Histology
Team
Lecture 3
Clinical Pharmacy
Cairo University
/Clinical2020CU
2014/2015
Lecture II: Connective Tissue
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Remember: There are four types of tissues:
1) Epithelial Tissue - Done
2) Connective tissue – Focus up now!
3) Nervous tissue
4) Muscular tissue
 Some important points:
factories of making proteins ‫ هي ال‬Ribosomes ‫ال‬
basophilic ‫ يعني بتعمل بروتين بتخلي الوسط‬ribosomes ‫و قولنا ان الخلية طالما فيها‬
‫في‬Golgi apparatus ‫ و بعدين تروح ال‬rER ‫ اللي بتتعمل في ال‬enzymes ‫و القصة بتاعت ال‬
‫ اللي لو كان ليها شكل معين ممكن تعمل‬secretory vesicles ‫و هو يطلعها على هيئة‬transport vesicles
exocytosis ‫ و تخرج بال‬membrane ‫ و في االخر تقرب من ال‬secondary lysosomes ‫ او‬primary
‫بعد ما تعمل وظيفتها‬
‫ بتاع خلية بمجرد اني‬EM ‫و ال‬LM ‫و شكل ال‬organelles ‫انا عايز اوصل من كل دة الية ؟؟؟ اننا اقدر احدد ال‬
‫اعرف وظيفتها‬
Digestive cells should have many lysosomes and developed Golgi apparatus ‫يعني مثال‬
‫ فكل دة هيكون موجود و‬proteins ‫ اللي بتعمل‬ribosomes ‫ اللي بيعمل ال‬RNA ‫ بتعمل ال‬Nucleolus ‫و ال‬
‫واضح في الخلية اللي بتعمل بروتين‬
heterochromatin ‫ بيبقى كتير في الخلية اللي بتعمل بروتين و العكس بالنسبة لل‬euchromatin ‫و ال‬
II.
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Connective tissue:
a. Structure: Consists of widely separated cells with excess matrix (intercellular
ground substance)
b. Site:
underneath epithelium
c. Origin
Mesodermal only in origin
d. Main characteristics
i. Usually contain blood vessels , nerves and
lymphatics
e. Function
Connects, supports and protects organs
f. Classification
According to matrix:
a. Blood: contains fluid matrix
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b. Connective tissue proper: contains soft matrix
c. Cartilage: has rubbery matrix.
d. Bone: contains hard matrix
Having the proper connective tissue topic under study, we are gonna see the different subtypes
of it according to the number of layers:
Proper connective tissue
these tissues consist of cells with fibers found in matrix
1- Connective tissue cells: either fixed or free
2- Connective tissue fibers: either collagen or elastic fibers or reticular fibers
3- Connective tissue matrix:
connective tissue is classified into four types according to matrix consistency:
a. Soft matrix: proper C.T
b. Firm (rubbery): cartilage C.T
c. Hard (solid) bone C.T.
d. Fluid matrix blood C.T
1) Fixed Connective tissue cells:
Stable, long lived cells:
1) Undifferentiated Mesenchymal cell (UMC) : ‫بتتكاثر و تتحول لباقي الخاليا‬
 Called “mother cell or stem cell or (mesoderm).
 Site: Mainly in the embryo, in adult in certain areas e.g. bone marrow
(i.e. To be the non-stop source of blood cells).
 LM: small branched cell with pale basophilic cytoplasm and pale nucleus ( has
nucleolus )
 EM: few organelles, many free ribosomes, nuclear euchromatin
 Function :
i. Differentiate into other types of cells➡ in embryo. & acts as stem
(mother) cells.
ii. In adult → they still undifferentiated in certain areas to act as lifelong source for some cells as:
- in bone marrow ➡ blood cells
- around blood vessels ➡ pericytes.
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2) Pericytes:
 Origin : (UMCs)
 site: around blood capillaries
 Shape: is similar to that of the (UMCs) in L.M, but
in the E.M: it has many free ribosomes, few other organelles & (actin &
myosin filaments).
 Function: it acts as (UMCs) for the adult as during injury of the connective
tissue &blood vessels it can give rise to: -Fibroblast & smooth muscle cells &
endothelial cells
As it's also has a contractile function and can constrict blood vessels as it has filaments of actin
& myosin.
3) Fibroblast1:
 They are the most common CT cells ‫بتصنع النسيج‬
 Origin: UMCs & pericytes.
 LM: deep basophilic cytoplasm, pale large oval nucleus with prominent
nucleolus. (Vesicular)
 EM: branched cell with euchromatic nucleus (active nucleus), large
nucleolus, Many rER, Golgi apparatus and mitochondria " features of
protein -secreting cells . "
 Functions:
1. Formation of elastic and reticular fibers
2. Formation of matrix
3. Help CT healing.
Note: Old Inactive Fibroblasts are Called fibrocytes. They can Change to active Fibroblast in
wound healing.
4) Macrophage:
- It has two types have the same origin, structure & function.
They are: fixed ➡ which still in the connective tissue.
Free ➡ which are distributed over the organs.
 Origin (indirect transformation) : monocyte (white blood cells)2
 Site: in loose C.T along collagen fibers, Known as histiocytes .
1
2
Blast = forming so Fibroblast = fibril forming cells.
Gaya bardo mn el UMC
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 LM: large cell with pseudopodia. So it has a highly variable shape: dark
small kidney shaped nucleus (very characteristic to this type of cells) &
darkly stained, cytoplasm: pale & granular & rich in vacuoles.
Special stain: vital stain (which keep the cell alive after be stained) ➡ called: trypan blue.
 EM: many lysosomes and developed Golgi apparatus & phagocytosed
particles.
 Functions:
1. Phagocytosis and destruction of foreign bodies & microorganisms:
they can fuse and form giant cell to engulf large foreign bodies -clean wounds
2. It also acts as antigen presenting cells to T- lymphocytes.
(I.e.: bt3ml nafsaha ka2naha antigen)
3. Has a role in the destruction of old RBCs in liver & speleen (ya3ny
btksr el RBCs el adeemafel kabd w El to7aal w ta5od el
hemoglobin (el 7deed) Elly gowahom lel bone marrow tany).
5) Fat cells (adipocytes)
 Origin: UMCs
 it has two types:
Site
Site
L.M
unilocular fat cell
In white adipose C.T.
Large oval cell, with peripheral and flat
nucleus, its cytoplasm is a very thin film
around a single large fat droplet.
* In H& E stained section fat dissolves by heat
and the cell appear evacuated as large
vacuoles called (signet-ring appearance). But
in frozen sections fat stains orange with
Sudan III
E.M
few mitochondria & moderately electron
dense fat
Function Storage of fat to release energy & acts as
heat insulator.
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multilocular fat cell
In brown adipose C.T.
Small rounded cells, the nucleus is
central & rounded, cytoplasm has
many small fat droplets.
* pigmented by the cytochrome
pigments in the mitochondria.
Many mitochondria then as the
unilocular.
Heat generator especially in newly
born babies which regulate their
body temperature and give them
heat necessary for their lives.
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6) Reticular cells:
 Origin: UMCS
 Site: in stroma of different organs e.g. spleen, lymph, nodes.
 L.M: small branched cells with long thin processes with central rounded
nucleus &pale basophilic cytoplasm.
 Functions:
1. It forms a reticulum network with reticular fibers.
2. It acts as supporting cells.
3. Can act as phagocytic cells, on need.
B. Free Connective tissue cells:
motile, short - lived cells:
1) Plasma cell: ‫ بتصنع بروتين بس بيخرج برة الخلية على شكل‬antibodies
 Origin: developed from activated B-lymphocyte.
 Site: abundant in lymphoid tissues.
 LM: large oval cell, its nucleus is eccentric with a cart-wheel (clovk face)
appearance, with deep basophilic cytoplasm and –ve Golgi image.
** "features of protein secreting cell” well developed Golgi apparatus large amount of rER &
mitochondria.
 EM: no secretory granules, as they are secreted continuously.
 Function: formation & secretion of antibodies.
2) Mast cell:
 Origin: UMCs in bone marrow.
 Site: in loose C.T along blood vessels & in C.T under epithelium of
respiratory or digestive tracts.
 LM: oval cells with central rounded nucleus with many basophilic
granules in the cytoplasm
Special stain: granules can be stained.
Metachtomatically (means color change) : with toluidine blue (methylene blue) ➡ it gives
purple color instead of blue.
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EM: rich in mitochondria, Golgi apparatus and secretory vesicles
(granules). Cytoplasm is full of electron dense granules that mask other
contents
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Functions: secretion of:
o Histamine ( vasodilator ) which initiate allergic reaction
o Heparin ( anticongalnt ) ) (‫التالت المحاضرة الجاية( –مضاد للتجلط‬
inri eccserce seencelinpe ce cis .)FCE( esrsscnec et seencelinp risoecercnr terces -3 .
.)epsi sp eppssis3cs ys3se ( .encs et eppssis
Fibers
A) white collagen fibers: ( most common type).
▪Origin: Mainly Fibroblasts (+ chondroblasts & osteoblasts) .
▪L.M: wavy branching bundle formed of non- branching parallel fibers ( thin threads polymrized
to the shape of bundle f hatb2a shabah el tendon kda)
▪Color & stain: -colorless when single, white when condensed
- Pink in color in H&E (acidophillic).
▪character: strong, rigid& not elastic
▪function: give strength to tissues &resist stretching.
▪Types: many Types: the most important are ; I, II, III, IV, V, VI.
B) yellow elastic fibers: formed of protein called ➡elastin.
▪Origin: Fibroblasts.
▪l.M thin long branching Fibers, run singly not in
Bundle.
▪Color & stain:yellow in color when fresh., pink in H&E, brown with orcein.
▪ character: stretch &recoil (elastic) .
▪function: give elasticity to tissues & in the walls of the artries as Aorta (if we examen the wall
of the Aorta we notice that it's color is slightly yellow or yellow because it comtain large
quantities of yellow elastic fibers).
▪Types: only one type.
C) reticular fibers :
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▪Origin: Fibroblasts
▪l.M: very thin fibers that branch &anastomose forming a network
▪Color &stain: brown with silver stain (argyeophilic).
▪character :delicate & flexible.
▪function: form stroma (background) which supports organs.
▪Types: One type.
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Types of connective tissue
It was classified according to relative abundance of the basic components into:
I) LOOSE C.T. PROPER.
II)DENSE C.T PROPER.
Firstly we will start with:
I) loose C.T proper:
1. ➡ Loose (areolar) C.t: (the most common type) :
▪ structure: it contains:
_All types of C.T cells ( mainly Fibroblasts,fat cells & macrophages) & all types of C.T. Fibers (
mainly collagen) , embedded in a loose matrix.
_contain potential cavities (areolar) , which may be filled with fluids or gases. ( dah fe 7alet el
inflammation ( edema)).
▪sites:
1) present all over the body except the brain.
2) around organs and blood vessels.
3) under epithelium, (3ashan El epithelium by3tmd 3alih 3ashan dah rich fel blood vessels) , in
submucosa & derms of skin
▪ function:
1) it binds tissue together & surrounding the organs.
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2)it supports epithelium and blood vessels.
2. ➡ Reticular C.T:
▪structure: it's formed of:
a) reticular fibers: fine branching Fibers.
b) reticular cells: these are modified Fibroblasts
They are branched cells with long processes that are connected with each other.
Reticular cells and fibers form a network ( reticulum) which is stained brown by silver stain.
(Ag)
▪site& functions: both reticular cells and fibers form the framework (stroma) of organs ***[to
support the functioning cells e.g: lymph node, spleen & liver. ]
3. ➡ Adipose C.T : it's a loose C.T. In which fat cells predominate. It consists of groups of
fat cells, separated by fibrous septa
****!they are two ✌ types ;
✳white Adipose C.T:
▪structure: _ unilocular fat cells: large with flat peripheral nucleus.
_ each cell contains a large single fat droplet
_ fat is not pigmented
_poor blood supply.
▪sites:- under the skin.
-Mammary gland.
- around the kidney.
▪functions: -storage of fat.
-(v.I) ➡Heat insulator.
-support of organs e.g kidney.
-Forms the body contours, especially in females.
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✳Brown adipose C.T:
▪structure: multilocular fat cells :smal with central rounded nucleus,
Each cell contain many fat droplets
The Fat is pigmented due to:
a) high Vascularity
b) Cytochrome pigments in mitochondria.
▪sites: ➡in fetus & new born. :interscapular region &axilla.
➡in adults: only around the thoracic Aorta
▪function: heat generation (in newly born infants).
4.
➡ mucoid C.T.:
▪structure: formed of :
_large amount of jelly -like ground substance rich in mucus and hyaluronic acid.
_UMCS & Fibroblasts that communicate by thier processes.
_ fine collagen fibers.
▪sites :
_Umbilical cord (known as wharton's jelly).
_ pulp of growing teeth.
_vitreous humor of the eye.
▪function: it protects near_by structures from pressure.
II)DENSE types of C.T.proper:
1.
➡
white fibrous C.T.:
▪structure: formed of :
Bundles of collagen fibers and Fibroblasts with minimal ground substance.
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▪Types: it has two ✌ types according to the arrangement of collagen bundles:
A) regular. White fibrous C.T:
▪structure: parallel collagen bundles with Fibroblasts in_between.
▪sites: tendons & cornea
▪function: withstand stretch in one direction.
B) irregular white fibrous C.T.:
▪structure: irregulary arranged collagen bundles with Fibroblasts in-between.
▪sites: periosteum, perichondrium, derms of skin, capsule of organs.
▪ function: withstand stretch in different directions.
2.
➡ yellow elastic C.T.:
▪ structure: formed of:
_Mainly elastic fibers (so appears yellow in fresh state) .
_Fibroblasts.
▪ sites: ➡Aorta - Bronchi & Bronchioles
➡ligaments
▪function: recoil after stretch..
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