Bones and Cartilage PDF Workshop Notes

bones and cartilage Created @November 26, 2024 10:53 AM Tags workshop notes overview general objective: to recognise various types and components of cartilage and bone and understand their...

bones and cartilage Created @November 26, 2024 10:53 AM Tags workshop notes overview general objective: to recognise various types and components of cartilage and bone and understand their functions specific objectives: (1) to recognise the histological appearance of the different types of cartilage: hyaline, elastic and fibrocartilage (2) to know the architecture of compact and spongy (cancellous) bone, the structure of osteons (haversian systems), the importance and position of haversian and volkmann’s canals (3) to differentiate between osteoblasts, osteocytes and osteoclasts and understand their roles in bone formation cartilage hyaline cartilage: identify: extracellular matrix → a gel-like substance composed of water, collagen fibres (mainly type ii collagen), and proteoglycans, providing structural support chondrocytes within lacunae → cartilage cells (chondrocytes) are located in small spaces called lacunae within the matrix bones and cartilage 1  cell nests (isogenous groups) → groups of chondrocytes that arise from the division of a single chondrocyte, appearing in clusters within the matrix perichondrium (outer fibrous layer and inner cellular layer) → outer fibrous layer — contains dense collagen fibres and fibroblasts; inner fibrous layer — contains chondroblasts that can divide and produce new cartilage extracellular matrix composition → mainly composed of type ii collagen, proteoglycans (like aggrecan), and water, providing both strength and flexibility to the cartilage perichondrium layer, outer fibrous: compositional differences → dense collagen fibres and fibroblasts functional differences → provides mechanical support and protects the cartilage perichondrium layer, inner circular: compositional differences → contains chondroblasts functional differences → involved in the growth and repair of cartilage chondroblast function → chondroblasts are immature cartilage cells responsible for producing the extracellular matrix difference in appearance to chondrocytes: chondroblasts are bones and cartilage 2  actively synthesizing the extracellular matrix and are typically more elongated or rounded, whereas chondrocytes are mature cells in lacunae and are less active chondrocyte nutrients intake → chondrocytes receive nutrients and oxygen through diffusion from nearby blood vessels in the perichondrium, as cartilage is avascular (lacks blood vessels) location within body → found in areas such as the articular surfaces of joints, costal cartilage (rib cage), nasal cartilage, and parts of the respiratory tract (e.g., trachea) cartilage properties → hyaline cartilage is firm yet flexible, providing smooth surfaces for joint movement, supporting structures like the nose and respiratory pathways, and forming templates for bone development in the fetus; it has low friction, absorbs shock, and can withstand compressive forces elastic cartilage: bones and cartilage 3  identify: extracellular matrix → similar to hyaline cartilage, but with an abundance of elastic fibres that give the tissue its flexibility chondrocytes within lacunae → cartilage cells are located within small spaces (lacunae) in the matrix elastic fibres → abundant in the ecm, these fibres provide flexibility and the ability to return to the original shape after deformation perichondrium → a connective tissue layer surrounding the cartilage, containing blood vessels and fibroblasts for cartilage growth and repair extracellular matrix composition → elastic cartilage contains elastic fibres (in addition to type ii collagen) embedded in a similar ground substance to hyaline cartilage, making it more flexible compare to composition in hyaline cartilage: elastic cartilage — more elastic fibres and less collagen; hyaline cartilage — predominantly collagen fibres, particularly type ii collagen, and fewer elastic fibres function of elastic cartilage → provides structural support with flexibility and elasticity, allowing the cartilage to return to its original shape after being bent or compressed bones and cartilage 4  compositional influences: the abundance of elastic fibers allows for more flexibility compared to hyaline cartilage comparison to hyaline cartilage: while both types of cartilage provide support, elastic cartilage is more flexible and resilient due to its elastic fibres, whereas hyaline cartilage is more rigid and provides smoother joint surfaces location within body → found in structures requiring both support and flexibility, such as the external ear (auricle), epiglottis, and parts of the larynx fibrocartilage: identify: thick bundles of type I collagen (stained pink) → large, parallel bundles of type i collagen fibres visible under a microscope, providing tensile strength cartilage matrix → the ecm contains a mix of type ii collagen and proteoglycans but is dominated by type i collagen chondrocytes within lacunae → cartilage cells (chondrocytes) are located within lacunae, but fewer in number compared to hyaline or elastic cartilage dense connective tissue arrangement → the matrix is interspersed with dense, bones and cartilage 5  parallel bundles of type i collagen, providing structural support and resistance to tension cartilage matrix arrangement → the cartilage matrix is more fibrous, with a mix of collagen fibres and ground substance, arranged to withstand compressive and tensile forces functional significance of type 1 collagen bundles → type i collagen bundles provide high tensile strength, helping fibrocartilage resist stretching and tearing, which is crucial in areas subjected to high mechanical stress location within body → found in areas subject to both compression and tension, such as intervertebral discs, pubic symphysis, and menisci of the knee relation to function: the dense type i collagen and fibrocartilage's arrangement allow it to function in load-bearing and shock absorption, providing stability and cushioning in joints and intervertebral spaces bone compact bone: bones and cartilage 6  identify: haversian system (osteon) → the basic structural unit of compact bone, consisting of concentric layers (lamellae) of bone matrix surrounding a central haversian canal osteocytes → mature bone cells located in small cavities called lacunae within the bone matrix. they maintain the bone tissue and communicate with each other via canaliculi (tiny channels) haversian canal and canaliculi → haversian canal — the central canal in each osteon, containing blood vessels and nerves, supplying nutrients to the bone; haversian canaliculi — tiny channels that connect osteocytes in lacunae to each other and to the haversian canal, allowing for nutrient and waste exchange identify: concentric lamellae → layers of bone matrix arranged in concentric rings around the haversian canal, providing strength and stability to the bone structure interstitial lamellae → fragments of old osteons found between the new osteons, representing remnants of previously remodelled bone bones and cartilage 7  circumferential lamellae → layers of bone that encircle the entire bone, just beneath the periosteum (outer bone layer), providing additional strength and support extracellular matrix of bone tissue → composed mainly of collagen fibres (type i), calcium phosphate crystals (hydroxyapatite), and other mineral salts, giving bone its strength and rigidity cells associated with bone tissue: osteoblasts → bone-forming cells that secrete the bone matrix and minerals osteocytes → mature bone cells maintain the bone matrix and communicate with other osteocytes for bone maintenance osteoclasts → large, multinucleated cells responsible for the resorption and breakdown of bone tissue, playing a role in bone remodelling cell functions: osteoblasts → synthesize and mineralize bone matrix during bone formation osteocytes → maintain bone tissue, monitor mechanical stresses, and coordinate remodelling osteoclasts → break down bone tissue, releasing bones and cartilage 8  minerals like calcium into the bloodstream during bone remodelling and repair compact bone: identify: volkmann’s canal → horizontal or oblique channels that run perpendicular to the haversian canals, connecting them and allowing for the passage of blood vessels and nerves between osteons osteocytes → mature bone cells located in lacunae within the bone matrix; they help maintain the bone tissue and communicate with other osteocytes canaliculi → small channels that radiate from the lacunae, allowing osteocytes to exchange nutrients, waste, and signals with other osteocytes and the haversian canal function of volkmann’s canal → volkmann’s canals allow for the passage of blood vessels and nerves between osteons, connecting the haversian canals and supplying the bone with nutrients and oxygen composition of haversian canal → the haversian canal contains blood vessels, nerves, and lymphatic vessels, all surrounded by layers of concentric bone matrix in the osteon bones and cartilage 9  composition of canaliculi → canaliculi are tiny, fluid-filled channels that allow for the exchange of nutrients and waste between osteocytes and the haversian canal. they also facilitate communication between osteocytes via gap junctions osteon cell arrangement → the functional unit of compact bone, consisting of concentric layers (lamellae) of bone matrix around a central haversian canal function: the arrangement of osteocytes within the lamellae, connected by canaliculi, allows for efficient nutrient diffusion, bone maintenance, and communication. the osteons work together to provide structural strength and rigidity to the bone spongy bone: note that spongy bone is a type of mature (lamellar) bone and should not be confused with woven bone (immature bone) identify: trabeculae → thin, branching plates or beams of bone that form a lattice-like structure in spongy bone. these trabeculae are aligned along lines of stress to provide support and distribute weight osteocytes → mature bone cells located in lacunae within the trabeculae. they maintain the bone bones and cartilage 10  matrix and communicate with other osteocytes through canaliculi bone marrow → the soft tissue filling the spaces between trabeculae in spongy bone. it contains hematopoietic stem cells responsible for producing blood cells location of trabeculae within body → trabeculae are found in areas of spongy bone, such as the epiphyses of long bones (like the femur and humerus), vertebrae, and flat bones (like the sternum and pelvis) difference in function to compact bone: spongy bone → provides lightweight structural support and houses bone marrow for blood cell production, its trabecular structure allows for flexibility and shock absorption compact bone → provides strength, rigidity, and protection to the bone structure, particularly around the diaphysis of long bones; it is denser and more solid than spongy bone, designed for weight-bearing and stability bones and cartilage 11