TISSUE
Associate Professor:
Dina A.A. Hassan
-Associative professor in pharmacology
-Pharmacology department
-College of Pharmacy
-Sattam Ben Abdulaziz University ,
Al Kharge
Email : da.hassan@sau.edu.sa.
dinallam5@gmail.com
Tissue
• Groups of closely associated cells that are similar in
structure and function are called tissues
• Four primary tissues types:
• Epithelial (covering) tissue
• Connective(support) tissue
• Musclular (movement)tissue
• Nervous (control) tissue
Chapter Outline
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•
•
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Epithelial Tissue
Connective Tissue
Nervous Tissue
Muscle Tissue
SECTION I
EPITHELIAL TISSUE
Epithelial Tissue
• Epithelial tissue is a sheet of cells with little extracellular
material lying in the space between them.
• Epithelial tissue covers all the inner and outer surfaces of the
body including;
• Skin
• Viscera of the digestive and respiratory system
• The lining of body cavities
• Linings of blood vessels
• Most glandular tissue
Special Characteristics of Epithelium
Special Characteristics of Epithelium
1) Cellularity : formed of sheets of cells
2) Polarity:
• All epithelia exhibit polarity where the cells near the apical surface differ
from those at the basal surface
• Apical surfaces can be smooth, most have microvilli, and some have cilia
• The basal surface of epithelium is called the basal lamina, which acts as a
selective filter that determines which molecules are allowed to enter the
epithelium
• Deep to the basal lamina is a layer of reticular fibers belonging to the
underlying connective tissue
• Together the reticular fibers and the basal lamina form the basement
membrane
Special Characteristics of Epithelium
3) Supported by connective tissue
All epithelial tissue sheets rest upon and are supported by connective tissue
4) Specialized connection (cell junctions) between epithelial cells.
5) Innervated but avascular
• Epithelial tissues are supplied with nerve cells
• Epithelial tissues contain no blood vessels
• Epithelial tissue receive nutrients by substances diffusing from blood
vessels in the underlying connective tissue layers
6)Regeneration
• Epithelial cells have a high regenerative capacity
Classification of Epithelia
• Each epithelium is given two names:
• The first name references the number of epithelial cell layers
present
• Simple (one layer)
• Stratified (more than one layer)
• The second name describes the shape of the top cells layer
• Squamous
• Cuboidal
• Columnar
Epithelial shape
• Squamous - flat and
scale-like
• Cuboidal - boxlike
• Columnar - tall and
column shaped
Simple Epithelia
• cells are arranged in one layer that have the same shape
• There are four major classes of simple epithelia
• Simple squamous
• Simple cuboidal
• Simple columnar
• Pseudostratified columnar (Highly modified simple epithelium)
Stratified Epithelia
• cells are arranged in more than one layer
• According to the shape of the top epithelial layer , there
are also four major classes of stratified epithelia
• Stratified squamous
• Stratified cuboidal
• Stratified columnar
• Transitional epithelium (a modified stratified squamous
epithelium)
Simple Squamous Epithelium
• A single layer of flattened cells
• Thin and permeable, this type is often found where filtration
or diffusion is a priority ( function)
• Two simple squamous epithelium have special names related
to their location
• Endothelium (lining blood vessels)
• Mesothelium (found in serous membranes)
Simple Epithelia
Simple Squamous Epithelium
• Simple squamous
epithelium
forming walls of
alveoli (air sacs) of
the lung
Simple Cuboidal Epithelium
• Single layer of cube like
cells
• Important functions are
secretion and absorption
• It forms ducts of small
glands and tubules in the
kidneys
Simple Epithelium:
Simple Cuboidal Epithelium
• Simple
cuboidal
epithelium in
kidney tubules
Simple Columnar Epithelium
• Consists of a single layer of tall, closely packed cells
• It lines the digestive tube from stomach to anal canal
• Important functions are secretion and absorption
Types of Simple Columnar
Epithelium
• Unciliated in the digestive tract
• Ciliated in the respiratory passages
Simple columnar epithelium
• Simple
columnar
epithelium of
the stomach
mucosa
Pseudostratified Columnar
Epithelium
• Single layer of cells of differing heights BUT all of
them rest on the basement membrane.
• The cell nuclei are located at differing levels giving the
false (pseudo) impression of multiple cell layers
• pseudostratified columnar epithelium ciliated in the
upper respiratory tracts
Pseudostratified Epithelium
• Pseudostratified
columnar ciliated
epithelium lining
the human trachea
Stratified Squamous Epithelium
• composed of several cell layers
• Surface cells are flattened (squamous) while deeper cell
layers are columnar
• Types:
• keratinized epithelium has surface layer of dead cells (keratin )
e.g.: skin
• nonkeratinized epithelium lacks the layer of dead cells .e.g.
esophagus & tongue .
Stratified Squamous Epithelium
• Stratified
squamous
epithelium
lining the
esophagus
Stratified Squamous Epithelium
• Keratinized
stratified
squamous
epithelium
lining the skin
Stratified Cuboidal Epithelium
• Generally two layers of cube-shaped cells
• Form large ducts of some glands
• Function to protect
Stratified Epithelium:
Stratified Cuboidal Epithelium
• Stratified
cuboidal
forming a
duct of
parotid
gland
Stratified Columnar Epithelia
• Several Cell layers present
• Basal cells are cuboidal while superficial cells are
columnar
• Rare in the body; found in the large ducts of
some glands and in the male urethra
• Functions include protection and secretion
Stratified Epithelium:
Stratified Columnar Epithelium
• Stratified
columnar
epithelium
lining the male
urethra
Stratified Epithelium:
Transitional Epithelium
• Forms the lining of the urinary system
• The cells vary in appearance depending on the degree of
distension of the organ
• The ability of the epithelium to thin under pressure allows
for a greater volume of urine to pass through these organs
Transitional Epithelium
• Transitional
epithelium
lining of the
bladder,
relaxed state
Epithelial Surface Features
The apical, lateral and basal cell surfaces of epithelia have
special features
• Apical surfaces have microvilli and cilia
• Lateral surfaces have cell junctions
• Basal surface has a basal lamina
Microvilli
• Microvilli are fingerlike extension of the plasma membrane
of apical epithelial cells
• Microvilli maximize the surface area across which small
molecules enter or leave cells .
• Site: In the epithelial cells of the small intestine to increase
surface area for absorption.
Cilia & Flagellum
• Cilia are hair-like, highly motile
extensions of the apical surface of
epithelia cells
• Function: The cilia on an epithelium
bend and move in coordinated waves.
The waves push mucus or ovum over
its surface .
• Site : Respiratory tract, digestive tract
and ovary.
• Flagellum
• Long isolated cilium
• Only found as sperm in human
(site)
Cells junctions
• Cells junctions are characteristic of epithelia cells.
• Types of cell junction:
1 ) Tight junctions:
2) Adherens junctions:
3) Desmosomes:
4) Gap junctions:
Cell Junctions
• Tight junctions:
• So close
• It prevents molecules from passing through
epithelial cells
• Adherens junctions:
• Transmembrane linker proteins
• Desmosomes:
• Filaments anchor to the opposite side
• Gap junctions:
• It is a spot-like junction
• Allow small molecules to move between cells
PHL 212
37
Glandular Epithelia
• A gland consists of one or more epithelial cells that make a
secretion
• Secretions are usually water based fluids containing proteins
• Glands are classified on where they release their secretion:
• endocrine (internal secretion through blood vessels)
• exocrine (external secretion through ducts)
• Exocrine glands are classified by number of cells:
• unicellular exocrine glands
• multicellular exocrine glands
Endocrine Glands
• All endocrine glands eventually lose their ducts and are
considered to be ductless
• Endocrine glands produce hormones that regulate body
functions
• These glands secrete directly into the extracellular space
• The hormones then enter the blood or lymphatic fluid
Endocrine & Exocrine Glands
• Endocrine glands secrete (hormones) directly into bloodstream
• Endocrine gland secrete hormones.
• Pituitary, Thyroid, Parathyroid, Adrenal, Thymus are e.g. of
•
•
•
•
endocrine gland
Exocrine glands are more numerous than endocrine
Exocrine glands secrete their products through a duct onto a body
surface or into a body cavity
Exocrine glands secrete mucous, sweat, oil, saliva, bile, digestive
enzymes, and many other substances
Sweet , sebaceous , salivary and mucus glands are e.g. of exocrine
glands
Goblet
cells
• It is the only
unicellular
exocrine gland
found in
columnar
epithelium cells
lining the
intestinal and
respiratory tract
Multicellular Exocrine Glands
• Structure of multicellular exocrince gland :• Multicellular exocrince gland is formed of two structural
elements:• A duct for delivering secretion
• A secretory unit consisting of secreting cells
• In all but the simplest glands connective tissue surrounds the
secretory unit supplying it with blood an nerve fibers
• Often the connective tissue forms a fibrous capsule and may
subdivide the gland into lobes
Multicellular Exocrine Glands
Structural Classification
• On the basis of their duct structures, multicellular
exocrine glands are either:
• Simple glands have a single unbranched duct
• Compound glands have a branched duct
• The glands are further classified by their secretory units
• Tubular (forms tubes)
• Alveolar (forms sacs)
• Tubuloalveolar (contains both types)
Simple Duct Structure
Compound Duct Structure
classification of multicellular exocrine
glands according to their modes of
secretion
• Merocrine glands (salivary, sweat, pancreas)
• Secret their products by exocytosis and
gland is not altered (fig. a)
• Holocrine glands (sebaceous oil glands)
• The entire cell ruptures releasing the
secretions (fig. b)
• Apocrine glands (mammary glands)
• The apex of the secretory cell pinches off
and release its secretion (fig. c)
(c)