4th lecture
In this sheet we will talk about many issues But we must read the book because the Dr
said is all the" epithelium chapter " wanted    ( L2no 6olab el Dof3a gnano ahlo  )
# we will talk about two main things : 1) notes about types of epithelium and the rest
mush be read from book 2) notes about specializations of the apical cell surface and the
rest must be read from book 3) notes about intercellular adhesion and other junctions
and the rest must be read from book 4) notes from lab 2 ( classifications of epithelium )
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# The menstrual cycle is 28 days ( this period is between two cycles ) therefore >>> in
the fourteen day we get ovum >>>> if the fertilization takes place (presence of sperm )
>>> we will get the Zygote  >>> after many steps of dividing of this zygote >>>>> in the
2nd week of the pregnancy , the female will know her pregnancy because the menstrual
cycle did not come  >>>
# The embryo consists of two layers ( Hypoblast and epi-blast )
# In the 3rd week , the heart will form in the embryo .
# In the 3rd week , the Gastrulation process takes place ( and in this process , the embryo
will consist of 3 layers : ectoderm , endoderm and mesoderm )
# The Gastrulation : is a phase early in the embryonic development of most animals
during which the single –layered blastula is recognized into a tri-laminar ( three layers )
structure known as the gastrula >>> " these three layers are known as : ectoderm –
endoderm – mesoderm "
# Tissue barrier
this subject includes two examples ( Blood air barrier in lungs – Blood brain barrier in
brain (BBB) )
- it is discovered when the scientists injected th e Chlorophyll in different parts of the
body >>> all these parts ( tissues ) became green color except the testis >>>> means in
the testis tissues there are barrier which prevents the pass of Chlorophyll >>>> the testis
stayed as them  >>>> But with increasing the concentrate of the Chlorophyll >>> the
testis became green color ( But the increasing of this substance forms a risk because the
chlorophyll and any chemical substance is considered risky especially in high
concentrations 
# The blood – brain barrier ( BBB )
- is a highly selective permeability barrier that separates the circulating blood from brain
extracellular fluid (BECF) in the central nervous system (CNS )
- it is formed by capillary endothelial cells , which are connected by tight junction .
- it allows the passage of water , some gases and lipid soluble molecules by passive
diffusion and these endothelial cells restrict the diffusion of microscopic objects such as
bacteria   
# This structure is very important 
# (From Dr Darwish) (so2al 3la inferad :p ) >>> The basement membrane consists of
two layers :
1) Basal lamina ( lamina lucida and lamina densa )
2) Lamina reticularis ( collagen type 3 with carbohydrate )
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# CONCENTRATE OK !
-If we look to the cell through the microscope we may recognize the epithelial layer But
we cannot know its resource >>>>> BUT when we put this layer ( basal lamina ,especially
Lamina densa ) in the medium >>>> the epithelial cells of this layer will change their
direction and line above the basal lamina like ranks of army ( here the command of the
lineup came from the basal lamina ) >>>>>>therefore we can know the type of the tissue

and >>>>> the cells after this lineup will regulate their metabolic activity ( means : forexample they will use 10 mg glucose instead of 10 g per day  ) >>>> the cells after
lineup will regulate the mitotic activity BECAUSE  when they lined , the lateral and basal
and apical domains are identified  means the polarity formed  this polarity will affect
on their mitotic activity  .
# Some cells start to grow in the abnormal way above the basal lamina horizontally first
then vertically >>> and this grow pushes the basal lamina down and the pushing proceeds
by the growth of more cells till the basal lamina be broken then they penetrate it and
they will be spread all over the body >>>> we will get ( metastasis that means the spread
of cancer from one organ or part of organ to another organ or another part of organ such
as breast cancer    ) >>>> the aim of their penetration of the basal lamina is : to
access to the blood supply in the C.T ( e3ni 3`r9`hm sharif el gama3a    bdhom eaklo
wa etgzooooo    ) :p
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# Remember : the epithelia cells are amorphous means : NO 3-D structure , NO cells
fibers and this is noticed first in trachea  .
# The epithelia are responsible of the trans-cellular transport  the passing of
substances from one side to another side 
# Note : the most of the tumors after the age 45 are related to epithelial origin like the
breast cancer and prostate cancer BUT notice that the cancers and tumors that
developed from epithelial origins are less risky than those developed from C.T .
# Remember : the tasting buds and olfactory epithelium are examples of modified
epithelium
# Note : any epithelium must be connected to connective tissue proper ( connective tissue
proper means : is a subset of C.T characterized as having more intercellular materials than
cells  )
# Ulcer is the discontinuity of an epithelium or the loss of it and this is the main cause of
venous ulcer .
# Venous ulcers : are wounds that are thought to occur due to improper functioning of
venous valves >>>> usually in the leg  hence are called ( leg-ulcers ) .
# Remember : the type of an epithelium tissue present in a cell depends on its function 
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The classification of epithelium
Epithelia can be divided into two main groups :
1) covering (lining) epithelia
2) Secretory ( glandular ) epithelia
 But this is arbitrary division ( maybe incorrect ) , because there are lining epithelia in
which all cells also secrete (e.g :the lining of the stomach ) or in which glandular cells are
distributed among the lining cells (e.g : mucous cells in the small intestine or in trachea )
# Remember : The C.T that underlies the epithelia lining the organs of the digestive ,
respiratory and the urinary systems is called (Lamina propria ) , the area of the contact
between the epithelium and C.T may be increased by irregularities at the interface in the
form of small evaginations called (Papillae ) , papillae occur most frequently in epithelial
tissues subject to friction , such as the covering of the skin or tongue 
# The shapes and dimensions of epithelial cells are quite variable , ranging from columnar
to cuboidal to low squamous cells .
# The cells size and morphology are generally dictated by their function .
# Epithelial cell nuclei vary in shape and may be elliptic ( oval) , spherical or flattened .
# Nuclear shape corresponds roughly to cell shape :  tall cells have elongated nuclei
squamous cells have flattened nuclei  Cuboidal or pyramidal cells have more
spherical nuclei .
# Note : The number and shape of the stained nuclei can indicate cell density – shape –
number of cell layers in an epithelium – primary morphologic criterion for classifying 
‫ال داعي لذكر جميع معلومات الكتاب بخصوص موضوع أنواع النسيج الطالئي والصور المدرجة عليه فجميعها‬
‫مطلوبة بالحرف كما قال الدكتور والنقل من الكتاب لهذا الملخص سيعتبر ُجهدا ً ضائع ألنها مطلوبة رغم أنّها لم تُذكر‬
‫كلّها في المحاضرة ( بس حسبي هللا ونعم الوكيل بالطالب يلي جننّوا للدكتور بالمحاضرة لحتى حكالهم انو الشابتر‬
)    ‫مطلوب من الجلدة للجلدة‬
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# Differentiated cells cannot go for divisions and if they are cancer they will never
response to the chemical and radio therapy BUT by surgery 
# There are some keratinized tissues in the mouth oral cavity ( only note  )
The basolateral domain
Note : The continuous zones around epithelial cells prevent membrane proteins at the
apical cell surface from moving in the membrane to the basal and lateral surfaces and vice
versa .
 This produces two membrane domains (apical – basolateral ) with different protein
populations , which allows the two sides of the epithelium to maintain different receptors
and to function differently .
# Apical cell membranes of epithelia are part of luminal compartment of a tissue of organ
, while the basolateral domains of the epithelial cells are part of the basal compartment
that also encompasses the underlying connective tissue 
# Notice that the apical membrane of a polarized cell is the surface of the plasma
membrane that faces inward to the lumen  this is particularly evident in epithelial and
endothelial cells 
# The basolateral membrane of polarized cells is the surface of the plasma membrane that
forms its basal and lateral surfaces  it faces outwards ( toward the C.T ) and away from
the lumen 
# Note : the thick area on the apex of adjacent cells is the terminal bars which includes
tight and adherents , this area was thought to be junctions itself  But lately it was
discovered that it has some modified structures by E.M  .
# On the apical parts of the cells there are modified structures including (tight and
adherent junctions ) .
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The intercellular adhesion and other junctions
Tight Junctions ( occluding junctions or zonulae occludens)
# The word zonulae means a band encircling each cells as a belt on the waist
* The word occluding means that the transcellular transport is occurring through the cells
themselves (transcellular path) not between them (paracellular path).
* Tight junctions are the most apical of the junctions
* Under the microscope the adjacent membranes of these appear fused
* The seal between these is due to the interactions between the trans-membrane claudin
and occluding proteins, they join the cells together , and it's kind impossible to separate
two cells from their sides and if they are separated occluding will not divide into two parts
but it will go with one of the cells .
# Major functions : seals adjacent cells to one another , controlling passage of molecules
between them , separates apical and basolateral membrane domains .
# Cytoskeletal components : actin filaments 
# Major trans-membrane proteins : Occludins , Claudins and ZO proteins 
( WE SHOULD READ THIS SUBJECT FROM BOOK Because el doctor 7aka heek ) e2brni el
doctor ana <3 <3 <3
Adhering junctions( Zonula adherens )
# they are close to each other but not fused and the spaces are filled by some proteins
called adherenes .
** In the zonulae area of adhering junctions, the plasma becomes thick and straight .
** Cadherene/adherene : Is a glycoprotein that mediates the cell adhesion it's called
CAdherene because it's a calcium dependent means it works in the presence of Ca+2
** In centrifuge if we have a high speed to separate the cells they won't be separated
until the calcium is removed  ( allah be3en sho bdna n3ml :p )
** Actin filaments are present in these junctions
** Cadheren binds to Catenin that's linked to actin filaments by some certain proteins.
The actin filaments linked to the adherents junction to form a part of the terminal web.

** The terminal web : a network of actin and other things which is supported by myosin

** A related adherent junction is the Desmosomes (macula adherens) they
don't form a belt around the cell ,they have larger members of cadherens family called
desmoglein and desmocollin -they look like spines under the microscope
# The cytoskeletal components of Zonula adherens are actin filaments BUT in
Desmosomes are intermediate filaments (keratin ) 
# The major functions of Zonula adherens are : providing points linking the cytoskeletons
of adjacent cells , strengthening and stabilizing nearby tight junctions 
# The major functions of Desmosomes are : providing points of strong intermediate
filament coupling between adjacent cells – strengthening the tissue 
# # Note:
Sometimes the body forms some antibodies against desmoglin which is in the
desmosomes  these antibodies participate in separating the cells and this allows the
fluids of the body (plasma) to accumulate  so the accumulations appears as bubbles on
the skin and they are called blisters - they can burst those people who have this disease
(bullous or blistering disease) they have a lack of blood supply and they may get a stroke…
( eni ema be9ebhom gl6a aw anfjro :p Bae5a hahahah)  l2 gd (be9ebhom gl6a wa
bemoto    ).
#
Hemidesmosome  it's half a desmosome, consists of one cell and we say half
because desmosomes must contain 2 cells  by the way hemidesmosomes are
responsible about binding the basal surface of the epithelial cells to the basal lamina .
#The cytokeratin:
A protein present in desmosomes , it forms a bundle called to ton fibers , if cytokeratins
fail to make these bundles or fail to be inserted into desmosomes , the epithelium will
NEVER be keratinized
 cytokeratin is either basic with eight subtypes or acidic ten/eleven subtypes
 Myoepihelial cells contain cytokeratin   
 Any epithelial cell should contain at least<<< 1>>> basic and <<<1>>> acidic type, and
the more the tissue is complicated the more the number of cytokerateins  it's existence
in the cell means it's epithelial   
Note:
## Cancer cells have no gap junction they don't communicate and they divide not
uniformly
## they are for communication rather than adhesion .
 ‫ وقراءة أغلب الصفحات الباقي أيضا طبقا ً لكالم الدكتور‬, ‫ ) من الكتاب‬Gap junction ( ‫ يجب قراءة ال‬: ‫مالحظة‬
# Specialization of some apical cell surfaces
# The apical ends of many tall or cuboidal epithelial cells face an organs lumen and often
have specialized projecting structures .
These function either to increase the apical surface area for absorption or to move
substances along the epithelial surface .
1) Microvilli
## They increase the surface area about 20-40 time 
## All epithelial cells have microvilli but their number varies due to their needs and the
cell function
## When their number is few they act for the cell stability 
## Microvilli are covered by glycocalyx covering intestinal microvili , it includes enzymes
for digestion of certain macromolecules the existence of glycocalyx indicates why
microvilli give PAS positive stain((((they have carbohydrates)))) .
## The arrangement of brush border microvilli is in the kidney 
## there are 25-30 actin and they are joined by a protein called Fembrin , then they are
inserted in the apical part as a part of the terminal web .
# Note  normally microvilli are a bit apart  so the contraction of actin filaments
helps in their motility
2) Steriocilia
# are restricted to absorptive epithelial cells lining the epididymis and the proximal part
of ducts deferens in the male reproductive system
# They increase the cells surface area , facilitating absorption
# More specialized stereocilia with a motion-detecting function are important
components of inner ear sensory cells .
# The resemble microvilli in containing arrays of actin filaments and various actin-binding
proteins , with similar diameters and with similar connections to the cells terminal web .
# Sterecilia are much longer and much less motile than microvili , anf may show distal
branching along their length .
# But keep in mind that  they are not motile and they are in the epididymis and ear
sensory cells  Also they are longer than cilia 
3) Cilia
# there are around 300-400 cilia in each cell of the respiratory tract.
# they are larger than microvilli 0.2 in diameter and 7-10 Mm long
# MOTILE cilia are only found in epithelia and they are abundant in the apical domain of
cuboidal or columnar
## They have microtubule triplet , a 9+2 assembly which is called axoneme
## In fallopian tube some cells are ciliated and so are not the one who are not serves as
lubricators of the other ciliated cells
## Dynein is important for the cilia movement with the help of ATP
## the absence of Dynein creates an immotile cilia and this disease is called immotile cilia
syndrome 
## If the cilia in the respiratory tract stop moving all the strange bodies are going to
enter the lungs and this too bad for the health   
# Note : that Nicotine limits the cilia movement and the goblets of the cell starts to
secretes more mucus and this helps the strange bodies to be sticky to this mucus and this
is dangerous too
# Note : absence of cilia causes infertility   
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 ‫الحمدُ هلل الذي بنعمته تتّم الصالحات‬