Bones, Joints and Cartilage Notes: Diagrams and Illustrations | Osmosis (2023)

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OBSERVATIONS OBSERVATIONS BONES, JOINTS AND TISSUE SKELETAL SYSTEM ANATOMY & PHYSIOLOGY osms.it/skeletal-system-anatomy-physiology SKELETON BASICS BONE TYPE Axial skeleton ▪ Vertical body skeleton? 80 bones (22 in skull, 33 vertebrae, 24 ribs, 1 sternum) Long bones ▪ Length > width ▪ Humerus, radius, ulna (in arms). metacarpals, phalanges (hands, fingers). femur, tibia, fibula (legs); metatarsals, phalanges (feet, toes) ▪ Mainly responsible for length ▪ 206 bones in skeleton ▪ Divided into axial, appendicular skeleton Appendicular skeleton ▪ Supports limbs. The thoracic girdle (clavicles, shoulder blades) supports the humerus, the pelvic girdle (pelvic bones) supports the thigh. 126 bones (4 in shoulders, 6 arms, 54 arms, 2 hips, 8 legs, 52 feet) Short bones ▪ Equal length, width ▪ Carpal bones (in the wrists). Tarsal bones (ankles) ▪ Supporting arms, legs Figure 48.1 Skeleton overview. OSMOSE.ORG 405

Flat bones ▪ Thin, sometimes curved ▪ Skull bones. scapula, sternum, ribs ▪ Protection of vital organs Sesamoid bones ▪ Embedded in tendons, shaped like a giant sesame ▪ Pisiform bone (in the wrists). patella (knees) ▪ Support, protection, extra strength for tendons Irregular bones ▪ Facial bones. mandible; vertebrae; sacrum, coccyx BONE SURFACE FEATURES Muscle attachment, ligament attachment ▪ Tuberculosis, tubercle: small bumps on bone, serve as points of muscle attachment. large tuberculosis → tuberculosis? deltoid tubercle (in the humerus) ▪ Process: bony prominence. xiphoid process (sternum) ▪ Apex: narrow outline. patellar crest (ilium) Processes ▪ Articular section ▪ Condyle: rounded, articular projection. lateral, medial condyles (femur); epicondyle → elevated part on/above the condyle (lateral, medial epicondyle) ▪ Ramus: arm-like part. mandible (lower jaw) Openings, passages, cavities ▪ Foramen: holes in bone, allow blood vessels/nerves to pass. foramen maximus (in the occipital bone of the skull) ▪ Canal/crotum: tunnels, allow blood vessels/nerves to pass. optic canal (sphenoid bone); external auditory canal (temporal bone of the ear) ▪ Sinuses, cavities: empty spaces in/between bones. nasal cavity, paranasal sinuses ▪ Fossa: depressions where other structures rest. pituitary fossa (sphenoid bone) 406 OSMOSE.ORG Figure 48.2 Types of bones. STRUCTURE OF BONE Cortical/solid bone ▪ Surrounded by periosteum ▪ Contains tubular structures called osteons. connect laterally with Volkmann's canals ▪ Osteon walls made of bone matrix (type I collagen reinforced with hydroxyapatite), produced by osteoblast cells ▪ Some osteoblasts get trapped in bone matrix → mature into osteocytes → repair old/broken bone ▪ Osteoclasts cells secrete enzymes → breakdown of lower bone matrix → releases calcium, phosphate into blood Dada/cancellous bone ▪ Similar material to cortical bone ▪ Looser structure. branched rods called trabeculae ▪ Contains bone marrow, consists of hematopoietic stem cells ("red marrow"), adipocytes/adipocytes ("yellow marrow") ▫ Appendicular bones often contain red marrow at the ends, yellow marrow in the hollow medullary cavity (center ) ▫ Axial bones mainly red marrow

Chapter 48 Musculoskeletal Physiology: Bones, Joints, and Cartilage Figure 48.3 Cross section of bone showing the structure composed of cortical bone and cancellous bone. Cancellous bone contains two types of bone marrow, each made of a different type of cell. FAT osms.it/cartilage WHAT IS FAT? ▪ Strong, flexible connective tissue ▫ Covers part of nose, ears ▫ Provides cushioning between joints ▫ Supports/connects body parts (eg costal cartilage connects ribs to sternum) ▪ Perichondrium: connective tissue that wraps around around cartilage ▫ fibrous connective tissue contains blood vessels ▫ Inner layer contains chondroblasts → secrete proteins that form extracellular matrix ▪ Extracellular matrix: protein fibers (collagen for strength, elastin for flexibility) suspended in thick gel (water, proteoglycan aggregates) ▫ Chondrocytes: chondroblasts (chondroblasts) of the standard ; maintenance, repair of extracellular matrix ▫ Proteoglycan aggregates: hyaluronic (long chain of hyaluronic acid molecules) with hundreds of proteoglycans (proteins + long chains of glycosaminoglycan sugars—GAGS) branches from OSMOSE.ORG 407

Figure 48.4 Cross section of cartilage showing histological structure. The perichondrium wraps around the extracellular matrix. Chondroblasts originally in the perichondrium become chondrocytes when entrapped in the extracellular matrix. TYPES ▪ Three main types of cartilage Elastic cartilage ▪ The least common type ▪ ↑ chondrocyte density. ↓ Density of protein fibers (mainly loose elastin fibers, some type II collagen fibers) ▪ Softer, more flexible cartilage ▪ Pinnae, pharyngeal cord Hyaline cartilage ▪ Most common type ▪ Medium chondrocyte density. Moderate protein fiber density (mostly type II collagen fibers, some loose elastin fibers) ▪ Stronger, but less flexible cartilage. ↓ friction surface ▪ Fetal skeleton (eventually replaced by bone). nose; larynx walls; trachea, costal cartilage; growth plates; articular cartilage Fibrous cartilage ▪ ↓ chondrocyte density? ↑ Density of protein fibers (usually type I collagen fibers) ▪ The highest tensile strength. resistant to compression, stretching. ↓ flexible ▪ Knee meniscus, vertebral intervertebral discs 408 OSMOSE.ORG Figure 48.5 Proteoglycan aggregates, found in thick gel of extracellular matrix.

Chapter 48 Musculoskeletal physiology: bones, joints and cartilage Figure 48.6 Histology, characteristics of the three main types of cartilage. RATE OF DEVELOPMENT ▪ Two patterns of cartilage growth ▪ Both growth patterns are present in the developing bones of children, adolescents (eg femur) ▫ Chondrocytes in the growth plate → interstitial growth → cartilage elongates → osteoblasts turn cartilage into bone ▫ Articular points show cartilage on top of bone interstitial growth Deposition of growth ▪ Chondroblasts secrete new matrix on existing surfaces → cartilage expands, expands Interstitial growth ▪ Chondrocytes secrete new matrix into cartilage → cartilage grows in length Figure 48.7 The two forms of cartilage growth. Both types of growth occur in articular cartilage. Only interstitial growth takes place in the growth plate. OSMOSE.ORG 409

BONE MODEL & REPAIR osms.it/bone-remodeling-repair BONE REPAIR ▪ Old bone removed/absorbed (broken down) before new tissue replaces it 1. Osteoblasts detect microcracks, secrete receptor activator of nuclear factor-kb-ligand (RANKL) 2. RANKL binds to RANK receptors on monocytes → causes them to fuse and form multinucleated osteoclasts. 410 osmose.org (Howship's Lacunae), hydrochloric acid → dissolves hydroxyapatite into soluble calcium, phosphate 4. Osteoblasts secrete osteoprotergin → inactivate rankl, slows osteoclastic activity (before osteoclast apoptosis) phosphate deposition in refined hydroxyapatite 6. Some osteoblasts get trapped in gaps → turn into osteocytes

Chapter 48 Musculoskeletal Physiology: Bones, Joints, and Cartilage REMODELING AGENTS ▪ Hormonal ▫ Parathyroid hormone promotes bone resorption ▫ Calcitonin inhibits bone resorption ▫ Vitamin D (→ ↓ calcitonin (calcitonin) bones bearing more weight model more FIBER TYPES ▪ Classification based on movement of three main groups ▫ Fibrous joints: no movement ▫ Cartilaginous joints: some movement ▫ Articular joints: free movement FIBROUS JOINTS ▪ Articulation/fixed joints ▪ Bones are connected by ligaments Three main categories (based on position) ▪ Sutures: connections between adjacent cranial bones. Sharpey's fibers connect bones. Fixed (no fusion in infants → partially mobile) ▪ Pegs: pin joints for teeth. periodontal ligaments connect tooth roots to sockets. slightly mobile ▪ Ligaments : remaining fibrous joints. bound by interosseous membrane (eg, between radius, ulna). slightly mobile Figure 48.9 Three major classes of fibrous joints. OSMOSE.ORG 411

CARTILAGE JOINTS ▪ hyaline cartilage connects bones, stretches to allow some movement. growth plates between bony diaphysis, epiphysis ▪ Symphysis: pubic symphysis on pelvic bone (fibrocartilage) ▫ ↑ strength, ↓ flexibility JOINTS JOINTS ▪ Joint capsule connects bones ▫ Consists of outer fibrous synovial capsule: filled synovial capsule with renal membrane , , absorbs shocks. made of hyaluronic acid, lubricin, proteinases, collagenases ▫ Articular cartilage covers the tops of bones (same function) ▪ Allows for abduction, adduction, rotation around axis Six main categories (based on structure, movement) ▪ Hinged joints: only one axis movement allowed (e.g. between humerus, ulna) ▪ Swivel joints: allow rotation (e.g. between radial head, ulnar groove) ▪ Flat (sliding) joints: allow flat bones to slide over each other (e.g. in carpal, tarsal bones) ▪ Ball joints : allow all movements (e.g. shoulder joint) ▪ Condylar (elliptical) joints: allow most movement, but no rotation (eg, metacarpophalangeal, metatarsophalangeal joints) ▪ Saddle joints: allow the most movement, with limited rotation (eg, carpometacarpal joint) 412 OSMOSIS.ORG Figure 48.10 The two classes of cartilage joints (with examples). Figure 48.11 Cross section of an articular joint with synovial capsule.

Chapter 48 Musculoskeletal Physiology: Bones, Joints, and Cartilage Figure 48.12 The six classes of articular joints (with examples). Joints are circled in green. OSMOSE.ORG 413