General Histology 2 PDF

Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani TISSUES OF THE BODY EPITHELIAL TISSUE - Formed of large number of closely aggregated cells of a similar type and little intercellular substance. – All three embryonic germ layer take part in the f...

Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani TISSUES OF THE BODY EPITHELIAL TISSUE - Formed of large number of closely aggregated cells of a similar type and little intercellular substance. – All three embryonic germ layer take part in the formation of the epithelium 1- Ectoderm: [external] body surface → skin → mouth → nose 2- Endoderm:- lining epithelium of → digestive tract → glands of digest-tract ( liver, pancreas) → respiratory tract. 3- Mesoderm:- lining of → vascular system → closed body cavity→ parts of uroginital system. Types of epithelial tissue: 1- Simple epithelium (cellular sheets formed of one layer cells) 2- Stratified Epithelium (formed of many layers of cells one above the other) 3- Glandular epithelium (cells forming glands) 4- Neuro-epithelium (cells acting as receptors) 27 Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 28  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 1- SIMPLE EPITHELIUM Types of simple epithelium 1- Simple squamous 2- Simple cubical (cuboidal) 3- Simple columnar 4- Simple columnar ciliated 5- Pseudo stratified columnar 6- Pseudo stratified columnar ciliated. 1. SIMPLE SQUAMOUS EPITHELIUM - It is formed of one layer of flat cells with flattened nuclei. - It formed a thin smooth surface to allow easy passage of fluids or organs. - It facilitates the movements of viscera. Simple squamous epithelium lines the following parts in the body: a- The endothelium of the heart and blood vessels b- The mesothelium of serous membrane as: pleura (Around the lung), pericardium (around the heart) and peritoneum (around the intestine). c- Peripheral layer of Bowman's capsule of the kidney. d- Alveoli of the lung e- Anterior chamber of the eye ball f- Descending limb of Henley's loop in the kidney. g- Surface epithelium of adult ovary. 29  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 2. SIMPLE CUBICAL ( cuboidal) EPITHELIUM - Formed of one layer of cubical-cells with central rounded nuclei Function: is mainly responsible for secretion or covering. It is present in: a- Lining the thyroid follicles b- In kidney: lining its convoluted tubules and its small collecting tubules c- In eye: Covering the anterior surface of lens and the inner cells of choroids. d- In Glands: lining the acini and small ducts of glands. e- In ovary: in newly born infants it forms the germinal epithelium of the ovary. 3. SIMPLE COLUMNAR EPETHELIUM ( non-ciliated) 30  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - It is formed of one layer of tall columnar cells with basal oral nuclei Function: it is concerned with secretion, absorption and production. Present in : a- In stomach, simple columnar secrete mucin so they have clear cytoplasm b- In the intestine, they have dark cytoplasm and the surface is covered with microvilli which are rich in phosphatase enzymes in order to facilitate the absorption processes. c- Lining the gall bladder, the common bile duct and the pancreatic duct. d- Lining the large collecting tubules of the kidney. 4. SIMPLE COLUMNAR EPETHELIUM (ciliated) - It is formed of simple columnar cells with basal oval nuclei. Their free borders are covered with cilia. - Cilia are responsible for transport of solid or fluid particles. They help in sensory reception. Present in: a- Central canal of spinal cord and brain ventricles (ependymal cells). b- Fallopian tube and uterus (some of their lining cells are ciliated to facilitate the movement of ova). c- Outer or bony part of Eustachian tube. d- Some bronchioles of the lung. 31  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 5. PSEUDO-STRATIFIED COLUMNAR EPETHELIUM (Ciliated or non-ciliated) - It is simple type of epithelium, formed of one layer of columnar cells resting on a clear wavy basement membrane. - Cells are irregular in shape and size - Their nucleus located at various levels, that why the epithelium appear to have several layers. - All the cells reach the basement membrane, but some of them may reach the free surface. - Surface may ciliated or non-ciliated - Goblet cells may be present between the columnar cells, their upper ends reach the surface, and they secrete mucus secretion. - Present in: a- The upper respiratory passages as: nasal air sinuses, nasopharynx, and lower part of the larynx, trachea and bronchi. b- Eustachian tube (in its inner or cartilaginous part). c- Lacrimal sac. Function: 32  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - This type of epithelium is responsible for; protection, secretion and transport of particles out of the air passages. If it is non-ciliated – it is present in: - Large ducts of salivary glands - Upper part of male urethra - Upper part of vas defense. 33  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani II. STRATIFIED EPETHELIUM Stratified epithelium is formed of many layers of cells (3 or more layers) Types of Stratified Epithelium: It is named according to the most superficial cells, so we have four types: 1- Stratified Squamous Epithelium (the superficial cells are squamous) 2- " Columnar " (" " " " columnar) 3- " " ciliated epithelium (the superficial cells are columnar ciliated) 4- Transitional Epithelium (the superficial cells are broad cuboidal) 1: STRATIFIED SQUAMOUS EPITHELIUM - It is a thick type of stratified epithelium formed of many layers of cells, one above the other. The number of layers ranges from 5 to 30 layers of cells. - The cells are rest on basement membrane - Under the basement membrane there is C.T containing blood and lymph vessels 34  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - The basal cells are formed of columnar cells with oval basal nuclei, from these basal cells, the other layers germinate. - The intermediate layers are polygonal cells (have many sides). - The superficial layers of cells are flat squamous cells which may be nucleated or not. - They are exposed to air - Surface covered with Fresh non-keratinizing squamous cells as in esophagus. - In other area as in Skin, it is covered with Keratin Layer - It has protective function. So it is present in →→ (keratinizing) a- Epidermis of skin b- External Ear, nose, outer surface of the lip and the anal orifice Non-keratinizing →→ present in: - Oral cavity, inner surface of the lip, tongue, gum and palatine tonsils. - Oesophagus, oropharynx and vocal cords. - Cornea and the exposed part of the conjunctiva. - Vagina, terminal parts of male and female urethra and anal canal. 2. STRATIFIED COLUMNAR EPITHELIUM - It is similar in structure to stratified squamous epithelium but: - Its layers are less in number. - The superficial cells are non-keratinizing columnar cells It is present in the following area: a- Fornicies of conjunctiva of the eye b- Penile part of male urethra 35  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani c- Large ducts of glands. d- Recto-anal junction 3. STRATIFIED COLUMNAR CILIATED It is similar in its structure to stratified squamous epithelium but: - It is formed of few layers of cells - The superficial cells are non-keratinizing columnar ciliated cells This type of epithelium is present in: a- Foetal oesophagus b- Nasal surface of soft palate c- Laryngeal surface of epiglottis 36  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 4. STRATIFIED CUBICAL EPITHELIUM When the free surface of the stratified epithelium is covered with cuboidal cells, It is called stratified cubical. It is present in : - Ducts of sweat glands - Seminiferous tubules of the testes 37  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 4. TRANSITIONAL EPITHELIUM - It is a stratified type of epithelium which is present in the urinary tract - Its superficial cells are cuboidal in shape with convex outer surfaces and concave inner surfaces. - The superficial cells are covered with a mucous-like substance, and a protecting membrane. - This membrane acts as an osmotic barrier between urine and tissue fluids, it also protects the epithelium from the high acidity or high alkalinity of urine - The basal cell layer is formed of high cuboidal cells - The intermediate cells which are present between the basal and superficial layers are polyhydral cells and are separated from each other by mucus-like substance in their intercellular spaces - The presence of mucous substance between the cells facilitate gliding of cells on each other, so the transitional may be formed of 3 to 4 layers only in full distended urinary bladder or 6 to 8 layers in an empty bladder. - The superficial cells may change temporarily into squamous cells when the bladder is full of urine. It is present in: a- Minor and major calyces of the kidney b- Pelvis of the ureter, the ureter and the urinary bladder c- The prostatic part of male urethra and the inner part of female urethra 38  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani GLANDULAR EPITHELIUM It is the third type of epithelium which is specialized to produce secretion. - It is formed of collections of epithelial cells, and is classified by many different ways: The different glands in our body are classified according to the following classifications: 1. According to presence or absence of ducts, the glands are classified into: a- Endocrine or ductless glands secreting hormones directly in blood as: Thyroid, parathyroid, pituitary, suprarenal, pineal body, islets of lagerphone's, placenta, corpus luteum and special cells in the testis and ovary. 39  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani b- Exocrine glands: They have ducts to carry their secretions. E.g. salivary glands, sweat and sebaceous glands. c- Mixed glands, which possess the exocrine and endocrine functions as : pancreas, testis and ovary. 40  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 2. according to number of cells, the glands classified into: a- Unicellular gland: as goblet cell which is formed one cell and is considered as a gland and is present in : respiratory tract, intestinal tract, pancreatic and bile ducts. b- Multicellular glands (Formed of many cells) as the salivary glands. 3. according to changes in the secretory cells, the glands are classified into: a- Merocrine gland: in these glands there is no cellular change in their secretory cells; for example: the salivary glands. 41  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani b- Apocrine gland; in which the tips of the secretory cells of the gland are detached and come out with the secretory products of the gland e.g. mammary glands secrete milk which contains parts of the secretory cells. c- Holocrine gland ; in which the whole secretory cells are destroyed and come out with the secretion e.g. the cells of sebaceous glands may come out with their secretion. 4. The glands are classified according to the kind of secretion into: a) Serous secretory glands – as parotid gland and Von Ebner gland of the tongue. b) Mucous " " _ as Brunner's gland and goblet cells. c) Mucoserous " " _ as submandibular and sublingual glands. d) Fatty secretory glands _ as sebaceous glands. e) Watery " " _ as sweat glands. f) Waxy " " _ as glands of external ear. g) Cellular " " _ as testis and ovary. 5. According to shape and branching of the secretory part of the glands and the shape and branching of their ducts: The shape of the glands may be: Tubular, alveolar or Tubulo-alveolar. 42  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani TUBULAR GLANDS 1. Tubular Glands which may be: a) Simple tubular glands: as the intestinal glands or the crypts of Lieberkuhn. b) Simple branched tubular: as the glands of the stomach. ALVEOLAR GLANDS 2. Alveolar Glands which may be: a) Simple alveolar: as sebaceous glands of the skin. b) Simple branched alveolar: as the sebaceous and tarsal glands of eye lid. c) Compound alveolar: as the sebaceous gland and mammary gland. TUBULO-ALVEOLAR GLANDS 3. Tubulo-alveolar Glands: which may be: a) Simple Tubulo-alveolar: not found in man. b) Branched tubulo alveolar: as the glands of the mouth cavity. c) Compound tubulo-alveolar: as pancreas, prostate and salivary glands. 6. The glands can be classified according to their functions into: Secretory and excretory Glands. a) Secretory Glands: which synthesize specific substances to be secreted in the body as salivary and endocrine glands. b) Excretory Glands: which eliminate and excrete the waste products outside the body as kidney and sweat glands. GENERAL CHARACTERISTICS OF EPITHELIUM TISSUE 1. Epithelium may arise during embryological development from ectoderm (as skin), from mesoderm (as mesothelium of serous membrane) or from endoderm (as the epithelium of the intestinal tract). 2. Blood vessels do not penetrate between epithelial cells except in endocrine glands but nerve fibres can penetrate between the epithelial cells. 3. Epithelium rests on a basement membrane which may be clear or none clear. The non-clear basement membrane is present in: Transitional epith, olfactory epith, thyroid follicles and liver cells. 4. Epithelium can degenerate (destroyed) and can rapidly regenerate (renewed). 43  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 5. Epithelium has a little intracellular substance but the epithelial cells may be connected with each other by different types of cellular junctions. 6. Epithelial tissues cover a surface or line a cavity or form a gland. 7. Epithelial cells may act as special receptors for taste and equilibrium. FUNCTIONS OF EPITHELIAL TISSUES: 1. Protection against injuries, bacteria, chemicals and water as epithelium of skin and stomach. 2. Secretion as glandular epithelium of pancreas, prostate, salivary and endocrine glands. 3. Absorption as the intestinal epithelium. 4. Sensation as the taste buds and organ of corti. 5. Reproduction as the cells of the testis and ovary. 6. Excretion as the cells of kidney and sweat glands. 7. Covering surfaces or lining cavities. ………………………………………………………………………………………… 44  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani CONNECTIVE TISSUE The mesoderm of the embryo gives rise to mesenchymal tissue (U.M.C. = undifferentiated mesenchymal cells and homogeneous intracellular substance of proteins). The mesenchymal tissues are differentiated in the embryo into: 1. Connective tissue = C.T. 2. Vascular tissue. 3. Smooth muscles. The connective is formed of: (a) Cells (b) Fibres (c) Matrix TYPES OF CONNECTIVE TISSUE According to the nature of the intercellular matrix we have three types of connective tissue: 1. Connective tissue proper which have soft matrix. 2. Cartilage which has a rubbery matrix. 3. Bone which has a solid matrix. 45  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani CONNECTIVE TISSUE PROPER It is called connective because it supports, binds and connects various tissues and organs. The connective tissue is formed of: 1. C.T. cells. 2. C.T. Fibres. 3. Soft matrix or ground substance. TYPES OF CONNECTIVE TISSUE PROPER The different types of C.T. cells and C.T. fibres are present in the soft C.T. matrix in order to form the following 6 types of C.T. Proper: 1. Areolar C.T. 2. Adipose C.T. 3. Yellow elastic C.T. 4. White collagenous C.T. 5. Mucoid C.T. 6. Reticular C.T. 46  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani TYPES OF CONNECTIVE TISSUE CELLS: There are 8 types of C.T. cells: 4 are branched cells and the other 4 are oval or rounded cells: The branched C.T. Cells are: 1. Mesenchymal cells. 2. Fibroblast Cells. 3- Histiocyte cells 4. Pigment cells. The oval C.T. Cells are: 47  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 1. Fat cells 2. Plasma cells 3. Mast cells 4. Leukocyte cells.......................... THE FOUR BRANCHED C.T. cells 1- UNDIFERENTIATED MESENCHYMAL CELL = U.M.C. - It is embryonic branched cell with large oval nucleus and basophilic cytoplasm. - It is present mainly in the embryonic tissue - It can differentiate into other types of C.T. cells - It may remain undifferentiated in certain areas in the body. - in adults the U.M.C are very important because they serve as Progenitor Cells (mother cells) for certain cells in the body. 48  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani These are the Progenitor Connective Tissue Cells in the body: 1. The U.M.C. in the bone marrow: these cells differentiate into blood cells. 2. The Endothelial Cells: - Present in the entire surface of blood capillaries and blood vessels - Developed from embryonic mesenchymal cells - They synthesize collagen - Divided to form new capillaries in tissue injuries 3. The Pericytes: (peri = around) - Pale branched cells with long cytoplasmic processes - Present immediately external to the endothelium of blood capillaries and small venules, - It considered as mesenchymal cells which persist in adult life - It can give rise to both fibroblasts and smooth muscle cells - Play an important role in the process of healing of C.T. and blood vessels whenever wounds are present 49  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 2. FIBROBLAST and FIBROCYTE: - develops from the pericytes - When becomes mature and less active changes into fibrocytes - Fibroblast means fiber-forming cell. and it can form the C.T. fibres - It is branched cell with multiple processes - Their cytoplasm is deeply basophilic in staining, it is very rich in RNA, G.E.R. and G.A because it is actively synthesizing proteins - The nucleus is oval in shape and has little amount of chromatin, thus it appears pale in stained sections. Functions of Fibroblasts: - They form collagen in the form of a precursor known as procollagen which aggregate to form the collagenous fibres. - They can secrete the elastic material to form elastic fibres. - " " " " mucoprotein in order to form the C.T. matrix. - They can divide to increase their number during growth of tissues or during inflammation or during healing of wounds. - Play an important role in repair of wounds and formation of scar tissue. 50  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 3. HISTIOCYTE OR MACROPHAGE: - More present in the Vascular C.T. areas as in the serous membrane and alimentary canal. - They are also called clasmatocytes. - They are usually branched with multiple processes. - They have irregular cell membrane due to presence of pseudopodia. - Their cytoplasm is not clear, it may granular and vacuolated - It has large number of lysosomes - Nucleus is small, Kidney-shaped, and very rich in chromatin and is darkly stained. FUNCTIONS OF MACROPHAGES: - They play an important role in the defense mechanism of the body. - They can engulf (eat) foreign bodies, bacteria and old blood cells. - They can clean wounds from foreign bodies and debris - They can trap and transport antigens - Some of them may collected with each other to form a Multinucleated Giant Cell known as Foreign body giant cell which can surround and enclose large foreign bodies, in order to destroy them. 51  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 4. PIGMENT CELL: - It is found in C.T. of skin, choroids and iris of the eye in man - More common in lower animals as in frogs where they are sensitive to light - They are also called Chromatophores or Melanophores because they carry melanin pigments - They are small cells with many branching processes - The nucleus is small, rounded and usually present at one side Function: - They responsible for the synthesis of melanin pigment which is essential to protect the body from the harmful effects of exposure to the ultraviolet rays in sun light - They can absorb and disperse ultraviolet light and thus prevent sun burn ……………….. THE FOUR OVAL C.T. CELLS 1. FAT CELL OR ADIPOCYTE - It is derived from mesenchymal cell after accumulation of fat droplets in its cytoplasm 52  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - Large oval cell with flat peripheral nucleus (signet ring appearance) - It is contains a large globule of fat which is surround with a small amount of cytoplasm in which the cell organoids and the nucleus are present 2. PLASMA CELLS: - It is rounded in shape with eccentric nucleus and large nucleolus - The condensed chromatin gives the nucleus the nucleus a clock-face - The cytoplasm is basophilic - It shows many ribosome's, prominent Golgi and many mitochondria FUNCTION: - It is developed from B-lymphocytes of the blood - It is produces antibodies and playing an important role in defending the body against infection (immune response and antigen-antibody reaction ) 3. MAST CELLS: 53  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - It is large rounded cell which is very rich in basophilic secretory granules - These granules are Metachromatically stained with basic dyes such as methylene blue - This metachromasia is because of their content of heparin - The nucleus is small and masked by granules - The cytoplasm is full of electron dense (dark) secretory granules Function: - It is tend to be situated close to small blood vessels - The granules of mast cells contain histamine and heparin FUNCTION OF HISTAMINE: - Contraction of smooth muscles (mainly within the bronchioles of lungs) - Dilatation of blood capillaries - Increase the permeability of blood capillaries N.B. Mast cells have an important role during the inflammatory reaction and in relation to allergy and anaphylaxis Heparin: - Heparin is known to prevent blood clotting and agglutination of platelets 4. LEUKOCTES: - Neutrophils, basophils, eosinophils, lymphocytes and monocytes are wandering cells that may migrate from blood stream to the connective tissue - These cells protect the tissues against invasion from micro-organisms................................................................................. 54  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani EXTRACELLULAR FIBRES There are three types of fibers; white collagen, yellow elastic, and reticular fibers 1. WHITE COLLAGEN FIBRES - It is appears as wavy pink (acidophilic) bundle - The fibers do not branch, while the bundle can - Each collagen fibers is composed of parallel fibrils, each fibril is formed of parallel microfibrils Formation of collagen: - Fibroblast is the main cell of origin, however other cells can produce collagen fibers - Collagen fibers are formed of the "protein collagen" which is secreted from fibroblast as "procollagen" - The component polypeptide chains of procollagen molecules are synthesized in fibroblast by RER - Transfer vesicles then deliver these polypeptides to the Golgi apparatus where the carbohydrate component, hexose, is added - Finally procollagen is carried by secretory vesicles to the cell surface where it is released by exocytosis into the intercellular spaces as "tropocollagen" FUNCTION: - The collagen fibers have a mechanical importance in loose C.T - They strongly resist a pulling force and they are flexible but not elastic Types of collagen fibers: Type 1: 55  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - Loose and dense C.T (tendon, fascia, the capsule of organs, collagen fibrocartilage, and bone) - It accounts for 90% of the collagen in the body, and it is originate from Fibroblasts and Osteoblasts Type II: - Hyaline and elastic cartilage, the nucleus pulposus of the intrervertebral discs, and the vitreous body of the eye, and it is originate from chondroblasts and chondrocytes Type III: - Loose C.T, walls of blood vessels, uterus, stroma of various glands and organs, fetal skin and healing wounds - It is originate from smooth muscle cells and fibroblasts Type IV: - Basal lamina of placenta and external laminae of smooth and striated muscles - It is originate from Fibroblasts and muscle cells Type V: - Basal laminae of epithelia - - It is originate from Epithelial cells and endothelium 2- Yellow elastic fibers: It is straight, thin, and long fibers which branch to form a network. - They stain pale pink with H&E sections. They stain brown with orcein dye - Each one is formed mainly of amorphous material (elastin) surrounded by microfibrils Formation of elastic fibers: - It is composed of the protein "alastin" which is formed by fibroblasts and smooth muscle cells Function: - It is not strong as collagen fibers. They stretch easily and then recoil 56  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 3- RETICULAR FIBERS: - They can not be seen by H&E, it is appear as a dark brown fine network by silver staining - It is very thin collagen fibers type III, so they are considered as immature form of collagen fibers FUNCTION: - It is form the delicate network in the stroma of glands and solid organs e.g. lymph node. It is shared in the formation of the basement membrane....................................................................................................................... TYPES OF CONNECTIVE TISSUE PROPER According to the density of matrix and the main cells and fibers found it is classified into: I- Loose connective tissue II- Dense C.T 1- Loose areolar C.T 1- Dense white collagen C.T 2- Adipose C.T A- Irregular 3- Reticular C.T B- Regular 4- Embryonic mesenchymal C.T 2- Dense yellow elastic C.T 5- Mucous C.T.................................... I- Loose Connective Tissue 1- Loose areolar C.T: - All structural elements of C.T, cells, fibers and amorphous substance are present - The most common cell types are fibroblasts and macrophages. - White collagenous fibers are prominent 57  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani Function and sites: - It is the packing and anchoring material and the embedding medium of many structure, including nerves and blood and lymphatic vessels - It binds other tissues, organ components, and organs together - It is found in almost every part of the body 2- Adipose Connective Tissue: - If the loose C.T becomes dominated by FAT CELLS it is called adipose tissue - There are two types of adipose C.T, according to the vascularity and the function, White and Brown A. White adipose connective tissue - It is widely distributed in the body - Fat cells contain one large fat droplet which occupies most the cytoplasm - It appears yellow as it contains pigment Function: - It represents the primary site of fat metabolism and storage in the body B. Brown adipose connective tissue - It is present in small amounts in adults, in fetuses and neonates and then it is gradually replaced by white fat - Fat cell store fat in multiple droplets, not as a single large one like white fat - It is brown color is caused by the high vascularity of this tissue Function: - The main role of brown fat is to provide heat, critical for newborn babies 3: RETICULAR CONNECTIVE TISSUE - It is a primitive type of C.T that is characterized by the presence of a network of reticular fibers associated with primitive reticular cells (mesenchymal-like cells) - It is forms the framework of solid organs e.g. lymphoid organs, bone marrow and liver 4- EMBRYONIC MESENCHYMAL CONNECTIVE TISSUE - It is an unspecialized C.T of the early weeks of embryonic life - It is formed of undifferentiated mesenchymal cells, ground substance and fine reticular fibers 58  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 5- MUCOUS CONNECTIVE TISSUE - It is formed of stellate (branched like a star), fibroblasts, abundant substance (given a mucin reaction) and fine collagenous fibers - It is found in umbilical cord ………………………………………… II- DENSE CONNECTIVE TISSUE - It is characterized by the close packing of their fibers, few cells(fibroblasts and fibrocytes) and small amount of amorphous intercellular material. - According to the type of fibers it is classified into dense white collagenous and dense yellow elastic connective tissues 1- DENSE WHITE COLLAGEN CONNECTIVE TISSUE: - When collagen fibers are predominant in a dense C.T, it is called "dense white collagen C.T" because in fresh state it is white in color - According to the arrangement of the fibers, two types are found; irregular and regular dense white collagen C.T A- Irregular Dense White Collagen C.T - The collagen fibers are arranged in an irregular pattern. There is little ground substance and the cells are mainly fibroblasts and fibrocytes Function and sites: - It can withstand stretch from several different directions - It is found in areas where tensions are exerted in multiple directions e.g. in deep fascia, dermis of the skin, fibrous capsules of organs (liver, lymph nodes) fibrous sheath of cartilage (perichondrium) and bone (periostenum) B- Regular Dense White Collagen C.T - The collagen fibers are arranged in a regular parallel pattern. The cells found are fibrocytes with minimal matrix Function and sites: - It can withstand stretch in one direction - This group includes tendons, aponeuroses (wide, flat tendons expanded into a fibrous sheet), and ligaments 2- DENSE YELLOW ELASTIC CONNECTIVE TISSUE - When elastic fibers are predominant in a dense C.T it is called dense yellow elastic C.T 59  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - It is yellow in color in fresh state - It is formed of regular parallel elastic fibers bound together by a small amount of delicate fibers with many fibroblasts and fibrocytes Function and sites: - These elastic ligaments have the ability to return to their original length after stretching - This type is located in yellow elastic ligaments, ligamentum nuchae( at the back of the neck) and ligamentum flavum (between adjacent vertebrae) 60  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani The blood Site of production of blood: *- In the first few weeks of gestation the (yolk- sac) is the main of haemopoiesis. *- From the six weeks until (6-7) months of foetal life the liver and spleen are the main organs involved and they continue to produce blood cells about (2) weeks after birth. *- The bone marrow is the most important site from (6-7) months of foetal life and during childhood and adults life Table 1: Sites of haemopoiesis Foetus 0-2 months----- yolk sac 2-7 months----- liver, spleen 5-9 months----- bone marrow Infants bone marrow (practically all bones) 61  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani Adult's vertebra, ribs, sternum, skull, sacrum and pelvis, proximal ends of femur *- The marrow is only source of new blood cells Organs shared in haemopoiesis: 1- Bone marrow: - Produces erythrocytes, granulocytes, monocytes, and blood platelets and possible source of lymphocytes. - After birth, erythropoiesis, grnulopoiesis and megakaryocytopoesis occur principally in the bone marrow. 2- The thymus: - The thymus is the central lymphoid organ responsible for receiving precursor cells from the bone marrow. - It is also acts upon these cells to differentiate them into special lymphocytes that become sensitive to antigen. - These cells released to the circulation and go to the spleen, lymph nodes, and other foci of lymphocytic tissues. 3- The spleen: - Lymphocytes of the white pulp of the spleen have immunologic functions. - Spleen become active during some emergency cases such as haemorrhage and increase production of erythrocytes, granulocytes, and megakaryocyte. - Spleen also serves as reservoir for erythrocytes. - Spleen has also some control over erythropoiesis and erythrocyte morphology. 4- The lymph nodes and follicles: - These are scattered throughout the body along lymph channels and are the main source of lymphocytes. - The lymphocytes migrate into sinuses of the nodes and are carried via the lymphatic to the thoracic ducts, whence they are entered the blood stream. - The lymph nodes may serve as extramedullary site for grnulopoiesis. 5- The liver: - It is the main depot for vitamin B12 and folic acid. - It is serves in the storage of excess iron. - Two very important plasma proteins which serving in the blood clotting, namely, prothrombin, albumin and fibrinogen are produced by the liver. 62  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 6- The stomach: - It is playing an important role in preparing vitamin B12 for absorption by the intestinal mucosa. - It is also production of HCL which ionized the food iron to ferric iron. 7- The kidney: - It is claimed that the kidney participates the regulation of erythropoiesis by making an enzyme or principle called renal erythropoietic factor (REF) or erythrogenin. Substances needed for erythropoiesis: 1- Metal:- Iron, Manganese, Cobalt 2- Vitamins:- VB12, Folate, Vit C, Vit E, Vit B6, Pyridoxine, thiamine, Riboflavin and Pantothenic acid. 3- Amino acids 4- Hormones:- Erythropoietin, Androgens and Thyroxine. Erythropoesis: Means the production of RBCs from bone marrow started from Multipotential (STEM CELL) ↓ Unipotential (STEM CELL) _______________↓________________ ↓ ↓ ↓ Red blood cell White blood cell Platelet - These maturation occurs according to the type of stimulation - The morphology of Multipotential stem cell is unknown - They appear similar to small lymphocyte - This stem cell is self-replicates OR differentiate into a Unipotential stem cell [committed] stem cell - Unipotential stem cell include {Red, granular and megakaryocyte} - Erythrocytic Unipotential stem cell is self-replicating and responsive to erythropoiesis, which differentiation to rubriblast. 63  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani Series of maturation of red cell: Rubri Blast (mother cell) Mitotic division ↓ Pro Rubri-cyte (act as Hb synthesis) Mitotic division ↓ Rubri-cyte ↓ Meta Rubri-cyte ↓ Reticulocyte ↓ Mature red cell 1:- Rubri blast: ♠- Large round cell ♠- The nucleus occupy most of the cell ♠- Chromatin of the cell is --- condensed, overlaps and stapled ♠- It has one or more nuclei ♠- The cytoplasm is more deep basophilic due to high amount of RNA ♠- The cytoplasm is thin 2- Pro Rubri-cyte: ♠- Similar to the previous cell except: ♠- It is small in their size ♠- Their nuclei is absent ♠- The chromatic threads is more cons 3- Rubri-cyte: ♠- It is smaller than the previous cell ♠- The nuclear chromatin is condensed and stippled by light steaks OR cart wheal N.B- according to the amount of Hb synthesis the Rubricyte can be classified into: ►Basophilic Rubricyte ►Polychromatophilic Rubricyte ►Normochromic Rubricyte OR Erythrochromic 64  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 4- Meta Rubricyte: ♠The nucleus undergo pgnetic degeneration ♠It is appear as dark blue homogenous mass without distended structure ♠The cytoplasm is polychromatophilic cell OR normochromic 5- Reticulocyte: ♠Non-nucleated erythrocyte ♠If stained by normal stain [gemsa – leshman] it appears blue in color ♠ It contains some organelles as Mitochondria, Ribosomes and Romenet nucleus ◙ Morphological changes which occur during maturation: Decreases in the size i.e dimension in the cell size. N.B the normal size is {7.4} Changes in the nucleus i.e maturation in nucleus Develop of Hb i.e from blue→→→ Green →→→ orange ↓ ∕ \ ↓ RNA RNA Hb high Hb N.B: ►The synthesis of Hb is start in Primitive cell [Pro Rubricyte] ►The normal concentration of Hb is 30-36gm/liter At the late stage of Rubricyte the mitotic division stops when Hb concentration will reach 20% {critical concentration}. Reticulocyte lost their reticular Romenet in bone marrow (2-3 days) and then release in circulation. ◙ CONTROL OF ERYTHROPOESIS; ♠ Erythropoietin Hormone ♠ Sex Hormone ♠ Growth Hormone {cortisone and thyroxin} …………………….. ◘ Erythropoietin hormone: ♦ It is released as response to Hypoxia ♦ It is glucoprotein in nature ♦ It is produced from kidneys ♦ Normally it is present in plasma ♦ It is molecular weight of 30400 ♦ Normally 90% is produced in the peritubular complex of the kidney and 10% in the liver and elsewhere 65  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ♦ It is stimulate erythropoiesis by: □ It stimulate Unipotential stem cell to give mother cell Rubriblast □ It is increased the mitotic division {dupling in number} □ It is shorting the time between each division to increases the number ◙ Sex Hormone: ♦ Male hormones increased the erythropoiesis by increased production of Erythropoietin hormone ♦ Female hormone [Estrogen] decreased Erythropoesis by suppression of Erythropoietin hormone production ◙ Growth Hormone: ♦ Cortisone, Thyroxine, Thyroid, Pituitary and Adrenocortical Hormones increased the Erythropoesis by increase production of erythropoietin hormone ◙ Factors affecting erythropoiesis: 1- ♦ O2 Tension [hypoxia]: The hypoxia may physiological or pathological. ♣ Physiological hypoxia includes both →→ Relative hypoxias ↓ →→ Atmospheric hypoxia In the high altitude the yellow marrow and the red marrow are both under the effect of erythropoietin hormone so the stimulation of the marrow is high and the production of the blood cells are accelerated ♣ Pathological hypoxia: The tissues of the body are suffering from hypoxia as in heart disease and in lung hemorrhage. 2-♦ Kidneys:- ►The hypoxia doesn't stimulate bone marrow directly, but it is stimulating the kidney to release renal erythropoietin factor {R.E.F} from juxtra glomerular apparatus. ►At the same time it also stimulate the liver to release certain alpha globulin in plasma. 66  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ►The R.E.F act on the globulin (from liver) and change it to →→ erythropoietin hormone which will→→ stimulate the bone marrow this processes will lead to increase erythropoiesis. So→ if the person is complaining from both renal disease and liver disease he will suffering from anemia 3-♦ Liver: It plays an important role in erythropoiesis because: □ It forms globulin which change to erythropoietin hormone □ It act as storage for Vit B12 and iron □ It form globin molecule (molecule of hemoglobin) 4-♦ Bone marrow: The healthy B.M is very essential for formation of all blood cells. So if it damage by X-ray or radiation the production of blood cells will decrease. 5-♦ Hormones: Male hormone→→→→↑ the erythropoiesis Female hormone→→→ ↓ " " 6-♦ Diet: The hemoglobin molecule is composed of both globin + Heme which composed of iron and protoporphirine So- the dietetic factor must be including protein, minerals and vitamins. A- Proteins- for globin formation B- Minerals- Iron- for Hb synthesis Cooper- essential for hem synthesis Cobalt- for Vit B12 molecule C- Vitamins- Vit B12, Vit A, Vit C and Folic acid ►Vit B12 and folic acid: They are used for D.N.A synthesis which is essential for mitotic division of the cell. So if they decrease the produced cells will be macrocyte. ►Vit B6-pyridoxine: Which is used as Co.factor to A.L.A synthesis which is essential for Heme Synthesis? ►Vit C: it plays two roles: 67  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 1- It is acts as reducing agent because it changes the complex form of Ferric of iron→→→ Ferrous form which easy to absorb. 2- It covert the complex form of Folic acid→→→ Folinic acid (active form) which essential for D.N.A with Vit B12 Ω - Haemoglobin:- Hemoglobin is a protein that is carried by red cells. It picks up oxygen in the lungs and delivers it to the peripheral tissues to maintain the viability of cells. Hemoglobin is made from two similar proteins that "stick together". Both proteins must be present for the hemoglobin to pick up and release oxygen normally. One of the component proteins is called alpha, the other is beta. Before birth, the beta protein is not expressed. A hemoglobin protein found only during fetal development, called gamma, substitutes up until birth. Haemoglobin synthesis: ☼ - The main function of RBCs is to carry O2 to the tissue and to return CO2 from tissue to the lungs ☼ - They contain the specialized protein, Haemoglobin. ☼ - Each red cell contains 640 million Haemoglobin molecules ☼ - Each molecule consists of four polypeptide chains α2β2. ☼ - The molecular weight (MW) of Hb A is (68000). 68  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ☼ - The switch from foetal to adult haemoglobin occurs 3-6 months after birth. ☼ - Sixty-five per cent of haemoglobin is synthesized in the erythroblasts and 35% at the reticlucyte stage ☼ - Haem synthesis occurs largely in the mitochondria by a series of biochemical reactions starting with→→→ condensation of glycine and succinyl coenzyme A under the action of the key rate-limiting en zyme δ-aminolaevulinic acid {ALA} synthetase ☼ - Pyridoxal phosphate (vitamin B6) is a co-enzyme for this reaction which stimulated by erythropoietin and inhibited by haem. ☼ - Protoporphyrin combines with iron in the ferrous (Fe² +) state to form haem. ☼ - Each molecule of which combines with a globin chain made on the polyribosomes. ☼ - A tetramer of four globin chains each with own haem group in a "pocket" is then formed to make up a haemoglobin molecule. Haemoglobin function: – Red cells in systemic blood carry O2 from lungs to the tissues and return in venous blood with CO2 to the lungs. – As the haemoglobin molecules loads and unloads O2, the individual globin chains in the haemoglobin molecule move on each other. – α1β1 and α2β2 contacts stabilize the molecule. – The β chains slide on the α1β2 and α2β1 contacts during oxygenation and deoxygenation. – When O2 is unloaded, the β chains are pulled apart, permitting entry of the metabolite 2,3-diphosphoglycerate {2,3-DPG} resulting in a lower affinity of the molecule for O2. 69  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani THE RED CELL: - The red cell, 8 µm in diameter is able to pass repeatedly through the microcirculation whose minimum diameter is 3.5 µm. - Its total journey throughout its life span 120-day has been estimated to be 300 miles about 480 Km. - The cell is flexible, biconcave disc with an ability to generate energy as ATP by the anaerobic way. Red cell membrane: - This is bipolar lipid layer containing structural and contractile proteins and numerous enzymes and surface antigens. - About 50% of the membrane is protein, 40% is fat and up to 10% is carbohydrate. 70  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani - The lipid consists of 60% phospholipids, 30% neutral lipid (mainly cholesterol) and 10% glycolipid. - Four major proteins {spectrin, actin, protein 4.1 and ankyrin} form a lattice on the internal side of the red cell membrane and are important in maintaining the biconcave shape. - Defects of the proteins may explain some of the abnormalities of the shape of the red cell membrane, e.g. hereditary spherocytosis and elliptocytosis. - While alteration in lipid composition due to congenital or acquired abnormalities in the plasma cholesterol or phospholipids may be associated with other membrane abnormalities. ▄ RETICULOCYTES: ♥ Reticulocyte is non-nucleated red cells ♥ 7-10 µm in diameter ♥ It is contain RNA, small mitochondria and ribosomes ♥ It gives polychromatic staining with romanosky dyes ♥ It can deforms, motile and has irregular cell margin ♥ It is stimulated by erythropoietin hormone ♥ Reticulum becomes more scantly until only few granules remain ♥ This maturation taken 1-2 days in the marrow followed by 24 hr in circulation ♥ Normal range 3 months fetus 90% 0f circulating red cells 6 months fetus 15-30 % Full term newborn infant for first 3 days 2-7% falling after 3 days to < 1% 71  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani Children and adults 0.5-1.5 % Increased: ∆- After specific treatment for deficiency anemia e.g. iron, vitamin B12 and folic acid ∆- Following hemorrhage or Hemolysis ∆- Myelosclerosis due to reduce of red cell production ∆- Very high in acute erythraemic myelosis ∆- Leucoerythroblastic anemia Decreased due to: ∆- Aplastic and hypoplastic DESTRUCTION OF ERYTHROCYTES; ► The average erythrocyte life span is 120 days ►Aging of erythrocyte is accompanied by changes in enzyme content and cell membrane structure causing a less of flexibility ►In health, senescent erythrocytes are removed from circulation by two routes: □ Phagocytosis by macrophages is the major route □ Intravascular lysis and release of free hemoglobin is a minor route. Phagocytosis "major route" ↓ Macrophage ↓ Hb ∕ \ Heme ←←← →→→→ Globin ↓ ↓ Protoporphirine Protein in nature reutilize again ↓ Bilivirdin ↓ Bilirubin ↓ Free bilirubin (indirect + glucoronic acid) ↓ Conjugated bilirubin 72  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ↓ Urobilinogen (Eliminated by normal filtration) ∕ \ Stercobilinogen Urobilinogen ↓ ↓ Stercobilinogen Urobilinogen N.B. If excessive Hemolysis more than capacity of liver. So the level of bilirubin will increased and it will lead to JAUNDICE. DEVELOPMENT OF BLOOD CELLS The process of development of blood cells is known as haemocytopoesis. ►In adult man, the haemopoietic tissues are divided into two main types: 1- Myeloid Tissue (Bone Marrow) 2- Lymphatic Tissue (lymph nodes, spleen, tonsils, thymus and other lymphatic) THE MYELOID TISSUE Kinds of Myeloid Tissue: Yellow and Red Bone Marrow 1-►Inactive Yellow Bone Marrow: ► It is present in the cavities of the long bones in adult ► It is formed of:- many fat cells, reticular cells and some mesenchymal cells which may change into myeloid cells in certain conditions ► The yellow bone marrow acts as storage area for fat cells, it is also represents the reserve areas for haemopoietic tissue ► It may change into active red bone marrow in cases of excessive loss or destruction of RBCs 2-►Active Red Bone Marrow: ► In the foetus, red bone marrow is present in most of the bones ►In adult man, red bone marrow is found in the sternum, vertebrae, ribs, diploes of the skull, clavicle and in the pelvic bones 73  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani THE WHITE CELLS Granulocytes, Monocytes and their Benign Disorders ► The white blood cells (leucocytes) may divided into two broad groups-the phagocytes and the immunocytes ►Granulocytes, which include three types of cell: neutrophils (polymorphous), eosinophils and basophiles ► Normally only mature phagocytic cells and lymphocytes are found in the peripheral blood ☻GRANULOCYTES Neutrophil appearance: Neutrophil (polymorph): ►Their percentage varies from 60 to 70% of the total leucocytes ► The nucleus is single but segmented, it is formed of 2 to 5 segments connected with each other by chromatin threads ► It has an amoeboid movement, they can protrude pseudopodia in order to engulf micro-organisms ► The cell has dense nucleus consisting of between two and five and pale cytoplasm ► It is contain granules which divided into primary and secondary (specific) ► The granule are lysosomal in origin ► The primary contains myeloperoxidase, acid phosphatase and other acid hydrolase 74  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ► The secondary contains collagenase, lactoferrin and lysosyme ► The granules are: ◙ Azurophilic granules: which are few in number and large in size. They are considered as lysosomes because they are very rich in hydrolytic enzymes ◙ Specific granules: which are numerous and small in size. They contain the mentioned enzymes which are a bacteriostatic substance. ► The lifespan of neutrophils in the blood is only about 10 hours ► The cell has variable size and has a large nucleus with fine chromatin and usually 2-5 nucleoli ►The cytoplasm is basophilic Functions of Neutrophils: ►They are phagocytic to micro-organisms in the tissues outside the B.V ►They secrete photolytic enzymes ►They secrete trephine substances which help in healing wounds ►It is help monocytes to migrate to the inflamed area of the body ►During acute infections and in fever conditions, neutrophils stimulate bone marrow to develop more leucocytes ►Neutrophils may be changed into pus cells in acute infections EOSINOPHILS; ►Their lifespan is about 8 to 12 days ► These cells are similar to neutrophils, except that the cytoplasmic granules are coarser and more deeply red staining ►It has more than three nuclear lobes 75  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ► They enter inflammatory exudates and have a special role in allergic response, in defence against parasites ► Their percentage varies from 1 to 4% of the total leucocytes ►The nucleus is bilobed and is called horse shoe-shaped nucleus ►It is rich in shiny acidophilic granules, and it is considered as lysosomes ► They contain the following enzymes: Histaminase enzyme- to destroy histamine substance Sulphatase enzyme- to destroy sulphate substance which secreted by mast cells Functions of Eosinophils: ◙ They attached to the site of allergic reactions by eosinophil chemotactic factors ◙ It is contains histamine and Sulphatase enzymes to destroy that substances ◙ Eosinophils can phagocytose the antigen-antibody complex in allergic conditions BASOPHILS; ► These are only occasionally seen in normal peripheral blood ► They have many dark cytoplasmic granules and contain heparin and histamine ► In the tissue they become mast cells ► Their percentage varies from ½ to 1% ►Their nuclei are large and irregular in shape ► Their lifespan from 10 to 15 days ►They have IgE attachment sites and their degranulation is associated with histamine release Functions of Basophils: ►Production and carriage of histamine and heparin 76  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ► They are slightly phagocytic cells............................................................. NON GRANULAR LEUCOCYTES MONOCYTE: ► These are larger than other peripheral blood leucocytes ►It has a large central or indented nucleus with clumped chromatin ► The abundant cytoplasm stains blue and contains many fine vacuoles ► The cytoplasmic granules are also present ► Their percentage varies from 3 to 8% ► It appears pale blue due to the presence of azurophil granules which are lysosome bodies in its cytoplasm ► The cytoplasm is rich in acid phosphatase and other enzymes ►Monocytes can penetrate through capillaries and venules to enter the C.T. They can extend and withdraw their pseudopodia ►The nucleus is pale, large and slightly indented, it may kidney shaped. Its chromatin is less condensed than that of a lymphocyte ► Their lifespan is about 3 days in the blood stream Functions of monocytes: ►In C.T., they are highly phagocytic cells; they can be transformed into macrophage cells. ► Macrophage contain more granules and proteolytic enzymes than monocytes ► Macrophages may survive long periods in tissues and capable of division and more phagocytic 77  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ► Macrophages also performed Phagocytosis and digestion of foreign material and dead cells ►Macrophage also synthesis of certain complement components, transferring, interleukin I, and lysozymes and they may be also the major source of interferon …………………………………… LYMPHOCYTES; ► In postnatal life the bone marrow and thymus are the primary lymphopoietic organs ► In the foetus, the yolk sac, liver and spleen are also primary lymphopoietic ► The secondary or reactive lymphoid tissue is found in the lymph nodes and the spleen together lymphoid tissues ► Their percentage varies from 20-30% of the total number of blood leucocytes ► According to the diameter, lymphocytes are classified into: ☼ Small lymphocytes: ► Their percentage in the blood is about 15-20% ► Each lymphocyte is about 6-8 microns in diameter ► It is cytoplasm is scanty and it contains few azurophil granules and many free ribosomes ►The nuclei is small, darkly stained and filling the whole cytoplasm ☻ there are two types of small lymphocytes: A- T-Lymphocytes (75%) B- B-lymphocytes (25%) ►Small T and B lymphocytes are covered by microvilli 78  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ► Their cytoplasm shows many free ribosomes ► It is also contain few mitochondria, few endoplasmic reticulum and pair of centrioles ► Large lymphocytes: ► Their percentage in the blood is about 5-10% ► Each lymphocyte is about 10 to 15 microns in diameter ► Its cytoplasm is abundant and it contains many ribosomes, mitochondria and well- developed Golgi apparatus ► The nucleus is slightly indented and appears pale after staining …………………………………………………. CLASSIFICATION OF SMALL LYMHOCYTES According to the origin and functions, they are classified into □ T-lymphocytes □ B-lymphocytes 1-►T-LYMPHOCYTES: ► They are termed as T-lymphocytes because they are Thymus dependent lymphocytes ► They require the presence of the thymus gland for their development and for their maturation ► They account for most of the circulating lymphocytes ► They have a long life span, they can live for years ► It is originate from mother cells called (colony forming cells) which are present in the Bone Marrow ►The mother cells migrate from the bone marrow to the thymus gland ►They proliferate in the thymus to be changed to T-lymphoblast and then to T-lymphocytes ►Some of them circulating in the blood to be settled in the thymus dependent areas as: the spleen, lymph nodes, and other lymphatic tissue area FUNCTION OF T-LYMPHOCYTES: ► It is responsible for cellular immunity: → If any foreign body or bacteria → T-lymphocyte act as antigens→ which react with the surface receptors of T-lymphocytes → resulting in their sensitization with these antigens. 79  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani So→ If the bacteria and antigens enter to our body again→ the previously sensitized T-lymphocytes will come in contact with these antigens and cause lysis and destruction of these bacteria and antigens. Therefore cellular immunity means cell to cell contact destruction. ► It acts as Killer Cells: The T-lymphocytes which have been sensitized by certain antigens can secrete cytotoxic substances called Lymphokinase which are hormone- like factors. They include: ♣ Interferon which inhibits viral replication ♣ Colony stimulating factor: which stimulates proliferation of B.M CELLS? ♣ Macrophage factor: which can kill certain bacteria as T.B.? ► It is acts as T-Memory Cells: If any specific antigen enters the body, it activates the T-lymphocytes. These activated T-lymphocytes multiply and produce many activated T-lymphocytes. Some of these newly-formed cells remain in the body and are called T-memory cells. ► It is considered as Helper Cells to B-lymphocytes because they can help the B- lymphocytes to be activated by the specific antigens which may enter the body ► It is acts as Macrophage Chemotactic Cells. They activate and stimulate the macrophage (phagocytic cells) to migrate to the sites of infection. ……………………………….. 2-► B-LYMPHOCYTES: ►They are termed as B-lymphocytes because they are Bursa dependent lymphocytes in birds, they develop in the bursa of Fabricus in birds ►It is derived from the primitive stem cells of the bone marrow in mammals ►They have short lifespan (about 3 months) Functions of B-lymphocytes: ►It is responsible for the development of humoral immunity ►They are transformed into plasma cells which secrete many antibodies in the form of gamma globulins which circulate in the blood stream ►The development of humoral immunity takes place as follows: ◙ If any antigen enters the body it is first picked up by the T-lymphocytes which act as helper cells for B-lymphocytes ◙ The antigen is then subsequently delivered from T-lymphocytes to the programmed B-lymphocytes 80  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ◙ In this case the B-lymphocytes enlarge and become activated and then differentiated into plasma blast. ◙ Plasma blasts then differentiate into plasma cells. ◙ Plasma cells can now secrete antibodies that react specifically with the original antigen ►B-lymphocytes acts as B-Memory Cells: The majority of the activated B- lymphocytes differentiated into plasma cells ► But the minority of the activated B-lymphocytes remain in the blood as Memory Cells ►The Memory Cells can produce secondary immune response when they are exposed once again to the same type of antigen The mode of neutrophils functions actionh: ► It is consider as the first line of body defense by Phagocytosis and bacterial-cidal action 81  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani THE BLOOD PLATELETS ☼ Thrombocytes (blood platelets) are small cytoplasmic fragments from megakaryocytes and are found in circulating blood ☼ It is produced from megakaryocytes of bone marrow although the lung has also been mentioned as a site of megakaryocyte development ☼Platelets are not cells; they are small oval or rounded non-nucleated bodies, similar to plates ☼ They are found in mammals. In lower vertebrates they are known as Thrombocytes because they are nucleated bodies. ☼ Their number varies from 200,000 to 400,000 per cubic millimeter ☼ With E/M the cell membrane of the blood platelets are irregular and covered a cell coat formed of glycoprotein ☼ The Hyalomere of platelets contains bundles of microtubules and microfilaments which play an very important role in the contractile function, they can change the shape of platelet during retraction of blood clot ☼ The Chromomere (central area of platelet) contains: ►Alpha granules which are numerous and are considered as lysosomes ►Mitochondria or Beta granule which are few in number and small in size 82  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ► Sydersomes or Delta granules which are rounded vesicles with clear contents ►Very Dense Granules which are rich in serotonin substances, ATP, ADP and Ca ►Glycogen granules which are present in small or large groups ►A system of tubules and vesicles ☼ Life span of platelets is from 5 to 10 days ☼ The role of the thrombocyte in haemostasis is: ►Aggregation and formation of a haemostatic plug ►Thromboplastic activity ►Clot retraction ☼ They clump together and adhere to an injured vessel wall, they release certain active biochemical substances ☼ They release of ADP cause aggregation of additional platelets by a mechanism ☼ Serotonin released by platelets acts as a vasoconstrictor and contributes to the overall haemostatic reaction ☼ The activity of the platelets is directly related to the phospholipids released (platelet factor 3), which is activation of the coagulation sequence ☼ It play an important role in the clot retraction. ☻If whole blood is allowed to clot and is observed, the clot decreased in size and serum is expressed, this phenomenon dependent upon the presence and action of thrombocyte ☻If the blood is deficient in platelet, clot retraction is usually poor ☻Low fibrinogen levels are associated with poor retraction ……………………………………………. FUNCTION OF BLOOD PLATELETS: ◙ Blood Agglutination: platelets adhere together when exposed to a rough surface; they form a white thrombus during agglutination ◙ Blood coagulation: during coagulation, platelets cause deposition of fibrin threads entangling RBCs forming a Red Thrombus ◙ It released serotonin substance which is a vasoconstrictor substance ◙ It causes clot retraction by means of their microfilaments 83  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani CARTILAGE ►Cartilage and bone are connective tissues in which the amorphous intercellular substance is hardened to provide rigidity, support and attachment for tissue ►Cartilage is a dense types of C.T. which is firm, rigid and flexible ►Cartilage support soft tissues. It also provides sliding surfaces for bone at the joints in order to facilitate the movement of the articular surfaces of bone ►cartilage is essential for the growth of long bones before and after birth ►STRUCTERS OF CARTILAGE : ►It is formed of cartilage cells and C.T. fibers which are embedded in a special type of rubbery matrix ►1- Cartilage cells are two types a) Young chondrocytes (Chondroblasts): 84  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ►They are flat basophilic cells with oval nuclei ►They are present at the periphery of the cartilage under the perichondrium OR in the centre during growth of cartilage b) Mature chondrocytes: ►Which are special cells. They present in the spaces called (lacunae) which surrounded by capsules formed of condensed matrix ►The chondrocytes can divide, thus they may be present singly or in groups (of 2, 4 or 8 cells) ►When they many chondrocytes are present in a single lacuna, they form a (cell nest) ►Their cytoplasm is basophilic, rich in glycogen, fat and phosphate enzymes ►Each cell contains a large nucleus with one or two nuclei ►2- The Connective Tissue Fibers ►They are present in the cartilage which may be collagenous or elastic fibers ►They are similar to the fibers of the C.T. proper ►3- Intercellular Matrix ►The matrix or ground substance is rubbery in consistency ►It is formed of a viscous hydrophilic glycol-protein called cartilage (Proteoglycan) which is formed by the chondrocytes, there is also another protein in the matrix called (Chondrocalcin) ►The matrix appears homogenous although it contains fine collagenous fibres. ►The matrix can be stained blue basic dyes and can also be stained with metachromic stains because it is very rich in chondroitin sulphuric acid TYPES OF CARTILAGE ►The cartilage cells and the C.T. fibers are embedded in a rubbery matrix in order to form the following three types of cartilages: 1- Hyaline cartilage (it appears glassy) 2- Elastic fibro-cartilage (contains elastic fibers) 3- White fibro-cartilage (contains white collagenous bundles) HYALINE CARTILAGE ► ►It is the commonest type of cartilage, it appears when fresh, translucent and pale blue in colour. Therefore it is called hyaline 85  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ►The matrix is poor in blood supply. The blood vessels which appear in the matrix pass through it on their way to supply other tissues ►It is covered by a vascular membrane or (perichondrium), which is not present over the cartilage which covers the articular of joints ►The perichondrium is formed of: - Outer Fibrous Layer: of collagenous bundles, rich in B.V. - Inner Chondorgenic Layer: formed of chondroblasts which can be changed into chondrocytes. These chondroblasts can divide and can secrete new matrix, this will result in growth of cartilage at its periphery ►Functions of perichondrium: ►It supplies the cartilage with blood and nourishments ►Its chondroblasts can secrete matrix during the growth of cartilage ►It provides an attachment for the muscles Two types of cartilage cells: a) Young chondrocytes or chondroblasts: - They are flat cells surrounded by spaces or lacunae. - They have flat nuclei and basophilic cytoplasm - They are present as single cells under the perichondrium - With growth of cartilage, chondroblasts become deeply buried in the matrix and are transformed into mature (chondrocytes) b) Mature chondrocytes: - They are spherical cells with rounded nuclei and basophilic cytoplasm rich in phosphatase enzyme - Each cell is present in a space called secondary lacuna - During growth, chondrocytes can divide giving rise to 2 or 4 or 8 chondrocytes, each new one is surrounded by its secondary lacuna - These new daughter cells are grouped in 2 or 4 or 8 chondrocytes - These groups are surrounded by a common apace called primary lacuna - These of chondrocytes which are surrounded by a common primary lacuna and by a common capsule formed by the condensed matrix are called Cell Nests ►Sites of hyaline cartilage: ►Costal cartilage: which are present in the thoracic cage 86  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ►Cartilage of respiratory passages as in: nose, trachea, bronchi, thyroid and cricoids cartilages of the larynx ►Long bones in the skeleton of foetus ►Articular surfaces of joints (cartilage here is not covered with perichondrium) ►YELOW ELASTIC FIBRO-CARTILAGE ►This type of cartilage is similar in its structure to hyaline BUT: ♣ The matrix is rich in elastic fibers which surround the cartilage cells. The elastic fibers are continuous with those of the perichondrium ♣ This cartilage is flexible and is yellow in colour due to presence of elastic fibers The Chief Distribution Of Elastic Cartilage In Human Body: ►Ear pinna, External auditory tube and Eustachian tube ►Some laryngeal cartilage as : corniculate and cuneiform cartilage. The epiglottis and the lip of the arytenoids cartilage contain elastic fibro-cartilage ►WHITE COLLAGENOUS FIBRO-CARTILAGE ►It is similar to hyaline cartilage, it is rich in dense white C.T. and it has the following characteristics: ♣ It is formed of chondrocytes similar to those of hyaline cartilage ♣ The cartilage cells are arranged in rows or in columns ♣ The cartilage cells are present in a single form or in groups of two cells which are surrounded by clear lacunae and by capsules ♣ The rows of cartilage cells are separated by acidophilic collagenous bundles ♣ The white fibro cartilage is not covered by perichondrium but it is surrounded at its periphery by dense fibrous tissue rich in blood capillaries from which it is nourished ►Sites of White Fibro-Cartilage In The Body: ♣ Present in the intrervertebral discs ♣ In the semilunar cartilage of knee joints ♣ In the symphysis pubis, acetabulum and in the glenoid cavity ♣ In The discs between steno-clavicular and mandibular joints ♣ In the terminal parts of the muscle tendons and in the tendon grooves ►Function of Cartilage ♣ Cartilage helps in maintaining the patency of respiratory passages 87  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ♣ Cartilage and bone form the skeleton of the body ♣ Cartilage forms a smooth firm surface for the articular surfaces of joints ►CLINICAL NOTE: ►In a condition of prolapsed intrervertebral disc the soft nucleus pulposus is herniated through the annulus fibrosis. ►This causes inflammation that is very painful and can compress the roots of the spinal nerves at the level involved ►Nutrition Of Cartilage: ♣ Cartilage, like epithelial tissue, lacks a capillary blood supply of its own, (i.e. it is a vascular C.T. ♣ Nutrients and oxygen reach the cells from perichondrium (an outer vascular layer that surrounds cartilage) by diffusion through the matrix ►GROWTH OF CARTILAGE 1- Appositional growth: ♣ It is growth of the cartilage by adding new layers from "outside" ♣ It is due to mitosis of chondroblasts in perichondrium ♣ They secrete new matrix to the surface and form chondrocytes inside lacunae 2- Interstitial growth: ♣ It is growth of the cartilage from "inside" ♣ It occurs as the result of division of young chondrocytes within the cartilage ♣ Chondrocytes secrete more matrix and form cell nests 88  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani THE BONE ►Bone is a calcified osteoid tissue. It is rich in blood supply. It has a solid matrix ►It is strong, hard and rigid specialized form of C.T. ►FUNCTIONS OF BONE ♣ It Forms the skeleton of the body ♣ It protects the vital organs (as brain, heart, lungs and bone marrow) ♣ It acts as a reservoir for calcium ►Shape: ♣ The bone may be Long as the bone of limbs ♣ It may be short as the bone of hand and foot ♣ Irregular bone as vertebrae and Flat bones like skull, scapula, sternum. And ribs ►TYPES OF BONE ♣ Compact or ivory: solid bone which is present in : the shafts of long bone and in the outer thin layer of the spongy bone in old age ♣ Spongy or cancellous: bone which is present in : the epiphysis of long bone, ribs, vertebrae, flat bones as skull, scapula, sternum, and sacrum ►CONSTITUENTS OF BONE ♣ Bone Matrix : which is a calcified tissue ♣ bone Cells: which are (Osteogenic Cells, Osteoblasts, Osteocytes and Osteoclasts) ♣ Periosteum: which is the covering layer of bone from outside ♣ Endosteum: which is the inner layer of bone from inside ►THE BONE MATRIX ♣ The bone matrix is formed of bone lamellae which are formed of layers of calcified osteoid tissue. These lamellae are arranged in different layers ►The Chemical Structure Of Bone Matrix ♣ Organic substances: - They constitute about 30% and are mainly protein which is present in the form of ( bone collagen, glycoprotein and osteo-mucoid) ♣ Inorganic Substances: - They constituent about 45% and are mainly calcium phosphates, carbonates, and citrates. They also contain sodium, magnesium and iron ♣ Water: about 25% 89  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ►CALCIFICATION OF BONE MATRIX ♣ The osteoblast cells: - Which are responsible for the synthesis of the organic components of the bone matrix,(collagen and glycoprotein) - They also secrete phosphatase enzyme which causes precipitation of calcium phosphate in the matrix - Osteoblasts secrete also pyrophosphatase enzyme which inhibits the pyrophosphate substances - These pyrophosphate substances retard the processes of calcification ►TYPES OF BONE CELLS ►There are Four Types of Bone Cells ♣ Osteogenic Cells: There are primitive cells which can differentiate into osteoblast cells ♣ Osteoblast Cells: They are responsible for synthesis and calcification of bone matrix ♣ Osteocytes Cells: They are the actual mature bone cell ♣ Osteoclast cells: They are responsible for bone resorption. They are bone-eating cells ♣ Osteogenic Cells 90  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ♣ They are primitive cells, they develop from undifferentiated cells which are called (pericytes). These pericytes are present around blood capillaries ♣ They are mainly present in the Periosteum, in the bone marrow cavities, in the cavities of spongy bone in the (Haversian canals of compact bone) ♣ They are spindle-shaped cells. They have pale cytoplasm and flat nuclei ♣ They differentiate into bone-forming cells which are the osteoblast cells ♣ They are very active during growth of young bone and during healing of fractured bone in order to give more osteoblast cells to form new bone ♣ Osteoblast Cells: ♣ Origin: They arise from the Osteogenic cells: ♣ With (L/M): They are oval cells with eccentric rounded nuclei ♣ The cell membrane has few cytoplasmic processes, and its deeply basophilic ♣ With (E/M): The cytoplasm is rich in RNA, rough endoplasmic reticulum, Golgi minerals in the osteoid tissue during bone development 2- Pyrophosphatase enzymes: which inhibit the action of pyrophosphate substances (these pyrophosphate substances retard the processes of calcification of development bone) vesicles and mitochondria ♣ They are very rich in these enzymes: 1- Alkaline phosphatase enzymes: which facilitate deposition of calcium and ♣ Sites: They are present side by side at the surface of bone tissue (e.g. in the periosteum, Endosteum and lining the bone marrow cavities in spongy bone) ♣ FUNCTION: &- They synthesize the organic component of bone matrix ( collagen, glycoprotein) to form the osteoid non-calcified pre-bone tissue &- The phosphatase and pyrophosphatase enzymes of the osteoblasts are concerned with calcification of bone &- Osteoblasts change into Osteocytes when they are surrounded by lacunae and by calcified matrix ♣ THE OSTEOCYTE ♣ It is a mature flat bone cell present inside lacunae and is surrounded by calcified matrix ♣ Its cytoplasm is slightly basophilic and it contains phosphatase enzymes but the cell cannot divide ♣ The nucleus is flat with condensed chromatin 91  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ♣ Each cell is surrounded by a space or lacuna from which ( canaliculi ) arise connecting Osteocytes together ♣ The tissue fluids usually pass through these canaliculi ♣ With (E/M): - Osteocytes contain few rough endoplasmic reticulum and ribosomes - Many cytoplasmic processes arise from Osteocytes, through these processes they connected with each other, and the electrolytes pass freely from one cell to another ♣ Origin: - Osteocytes are considered as mature osteoblasts surrounded by calcified matrix ♣ FUNCTION: @- They are involved in the maintenance of the bone matrix @- They can release calcium ions from bone matrix to the circulating blood plasma when calcium demands increase ♣ THE OSTEOCLAST CELL ►Origin: They are formed as a result of fusion of multiple blood monocytes ♣ With (L/M): * It is a large cell with irregular striated cell membrane * The cytoplasm is acidophilic and has a foamy appearance * Each cell contains from 6 to 12 nuclei ♣ With (E/M): * It shows a brush border formed of many finger like processes projecting from the cell membrane * The oteoclasts with other cells are essential in bone resorption during the process of ossification. They are rich in lysosomes and in acid phosphatase enzyme * It may secrete osteolytic enzymes. They may liberate toxic substances which may result in solution of calcium salts around themselves ♣ Sites: * They are present on surfaces of bone where bone resorption is taking place as in bone marrow cavities and in the Endosteum of bone ♣ FUNCTION: = They are concerned in bone resorption during ossification = They secrete collagenase and other proteolytic enzymes that dissolve the organic component of the bone matrix during remodeling of bone 92  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani = They also liberate carbon dioxide which plays an important role in decalcification of bone matrix = They are also actively concerned in elimination of debris during bone ossification ♣♣ MICROSCOPIC STRUCTURE OF COMPACT BONE ♣ The shafts of adult long bones are formed of bone layers or lamellae which composed of the following structures: ►Haversian system: or osteons ►Interstitial systems or lamellae between the Haversian systems ►Outer and Inner circumferential lamellae: which are present under the periosteum and near to the Endosteum of the bone ►Periosteum and Endosteum: The external surface of bone is covered by the periosteum and its internal surface is lined by the Endosteum ►SPONGY OR CANCELLOUS BONE ♣ The long and short bones are formed externally of compact bone, but their endosteums are irregular due to presence of spongy bone ♣ Cancellous bone looks spongy, with many vascular channels ♣ It is formed of irregular bars or plates of bone separating between them multiple bone marrow cavities which are rich in blood vessels ♣ The multiple bone marrow cavities are filled with active red bone marrow ♣ Sites : It is present in the centre of ribs, vertebrae and the centre of flat bones as : ( skull, scapula, sternum and ilium). ♣ It is present also in the centre of the epiphysis of long bones DIFFERENCES BETWEEN CARTILAGE AND BONE Bone Cartilage 1- It is a solid inflexible tissue 1- It is a rigid flexible tissue 2- There are 2 types of bone: compact 2- There are 3 types of cartilage: Hyaline, and spongy (cancellous) elastic and white fibro-cartilage 93  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 3- It has a solid matrix rich in calcium 3- It has a rigid matrix rich in chondroitin sulphuric acid and glycoprotein 4- Bone cells (Osteocytes) are present 4- Cartilage cells (chondrocytes) are singly inside lacunae present singly or in groups inside lacunae 5- Osteocytes intercommunicate by their 5- Chondrocytes do not communicate canaliculi arising from their lacunae because there are no canaliculi 6- Bone is vascular tissue, its Haversian 6-Cartilage is a non-vascular tissue but its canals, Volkmann's canals and the chondrocytes receive nourishment from canaliculi carry blood to all parts of bone B.V. of the perichondrium 7- Osteocytes cannot divide 7- Chondrocytes can divide OSSIFICATION [Development of Bone} ►Ossification is the process of formation of bone which leads to its growth ►There are two methods for bone development or bone ossification: 1- Intramembranous 2- Intracartilagenous ♣ In Intramembranous ossification, the bones develop directly from the embryonic mesenchyme ♣ In the Intracartilagenous ossification, the bones are first modeled in the form of cartilage which is then destroyed and replaced by bony tissue ►Mechanism of ossification ♣ Bone development occurs as a result of the following two processes: 1- Bone formation by osteoblasts: The Osteogenic cells in the primitive embryonic tissue change into osteoblasts. These osteoblasts can form osteoid tissue in the form of irregular trabeculae of bone - When the osteoblasts are completely surrounded by the bone matrix, they are changed into Osteocytes 2- Bone Resorption by Osteoclasts: This process occurs during growth and remodeling of the formed bones (1) THE INTRAMEMBRANOUS OSSIFICATION 94  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ♣ It occurs in: Flat bone of the face and skull and also in certain bones as the clavicle. The site of the future bone is occupied with a mesenchymal membrane which is formed of soft matrix, blood capillaries and mesenchymal cells. This membrane is transformed into spongy bone (2) THE INTRACARTILAGENOUS OSSIFICATION ♣ This type of ossification occurs in the long bones which were originally formed of hyaline cartilage in the foetus.These cartilage models will be replaced by bone. ♣ Cartilage is never changed into bone. It is only gradually replaced by primitive mesenchymal tissue. The mesenchymal tissue can be changed into bone. ♣ Ossification starts as primary centre of ossification in the middle part of the long bone (Diaphysis). Then secondary centers of ossification appear at both ends of long bone (Epiphysis). ♣ The epiphyseal disc and the part of the Diaphysis near to it are called the Growing Zone; If we examine a longitudinal section in the growing end of a long bone, we can demonstrate the different stages of intracartilagenous ossification MUSCULAR TISSUE ♣ There are (three) types of muscles: 1- Smooth 2- Skeletal 3- Cardiac ♣ General characteristics of Muscles: ►The structural and functional units of muscles are formed of special elongated cells known as muscle fibers ►The cell membrane of these muscle fibers is known as (sarcolemma) ►The cytoplasm of these muscle fibers is known as (sarcoplasm) ►The sarcolemma contains all the cell organoids and cell inclusion ►The cytoplasm is rich in : fat, glycogen, pigments, mitochondria, and myofibrils which are responsible for muscle contractions ►The muscle fibers may have transverse striation as the skeletal and cardiac muscle fibers, or they may show no striations as the plain or smooth muscles 1- SMOOTH MUSCLES ►Characteristics of Smooth or plain Muscles: ♣ Smooth muscles are: Pale in colour and acidophilic in staining ♣It may be arranged singly as in dermis of skin. Or in layers as in the wall of the viscera (e.g. stomach). 95  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ♣ They are spindle-shaped cells with acidophilic granular sarcoplasm (rich in mitochondria and glycogen granules) and poor in granular endoplasmic reticulum ♣ The nucleus is single and central in position, and it may rod-shaped or oval in shape ♣ The cytoplasm contains longitudinal myofibrils, they are three types: Actin, Myocin and Intermediate myofibrils, and they are scattered in the cytoplasm overlapping each other and showing no striations ♣ The length of a smooth muscle ranges from: 30 microns as in the wall of Blood Vessels; up to 500 microns as in pregnant uterus. The diameter of each smooth muscle ranges from 4 to 10 microns. ♣ All smooth muscles originate from the mesoderm except the muscles of the (iris and the myoepithelial cells around the acini of certain glands) which are ectodermal in origin ♣ Smooth muscles are involuntary in action. They are innervated with sympathetic and parasympathetic nerves ♣ The number and size of smooth muscle fibers may increase during life as in (pregnant uterus and in certain arteries) ♣ Regeneration of smooth muscles: Formation of new smooth muscles in the uterus or in wounds takes place from the primitive cells which are present around the small capillaries and venules and are called (Pericytes) ♣ All smooth muscles are involuntary except the (ciliary muscles of the eye) and special muscles in the (urinary bladder) which are partially voluntary ♣ SITES OF SMOOTH MUSCLES &- Digestive system: Muscles in the wall of the lower third of Oesophagus, the wall of stomach, intestine, gall bladder and wall of salivary and pancreatic ducts &- Respiratory system: Trachea, bronchi and bronchioles &- Urinary system: Ureter, urinary bladder and urethra &- Male genital system: Epididymis, vas deferens, prostate and penis &- Female " " : Fallopian tube, uterus and vagina &- All the media (middle part) of blood and lymph vessels &- Capsules of glands and spleen, ciliary muscles and iris of the eye and also in the arrector pili muscles of the (hairy skin) 96  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani 2- SKELETAL MUSCLES ♣ Skeletal muscles are attached to the skeleton. ♣ They are present also in the diaphragm, tongue, muscles of the face, eye, pharynx and upper third of Oesophagus ♣ Skeletal muscles are Voluntary muscles except those in: the upper third of Oesophagus, some muscles of the pharynx and the cremasteric muscles of the spermatic cord. ☻CONNECTIVE TISSUE OF THE MUSCLES ♣ The cutting section in any skeletal muscle show the presence of C.T. fascia or the epimysium around the whole muscle. ♣ The perimysium in the C.T septa between the muscle bundles, while each muscle fiber is surrounded by a C.T endomysium ♣ In the C.T of the muscles: B.V. nerves and lymph vessels are present. C.T. also firmly attach the muscle bundles together and attach the whole muscle with its tendon ☼ CHARACTERISTICS OF SKELETAL MUSCLES: ►They are attached to bone forming the muscles of limbs, abdomen, head, neck, face, eye, diaphragm and tongue ►They are formed of striated muscle fibers. Each muscle fiber is a single cell which varies in length from 1 mm up to 40 mm ►The muscle fibers do not branch except in the tongue and face muscle ►Each muscle fiber is a multinucleated cell, it has many oval nuclei under its cell membrane, the cell membrane of the muscle fiber is known as sarcolemma ►The cytoplasm of the muscle fiber is known as sarcoplasm. This sarcoplasm is an acidophilic colloidal protein substance rich in glycogen and myoglobin ►The myoglobin is formed of pigmented protein which may be present in large amounts in certain muscles ► The sarcoplasm (cytoplasm) contains many ribosomes, many mitochondria and many smooth endoplasmic reticulum which is called Sarcoplasmic Reticulum ►The sarcoplasm contains also longitudinal fibrils known as (Myofibrils) or (Sarcostyles) ☺THE MYOFIBRILS OF SKELETAL MUSCLES 97  Tissues of the body…………………………………………………………………………………………….Prof-Tabet El-hani ►They are the specific cell organoids present in muscle cells ►They are the contractile threads which are arranged longitudinally in the sarcoplasm of each muscle fiber ►The arrangement of it near each other shows transverse striation ►The transverse striation due to presence of alternating dark and light bands on each myofibril ►each dark band of one myofibril is present beside the dark band of the adjacent myofibril. These arrangements of dark and light bands give the muscle fibre the appearance of transverse striation ►Each dark band is further subdivided by a pale are in its centre called Hensen's zone or H-Disc ►The area of the muscle fibre enclosed between two Z-Discs is called sarcomere ►The sarcomere are the functional contractile units of the muscle fibre ►The sarcomere of each muscle fibre contract and relax as one unit. ►CONTRACTION OF MUSCLE ►The muscle contracts when a nerve impulse arrives to it ►The energy needed for its contraction comes the transformation of ATP into ADP + energy ►The energy causes the gliding of the thin filaments over the thick filaments ►The thin filaments thus slide towards the middle of the of the sarcomere, this will result in pulling the two Z-lines behind them ►The gliding of the thin filaments over the thick filaments goes on until the fine filaments become restricted to the area of dark band ►Thus, the H-Zone disappear during muscular contractions because during contraction, the H-Zone will contain both types of filaments ►While, during relaxation of muscles, the H-Zone contains only the thick filaments ☼ THE CARDIAC MUSCLE ►The heart is formed of two thin atria and two thick ventricles ►The cardiac muscle forms the main wall of the heart and is known as (myocardium) ►T