Histology
(MLHS-201)
Lecture 4
Tissue types
(Epithelial tissue)
Dr. Afaf Mousaad
• Department of Medical Laboratory Technology
• Faculty of Allied Medical Sciences
1
Learning objectives
• How to Identify the keratinized, basal and
apical layers in stratified epithelium.
• Distinguish between simple and stratified.
• Describe the shapes of stratified epithelial
cells.
2
All epithelial cells are in contact with the basement
membrane, but not all of them reach the surface of the
epithelium. The nuclei are often located at different
heights give the epithelium a stratified appearance.
Ciliated e.g. epithelium of respiratory tract (Nasal
cavity ,larynx, trachea, bronchi,....)
3
4
5
Stratified epithelium
a.keratinized stratified epithelium:
The mammalian skin epidermis (cornified epithelium) :
-A protective type of epithelium
containing a tough, resistant keratin
protein . Protects underlying tissues from, dehydration,
chemicals, and bacterial invasion.
6
The outermost layers of cells are flattened squamous, filled
with Keratin.
-protects delicate tissues in areas
subjected to abrasion.
The thickness of the cornified layer of the skin varies greatly,
being thickest on the soles and palms.
7
Keratinized stratified
squamous epithelium
e.g epidermis of the
skin
8
This type of stratified epithelium is constantly renewing itself.
Cells in the bottom layer divide, and the daughter cells move
towards surface maturing and then degenerating.
There are around 8-10 layers of cells.
The cells become more flattened towards the top (apical) layer
and have flattened nuclei - these cells are dying.
9
Horny cells are constantly shed
from this part of the stratum
corneum.
Variations in the thickness of the
epidermis are mainly the result
of variations in the thickness of
the stratum corneum(~0.1 mm
in thin skin and 1 mm or more
in thick skin).
10
The stratum spinosum:
cells
become
The
irregularly
polygonal. The cells have
spine-like
cytoplasmatic
extensions (hence the name
of the layer and of its cells:
spinous
cells),
which
interconnect the cells of this
layer.
11
Elongated keratinized structures derived from
invaginations of epidermal epithelium.
12
Horny hard plates made up of
cornified cells containing keratin.
Nail plate is divided into:
1-The body of the nail :
Broad pink part, appears pink because it is semi-
transparent (blood capillaries in the dermis shows through).
It shows a crescent-shaped area, Lunula best seen on the thumb and absent
from the little fingers
2- The root of the nail:It lies beneath the skin (invisible part). Nails grow
at a rate of 0.5 mm/week. A finger nail grows faster than toe nail
13
b.Non keratinized type: the
most common stratified type
consists of many layers of
closely held cells with the
outermost layer consisting of
flattened cells . e.g. covers
the tongue and lines the
mouth
cavity,
throat,
esophagus, anus, & vagina.
- non-keratinized, mucousal cell layer
lining the esophagus
- protection of the esophagus from
stomach acid,
14
Stratified squamous
epithelium.There are 1020 layers of cells present,
which by definition makes
this a "stratified"
epithelium; and that the
cells at the free surface are
flattened, squamous
shaped ones.The cells in
the deeper layers are
cuboidal.
The lumen of the esophagus is
lined with stratified squamous
epithelium.
15
Rare-found in ducts of
e.g.
Sweat glands which are coiled
tubular glands.
Their ducts consisting of
two layers of small cuboidal
cells
16
Stratified cuboidal epithelium is a rare type
of epithelial tissue
cube-shaped
commonly cells make up two layers
sweat glands in the skin
mammary gland in the breast
salivary glands in the mouth
Stratified cuboidal epithelium : the
ducts of the parotid gland
composed of cuboidal shaped cells arranged
in multiple layers.
17
Transitional epithelium:
e.g. Urinary bladder ,
ureter, urethra .
Control the amount of
water and salts that are
absorbed back into the
blood and what is taken
out as waste.
18
Transitional epithelium
•Multilayered
•Surface cells varying in shape
from round to flat if stretched
•Lines hollow organs of the urinary
tract that expand
19
20
3.Transitional epithelium is a stratified epithelium in which the shape of
the surface cells changes (undergoes transitions) depending on the degree
of stretch.
Empty:Unstretched cells :rounded
superficial cells bulge out
1.When a transitional epithelium is not stretched (in an empty bladder)
the cells of the surface layers are large and rounded.
2.When a transitional epithelium is stretched (in a full bladder) the cells of
the surface layers are pulled into a flatter shape.
21
"transitional“ = ability to change its shape from
cuboidal to squamous when stretched.
e.g. Urinary bladder , ureter, urethra.
Empty bladder, consists of 4 -8
layer of cells .
When the bladder is distended with
urine the cells at the top become flat ,
the number of layers is reduced to 2 3 glide on each other.
22
a. distended urinary bladder
(full
with
urine).
The
epithelium is very thin with
fewer layers of cells and the
top layer become flattened.
The cells of the intermediate
Transitional
layers glide on each others. depends
and reduced to 2 or 3 layers .
epith.
thickness
on the state of distension
(full) or contracted (empty).
23
b. Empty urinary bladder-
the epithelium consists of
more than five layers of
cuboidal cells.The surface
cells facing the lumen of
the
bladder
are
dome-
shaped which characterizes
on the apical surface the
transitional epithelium.
on the apical surface
24
Neuroepithelial Cells
The tongue is a muscular organ covered with mucosa. Tiny
bumps called papillae give the tongue its rough texture.
Thousands of taste buds cover the surfaces of the papillae.
Taste buds contain neuroepithelial cells
embedded in the stratified squamous
epithelium of each papilla that are
the receptors for taste.
25
We all have about 10,000 taste buds, mainly on the tongue.
Most highly concentrated in certain regions of the
tongue's surface.
Sweet receptors on the tip of the tongue .
Sour receptors occur along the sides of the tongue .
Salt receptors most common in the tip and upper front portion
of the tongue.
Bitter receptors :located toward the back of the tongue.
26
Receptor cells live for only 1 to
2 weeks and then replaced by
new receptor cells.
Each receptor responds to one
of the basic tastes.
The four common tastes are
sweet, sour, bitter, and salty.
27
Questions
1.Keratinization is a characteristic of the cells in the epidermis of the skin.
2.What type of epithelium has dome shaped cells on the apical surface?
a. Epithelioid tissue
b. Mesothelium
c. Endothelium
d. Transitional
e. Pseudostratified
3.Keratinized stratified squamous epithelium forms the epidermis.
28
‫‪Assignments‬‬
‫األسم‬
‫م‬
‫‪I.D‬‬
‫‪1‬‬
‫‪51012018‬‬
‫اسالم عادل رمضان ابراهيم على‬
‫‪2‬‬
‫‪51012019‬‬
‫اسالم محمد عبد السالم محمد‬
‫‪3‬‬
‫‪51012020‬‬
‫اسماء إبراهيم كمال بسيوني‬
‫‪4‬‬
‫‪51012021‬‬
‫اسماء النقراشي وادي احمد‬
‫‪5‬‬
‫‪51012022‬‬
‫الشيماء مصطفى عبد العاطي‬
‫‪6‬‬
‫‪51012023‬‬
‫امل محمد احمد احمد سويدان‬
‫‪7‬‬
‫‪51012024‬‬
‫اميرة اسعد يوسف االسكندراني‬
‫‪8‬‬
‫‪51012025‬‬
‫أميرة صالح مرشدي عبد السالم‬
‫‪1‬‬
‫‪51012109‬‬
‫محمد احمد فتوح احمد سعده‬
‫‪2‬‬
‫‪51012110‬‬
‫محمد احمد محمد قاقا‬
‫‪3‬‬
‫‪51012111‬‬
‫محمد انور عبد الغنى السيد هالل‬
‫‪4‬‬
‫‪51012112‬‬
‫محمد خالد اسماعيل عبد العال‬
‫‪5‬‬
‫‪51012113‬‬
‫محمد صالح السيد صابر سعيد‬
‫‪6‬‬
‫‪51012114‬‬
‫محمد صالح الدين جامع فتح الباب‬
‫‪7‬‬
‫‪51012115‬‬
‫محمد عادل خضر إبراهيم‬
‫‪8‬‬
‫‪51012116‬‬
‫محمد علي رمضان علي النقيب‬
‫‪Assignment tittles‬‬
‫‪Nucleus‬‬
‫‪Smoking & Lung cancer‬‬
‫‪3/23/2016‬‬