Joints, tendons cartilage 2023-24.pptx

Joints, + Tendons & Ligaments Dr Vehid Salih Y1 Programme co-lead Learning Objectives To describe the classification of joints To explore the structure and role of ligaments/tendons To explore the histology and functional characteristics of a synovial joint i.e. the TMJ To relate joint structure to...

Joints, + Tendons & Ligaments Dr Vehid Salih Y1 Programme co-lead Learning Objectives To describe the classification of joints To explore the structure and role of ligaments/tendons To explore the histology and functional characteristics of a synovial joint i.e. the TMJ To relate joint structure to function Some Definitions... Joint - a site where two or more bones or other skeletal components are joined together. Tendon - a fibrous band of connective tissue that is bonded to connects muscle to bone. bone and Ligament - a fibrous band of connective tissue that connects bones and other connective tissues together at joints. Cartilage - fibrous and viscoelastic connective tissue composed of closely packed collagenous fibres in a proteoglycanrich extracellular matrix. Classification of Joints Functional classification Focuses on amount of movement Synarthroses (immovable joints) Amphiarthroses (slightly movable joints) Diarthroses (freely movable joints) Structural classification Based on the material binding them and presence or absence of a joint cavity Bony fusion Fibrous Cartilagenous Synovial Table of Joint Types Functional Synarthroses (immovable joints) Amphiarthroses (some movement) Diarthroses (freely movable) Syndesmoses -ligaments only between bones; short, so some, but not a lot of movement (eg: tib-fib ligament) Syndesmoses -ligament longer (eg: radioulnar interosseous membrane) Structural Bony Fusion Synostosis (frontal=metopic suture; epiphyseal lines) Fibrous Suture (skull only) -fibrous tissue is continuous with periosteum Gomphoses (teeth) - ligament in this case is periodontal ligament Cartilagenous (bone united by cartilage only) Synovial Synchondroses -hyaline cartilage (eg: manubrium-C1, epiphyseal plates) Sympheses -fibrocartilage (eg: intervertebral discs, pubic symphesis Are all diarthrotic Sutures Only between bones of skull* Fibrous tissue continuous with periosteum Ossify and fuse in middle age: now technically called “synostoses”= bony junctions *USEFUL LEARNING AID https://www.kenhub.com/en/library/anatomy/the-cran ial-sutures Fibrous joints Bones connected by dense regular connective tissue No joint cavity Slightly immovable or not at all Types Sutures Syndesmoses Gomphoses Syndesmoses “with band” i.e. ligament Bones connected by ligaments only Amount of movement depends on length of the fibres (often longer than in sutures) Gomphoses Almost a peg in a socket Only example is a tooth within its socket Ligament is a short periodontal ligament Cartilagenous joints Articulating bones united by cartilage No joint cavity Slightly movable 2 types: Synchondroses Sympheses Synchondroses “Junction of cartilage” Hyaline cartilage unites the bones Immovable (synarthroses) Examples: Epiphyseal plates Joint between first rib’s costal cartilage and manubrium of the sternum Sympheses “Growing together” Fibrocartilage unites the bones Slightly movable (amphiarthroses) Resilient shock absorber Provide strength and flexibility Hyaline cartilage on articular surfaces of bones to reduce friction Examples Intervertebral discs Pubic symphysis of the pelvis Synovial joints Include most of the body’s joints All are diarthroses (freely movable) All contain fluid-filled joint cavity General Structure of Synovial Joints 1. Articular cartilage Hyaline Spongy cushions absorb compression Protects ends of bones from being crushed 2. Joint (synovial) cavity Potential space Small amount of synovial fluid General structure of synovial joints (cont.) 3. Articular (or joint) capsule Two layered Outer: fibrous capsule of dense irregular connective tissue continuous with periosteum Inner: synovial membrane of loose connective tissue (makes synovial fluid) Lines all internal joint surfaces not covered by cartilage General structure of synovial joints (cont.) 4. Synovial fluid Filtrate of blood Contains special glycoproteins Nourishes cartilage and functions as slippery lubricant 5. Reinforcing ligaments joints) (some Capsular (most) – thickened parts of capsule Extracapsular Intracapsular General structure of synovial joints (cont.) 6. Nerves Detect pain Monitor stretch (one of the ways of sensing posture and body movements). 7. Blood vessels Rich blood supply Extensive capillary beds in synovial membrane (produce the blood filtrate). Summary Characteristics of Synovial Joints Hyaline cartilage – A protective layer of dense white connective tissue that covers the ends of the articulating bones Joint cavity.... Synovial membrane – Covers joint cavity, except over the surfaces of the articular cartilages – Secretes the lubrication fluid Synovial fluid – Lubricates the joint Capsule – May or may not have thickenings called intrinsic ligaments Extrinsic ligaments – Support the joint and connect the articulating bones of the joint Tendons & ligaments (both viscoelastic; made up of dense regular connective tissue) Tendons – Attach muscle to bone – Transmit (and withstand) tensile loads, yet flexible – Aid position of muscle relative to joint – More stiff Ligaments – Attach bone to bone – Assist in stabilization of joint structures – Prevents undesirable movement/excessive motion – Less stiff Tendons & ligaments Property Tendon Ligament >80% 70-80% Type I collagen 95-99% 90% Type III collagen 1-5% 5% (up to 10%) Elastin + +++ Proteoglycans/GAGs + +++ > organised > random = = % collagen Fibre organisation Cells, H2O Cartilage Cartilage Articular vs. Elastic vs. Fibrous. Elastic cartilage e.g. epiglottis, larynx, pinna Fibrous cartilage Cartilage provides a supporting framework, forms the end of articulating joints and is the origin of long bone growth. Very hydrated ECM containing only one cell type (chondrocyte) and a unique organic matrix of proteoglycan and collagen fibres. Avascular and not innervated! NB Fibrous cartilage in TMJ e.g. Pubic symphesis, interverteb ral discs TMJ Union of mandible and skull condyloid process + temporal bone (articular fossa or mandibular fossa) articulating area also includes the articular eminence (anterior to the fossa) and the post-glenoid process (posterior to the fossa) condyle of the mandible articulates directly at the head of the condyle = articulating surface (Pocket Dentistry, Chapter 13 TMJ: Joint Capsule TMJ is a ball & socket joint – diathrotic joint = freely movable – synovial joint surrounded by a fibrous capsule capsule of fibrous connective tissue surrounds the head and neck of the condyloid process – superior border wraps around the articular eminence and fossa – inferior border wraps around the condyle (neck) https://www.physio-pedia.com/TMJ_Anatomy TMJ: Joint Interior synovial joint – articulating ends of bones covered with TMJ condylar cartilage has both fibrocartilaginous and hyaline-like character, with a thin proliferative zone that separates the fibrocartilaginous fibrous zone at the surface from the hyaline-like mature and hypertrophic zones below this (different to other synovial joints) https://core.ac.uk/download/pdf/82669887.pdf – cartilage + fibrous capsule is surronded with a synovial membrane (epithelium + connective tissue) the synovial membrane cells synthesize a watery fluid = synovial fluid the synovial fluid protects and lubricates between the articulating bones = joint disc or articular disc (fibrocartilage disc = meniscus) disc can degenerate with age or trauma or mechanical stress can also become dislocated TMJ: Articular Disc disc divides the joint cavity into two regions 1. superior synovial cavity 2. inferior synovial cavity – the disc attaches to: the mandibular condyle the temporal bone – anterior attachment is NOT a direct attachment the temporal bone posteriorly – here the disc divides into: » an upper division – attaches to post-glenoid process » a lower division – attaches to the condylar neck TMJ: Ligaments Three major ligaments – stylomandibular ligament styloid process to the angle of the mandible tightens with protrusion – sphenomandibular ligament NOT a part of the TMJ runs from the spine of the sphenoid to the ramus of the mandible (lingula of the mandibular foramen) a vestige of the embryonic lower jaw tightens with protraction of mandible landmark for local anesthesia – TMJ ligament (lateral ligament) reinforces the inferior portion of the capsule prevents excessive retraction of mandible runs from tubercle of the zygomatic process to the neck of the mandible TMJ: Muscles The four muscles of mastication: Temporalis – contraction of both retracts the mandible and produces a gliding motion in the upper synovial cavity – – – – Masseter – strongest of the four muscles – – – – O: maxilla & zygomatic arch I: angle & ramus of mandible A: elevates N: mandibular division of cranial nerve V Medial Pterygoid – – – – O: Temporal Bone I: Coronoid process & ramus of mandible A: elevates & retracts N: mandibular division of cranial nerve V O: lateral pterygoid process of sphenoid I: angle and ramus A: elevates, protracts and lateral movements N: mandibular division of cranial nerve V Lateral Pterygoid – – – – O: lateral pterygoid process of sphenoid I: condyle of mandible A: depresses, retracts and lateral movements N: mandibular division of cranial nerve V TMJ: Movements TMJ: Movements Ball & socket structure allows for movement in more than one plane = multi-axial joint SDL