classification of joints, muscles and cartilage

Question 1

Joints types based on structure and range of motions available

Answer 1

structure: synovial: fibrous capsule, joint cavity with lubricating fluid, articular (hyaline) cartilage
- fibrous: joined by fibres tissure
- cartilaginous: joined by either hyaline or fibrocartilage

Movements: diarthroses- largest range of movements available, diarthroses joint=synovial joint

• amphiarthroses: a few movements available -> syndesmoses, secondary cartilaginous/symphyses
• synarthroses: no or very slight movements available -> primary cartilaginous/synchondroses, sutures, gomphoses

Question 2

Synovial joints characteristics and types

Answer 2

aka diarthrosis

Characteristics: bones are joined by a joint capsule (consisting of a fibrous layer - blends w/ periosteum - and an inner serous synovial membrane), articular cartilage cover the articulating parts of the bones and a joint cavity containing lubricating fluid secreted by the serous membrane separates the two bones

Types: ball and socket - multiaxial eg GHJ

• pivot - uniaxial (only rotation) eg atlanto-axial joint
• plane - gliding eg acromioclavicular
• hinge - uniaxial (flex/extension) eg elbow
• saddle - biaxial eg 1st CMCJ
• condyloid - biaxial, more movement available in one plane compared to the other eg 2nd-4th MCPJ

Question 3

Fibrous joints types and characteristics

Answer 3

joints united by fibrous tissue

Sutures: found between bones of the cranium, the bones are close together and either interlocking along a wavy line or overlapping - synathrosis

Syndesmoses: unites bones w/ a sheet of fibrous tissue, either a ligament/fibrous membrane, partially moveable eg IO membrane in forearm or leg - amphiarthrosis

Dentoalveolar Syndesmoses/Gomphoses: peg-like process fits into a socket articulation between the root of the tooth and alveolar process of jaw, microscopic movements give us information on how hard we are biting or whether there is something stuck between our teeth -> in maxilla and inferior maxilla/mandible - synarthrosis

Question 4

cartilaginous joints types and characteristics

Answer 4

Joints are united by cartilage

Primary cartilaginous/synchondroses - joined by hyaline cartilage, allows very slight bending in early life eg epiphyseal plates - synarthroses

Secondary cartilaginous/symphyses - joined by fibrous cartilage eg intervertebral discs, the joints (cumulatively) allow shock absorption, strength and flexibility - amphiarthroses

Question 5

compare skeletal/cardiac/smooth muscle

Answer 5

skeletal: large, very long, unbranched, cylindrical and striped fibres arranged in parallel bundles, multiple peripherally located nuclei, T tubules located between A and I band overlap

Cardiac: branching and anastamosing shorter fibres w/ transverse striations running parallel and connected end to end by complex junctions, intercalated discs, has single central nuclei, T tubule located at Z line

Smooth: single or agglomerated, small spindle shape fibres w/o striations, single central nucleus

Question 6

aponeurosis

Answer 6

tendons of muscles that form a flat sheet

they anchor muscles to skeleton a/o to deep fascia eg lat. dorsi, or to aponeurosis of another muscle eg oblique muscles of anterolateral wall

Question 7

Shapes of muscles types

Answer 7

Flat: parallel fibres, often w/ aponeurosis, can be broad (external oblique) or narrow (sartorius)

Pennate: feather like in arrangement of fascicles, can be uni (EDL), bi (rectus femoris) or multipennate (deltoid)

Fusiform: spindle shaped, round thick belly, tapered ends eg biceps brachii

Convergent: broad origin inserts to a single tendon eg pec M

Quadrate: 4 equal sides, eg pronator quadratus

Circular/Sphincteral: surround a body opening/orifice, constricting it when the muscle contracts eg orbicularis occuli (eyelids)

Multiheaded/bellied: >1 attachment head eg gastrocnemius

Question 8

types of contraction of muscles

Answer 8

Reflexive: automatic, though can be voluntarily controlled, eg respiratory muscles of diaphragm and movement after muscle stretch formed by tapping a tendon w/ a hammer

Tonic: Even when relaxed, muscles are contracted to a small degree -> muscle tone; this provides: muscle firmness, assisting stability of joints and maintenance of posture

Phasic: Isotonic (Eccentric and Concentric) and Isometric:

• Isotonic: ->Eccentric: muscle lengthens while exerting a controlled diminishing force, eg biceps when extending the forearm with a weight
• >Concentric: muscle shortens eg hamstrings when flexing the leg
• Isometric: muscle length remains the same but force alters, important when resisting gravity eg deltoid when a weight is put in the outstretched hand

Question 9

Muscle units

Answer 9

Structural unit: skeletal striated muscle fibre

Functional unit: motor unit, consisting of a motor neurone and the muscle fibres it innervates

Question 10

specific functional types of muscles in moving and positioning body

Answer 10

Prime mover/Agonists: main muscle responsible for producing a specific movement of the body, concentric cxn produced, in most movements there is one agonist, in some there are two working in equal measures

Fixators: steadies proximal part of the limb, isometric cxn

Synergists: complements the agonist either by: producing the same, but weaker, movement, or by acting as a fixators when the agonist acts over >1 joint

Antagonists: opposes the action of another muscle - a 1^o muscle opposes an agonist, a 2^o muscle opposes a synergist - eccentric cxn produces a smooth movement