Histology
Introduction & Epithelium
By
Rahat Anarbekov
HISTOLOGY
HISTOLOGY: the study of tissues
- the branch of anatomy that deals with the
microscopic structure of tissues
HISTOLOGY
tissues: groups of cells that are similar in
structure & function
4 main types of tissue
1) Epithelial
2) Connective
3) Muscle
4) Nervous
All tissues are interconnected!
Epithelial Tissue
EPITHELIAL TISSUE
 Also known as EPITHELIUM
 Is the lining, covering, and glandular tissue
of the body
FUNCTIONS OF EPITHELIUM
1)
2)
3)
4)
Protection
Absorption
Filtration
Secretion
Characteristics of Epithelium
1) Cells fit closely together to form
continuous sheets
2) Always one unattached (free) surface or
edge
* called the apical surface
Characteristics of Epithelium
3) Lower surface of epithelial tissue rests
on a basement membrane
* thin layer of extracellular material to which
epithelial cells are attached
Characteristics of Epithelium
4) Epithelium is avascular = no blood
supply of own
 blood gets to these cells by diffusion
from capillaries
5) Epithelial cells can regenerate easily
(if well nourished)
Classification of Epithelium:
Each type of epithelium has 2 names:
First part of name = # of CELL LAYERS
Second part of name = SHAPE
Classification of Epithelium:
First name:
Simple = one layer of cells, very thin
 Functions: absorption, secretion, filtration
Stratified = two or more layers of cells, more
durable
 Functions: protection
Classification of Epithelium:
First name:
Pseudostratified = “false” stratified, cells are
different heights but still one layer
Classification of Epithelium:
Second name:
Squamous = flattened, like fish scales or
floor tiles
Cuboidal = cube-shaped, like dice
Columnar = column-shaped, thinner
Classification of Epithelium:
Simple vs. Stratified
Stratified epithelia named for the cells at the
free surface of the epithelial membrane
Simple Squamous Epithelium



Single layer of flat cells resting on a
basement membrane
Location: lines air sacs of lungs, blood
vessels, lines ventral body cavity
Function: exchange of substances by
rapid diffusion, filtration, secretion
Simple Squamous Epithelium
Simple Cuboidal Epithelium



Single layer of cube-shaped cells resting
on a basement membrane
Location: salivary glands; kidney; ovaries
Functions: Secretion and absorption
Simple Cuboidal Epithelium
Nonciliated Simple Columnar Epithelium



Single layer of nonciliated rectangular
cells resting on a basement membrane
Location: lines digestive, respiratory,
urinary tracts
Function: Secretion and absorption
Nonciliated Simple Columnar
Epithelium
 Contain absorptive and goblet cells
 Absorptive cells- columnar epithelial cells with
microvilli (fingerlike projections that increase
surface area, therefore increasing the rate of
absorption)
 Goblet cells- modified columnar cells that
secrete mucus
 Before mucus is released, it accumulates in the
upper portion of the cell, causing that area to bulge
out and resemble a goblet or wine glass
Simple Columnar Epithelium

Epithelial membranes that line body cavities
which open to the body exterior are called
mucous membranes
Ciliated Simple Columnar Epithelium



Single layer of ciliated columnar cells
resting on a basement membrane
Location: Upper respiratory tract
Function: Moves mucus and other
substances by ciliary action
Ciliated Simple Columnar Epithelium
Stratified Squamous Epithelium



Multiple layers of cells, with squamous at
the apical surface and cuboidal or
columnar lining the basement membrane
Location: Skin, mouth, throat
Function: protection
Stratified Squamous Epithelium
Stratified Cuboidal Epithelium



Two or more layers, with cube-shaped
cells at the apical surface
Location: large glands (sweat glands)
Function: secretion
Stratified Cuboidal Epithelium
Stratified Columnar Epithelium



Two or more layers of cells with
columnar shaped cells at the apical
surface
Location: large glands
Function: secretion
Stratified Columnar Epithelium
Transitional Epithelium

Modified stratified squamous epithelium



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
Basal layer: cuboidal/columnar
Apical surface: vary in shape
Location: urinary tract (bladder, ureters,
urethra)
Function: Cells can slide over each other
to accommodate change in organ size
Organs can stretch without rupturing
Transitional Epithelium
Pseudostratified Columnar Epithelium



Single layer of ciliated
columnar cells of varying
heights resting on a
basement membrane
Location: lines respiratory
tract
Function: Secretion and
movement of mucus by
ciliary action
Pseudostratified Columnar
Epithelium
1: simple squamous
2: simple cuboidal - kidney
3: simple columnar – small intestine
4: ciliated pseudostratified columnar - trachea
5. Stratified squamous epithelium – tongue
Glandular Epithelium
 Function: secretion
 Glandular cells often lie in clusters deep to
the covering and lining epithelium
 A gland may consist of one cell, or a
group of highly specialized cells
 They secrete substances into ducts, onto
a surface, or into the blood
Glandular Epithelium
 Endocrine glands
 Secretions enter extracellular fluid, then
diffuse into the bloodstream without flowing
through a duct
 Secretions are hormones (regulate metabolic
and physiological activities to maintain
homeostasis)
 Ex: pituitary, thyroid, adrenal glands
Glandular epithelium
 Exocrine glands
 Secrete into ducts that empty at the surface of
covering/lining epithelium or directly onto a
free surface
 Skin or interior space (lumen) of a hollow organ
 Secrete mucus, sweat, oil, earwax, milk,
saliva, digestive enzymes
 Ex: sweat glands, salivary glands
Epithelium Review
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2
3
4
5
6
Histology
What is a tissue?
Histology
tissues: groups of cells that are similar in
structure & function
Epithelial Tissue
 Is the lining, covering, and glandular
tissue of the body
Functions of Epithelium
1)
2)
3)
4)
Protection
Absorption
Filtration
Secretion
Pigeons Always
Fly Straight
Characteristics of Epithelium
1.
2.
3.
4.
5.
Abut
Apical surface
Basement membrane
Avascular
Regenerate
Another Awesome Byrne
Anatomy Review!

Characteristics of Epithelium
1) Abut: Cells fit closely together to form
continuous sheets
2) Apical Surface: Always one unattached
(free) surface or edge
Characteristics of Epithelium
3) Basement Membrane: Lower surface of
epithelial tissue rests on
* thin layer of extracellular material to which
epithelial cells are attached
Characteristics of Epithelium
4) Avascular: no blood supply of own
 blood gets to these cells by diffusion
from capillaries
5) Regenerate: Epithelial cells can
regenerate easily (if well nourished)
Simple Squamous
Specimen: artery
Label: apical surface,
nucleus of squamous
cell
Simple Cuboidal
Specimen: Kidney
Label: cuboidal
cell, nucleus
Simple Columnar
Specimen: Small
Intestine
Label: goblet cells
Pseudostrified ciliated columnar
Specimen: Trachea
Label: apical
surface, cilia
Stratified Squamous
Specimen: Skin
Label: squamous
cell, apical surface
Transitional
Specimen: Urinary
bladder
Label: apical surface