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Epithelial Secretion/Glands

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الكلية كلية الطب     القسم  التشريح والانسجة     المرحلة 1
أستاذ المادة رنا أياد غالب محمد       12/11/2016 14:33:12
The Objectives
1- Distinguish endocrine from exocrine glands
2-Distinguish unicellular and multicellular glands
3- Recognize that multicellular glands are classified as either simple (single unit) or compound (multiple, branched units.
4- What are the types of secretory products?
5- Explain the mechanisms of secretion in glands?
Epithelial Secretion/Glands
The major function in many epithelial cells is synthesis and secretion of specialized products; organs composed primarily of such epithelia are called glands.
Classi?cation: Glands are classi?ed into two types on the basis of the site of secretion. Exocrine glands secrete into a duct or onto a surface. Endocrine glands secrete into the bloodstream.
1. Exocrine glands
a. Unicellular glands: are composed of a single cell (e.g., goblet cells in tracheal epithelium).
b. Multicellular glands
(1) Multicellular glands are classi?ed according to duct branching as (a) simple glands (duct does not branch) or compound glands (duct branches).
(b) They are further classi?ed according to the shape of the secretory unit as acinar or alveolar (saclike or ?ask like) or tubular (straight, coiled, or branched) Fig1.
(2) A connective tissue capsule may surround the gland, or septa of connective tissue may divide the gland into lobes and smaller lobules.
The type of secretory product of exocrine glands:
(1) Mucus is a viscous material that usually protects or lubricates cell surfaces.
(2) Serous secretions are watery and often rich in enzymes.
(3) Mixed secretions contain both mucous and serous components.
Fig. 1 Types of Exocrine Gland
Mechanisms of secretion :
(a) Merocrine glands (e.g., parotid gland), the secretory cells release their contents by exocytosis.
(b) Apocrine glands (e.g., lactating mammary gland), part of the apical cytoplasm of the secretory cell is released along with the contents.
(c) Holocrine glands (e.g., sebaceous gland), the entire secretory cell along with its contents is released.
2. Endocrine glands may be unicellular (e.g., individual endocrine cells in gastrointestinal and respiratory epithelia) or multicellular (e.g., adrenal gland), and they lack a duct system. These glands that secrete their products through the basal lamina into the blood stream and lack a duct system. These glands often secrete hormones.


المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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