Cartilage & Bone Lecture Notes PDF

ANATOMY | TRANS 1 LE Cartilage & Bone MA. CARMERIZA BUÑING, MD, FPOGS | Lecture Date (09/...

ANATOMY | TRANS 1 LE Cartilage & Bone MA. CARMERIZA BUÑING, MD, FPOGS | Lecture Date (09/29/2023) | Version 2 02 OUTLINE → Ex. Ear, nose, walls of the respiratory tract Guides development and growth of long bones I. Cartilage VII. Bone Classification → Ex. Endochondral ossification A. Definition A. Histologic classification B. Characteristics B. Macroscopic or Gross D. COMPONENTS C. Functions classification Cartilage is also a connective tissue, D. Components VIII. Bone Architecture It is composed of cells and predominantly of ECM II. Types of Cartilage A. Architecture of long A. Hyaline bones B. Elastic B. Architecture of lamellar C. Fibrocartilage bones III. Cartilage Formation, IX. Histologic Preparations Growth, & Repair A. Ground bone A. Chondrogenesis B. Decalcified bone B. Cartilage growth X. Bone Formation C. Cartilage regeneration A. Intramembranous & repair ossification IV. Bone B. Endochondral A. Definition and ossification components XI. Epiphyseal plate B. Functions XII. Bone Growth, Remodeling, V. Bone surfaces & Repair A. Periosteum A. Bone growth B. Endosteum B. Bone remodeling Figure 1. Hyaline cartilage. C - chondrocytes, P - perichondrium, M - VI. Bone Cells C. Bone repair matrix[Mescher, 2018] A. Osteoblasts XIII. Clinical Application EXTRACELLULAR MATRIX (ECM) B. Osteocytes XIV. Review Questions Composed of: C. Osteoclasts XV. References → Ground substance XVI. Appendix ▪ High concentration of GAGs and densely packed ❗️ Must know 💬 Lecturer 📖 Book 📋 Previous Trans proteoglycans which is responsible for; ▪ Semi rigid consistency → Fibers “CartilagE” SUMMARY OF ABBREVIATIONS ▪ Collagen CT Connective tissue ▪ Elastic ECM Extracellular matrix GAGs Glycosaminoglycans SUBDIVISIONS OF ECM RER Rough Endoplasmic Reticulum Territorial Matrix → Immediately surrounds chondrocytes LEARNING OBJECTIVES → Stains more intensely with hematoxylin (due to higher At the end of the lecture, the students should be able to characterize proteoglycan content) the histology of CARTILAGE and BONE by: Interterritorial Matrix ✔ Describing component parts → Lighter staining (lower proteoglycan content) ✔ Differentiating the 3 types of CARTILAGE as to composition of → Between isogenous groups the intercellular substance, histologic features and functions ✔ Classifying BONE according to morphology CELLS ✔ Explaining the process of formation, growth and repair and 1 Chondroblasts regenerative capacity → Immature cartilage forming cells → Elliptical in shape I. CARTILAGE → Found in the periphery (inner chondrogenic layer) A. DEFINITION → Undergo mitosis and secrete ECM around themselves to Tough, durable form of supporting connective tissue, become chondrocytes characterized by presence of cells embedded in ECM with high concentrations of GAGs and proteoglycans, interacting with 2 Chondrocytes collagen and elastic fibers → Round, mature cells surrounded by ECM, lie within lacunae → May occur singly or in clusters (isogenous groups or ❗ B. CHARACTERISTICS Avascular (no blood vessels) No lymphatic vessels and nerves aggregates) → Synthesize, secrete, and maintain ECM PERICHONDRIUM Nutrition is via diffusion from vascularized outer covering (perichondrium) Comes from greek word peri meaning “around” and chondros meaning “cartilage” C. FUNCTIONS Structure that forms an interface between the cartilage and tissue Allows tissues to bear mechanical stress being supported → Ex. Fibrocartilage found in Intervertebral discs Arise from superficial embryonic 💬 Facilitates bone movements Cartilage has a smooth surface, specifically in the articulating surface of bones, permitting almost friction free movements of Essential for growth and maintenance of the cartilage Connective tissue surrounding cartilage → Outer fibrous layer the joints. ▪ Dense irregular CT (type I collagen fibers), fibroblasts and ▪ Shock absorbing and sliding regions within joints blood vessels ▪ Ex. Synovial joints → Inner chondrogenic layer Forms the framework supporting soft tissues ▪ Blends with the matrix proper LE 2 TG 2 | H. Ong, J. Ong, J. Orduña, K. Orge, J. Oro, L. TE | Sabban & Salanga AVPAA | Vivero PAGE 1 of 12 TRANS 1 Oronce ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS 📖 ▪ Contains chondroblasts Contains mesenchymal stem cells which provide a source for new chondroblasts Figure 2. Components of hyaline cartilage[Lecturer’s PPT] II. TYPES OF CARTILAGE 3 types depending on the content of its matrix, and predominant fibers: → Hyaline: non rigid support → Elastic: support with high flexibility Figure 4. Hyaline cartilage → Fibrocartilage: strength under stress B. ELASTIC CARTILAGE Similar to hyaline cartilage (type II collagen) ECM: Type II Collagen Fibers Surrounded by perichondrium Abundant elastic fibers Dark bundles unevenly distributed “looks dirty” Fewer isogenous groups than hyaline cartilage Fresh elastic cartilage is yellowish color due to containing an abundant network of elastic fibers in addition to collagen type II EXAMPLES Located in areas where both flexibility & support are necessary: → Pinna of ears → External auditory canal → Epiglottis → Cuneiform cartilage of the larynx → Auditory or eustachian tube → Upper respiratory tract Figure 3. Distribution of Cartilage in Adults[Mescher, 2018] A. HYALINE CARTILAGE Most common type of cartilage Forms the temporary skeleton which is gradually replaced by bone ECM: Type II collagen Aggrecan most abundant proteoglycan Chondronectin → Multiadhesive glycoprotein for adherence of chondrocytes to the ECM Homogenous and semi transparent in fresh state “glass-like” appearance → Due to the same refractive index of the collagen fibers and ground substance (giving a blended appearance) Basophilic/ stains blue because of proteoglycans Chondrocytes appear in groups (isogenous aggregate/s) Figure 5. Elastic cartilage. C - chondrocytes, M - matrix, P - EXAMPLES perichondrium[Mescher, 2018] Fetal skeleton Walls of large respiratory passages (nose, larynx, trachea, bronchi) Ventral ends of ribs Articular surfaces of movable joints and Epiphyseal plates* → Don't have perichondrium ▪ Damage to these areas would mean poor regenerative capability and healing ANATOMY Cartilage & Bone PAGE 2 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS C. FIBROCARTILAGE III. CARTILAGE FORMATION, GROWTH AND REPAIR Combination of hyaline cartilage and dense connective tissue A. CHONDROGENESIS → Presence of fibroblasts Chondrogenesis: Formation of cartilage ▪ Due to being a combination of hyaline cartilage and dense connective tissue Abundant type I collagen than type II, arranged either in regular or irregular configuration → Type I collagen fibers helps in withstanding tensile forces → Reason why one of the functions of cartilage is to bear mechanical stresses Less proteoglycan (stains pink) Minimal ground substance Few isogenous groups → If present, isogenous groups can be seen as aligned Figure 8. Chondrogenesis[Mescher, 2018] aggregates 1. Rounding up of mesenchymal cells The relative scarcity of proteoglycans makes the matrix of → Cartilage comes from mesenchyme. During fibrocartilage more acidophilic than that of hyaline or elastic chondrogenesis, there will first be rounding up of cartilage mesenchymal cells and condensation No perichondrium 2. Mitosis, chondroblasts → Nutrition comes via diffusion from blood vessels or synovial → Undergoes mitosis and differentiation into chondroblasts fluids and not from the perichondrium 3. Separated from one another and would reside in the EXAMPLES lacunae Intervertebral discs → These secrete the matrix among themselves and Attachments of certain ligaments become trapped in the lacuna and become separated Pubic symphysis from each other and become chondrocytes. 4. Continuous multiplication within lacunae → There will be continuous matrix secretion and mitosis, eventually resulting in formation of new cartilage The dividing cells are typically called chondroblasts and chondrocytes when proliferation has ceased; both have basophilic cytoplasm rich in RER for collagen synthesis. B. CARTILAGE GROWTH Interstitial growth → Mitotic division of pre-existing chondroblasts → Can be found in epiphyseal plates, articular cartilage → In cartilages with no perichondrium Appositional growth → Differentiation of new chondroblasts from the perichondrium → more important in postnatal development Figure 6. Fibrocartilage. C - chondrocytes, M - matrix, D - Dense connective tissue[Lecturer’s PPT] Figure 9. Cartilage growth[Lecturer’s PPT] C. CARTILAGE REGENERATION AND REPAIR Slow, often incomplete (in adults) Generally poor due to avascularity Depends on perichondrium → Optimum nutrition depends on perichondrium, if there is no perichondrium, regeneration and repair will result in a much slower and poorer capability IV. BONE A. DEFINITION AND COMPONENTS Bone is a specialized type of connective tissue characterized by its rigidity and hardness Comprised of the following components: Matrix (Inorganic, Organic) Cells (Osteocytes, Osteoblasts, Osteoclasts) Figure 7. Isogenous groups of fibrocartilage. C - chondrocytes, D - dense connective tissue, M - matrix[Mescher, 2018] ANATOMY Cartilage & Bone PAGE 3 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS B. FUNCTIONS B. ENDOSTEUM Provides structural support and protection Internal surface of bones/trabeculae → Giving shape & form to the body Single row of bone lining cells, osteoblasts, osteoclasts & Permit movement progenitor cells → Insertion of muscles Serves as a storage for minerals → Ex: Calcium Contains bone marrow → Myeloid tissue = bone cell precursors MATRIX ORGANIC PORTION Mainly type I collagen fibers → Stain pink with eosin Minimal ground substance: → Proteoglycans → Glycoproteins → Osteonectin → Osteocalcin → Phosphatases ▪ Components are important for binding collagen, calcium, calcification INORGANIC PORTION 50% of dry weight of bone Calcium hydroxyapatite (most abundant) Calcium phosphate (significant amount) Figure 11. Endosteum[Mescher, 2018] Other ions: → HCO3- VI. BONE CELLS → Citrate A. OSTEOBLASTS → Mg2+ Origin: Mesenchymal stem cells → K+ Exclusively at the surface of the bone matrix → Na+ Single layer of Cuboidal cells V. BONE SURFACES → Inactive form: Bone lining cells ▪ Flattened with heterochromatic nuclei A. PERIOSTEUM → Active form: Osteoblasts are Cuboidal or columnar in Double layer of CT surrounding outer bone surface shape with basophilic cytoplasm Similar to perichondrium Functions: → Well vascularized → Absent at articular surfaces LAYERS OF PERIOSTEUM 📖 → Secrete OSTEOID (Organic bone matrix) Osteoid: located between the osteoblast layer and pre existing bone matrix Outer fibrous → Synthesize osteocalcin and alkaline phosphatase in → Dense CT most type I collagen membrane- enclosed matrix vesicles → Small blood vessels, collagen bundles, fibroblasts Inner osteogenic → Osteoprogenitor cells 📖 → Formation of hydroxyapatite crystals The first visible step in calcification → Mineralization of osteoid → Osteoblasts → Osteoclasts → Bone lining cells (inactive osteoblasts) Perforating/Sharpey fibers → Bundles of periosteal collagen fibers that act like a glue to bind periosteum to the bone Figure 12. Photomicrograph of developing bone. M - mesenchyme, Ob - osteoblast, Os - osteoid, B - bony matrix, Oc - osteocyte[Mescher, 2018] B. OSTEOCYTES Almond shaped cells containing long processes Differentiated osteoblasts surrounded by matrix enclosed singly within lacunae Figure 10. Perforating fibers of the periosteum[Mescher, 2018] Communicate with one another via long cytoplasmic processes that contain gap junctions that aid in the transport of nutrients ANATOMY Cartilage & Bone PAGE 4 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS Lined with dendritic processes within canaliculi (tiny channels where dendritic processes rest) Functions: → Maintain the bone matrix → Role in transport of nutrients between blood & bone, calcium homeostasis → Detection of mechanical stresses to direct bone remodeling ▪ Mechanostat: network of dendritic processes extending from osteocytes ▪ Monitors areas where loading has increased or decreased ▪ Signals cells to adjust ion levels and maintain adjacent matrix ▪ Bone density can be increased with mechanical stimulation Figure 15. Osteoclasts[Lecturer’s PPT] of bone cells Figure 13. Osteocytes with osteoblasts[Lecturer’s PPT] Figure 16. Schematic of osteoclast[Mescher, 2018] Osteoclasts circumferential sealing zone → Integrins tightly bind the cell to the bone matrix. → The sealing zone surrounds a ruffled border of microvilli and other cytoplasmic projections close to this matrix. ▪ The sealed space between the cell and the matrix is acidified to ~pH 4.5 by proton pumps in the ruffled part of the cell membrane and receives secreted matrix metalloproteases and other hydrolytic enzymes. → Acidification of the sealed space promotes dissolution of hydroxyapatite from bone and stimulates activity of the protein hydrolases, producing localized matrix resorption. ▪ The breakdown products of collagen fibers and other polypeptides are endocytosed by the osteoclast and further degraded in lysosomes, while Ca2+ and other ions are released directly and taken up by the blood. Figure 14. Osteocytes of osteon[Mescher, 2018] C. OSTEOCLASTS Large, motile, multinucleated, vacuolated cells with, frothy cytoplasm Derived: monocyte-macrophage cell line Figure 17. Photomicrograph of osteoclasts[Lecturer’s PPT] Lie in depression in bone surfaces (resorption bay/ cavity/ VII. BONE CLASSIFICATION Howship lacunae) A. HISTOLOGIC CLASSIFICATION Ruffled border: part of cell membrane facing the site of bone WOVEN OR IMMATURE OR PRIMARY BONE resorption Function: First bone deposited → Secrete lysosomal enzymes to dissolve hydroxyapatite and Osteocytes and collagen fibers randomly arranged digest matrix proteins that will lead to bone resorption Less mineralized than lamellar bone → Osteoclast activity is inhibited by calcitonin (thyroid gland) and Examples activated by parathyroid hormone → Bone tissue in embryonic development → Bone tissue in fracture repair ANATOMY Cartilage & Bone PAGE 5 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS LAMELLAR OR MATURE OR SECONDARY BONE Replaces most woven bone Deposited in layers or lamellae Better mineralized than woven bone B. MACROSCOPIC / GROSS CLASSIFICATION: MATURE COMPACT OR CORTICAL BONE Solid portion covering the exterior of bones and forming the shaft of the long bones 80% of total bone mass CANCELLOUS (SPONGY / TRABECULAR / MEDULLARY) Interior of bone Covered by endosteum 💬 Labyrinth of bony spicules or trabeculae Trabeculae serve as a supporting structure that provides considerable strength without increasing the bone’s weight Intervening spaces filled with loose connective tissue or marrow 20 % of total bone mass Figure 19. Structure of typical long bone[Ross & Pawlina, 2011] B. ARCHITECTURE OF LAMELLAR BONES Osteon or haversian system → Concentric lamellae (4 to 20) arranged around a central or 💬 haversian canal containing blood vessels and nerves Looks like a tree trunk or cinnamon roll Cement line → Outer boundary of each osteon Perforating / Volkmann canal → Transverse canal that allows each osteon to communicate with each other Lacunae → Spaces located between successive lamellae → Contain single osteocyte → Interconnected by canaliculi Canaliculi Figure 18. Spongy bone[Lecturer’s PPT] → Narrow tunnels between lamellae containing long dendritic processes of osteocytes VIII. BONE ARCHITECTURE External (outer) circumferential lamellae A. ARCHITECTURE OF LONG BONES → Not associated and scattered along osteons Epiphysis → Located immediately beneath the periosteum → Knob-like structure at both ends Internal (inner) circumferential lamellae → Spongy bone covered by a thin rim of compact bone → Located around the marrow cavity Diaphysis Interstitial lamellae → Shaft of the long bone → Found in between osteons → Mostly composed of compact bone → Remnants of partially destroyed osteons during bone growth → Hollow center lines with thin region of spongy bone that and remodeling contains the marrow Metaphysis → Flared region between diaphysis and epiphysis Epiphyseal plate → Hyaline cartilage that separates the epiphysis and metaphysis → Region of endochondral bone formation ( it is needed for bone elongation ) Figure 20. Osteon. CC - central canal, L - concentric lamellae, O - osteocyte, I - interstitial lamellae[Mescher, 2018] ANATOMY Cartilage & Bone PAGE 6 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS Figure 24. Decalcified bone[Lecturer’s PPT] Figure 21. Osteon diagram[Mescher, 2018] Figure 22. Volkmann canal[Lecturer’s PPT] Figure 25. (Top) Ground bone, (Bottom) Decalcified bone[Lecturer’s PPT] IX. HISTOLOGIC PREPARATIONS X. BONE FORMATION A. GROUND BONE For both intramembranous and endochondral ossification, woven Unpreserved bone (no chemical added) bone is formed first and soon replaced by stronger lamellar Bone is ground to thinness where light can be transmitted bone No preservation: no cells or organic matrix A. INTRAMEMBRANOUS OSSIFICATION General organization that can be seen: lamellae, lacunae, Osteoblasts differentiate directly from mesenchyme canaliculi, inorganic matrix Examples → Flat bones of skull → Fontanelles → Mandible & maxilla → Clavicle Figure 26. Mesenchymal cells with ossification center[Lecturer’s PPT] 1. Bone formation starts with the mesenchymal cells cluster or condensation of mesenchymal cells with simultaneous Figure 23. Photomicrograph of ground bone[Mescher, 2018] formation of ossification centers B. DECALCIFIED BONE Cells are fixed and inorganic matrix is removed by decalcification Periosteum and organic matrix cells are assessed in great detail Lamellae and inorganic matrix are difficult to distinguish ANATOMY Cartilage & Bone PAGE 7 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS Figure 30. Early stages of endochondral ossification[Mescher, 2018] 1. Bone forms from a hyaline cartilage model Figure 27. Formation of osteoblasts and osteocytes[Lecturer’s PPT] 2. Hyaline cartilage then undergoes degeneration followed by the formation of a periosteal bone collar around the diaphysis 2. Mesenchymal cells will then differentiate into osteoblasts a. Bone collar formation impedes diffusion of oxygen and a. Osteoblasts then secrete bony matrix around themselves nutrients resulting in further cartilage degeneration and b. The osteoblasts would then be trapped within a lacunae, death of chondrocytes. becoming osteocytes 3. Primary ossification center is formed in the diaphysis i. Osteocytes deposit calcium and other mineral salts that a. Penetrated by blood capillaries which brings in the harden the forming bone matrix osteoprogenitor cells b. Osteoprogenitor cells secrete bone matrix or osteoid resulting in the formation of the woven bone. 4. At the time of birth, secondary ossification center forms in epiphysis a. Woven bone in the primary ossification center will be replaced by a developing compact bone enclosing a medullary cavity Figure 28. Trabecular bone with blood vessels[Lecturer’s PPT] 3. Continuous deposition of bony matrix will eventually form the bony spicules or trabecular bone a. Trabeculae is inundated with blood vessels b. Formation of the periosteum on the surface of the bone Figure 31. Later stages of endochondral ossification[Mescher, 2018] 5. During childhood, primary and secondary ossification centers are separated by an epiphyseal plate or growth plate a. Growth plate is responsible for bone elongation 6. Epiphyseal plates ossify and epiphyseal lines are formed a. Ossification centers fuse when the full stature of the person is achieved. i. Around 20 yrs old for males and earlier for females Figure 29. Compact bone and spongy bone[Lecturer’s PPT] XI. EPIPHYSEAL PLATE (GROWTH PLATE) Responsible for bone elongation 4. Further deposition of bony matrix would result in the trabeculae Made up of five overlapping zones becoming the primary bone which is then replaced by a more → Typical order is from diaphysis to epiphysis stronger compact bone a. Blood vessels that invaded the trabeculae would condense and become the red marrow B. ENDOCHONDRAL OSSIFICATION Preexisting hyaline cartilage is used as a template Important for the formation of long and short bones Examples → Bones of limbs → Pelvis → Vertebral column Figure 32. Photomicrograph of long bone and its epiphyseal plate[Lecturer’s PPT] ANATOMY Cartilage & Bone PAGE 8 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS XII. BONE GROWTH, REMODELING, & REPAIR A. BONE GROWTH Always appositional → Laid down on preexisting bone or cartilage Interstitial growth impossible → Presence of ossified matrix does not allow osteocytes to divide or secrete additional matrix B. BONE REMODELING Continuous process of bone resorption & formation throughout life for growth or to mobilize calcium Ensures that bone tissue remains plastic and capable of adapting its internal structure in the face of changing stresses Maintains bone’s general shape while increasing its mass Example of bone remodeling are braces → Consistent traction is applied on the teeth resulting in bone remodeling → Removal of traction would affect the alveolar bone with the deposition of new bone on one side and resorption of bone on Figure 33. Zones of the epiphyseal plate[Mescher, 2018] the other side Resting zone or zone of reserve cartilage → Where “normal” hyaline cartilage resides with typical chondrocytes Proliferative zone or zone of proliferating cartilage → Isogenous groups of chondrocytes actively divide and form columns of stacked cells parallel to long axis of bone Hypertrophic cartilage zone or zone of maturation & hypertrophy → Characterized by swollen chondrocytes with accumulated glycogen in cytoplasm Calcified cartilage zone → Loss of chondrocytes by apoptosis and calcification of cartilage matrix by hydroxyapatite crystals Ossification zone → Where bone tissues first appear ▪ Blood vessels and osteoblasts invade lacunae of chondrocytes ▪ Bone tissue deposited on calcified cartilage Figure 36. Bone remodeling[Lecturer’s PPT] 1. Osteoclasts (periosteum & endosteum) resorb bone at surface Osteoclasts attach themselves at the site of bones to be absorbed 2. Tunnel into compact bone forming resorption canal/cavity Formation of cavity (Howship’s lacunae or resorption base) by the osteoclasts 3. Osteoblasts invade the cavity and enter newly formed tunnel and line walls 4. Osteoblasts secrete osteoid in cyclic manner forming lamellae Osteocytes trapped in lacunae 5. Cavity filled up by lamellae until narrow central canal remains Remains of partially resorbed osteons become interstitial Figure 34. Schematic diagram of epiphyseal growth plate[Lecturer’s PPT] lamellae Figure 35. Photomicrograph of epiphyseal plate[Lecturer’s PPT] ANATOMY Cartilage & Bone PAGE 9 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS C. BONE REPAIR XIII. CLINICAL APPLICATION This happens because bone is vascular Bones take 6 to 8 weeks to completely heal Figure 37. [Left] Fracture hematoma forms, [Right] Figure 39. Comparison between normal bone and osteoporotic Fibrocartilaginous (soft) callus forms[Mescher, 2018] bone[Lecturer’s PPT] 1. Bone repair begins with a fracture hematoma Osteoporosis Removed by circulating macrophages → Common among the elderly 2. Fracture hematoma is converted into a procallus → Results from the imbalance in bone turnover Rich in collagen and fibroblasts ▪ Bone resorption is much greater than bone formation Will be invaded by blood vessels for nourishment and aid in ▪ Resulting in calcium loss and reduced mineral content bone repair → Bone is brittle, fragile, and easily gets fractured. → Lack of exercise can result in lower bone density due to the lack of mechanical stimulation by the osteocyte or mechanostats. Figure 40. (Left) Osteoarthritis, (Right) Rheumatoid arthritis[Lecturer’s Figure 38. [Left] Hard (bony) callus forms, [Right] Bone is PPT] remodeled[Mescher, 2018] Osteoarthritis of the knee (left) 3. Soft procallus will become hard callus → Also known as wear and tear arthritis because it develops Hard callus would then become the primary bone or woven as the cartilage in the joints wear down bone → As the cartilage in the joins are being damaged, this allows Osteoblasts transform the callus into bone the bone to rub against each other, resulting in joint 4. Woven bone is then replaced by the compact bone at break stiffness, pain and swelling site Tthe knees are markedly swollen, same as in the knuckles of the hands → Usually common in the elderly but may be seen in younger populations as well Rheumatoid arthritis (right) ANATOMY Cartilage & Bone PAGE 10 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS XIV. REVIEW QUESTIONS 10. What is the primary role of parathyroid hormone (PTH) in calcium regulation? 1. In what type of cartilage is the perichondrium not present? a. To inhibit osteoclast activity a. Hyaline cartilage b. To lower blood calcium levels b. Elastic cartilage c. To stimulate osteoblasts c. Fibrocartilage d. To indirectly stimulate osteoclasts and elevate blood calcium d. all of them levels 2. In what type of cartilage is type II collagen present? a. Hyaline cartilage ANS: 1. C. Hyaline and elastic cartilage have the perichondrium. b. Elastic cartilage 2. D c. Fibrocartilage 3. A d. all of them 4. B. All cartilage forms from embryonic mesenchyme in the process of 3. What is the main location of elastic cartilage? chondrogenesis a. External ear 5. A. The poor capacity of cartilage for repair or regeneration is due in part to b. Pubic symphysis the avascularity of this tissue. c. upper respiratory tract 6. C. Bones do not absorb lipids 7. C d. intervertebral disc 8. C 4. Which cell forms cartilage? 9. B a. Myeloid cell 10.D b. Embryonic mesenchyme c. Osteocyte XV. REFERENCES d. Osteoclast 2025. (2021). Bone and Cartilage. [Transcription]. 5. Why does cartilage have a poor capacity for repair? Buning, C. (2021) Bone and Cartilage. [Lecture Recording], a. Because it is avascular Mescher, A. (2018). Junquiera’s Basic Histology: Text and Atlas b. Because it is anucleate (15th Edition). McGraw-Hill Education. c. Cartilage has a good capacity for repair Ross, M. & Pawlina, W. (2011). Histology: A Text and Atlas with 6. Which of the following is not a function of bones? Correlated Cell and Molecular Biology. Lippincott Williams & a. Support body Wilkins. b. Protect internal organs c. Absorb lipids d. Ca2+ ion reservoir 7. What cells differentiate from osteoprogenitor cells and secrete components of the initial matrix called osteoid? a. Osteocyte b. Osteoclast c. Osteoblast 8. What is the initial stage of bone repair after a fracture or injury? a. Formation of hard callus. b. Activation of osteocytes. c. Activation of periosteal fibroblasts to produce a soft, fibrocartilage-like callus. d. Formation of lamellar bone. 9. Where do primary ossification centers typically form in fetal long bones? a. In the epiphyses b. In the diaphyses c. In the growth plate ANATOMY Cartilage & Bone PAGE 11 of 12 ANATOMY | LE 2 Cartilage & Bone | Ma. Carmeriza Buñing, MD, FPOGS XVI. APPENDIX Table 1. Features of cartilage types Table 2. Summary of bone types and their organization ANATOMY Cartilage & Bone PAGE 12 of 12