nuclear envelope which is perforated by pores, to allow the passage of material between the nuclear contents and the cytoplasm outside the nucleus. two structures found within the nucleus, the chromosomes are found as visible of fine threads called chromatin, when the cell is undergoing division. the other structures are one or more granular oval bodies the nucleoli they are usually two nucleoli which are specialized parts of certain chromosomes, which considered the site of ribosome production that consists of subunits each composed of rna and proteins, and considered ribosome factory. when the ribosomal subunits are mature, they are transported out of the nucleus and assembled in the cytoplasm through nuclear pores.

 

                  it was found that nucleoli were small or absent in cells that have little protein synthesis, e.g. blastomere, sperm cells.

 

 

endoplasmic reticulum (er):

 

it is an extensive system of membrane, present in all nucleated cells, dividing the cytoplasm into compartments and channels, often coated on their outer surfaces by small particles called ribosomes, when no ribosomes are coated on membrane, the er is described as smooth endoplasmic reticulum (ser), and the presence of ribosomes described the er as rough endoplasmic reticulum (rer).

 

the rer includes large sacs called cisternae which are continuous with the outer membrane of the nuclear envelope. from the cisternae, the protein which is synthesized by rer are transported to the golgi body, and the synthesis of proteins for export, is one of the main functions of the rer. the synthesis of lipids and lipoproteins is associated with both rer and ser.

 

the function of ser is detoxification of variety of poisons and drugs involved in glycogenolysis.

 

 

ribosomes:

 

                  ribosomes are the most numerous of cells organelles. they are very small spheriodal particles composed of an equal amount of protein and rna, in eukaryotic cells often found attached to the rer. ribosomes tend to be distributed in the cytoplasm and play a crucial role in translating the message during protein synthesis.

 

 

golgi complex:

 

                  the golgi complex consists of flattened stacks membrane surrounded by tubules and vesicles leading to larger vacuoles filled with a granular content.

 

                  the golgi channels (cisternae) are arranged in parallel and are separated by a space filled with fibers.

 

                  the function is to store, modification and packaging of protein products and serve as distributing centers.

 

                  animal cells usually contain 10-20 golgi complexes.

 

 

lysosomes:

 

                  are intracellular organelles ranging from 0.05 to 0.5 mm in diameter, consist of single membrane enclosing a variety of several digestive enzyme (50 enzymes), and they are released when the lysosome rupture. they are involved in breaking down protein, polysaccharides and lipids. lysosomes are involved in the renovation and turnover of cellular component, digestion of extracellular materials involves in the release of primary lysosomes by exocytosis. the best example of lysosomes function is illustrated by the while blood cells (wbc) engulfing bacteria, which is taken up by the cell and lysosomes fuse with the vacuole containing bacteria and release their hydrolytic enzyme which digest the bacteria.

 

 

centrosomes:

 

                  centrosomes appear normally as small cylindrical body, in the cytoplasm. it measures an average (0.2-0.5 mm). centrosomes are comprised of two cylindrical shape, centrioles lies at right angle to each other forming t shape. each cylinder is made up of nine groups of triple tubules. centrosones are responsible for the formation of basal bodies and cilia in some specialized cells, and has been suggested that centrosome could serve as devices for locating the direction of signal sources in cell division.

 

 

mitochondria:

 

                  mitochondria are diverse in size, shape and number, found in all animal cells. a mitochondrion is surrounded by a double membranes, the outer membrane is smooth and freely permeable, while the inner membrane folds inward into series of imaginations known as cristae (fig. 3-4). within the inner compartment of the mitochondria here is a dense solution known as matrix.

 

                    mitochondria are considered as the power- house of the cells, and is the site of chemical energy that breaks the ilucose and makes it available to the cell to release energy.

 

                  mitochondria are composed mainly of proteins. lipids are present to a lesser degree along with small quantities of dna and rna.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lecture   4

 

membrane transport

 

the structure of the cell membrane:

 

                    because of the cell membrane, cell can exist and survive. it has protoplasmic structure that surrounds the cytoplasm and all cell organelles and inclusions. it is a thin permeable, about 7 to 9 nanometers (nm), also called plasma membrane or plasmalemma. the cell membranes which surround the organelles, have the same basic structure for all but, have little difference in the types of lipids and both number and types of proteins and carbohydrates. cell membrane is composed primarily of a bimolecular layer of lipid (phospholipids and cholesterol), in which are suspended numerous large globular proteins (fig. 4-1).

 

 

 

 

 

 

 

fig. 4-1: structure of the plasma membrane.

 

there is a wide variation in the lipid protein ratio between many plasma membranes. the molecule of the phospholipids bilayers have a polar heads and non polar tails, the polar heads consists of glycerol attached to the phosphate which are soluble in water, that is hydropinghilic (water loving), whereas the non polar tails, are soluble only in fat, that is hydropinghobic (water- fearing). the globular proteins which is embedded in the lipid bilayer, are glycoproteins and have been classified as integral proteins that are protruded all the way on the cytoplasmic side of the membrane. the peripheral proteins, which are loosely bound to the membrane surface and do not penetrate are attached to some integral proteins. it is believed that pores with hydropinghylic surfaces may pass through some of the protein molecule. the  short carbohydrate chain attached to the outside of the membrane are involved in the adhesion of cell to each other and with the recogniti and adhesion processes, between cells, and antibodies, cells and hormones and viruses.

 

                  the function of the protein, is to regulate some chemical reaction, and others involved in the transport of molecules across the membrane through channels located within integral protein these molecules are water soluble substances.

 

                  the concept of plasma membrane structure- drew the attention of two scientists (singer and nicolson, 1972), who proposed the fluid mosaic model of the membrane, in which globular proteins are integrated with the lipid layer, and distributed in a mosaic pattern both on the surface and in the interior of the plasma membrane.

 

 

 

the function of the cell membrane:

 

                  the cell membrane gives mechanical strength, and keep the shape and provide some protection to the cell, besides, it keeps certain things out and let others in, and regulate the internal environment of intracellular compartment inside the cell. all materials that inters or leave a cell, must pass through the channel in the membrane, or through the plasma membrane, and some materials pass across the membrane very freely, others pass with difficulty, and certain substances cannot penetrate at all. there are different ways that substances transport through the cell membrane.

 

 

diffusion:

 

                  diffusion is defined as a continual movement of particles from a region of high concentration to a region of lower concentration until they are evenly distributed. this occurs when two different particles concentration are adjacent. diffusion in gases are very fast, and slow in liquid, whereas extremely low in solid states. the energy that causes diffusion is the random thermal motion of the diffusion molecules. the substances that are moving from a region of higher to a region of lower concentrations are said to move along concentration gradient.

 

                  substances moving the opposite direction, toward a higher concentration of its own molecules moving against gradient, which is analogous to being pushed (uphill). the importance of diffusion is that many substances are transported within and between cells, for example, water, oxygen and carbon dioxide with other simple molecules diffuse freely across the cell membrane. the efficiency of diffusion increases by two factors:

 

1-      the size of the cells.

 

2-      the steepness of the concentration gradient.

 

thus, carbon dioxide is constantly produced as result of oxidation of molecules used to obtain energy, then there will be    a high concentration of co₂ inside the cell than outside, thus            a gradient is maintained between inside and outside, hence co₂ diffuses outside along gradient. conversely, oxygen is used up by the cells in the course of its internal activities, so oxygen present in air, water or blood, tends to move inside the cells by diffusion, again along gradient, similarly within a cell materials are often produced at one place and used at another place, thus                                      a concentration gradient is established between the two areas and the material diffuses down (along gradient) from the site of production to the site of use.

 

osmosis:

 

                  in biological systems, the exchange of water between the protoplasm and the surrounding medium through a membrane from a dilute solution into a more concentrated one is called an osmosis (fig. 4-2). the cell membrane is selectively permeable (table 4-1) or semipermeable, since not all substances may pass into or out of the cell.

 

 

table 4 - 1 selective permeable membrane

 

 

a solution in which the concentration of salt is greater than that inside the cell is called a hypertonic solution and will cause the plant cell to become plasmolyzed. in other words, it loses water and becomes dehydrated through plasmoysis. if the concentration of the salt solution outside the cell is less than that inside the cell, a hypotonic solution, the water will diffuse into the cell, making it turgid.

 

 

 

 

 

 

 

 

 

 

                     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 4-2: osmosis top, balloon of a semipermeable membrane filled with a sugar solution, the molecules of which are too large to pass through the membrane. middle, water does pass through, however. bottom, the result is the swollen balloon.

 

 

 

 

 

 

 

 

 

 

 

 

when the concentration of salt is the same on both sides of the membrane, the outside solution is said to be isotonic (fig.4-3).

 

 

 

 

 

 

 

 

 

 

 

 

fig. 4-3: osmosis in plant cells showing the effect on the cell of different solutions.

normal, or isotonic, solution does not distort the cell. a hypotonic solution, that is, one with a lower amount of salt in the water, causes the cell to swell. the reverse occurs when the solution has a greater amount of salt then does the cell, as can be seen by a shrunken cell in the hypertonic solution. arrows, relative amounts of water entering and leaving the cell. 

 

 

 

 

 

 

 

 

 

lecture   5

 

circulation

 

i. the blood:

 

                  the blood is the medium in which the nutrient molecules by digestion and the oxygen molecules taken in by way of the lungs (or gills) are delivered to the individual cells. the blood also carries a number of other important substances such as hormones, enzymes, and antibodies and waste materials, including urea and carbon dioxide. blood is about 8% of human body weight.

 

 

blood composition:

 

plasma: plasma is a clear, colourless fluid component of vertebrate blood, containing dissolved salts and proteins. because of the dissolved plasma proteins, the osmotic potential of the blood is greater than that of the intestinal fluid, these proteins act to prevent excessive loss of fluid from the blood stream to the tissue.

 

plasma proteins are of three major types. albumin, globulins, and fibrinogen.

 

 

 

 

 

red blood cells (erythrocytes) (rbc):

 

                  they are the most numerous cells of vertebrates blood. they are responsible for transporting oxygen from the lungs to the tissue, and carry carbon dioxide from tissue to the lungs. they are produced in the bone marrow. erythrocytes are biconcare disk- like in shape, with an average diameter of 7.5 mm.

 

                  in human males, there are 5 to 5.5 millions red blood cells per cubic millimeter, whereas, in females 4.5 to 5 millions per cubic millimeter, where as in female 4.5 to 5 millions per cubic millimeter. erythrocytes contain hemoglobin which gives the rbc its red colour. haemoglobin is formed of protein (globin) and an iron containing pigment (haem). haemoglobin plays a role in controlling the ph of the blood.

 

                  the life span is 120 to 130 days, and old erythrocytes are destroyed by the phagocytic cells called macrophages, located in the liver, bone marrow, and spleen. the iron part of haemoglobin is reused again and the rest can be changed to bile pigments and haemosiderine granules.

 

 

white blood cells (leucocytes):

 

                  also called white corpuscle, or white blood cells. large nucleated colourless contains no haemoglobin. however, they contain all cell organoids, have spherical shape with diameter range from 8 to 18 mm. total number is between 4000 to 8000 per cubic millimeter, when increased in number called leucocytosis, and caused by acute and chronic disease, and during delivery, whereas, their decrease in number below 4000/cm³ is called leucopenia, and occurs in typhoid fever and many diseases. leucocytes are developed in red bone marrow and lymphatic tissues. the function of leukocytes is the protection of the body from foreign bodies by the process called phagocytosis, and some can produces antibodies.

 

                  they are classified into two types according to the presence of cyteplasmic granules:

 

 

a. granular leukocytes:

 

                  this type of leukocytes contains specific granules in their cytoplasm, and these include:

 

1.    neutrophils (polymorphs): they have multibobulated nucleus, percentage (55-70%).

 

2.              eosinophils: they have bilobed nucleus, percentage (1-4%).

 

3.              basophils: they have irregular lobes in their nucleus, percentage (0.5-1%).

 

 

b. agranulocytes (non- granuler leukocytes):

 

                  they have no granules in their cytoplasm and they are of two types:

 

1.      lymphocytes: they have large rounded nucleus, percentage (20-30%).

 

2.      monocytes: they have large kidney shaped nucleus, percentage (3-6%).

 

 

blood platelets (thrombocytes):

 

                  very small oval of disc- shaped, non- nucleated bodies, made in the bone marrow. number usually varies from 200 to 400 thousand per cubic millimeter. there function is formation of blood clot, they gather at an injured area and block the bleeding blood vessels and they release serotonin substance which initiates blood clot. the life span of platelets varies between 7 to 12 days.

 

 

blood clotting:

 

                  blood clotting is a complex phenomenon at least 15 factors involved in the process have been identified. the sequence of events begins when plasma encounters a rough surface, such as a torn tissue. this stimulates a chain of chemical reactions resulting in the activation of a substance called thromboplastin. thromboplastin acts to convert the enzyme prothrombin, a plasma protein produced in the liver, to its active form, thrombin:

 

                                                            thromboplastin

 

                  prothrombin                                                                  thrombin

 

 

                  platelets as well as several other factors normally present in the blood stream are required for this series of reactions, which involves several enzymatic steps.

 

                  thrombin converts fibrinogen, a soluble plasma protein to fibrin:

 

                                                                        thrombin

 

                  fibrinogen                                                                        fibrin

 

 

                  the fibrin molecules clump together, forming an insoluble network that enmeshes red blood cells and platelets to form a clot.

 

 

blood groups:

 

                  when an organ is transplanted from a donor to a recipient, it will generally never succeed unless the two individuals are genetically similar. this happens because the protein molecules of the donor is considered a foreign to the recipient. the rejection is the responsibility of the t- lymphocyte. the same happens when we mix two different blood types, blood cells clump together and agglutination will result.

 

                  the human blood group system is one of the best known of the naturally occurring immune reactions, the abo blood groups (table 6-1). this was discovered by the austrian scientist landsteiner (1900), who showed that a, b, or b/o are inherited as dominant genes, thus individuals with gene a/a or a/o for example will developed antigen (blood type a). the presence of a b gene produces b antigen (blood type b). and for genotype a/b both a and b antigens developed on the erythrocytes (blood type ab). type a persons always have anti- b antibodies in their blood, even without prior exposure to type b blood. similarly, type b individuals carry anti- a antibodies. type ab blood has antigen a and antigen b but no anti- a or anti- b antibodies. type o blood has both anti- a and anti- b antibodies. universal donor implies for blood group o, because they lack antigens, on the contrary, blood group ab is called universal recipient, because they have antigens ab on red blood cells antibodies (figs. 6-1, 2).

 

 

 

 

                table 6-1: blood groups.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 6-1: abo blood group.

 

                          blood group “o” known as universal donor,

 

                          blood group ab known as universal recipient.

 

 

 

 

 

 

 

 

 

 

donor cells

recipient serum

o

o

a

a

b

b

ab

ab

 

 

 

 

 

 

 

 

 

 

 

fig. 6-2: blood transfusion.

 

sever and sometimes fatal reactions can occur following transfusions of blood of a different type from the recipient’s. these reactions are the result of agglutination of the blood cells caused by antibodies present in the recipient’s blood. the blood that is shown agglutinating has natural antibodies against the donor blood.

 

 

ii. circulatory system:

 

                  the circulatory system includes, two systems of diverging tubes, the cardiovascular system (sometimes is called vascular system) and lymphatic system. the cardiovascular system is made up of a system of tubes of varying diameter, size and function. in general it is a continuous closed system of tubes comprising heart, arteries, capillaries and veins. the function of circulatory system is to provide sufficient blood flow, carrying oxygen and other nutrients and removing waste products.

 

arteries:

 

                  arteries are considered as distributing vessels, which transport blood from the heart to the tissues. they carry oxygenated blood for an exception to this rule, pulmonary artery carry deoxygenated blood, and divide into smaller vessels called arterioles. all arteries are composed of squamous endothelial layer, attached to a thin basement membrane called tunica intima, followed by layer called tunica media, composed mainly of smooth muscle and elastic tissue. the outer layer, tunica adventitia consists of connective tissue, containing nerves, collagen, and elastic fibers which give their characteristic elasticity.

 

                  the small arteries branched and narrowed into arterioles. they consist only of endothelium and a thin layer of smooth muscle (fig. 6-3).

 

 

 

 

 

 

 

 

fig. 6-3: structure of arteries, veins and capillaries.

 

 

capillaries:

 

                  the capillaries are the smallest vessels of both the circulatory lymphatic system. blood capillaries are slightly smaller in diameter than lymphatic capillaries. they are present in huge number, forming complex networks through which the exchange of materials takes place.

 

 

veins:

 

                  veins are relatively thin- walled blood vessels, that carry blood from the capillaries through venules (diminutives of veins) to the heart. they contain valves to prevent blood flowing backward. veins are larger than arteries and differ structurally in the layer of tunica media, that are thinner in veins. all veins carry deoxygenated blood (except pulmonary vein).

 

heart:

 

                  the heart is a muscular pumping organ of the cardiovascular system. it lies ventrally near the anterior end of the trunk, located behind the breast bone. the heart is divided by fibromuscular septum into two lateral halves each consisting of a thin walled receiving chamber or atrium, and a thicker, muscular pumping chamber or ventricle (fig. 6-4).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 6-4: gross anatomy of the heart.

 

 

                  blood enters the right atrium from the rest of the body through the superior and inferior vena cava. it passes through the tricuspid valve to the right ventricle and is pumped to the lungs by left and right pulmonary arteries through a valve (the pulmonary semilunar valve) during systole phase.

 

                  blood returns from the lung by way of pulmonary veins (four veius two from each lung) to the left atrium (or auricle). the contraction of the left atrium forces the blood through a valve (the bicuspid or mitral valve) into the left ventricle. the blood with fresh oxygen pumped to the largest artery in the body, the aorta through a valve (the aortic semilunar valve).

 

 

 

 

contraction of the heart:

 

                  the initiation of the heart is originated by a specialized muscle tissue. the sino- atrial node or s-a node, located on the wall of the right atrium (fig. 6-5).

 

 

 

 

 

 

 

 

 

 

fig. 6-5: intrinsic conduction system of heart.

 

 

this tissue serves as the pacemaker of the heart. the wave of contraction reaches a second mass tissue, the atrioventricular node or a-v node, situated near the partition between the right atrium and the ventricle. the excitatory activity spreads quickly to all parts of the ventricle by special fine fibers called bundle of his.

 

 

blood flow and blood pressure:

 

                  contraction of the heart generates blood flow through the vessels (arteries, arterioles, capillaries, venules, veins). the velocity of flow at any point is related to the total cross- sectional area of that point of the circulation, (i.e. the cross- section area of the sum of all capillaries or arteries at that point in the circulation). the highest speed of blood flow occurs where the total cross- sectional area is smallest and vice versa, so the arteries have the smallest total cross- sectional area whereas, the capillaries have by for the largest. thus the highest velocities occur in the aorta and pulmonary artery. then velocity falls gradually as blood flows through, the capillaries, but it rises again as blood flows through the veins (fig. 6-6). this mechanism allows the exchange of materials between blood and tissue as a result of slow of blood in the capillaries.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 6-6: relationship between blood flow, velocity and total cross- section area.

 

 

                  blood pressure refers to the force exerted upon the walls of the blood vessels. this force is generated by the pumping action of the heart. during heart beat cycle, the maximal arterial pressure (systolie pressure), and minimum in diastolic pressure and given in mmhg. when the arteries narrow into arterioles, and the blood flow blecoms slow and thus the blood flow to all body organs. at this point the arterial end of the capillaries have hydrostatic pressure equal to 40 mmhg. consequently, a net filtration pressure (the hydrostatic pressure which tends to force fluid out, and less the osmotic pressure, which tends to draw water back) of about 15 mmhg (because protein pressure of about 25 mmhg), at the arteriole end of the capillaries. water and dissolved substances are forced out of the capillaries, and circulate through intestinal spaces, as the blood flows through the venous capillary, the blood pressure falls to 15 mmhg. at this point, the hydrostatic pressure is less than the osmotic pressure because of the plasma protein still approximately 25 mmhg, and water drawn back into the capillaries .

 

                  the blood pressure is governed by cardiac accelerating center, situated in the medulla of the brain. the normal arterial pressure in adult humans varies only between 120 mmhg (systole) and 80 mmhg (diastole).

 

 

 

cardiac output and stroke volume:

 

                  the total volume of blood pumped by the heart per unit time, may be expressed either as stroke volume (ml/beat), or as minute volume (ml or l/min.). cardiac output corrected for body weight may be written as ml / kg / min. in a healthy young man this amount to a bout 5.6 liters/min. or 80 ml/kg/min.

 

                  cardiac output                        heart rate x volume of blood.

 

                  heart rate                                          beat per minute = 72

 

                  volume of blood                                   liters per beat = 0.078

 

                  cardiac output                       = 72 x 0.078

 

                  cardiac output                       = 5.6 liters per minute.

 

                  the stroke volume of blood pumped by one ventricle during a single heart beat. the mean stroke volume can be determined by dividing cardiac output by heart rate.

 

 

the rh factor:

 

                  a once common medical problem caused by the immune system is hemolytic anemia of the newborn, which is due to a blood factor, the rh factor, the rh factor (named after the rhesus monkeys in which the research leading to its discovery was carried out). during the last month in the uterus, the human baby usually acquires antibodies from its mother. most of these antibodies are beneficial. an important exception, however, is found in the antibodies formed against the rh factor, which is a genetically determined substance found on the surface of red blood cells. if a woman who lacks the rh factor (that is, an rh- negative woman) has children fathered by a man homozygous for the rh factor, all the children will be rh positive, if he is aheterozy got about half of the children will be rh positive. when she is first pregnant with an rh-positive child, an rh- negative woman will generally form antibodies to the rh factor at the time of delivery (fig. 6-8), when blood from the infant enters the mother’s blood stream. these antibodies persist and in subsequent pregnancies can be passed in to the fetal bloods stream during the last month in the uterus, causing destruction of the red blood cells in an rh - positive fetus. now that its cause are recognized rh disease can be prevented by injecting the rh- negative mother, within 72 hours of her delivery, with antibodies against the fetal rh red blood cells in her system, thus destroying the cells and preventing them from triggering antibody production.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 6-8: the rh factor.

 

a.      fetal blood cells spill across the barrier that separates the maternal and fetal circulations. antigens on the red blood cells of the rh- positive fetus stimulate the production of antibodies by the mother immune system. these antibodies remain in the mother’s bloodstream indefinitely.

 

b.      the antibodies pass through the barrier from the maternal blood to the blood of the fetus. if the fetus is rh positive, the antibodies react with the antigens on its red blood cells, destroying them.

 

 

lymphatic system:

 

                  it is an independent system of blind ending thin- walled vessels. these vessels are called lymph vessels, which are distributed throughout most of the body. these lymphatic capillaries join to form extensive network reaching to all tissues. the larger lymphatic vessels drain via a thoracic duct into the anterior vein.

 

                  the walls of lymphatic vessels are composed of a single layer of endothelium.

 

                  the lymphatic system serves three main functions:

 

1.      rerturn to the blood excess fluid and protein.

 

2.      fat and high molecular weight hormones a bsorbed from the gut, is released the blood by lymph vessels rather than by blood vessels.

 

3.      involved in the body defense against infection by producing lymphocyte and monocyte in the lymph node.

 

 

lymph:

 

                  it is a fluid drained from blood capillaries in mammals in response to high pressure at the arterial end of the capillary bed. lymph is similar to plasma (except for a much lower concentration of plasma protein) baths the tissue and acts as a medium in which substance is exchanged between capillaries and cells. it may contains some harmful substance so, it is filtered in lymph nodes and nodules (fig. 6-9a). lymph flows in one direction inside the lymphatic capillaries and lymphatic vessels (fig. 6-9b), and the most important functions of the lymph are:

 

1.      as a mediator between tissue and blood. drains the fluid from tissue and drains it up in the venous blood.

 

2.      destroy bacteria by the lymph gland.

 

3.      transport fats absorbed from the digestive tract to the blood stream.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 6-9: a- human lymph system.

 

                                                                          b- diagram of a lymph node.

 

 

 

 

 

 

lecture   6

 

respiration:

 

                  all living organisms able to release energy during a process called respiration, which is defined as the oxidation of food molecules by cells, or the process of taking oxygen into the cells, using it for the release of energy from food materials and the elimination of subsequent waste products (carbon dioxide and water).

 

                  some of the simple organisms, including certain bacteria and yeasts, as well as a few invertebrate species, can live indefinitely under totally anaerobic (oxygen-free) conditions, the anaerobes fall into two groups:

 

1.        obligatory anaerobes (those that can not grow in the presence of oxygen i.e. they are poisoned by oxygen, e.g. the bacteria clostridium botulism.

 

2.        facultative anaerobes, like the yeast that survive and reproduce well either in the absence, or presence of oxygen.

 

the oxygen utilized by living individuals and the waste carbon dioxide release out of the cells takes place by diffusion, which diffuses along the concentration gradient (partial pressure).

 

                  this is true of all cells, whether an amoeba, paramecium, liver cell, or a brain cells. but substances can move very short (less than 1mm) to diffuse and this no problem for very small animals in which each cell is quite close to the surface. diffusion cannot meet the need of large individuals in which cells in the animal’s interior may be many centimeters from the air or water serving as the oxygen source.

 

                  the nature of the environment plays an important role in animal respiration, so air contains oxygen 20 times more than water. it contains 9 ml/l at 4 c^o at saturation, whereas, air contains 210 ml/l. hence, the aquatic animals would have a problem of low concentration of oxygen, together with other factors, which allow the aquatic animals to possess successfully ways of getting oxygen from water.

 

 

kinds of respiratory organs:

 

1. cutaneous respiration:

 

                  it is most common in protozoa, sponges and many worms, where certain amount of gas exchange can take place between the skin and the environment, is effective in very long narrow animals like fish with favorable mass to surface area ratio.

 

                  cutaneous respiration is important in all amphibians, approximately 80% of co₂ is released through the skin. frogs use the cutaneous respiration during winter (hiberbation), when it spends cold spell in a pond or lakes.

 

 

2. lungs

 

                  a lungs is vascularized air sac. the exchange of gases between the environment and the body tissue depends on an intermediate circulating fluid. lung do not confine to vertebrates only, but they are found in some invertebrates (snails, scorpions, some spiders and some small crustacean). they are called book lung, consist of many parallel air pockets extending into a blood filled chamber. they derived their name from resemblance to the leaves of partially opened book.

 

                  the mammalian lungs consist of a complex network of tubes and sacs. they are basically alveolar lung, in which each entering bronchus is divided into smaller and smaller bronchioles, which finally terminate in microscopic alveoli. the alveoli are too small, that they would be collapsed by the fluid moistening the respiratory membranes.

 

 

3. trachea:

 

                the insect and some other terrestrial forms have an unusual means of respiration, consisting of two systems of cutical- line air ducts known as trachea, that pipe air directly into the parts of the body. gases must pass through trachea by diffusion. air enters the trachea system through structures (spiracles) on each side of the body. carbon dioxide diffuses out in the opposite direction. in this system, blood is not needed to transport the respiratory gases. the cells have a direct pipeline to the outside.

 

 

 

 

4. gills:

 

                  they are respiratory organs, which are appendages present in the body surface of aquatic animals. they are of two types, the external gills, which are an expansion of particular area of highly vascular surface epithelia such as dermal papulae (starfish), and the internal gills, found in fish, such as a thin filamentous structure containing vessels rich in blood, and flow is opposite to the flow of water through the gills to get more oxygen from the water.

 

 

human respiration system:

 

                  the respiratory system consists of the lungs and the airway leading to them, the thorax and its pleural sac, the diaphragm and muscles of the thorax, and the afferent and efferent nerves connected with these structures. the airways are the nasal cavity, pharynx, trachea and bronchi, which function as a continuous air tube to the lungs (fig. 7-1).

 

                   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 7-1: the human respiratory system.

 

                  the nasal cavity is lined with mucous membrane, which is most and contains numerous glands, for moisturizing the inspired air.

 

                  the pharynx is a space, or common passageway for the respiratory and dijestive tubes. the larynx (voice box), is an air passage situated in the middle of the front of the neck, it serves as the principal organ of phonation, and as a valve to prevent the passage of food and fluid.

 

the vocal cord, which is attached to plates of cartilage on each side, form the boundary of the glottis. the trachea (wind pipe) is the main tube connecting the larynx with two principal bronchi, and carrying air to and from the lungs. its membrane has numerous mucous glands, with ciliated epithelium, together they help to clean the trachea of dust and other particles. the bronchi are similar in structure and function to the trachea. they branch into bronchioles. the lungs are two elastic membranous sacs. they contain many tubes, bronchi bronchioles and alveolar sacs. these sacs connect by way of their atria, with the alveolar ducts, which are direct branches of the bronchioles (fig. 7-2). the bronchioles are millions of tiny tubes, formed by complex branching and rebranching of the two main bronchi after they enter the lunges. the lung is covered by a thin moist membrane (visceral pleura), which secretes a watery fluid (surfactant), that facilitates movement during breathing. the space between the pleura is called the pleural cavity. the diaphragm is the principle muscle of respiration, separating the chest cavity and abdomen.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 7-2: the enlargement of bronchiole and air sac with their blood supply.

 

 

mechanism of breathing:

 

                  inspiration, is defined as breathing in, when the diaphragm contracts and moves downward, expanding the chest cavity from top to bottom. the muscle between the ribs pull the ribs upward and outward, expanding the chest cavity from front to back. this series of automatic actions creates a lowered air pressure in the lungs, and air actually rushes in and fills the lungs.

 

                  expiration (breathing out) usually takes place as the diaphragm and ribs muscles relax, and the size of the chest cavity is reduced, air is forced out of the lungs.

 

                  the average normal rate of breathing is about 18 per minute, it decreases with age, being very rapid in babies, but slow in old people. breathing is not a voluntary act.

 

 

transport of o₂ and co₂:

 

                  breathing is normally involuntary and automatic but comes under voluntary control for talking, singing, coughing, eating and numerous other activities. breathing is under the control of brain (medulla oblongata). the rhythm of breathing is regulated by the carbon dioxide quantity in the blood. exercises rais the co₂ level and the breathing rate increases at 5500 meter, the highest human habituation. there is only about half as much oxygen as on at sea level.

 

                  the oxygen is transported together with small amount of co₂ by respiratory pigments in haemoglobin, a protein containing iron within rbc of all vertebrate and some invertebrates, haemoglobin is made up of 5% heme and 95% globin. each gram of haemoglobin can carry a maximum of 1.3 ml. oxygen.

 

                  haemoglobin consists of four polypeptide chains each of which is combined with an iron- containing molecule known as heme. haemoglobin molecules are manufactured and carried in the red blood cell. mature rbc contains about 265 million molecules of haemoglobin. these molecules are able to combine with o₂ and collected in the lungs after releasing in the tissue. combination of oxygen with haemoglobin depends on the partial pressure of o₂ (po₂). oxygen (o₂) is diffused from air into the alveolar capillaries, when the po₂ is high and most of the haemoglobin in combination with o₂, some of o₂ diffuse to the tissue when the po₂ is low. to explain the oxygen requirements by tissue, the po₂ leaving the lung is 100 mmhg, at this pressure haemoglobin is saturated with oxygen as the haemoglobin molecules travel through the tissue capillaries, the po₂, dropings, and as it dropings, the oxygen bound to the haemoglobin molecules is given up, little o₂ is yielded as the po₂ dropings from 100 mmhg to 60 mmhg. when the po₂ dropings below 60 mm hg, oxygen is given up much more readily.

 

the po₂ of the blood in the tissue capillaries is normally about 40 mm hg, when the blood leaves the capillaries its haemoglobin is still 70% saturated. this is considered as a reserve when the body needs more o₂ as during the exercise.

 

blood that unload oxygen to the tissues from the lungs, carries co₂ back to the lungs. co₂ is transported in the following reactions. most of the co₂ (about 65%) is carried in the blood as bicarbonate (hco₃). bicarbonate ion is produced in two stages of reaction. first, carbon dioxide combines with water to form carbonic acid. this reaction is catalyzed by the enzyme carbonic anhydrase found in red blood cells. then carbonic acid, a weak acid, dissociate to yield bicarbonate and hydrogen ions.

 

carbonic anhydrase

 

                co₂                +      h₂o                                                h₂co₃

 

carbon dioxide                      water                                                      carbonic acid

 

  h₂co₃                                            hco₃^-          +                h⁺

 

                                                                                                  bicarbonate ion                hydrogen ion

 

 

the reaction is of two directions depends on partial pressure of co₂ in the blood. in the tissue of low partial pressure of co₂ in blood, bicarbonates dissociates to form co₂ and water. the co₂ diffuses from the plasma into the alveoli and flows out of the lungs with the expired air. partial pressure of co₂ in the blood affects haemoglobin affinity for oxygen. in the tissues where more co₂ is taken up by the blood result in increasing acidity, so haemoglobin affinity for o₂ decreases and so it gives up its o₂ more readily.

 

control of breathing:

 

                  respiration is controlled by neurons in the brain stem, which become active spontaneously and activate the motor neurons in the spinal cord that stimulate the diaphragm and intercostal muscle to contract. the respiratory neurons receive signals from receptors sensitive to co₂, o₂ and hydrogen ion which is simultaneously monitored by centers in the brain.

 

                  when pco₂ increase, breathing becomes deeper and faster allow more co₂ to leave the blood.

 

 

lecture   7

 

nutrition and digestion:

 

                  all living organisms need food to provide materials for production of new, tissue and the repair of old tissue, and for use as an energy sources.

 

                  to meet these requirements, different organisms obtain their food in many ways, thus autotrophs organism (holophtic), synthesizes complex organic compounds, from single non-living inorganic compounds by the process of photosynthesis. heterotrophs obtain organic compounds by feeding on other organisms and can be classified into carnivores, herbivores and omnivores.   

 

                  nutrition is the key to success of any species. animals use various ways to feed. certain protozoa, endoparasites, and aquatic invertebrates absorb the nutrient molecule through their body surface. endocytosis which consists of both pinocytosis (cell drinking) and phaocytosis (cell eating), are familiar in protozoa such as, paramecium occurs in some digestive tissues of many metazoa. sessile animals wait for food to come to them.

 

                  this group of marine and fresh water environment depends on water current to carry small organisms. this method is filter feeder and occurs in some sponges and bacteriophages. piercing and sucking another way to obtain food, occurs among vampire bats, leeches (through blood suckers), mosquitoes and lice, lower vertebrates have pointed teeth to cut the prey into pieces small enough to swallow. mammals have different types of teeth, incisors, canines premolars and molars each adapted for specific functions.         

 

 

essential components of food and their general function:

 

                  nutrients are substances that serve as a source of metabolic energy. animals vary in their nutritional needs and within species. those need, vary in different aspects, such as body size, composition, activities, age, sex and reproductive functions. to meet these requirements food just include carbohydrates, proteins, fats, water, minerals, salts and vitamins. carbohydrates are used as immediate energy fuels (glucose 6-phosphate) or stored (glycogen) energy, which can also convert to metabolic intermediate or to fats. the major sources of carbohydrates are sugars, starch and cellulose found in plants.

 

 

fats and lipids:

 

                  contained in all living tissues. the presence of lipids is important in certain tissue components, such as plasma membrane and myelin sheath of axons. the fats and oils contain a higher proportion of energy rich carbon-hydrogen bonds than carbohydrates. lipids include, fatty acids, monoglycerides, triglycerides, sterols and phospholipids. lipids serve as energy storage forms, and structural purposes as in phospholipids and waxes.

 

 

proteins:

 

                  proteins are the most abundant organic molecules in the living cell, making up more than half of the mass of a cell as measured by dry weight. they are used as structural components of soft tissues and as enzymes. the protein of an animal tissue are composed of long chain of sub-units called amino acids. there are more than 20 different amino acids found in living organisms, bounded together in chains known as peptides, which are the basis of protein structure.

 

                  these amino acids that can not be synthesized by animal, called essential amino acids. animal proteins have more essential amino acids than plants proteins. an human adult required 67 gm of wheat bread to meet his amino acids requirements, but requires 19 gm of meat each day for the same requirements.

 

                  of the 20 amino acids commonly found in proteins, possibly 11 are essential to the humans. the rest can be synthesized. all 20 amino acids are essential for the various cellular functions of the body (table 8-1)

 

 

 

 

 

 

 

 

 

 

 

table 8-1: the main differences between essential and non- essential amino acids

 

 

nucleic acid, minerals, vitamins and water:

 

                nucleic acids are the materials essential for the genes, the units of heredity. all animal cells appear to be capable of synthesizing them from single precursors. there are two major groups of nucleic acid the ribonucleic acid (rna), and deoxyribonucleic acid (dna), which is the primary carrier of genetic information.

 

                  all organisms require certain minerals, which are naturally occurring inorganic substances, some are needed in relatively large quantity, e.g. sodium, chlorine, potassium, phosphorus, magnesium and calcium. other minerals are needed in much smaller amounts, e.g. iron, manganese, and iodine. other are needed only in trace amounts, e.g. copper, zinc, molybdenum, cobalt. the function of these minerals is to assist in cell building and repairing (especially bone, teeth and muscle tissue). some act as components of coenzymes.

 

 

vitamins:

 

                  vitamins are organic compounds found in some foods that are necessary for human nutrition. the lack of any one or more vitamins in the body, results in specific diseases, and in some cases malformations of the skeleton and general disability.

 

                  vitamins are classified as fat soluble (soluble in organic solvents), or water soluble, which includes the b complex and vitamin c. fat soluble (a, d, e and k) can be stored in body fat deposits.

 

 

water:

 

                  the bodies of organisms are composed largely of water, some animal tissues contain up to 95% of water. the living organism gain water by drinking, by digestion with food, or as an end product of cellular metabolism, and water loss occurs in urine, from the skin, with expired gases, and in the faces. water is required as a solvent for many important classes of life chemistry and a major components of all body fluids.

 

 

 

 

 

 

 

 

 

lecture   8

 

endocrine system:

 

                  hormones are organic molecules secreted by glands (fig. 10-1), which are epithelial tissues specialized for secretion of these substances in minute amount that regulates the function of another tissue or organ. glands are divided into two main groups, the exocrine gland, that passes its secretions to a duct system and then to a body surface, e.g. sweet gland, occurs over much of the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 10 -1: some of the hormone-producing (endocrine) organs.

 

body in most mammals and digestive gland. the second group of glands are endocrine glands, that secret hormones directly to the blood stream (or into the extracellular fluid from which the hormones diffuse into blood stream).

 

                  each hormone has a very specific effect but only on particular “target cell”, in the course of their circuit in the blood and interstitial fluid, the hormone molecules typically face receptor molecules located on the surface of the target cell. these proteinaceous receptors are specific for that hormone and convey the signal to the cell interior.

 

                  the amount of hormone produced by an endocrine gland is generally small, with very low concentration in the blood. hormone secretion and circulation is very slow in comparison to nervous system, but both systems function as a single united system, that nervous system controls most endocrine function and on the contrary, hormones act on the nervous system and affect many kinds of animal behavior.

 

 

mechanism of hormone action:

 

                  there are two different mechanisms in the effect of the hormones on their target tissues.

 

 

1. intracellular receptors (cytoplasmic receptors):

 

                  several hormones that are soluble in lipids pass freely through cell membrane like steroids and thyroid hormones, they bind electively to cytoplasmic receptor molecules found only in the target cells, it combines with specific protein molecule, the receptor. the hormone receptor complex moves to the nucleus where it binds to the chromosome, initiating rna transcription leading to protein synthesis.

 

2. membrane receptor (cell surface receptors):

 

                  this group of hormones acts by combining with receptors on the membrane which causes the activation of an enzyme, adenylate cyclase that converts atp in the cytoplasm to cyclic amp which generate acts as a second “messenger” that relays the hormone’s message to the cell’s biochemical machinery, when it alters (stimulates) some cellular process. since many molecules of cyclic amp may be manufactured, after a single hormone has been found, the message is amplified, perhaps many thousands of times.

 

                  cyclic amp mediates the actions of many hormones, including glucagons, epinephrine, adrenocorticophic hormone (acth), they are much too large to penetrate the cell membrane.

 

 

 

 

 

 

lecture   9

 

the nervous system:

 

                  the activity of any animal depends on the information from the receptors to the affecters. the strmulus transmitted through the nervous system. the simplest nervous system is of hydra, consisting of neurons which form a diffuse network. the more organized nervous system is of the planaria (flatworm), those two anterior ganglia (cluster of nerve cell bodies) connected with two condensed cords run along the vertical surface. in earthworm, two longitudinal verve cords fused and many ganglia present, and considered the more centralized nervous system. mollusca have three pairs of ganglia with                    a number of sense organs. in all invertebrates, the nerve cord is located vertically underneath the alimentary canal, whereas, dorsal in the vertebrate and the nervous system is enclosed and protected by the bones of the vertebral column and the skull.

 

                  the nervous system (fig. 11-1) of vertebrate is divided into:

 

a-  central nervous system.

 

b-  peripheral nervous system.

 

the neuron is the functional unit of the vertebral nervous system. it is characterized by a cell body, an axon (which carries impulses away from the cell body) and dendrites (which carries impulses towards the cell body).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 11-1: human central and peripheral nervous system.

 

 

neurons are communicated with one another across a junction called synapse. the neurons are of two types, sensory (afferent, toward some organs or conducting impulses toward the brain), or motor (efferent leading away from some organ, nerve impulses conducting away from brain). the sensory and motor neurons lie outside the skull and vertebral column.

 

 

 

 

 

lecture   10

 

sensory receptors

 

introduction:

 

                  human sense organs are the products of adaptation and evolution. the sensory receptors are many and varied:

 

1.      mechanoreceptors: touch, hearing and position.

 

2.      chemoreceptor: taste and smell.

 

3.        photoreceptors: visions.

 

4.      temperature: receptors.

 

5.      pain receptors.

 

 

some sensory receptors are small and relatively simple in structure. look at the human skin (fig. 12-1), the body’s largest organ. the epidermis is made up mostly of epithelial cells and consists of two layers an inner layer of living cells, and an outer layer of dead cells filled with keratin.

 

the dermis, consisting mostly of connective tissue, contains sensory nerve endings, erector muscle, which raise the hair when contracted and sweat and sebaceous glands, which are modified epithelial cells. the latter produce a fatty substance that lubricates the skin surface. fatty tissue, which makes up the insulating layers below the dermis, is also a form of connective tissue, as is the blood found in the capillaries.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 12-1: a section of human skin

 

 

the simplest receptors are the free nerve ending, which are receptors for pain and temperature and perhaps for other, sensations as well. slightly more complex are the combinations of free nerve ending with a hair and its follicle. each of these little organs is an exquisitely sensitive mechanoreceptors. meissner’s corpuscles and merkel cells are both involved with touch. they are found in particularly sensitive areas of the skin, such as the fingertips, palms, lips and nipples and are especially abundant where hairs are not present. the pacinian corpuscles, lying deeper within the tissues, respond to pressure and vibrations.

 

lecture   11

 

reproduction:

 

                  it is the process of replication, one of the characteristics of living organism, the ability of living organism to give offspring similar to themselves. they are of two types, sexual and asexual.

 

 

a- a sexual reproduction:

 

                  is a characteristic of the formation of a new organism, which is formed from a single parent without gamete production. the offspring is genetically similar copy of itself. asexual reproduction can takes place by:

 

1-      fragmentation: that organisms break down into two or more parts, each part becomes a mature individual. this is found in a variety of animals such as platyhelminthes and echinodermata.

 

2-      budding: unequal division of the organism, it arises as outgrowth (bud) from the parent. the budding is of two types.

 

a-      external budding as in hydra.

 

b-    internal budding as in fresh water sponges.

 

3-      binary fission: division of organism into two approximately equal part, it is common among bacteria and protozoa and to a limited extent among metazoan.

 

4-      multiple fission: the nucleus divides repeatedly before division of the cytoplasm. it occurs in protozoa.

 

 

b. sexual reproduction:

 

                    the combination of sex cells to create offspring having the mixed genetic identity of both parent. there are two kinds of gametes, the ovum (egg) produced by the female and the spermatozoa (sperm) produced by the male (fig. 13-1). the ova are produced relatively in small numbers and non-motile, while the sperns on the other hand are produced in large numbers, motile and are smaller in size. the union of the sperm with the an ovum is carried out by the process of fertilization, which results in the formation of zygote that develops into new organism.

 

 

 

 

 

 

 

 

 

 

 

fig. 13-1: the life cycle of homo sapiens.

 

                  two methods of sexual reproduction (biparental) are found in a variety of animals.

 

1-  parthenoogenesis: development of an egg without fertilization, occurs in a variety of animals, and the best example is in the honey bee. (the queen).

 

2-  hermaphroditism: animals that have both male and female organs located in the same individual, is called (monoecious). the example of this type of reproduction is in earthworm and some crustacea.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

lecture   12

 

embryology:

 

                  embryology is defined as the science which deals with the study of the progressive growth and differentiation that occurs during the early development of an organism. a brief summary of embryology is necessary for the understanding the pattern of an animal, and also for some of the basic concepts used in describing animal groups and their classification.

 

                  the union of the germ cells (male sperm and female ovum), is a process called fertilization. the fertilized egg called zygote, and from the zygote develops a complete animal by the process of differentiation. the development of the embryo, is called embryogenesis.

 

                  the stages of embryogenesis are as follows (fig. 14-1).

 

1.      fertilization: the activation of the egg by a sperm in biparental reproduction, the fusion of these male and female gametes forms a zygote which is the commencement of development.

 

2.      cleavage and blastulation: the process of division of the zygote into smaller and smaller cells (cleavage), leading to the formation of a hollow ball of tiny cells (blastula).

 

3.      gastrulation: the sorting out of cells of the blastula into a three layers (ectoderm, mesoderm and endoderm), that becomes committed to the formation of the future body organs.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

fig. 14-1: stages of embryogenesis

 

4.      differentiation: the formation of body organs and tissues which takes their specialized functions, the basic body plan of the animal becomes established.

 

5.      growth: increased in size of the animal by cell division or cell enlargement, growth depends on food intake to supply materials for the synthesis of protoplasm.