Tissues
Tissues are group of cells organized to perform specific
function
Tissues of human body
Human body composed of 4 basic tissue types, which are:
1. Epithelial tissue = epithelium it covers the body surfaces
and lines cavities and lumen and formed glands. There are:
a) Surface epithelium
b) Glandular
c) Special epithelium
2. Connective tissue, which surrounds or underlies and
support the other three basic tissues.
It is classified into:
a) Connective tissue proper
1- loose C.T
2- Dens C.T "regular, irregular"
b) Haemopoitic tissue
c) Blood and lymph
d) Supportive tissue" cartilage, bone"
3- Muscular tissue is made of contractile cells. responsible
for body movement" smooth, skeletal, cardiac"
4- Nervous tissue transmits and integrates information
From outside and inside the body to control its
activities and function.
Epithelial tissues
 The epithelial tissues having diverse functions and structural
multiformity
General features of the epithelia
The cells that make up the epithelium tissues have three principal
Characteristics:
a) They adhere to one another by mean of junctions
b) They exhibit functionally distinct surfaces, free or apical,
lateral and basal surface.
c) The basal surface is attached to the underlying basement
Membrane. EM = basal lamina
Function:
1. Act as selective barrier.
2. Facilitate differentiation and proliferation.
3. Provide attachment to underlying tissue.
 The epithelia are generally avascular, they don’t posses
blood vessels.
Nourishment occurs by diffusion.
 Epithelial tissues lined all surfaces and cavities of the body
except joint. e.g. : - Lined skin (epidermis)
- Lines digestive system, respiratory, urinary passages
- Lines closed coelomic cavities, peritoneum, pleura,
Pericardial called mesothelium
- Lines cardiovascular channels by endothelium.
- Lines all derivatives of surface epithelium such as
glands.
 All the body surfaces are active i.e. there is continuos flow of
materials either in unidirectional or bi-directional across the
epithelial lining.
 Glands of the body exocrine gland retained its connection
with surface, but endocrine lost it.
 Epithelia have a remarkable capability of renewal and
regeneration
This shedding off epithelium used in diagnostic aspect (Pap
smear)
Exofoliative Cytology to study the cervix to detect any cervical
carcinoma.
 The epithelial tissues have ability to change their
morphology and function. Change of one epithelium to
another is called metaplasia e.g urinary stone in U.B
(transitional
squamous cell)
Pseudo stratification of bronchi of smokers’
be reversal Tumor arising from epithelium
gland
str. sq. may
carcinoma for
adenocarcinoma
 They have diversity of function include: Protection,
lubrication, secretion, absorption, digestion, transport,
excretion, sensation, reception, transduction and
reproduction.
 Give examples of different secretion secreted by epithelial
gland??
Milk – breast
Sweat gland
Sebaceous
sweat
sebum
Gland in the external ear
wax
Digestive gland
enzymes
Endocrine gland
hormones
Urine, reproductive cells
Classification of epithelium
There are three types of epithelium
I- Surface epithelium (SE)
According to the cell number and the height and shape of
surface layer,
SE divides into:
a. Simple
b. Stratified
II - Glandular epithelium
a. Endocrine gland.
b. Exocrine gland.
c. Mixed.
111- Neuro-epithelium = special epithelia have certain special
properties
Concern with:
 Sensory perception
 Reproduction
1- Sensory perception
o Olfactory
o Visual
o Gastatory
o Auditory
2- Reproduction
germinal epithelium lined seminefrous tubules of the
testis and surface of the ovary.
I- Surface epithelium
a-Simple
b- Stratified
There are 4 simple and 4 stratified.
a. Simple
Consists of single layer of cells it can be classified as follow:
1. Simple squamous epithelium: allow exchange of gas, fluid
on metabolites.
The cells are flat with flattened nuclei.
Site:
 Endothelium of blood vessels
 Serous membrane, pleura, pericardium, peritoneal
(mesothelium).
 Alveoli of the lung. Small bronchioles
 Cardiac channels ( endothelium)
 Bowman's capsule (parietal layer )
 Thin segment of loop of Henle
 Inner aspect of tympanic membrane
2. Simple cuboidal (cubical) epithelium
It is formed of one layer of cubical cells with central rounded
Nuclei resting on a basement membrane.
Function:
1- Play important role in secretion or absorption.
2- Line glandular ducts
Site:
 Kidney tubules, proximal & distal convoluted tubules
and small collecting ducts
 Rete testis and free surface of the ovary
 Ducts of many gland.
3. Simple columnar epithelium
It is formed of tall columnar cells with basal oval nuclei
Function:
- It is primarily responsible for secretion and absorption.
Site:
 Line ducts of many glands e.g. stomach, intestine
(absorption),
gall bladder.
 Lining the large collecting tubules of the kidney ( secretion)
 Oviduct (secretion).
Note
There is type of simple columnar epithelium which have cilia
or its free surface (free border) called: simple columnar
ciliated epithelium.
Site:
 Oviduct (half non ciliated + half ciliated) (fallopian tube).
 Central canal of the spinal cord.
 Bony part of the Eustachian tube. Some bronchi of the lungs.
4. Pseudo stratified columnar epithelium
Two types:
1- Ciliated.
2- Non ciliated
It is formed of one layer of columnar cell resting all on the
basement membrane but not all the cells reach the surface. The
nuclei are stratified,
being at two or more levels.
Function
Secretion, absorption and ciliated concern with transport of
particles + protection.
Site
 Pseudo stratified columnar epithelium ciliated with goblet
cells
Found in: - upper respiratory tracts
- Lacrimal sac
- Cartilaginous part of the eustacian tube.
 Pseudo stratified columnar non ciliated
male urethra, vas deferens.
 Pseudo stratified columnar epithelium with steriocilia
actually
(Long microvilli a) epididymis and ducts deferens.
Stratified Epithelium
 It is formed of multilayered cells 2 or more
 The basal cells resting on the basement membrane.
 Derives its name from the shape or appearance of the
upper cells.
 Basement membrane usually clear & wavy.
Types
1- Stratified squamous.
2- Stratified cuboidal.
3- Stratified columnar
4- Transitional.
1- Stratified squamous epithelium
Two types of st. Sq. Epithelium:
a. Non- Keratinized (Mucous type)
The surface cells are flattened, variable and contain nuclei
but no keratin on the free surface.
Function
Site





Protective
Tongue, gum, palatine tonsil.
esophagus = oropharynx
Cornea& conjunctiva.
Urethra.
Vagina
b. Keratinized squamous epithelium
The surface cells are flattened, dead and non-nucleated
(anucleated) and formed superficial layer of keratin.
Function
Protective and adapted to physical insults as abrasion and
desiccation.
Site
 Epidermis of the skin
 Gingiva and part of hard palate may be keratinized due to
type of
Diet (abrasive) or technique of oral hygiene
 Annus, external surface of nose, ear, lip.
Keratinized
Stratified Epithelium
Non-Keratinized
2- Stratified cuboidal Epithelium
 The surface cells are cuboidal in shape
 They are limited in location
Site
 Ducts of gland with large caliber
 Granulosa cells of the ovarian follicle
3- Stratified columnar Epithelium
 The surface cells are columnar in shape.
 In between cells between the basal layer & surface layer
having different shape varies between polyhedral and
cuboidal cells.
Site





Male urethra
Large glandular ducts.
Rectoannal junction
Fornices of conjunctiva
Parts of pharynx & larynx
NB = Ciliated type present in fetal esophagus
4- Transitional epithelium
 It is intermediate between stratified squamous and
stratified columnar, it is resemble st. cuboidal epithelium
but having a unique flexible intensity i.e. it has ability to
distend and retract.
 The surface cells having dome- shaped appearance,
occasionally binuclear cells present. (Low cuboidal).
 Basal cells are highly cuboidal in shape.
 In non-distended urinary-bladder, it is four- six or more
cell layers thick.
 In distended (stretched) condition, an epithelium of only
two or three cell layers may be present
Function
1- Act as exosmotic barrier to prevent diffusion of water
in to the lumen of the urinary bladder.
2- Secretion & protection
Site
 Lining some portion of urinary tract.
Renal pelvis,
ureter, urinary bladder and proximal (initial part of the
urethra)
NB = Basement membrane not clear +not wavy.
11 - Glandular Epithelium
 Gland is specialized to produce secretion. Gland is formed of
group of cells.
 Gland can be divided either on the basis of mode of
secretion or according to the type of secretion:
According to mode of secretion:
1- Exocrine: (release secretion to duct system)
2- Endocrine: (release secretion to bloodstream)
3- Mixed: pancreas, testis & ovary
Exocrine glands
It would be classified into four categories according to:
1. The number of the cells:
a. Unicellular gland = goblet cells
(RT+ D.S)
secret mucous
b. Multicellular = formed of many cells - salivary glands
1- Epithelial sheet
2- Intraepithelial glands
3- Complex with duct
2. According to the nature of the secretion
a. Mucus = glycoprotein mucin = mucin & water = mucus
The secretory cell have basal flattened situated nucleus
pushed down by the large quantity of mucino granules.
Function
Protection + lubrication
b. Serous
 Secret clear, watery fluid rich in proteinaceous
substances.
 Secretory cell has large basal (not flattened) with
rounded
Nucleus & perinuclear cytoplasmic basophilia (rER)
Function
Lubrication cleans epithelium surface & rich in enzymes.
c. Mixed or mucoserous = seromucous glands:
Contains both cells or units or mixed units.
Mucous units attach to it serous caps (demilunes).
d. Watery secretion
e. Waxy secretion
(cerminous)
Sweat
gland of the external ear
3. According to the mode of the secretion
I.e. changing occurring to the secretory cells
1- Merocrine: no cellular change - secretion released through
the cell membrane (exocytosis, salivary gland, pancrease
(releas mucous).
2- Apocrine: the apical part of the secretory cells (part of cell
membrane & parts of cytoplasm) release with the secretion
e. g mammary gland, apocrine sweat gland, cerminous gland.
3- Holocrine: the secretory cells shed off with the secretory
Product into the glandular duct e.g. sebaceous gland.
Ovary & testis is a special type of holocrine - in that whole living
cells (spermatozo & oocyte) release so called cytogenous
secretion.
4. According to the shape of duct system and secretory portion
1- Tubular (secretory part)
On the bases of duct system:
i. Simple tubular e.g. crypts of liberkuhn (intestinal gland).
ii. Simple coiled tubular e.g. ecrine sweat gland.
iii. Simple branched tubular e.g. fundic gland of stomach,
Burner's gland of the duodenum.
iv. Compound tubular = cardiac gland of stomach.
2- Alveolar (acinar)
a. Simple alveolar:
e.g. may not occur in mammals poison amphibians
b. Simple branched alveolar
e.g. sebaceous
3- Tubuloalveolar (mixed)
a. Compound tubuloalveolar gland. e.g salivary gland &
pancrease
Myoepithelial cells = basal cell = basket cells
In certain gland such as sweat, salivary, mammary ceruminous,
lacrimal)
There are special cells called myoepithelial cells.
Site
Basal portion of secretory acinus cells.
Features
Muscle like cells, contractile, contain myofibrils, ectodermal in
Origin, having cytoplasmic proceses, aid to squeez the
secretion to the glandular ducts.
Neuroepithelium
Acts as sensory receptors for special stimuli epithelium concerned
With
sensory perception
Olfactory
Auditory
Taste (taste bud)
Visual
crista ampuli
Organof corti
Reproduction
(Germinal epithelium)
1) Junctional complex (usually near the apices)
Appear in LM as a darkened area called terminal bass.
a. Zonula occludens = tight junctions
 Near apices of epith. Cells - e.g. endothelial cells
 Two cell membrane are in actual contact no intracellular
space.
 Act as barrier prevent the movement of substance into
the
intercellular spaces, supportive.
 Actualy appear as spot i.e focal fusion not as continuous
seal.
 Cell membrane of a cell
pentalaminar
(impermeable)
b. Zonula adherence
Intercellular space = 10 - 15nm
 Thickness of2 membrane (mainly due to actin).
 Also encircle the cells like a built like.
 Cytosheet of both cell linked by transmembrane linker
Fascia adherans similar to zonula but doesn’t go around the
entire
Circumference of the cell (ribbon like)
c. Desmosomes = macula adherense
 Disk shape attachment plaque, attach to it intermediate
filaments
 The intercellular space - 30 nm and contain filamentous
material with a dense, vertical line from which filamentous
material attach to it.
(An 10 antibodies against desmosome) peimphigus ulgaris wide
spread
Blistering
loose of tissue fluid
un recoverable
death.
2) Gap Junction = macula (communicats) - permit
movement of ions
 2 cell membrane are not in actual contact as in
zonula occludens
 2 cell membrane line close together, the gap being
reduce from normal to us to 2 - 3 nm..
 In between there is bead-like structures arranged in
hexogens.
 A minute canaliculus passing through each head
connects the cytoplasm of the two cells this allow
passage of substance from one cell to another.
 Involve in cell - cell communication - and low
resistance to ionic flow
3) Terminal web
 Area just underneath the apical surface
 Contain a dense accumulation of filaments run
parallel to surface.
 Devoid of cell organelles.
 Give support to apical surface and produce a
root for apical appendages.
(Fig. of desmosomes: General hist. for medical students (Dr. smar alsagaf, Dr. Mohd
Badawoud)