integumantary system محاضرة

INTEGUMENTARY
The skin (integument , cutis ) and its
derivatives constitute the integumentary
system . It form the external covering of
the body and is the largest organ of the
body.
The skin consists of two main layers :
1-Epidermis : composed of a
keratinized stratified squamous
epithelium.
2-Dermis: composed of a dense
connective tissue.
The epidermal derivatives of the skin include the
following organ structures and integumentary
products :
• Hair and hair follicles
• sweat gland
• sebaceous gland
• nail
• mammary glands
Structure of thick and thin skin
• The thickness of the skin varies over the
surface of the body ,
• thick skin is found in palm of hands and
feet while the
• thin skin (which contains hair follicles)
found in the most of the body for example
the skin of scalp .
• The skin consists of the following layers :-
I- Epidermis
The epidermis is composed of stratified
squamous epithelium in which four distinct
layers can be identified .
In the case of thick skin , a fifth layer is
observed . Beginning with the deepest layer ,
these are :
. Stratum basale , also called Stratum germinativum
. Stratum spinosum
. Stratum granulosum
. Stratum lucidum (limited to thick skin)
. Stratum corneum


Stratum basale .
• The stratum basale is represented by a single
layer of cells that rests on the basal lamina
stratum germinativum .
• The cells are small and are cuboidal to low
columnar in shape . They have less cytoplasm
than the cells in the layer above ; consequently
, their nuclei are more closely spaced . This ,
in combination with the basophilic cytoplasm of
these cells , imparts a noticeable basophilia to
the stratum basale .
Stratum spinosum .
• Is at least several cells thick. The cells are
larger than those of the stratum basal.
They exhibit numerous cytoplasmic
processes or spines, which gives this layer
is name.
Stratum granulosum .
• The stratum granulosum is the most
superficial layer of the nonkeratinized
portion of the epidermis. This layer varies
from one to few cells contain numerous
Keratohyaline granules hence the name of
the layer.
Stratum lucidum
• Considered a subdivision of the stratum
corneum by some histologists, is found
only in thick skin
Stratum corneum
• . In the light microscope, it often has a refractile
appearance and may stain poorly. This highly
refractile layer contains eosinophilic cells in which
the process of keratinization is well advanced.
• The nucleus and cytoplasmic organelles become
disrupted and disappear as the cell gradually fills
with the intracellular protein keratin.
II- Dermis
• Attachment of epidermis to dermis is enhanced by an
increased interface between the tissues , one can recognize a
division into two structurally distinct layers .

The papillary layer,
Section of skin cut perpendicular
to the surface reveal numerous
finger- like connective tissue
protrusions, dermal papillae, that
project into the under surface of
the epidermis .When it contain a
blood vessel then called vascular
papillae, but when it contain a
nerve ending (Meissner
corpuscle) then it called nervous
papillae .
The reticular layer , lies
deep to the papillary layer;
it characterized by thick ,
irregular bundles of
collagen and the presence
of more coarse elastic
fibers.
The hypodermis
• the subcutaneous connective tissue , is a
looser connective tissue than the dermis .
It lies deep to the dermis .
• The hypodermis contains variable
amounts of adipose tissue .
Skin appendages .
Hair and hair follicles
• The growing follicle expands at its base to form the pulp ,which
invaginated by tuft of vascularized loose connective tissue called ,a
dermal papilla.
• The outermost part of the hair follicle is a downgrowth of the epidermis
designated the external (outer ) root sheath .The dividing cells in the
germinative layer of the matrix differentiation into the keratin –producing
cells of the hair and the internal root sheath .
• The hair consist of a medulla, cortex , and cuticle , and the internal root
sheath consist of a cuticle ,Huxleys layer , and Henles layer . The
follicle is surrounded by a connective tissue sheath to which the
arrector pili muscle is attached.

• Sweat glands
• A simple coiled tubular structure composed of a
secretory segment located deep in the dermis or in the
upper part of the hypodermis and a directly continuous
duct segment that leads to the epidermal surface. Sweat
gland are classified on the basis of their structure and
the nature of their secretion .Two types of sweat glands
are recognized:
• 1-Eccrine sweat glands.
• 2-Appocrine sweat glands.