Histology Of Cartilage PDF

Dr. Kandeel Dr. Kandeel Module 103 Cartilage Dr. Kandeel - specialized type of C.T in which matrix is rubbery? → to bear mechanical stress. 1) Being a type of C.T: a- cartilage arises from Undifferentiated mesen...

Dr. Kandeel Dr. Kandeel Module 103 Cartilage Dr. Kandeel - specialized type of C.T in which matrix is rubbery? → to bear mechanical stress. 1) Being a type of C.T: a- cartilage arises from Undifferentiated mesenchymal cells (UMCs). b- resembles C.T. proper: widely separated cells with amount of (matrix). c- matrix is rubbery (firm) but flexible. 2) Avascular: diffusion of O2 & nutrients from: a- surrounding C.T (Perichondrium) b- synovial fluid in joint. 3) It has no lymph vessels or nerves. a- Supports soft tissues with some flexibility b- tissue attachment & weight bearing, shock absorbing c- Keeps airway patent. d- Smooth surface for easy movement of bones. e- Development and growth of bones Module 103 Dr. Kandeel Cartilage The Cells: chondroblasts and chondrocytes. The Matrix: a- Ground substance: abundant, firm & rubbery. b- Fibers: collagen & elastic embedded in ground substance three types of cartilage based on: a- amount of ground substance b- type of fibers - most common type, translucent, with glassy appearance - the typical structure of cartilage. 1 - Fetal skeleton 2- Articular surface of bones 3- Costal cartilage 4- Epiphyseal plate 5- Upper Respiratory passages (nose, larynx, trachea & bronchi). Module 103 Cartilage Dr. Kandeel Capsule-like, surrounds hyaline cartilage except at articular surface of joints 1- Outer fibrous layer: white fibrous C.T: a. fibroblasts that secrete collagen type I, - blast - deep... b. rich in blood vessel, nerve extoplasm cartilage - 2- Inner chondrogenic (cellular): chondroblasts ↳ basophilic Fundes Kopen in Nutrition of non-vascular cartilage (by diffusion). Provides attachment for muscles. Formation of new cartilage cells during growth. Module 103 Dr. Kandeel Cartilage - Collagen fibers (type II). - can't be seen by LM: homogenous, transparent, this is because: a- They are very thin. b- They have the same refractive index as the surrounding matrix. - They can be seen after digestion of the matrix by enzymes. : - produced by chondroblasts and chondrocytes. - matrix consists of: proteoglycans, glycoproteins and water - It is rubbery, homogenous, transparent - markedly basophilic (sulfated GAGs= Chondroitin Sulphate). - stained metachromatic: (with toluidine blue) - Ground substance + fibers forming Matrix Module 103 Cartilage Dr. Kandeel - UMCs which proliferate, transformed into develop from chondroblasts chondroblasts - Surface of cartilage - Young cells are Superficial - inner aspect of - Older cells become deeper perichondrium in the matrix. - small, oval, parallel to surface. - Flat to oval or spindle cell - rounded cell with pale - deep basophilic cytoplasm basophilic - Flat or oval pale nucleus, - rounded dark central nucleus. with prominent nucleolus. - cells singly in lacunae - Can divide - deeper in the matrix, with dark, round nucleus - rounded or triangular cell - pale cytoplasm - rich in fat & glycogen dissolve during preparation - divide giving clusters of cells formed of 2 or 4, up to 8 cells * (isogenous groups or cell nest) in lacunae surrounded with darkly stained capsule - During tissue preparation: chondrocyte shrink, so lacunae appear as empty spaces. Module 103 Dr. Kandeel Cartilage - protein forming cells (less - protein forming cells: prominent than chondroblast) euchromatic, ribosomes, rER, - old chondrocyte have large lipid Golgi & many mitochondria). droplets and glycogen - Formation of matrix - Maintain matrix by continuous - change into chondrocytes. secretion of new matrix - Formation of collagen II - Interstitial Growth: growth of - Cartilage growth from cartilage from inside by division outside of young chondrocytes which (appositional growth). produce matrix around them. Module 103 Cartilage Dr. Kandeel ….. yellow in fresh state tough type: important in bone to bone * opaque & flexible attachment. Covered by perichondrium. intermediate characters between has the same structure of hyaline cartilage and dense regular hyaline cartilage, but: white fibrous C.T. a- large number of branching Is not surrounded with perichondrium. elastic fibers formed of collagen fibers (type I) b- Few collagen fibers (type II) present in parallel thick bundles. Chondrocytes form small cell Cartilage cells inside lacunae are nests (mostly 2 cell called present in rows between collagen isogenous groups). bundles embedded in very scanty matrix around them. - very flexible, recovers its shape - strong and tough type that can resist after being deformed. great stretch - attaches bone to bone with limited mobility. Module 103 Dr. Kandeel Cartilage --- Ear pinna. hip, shoulder joints. Eustachian tube. Intervertebral disc. Epiglottis ,Some laryngeal Mandibular joint cartilages Symphysis pubis. External auditory canal Sternoclavicular joint. Semilunar cartilages of knee joints. Module 103 Cartilage Dr. Kandeel - present between bodies of two adjacent vertebrae 1- outer fibrous ring (annulus fibrosus): white fibrocartilage (collagen type I) 2- inner soft jelly-like (nucleus pulposus): collagen type II - Herniation of the nucleus pulposus from the annulus fibrosus called disc prolapse, can compress nerve roots causing severe pain. Module 103 Dr. Kandeel Dr. Kandeel Module 103 Bone Dr. Kandeel - highly vascular & hard type of connective tissue as it has calcified matrix 1- body support as it forms bony skeleton 2- protection of vital organs as brain & bone marrow 3- minerals store mainly calcium store a- matrix: Ground substance, fibers b- Bone coverings: (periosteum & endosteum): outer, inner covering for bone surface c- bone cells: osteogenic cells, osteoblasts, osteocytes and osteoclasts - formed of type I collagen fibers that arranged as thick bundles & ground substance (glycosaminoglycans & glycoproteins) - formed of calcium salts in form of calcium phosphate & carbonate - present on surface of collagen bundles & within ground substance cause hardness of bone - Bone matrix: arranged in the form of lamellae of calcified collagen bundles embedded in calcified ground substance Module 103 Dr. Kandeel Bone Definition: layer of connective tissue, covers outer surface of bone Structure: two layers: 1- outer fibrous layer: a. collagen fibers (type I) b. fibroblasts & blood capillaries 2- inner osteogenic layer: a. formed of osteogenic cells b. in case of growth & fracture: osteogenic cells multiply : 1. Collagen fibers: a. protection of bone b. gives attachment form muscles 2. Blood capillaries: nutrition for bone 3. osteogenic cells differentiate to osteoblast which: a. form bone matrix b. change to osteocytes (Appositional growth) Definition: a. delicate layer of connective tissue b. contains a single layer of osteogenic cells Functions: a. protection of bone surface b. bone growth by adding from inside Module 103 Bone Dr. Kandeel ------ UMC & pericytes - arise from osteogenic cells inner layer of periosteum, - under periosteum single layer endosteum - under endosteum -Flat cells with flat nuclei - oval cells with few processes & -pale basophilic cytoplasm eccentric nuclei. - darkly basophilic with negative golgi image - rich in alkaline phosphatase - show free ribosomes - protein forming cells: rich in rER, mitochondria, well developed golgi - divide & give rise to - secrete organic part of matrix osteobalsts called “osteoid” - numerous in case of fracture - they calcify matrix by alkaline & young age phosphatase enzyme which helps - give chondroblasts in area of deposition of calcium poor vasculature - when surrounded by calcified matrix, they change into imprisoned cells called osteocytes - 10-20% osteoblasts differentiate into osteocytes in lacunae, - some flatten and cover the matrix as bone lining cells - majority undergo apoptosis Module 103 Dr. Kandeel Bone fusion of mononuclear Osteoblasts hemopoietic progenitor - present singly in small bony lacunae - on the surface of bone near bone - lacunae communicate through marrow within a cavity called canaliculi which connect them Howship,s lacuna together, for exchange of nutrition & waste products - as matrix is calcified & no tissue fluid can pass through it oval cells fine processes large irregular cells having oval nuclei, lightly basophilic brush border contains alkaline phosphatase multinucleated cells (6-12) foamy acidophilic cytoplasm - processes extend within canaliculi, -ruffled surface which shows connected by gap junctions microvilli - less ribosomes, rER than osteoblast, -rich in lysosomes, mito, golgi & contain golgi & mitochondria shows multiple vesicles Module 103 Bone Dr. Kandeel Osteocytes Osteoclasts - formation the organic part of the a- Bone resorption which occurs in matrix two steps :- - calcification of the matrix by 1- osteoclasts contain carbonic anhydrase which induces reaction deposition of calcium salts (H2O +CO2 → HCO3- +H+) - important for viability of the Releasing H+ through ruffled border matrix ,acidifying medium and helping to Function dissolve calcium salts - only one osteocyte is 2- osteoclasts secrete lysosomal present within lacunae unlike proteolytic enzymes (osteolytic chondrocytes as osteocytes cannot enzymes) which cause lysis of organic divide, No interstitial growth in part of matrix bone b- Bone remodeling - during ossification process are phagocytic cells, contain: 1- exocytotic vesicles transfer lysosomal enzymes to Howship lacunae 2- endocytotic vesicles:- a. transfer degraded bone products to interior of cell b. contents of endocytotic vesicles are discharged by exocytosis from the basolateral aspect of osteoclasts - common bone diseases, characterized by loss of normal bone density that increases risk of bone fracture. - it is caused by increased bone resorption over bone formation Module 103 Dr. Kandeel Bone - A balance between osteoblast and osteoclast activity is necessary for a stable calcium level in blood. - osteoclast activity is hormonally regulated ,stimulated by parathyroid hormones and inhibited by calcitonin from C-cells of the thyroid gland - calcitonin is given in the treatment of patients with osteoporosis - Being a highly vascular structure: a. bone repair is faster than that of the cartilage b. This is referred to degranulation of platelets from the blood clot formed around fracture ends of bones. c. Cytokines released from this degranulation initiate acute inflammatory response to start healing process Howship's lacuna, non-bony Bone marrow surfaces 50 – 70 µm 150 µm Basophilic Foamy acidophilic Single, multilobed Multinucleated Form platelets Bone resorption Module 103 Bone Dr. Kandeel 1- Decalcification method: a- calcium is removed by mineral acids as nitric acid 10% b- bone becomes soft & sections can be cut and stained c- decalcified bone sections demonstrate the bone cells and soft tissue 2- Grinding method: a- bone is left to dry in air b- small pieces of the bone are cut by a saw c- bone is thinned by grinding by using carborandum wheel d- ground bone sections are unstained sections which only show: bone lamellae, the lacunae, canaliculi (no cells) & Volkmann canal grinding method is not used for sections of spongy bone I- Anatomical classification: (according to shape): 1- long bones 2- short bones 3- flatbones 4- irregular bones II- Histological classification (according to structure): A- compact bone B- spongy bone Module 103 Dr. Kandeel Bone a. shaft of long bones b. cover the surface of spongy bone 1- periosteum: - covers the outer surface of bone 2- External ,circumferential Lamellae: - found under the periosteum - formed of osteocytes within lacunae between lamellae of calcified collagen bundles 3- Haversian system (osteon): - structural units of compact bone - cylindrical, formed of central canal (Haversian canal) - blood vessels & nerves embedded in loose C.T. - surrounded by 5-20 of concentrically lamellae - osteocytes within lacunae Module 103 Bone Dr. Kandeel Volkmann's canal: traverse or oblique canals that a. connect haversian canals together b. connect haversian with periosteum c. connect haversian with bone marrow 4- Interstitial Lamellae: a. irregular bony lamellae b. osteocytes in lacunae between Haversian lamellae 5- Internal circumferential lamellae: surround bone marrow cavity 6- Endosteum: lines bone marrow cavity ▪ calcified collagen fibers that arise from tendons or ligaments at site of muscle attachment ▪ they perforate periosteum to be attached to external lamellae ▪ become continuous with collagen fibers of matrix ▪ they fix the tendons into the bone Module 103 Dr. Kandeel Bone - flat bones, short & irregular bones, epiphysis of long bones - irregular branching & anastomosing bony trabeculae enclosing irregular bone marrow cavities - Each trabeculum : formed of irregularly bony lamellae & osteocytes - No haversian system, surface is covered by periosteum - bone marrow cavities are lined by endosteum Module 103 Bone Dr. Kandeel - Bones of the body are formed by one of two methods: I-Intra membranous ossification II-Intra cartilagenous ossification Occurs in flat bones: - starts by mesenchymal C.T membrane, ends by formation of spongy bone 1- Mesenchymal C.T membrane is - Formed of UMCs, fibers, blood Vessels UMCs: this area is called ossification center (O.CS) 2- UMCs differentiate into osteogenic cells then into osteoblasts - Osteoblasts lay down osteoid that calcify & some osteoblast will be imprisoned in lacuna, become osteocytes. 3- Osteoblast continue to produce bony matrix, trabeculae thicken, branch, anastomose forming spongy bone - Spaces enclosed by bone trabeculae become occupied by bone marrow cells 4-At either side of central spongy bone: layer of compact bone are formed Module 103 Dr. Kandeel Bone Module 103 Bone Dr. Kandeel Module 103 Dr. Kandeel Bone - Replacement of cartilage model by compact bone or spongy bone - it occurs in long, short & irregular bones as follows: 1- primary ossification center: - occurs in middle of the diaphysis of the cartilage model - as result of increased vasculature: chondrogenic change into osteogenic which differentiate into osteoblasts - Now perichondrium is changed to periosteum - osteoblasts form layer of bone under periosteum called periosteal bone collar - chondrocytes increases in size and deposit calcium. - calcification of cartilage matrix will lead to death of chondrocytes leaving irregular cavities. - osteoclasts from holes in bone collar so a vascular core formed of U.M.C & blood vessels invade the irregular cavities - U.M.C around blood vessels change into osteogenic cells which differentiate to osteoblasts - osteoblasts deposit bone matrix forming irregular bony trabeculae (spongy bone) - osteoclasts change the irregular bone marrow cavities into one regular bone marrow cavity - bony lamellae become regularly & concentrically arranged forming haversian system & compact bone Module 103 Bone Dr. Kandeel 2- Secondary ossification center - present in the epiphysis - steps are similar to that occurring in the primary center until the cartilage is replaced by spongy bone 3- changes at the epiphyseal cartilage - Zone of resting hyaline cartilage: formed of cartilage cells - proliferative zone: cartilage cells increase in number & become arranged in parallel rows - zone of hypertrophy: cells increase in size as a result of accumulation of glycogen & alkaline phosphatase enzyme - zone of calcification: chondrocytes deposit calcium in the surrounding matrix - zone of invasion: vascular bud formed of blood capillaries & U.M.C. enters through holes formed by osteoclasts in the periosteal collar - zone of ossification: U.M.C, pericytes change into osteogenic cells which differentiate to osteoblasts that deposit matrix & form irregular trabeculae of spongy bone - Remodeling stage: resorption of bone from certain areas by osteoclasts ,results in a single bone marrow cavity - stage of compact bone formation: Haversian system develops & only one central bone marrow cavity Module 103 Dr. Kandeel Dr. Kandeel Module 103 Muscle tissue Dr. Kandeel - Structural and functional units - specialized elongated cells, called muscle fibers - containing contractile filaments (thin actin and thick myosin). - cell membrane is called sarcolemma, cytoplasm is called sarcoplasm - smooth endoplasmic reticulum is called sarcoplasmic reticulum. - acidophilic: as it is rich in organelles as mitochondria, sER Mesodermal: Undifferentiated mesenchymal cells differentiate into myoblasts. Myoblasts are embryonic progenitor cells that differentiate into myocytes. Myocytes (muscle cells): form all types of muscle tissue. - Classified according to shape and functions of their cells into: 1. Skeletal muscle. 2. Cardiac muscle. 3. Smooth muscle Module 103 Dr. Kandeel Muscle tissue attached to skeleton, except: Face, tongue. Pharynx & upper 1/3 of esophagus Diaphragm. Cremasteric muscles. a) Epimysium: - Dense C.T that surrounds the whole muscle - penetrated by vascular and nerve b) Perimysium: - less dense C.T, descends from epimysium - surrounds group Of fibers to form bundle or fascicle - Large blood vessels and nerves pass in it. c) Endomysium: - layer of reticular fibers that surround each muscle fiber. - Small blood vessels and fine nerves pass in it. - C.T. is essential for force transmission & connects muscle together. - rich in nerve fibers and blood vessels that nourish fibers through diffusion Module 103 Muscle tissue Dr. Kandeel Size: - 10-100um in diameter & variable in length. Shape: - cylindrical, non-branched (except in face & tongue). Sarcolemma: - thick due to its fusion with basal lamina, endomysium. Nuclei: - multiple, oval, beneath sarcolemma. Sarcoplasm: - acidophilic with transverse striations that appear in longitudinal section. : 1. Myofibrils: - muscle cell is filled with numerous cylindrical fibrils 2. Sarcoplasmic reticulum: - well-developed smooth endoplasmic reticulum - highly organized tubular network around myofibrils. - It is specialized for Ca++ storage & pump. 3. Mitochondria: numerous, arranged mainly in rows between myofibrils. 4. Other organelles: few and found mainly in perinuclear 1. Myoglobin: a) O2-binding pigmented protein b) provide oxygen for oxidative reaction. 2. Glycogen & lipid granules: found between myofibrils to provide energy Module 103 Dr. Kandeel Muscle tissue * shows alternating dark & light bands: explain appearance of transverse striations light band: - isotropic (l band) ? - as it does not alter plane of polarized light. - subdivided by dense membrane called Z-line. - appears light: as it is formed of only actin. - portion of myofibril between two adjacent Z lines is called: sarcomere: - basic contractile unit or functional unit in contraction. - dark band: - anisotropic (A band) ? as it alters polarized light in two planes. - appear dark: formed of both myosin & actin filaments. - shows a central pale area called H-zone, which is bisected by a thin M-line. - H-band appears paler due to the presence of myosin filaments only. - M-line is produced by interconnections of adjacent myosin filaments - thick myosin: are restricted to the A-band. - thin actin: attach to Z line and pass through l-band, then extend into A-band till beginning of H zone. Module 103 Muscle tissue Dr. Kandeel - dense by condensed actin filament & accessory proteins: maintaining alignment of thin and thick filaments) 1. Titin: - a large protein, anchors thick filaments to the Z- lines. 2. Dystrophin: - large protein, link the external lamina of the muscle cell to actin filaments. - enlargement of muscle fibers, not by the formation of new fibers ex: as with exercise. - degeneration of skeletal muscle fibers - in which satellite cells fail to replace degenerated fibers - resulting in decrease in muscle function. Module 103 Dr. Kandeel Muscle tissue many invaginations of sarcolemma, forming transverse tubules or T-tubules in the sarcoplasm. These tubules are located at the A-l band junctions Each T-tubule lies in-between a pair of wide terminal cisternae of sarcoplasmic reticulum, forming triple str. - voluntary contraction except pharynx, esophagus & cremasteric muscles are involuntary. - The contraction proceeds as follows: arrival of a nerve impulse to neuromuscular junction triggers depolarization of sarcolemma - Depolarization is spread along membranes of T- tubules It stimulates sarcoplasmic reticulum to rapidly release the Ca into sarcoplasm. Ca facilitates sliding of actin filaments over myosin deeper toward middle of the A-band. Module 103 Muscle tissue Dr. Kandeel 1. l-band decreases in size, H- zone disappears, while A-band is constant. 2. Sarcomeres, myofibril and whole muscle fibers shorten. 3. length of actin & myosin filaments is not changed. - When depolarization stops: Ca++ is pumped into sarcoplasmic reticulum, decreasing Ca++ in the sarcoplasm & contraction stops (muscle relaxation). Module 103  Dr. Kandeel Muscle tissue According to the required function: Red (dark) due to abundant White (pale) due to myoglobin, mitochondria, high abundant glycogen and less Color vascularity myoglobin. rich in myoglobin poor in myoglobin Myoglobin Mitochondria larger & more numerous less numerous Vascularization Rich Poor Glycogen Less More Size Small Large slow, prolonged & no fatigue fast, short & easy fatigue Contraction source of Aerobic: many mitochondria & O2 Anaerobic by glycolysis: energy binding myoglobin) short generation of ATP 1. long back muscles in humans. 1. Muscles that move the 2. Muscles of athletes, as in eye & digits. Site marathon 2. Muscles of short distance 3. The chest muscles of flying sprinter. birds. Module 103 Muscle tissue Dr. Kandeel Inactive myoblasts in adult muscle fiber between sarcolemma and basal lamina is called satellite cells :- a. After injury : become activated, proliferate give rise new muscle fibers. b. responsible for skeletal muscle's ability to regenerate. - At junction of muscle with tendon: a) muscle fibers taper off and C.T. components of muscle continue with tendons b) Collagen fibers of tendon insert among muscle fibers. : sudden painful contractions of muscles due to: a- lowered blood flow to them b- lowered levels of potassium c- vigorous exercise - without proper warming up (stretching) - involve muscles of lower leg. : * autoimmune disease that is characterized by weakening of skeletal muscles due to : - formation of antibodies against skeletal muscle's acetylcholine receptors. - weakening affects most active muscles first (muscles of the face, eyes and tongue), then muscles of respiration become compromised and individual dies of respiratory insufficiency. Module 103 Dr. Kandeel Muscle tissue - forms the middle layer of the heart (myocardium) - This layer is thicker in ventricles than in the atria. - Myocardium is surrounded by epicardium (visceral layer of pericardium) from outside and endocardium from inside. - formed of branched and interconnected muscle fibers - each fiber is surrounded by delicate sheath of C.T: endomysium - many separate cells, called cardiac myocytes Shape: Cylindrical, branched cells. Size: 15um in diameter Sarcolemma: Thin cell membrane. Nucleus: single (may be two), oval & central Sarcoplasm: - acidophilic, transverse striations - intercalated discs. Module 103 Muscle tissue Dr. Kandeel 1. Myofibrils: Less than in skeletal muscle. 2. Mitochondria: numerous, large with closely packed cristae. 3. Other organelles: few. 4. Sarcoplasmic reticulum: - less in number, development than in skeletal muscle. - Its arrangement with T-tubules form of Diad (Not triad) tubular system at the level of Z-line 1. Glycogen granules: concentrated between the myofibrils. 2. Lipofuscin granules: a) accumulate to be abundant in old age b) forming brown atrophy of the heart. 3. Atrial granules: a) present in muscle cells of heart atria b) contain atrial natriuretic hormones c) which affect urinary excretion of sodium & water balance. d) So, muscle cells of heart's atria also have an endocrine function. Module 103 Dr. Kandeel Muscle tissue * Definition: site of Junctions between sarcolemma of adjacent cardiac muscle cell * By LM: densely stained clear lines * By EM: - formed of transverse and lateral regions - give the discs shape of the stairway: a) transverse component : - crosses cardiac myofibers at right angle to the fibers, like risers of stairway. b) lateral component : - lies parallel to myofibers, like the steps of stairway. Desmosomes and adherent junctions (fascia adherens): - located in the transverse region of the disc - bind cardiac myocytes firmly together to prevent their separation during contractions. Gap junctions: - located in lateral segment of disc - Their position in lateral parts of disc protects them from the contraction forces. - allow the contraction signals to pass from cell to other. Module 103 Muscle tissue Dr. Kandeel highly specialized cardiac muscle fibers that constitute atrioventricular (A-V) bundle & its branches. They rapidly transmit contractile impulses to various parts of the ventricular cardiac muscle cells via gap junctions, faster than the ordinary myocardium. They are grouped into bundles which are surrounded with C.T. sheath. * Moderator band: located in the right ventricle and it contains Purkinje muscle fibers. larger in diameter than ordinary cardiac muscle fibers. No intercalated discs. Nucleus: eccentric in position. Sarcoplasm: pale & vacuolated (due to excess glycogen). No striations in sarcoplasm due to: a- few myofibrils b- peripherally situated Module 103 Dr. Kandeel Muscle tissue - Folds of endocardium - covered by simple squamous epithelium - has middle layer of dense fibrous C.T. - rich in collagen and elastic fiber, macrophages. - involuntary rhythmic contraction that is modulated, but not initiated, by autonomic innervations and hormonal stimuli. : - Cardiac muscle doesn't contain progenitor cells. - So, it cannot regenerate. - When the cardiac myocytes are injured, as in cases of myocardial infarction:- - they heal by fibrous tissue. - slowly reduction of coronary artery by impairs oxygenation of ventricular muscle leading to chest pain increases by exertion - complete obstruction of one of the coronary arteries leads to cardiac muscle fibers death - heart muscle cells release proteins such as troponin T and creatine kinase into the blood stream. - So, measure these proteins (called cardiac enzymes) in patients who present with chest pain for early diagnosis, rapid treatment. Module 103 Muscle tissue Dr. Kandeel wall of hollow viscera (e.g. digestive, urinary, genital & respiratory tracts). wall of blood vessels, skin and the eye. Smooth muscle fibers are connected together by gap junctions. Each muscle fiber is surrounded by thin reticular fibers (endomysium). Fibers are packed to form a sheet, layers or bundle Each bundle includes small group of fibers, surrounded by perimysium *Smooth muscle cells: * may be affected by hormones such as (oxytocin: stimulator of smooth muscle contraction) - plays an essential role in uterine contraction during parturition, - so used to induce or enhance labor. Module 103 Dr. Kandeel Muscle tissue small diameter, Its length varies from: a) 20 micro in small blood vessels b) to 500 micro in pregnant uterus. - Non-branched spindle - each fiber is a cell with wider central area & tapering ends. - in transverse section, smooth muscle cells appear with variable diameter. - thin surrounded by basal lamina. - shows no T-tubules : - instead there are invaginations along the cell surface, called caveolae control calcium release, muscle contraction. - single, oval & central. - Its shape is like corkscrew during contraction. ‐ acidophilic, contains numerous mitochondria, sarcoplasmic reticulum ‐ free ribosomes, Golgi, glycogen granules. ‐ present mainly at perinuclear region. ‐ Myofibrils, of thick myosin and thin actin, irregularly arranged ‐ striations do not appear in smooth muscle fibers. ‐ Actin filaments insert into sarcoplasmic and sarcolemma-associated dense bodies (correspond to Z-line in striated muscle) ‐ extend into the sarcoplasm to interact with myosin. ‐ Intermediate desmin filament also insert into dense bodies ‐ attachments of actin and intermediate filaments to dense bodies transmit contractile force to adjacent smooth muscle cells. Module 103 Muscle tissue Dr. Kandeel Module 103 Dr. Kandeel Muscle tissue - produces slow involuntary contraction that is modulated by autonomic innervations and hormones - secrete C.T. matrix & fibers as in the wall of blood vessel. - Smooth muscles can grow in size (hypertrophy) and increase in number (hyperplasia) in certain conditions as in hypertensive arteries & pregnant uterus. - Regeneration of smooth muscles after damage can occur by :- 1) mitotic division. 2) Pericytes can repair smooth muscles of blood vessels Module 103 Muscle tissue Dr. Kandeel Attached to bone The heart wall Wall of the viscera Largest Medium Smallest Single cell several cells single cell cylindrical Cylindrical spindle shaped rarely Branched non branched thick very thin Thin striated non-clear striations non striated multiple & one & central one & central peripheral regular Irregular Absent Triad system Diad system Absent intercalated disc: None fascia adherens, gap junction desmosome, gap j cannot regenerate in mitosis or from satellite cells normal conditions pericytes voluntary Involuntary involuntary motor Autonomic Autonomic muscle spindle purkinje fibers ---------- Module 103 Dr. Kandeel Dr. Kandeel Module 103 Skin Dr. Kandeel protective covering body, Largest and heaviest organ. 15-20 % of body weight. 1. Epidermis. 2. Dermis. - called subcutaneous tissue. - A deep layer of adipose CT beneath the dermis. - Binds skin loosely to subjacent tissues, allowing free movement of skin According to thickness of epidermis, skin is classified into: a) thick Skin b) thin skin. Module 103 Dr. Kandeel Skin thick epidermis and a thick horny layer. Present in palms and soles. formed of epidermis and dermis. - keratinized stratified squamous epithelium. - Thicker over soles than palms. - Avascular layer receiving its nutrition by diffusion - Rich in free nerve endings. - The epidermis is formed of keratinocytes and non-keratinocytes. - Represent 85% of cells in epidermis. - Deeper layers are continuously dividing, differentiating to give keratin filaments (keratin formation) - Superficial layers are continuously shed off. Module 103 Skin Dr. Kandeel Module 103 Dr. Kandeel Skin - Deepest single layer of - Cells are attached to each, to columnar cells prickle layer by desmosomes. - resting on clear, wavy - Cells are attached to basement basement membrane membrane by - basophilic cytoplasm. - hemi desmosomes. - Large basal oval nucleus. - rich in free ribosomes - Intense mitotic figures - few (golgi, mitochondria, rER) (responsible for renewal): - show keratin intermediate - epidermis is regenerated every filaments arranged in bundles 2-4 weeks. ending in desmosomes - Melanocytes and Merkel's cells are found - 4-8 layers of polyhedral cells - bundles of intermediate - above basal cell layer filaments (tono filaments) that - Less basophilic cytoplasm end into the dense plaques of - central rounded nuclei. numerous desmosome along - Langerhans cells are present in inter-digitating cell boundaries. this layer. N.B.: Soles of feet have thicker - Borders of cells appear to be stratum spinosum with more separated by small spaces desmosome ( spine-like processes) : * indicate where they are joined Malpighian layer: by desmosomes - Mitotic figures - both stratum basale and stratum spinosum Module 103 Skin Dr. Kandeel - 3-5 layers of spindle cells : - present above prickle cell a) Keratohyalin granules: layer - Irregular large, not surrounded by - Cytoplasm is deeply membranes. basophilic. - contain proteins rich in phosphate - They have flat pale nuclei. groups: intense basophilia - proteins are, Filaggrin and trichohyalin that promote aggregation of keratin into tonofibrils, by process called keratinization. b) Membrane-coated lamellar granules: - Surrounded by membranes. - Contain lamellar discs formed of lipid bilayer. - form lipid sheets (cement substance) that act as barrier and have a sealing effect. Cells are flattened, Thickened cell membranes. - thin, lightly stained, clear layer. Few remnants of desmosomes. - Formed of flattened cells. Organelles disappear (by lysosomal - Nuclei are on their way to activity). disappear by karyolysis. **Nuclei appear as ghosts or - More apparent in thick skin. completely disappear ** Cells have keratin filaments (tonofibrils) - thick eosinophilic layer - thickened cell membranes attached - heavily keratinized dead cells, by desmosomes. called scales - filled with mature keratin filaments (tonofibrils) - They show neither nuclei nor organelles. Module 103  Dr. Kandeel Skin ------ - Ectodermal:modified Bone marrow - neural crest (ectoderm) epithelial cells - 3-8% - resemble epidermal cells. - between stratum - stellate, found - between cells of basal layer. basale. mainly between - Abundant in highly - rounded, long irregular stratum sensitive like that of finger cytoplasmic processes spinosum of tips, hair follicles. extend between epidermis. - Naked nerve fibers keratinocytes, (sensory) traverse basal terminate in stratum In H & E: lamina and terminate as basale, spinosum - dark nucleus disc-shaped expansions - rounded pale nuclei. - pale cytoplasm. beneath Merkel's cells * H & E: do not - vital stains. forming Merkel cell-neurite demonstrate complex melanocytes. - prominent Golgi, - Cells are attached to active protein - Lysosomes (1ry, neighboring keratinocytes synthesizing cells: 2ry). by desmosomes. rER, Golgi, - Few other - electron-dense granules mitochondria. organelles. resembling those of Granules: - Special tennis- neuroendocrine cells melanosomes racquet-shaped (APUD). Nucleus: euchromatic granules (Birbeck's - Deeply invaginated and prominent granules) nucleus. nucleolus. - irregular nucleus No desmosomes - Absence of: between melanocytes , a- keratin, keratinocytes. desmosome b- Hemidesmosomes to melanin granules. bind melanocytes to c- cell junctions basal lamina. Module 103 Skin Dr. Kandeel - bind antigen then Mechanoreceptors for a) Formation of Melanin presenting it to T- light touch as they synthesize lymphocytes (act as Neurosecretory tyrosinase enzyme antigen presenting function(granules). b) Ultraviolet light speeds cells). tyrosinase synthesis, - So, have a role in thus increasing melanin skin immunological production reactions (allergic dermatitis). sketch Module 103 Dr. Kandeel Skin is beneficial in diagnosis of diseases: becomes pale in anemia, blue when blood is insufficient (heart and lung diseases). - common skin disease in which number of proliferating cells of stratum basale & spinosum increased. - This results in greater epidermal thickness & abnormal keratinization with a defective skin barrier - absence of melanin production resulting from a genetic defect in tyrosinase synthesis. - depigmented, or white patches of skin in any location on body, cause is unknown; however, autoimmune condition may be involved. - Acquired darkening of the skin due to exposure to ultraviolet radiation either from sunlight or from artificial sources Excessive exposure may lead to sunburn, accelerated aging of skin & increased risk of skin cancer. Module 103 Skin Dr. Kandeel deep Connective tissue under epidermis, Thicker than epidermis Irregular surface having projections (dermal papillae) which fit in concavities in epidermis (epidermal ridges). - Thinner superficial layer. - Thicker deep layer - Forms dermal papillae under epidermal ridges - Formed of loose C.T - Formed of dense C.T - More vascular - Less vascular (to nourish the epidermis) - More cellular - Less cellular - type III collagen & elastic fibers) - type.I (bundles) collagen & elastic fibers - Receptors: Meissner's corpuscles. - Receptors: Pacinian corpuscles, Ruffini's end organ & Krause's end bulb. Module 103 Dr. Kandeel Skin Zigzag-like between dermal papillae, epidermal ridges forming finger prints: medico legal importance. Its importance: - Provide attachment of epidermis to dermis. - Surface area for nutrition of epidermis. The basement membrane of epidermis. Dermal papillae interdigitating with epidermal ridges. Hemidesmosomes: between basal epidermal cells & basement membrane - Rapid stretch of skin leads to rupture of fiber bundles in dermis. - Scar tissue is formed in the area and form white lines, Such lines in pregnancy called "linea gravidarum” A- Atrophy of elastic fibers:- 1. reduce skin's elasticity 2. causes wrinkling B- blood vessels of dermis become :-more fragile (bruising) C- Sebaceous glands produce less oil which makes it hard to keep skin moist, resulting in dryness. D- Subcutaneous fat layer thins so it has less insulation. Module 103 Skin Dr. Kandeel It covers all the body except palms, soles, tips and sides of fingers and toes Eyelid has got the thinnest skin in the body. Palms & soles - Rest of the body Tips & sides of fingers & toes Thicker Thinner Thicker Thinner Thicker (3-5) Thinner (single) Present Less apparent Very thick Very thin More, large, regular Fewer, small, irregular Absent present sweat glands More numerous less numerous Module 103 Dr. Kandeel Skin Hair follicles and hairs Sebaceous glands Sweat glands keratinized epithelial thread that is embedded in hair follicle (Epidermal sheath) undifferentiated epithelial cells that reside in the Hair follicle Under normal conditions: ES responsible for growth of hair follicles, IRS as well as sebaceous glands. When epidermis is injured or lost: ES cells migrate toward wound surface and participate in initial healing of the wound Module 103 Skin Dr. Kandeel - bundle of smooth muscle fibers that extend from mid shaft of hair follicle to papillary layer of the dermis. In case of fear and cold: - sympathetic stimulation causes contraction of arrector pili muscle leading to erection of hair with depression of skin over muscle and elevation of skin around the hair (goose skin). - develop as outgrowths of the external root sheath of the hair follicle. - Simple alveolar (acinar) or branched alveolar. - Dermis of thin skin - associated with hairs. - Rarely without hairs: eyelids. Module 103 Dr. Kandeel Skin Each alveolus is lined by: - Short & wide and opens in upper 1/3 1. Basal flattened germinal cells: of hair follicle. - large polyhedral cells are - Lined by stratified squamous produced by mitosis of basal cells epithelium continuous with outer 2. Large polyhedral vacuolated cells: root sheath of hair follicle. - filled with numerous lipids. Module 103 Skin Dr. Kandeel - oily substance (sebum) is product of holocrine secretion. - cell undergoes programmed cell death (apoptosis) - both secretory product and cell debris are discharged from gland through their short ducts. Keeps thin skin and its hairs soft (prevent cracking). Antifungal and antibacterial. Acne: - Inflammation of sebaceous due to obstruction of duct by sebum known as (white head). - If the plugged sebum mixed with melanin, it is known as (black head). Module 103 Dr. Kandeel Skin - Type: Simple tubular coiled glands. - Site: Deep in the dermis, all over the body except: glans penis & nail beds - All over body except glans - Thin skin of axillary, pubic, penis & nail beds perineal regions - More numerous - Less numerous, Not present - More in thick skin in thick skin - Merocrine (by exocytosis) - Small in size Large in size - Narrow lumen Wide lumen * Formed of three types of cells: * Formed of two types of cells: - More numerous - Esinophilic cytoplasm - Broad base, narrow apex. - apical cytoplasm contains - Pale cytoplasm (glycogen), numerous small granules that - Intercellular canaliculi between * discharge their content by clear cells. exocytosis. - Less numerous - Narrow base, wide apex - Dark cytoplasm (dark granules: glycoprotein). N.B.: Watery secretion of clear cells passes through canaliculi to lumen where it mixes with the protein product of dark cells. Module 103 Skin Dr. Kandeel - Spiral course in dermis & - Spiral course in dermis epidermis - Opens into a hair follicle - Opens into epidermis - Lined by 2 layers of cubical cells - Lined by 2 layers of cubical cell - Appears darker than the secretory part - Sweat is a clear watery fluid - Start function at puberty. (water, NaCl, urea & ammonia) - They secrete viscous odorless with low protein content. secretion that becomes offensive - Its main function is body by bacterial action. temperature regulation. Module 103