Connective Tissue I 2024 PDF

Connective Tissue By Prof. Dr./ Usama Kamal Moawad Professor of Histology and Cytology  General Characters of Connective Tissue It is called connective, because it is specialized to connect, bind, support and protect the other tissues of the body. Origin: T...

Connective Tissue By Prof. Dr./ Usama Kamal Moawad Professor of Histology and Cytology  General Characters of Connective Tissue It is called connective, because it is specialized to connect, bind, support and protect the other tissues of the body. Origin: The connective tissue is mesodermal in origin. Vascularity: It may be vascular (loose connective tissue), highly vascular (bone) or avascularegalitrac( ). It consists of cells ,fibers ‫مرنه‬citsale ,negalloc( and reticular Fs(and intercellular substances or the matrix (soft non ro sedirahccas ylopocum detahplushard detahplus mucopoly saccharides ) Components of CT  1 CT cells (I) Connective tissue cells: They are all mesodermal in origin except melanocytes are ectodermal in origin. (I) They are classified according to function into: A) Cells responsible for generation and maintenance of C.T: 1- Undifferentiated mesenchymal cells (UMCs). 2. Pericytes. 3- Endotheial cells. 4. Fibroblasts. 5- Chondroblasts.. 6. Osteoblasts B) Cells responsible for defense and immunity ‫المناعه‬: 1- Macrophages ‫البلعميه‬. 2. Plasma cells. 3.Mast cells. 4. Leucocytes. C) Cells responsible for storage and metabolism: 1`- Fat cells ( adipocytes). 2. Pigment cells ( melanocytes). 2- Classifiication of CT. cells according to state Fixed cells Wondering or free cells 1- Undifferentiated 1- Mast cells. mesenchymal cells (UMCs) 2- -Fibroblasts. 2-plasma cells. 3-- fat cells 3 -leucocytes. 4-fixed macrophages 4 - free macrophages 5- pericytes 6-- endothelial cells  1. Stem cell or undifferentiated mesenchymal cells or mother cell ▪T hey are undifferentiated embryonic connective tissue cells. They are numerous in embryos while in adults these cells are localized at: 1. Bone marrow (blood cells). 2. Around blood vessels ( pericytes). Structure: - LM: Shape: they are small irregular branching, star shaped cells. Nucleus: is large, oval or spherical and lightly stained as well as centrally located with prominent nucleolus. Cytoplasm are pale basophilic. - EM: - They contain few cytoplasmic organelles,abundant ribosomes and fine chromatin in the nucleus  Functions: - They have the ability to divide and differentiate into any other type of C.T cells so it is considered as mother or stem cells.  2- Pericyte ‫الخاليا المحيطه باالوعيه الدموية‬ ◼ -Def. They are UMCs or stem cell or mother of adult tissue. ◼ Site: around the blood capillaries and sharing the basal laminae ‫الصفيحه القاعديه‬of endothelial cells. LM: They are flattned, branched cells and lightly stained cytoplasm with oval nuclei. ◼ EM: The cytoplasm contains few organelles as Mitochondria, RER & euchromatic N. ◼ Functions: 1. Can differentiated into other cells as fibroblasts or smooth muscle cells. 2. They are contractile cells which leading to vasoconstriction ‫انقباض الوعاء الدموى‬.  3- Endothelial cells Sites: lining all blood vessels and heart. Structure: they are simple squamous epithelial cells having little cytoplasm with few organelles and flat nucleus. Functions: 1. They can be differentiated into new endothelial cells. 2. They produce special type of collagen (type IV) 3. They produce their own basal lamina.  4- Fibroblast ‫الخاليا الليفيه‬ Origin: UMCs. - Sites: the most common type in the C.T proper. - Structure: LM: Shape: They are large irregular or fusiform ‫مغزلية‬ branching cells with long and thin cytoplasmic processes. cytoplasm :is basophilic Nucleus: is large, oval, and vesicular with prominent nucleolus.  EM Their cytoplasm rich in organoids responsible for protein synthesis i.e. well developed Golgi apparatus, RER, mitochondria ,ribosomes and secretory granules. Their nuclei are euchromatic N. Their ultrastructural features give indication of active protein synthesis. Functions: 1. These are the principle cells of the connective tissue which produce all types of C.T fibers (collagen, elastic and reticular) also responsible for production of amorphous ground substances. 2. Fibroblasts are essential during wound healing and repair of C.T after injury. Fibroblast and fibrocyte  Fibrocyte (aged fibroblast) Inactive cells ◼ Sites: the most common type in the C.T proper LM: Shape: , small in size, flattened in shape with fewer cytoplasmic processes. The cytoplasm is lightly acidophilic. ◼ Nucleus: is small, oval, and darkly stained. ◼ EM:- little and ill developed cytoplasmic organelles. ◼ - Their nuclei are hetero chromatic ◼ Function : maintenance of CT. elements  5- Plasma cell origin: developed from B- lymphocytes. Sites: numerous in lymphoreticular tissues‫األنسجة الليمفاويه‬ LM: Shape.sllec diovo : ◼Cytoplasm deniatsnu( elap htiw cilihposab ylpeed :.egami igloG evitagen dellac)aera ◼The nucleus is rounded ,eccentric and having a characteristic feature which looks like a spokes of cart-wheel ‫ اسالك عجلة العربه‬or clock-face ot eud regular radial ‫ شعاعى‬arrangement of chromatin along the inner surface of the nuclear memberane. ◼EM: - They have EM features of protein producing cells as extensive granular RER, GA, mitochondria and ribosomes. ◼Functions: - Synthesis and secretion of antibodies AB (humral immunity).  6- Mast cell sites: loose C.T and in vicinity of ‫المنطقه المجاورة‬the small blood vessels. LM: Shape era yeht :ovoid cells with few cytoplasmic processes. ◼Cytoplasm is engorged with a huge number of large, coarse metachromatic granules i.e., the color of granules is not the true color of the dye used to stain them. ◼Nucleus is small, eccentric hcihw elap dna ‫ مغيبه‬derucsbo(masked or hidden) by these granules. EM Have EM features of secretory cells as well developed RER; mitochondria, Golgi apparatus and electron dense memberane- bounded secretory granules. Functions: Mast cells play an important role in detecting foreign substances and initiating a local inflammatory response in the tissue in the form of: 1. Secretion of histamine which causing vasodilatation, increasing permeability of blood capillaries during allergic reaction. 2. Secretion of heparin which prevent the blood clotting (anticoagulant substance). 3. Secretion serotonin which cause contraction of smooth muscle. 4.Secretion of eosinophil chemotactic factor which attract eosinophils to site of allergy ‫حساسية‬.  7- Adipose cells adipocyte (fat cells ( - Origin: They are developed from mesenchymal cells by gradual accumulation of lipid droplets in the cytoplasm. Then the lipid droplets either fuse with each other forming one large fat globule called white fat cells (unilocular adipocytes) or persist as multiple fat droplets scattered in the cytoplasm called brown fat cells (multilocular adipocytes).  A. White fat cells: They are called unilocular adipocytes Sites: most abundant in white adipose C.T - Structure: LM ❑Shape:They are spherical in shape when present singly or polyhedral in clusters. ❑Cytoplasm: They contain single large fat globule which fill the cell surrounded by very thin rim of acidophilic cytoplasm. ❑Nucleus is compressed, flattened and bulged peripherally. ❑ In H&E stained sections the fat globule is dissolved during dehydration leaving large empty space so the fat cells have a signet ring appearance. In frozen sections, they can be stained orange by Sudan III or black by Sudan black or osmic acid stains. White fat cell stained with: ◼ Sudan III ◼ Sudan Black&Osmic acid H&E ◼ -EM: A fat droplet appears as electron dense non memberanous inclusion occupies most of cytoplasm. Cytoplasmic organelles as well developed mitochondria , SER and Golgi apparatus are present - Functions: 1. Storage of fat. 2. Support and protect of some organs as kidneys 3. Source of energy and heat.  ◼ B) Brown fat cells: ◼ They are called multilocular adipocytes. ◼ Sites ni ylniam tneserp :brown adipose tissue in rodents , ‫ القورض‬embryos ‫ االجنة‬and hibernating animals LM: Shape: are rounded or polygonal in shape small in size. ◼ cytoplasm ,osla stelpord dipil llams elpitlum sniatnoc : evahabundant cytochromes –rich mitochondria which give the brownish coloration of the cells. ◼ Nucleus :spherical and eccentric ◼ Functions: They provide more heat & energy for embryos rodents ‫ & القوارض‬hibernating‫ البيات الشتوى‬animals.  8- Fixed macrophages (Histocytes or Clasmatocytes) ❑origin: they are originated from monocytes (a type of white blood cells) which migrate to the loose C.T and become fixed when attached to the C.T fibers. ❑- Structure: a) LM: Shape: are large branched cells with irregular cell boundaries due to presence of pseudopodia Nucleus: They have small, eccentric darkly stained, kidney shaped nuclei. Cytoplasm is acidophilic, granular and vacuolated. It can be demonstrated by using special stains as Indian ink or trypan blue, phagocytic granules were seen in the cytoplasm of histocytes. b) EM: The cytoplasm contains numerous lysosomes, primary and different types of secondary lysosomes, phagosomes, residual lysosomes, multivesicular bodies and autophagic vacuoles. Also, well developed RER, prominent Golgi apparatus were present in the cytoplasm. - Functions: 1. They are phagocytic cells which can phagocytose and digest foreign particles. 2. clean wounds from debris ‫حطام‬ 3. Many histocytes fuse with each other to form multinucleated cells called foreign body giant cell which engulf large foreign bodies.  Free macrophages Origin: derived from blood monocytes then migrate to the C.T tissue and transformed into macrophages. Sites: They described as free cells as they are wandering in C.T. They take different names according to the tissue located in: - In liver …………… Von Kupffer cell. - In lung …………… dust cell or heart failure cells. - In spleen ……….... Littoral cell. In CNS …………… mesoglia cells or microglia cells In skin …………… Langerhan’s cells In in kidney …………. Mesengial cells. - Functions : have the same structure and function of fixed cells..  9- pigment cells (Melanocytes( origin: are ectodermal in origin which derived from the neural crest. Site: located in-between the basal cells of the stratified epithelium of the epidermis ‫ البشره‬of skin, hairs, iris‫ القزحيه‬and choroids ‫المشيميه‬ of eye. LM: small dehcnarb gnol ssessop seidob llec dednuor htiw sllec.sessecorp cimsalpotyc Nucleus :- small, rounded and central ◼Cytoplasm contain melanin granules (melanosomes) which difficult to be seen with H&E. It can be identified by only by histochemical methods, DOPA reaction that blackens the cells and also detecting of tyrosinase enzyme. ◼EM: Melanocytes have the typical EM features of protein synthesizing cells ynam RER tnadnuba ,AG tnenimorp sa.selcisev yroterces dna semosobir ,airdnohcotim ◼Functions:.ninalem fo sisehtys -  Functions: - Melanocytes are responsible for sythesis of melanin which is essential to absorb and disperse the harmfull effect of ultraviolet rays and thus prevent the sunburn. N.B: melanophores or melanophages differ from the melanocytes which are mesodermal in origin. They are called C.T macrophages in dermis ‫االدمه‬and considered as melanin eating cells they phagocytose melanin paricles from disintegrating ‫المفككه‬or aging melanocytes.These cells lacking tyrosinase enzyme and showed –ve DOPA reaction.  Types of CT fibers There are three types: 1. White collagen fibers. 2. Yellow elastic fibers. 3. Reticular fibers. 1) White collagen fibers: - They are long wavy branching bundles composed of non branching fibrils. ❑ They are called white because in fresh state their color is white when condensed as in tendons ‫االوتار‬and ligaments ‫االربطه‬ ❑ Types: They are classified into 5 main types according to the site and the cell of origin: type I, type II, type III, type IV, type V.  characters ❑White in fresh state. ❑ flexible ‫مرن‬not elastic ‫مطاط‬. ❑They are the most numerous of C.T fibers. ❑They produce gelatin (glue) on boiling. ❑They are destroyed by acids and alkalis. Structure: LM: ❑They are formed of fine parallel fibrils which run in long wavy bundles. The individual fibrils never branch but the bundles branch. ❑They are stained pink -‫وردى‬with H&E. while they are stained in different colors with special stains as red by Van Gieson’s stain; green to blue by Masson’s trichrome stain. ❑Functions: Give strength and rigidity to the tissues and resist a pulling force.  B) Yellow elastic fiber ❑ They are thin, long and branched fibers not formed of fibrils and not run in bundles. ❑They are yellow in dense elastic tissue but colorless in individual fibers. ❑They can unit to form elastic membrane Characters ❑yellow in fresh state. ❑ They possess considerable elasticity so; they can be stretched to over double length and return to original dimensions without deformity. ❑ Less numerous. ❑Resist boiling. ❑Resist chemicals. ❑Types : one type. Structure : ❑LM: They cannot be easily identified by H&E but can be selectively stained brown with orcein and weigert’s elastic stain. Functions: Because of their property of easily stretching and recoiling they are found in structures where stretching without breaking is essential as large arteries, external ears and epiglottis. C) Reticular fibers ❑They are very thin, short, highly branched and anastomosing with each other forming a network or reticulum in which the parenchyma is suspended. ❑LM: They are not stained with H&E, but can be specifically stained; black by silver impregnation methods (Gomori’s reticulin stain) so, reticular fibers are called argyrophilic or argentaffin fibers. also, they appear purple ‫ارجوانى‬by PAS technique due to their high content of glycoproteins.. Functions: Reticular fibers form fine network in the stroma and parenchyma of important organs specially lympho reticular tissue and glandular structures.  III) Amorphous ground substance (matrix) It is the interstitial substance of the connective tissue in which cells and fibers are embedded. It varies widely in amount and structure. It increased in both areolar and mucous C.T but is minimal in other types. It is described as an amorphous (shapeless),gellike substance. It is homogenous and transparent and is seldom ‫ نادر‬seen in routine histological sections. Structure: - The ground substance is a complex mixture of water, mineral salts, glycoproteins, and mucopolysaccarides which recently is described as glycosaminoglycans (GAG). The latter appear in to forms either:  1. Sulfated as (chondrotin sulfate , keratin sulfate , heparan sulfate) which persent in cartilage, bone. 2. Non- sulfated as (hyalourinic acid): which predominant in soft tissues as embryonic tissues, loose C.T, synovial fluid, vitreous body. Functions: 1.It controls passage of pathogens from C.T into blood 2. It allows the diffusion of oxygen, nutrients and waste products between the blood & cells. N.B: - Blood is considered a special type of C.T. containing cells, fluid matrix but with no fibers. The matrix is either soft (loose C.T.), rubbery and firm (cartilage), hard and calcified (bone) or even liquid (blood).  Types of connective tissue According the relative amount of basic components of the C.T (cells, fibers and matrix) C.T is classified into: I) Emryonic C.T. 1- mesenchymal C.T 2- Mucous C.T II) Adult proper C.T 1. Loose C.T 2. White dense fibrous C.T 3. Dense elastic C.T 4. Reticular C.T 5. Adipose C.T III) Adult supportive C.T 1- Cartilage. 2. Bone.