ANAT2241 Lecture Summary PDF

lOMoARcPSD|34309248 ANAT2241 - Lecture Summary Histology: Basic and Systematic (University of New South Wales) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or univers...

lOMoARcPSD|34309248 ANAT2241 - Lecture Summary Histology: Basic and Systematic (University of New South Wales) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC  Single layer polygonal-shaped cells with a Epithelium centrally placed nucleus  Location: lining tubules or ducts (kidney Structural Organisation tubules, salivary glands, pancreas for enzyme  Epithelial tissue is present in two forms production, thyroid follicles for hormone 1. Sheets of cells that cover external surfaces (skin, lining of digestive/ respiratory/ production, ovary cardiovascular tracts, pleura, peritoneal and pericardial membranes etc.)  Function: secretory, absorptive, protection 2. Glands (exocrine and endocrine) originate from epithelial cells Columnar  Cells appear tall  Epithelial cells are close to each other with space between membranes and small amounts of  Nuclei located basally in a single row intercellular material (glycosaminoglycan – acts as a cement)  May have microvilli on apical surface of cells  Junctional complexes between epithelial cells. Hold adjacent cell membranes together (small intestine) or cilia (oviducts, efferent  All epithelial cells sit on a basement membrane, separating them from underlying connective tissue ductules, small bronchi, paranasal sinuses)  Epithelium is avascular and depends on diffusion of substances across basement membrane  Location: small intestine, inner lining of gall bladder, larger ducts of glands, stomach lining, uterus and oviducts. MAIN FUNCTIONS OF EPITHELIUM  Function: reabsorption of water from bile,  Protection of underlying tissues from abrasion, injury, dehydration, invasion. secretion of enzymes and mucus and absorption  Regeneration in skin wound healing and renewal of the lining cells of the uterus following of nutrients and fluids, protection. menstruation and in the replacement of cells lining the GI tract (every 4 to 6 days). Pseudostratified Columnar  Secretion by glandular epithelial cells of products into the blood (hormones), ducts and hollow  Appears stratified but is a single layer of cells. organs (acids and enzymes), or onto the skin (sweat and sebum).  All cells in contact with basement membrane,  Absorption lipids in the SmIn. and selective re-absorption in kidney tubules (sodium). but only some reach surface of epithelium.  Detection sensations taste buds, retina of eye, specialized hair cells in the ear.  Because the cells are of different heights, their  Lubrication by various types of glandular epithelial cells, which secrete mucus and help the nuclei are located at different levels, giving the movement of food along the alimentary tract. Mesothelial cells, lining the closed body cavities, impression of a stratified epithelium secrete a thin serous fluid that prevents friction between organs e.g. heart, lungs.  Location: urethra, epididymis and larger  Excretion by epithelial cells, which filter waste products from the blood and then excrete them as excretory ducts of glands. urine or sweat.  A ciliated form is found lining most of the  Diffusion of gases (O2/CO2) by squamous epithelium (endothelium) of capillaries in the lungs. trachea and primary bronchi, the auditory tube, and the nasal cavity. Function: secretion (mucus), lubrication, CLASSIFICATION OF EPITHELIA transportation (mucus), and protection.  Classified according to 3 characteristics Stratified Stratified Squamous (Non-Keratinized) 1. Number of cell layers (simple or stratified)  Protective function  Composed of several layers  thick. Only 2. Shape of cells (squamous, cuboidal, columnar)  Degree of deepest layer in contact with basement 3. Presence of surface features (cilia, microvilli, keratin) stratification is membrane related to kinds of  Deepest cells are cuboidal, surface cells are physical stresses to squamous Simple Squamous which the surface is  Because surface cells are nucleated – non-  Found on adsorptive  Single layer of tightly packed, flattened cells exposed keratinized and secretory  Location: lining blood and lymph vessels  Classified according  Location: lining of mouth, oral pharynx, surfaces (endothelium), lining of pleural, peritoneal and to the shape of the oesophagus, vocal cords and vagina.  May have surface pericardial cavities (mesothelium), alveoli, and superficial (surface)  Function: protection, secretion (mucus) specializations (E.g. loops of Henle. cells Stratified Squamous Keratinized microvilli and cilia)  Function: Thin and functions where an  Similar to non-keratinized except superficial exchange of gases (alveoli), fluids (loop of layers are composed of dead cells whose nuclei Henle), nutrients, or metabolites occurs. and cytoplasm have been replaced with keratin  Location: skin epidermis.  Function: protection Stratified Cuboidal  2+ layers of cuboidal cells  Location: lining ducts of sweat glands. Cuboidal  Function: absorption, secretion. Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Stratified Columnar BASOLATERAL AREA  Composed of a low polyhedral to cuboidal  2 regions – lateral plasma membrane and basal plasma membrane deeper layer in contact with the basement  Each region possesses its own junctional specialisations and receptors for hormones and membrane and a superficial layer of columnar neurotransmitters cells.  Location: conjunctiva of the eye, large Lateral Plasma Membrane Specialisations excretory ducts of glands and the cavernous  Terminal bars where epithelial cells contact each other. Classified into 3 types urethra. 1. Zonula Occludens (Tight Junctions)  Function: secretion, absorption, and protection - Prevent movement of membrane proteins from the apical domain to the basolateral domain. Transitional Epithelium  Located solely in the urinary system – lines - Fuse plasma membranes of adjacent cells disallow water-soluble molecules from passing urinary tract from the renal calyces to the urethra between cells.  Composed of 5+ layers of cells – those that are 2. Zonula Adherens located basally are either low columnar or - Below the zonulae occludens, join cell membranes and maintain cell-to-cell adherences cuboidal cells 3. Desmosomes (Macula Adherens)  Superficial cells of the empty bladder are large, - "spot weld-like" junctions along lateral cell membranes of simple epithelia and throughout cell occasionally bi-nucleated and exhibit scalloping membranes of stratified squamous epithelia, esp. in epidermis. that bulge into the lumen become squamous and epithelium things when bladder is stretched Basal Plasma Membrane/Basal Lamina Specialisations  Function: protection, distensibility  Anchor basal plasma membrane to basal lamina  Acellular supportive structure (20-100nm thick) SURFACE MODIFICATIONS  Secreted by epithelium resting on it Apical Surface (top of cell)  Located at boundary between epithelium and underlying connective tissue  Site where secretory products are delivered for release into surrounding micro-environment  Composed mainly of Type IV collagen, laminin, and proteoglycans.  Several surface modifications include microvilli, stereocilia, cilia, and flagella.  The basal lamina with a deeper layer, the reticular lamina of the CT (reticular fibres and ground substance) is the "basement membrane" of light microscopy Microvilli  Projections of cytoplasm (plasma membrane) from the top surface of these cells  All epithelia supported by basement membrane  Example: The striated border of intestinal absorptive cells and brush border of the  Epithelial cells dependent on diffusion of oxygen and metabolites from underlying tissues kidney proximal tubule cells.  In intestinal epithelia, where absorption occurs, microvilli increase (up to x30) the Functions surface area of cells.  Diffusion barrier to protect movement of harmful substances into blood Stereocilia  Long microvilli (not cilia) found in epididymis, vas deferens and on sensory hair  Provides elastic support for protection against trauma from hard, rough materials cells of the cochlea (inner ear).  These non-motile structures in the epididymis function to increase the SA (absorbing fluid surrounding the sperm), whereas in the hair cells of the ear they Gap Junctions (Nexus, Communicating Junctions) function in signal generation.  Gap junctions allow intercellular communication by passage of ions and small molecules between Cilia  Motile projections (diameter 0.2 μm/length 7-10 μm) from surface of certain adjacent cells epithelial cells (e.g. trachea, bronchi and in oviduct).  Specialized to function in propelling mucus (trachea) and other structures (fertilized ovum by the oviduct) over the surface of the epithelium via rhythmic CLINICAL CONSIDERATIONS wavelike oscillations.  Epithelium may undergo metaplasia (abnormal change in the nature of a tissue) transforming into Flagella  Resemble cilia but are longer and wider and occur singly as free cells E.g. another epithelial form spermatozoa.  Pseudostratified ciliated columnar epithelium of the bronchi of heavy smokers may undergo  By whip like action, aid in moving sperm. squamous metaplasia transforming into stratified squamous to resist continuous abrasion Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Glands  Glands: Epithelial invaginations into underlying CT forming secretory units Function  Glandular epithelia make their product intracellularly by synthesis of macromolecules and stored in vesicles (secretory granules)  May be: - hormone (mucin) from goblet cells Compound - sebum from sebaceous glands  Compound tubular Brunner’s glands of duodenum - enzymes from exocrine part of the pancreas  Compound acinar pancreas  Glandular epithelium can remove metabolic wastes (E.g. through sweat glands)  Compound tubulo-acinar types salivary glands, mammary, prostate and seminal vesicles Classification Glands can be classified on:  Organisation (endocrine/exocrine)  # of cells involved  Having ducts  Branching of ducts  Material secreted and manner in which secreted 1. EXOCRINE GLANDS  These glands maintain their continuity with the epithelial surface via a duct Architecture  Exocrine glands put products through ducts that open into lumen of an organ or onto the skin  Larger multicellular glands are surrounded by CT capsule sending septa (strands of CT) into the gland  Classified as unicellular or multicellular  subdividing it into smaller compartments lobes and lobules  Septa where blood vessels, lymphatics, nerves, and ducts enter and leave the gland. Also provides Unicellular structural support  Simplest form as isolated secretory cells in epithelium (goblet cells), amongst the simple columnar  Location of ducts in a gland may be: epithelia lining the digestive tract (small intestine) and pseudostratified columnar epithelium of the respiratory tract (trachea) - Interlobar (between lobes)  Mucous lubricates the passage of materials protecting the lining along parts of the GIT - Intralobar (within lobes)  In respiratory system, it moistens the air and traps inhaled dust and other pollutants and antigens - Interlobular (between lobules) - Intralobular (within lobules). Multicellular  Gland composed of 1+ cell and drained by a series of ducts Secretion Types  Classification into simple or compound multicellular is by the morphology of their ducts and the  Glands can be classified according to type of material secreted shape of the secretory portion Mucous (E.g. goblet cell) - Tubular straight or coiled  Mucinogen and large glycosylated proteins which swell to become gel-like protective lubricants - Acinar grapelike (mucin) - Alveolar flask like Serous (E.g. in pancreas and salivary glands Ducts (non-secretory portion)  Watery and rich in enzymes  Simple: Single duct which does not branch.  Compound: Several ducts which branch. Mixed (E.g. sublingual and submandibular salivary glands)  Contains acini (secretory units) that produce mucous secretions as well as acini that produce serous Simple secretions  Simple tubular (large intestine, stomach body, uterine endometrium)  Some mucous acini have serous demilunes that secrete serous fluid  Simple coiled tubular (sweat glands)  Simple branched tubular (pylorus of the stomach, oesophageal glands)  Simple branched acinar (sebaceous glands). Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Mixed Endocrine/Exocrine Glands  Glands that contain both endocrine and exocrine secretory units (E.g. pancreas) - Exocrine portion secretes its product (digestive enzymes) into duct - Endocrine secretes product (hormones) into blood Myoepithelial (Basket) Cells  Secretory units of some glands have myoepithelial cells between glandular cells and the basal lamina  Long cytoplasmic processes extend from body of the cell around the secretory unit and by their contraction, express products from the secretory units into the ducts.  Found in sweat, mammary and salivary glands.  These cells are epithelial in origin, but function like a muscle (myo-) by contracting with actin filaments. Mode of Secretion Eccrine –  Process of exocytosis Merocrine  Most common form of secretion (E.g. salivary glands) Apocrine  Involves top of the cell being punched off with portion of the cytoplasm becomes part of the secretory product (lipid droplet)  Remainder of cell repairs itself and continues to secrete milk in mammary gland Holocrine  Involves discharge of the whole cell with disintegration of the entire cell to release the secretory product  Occurs in sebaceous glands  Basal cells multiply to replace lost cells  gland continues to secrete sebum 2. ENDOCRINE GLANDS  Arise from epithelium sheet and lose their connections with surface  lack ducts to leave isolated islands of epithelial secretory tissue within other tissues  These glands secrete hormones directly into blood - Hormones empty into tissue spaces enter blood and lymphatics for distribution to target organs/tissues  Major endocrine glands include adrenal, pituitary, thyroid, parathyroid, pineal gland, ovaries, testes Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC placed nuclei in which chromatin may Connective Tissue – Components be distributed along the nuclear envelope forming the "clock face"  Connective tissue (CT) has cells and extracellular materials fibres, ground substance, tissue fluid nucleus.  Produce immunoglobulins (antibodies) Ground Substance (GS) that form a defence against infection  Ground substance Fibres and cells of CT are embedded in gel of variable viscosity Lymphocytes  Cells that have come from the blood  Composed of glycosaminoglycans (GAG) into CT - Hyaluronic acid is the main GAG. Because of its capacity to bind water, it is responsible for  Responsible for initiating cell mediated changes in the permeability and viscosity of the CT immune response (T cells) or when  GS plays role in preventing or retarding the spread of microorganisms and toxic materials at sites of activated, differentiate to form plasma infection cells, which provide humoral immunity  Tissue fluid (mainly water) is loosely bound to GS forming a medium passage of materials through (B cells). the CT and for the exchange of metabolites (nutrients, waste etc.) with the circulation  Have small dark nucleus and little cytoplasm. Fibres  The fibres in CT are collagen, reticular and elastic produced by fibroblasts. Cells Fibroblasts  Most common CT cells  Flattened cells with elliptical nuclei that contain 1-2 nucleoli  Cell body looks stellate with cytoplasmic processes extending along Macrophages  Phagocytosing cells CT fibres  Responsible for removing particulate  Elaborate precursors of collagenous, matter and assisting in the immune reticular and elastic fibres response.  Produce ground substance  Originate in bone marrow, circulate in the blood as monocytes, and migrate into the CT where they perform their functions. Mast Cells  Large, ovoid cells (20-30 μm) with large granules in the cytoplasm  Cytoplasm contains - Heparin (anticoagulant) ADULT CONNECTIVE TISSUE TYPES - Histamine (causes vasodilation  General CT divided into loose or dense according to how fibres are packed and increases permeability of capillaries so excess plasma Loose CT (areolar) enters the CT spaces, causing  Can be classified further on basis of special properties of their constituents (E.g. adipose, reticular swelling) tissue)  Fewer fibres but more cells and matrix  Characterised by ground substance and tissue fluid housing the CT cells as well as some undifferentiated cells  Scattered through ground substance are loosely woven collagen, reticular and elastic fibres  Location widely distributed, filling in spaces just deep to the skin, below mesothelial lining of body cavities, in the adventitia of blood vessels, and respiratory tract.  Function Binds organs and organ components. Because this tissue lies immediately beneath the epithelia of the digestive and respiratory tracts, it is where the body first attacks antigens and bacteria. Plasma Cells  Ovoid in shape with eccentrically Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Reticular CT  Forms delicate networks and support of various organs  0.5-2.0m diameter  Type III collagen embedded in loose CT  Location embryonic CT, around fat and smooth muscle cells and a fine supporting mesh in the liver, lymph nodes, and spleen. Elastic CT  Loose bundles of elastic fibres with some collagen and cartilage in between.  Elastic fibres are coiled, branching fibres 0.2-1.0 μm in diameter, and stretch up to 150% of their resting length.  Location dermis, lungs, elastic cartilage and large blood vessels. Dense CT  Contains more fibres but less matrix and fewer cells than loose CT Dense Regular CT  Fibres are arranged in parallel bundles for tensile strength in 1 direction. Connective Tissue – Types  Fibroblasts occur in rows parallel to the collagenous bundles and are the only cells present with little ground substance FUNCTIONS OF CT  Location tendons, ligaments and aponeuroses.  Transport CT carry blood vessels and lymphatics, mediate the exchange of metabolites (nutrients, wastes, gases) between tissues and the blood. Dense Irregular CT  Support ligaments, tendons and rigid forms (bone, cartilage). Cartilage forms temporary skeleton  Contains thick collagenous bundles, irregularly woven into a compact meshwork resisting stress and of foetus. producing tensile strength from different directions.  Repair scar tissue formation after injury.  Among collagen fibres is a network of elastic fibres and cells such as fibroblasts, mast cells,  Defence phagocytes (macrophages), antibodies (plasma cells), inflammatory response (mast cells, macrophages. ground substance viscosity).  Location: dermis of skin, the sheaths of nerves, and the capsules of spleen, testes, ovary, kidney, and  Storage fats (lipids), bone (calcium). lymph nodes.  Packing space between epithelium, muscle, and glands. Dense Regular Elastic CT EMBRYONIC CONNECTIVE TISSUE  Possesses branching elastic fibres arranged parallel to each other with only a few collagen fibres Mesenchyme forming networks.  Loose, spongy tissue  Location large blood vessels, ligamentum flava, of the spine, and the suspensory ligament of the  Forms packing between structures of the embryo penis.  Spindle mesenchymal cells in a gel-like amorphous matrix containing a few scattered reticular fibres - Multi potential can give rise to any of the adult forms of CT Mucoid  Loose CT found in parts of the embryo – esp. in umbilicus (Wharton’s Jelly… idk sounds gross)  Has large stellate-shaped fibroblasts and jelly-like matrix (mainly hyaluronic acid) with sparse collagen fibres SPECIAL FORMS OF CONNECTIVE TISSUE Adipose Tissue  Adipose cells adipocytes  Derived from undifferentiated mesenchymal cells which then store and metabolise fat  Represent 15-20% body weight in males, 25% in females  2 types White Fat  More than brown in number and distribution  Signet ring shape (50-150um) Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC  Flat peripherally located nucleus and a thin ring of cytoplasm. Rest of cell filled by a single, large droplet of lipid (unilocular) which is free in the cytoplasm and is composed of glycerol esters and fatty acids. Location:  Mainly in adults  Men fat stored in subcutaneous tissue of neck, shoulders, buttocks, abdominal wall, around kidneys and in bone marrow.  Women fat is largely stored in breasts, buttocks, hips, lateral thighs, around the kidneys and bone marrow. Function: Storage depot, production of energy, insulation, packing material and shock-absorbing pads in the palms of the hands, soles of the feet, around the eyeball and kidneys. Brown Fat  Cells are smaller than white fat but show centrally placed round nuclei with a cytoplasm filled with numerous small droplets of lipid (multilocular) Location:  Foetus and newborn mammals, some hibernating animals. Especially in the interscapular and inguinal regions, some found in the adult E.g. mainly around the aorta. Function:  Thermoregulation. Cartilage  Semi-rigid form of CT for support, resisting mechanical stresses (shock absorber) and smooth movement  Has cells, fibres and ground substance.  Together, the fibres and ground substance form the matrix.  Physical properties of ground substance gives the firm consistency to cartilage and enables it to withstand pressure and shearing forces.  The collagen and elastic fibers embedded in the ground substance provide tensile strength and elasticity.  Cartilage has no nerve or blood supply of its own and no lymphatics. Nourishment is derived by diffusion of materials through the matrix from blood vessels in adjacent tissues. Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC MATRIX CELLS  Cartilage matrix contains: Collagen (40%), Proteoglycans, Glycoproteins, ECF. Chondrogenic cells  Spindle-shaped derived from mesenchymal cells. They have an ovoid  The GS and fibers of matrix form a framework that resists tensile forces. nucleus with 1-2 nucleoli. These cells can differentiate into chondroblasts as well as into osteoprogenitor cells.  The matrix is subdivided into two regions: 1. Territorial matrix (stains deeper, sulphate groups on the GAG’s) around each lacuna or Chondroblasts  Derived from 2 sources: mesenchymal cells within the centre of isogenous group (a 50μm wide band, poor in collagen and rich in chondroitin sulfate). chondrification and chondrogenic cells of the inner cellular layer of the 2. Interterritorial matrix (stains lighter, less sulphate groups on GAG’s), which is the bulk of the perichondrium. matrix rich in type II collagen and poorer in proteoglycans than territorial matrix. Chondrocytes  Chondroblasts surrounded by matrix, which they manufacture and maintain. These cells can resume active protein synthesis if they revert PERICHONDRIUM back to chondroblasts.  Mesenchymal cells at the periphery of cartilage form fibroblasts. These cells make collagenous CT perichondrium  Two layers 1. Inner region  Cellular (chondrogenic) composed of cells which differentiate into chondroblasts and begin to make matrix 2. Outer region  Fibrous (elastic, collagen, fibroblasts, blood vessels) and also contains chondroblasts which have been pushed out as a result of inner growth  The perichondrium is vascular, and its vessels supply nutrients to the cells of cartilage.  In areas where the cartilage has no perichondrium (E.g. articular surfaces of a synovial joint) the cartilage cells receive their nutrients from the synovial fluid that flows in joint surfaces. CARTILAGE FORMATION  Starts with the differentiation of embryonic mesenchymal cells to form chondroblasts, which make ground substance and fibrous extracellular material.  Secretion of extracellular material traps each chondroblast in a space or lacuna within the cartilaginous matrix  Each chondroblast then undergoes mitotic divisions to form a small group of mature cells (chondrocytes) separated by extracellular material.  These cluster (isogenous groups) of 2-4+ cells in lacunae the offspring of a single cell. Types of Cartilage Growth Interstitial Growth  Results from proliferation of young chondrocytes which divide and lay down new matrix to produce an expansion of cartilage from within  Occurs in young cartilage to allow expansion and lengthens bone  Articular cartilage (hyaline type at the synovial joint surface) lacks a perichondrium and grows only by interstitial growth Appositional Growth  Growth at the periphery where chondrogenic cells in the perichondrium differentiate into chondroblasts, forming a new layer of cartilage around the periphery of the existing cartilage  This growth increases the width of the cartilage Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC 3 Types of Cartilage Based on Fibres Present in Matrix Type Description Location Hyaline  Common type  Nasal septum, larynx,  Has ground substance, type II tracheal rings, bronchi, collagen fibres (40% of matrix) and sternal ends of the ribs, the small groups of chondrocytes skeleton of the foetus, epiphyseal (growth plate) in growing bones. Elastic  Is a variety of hyaline cartilage except  Where support with it also contains elastic fibres between flexibility is required type II collagen fibre bundles  The ear pinna, auditory  It has a perichondrium whose outer tube, epiglottis and parts of fibrous layer is rich in elastic fibre the laryngeal cartilages  Grows by apposition (cuneiform). Fibrocartilage  Transition between dense CT and  Where support and tensile (fibrous cartilage) hyaline cartilage strength is needed  Matrix consists of cartilage cells  Intervertebral discs, enclosed within lacunae menisci, pubic symphysis  The cartilage cells lay singly, in pairs or short rows between bundles of dense collagen fibers  Unlike the other two types, fibrocartilage does not possess a perichondrium, has a small amount of matrix in the vicinity of the cells and has bundles of type I collagen  Chondrocytes are aligned in alternating parallel rows with the thick bundles of collagen, which cope with the tensile forces.  Chondrocytes of fibrocartilage usually arise from fibroblasts that begin to make proteoglycans.  As the ground substance surrounds the fibroblast, the cell becomes trapped in its own matrix and differentiates into a chondrocyte. Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC  Occupy shallow depressions, (Howship's lacunae). Bone Formation and Joints  Ruffled border (infolded plasma membrane) is that part of the cell that is directly involved in the resorption of bone.  Bone Specialised connective tissue BONE FUNCTIONS  Framework support for skeleton PERIOSTEUM  Protection Brain and spinal cord, lungs and heart  Vascular, fibrous layer which surrounds bone except over articular surfaces  Serve as lever for the muscles which attach to them via tendons  2 layers  Reservoir for minerals calcium, magnesium etc. Outer Layer  Made of collagen with some elastic fibers  Thin layer distributes vascular and nerve supply to bone BONE MATRIX  From the outer layer, fine bundles of collagenous fibers (Sharpey’s) penetrate the  Extracellular matrix (ground substance and fibres) underlying bone at intervals to attach the periosteum, especially at sites of attachment of tendons and ligaments. Inorganic Materials 65% Inner Layer  Cellular (osteogenic layer, osteoprogenitor cells) that gives rise to new bone.  E.g. calcium phosphate, calcium carbonate, magnesium, sodium, potassium, bicarbonate, fluoride,  Endosteum Lining of central cavity of a bone. A thin CT of osteoprogenitor citrate, sulfate, and hydroxide) Gives bone rigidity and hardness cells and osteoblasts Organic Material 35%  Type I collagen which gives bones slight flexibility  Ground substance BONE MATRIX DEVELOPMENT - E.g. GAG’s with proteins (proteoglycans) which contain sulfates (chondroitin and keratin) 1. Bone starts as osteoid, which is collagen and GAG’s with no minerals. which gives bone resilience 2. Bone becomes mineralised (immature, primary or woven bone). It is the first bone to appear in development and in repair after fractures. 3. Bone starts to remodel as the adult form (mature, secondary, lamellar). BONE CELLS Osteoprogenitor  From embryonic mesenchyme (osteogenic) cells  Differentiates into osteoblasts MATURE BONE ORGANISATION  2 types of mature bone dense and cancellous Location  Inner cellular layer of the periosteum, lining Haversian canals, endosteum 1. Dense (Compact) (lining of the medullary cavity)  Edge of bone Osteoblasts  Derived from osteoprogenitor cells  Haversian systems AKA osteons complex of 4-20 concentric, bony lamellae surrounding a central  Form and grow new bone by synthesis of the organic components of the canal (AKA Haversian canal) 20-100um diameter bone matrix - The canal contains blood vessels, with a few unmyelinated nerve fibers, loose CT, and flattened osteogenic and osteoblast cells that line the lumen of the canal. Location  Osteocytes are in lacunae located within or between the lamellae.  On surfaces of existing bone tissue where they deposit the new bone matrix  A second arrangement of lamellae is found between the osteons, (interstitial lamellae). These are (osteoid), which contains no minerals remnants of older, partially resorbed Haversian systems.  Later mineralisation occurs and the tissue new bone  A third arrangement (circumferential lamellae) are rings of bone around the entire bone, beneath the  Osteoblasts extend processes with neighbouring osteoblasts for molecular periosteum. transport  Canaliculi Radiating from the lacunae are tiny channels Osteocytes  Flat cells with small cytoplasmic processes - Processes of the osteocytes enter these canals and communicate with adjacent osteocytes where  Aid in the maintenance of bone tissue and the storage of minerals an exchange of gases occurs, nutrients are supplied to the cells, and metabolic wastes are  Each osteoblast becomes surrounded by secreted matrix; and once this eliminated. occurs, the cell is known as an osteocyte (mature bone cell), and the space it  The Haversian canals communicate with the marrow cavity, the periosteum, and with each other via occupies is a lacuna. the transverse Volkmann's canals, which run at right angles to the long axis of the bone.  Radiating out in all directions from the lacuna are tunnel-like spaces  Each osteon has a cement line of calcified ground substance with some collagen fibers. (canaliculi), which house cytoplasmic processes of the osteocytes.  Canaliculi allow transfer of nutrients, and wastes between the osteocytes and 2. Spongy Bone Cancellous Bone the blood. NOT organised into Haversian systems but is a meshwork of thin bars (lamellae) or trabeculae of  Osteoclasts  Large, motile, multinucleated cells (150 μm diam), contain up to 50 nuclei. bone lining the marrow cavity  Cells break up and resorb bone.  Spaces within latticework are filled with bone marrow Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC  Trabeculae houses osteocytes in lacunae that are fed by diffusion from the marrow cavity - resorbed, and replaced by bone (all the cartilage is replaced by bone)  Found in long and short bones, pelvis, and vertebrae. Blood and Nerve Supply  Bones have periosteal vessels which penetrate the bone of the diaphysis of long bones and divide into DEVELOPING BONE REGION AT THE EPIPHYSEAL PLATE branches that enter the Haverian systems  Epiphyseal plate Area between shaft and epiphysis  Supply osteocytes embedded in the calcified matrix. Larger vessels pierce the epiphysis to supply the  Proliferation occurs at epiphyseal plate. Replacement takes place at diaphyseal plate spongy bone and the midshaft to supply the medullary cavity.  Series of 5 zones beginning at the centre of the disk and go toward diaphysis  Small myelinated and unmyelinated nerves go into the Haversian canals.  Periosteum contains many pain fibers, which makes it sensitive to injury e.g. a blow on the tibia. Zone of Reserve Cartilage  Chondrocytes through the matrix are mitotically active producing (resting zone) hyaline cartilage. Zone of Proliferation  Chondrocytes proliferate and form stacks of cells that parallel the direction of bone growth Zone of Maturation and  Chondrocytes mature, hypertrophy and accumulate glycogen in their Hypertrophy cytoplasm.  No mitosis occurs. Zone of Calcification and  Chondrocytes die and cartilage matrix becomes calcified Cell Death impregnated with calcium and phosphorus. Zone of Ossification  Blood vessels invade spaces left by dying chondrocytes carrying osteoprogenitor cells from the periosteum  Differentiate into osteoblasts which elaborate matrix that becomes calcified on the surface of calcified cartilage.  As matrix calcifies, some osteoblasts are entrapped as osteocytes bone trabeculae are formed.  Coalescence of trabeculae creates spongy bone.  Resorption of spongy bone by osteoclasts in the centre of the diaphysis enlarges the medullary cavity. HISTOGENISIS OF BONE DEVELOPMENT  Bone development is mesodermal in origin  If the tissue is membrane like (a sheet of mesenchyme of loose CT) it is intramembranous bone formation  If bone replaces cartilage that is largely resorbed before bone is formed endochondral (intracartilaginous) bone development. Intramembranous Bone Formation  Mesenchyme directly to bone  Flat bones skull, mandible, clavicle SUMMARY OF HISTOCHEMCAL PROCESSES FOR BOTH MODEL OF BONE FORMATION Endochondral Bone Formation 1. Osteoblasts secrete osteoid with NO minerals.  Process of bone formation occurs in two steps 2. Formation of primary bone whereby osteoid is mineralized. 1. A miniature hyaline cartilage model is formed in the region where bone is to grow within the embryo 3. Formation of secondary bone as compact or spongy types. 2. Cartilage model grows appositionally and interstitially and serves as a structural scaffold for bone development. GROWTH Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Interstitial length  Due to interstitial growth of the epiphyseal cartilage JOINTS  Growth continues until 20 years of age  Classified according to degree of movement between bones of the joint - Epiphyseal plate closes (cartilage replaced by bone) Synarthroses Syndesmosis -  growth in length stops.  Little to no  Union of bones by dense CT Appositional width  Appositional growth from surface and resorption by osteoclasts of the movement  Tibiofibular and radioulnar joints inner shaft so that marrow space can be enlarged BONE REMODELING  Continual remodelling occurs in response to forces E.g. Teeth growing in jaw bones  Bone deposited due to traction and resorbed due to pressure  Young bone deposition > bone resorption  Adult bone bone deposition = bone resorption Synchondrosis  Junction by cartilage  IV discs and symphysis pubis Synostosis  Joint united by bone  Skull sutures Diarthroidal Synovial  Knee, hip, shoulder  Great freedom of movement and have a CT capsule around a joint cavity held by ligaments  Joint has articular cartilage (hyaline) with no perichondrium  Capsule lined (except over articular surfaces) with a cellular, vascular, folded synovial membrane made of loose CT, which secretes a viscous, lubricating, synovial fluid Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Blood Shape  Round  Blood specialised type of loose CT  Biconcave disk  Ground substance fluid (plasma)  8.5 x 2.5μm in size.  Fibres strands of fibrin, only found in blood clot formation  Cells erythrocytes and leukocytes in the plasma.  Other constituents of plasma non-cellular blood platelets (thrombocytes), for blood coagulation, BLOOD CELLS – LEUKOCYTES lipid droplets (chylomicrons) and specific proteins (immunoglobulins).  Contain nucleus and cytoplasmic organelles  Arise mostly in red bone marrow and lymphoid tissue and enter blood when mature - The average adult has about 5 L of blood in circulation.  Pass through capillary walls by amoeboid movement into the tissue spaces to carry out functions (phagocytosis, immune reactions, wound repair, and control of infections) BLOOD FUNCTIONS  Less numerous than RBCs. Transport Gases, nutrients, electrolytes, wastes, hormones, antibodies, cells and particles - ~ 5,000-9,000/mm3 of blood for women Protection Against pathogenic agents by cells of immune system - ~ 6,000 -10,000 for men. Control Body temp through changes in circulation - Neutrophils 55-70% pH balance Maintained by buffers which neutralise acids and bases - Eosinophils 1 - 4%, Fluid balance Maintained between cells for their normal functioning - Basophils, 0.5 - 1%, - Lymphocytes 25 - 40%,  When blood is exposed to air, it clots trapping cells in a jellylike mass. - Monocytes 2-8%  The clear, straw-coloured fluid that remains is serum, which differs from plasma by the absence of fibrin. Classification  If blood is prevented from clotting by adding an anticoagulant (heparin) and then centrifuged, 3 layers  2 main classes exist based on type of cytoplasmic granules and morphology of nucleus form. - Granular w/ 1+ lobe per nucleus polymorphonuclear - Top layer plasma. - Non-granular w/ no nucleus lobulation mononucleuar - Middle layer buffy coat has leukocytes and platelets, and is about 1% of the column. - Lower layer RBCs Granular Leukocytes Neutrophils  Most common WBC PLASMA  Additional neutrophils escape from capillaries into tissue spaces or internal  Slightly alkaline fluid that transports and is a solvent of nutrients of the body cavities  Transports dissolved gases (CO2), electrolytes, waste materials, regulatory substances (hormones and - Become phagocytes ingesting bacteria and particulate matter (E.g. enzymes) Carbon) - Attracted to site of infection by chemotaxis and move by amoeboid Proteins movement to infected area  Proteins are main component of nutrients  Engulf bacteria and release hydrolases which lyse surrounding cells  Albumin most common protein. Role is maintain osmotic pressure of blood or blood vessel wall  ~ 10-14μm diameter with multi-lobed nucleus (3 to 5 ovoid lobes) connected by  Other proteins are globulins (alpha, beta, gamma, immune) and fibrinogens strands of chromatin.  Specific proteins (immunoglobulins) recognize and attach to foreign molecules  Cytoplasm filled with granules containing alkaline phosphatase and bactericidal (antigens), blocking the invasion of harmful organisms proteins (phagocytins) destroy bacteria after ingested by neut.  Example Bacteria. Lifespan  6 hrs - few days. BLOOD CELLS – ERYTHROCYTES Eosinophils  Orange/red granules  Function transport O2 from lungs to cells and return CO2 to be exhaled.  1.0um diameter which can partially obscure bi-lobed nucleus  Lose nucleus and organelles during maturation in order to increase efficiency.  Granules are lysosomes containing peroxidase, histaminase, hydrolytic enzymes - Filled with haemoglobin (similar to granules of neutrophils)  Flexible cell membrane enables it to traverse capillaries smaller than its diameter.  Slightly larger than neutrophils (11-15 μm).  Life span ~ 120 days.  May increase in parasitic infestations, chronic infections and most allergic  2,500,000 RBCs lost per second and same number of new cells must enter the blood in the same reactions. period to maintain normal haematocrit.  Sluggish amoeboid movement through capillary walls into tissue spaces, in the  Some senile cells are destroyed by phagocytosis in liver/bone marrow, but most are phagocytosed in intestinal mucosa. the spleen.  Show limited phagocytic activity against bacteria but phagocytize antigen  Polysaccharide layer (glycocalyx) covers external surface of membrane, which contains blood group antibody complexes. antigens, important in matching blood for transfusions, as well as an antigen for the Rh blood factor. Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Lifespan  8 - 12 days. Basophils  Number about 0.5-1% of circulating WBCs.  10-12μm diameter.  Identified by presence of many basophilic granules, scattered over the large bi- lobed nucleus, usually obscuring its outline. - The particles contain serotonin, histamine, and heparin.  Slightly phagocytic and collect at infection sites.  Produce about 50% of histamine in blood and play a role in allergy control. Lifespan  Few hours - few days. Non-granular Leukocytes Lymphocytes  Most numerous of non-granular  15-17um diameter  A few lysosomal granules may be present  Nucleus that nearly fills the cell, leaving a thin rim of cytoplasm.  Circulate through spleen, thymus, lymph nodes, and diffuse lymphoid tissue.  Mount an immune response by direct cell attack or via antibodies. Lifespan  Hours - years. Monocytes  “Macrophages” of blood  On passing through capillary wall, they enter loose CT and become tissue macrophages  Spherical and large  14-24um diameter  Large bean-shaped nucleus  Cytoplasm contains a few lysosomal granules Lifespan  Months Platelets  Fragments of cytoplasm from megakaryocytes (giant cells in red bone marrow). Thrombocytes  Biconvex disks  2-4 μm diameter.  Concentration in blood ranges from 200,000-400,000/mm3.  Remain in peripheral blood for ~ week before removed in the lungs and spleen by phagocytosis.  Function in sealing small tears in blood vessels and in blood clotting. Lifespan  5 - 10 days. Downloaded by Moutia Chaouk ([email protected])  lOMoARcPSD|34309248 ANAT2241 – HISTOLOGY: BASIC AND SYSTEMATIC Types of Skeletal Muscle Fibers: Red, White, Intermediate Muscle Red Fibres  Small with much myoglobin (oxygen transporting proteins that resemble haemoglobin)  Muscle cells allow locomotion, constriction and pumping movements by changing their length and  Many mitochondria, oxidative enzymes developing tension  Represent slow twitch fibers adapted to slow repetitive contractions White Fibres  Large, less myoglobin, fewer mitochondria, poor in oxidative enzymes  Represent fast twitch fibers adapted to rapid short lived forces. Intermediate  Features of both types. fibres  Most muscles have a mixture of the 2 types Light Microscopy of Skeletal Muscle Fibers  Mainly composed of longitudinal arrays of cylinder- shaped myofibrils,  1-2μm diameter.  Extend entire length of cell, packed so densely that nuclei and cytoplasm are pushed to periphery  The ordered parallel arrangement of myofibrils is responsible for cross-striations (light/dark banding)  Dark bands A bands (anisotropic with polarized light)  Light bands I bands (isotropic). Structure  The centre of each A band is occupied by a pale area, the H band, which is bisected by a thin M line.  Each I band is bisected by a thin dark line, the Z disc (Z line).  The region of the myofibril between 2 successive Z disks, is a sarcomere, (2.5 μm long/the contractile unit of skeletal mm fibers). Ultrastructural (EM) Organization of Myofibrils  Parallel, interdigitating thick and thin myofilam