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PBL 5 Scenario 5

Structure, Function of Bone, Synovial Joints, Cartilage

What are the main functions of bone? Support, Protection, Assistance in movement, mineral homeostasis, Blood cell production, triglyceride storage
What is the structure of a typical long bone? Diaphysis, epiphyses, metaphysis, the articular cartilage, the periosteum, the medullary cavity and the endosteum
The diaphysis (Growing between) is the bone's shaft or body- the long, cyclindricaal, main portion of the bone
The epiphyses Distal and proximal ends of the bone
The metaphyses Regions in mature bone where the diaphysis joins the epiphyses.
In a growing bone, what does each metaphysis contain? includes an epiphyseal plate, a layer of hyaline cartilage that allows the bone to grow in length.
What happens when a bone ceases to grow at age 18-21? The cartilage in the epiphyseal plate is replaced by bone; the resulting bony structure is called the epiphyseal line.
Articular cartilage A thin layer of hyaline cartilage covering the part of the epiphysis where the bone forms an articulation with another bone. Reduces friction and absorbs shock
Periosteum A tough sheath of dense irregular connective tissue that surrounds the bony surface wherever it is not covered by articular cartilage, contains bone-forming cells that allow bone to grow in length.
What are the other functions of the periosteum Proects the bone, assists in fracture repair, helps nourish bone tissue, and serves as an attatchment point for ligaments and tendons. Attatched to underlying ECM through Sharpey's fibres, thick bundles of collagen fibres.
Medullary cavity Is the space within the diaphysis that contains fatty yellow bone marrow in adults.
Endosteum Is a thin membrane that lines the medullary cavity. It contains a single layer of bone-forming cells and a small amount of connective tissue.
What are the four types of cells present in bone tissue? Osteogenic progenitor cells, Ostepblasts, Osteocytes and osteoclasts
Osteo progenitor cells Unspecialised stem cells derived from mesenchyme, the tissue from which all connective tissues are formed. The only bone cells to undergo cell division; the resulting cells develop into osteoblasts.
Osteoblasts Bone-building cells. Synthesize and secrete collagen fibres and other organic collagen fibres needed to build the ECM. Initiate calcification. Do not undergo cell division.
Osteocytes mature bone cells, main cells in bone tissue, maintain daily metabolism. Do not undergo cell division
Osteoclasts Huge cells derived from the fusion from 50+ Monocytes. Concentrated in the endosteum. Has a ruffled border that releases powerful lysosmal enzymes and acids that digest the proteins of the underlying bone matrix.
Features of Compact Bone? Circumferential lamellae, Osteons, Central Canal, Interstitual lamellae, perforating canal and concentric lamellae
Circumferential Lamellae Layers of bone that run parallel to the outer and inner diameters of the compact bone, they are in contact with the periosteum externally and the endosteum internally.
What lies between two sheets of cirumferential lamellae? osteons and intersititual lamellae
Components of bone tissue are arranged into repeating units called? Osteons
What do osteons contain? A central canal, Concentric lamellae, lucanae, osteocytes and canaliculi
Central Canal A channel through the core of each osteon; it permits the passage of neurovascular structures
Concentric Lamellae Ring of calcified extracellular matrix that makes up the osteons
Lucane Found between the lamella, contain osteocytes. Radiating in all directions from the lucane are tiny canaliculi which connect lucane with one another.
What do teh areas between osteons contain? Interstitual lamellae.
Interstitual lamellae Are fragments of older osteons that have been partially destroyed during bone rebuilding or growth.
Perforating canals/Volkmann's canals transverse The compact bone, connecting central canals of the osteons to the neurovascular supply of the periosteum.
What element of Compact bone is not present in spongy bone tissue? Osteons
Trabeculae in spongy bone tissue? Supports and protect the red bone marrow. Lamellae arranged into an irregular lattice of thin collumns called trabeculae
Joints can be classified based on their? 1. Structurally, bassd on their Anatomical characteristics 2. Functionally, based on the type of movement they permit
The STRUCTURAL classification of joints is based on two criteria? 1. The presence or absence of a space between the articulating bones 2. The type of connective tissue that binds the bones together.
What are the three classes of joints? Fibrous Cartilagionous Synovial Joints
What is a joint? Also called an articulation, Point of contact between two or more bones, between bone or cartilage, or between bone and teeth. Can be moveable or static
Functional classification Relates to the degree of movement they permit
What are the different types of FUNCTIONAL classifcation of joints Synathorosis - imovable joint Ampithorosis- Slightly movable joint Diathorosis- A freely movable joint ( all synovial joints)
Synovial Joint structures? Articular capsule, Synovial Fluid, Accesory ligaments and articular discs
Articular Capsule Function Surrounds a synovail joint which encloses: The synovial cavity, unites the articulating bones
What are the two layers of an articular capsule Composed of two layers: An outer fibrous capsule and inner synovial membrane
Outer fibrous capsule of a synovial joint Consists of dense irregular connective tissue( mostly collagen fibres) that attatches to the periosteum of articulating bones. Fibres can be arranged as parallel bundles of dense regukar connective tissue, highly adapted for resisting strains(ligaments)
Inner Layer synovial membrane of articular capsule composed of areolar connective tissue with elastic fibres. Includes accumulations of adipose tissue, called articular fat pads.
Synovial fluid function Synovial membrane secretes synovial fluid. Reduces friction by: lubricating the joints, absorbing shock and supplies oxygen and nutrients to and removing CO2 and metabolic wastes from the chondrocytes within articular cartilage.
Synovial fluid composition Consists of hyaluronic acid secreted by fibroblast-like cells in the synovial membrane and interstitual fluid filtered from blood plasma. It forms a thin film over the surfaces within the articular capsule. Contains phagocytic cells, removes debris.
What happens when the synovial joint is immobile for a time? the fluid becomes quite viscous but as joint movement increases, the fluid becomes less viscous
Accesory ligaments Contain extracapsular ligaments and intracapsular ligaments
Extracapsular ligaments Lie outside the articular capsule. E.g fibular and tibular collateral ligaments.
Intracapsular ligaments Occur within the articular capsule but are excluded from teh synovial cavity by folds of the synovial membrane. E.g the ACl and PCL ligaments of the knee joint
Articular discs e.g knee, pads of fibrous cartliage lie between the articular surfaces of the bones and are attatched to the fibrous caspule. Known as arituclar discs. Sibdivide synovial cavity into two spaces, allowing separate movements to occur in each space.
Bursae Saclike structures are situated to alleviate friction in some joints. Not strictly part of synovial joint, but resemble joint capsules.
Movements at synovial joints are grouped into four main cateogries. What are these? 1. Gliding 2. Angular movements 3. Rotation 4. Special movements
Gliding Simple movement in which flat bone surfaces move back-and-forth and from side-to-side with respect to one another. No siginificant alteration of of the angle between bones.
Angular movements Increase or decrease in angle between articulating bones. Major angular movements are: flexion, Extension, Lateral extension, Hyperextension, Abduction, Adduction, circumduction
flexion Decrease in the angle between articulating bones. i.e tucking your head forward towards neck.
Extension Increase in the angle between articulating bones e.g moving your head back to upright position from being positioned at your neck
Abduction (to be abducted, to take away) movement of part of the body away from the midline.
Adduction Movement of part of the body toawrds the midline
Circumduction Circular motiom of dital end of body part in a circular motion. Combination of: flexion, extension, adduction and abduction.
Rotation A bone revolves around its own longitudinal axis, in limbs, it may me medial or lateral rotaion.
Special movements Elevation, depression, protraction, retraction, inversion, eversion, dorsiflexion, plantar flexion, supination, pronation, opposition
Elevation and depression Elevation-Superior movement of a body part Depression- Inferior movemnt of a body part
protraction and retraction Protraction- moves part of a body anteriorly in trasnverse plain Retraction- moves part of the body posteriorly in transverse plane
Inversion and eversion Inversion- medial movement of soles inwards Eversion- lateral movement of soles inwards
Supination, Pronation, opposition Movement of the forearm that turns the palm anteriorly. Pronation- movement of forearm that turns palm posteriorly. opposition- movement of thumb across the palm to touch fingertips on same hand
what are the different types of synovial joints? Planar, Hinge, pivot, condolyoid, saddle and ball and socket
Hinge Joints uniaxial, like hinge on a door, only restricted to one plane by the shape of the opposing articular surfaces. ONLY FLEXION AND EXTENSION. E.G the knee
Planar joints Nonaxial, motion does not occur around an axis or along a plane, gliding motion. e.g intercarpal
Pivot Joints rounded or pointed surface of one bone articulates with a ring formed partially by another bone and partially by a ligament. Is uniaxial,
Condolyoid Joints convex oval shaped projection of one bone fits into the oval shaped depression of another bone. Is biaxial, as the movement it permits is around two areas.
Saddle joints the articular surface of one bone is saddle shaped, and the articular surface of another bone fits into the "saddle". Is a modification or condolyoid joint as freere movement is allowed. Biaxial.
ball and socket joints Ball like surface of one bone fitting into a cup-like depression of another bone. Multiaxial, permit movement around three axes plus all directions in between.
Cartilage a dense network of colagen fibres and elastic fibres firmly embedded in condroitin sulfate, a gel-like component of ground substance
What is the strength in cartilage due to? due to collagen fibres
what is the resistance in cartilage due to? chondrotin sulfate
What are the cells of mature cartilage Chondrocytes, occur singly or in groups within spaces called lucanae in the ECM
What covers the surface of most cartliage? Perichondrium covers the surface of most cartilage
Why does cartilage heal poorly following an injury? Unlike oher connective tissue, it contains no blood vessels or nerves, except in the perochondrium
what are the three types of cartilage? Hyaline, fibrocartliage, and elastic cartilage
Hyaline cartilage Contains a resilient gel as its ground substancce and appears in the body as a bluish-white substance. Weakest but most abundant
Fibrocartilage Chondrocytes are scattered amoung ckearly visable bundles of collagen fibres. LACKS A PERICHONDIRUM. Is the strongest type of cartilage
elastic cartilage Chondrocytes are located within a threadlike network of elastic fibres within the ECM. perichondrium present
Created by: Taryn Miller