Cartilage and Bone Anatomy PDF

BONES ANATOMY CARTILAGE & BONE DR ZAHIRRAH BEGAM BINTI MOHAMED RASHEED Department of Diagnostic Craniofacial and Bioscience  LECTURE CONTENTS 01 02 CARTILAGE BONE ❖ Characteristics and ❖ Characteristics composition...

BONES ANATOMY CARTILAGE & BONE DR ZAHIRRAH BEGAM BINTI MOHAMED RASHEED Department of Diagnostic Craniofacial and Bioscience  LECTURE CONTENTS 01 02 CARTILAGE BONE ❖ Characteristics and ❖ Characteristics composition ❖ Functions ❖ Functions ❖ Histology ❖ Cartilage formation, ❖ Classification growth, & regeneration ❖ Structure ❖ Classification ❖ Blood supply ❖ Bone remodelling CARTILAGE & BONE The 4 basic types of tissue: Epithelium Connective tissue o Connective tissue proper o Cartilage o Bone o Blood Muscle tissue Nervous tissue 01 CARTILAGE  Characteristics o Tough o Flexible o Avascular & aneural → incapable to repair itself when fracture o Firm, rubbery, resilient o Consist of cells & fibres embedded in firm, gel-like, unmineralized intercellular matrix o Nutrition is by diffusion from: Perichondrium Synovial fluid in joint cavities  Cartilage Composition Extracellular matrix Cells (ECM) Chondrogenic cells Differentiate Amorphous/ ground Fibres substance Chondroblast Mature Collagen (mainly type Mucopolysaccharides/ Elastic fibres GAG/ proteoglycans/ II) Chondrocytes glycoproteins Strength Flexibility & elasticity  Perichondrium o Sheath of dense irregular connective tissue that surrounds cartilage (except fibrocartilage) o Form interface between cartilage & tissues supported by cartilage o Contain blood vessels, nerves, & lymphatic vessels o Provide nutrition to cartilage by diffusion o Important for appositional growth & maintenance of cartilage o Have 2 layers: ❑ Outer fibrous layer: connective tissue fibres, fibroblast, blood vessels ❑ Inner cellular layer: contains chondrogenic cells → differentiate to chondroblasts Contains blood vessels, nerves, & lymphatic vessels Elliptical shape Long axis parallel to surface In matrix lacunae Isogenous groups of up to 8 cells (cell nest)  Perichondrium Functions o Prevent permanent distortion due to mechanical stress o Bear mechanical stress, support soft tissues o Provide sliding surface for joints o Facilitate bone movements (shock-absorber & sliding area) o Development & growth of long bones (before & after birth) Cartilage Formation -Chondrogenesis Lose their Chondrocytes Form aggregations and Entrapped in the surrounded by cytoplasmic differentiate into ECM they produce matrix → form cell processes, become chondroblast → chondrocytes rounded and produce nest/ isogenous ECM aggregates Cartilage Growth a) Appositional growth ❑ Formation of new chondrocytes from inner part of surrounding perichondrium (differentiation) ❑ Leads to increase in width ❑ Starts later than interstitial growth and continues through adolescence b) Interstitial growth ❑ Growth within tissue ❑ Formation of new chondrocytes within pre-existing chondrocytes by division ❑ Leads to increase in length ❑ Significant during early phases of cartilage formation (childhood and adolescents) → when cartilage is young and pliable Cartilage Regeneration 1. Damage cartilage undergoes slow and incomplete repair 2. Perichondral cells invade the injured / damaged area → generate new cartilage 3. Usually slow and often incomplete (except in young children) 4. If extensively damaged, perichondrium produces scar of dense CT (instead of forming new cartilage) 5. Poor regenerative capacity is due to its avascular in nature Classification of Cartilage Hyaline Elastic Fibrocartilage cartilage cartilage  (i) Hyaline Cartilage o The most common form of cartilage o Translucent, white, resilient o Found in nearly all foetal skeleton o Covered by perichondrium (except in articular cartilage in joints) o Location: Articular end of bone (movable, synovial joints) Costal cartilages Cartilages of nose, larynx (thyroid, cricoid, arythenoid), trachea, bronchi Epiphyseal plate of growing long bone (endochondral ossification) ❑ Function: provide flexibility & support, reduces friction & absorb shock Histology of Hyaline Cartilage o Lined by perichondrium ▪ Dense CT ▪ Inner cellular layer (chondrogenic perichondirum) ▪ Outer fibrous layer o Cells ▪ Chondrocytes in lacuna ▪ 2-4 cells arranged in cluster as isogenous groups ▪ Surrounded by amorphous cartiloginous matrix o Matrix ▪ Ground substance ▪ Collagen fibres – type II (predominant), type VI & IX ▪ Firm, hydrated gel of proteoglycans & structural glycoproteins → basophilic ▪ Appear amorphous & clear – ground substance & collagen have P = perichondrium similar refractive index M = matrix C = chondrocytes in o Different regions of ECM: lacunae ▪ Capsular matrix ▪ Territorial matrix ▪ Inter-territorial matrix Matrix around chondrocytes Outer region that occupies spaces Matrix surrounds the between isogenous group isogenous groups  Clinical Correlations o Hyaline cartilage is prone to calcification during ageing o Limited ability to repair o Osteoarthritis ▪ Related to ageing & injury to cartilage ▪ Chronic joint pain & deformity o Affect weight-bearing joints (such as hip & knee) Joint space Cartilage Cartilage breaking narrowing loss down Articular cartilage Meniscus Normal joint space  (ii) Elastic Cartilage o Yellowish o Not calcified during ageing process o Location: External ear (auricle, pinna) Walls of external acoustic meatus Eustachian tube (auditory tube) Larynx cartilages (epiglottis, corniculate, cuneiform cartilage)  Histology of Elastic Cartilage o Lined by perichondrium o Chondrocytes in lacunae – seen as isogenous groups, abundant & larger than HC o ECM: ▪ Collagen fibres type II ▪ Dense network of fine branching of elastic fibres ▪ Less susceptible to degeneration  (iii) Fibrocartilage o Opaque o Resilient o Location: ▪ Articular disc of Temporomandibular Joint (TMJ), sternoclavicular joint, wrist joint ▪ Menisci of knee joint ▪ Attachments of certain tendons & ligaments o Function: ▪ Resistance to traction force ▪ Provide great tensile strength  Histology of Fibrocartilage o Absence of perichondrium o Chondrocytes (single / isogenous aggregates) arranged axially / parallelly in long rows separated by coarse collagen fibres type I (dense regular CT o ECM: ▪ More acidophilic – due to richer collagen type I ▪ Firm, dense matrix ▪ Type II collagen ▪ Type I collagen fibres (thick, coarse bundles) Comparisons between cartilages Cartilage Hyaline cartilage Elastic cartilage Fibrocartilage Cells Chondrocytes & Chondrocytes & Chondrocytes & chondroblasts chondroblasts fibroblasts Chondrocytes Mostly in groups Mostly in groups Mostly small & sparsely (isogenous) (isogenous) arranged in parallel columns/ rows ECM Type II collagen Type II collagen & elastic Type II and Type I fibres collagens Perichondrium (except articular cartilage surface) Growth A&I A&I I Calcification (endochondrial (fibrocartilaginous callus ossification, ageing) calcification in bone repair) Comparisons between cartilages Locations URTI, costal cartilage, Epiglottis, larynx, ear Articular disc, IV-disc, long bones pubic symphysis, insertion of tendons & ligs Functions confer shape & Confer shape & elasticity Resistance to flexibility (URTI) compression, cushioning cartilage model for & tensile strength bone growth in foetus smooth surface for joint movement 02 BONE  Characteristics o Highly vascularized o Highly mineralised o Has nerve supply o Tough & resilient o Covered by periosteum ▪ 1 layer of dense CT ▪ 2 layers of: Outer fibrous layer Inner cell-rich layer  Functions o Framework to give form and support for the body o Provide areas for attachment of muscles & ligaments o Lever for movements in locomotion o Protects the vital organ (viscerae) of the body o Production of blood cells by marrow (haematopoiesis) o Serve as a storage site for minerals such as calcium & phosphate ions o Transmission of weight & force o Sound transduction in middle ear (auditory ossicles)  Bone Composition Cells Intercellular substance Mesenchymal cells Osteogenic cells Organic (1/3) Type I collagen fibres, Differentiate into amorphous muco- polysaccharide Osteoblast Inorganic (2/3) Transform into Hydroxyapatite: calcium, phosphate Osteocytes ions Others Blood vessels, Osteoclast lymphatics, nerves  Histology of Bone Cells Osteoprogenitor Derived from mesenchymal Resting cells cells stem cells Undergo mitosis and transform into osteoblasts Lie in innermost surface of periosteum & endosteum Found during normal growth & bone remodelling Periosteum with osteoprogenitor cells Osteoblasts Differentiated from Bone forming cells osteoprogenitor cells Low columnar cells Lie on periphery of newly-formed bone tissue Secrete organic components bone matrix (type I collagen fibres, PGs, GPs such as osteonactin) Involved in calcification of bone matrix Osteocytes Transformed from osteoblast Mature bone cells Oval shaped Lie in lacuna Enclosed by calcified bone matrix Has cytoplasmic processes lying in canaliculi Maintain bone matrix Osteoblast Osteocytes in lacunae Osteoprogenitor cells Osteoclast Derived from monocyte- Large (approx. 40-100um in diameter) macrophage cell line Multinucleated cells (with 15-20 closely packed nuclei) Responsible for bone resorption Lie in resorption bay called Howship’s lacunae  Bone Classification 1. SHAPE Long bone 4. STRUCTURE Short bone Compact/ cortical bone Flat bone Cancellous/ spongy bone Irregular bone 5. MATURITY 2. DIVISION Axial skeleton Woven (immature) bone Appendicular Lamellar (mature) bone skeleton 6. OTHERS Sesamoid bone 3. DEVELOPMENT Penumatic bone Accessory bone Intramembranous ossification Endochondral ossification  1. Shape of bone Type Description Example Long bone o Length > breadth & thickness Bones of the o Tubular shape with internal marrow cavity limbs o Diaphysis (long shaft) + 2 epiphysis at ends o Endochondral ossified (except clavicle) Short bone o Length = breadth = thickness Carpals, tarsals o Cuboid shape o Consist of thick spongy bone & marrow enclosed by thin layer of compact bone o Endochondral ossified Flat bone o Resemble sandwich Sternum, ribs, o Spongy bone & marrow lies between 2 layers scapula, most skull bones Irregular o Irregular shape Vertebrae, hip, bone o Do not fit above classification temporal bone o Consist of spongy bone enclosed by thin layer of compact bone  Irregular bone Type Description Example Sesamoid o Nodules of bone found embedded in certain tendons Patella bone o In areas exposed to severe pressure/ friction Pneumatic o Bones with air cavities Maxilla, ethmoid bone o Evagination of mucosal linings of nasal cavities, middle ear, mastoid bone antrum Accessory o Not regularly present Supernumerary bone o Can be found in certain bones that normally ossify from several centres – digit, sutural bone develop when 1 / more centres fail to unite with main bone mass of skull  2. Bone Division Appendicular Axial Bone that are Forms the vertical attached to the axial axis/ centre of the skeleton body Limb bones Skull Upper limb Hyoid bone Lower limb Vertebral column Thoracic cage Girdle bones Pectoral girdle Pelvic girdle  3. Bone Development Development occur in membrane Intramembranous Mesenchymal cells → osteoprogenitor cells → osteoblasts → osteocytes ossification Examples: skull (frontal, parietal), mandible Bone formation in hyaline cartilage model Mesenchymal cells → chondroblast → chondrocytes → form cartilage model Endochondral ossification Chondrocytes dies & replaced by calcified matrix & osteoprogenitor cells → osteoblasts → osteocytes Examples: long bone (except clavicle), short bone Intramembranous ossification Endochondral ossification Mesenchymal cells condensed → develop into chondroblasts. Chondroblast secretes cartilage ECM → producing cartilage model consists of hyaline cartilage. Perichondrium develop around the model Chondroblasts → chondrocytes. Interstitial growth & appositional growth happen. Cartilage ECM calcified. Artery penetrates perichondrium stimulate cells in the perichondrium to become osteoblasts. Perichondrium form bone known as periosteum. Periosteal capillary induce the growth of primary ossification center. Osteoblasts deposit bone ECM → spongy bone. Primary ossification spread on both ends of the bone. When branches of the epiphyseal artery enter the epiphyses, secondary ossification centers develop. Bone formation same as primary ossification. No medullary cavities yet. Osteoclasts break down some of the newly formed spongy bone trabeculae → cavity known as medullary (marrow) cavity, in the diaphysis (shaft). The wall of the diaphysis is replaced by compact bone. Epiphyses ossify. Hyaline cartilage remains as articular cartilage and epiphyseal plates  4. Bone Structure Compact bone Spongy bone Uniform, consist of Haversian system Irregular shape, consist of network of bony trabeculae & spicules with intervening bone marrow cavities Hard & dense, resemble ivory Lower density Lamellae in circular pattern Lamellae in parallel pattern In outer part of bone (cortical bone) In inner core of bone (medullary bone) Protection & support Support, blood cell production  5. Bone Maturity Woven (immature) bone Lamellar (mature) bone Irregular arrangement Regular arrangement Interlacing arrangement of collagen fibres, Made up of regular layers (lamellae) of calcified interstitial lamellae without organised pattern substance / bone matrix In developing fetus In adults Structure of Long Bone Structure Description Diaphysis (shaft) Thick-walled tube, mainly compact bone Inner/ central medullary cavity – filled with bone marrow (yellow/red marrow) External surface covered by periosteum Site of primary ossification centre Epiphyses (2 ends) Wider than shaft Mainly cancellous bone (spongy bone) Articular surfaces covered by articular cartilage Site of secondary ossification centre Metaphysis Transitional zone between diaphysis & epiphysis Occupied by cartilaginous epiphyseal disc in growing age Growth zone of long bone Structure of osteoid tissue i. Osteons ii. Associated lamellae iii. Volkmann’s canal iv. Marrow cavity v. Endosteum vi. Periosteum i. Osteon ❑ Is a structural unit of a compact bone ❑ Consist of: o Haversian canal Oval/circular canal Parallel to long axis of bone Contain blood vessels & nerve o Haversian lamellae Concentric layers of bone tissue around canals o Lacuna Small cavities occupied by osteocytes Uniformly spaced along lamellae o Canaliculi Small narrow spaces containing osteocyte processes Radiating fine passages from lacunae Provide connection between Haversian canal & lacunae o Cement line Thin, dense external bone layer that surrounds each osteon ii. Lamellae Lamellae Description Circumferential lamellae Lie parallel with outer & inner lining of bone Outer CL – beneath periosteum, surround outside of entire compact bone Inner CL – beneath endosteum, innermost layer of compact bone Haversian lamellae Arranged in concentric pattern around Haversian canal Interstitial lamellae Lie between Haversian systems Inner cellular layer Periosteum Interstitial lamellae Outer fibrous layer Inner circumferential Outer circumferential lamellae lamellae Haversian lamellae (concentric lamellae) iii. Volkmann’s canal ❑ Lie obliquely / perpendicularly to Haversian canals ❑ Form connections between 2 Haversian canals ❑ Provide passages for anastomosis of vessels of: ▪ Periosteum ▪ Endosteum ▪ Other Haversian systems Volkmann’s canal  iv. Marrow cavity ❑ Red (haematopoietic) marrow – consist of developing cells, blood sinuses, blood forming tissues ❑ Yellow (fatty) marrow – consist of fat cells Haematopoietic cells Fat cells Bone trabecula  v & vi. Endosteum & Periosteum Functions: ▪ Nutrition of osseous tissues Periosteum ▪ Provide continuous supply of osteoblasts for bone repair/ growth Endosteum Endosteum: A thin layer of CT covering marrow cavity Lines the Haversian canal and all the internal cavities of bone Cover small spicules/ bone trabeculae (spongy bone) that project into marrow cavities Consist of flattened osteoprogenitor cells (osteoblast precursor) Marrow cavities rich in blood sinuses & haematopoietic cells Periosteum: A thick layer of dense CT covering external surfaces of compact bone (decrease with age) Outer fibrous layer Collagen bundles, fibroblasts Attach to tendon, muscles, ligaments Sharpey’s fibres → protrude bone matrix and bind periosteum to bone Inner cellular layer Contain mesenchymal stem cells → osteoprogenitor cells Contain blood vessels Sensitive to pain (periostitis) Histology of growing part of long bone o Epiphyseal plate is the area of elongation in long bone o Epiphyseal closure Complete at age 15-18 years old in female and 18-22 years old in male Longitudinal growth ceases Epiphyseal plate replaced by suture (epiphyseal line / remnant) → diaphysis & epiphysis fuse o 5 zones of epiphyseal cartilage Resting zone – consist of typical hyalin cartilage Proliferative zone – chondrocytes form columns parallel to long axis of bone Hypertrophic zone – contain large chondrocytes Calcified cartilage zone – cartilage matrix becomes calcified & chondrocytes enlarge & become vacuolated → chondrocytes regenerate Ossification zone – endochondral bone tissues appears with blood capillaries Small chondrocytes secure epiphyseal plate to the overlying osseous tissue of epiphysis Produce new chondrocytes via mitosis Chondrocytes are larger and mature. Results in longitudinal growth of bone due to interstitial growth Most chondrocytes are dead due to calcified matrix → restricted nutrient diffusion. Epiphysis Diaphysis Blood Supply of Long Bone Supply epiphysis & metaphysis Supply red bone marrow Enter diaphysis through perforating (Volkmann’s) canal Supply periosteum & outer part of compact bone Branch of large blood supply near bone Enter through nutrient foramen Divide into proximal & distal branches Supply spongy bone & inner part of compact bone Bone Remodelling o Is the ongoing replacement of old bone tissue o Involves: ❑ Bone resorption Removal of minerals & collagen fibres from bone by osteoclast Results in destruction of bone ECM Widening by appositional growth from inner cellular layer of periosteum Lengthening by activity of epiphyseal plate ❑ Bone deposition Addition of minerals & collagen fibres to bone by osteoblasts Results in the formation of bone ECM Occur from inner part of bone To maintain shape of bone Factors affecting bone remodelling 1. Nutrition o Diet – protein o Vitamins – D, C, A, K, B12 o Minerals – calcium, phosphate ions 2. Physical & mental stress 3. Hormone o Parathyroid hormone promotes bone resorption o Calcitonin inhibits bone resorption o Thyroid & pituitary growth hormone (GH) stimulates osteoblast activity & bone matrix synthesis ▪ Lack of GH → pituitary dwarfism ▪ Excess GH → gigantism / acromegaly o Glucocorticoids promote calcium ion resorption from bone, inhibit collagen synthesis in osteoblasts Clinical Correlations 1. Nutritional deficiency o Children – rickets → abnormal bone growth, bone softening o Adult - osteomalacia 2. Physical & mental stress o Osteoporosis – bone resorption > bone formation → bone mass & bone porosity → fracture easily 3. Hormone o Pituitary growth failure → inadequate production of growth hormone → epiphyseal cartilage activity o Pituitary hyperactivity → overproduction of GH Before puberty – gigantism After puberty – acromegaly 4. Marfan syndrome o Hereditary o Excessive cartilage formation at epiphyseal cartilages Fracture healing 1. Formation of fracture heamatoma. Blood circulation stops at the site → bone cells die. 2. Fibroblasts from periosteum invade → produce collagen fibres. Cells from periosteum → chondroblasts & produce fibrocartilage – fibrocartilaginous callus 3. Osteogenic cells → osteoblasts producing spongy bone trabeculae & join the dead portions of the original bone fragments. Fibrocartilage is converted → spongy bone and the callus is called bony callus 4. Final phase. Dead portions of broken bone are resorbed by osteoclasts. Compact bone replaces spongy bone. THANKS! CREDITS: This presentation template was created by Slidesgo, including icons by Flaticon, infographics & images by Freepik