MINISTRY OF HIGHER EDUCATION
BABYLON UNIVERSITY
COLLEGE OF DENTISTRY
MANUAL OF
HISTOLOGY
FOR SECOND YEAR
EDETD BY
NADA MEHDI AL-KHAFAJI
RHAB GALIB AL - ZUHAIRY
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M. Sc. In animal physiology
physiology
M. Sc. In animal
THE TISSUES
A.
B.
C.
D.
Four main groups of tissues are known in the body. These are:
Epithelial tissues.
Connective tissues.
Muscular tissues.
Nervous tissues.
A- THE EPITHELIAL TISSUES
These tissues arise from any of the three primary germ layers, the ectoderm,
endoderm or mesoderm. They are almost always found covering a surface, external
or internal, thus mainly performing a protective function. But some of them are
specialized in various ways to perform different other functions.
The epithelial tissues are characterized by having very little intercellular
substance or matrix between their cells and by resting, in the majority of cases, on a
basement membrane formed of the underlying connective tissues.
Classification of Epithelium
Cell arrangement and cell shape classify the epithelium, not by function
-Simple, when it is one cell layer thick
-Stratified, when it is two or more cell layers
1.
2.
3.
4.
5.
The individual cells that compose an epithelium are described as:
Squamous, where the width of the cell is greater than its height
Cuboidal , where the width, depth ,and height are approximately the same
Columnar , where the height of the cell appreciably exceeds the width (the
term low columnar is often used where a cells height only slightly exceeds its
other dimensions ).
Pseudostratified epithelium has the appearance of being stratified. Some of
cells do not reach the free surface; however, all rest on the basement
membrane. Thus, it is actually a simple epithelium.
Transitional epithelium has several layers of cells, characterized by large,
dome-shaped cells at the free surface, that help maintain the integrity of the
epithelium during distention of the various components of the urinary tract.
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CLASSIFICATION
SOME TYPICAL LOCATIONS
Lining of vascular system (endothelium)
,
Simple squamous
Bowman s capsule (kidney)
Lining of respiratory spaces in lung
Small ducts of exocrine glands
Simple cuboidal
Surface of ovary (germinal epithelium)
Kidney tubules
Lining of small intestine and colon stomach
Simple columnar
Lining and gastric glands lining of gallbladder
Lining of trachea and bronchi
Pseudostratified
Lining of differences
efferent ductules of
epididymis
Epidermis
Stratified Squamous
Lining oral cavity and esophagus
Lining of vagina
Sweat gland , ducts larger ducts of exocrine
Stratified cuboidal
glands
Anorectal junction
Largest ducts of exocrine glands
Stratified columnar
Anorectal Junction
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Transitional
Renal calyces
Ureters
Bladder
Urethra
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AV: artriole , vessel supplying glomerulas , BV: blood vessel CT: connective tissue
EP : epithelium ,F : fibroblast nucleus N : nucleus SM: smooth muscle Arrow, site
of bile canaliculus Asterisk,tubule possessing .
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BC : basal cell ,C: cilia, CC : columnar cell CT : connective tissue
Arrows: Fig . 1, tubule composed of simple siquamous epithelium ; Fig.2, lateral
boundaries of cuboidal tubules cells; Fig 3, lymphocytes in epitheliunm
Asterisk, duct or tubule of simple cuboidal epithelium
Glands
Glands are composed of epithelial cells specialized to synthesize and secrete a
specific product. Typically, glands are classified into two major groups reflecting
how their products are distributed:

Exocrine glands, secrete their products onto a surface through ducts or .The
ducts, also composed of epithelial cells.

Endocrine glands, lack a duct system. They secrete their products into the
connective tissue from which they enter the blood stream in order to reach their
target cells. The products of endocrine glands are hormones.
Exocrine glands are classified as either unicellular or multicellular:
1Unicellular glands: are the simplest in structure, the secretory component
consists of single cells distributed among other cells that are not secretory. A
typical example is the goblet cell, mucus-secreting cell positioned among other
columnar cells. Goblet cells are located in the surface lining and glands of the
intestines and in certain passages of the respiratory tract.
2Multicelluar glands: are composed of more than one cell and exhibit varying
degrees of complexity. Their structural organization allows for subclassification
according to the arrangement of the secretory cells and the presence or absence of
branching of the duct elements.
If the duct is unbranched, the gland is called simple; if the duct is branched, it is
called compound. If the secretory portion is shaped like a tube, the gland is tubular;
if it is shaped like a flask, the gland is alveolar or acinar; if the tube ends in a sac like dilation, the gland is tubuloalveolar.
Tubular secretory portions may be single or branched. Thus, exocrine glands may
be described as:
Simple tubular, as in the intestinal glands of the colon
Simple coiled tubular, as in the eccrine sweat glands
Simple branched tubular, as in the submucosal glands of Brunner in the duodenum
Simple branched acinar, as in the cardiac glands of the stomach
Compound acinar, as in the pancreas
Compound tubuloacinar, as in the submandibular gland
Mucous and serous glands, are so named because of the type of secretion produced
.The secretory cells of exocrine glands associated with the various body tubes, i.e.,
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the alimentary canal, respiratory passages, and urogenital system, are often described
as being mucous, serous, or both.
Tubular
Compound acinar
tubuloacinar
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