Histology Lectures
TAMS E GODAM
Histology and Molecular and cell Biology Unit
Faculty of Basic Medical Sciences
Epithelial tissues
• Groups of cells that are similar in structure and perform a
common or related functions are called TISSUE
• The study of tissue, or histology, complements the study of
gross anatomy. Together they provide the structural basis for
understanding organ micro-architecture and physiology
Tissues
• The tissues of the human body include four major types: general
function
• Epithelial: covering
• Connective: support
• Muscle: movement
• Nervous: control
Types of Tissue
EPITHELIAL TISSUES
• Epithelium forms the external covering of internal lining of various
structures of the body.
• The word is derived from the words “ epi ” which means upon and
“thallous” meaning Nipple as it was first described on the nipples
• Epithelium can developed from any of the three germ layers. Eg
1. ectoderm- epidermis (skin)
2. endoderm—epithelium (GIT)
3. mesoderm----endothelium (Blood vessels) and lining body cavity it is
called mesothelium.
EPITHELIAL TISSUES
• Epithelial Tissue lacks of blood
vessels, contains little
intercellular material and are
continually being replaced
• They function in protection,
secretion, absorption, filtration,
excretion, and sensory
reception.
EPITHELIAL TISSUES
• Epithelium Tissue has many
characteristics that separate it
from other tissue types
• ET has Polarity- which means it
has an apical surface (near the
top) and a basal surface (near
the bottom)
• Specialized Contacts
• Supported by connective tissue.
• Epithelial membrane comprises of two parts
• Basement membrane
a) The amorphous part
b) Reticular part
Classification of epithelial tissues
Epithelium is classified according to the layer of cells external to the
basement membrane.
1. Simple epithelium– single layer of cells
2. Pseudostratified epithelium– single layer giving a false appearance of
multiple layers
3. Stratified epithelium--- more than one layers
EPITHELIAL TISSUES
•.
Simple Squamous Epithelium
• This tissue consists of a single layer of thin, flattened cells through
which substances can pass easily. So delicate they can easily be
damaged.
• Common site of diffusion and osmosis. Its functions in the exchange
of gases in the lungs
• Lines the air sacs of the lungs (gas exchange), forms the walls of the
capillaries, lines the insides of blood vessels and lymph vessels.
• Covers the membrane that line body cavities.
• EX: Cheek Cells
Simple Squamous Epithelium
Simple Squamous Epithelium
Simple Cuboidal Epithelium
• This tissue consists of a single layer of cube-shaped cells. Usually
have a centrally located spherical nuclei
• The vertical height and the horizontal width are equal.
• It carries on secretion and absorption. Secretes glandular products.
• Covers the ovaries, lines the kidneys, tubules and ducts of certain
glands like pancreas and the liver.
Simple Cuboidal Epithelium
Simple Cuboidal Epithelium
Simple Columnar Epithelium
• The tissue is composed of a single layer of elongated cells whose
nuclei are usually at about the same level, near the basement
membrane.
• Some have cilia some do not
• Secretes and absorbs…this tissue is thick!!
• This tissue lines uterus and portions of the digestive tract like
small/large intestines and stomach.
Simple Columnar Epithelium
Simple Columnar Epithelium
Simple Columnar Epithelium
Pseudostratified Columnar Epithelium
• They appear stratified but are NOT, They appear to have two or more
nuclei but they each reach the basement level.
• Goblet cells scattered throughout the tissue that secret mucus, which
the cilia sweep away.
• It lines tubes of the respiratory system. The mucus and cilia created
by this tissue trap the dust and microorganisms that enter the airway.
Pseudostratified Columnar Epithelium
• “C” the nuclei appear at various
levels giving it the stratified
appearance
• “B” the cilia can easily be seen
Pseudostratified Columnar Epithelium
Pseudostratified Columnar Epithelium
Stratified Squamous Epithelium
• They are named for the shape of the cells and consists of many layers,
relatively thick. Cells nearer the surface are flat where as the deeper
are cuboidal and columnar.
• Tissue can contain Keratin, which is a protein that accumulates and
protect the underlying tissue.
• Epidermis-outer most layer of the skin
• Also lines the skin and lines the oral cavity, throat, vagina, and anal
canal.
Stratified Squamous Epithelium
• Observe that the surface
cells (at B) are flattened
(are squamous).
Stratified Squamous Epithelium
Stratified Cuboidal Epithelium
• This tissue is composed of two or thee layers of cube-shaped cells.
• It lines the larger ducts of the mammary glands sweat glands, salivary
glands, and pancreas. Forms the lining of ovarian follicles and
seminiferous tubules
• It functions in protection.
Transitional Epithelium
• This tissue is specialized to change in response to tension..
• Transition epithelium is unstretched and consists of many layers when
the organs wall contract the tissue stretches and appears thinner
when the organ is distended.
• Forms the lining of the urinary bladder and lines the ureters and part
of the urethra.
Transitional Epithelium
Transitional Epithelium