Week 3 - Skeletal System PDF

# SKELETAL SYSTEM ## October 10th Zaitunnatakhin Zamli [email protected] ## Learning Outcomes The student should be able to: - Describe the general features and functions of skeletal system. - Name the bones that form the axial and appendicular skeleton. - Name the various types of bones, joints...

# SKELETAL SYSTEM ## October 10th Zaitunnatakhin Zamli [email protected] ## Learning Outcomes The student should be able to: - Describe the general features and functions of skeletal system. - Name the bones that form the axial and appendicular skeleton. - Name the various types of bones, joints, bone markings and cartilage. - Classify the bones based on shapes and histological structures. - Classify the joints based on the function and structure. - Identify and describe the morphological features of cells and extracellular matrix of bone and cartilage. - Explain the osteogenesis and chondrogenesis. ## The Axial and Appendicular Skeleton ## Introduction ### Major Components: - Bone - Cartilage - Associated ligaments - Bone marrow ### General Features: - Tissue vs. organ - Strong and hard - Resists compression and shearing forces - Dynamic tissue ### Functions: - Support - Storage - Blood cell production - Protection - Leverage for movement ### Number of Bones in the Body: - Axial skeleton: 80 bones - Appendicular skeleton: 126 bones - TOTAL = 206 bones ## The Skeletal System The images show the skeletal system. ## Axial Skeleton | Bone | Number | | :---------------------------------- | :----- | | Skull | 80 | | - Cranium | 8 | | - Face | 14 | | - Auditory ossicles | 6 | | - Hyoid | 1 | | Skull and associated bones | 29 | | Associated bones | | | Thoracic cage | 25 | | - Sternum | 1 | | - Ribs | 24 | | Vertebral column | 26 | | - Vertebrae | 24 | | - Sacrum | 1 | | - Соссух | 1 | ## Appendicular Skeleton | Bone | Number | | :---------------------------- | :----- | | Clavicle | 2 | | Scapula | 2 | | Humerus | 2 | | Radius | 2 | | Ulna | 2 | | Carpal bones | 16 | | Metacarpal bones | 10 | | Phalanges (proximal, middle, distal) | 28 | | Hip bone (coxal bone) | 2 | | Femur | 2 | | Patella | 2 | | Tibia | 2 | | Fibula | 2 | | Tarsal bones | 14 | | Metatarsal bones | 10 | | Phalanges | 28 | ## Classification of Bone - Shape ### Bone Shapes: - Long bone - Short bone - Flat bone - Irregular bone - Sesamoid bone The illustration shows the different shapes of human bones. ## Classification of Bone - Histological Structures ### Bone Histological Structures **a. Compact bone** - Solid mass, tube vs. column - osteon / Harvesian system - Forms the surface of bone - Thick in: shaft of the long bone, surface of flat bone **b. Spongy/Cancellous bone** - Interior part of bone - No Harvesian system - spicules / trabeculae - In flat bone → diploe ## Parts of a Long Bone The illustration shows the parts of a long bone. ### Parts: - Epiphyses - Metaphyses - Diaphysis - Medullary cavity - Periosteum - Endosteum - Articular cartilage ## Bone Markings - Articulating Surface ### Bone Markings: - **Condyle** - rounded articular projection - **Facet** - smooth, nearly flat articular surface - **Head** - bony expansion on a narrow neck - **Trochlea** - smooth, grooved, pulley-like articular process The illustrations depict the different bone markings. ## Bone Markings - Openings and Cavities ### Bone Markings: - **Fissure** - narrow, slit-like opening through a bone - **Foramen** - round / oval opening through a bone - **Canal** - passageway through a bone - **Meatus** - an opening into a canal - **Sinus** - space within a bone, filled with air The illustrations show the different openings and cavities on the skull. ## Bone Markings - Projections ### Bone Markings: - **Process** - any marked body prominence or projection - **Line** - narrow ridge of bone - **Crest** - narrow ridge of bone, usually prominent - **Spine** - sharp, slender, often pointed projection - **Ramus** - armlike bar of bone - **Epicondyle** - projection on or above condyle - **Tubercle** - small rounded projection/process - **Tuberosity** - large rounded projection, may be roughened - **Trochanter** - very large, blunt, irregular shaped projection The illustrations depict the different projections on the hip bone and the humerus. ## Classification of Joint ### Functions - No movement / synarthrosis (e.g. suture) - Little movement / amphiarthrosis (e.g. symphysis) - Free movement / diarthrosis (e.g. knee joint) ### Structures: - Bony (e.g. epiphyseal line) - Fibrous (e.g. suture) - Cartilaginous (e.g. epiphyseal plate) - Synovial (e.g. knee joint) The illustrations explain the different types of joints and their functions. ## Functional and Structural Classifications of Articulations - Synarthrosis (no movement): - Suture: A synarthrotic joint located only between the bones of the skull. - Gomphosis: A synarthrosis that binds the teeth to bony sockets in the maxillae and mandible. - Synchondrosis: A rigid, cartilaginous bridge between two articulating bones. - Synostosis: An immovable joint created when two bones fuse. - Amphiarthrosis (little movement): - Syndesmosis: Bones are connected by a ligament. - Symphysis: Bones are separated by a wedge or pad of fibrous cartilage. - Diarthrosis (free movement): - Synovial: Permits a wider range of motion than other types of joints. ## Classification of Synovial Joints | Type of Synovial Joints | Models of Joint Motion | Examples | | :------------------------ | :------------------------- | :------------------------------------------------------------------ | | Gliding joint | | Acromioclavicular and sternoclavicular joints, intercarpal and intertarsal joints, vertebrocostal joints, sacro-iliac joints | | Hinge joint | | Elbow joints, knee joints, ankle joints, interphalangeal joints | | Pivot joint | | Atlas/axis, proximal radio-ulnar joints | | Ellipsoid joint | | Radiocarpal joints, metacarpophalangeal joints 2-5, metatarsophalangeal joints | | Saddle joint | | First carpometacarpal joints | | Ball-and-socket joint | | Shoulder joints, hip joints | The illustrations show different types of synovial joints. ## Revision Based on the following image can you name: - The bones - Types of bone based on shape and location - Types of joint based function and structural features - Types of bone marking. ## Histology of Bone ## Histological Structure of Bone - Compact & Spongy Bone The illustration shows the histological structure of compact and spongy bones. ## Histological Structure of Bone - Bone Marrow ### Yellow Bone Marrow: - adipocytes - Function - energy reserve ### Red Bone Marrow: - RBC, WBC and platelets - In newborns - nearly all bones - In adults - skull, vertebrae, sternum, ribs, pelvic girdle, head of femur & humerus - Function - hematopoiesis The illustrations show the yellow and red bone marrow. ## Bone Tissue - Cells ### Osteogenic / Osteoprogenitor Cells: - Origin - mesenchymal cells - Location - cellular layer of periosteum and endosteum - Function - differentiate into osteoblasts. ### Osteoblasts: - Origin - osteoprogenitor cells - Location - cellular layer of periosteum and endosteum - Shape - flat (less active) or cuboidal (active) - Function - synthesize osteoid ### Osteocytes: - Origin - osteoblasts - Location - mainly in lacunae, the cytoplasmic processes in canaliculi - Function - maintaining the bone matrix and participate in the repair of damaged bone. ### Osteoclasts: - Origin - monocytes - Shape - large, multinucleated - Other features - mobile and phagocytic (> lysosomes) - Location - Howship's lacunae - Function - osteolysis / bone resorption The illustrations show microscopic images of cells found in bone tissue. ## Bone Tissue - Bone Matrix ### Inorganic Substances: - Calcium phosphate - hydroxyapatite crystals [Ca10(PO4)6(OH)2 - Other minerals - bicarbonate, citrate, magnesium, potassium and sodium. ### Organic Substance: - Collagenous substances - Collagen Type I, V, III, XI, and XIII. - Non-collagenous substances - proteoglycans, glycoproteins, bone-specific proteins, and growth factors and cytokines. ## Woven Bone and Lamellar Bone The illustration shows the microscopic images of woven bone and lamellar bone. ## Other Connective Tissues - Periosteum & Endosteum ### Periosteum: - Lines the external surface of bone except at the articulating surface. - Comprises of: - Outer fibrous layer - a dense connective tissue - Inner cellular layer - contains of osteoprogenitor cells ### Endosteum: - Lines the internal surface of bone including spicules and central canal. - Contains a single of osteoprogenitor cells and osteoblasts The illustration shows the microscopic images of periosteum. ## Osteogenesis - Introduction ### Intramembranous Ossification: - Formation of bone in the c.t. (mesenchymal tissue) - Replaces the c.t. - i.e. skull, mandible, maxilla and clavicle ### Endochondral Ossification: - Formation of bone from cartilage - i.e. long bones of limbs, vertebrae, etc. ## Osteogenesis - Intramembranous Ossification The illustration depicts the steps involved in intramembranous ossification. ## Osteogenesis - Endochondral Ossification The illustration depicts the steps involved in endochondral ossification. ## Revision The illustration shows a microscopic image of bone tissue. ## Histology of Cartilage ## Cartilage Tissue - Cells ### Chondrogenic Cells: - Origin - mesenchymal cells - Location - inner layer of perichondrium - Shape - Spindle-shaped with ovoid nucleus. - Function - differentiate into chondroblasts. ### Chondroblasts: - Origin - chondrogenic cells - Location - inner layer of perichondrium - Shape - Small cells with abundant cytoplasm. - Function - synthesize cartilage matrix ## Cartilage Tissue - Cells ### Chondrocytes: - Origin - chondroblasts - Location - in lacunae either singly or in an isogenous group/cell nest. - Shape - Typically round to polygonal-shaped. - Arrangement - parallel to perichondrium (periphery) or cell nest/isogenous group (internally) - Function - growth and maintaining the cartilage matrix The illustration shows a microscopic image of cartilage. ## Cartilage Tissue - Matrix ### Water: - Act as a medium of exchange and preserve the resiliency of the cartilage. ### Collagenous Components: - Type II collagen (80% of collagenous content) provides tensile strength, resists compression and hinder expansion of the viscoelastic matrix. ### Noncollagenous Components: - Aggrecan (50-85% of total PG) is negatively charged. It attracts and bind with water molecules. Together with the collagen, it provides compressive stiffness and elasticity. ## Other Connective Tissues - Perichondrium ### Perichondrium: - Dense irregular connective tissue - Consists of: - Outer fibrous layer - fibroblasts and fibers - Inner cellular layer - chondroblasts and chondrogenic cells - Location - covers the outer surface of cartilage, except at the AC and fibrocartilage. - Functions - involved in growth and nourishment of the cartilage cells. The illustration shows a microscopic images of perichondrium. ## Hyaline Cartilage and Dense Irregular Connective Tissue The illustration shows a microscopic images of hyaline cartilage and dense irregular connective tissue. ## Type of Cartilage - Hyaline Cartilage ### General Features: - Surround by perichondrium (except in joint cavity) - Clear and glassy matrix - Locations - including nasal septum, larynx, trachea, articular surface of bone & costal cartilage. - Function - reduces friction at joints, supports and maintain shape and serve as a cartilage template for endochondral ossification. The illustration shows a microscopic image of hyaline cartilage. ## Type of Cartilage - Elastic Cartilage ### General Features: - Surround by perichondrium - Chondrocytes - numerous - ECM - Type II collagen, abundant elastic fibres - Locations - epiglottis, ear auricle and wall of auditory tube - Functions: - Confers structural support - Provides additional resiliency and pliability The illustration shows a microscopic image of elastic cartilage. ## Type of Cartilage - Fibrocartilage ### General Features: - Combination of hyaline cartilage and dense c.t., no perichondrium. - Chondrocytes - arranged singularly, in column or isogenous group. - Fibroblasts - synthesize versican. - ECM - acidophilic, more interwoven collagen fibres than amorphous ground substance (around lacuna) - Locations - intervertebral disc, pubic symphysis, meniscus and insertion of tendon. - Functions - provide tensile strength, bear weight, resist excessive stretch and compression. The illustration shows a microscopic image of fibrocartilage. ## Chondrogenesis - Interstitial & Appositional Growth ### Interstitial Growth: - Growth from within - Chondrocytes undergo cell division ### Appositional Growth: - Additional layer of newly synthesised cartilage to the surface. - Chondrogenic cells undergo cell division. ## Revision The illustration shows microscopic images of the different types of cartilage. ## Thanks!