physiology of the joint Flashcards
1. What are the primary functional roles of joints in the musculoskeletal system?
Structural support, purposeful movement, stress distribution, confer stability (shape of articular component, ligaments, synovial fluid acts as an adhesive seal), joint lubrication (cartilage interstitial fluid, synovium-derived hyaluronic acid, synovium-derived lubricin).
- Define and give examples of fibrous joints (synarthrosis).
Fibrous joints babe pic
Fibrous joints are where bones are united by ligaments/ fibrose tissue, typically allowing little to no movement. Examples Sutures where they are completely fixed in adults but partially movable in fetus
- Explain cartilaginous joints (amphiarthrosis) and provide examples.
Cartilaginous joints involve bones united by cartilage, allowing limited movement. Examples include IV discs, pubic symphysis, part of the sacroiliac joints, and costochondral joints.
- Describe the components of synovial joints.
Synovial joints have bones separated by a cavity containing synovial fluid and are united by a capsule, ligaments, tendons, and bursae. Articular surfaces are covered with cartilage.
- What is the function of the synovial membrane?
The synovial membrane, a vascular connective tissue,
lines the inner aspect of the fibrous capsule.
It contains synovial cells (fibroblasts) that produce synovial fluid.
- Differentiate between a simple synovial joint and a compound synovial joint.
A simple synovial joint involves one pair of articular surfaces (e.g., metacarpophalangeal joint), while a compound synovial joint involves more than one pair of articular surfaces (e.g., elbow joint).
- Explain the properties and composition of synovial fluid.
Synovial fluid, filling the joint cavity, is continuously replenished by the synovial membrane. It has high viscosity due to hyaluronic acid, with viscosity and elasticity varying with joint movement.
- What is the normal appearance of synovial fluid?
Normal synovial fluid is clear and colorless.
- Describe the cell count and characteristics of normal synovial fluid.
Normal synovial fluid contains few cells, mainly mononuclear leucocytes, with WBC count usually <200/mm3 and polymorphs <25/mm3.
- In what situations does the synovial fluid turn red?
The synovial fluid turns red in traumatic synovial tap and in haemorrhagic arthritis.
- Enumerate the functions of synovial fluid.
Synovial fluid lubricates joints, facilitates joint movement, helps minimize wear-and-tear, aids in the nutrition of articular chondrocytes, and supplies chondrocytes with O2 and nutrients while removing CO2 and waste products.
- What functions does articular cartilage serve?
- Provides a low friction lubricated gliding surface which helps prevent wear-and-tear of joints (synovial fluid) - Distributes contact pressure to subchondral bone - The cartilage composition of the cartilage ECM and the interaction between the fluid and solid phase of the cartilage plays a significant role in determining the mechanical properties of cartilage
- Describe the structure of articular cartilage.
- The articular cartilage is usually hyaline - It is elastic and has a sponge-like property - The zones differ in the organization of collagen fibers and relative content of cartilage components
- What are the main components of the extracellular matrix (ECM) in articular cartilage?
- Water (70%) - maintains the resiliency of the tissue and contributes to the nutrition and lubrication system - Collagen (20%) - mainly type II (elastic) - Maintains cartilage architecture - Provides tensile stiffness and strength - Decreases with age - Proteoglycans (10%) - responsible for the compressive properties associated with load-bearing (act like ‘balloons’) - Composed mainly of glycosaminoglycan, e.g., chondroitin sulfate - Composition changes with age, e.g., chondroitin decreases with age
- How is the ECM synthesized in articular cartilage?
Synthesized, organized, and degraded by chondrocytes, usually constituting <2% of the total cartilage volume - The articular cartilage is avascular, and chondrocytes receive nutrients and O2 via the synovial fluid - In normal joints, the rate of ECM degradation doesn’t exceed the rate at which it is replaced - Joint disease can occur if the rate of ECM degradation exceeds the rate of its synthesis
- What may go wrong in a joint?
- Cartilage and synovial fluid decomposition and function deteriorate with age and repeated wear and tear → osteoarthritis - Synovial fluid proliferation and inflammation → rheumatoid arthritis - Deposition of salt crystals, e.g., uric acid →gouty arthritis - Injury and inflammation to periarticular structures can cause soft tissue rheumatism, e.g., injury to the tendon causes tendonitis
What are the characteristics of bone?
Rigid, not permeable - Cells within the bone must be nourished by blood vessels that pervade the tissue
List the primary functions of bone.
- Support 2. Levers for effective movement 3. Protection of internal organs (e.g., cranium, ribs) 4. Calcium store - More than 95% of the total calcium found in the body is in bone, and there is constant change of calcium between bone and blood 5. Haemopoiesis (blood cell production) - Typically shifts to bone marrow by birth
What is intramembranous ossification, and where does it occur?
- **Intramembranous ossification **is the process of bone development from fibrous membranes, involved in flat bones like the skull, mandible, and clavicles - Endochondral ossification is the process of bone development from hyaline cartilage, involved in most bones in the body
How is bone girth increased?
Bone girth is increased by cells from the periostrum, which lay down circumferential new bone on the periphery of the existing cortex
How is bone length increased?
Bone length is increased by cartilage proliferation at growth plates between the metaphysis and epiphysis; the cartilage then ossifies
Define the diaphysis, epiphysis, and metaphysis in bone anatomy.
- Diaphysis: Long shaft of bone 2. Epiphysis: Ends of bone 3. Metaphysis: Between epiphysis and diaphysis 4. Articular cartilage: Covers epiphysis 5. Periosteum: Membrane covering the outer surface of all bones except at the articular surfaces 6. Medullary cavity: Hollow chamber in bone
What is the composition of bone?
- 65% bioapatite (mostly hydroxyapatite, a form of calcium phosphate) - 23% collagen - 10% water - 2% non-collagen proteins
Describe the morphology of bone.
- The outer shell of dense cortical bone makes up the shaft (diaphysis) - Cancellous or trabecular bone occupies the ends of the bone (epiphysis) - Both types are lamellar, made up of layers - Bone is a living tissue penetrated by small canals for blood vessels and nerves, containing living cells called osteocytes
Explain the morphology of cortical bone.
- Lamellae organized into concentric circles surrounding a vertical Haversian canal (transmits small neurovascular and lymphatic vessels) - The entire structure is called an osteon, the functional unit of bone - Osteocytes located between lamellae within lacunae - Lacunae interconnected by canaliculi
Describe the morphology of trabecular bone.
- Trabecular bone has osteocytes and is lamellar in nature but generally lacks Haversian canals - Due to thin struts, osteocytes can survive from contact with marrow spaces
How does bone microarchitecture influence bone strength?
- At 20 years: strong, healthy bone - At 50 years: decrease in trabecular thickness, more pronounced for non-load-bearing horizontal trabeculae - At 80 years: decrease in the number of connections between vertical trabeculae and a decrease in trabecular strength
What is the role of osteocytes in bone structure?
Osteocytes are living cells in bone, located between lamellae within lacunae. They play a crucial role in maintaining bone health by sensing mechanical strain and influencing bone remodeling.
