basic concepts in MSK

Question 1

functions of skeletal muscle

Answer 1

locomotion- contraction of muscles acting across a joint lead to movement of that joint
posture 
metabolic 
venous return 
heat production 
continence

Question 2

what connects bone to bone

Answer 2

ligaments

Question 3

what connects muscle to bone

Answer 3

tendons

Question 4

what is fascia

Answer 4

sheets of connective tissue that envelop groups of muscles and divide body parts into anatomical compartments.

Question 5

discuss the difference between hyaline (articular) cartilage and fibrocartilage

Answer 5

hyaline cartilage is found on the end of bones contributing to joints. It’s very smooth and helps to create almost frictionless motion at the joint. is avascular
fibrocartilage has a higher collagen content. involved in shock absorption and increases bony congruity at joints. Menisci of the knee is made from this.

Question 6

discuss the blood supply to bones

Answer 6

nutrient artery supplies the marrow and enters Bible through the nutrient firemen near the middle of the diaphysis.
periosteal arteries supply the periosteum and the outer third of the cortex of bone.
some bones like the femur have metaphyseal arteries that enter at the site of attachment of the capsule.
in a child the metaphyseal arteries don’t cross the growth plate so the secondary ossification centre is completely dependent on the epiphyseal artery .

Question 7

what is avascular necrosis and what are the causes

Answer 7

death of bone due to loss of its blood supply
fracture
risk factors :alcoholism , excessive steroid use , other trauma , radiation , thrombosis, hypertension ,decompression sickness

Question 8

what are the three classifications of joints and examples

Answer 8

fibrous joints - united by collagen fibres. limited mobility so high stability. e.g sutures of the skull , inferior tibiofibular joint, posterior sacroiliac joint, joint between roots of a tooth and the bone of the mandible or maxilla
cartilaginous joints- use cartilage to unite bones. they are typically found in the midline of the body and also in the epiphyseal plates of long bones. can be divided into primary cartilaginous joints and secondary cartilaginous joints. primary are united by hyaline cartilage and are completely immobile. secondary are also known as symphyses and are covered with hyaline cartilage with a pad of fibrocartilage in between .
synovial joints- has joint cavity with synovial fluid. this provides lubroication so synovial joints have a high degree of mobility.. articulating surfaces of synovial joints are covered with hyaline cartilage

Question 9

describe the structure of a synovial joint

Answer 9

fibrous capsule surrounding the joint which stabilises the joint and permits movement but resits dislocation. its continuous with the periosteum covering the surface of adjacent bones.
synovial membrane thar produces synovial fluid lines the joint capsule, tendon sheaths and bursae.

Question 10

what are the different types of synovial joints

Answer 10

plane- 2 flat surfaces slid against each other.
condyloid- 2 elliptical joints nested together . no rotation
Saddle – named due to its resemblance to a saddle on a horse’s back. It is characterised by opposing articular surfaces with a reciprocal concave-convex shape.
Hinge – permits movement in one plane – usually flexion and extension.
Pivot – allows for rotation only. It is formed by a central bony pivot, which is surrounded by a bony-ligamentous ring
Ball and Socket – where the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone. It permits free movement in numerous axes.

Question 11

what is bursa

Answer 11

small sac lined by synovial membrane and contains a thin layer of synovial fluid. it provides a cushion between bones and tendons and /or muscles around a joint. helps reduce friction between bones and allows free movement.
tendon sheaths are elongated bursae wrapped around tendons.

Question 12

functions of synovial fluid

Answer 12

reduce friction
act as a shock absorber
transport nutrients to and remove waste from the articular cartilage of the joint .

Question 13

what factors will influence the range of motion of individual joints?

Answer 13

structure/shape of the articulating bones
strength and tension of the joint ligaments
arrangement and tone of muscles around joint
apposition of neighbouring soft tissues- are they restricting movement
effect of hormones
disuse of a joint

Question 14

what are the key principles of muscles

Answer 14

they can only pull and not push

can only act of joints that they or their tendons cross

Question 15

what is a synergist

Answer 15

muscle that act to assist the prime mover

e.g sartorius is a synergist of hip flexion

Question 16

what is a neutraliser

Answer 16

prevents unwanted actions that an agonist can perform. e.g gluteus Maximus can stabilise the hip joint in the extended portion whilst rectus femurs extends the knee without it rectus femurs would also flex the hip.

Question 17

what’s a fixator(stabiliser )

Answer 17

act to hold a body part immobile whilst another body part is moving

Question 18

what are the 3 types of contraction

Answer 18

Concentric (shortening)
Eccentric (lengthening)
Isometric (same length)

Question 19

how can skeletal muscle fibres be arranged

Answer 19

Parallel: subdivided into strap, fusiform and fan-shaped (triangular or convergent).
Pennate: subdivided into unipennate, bipennate and multipennate. Pennate muscles have one or more aponeuroses running through the muscle body from the tendon
Circular

Question 20

why can a pennate muscle generate more force than a parallel muscle

Answer 20

A pennate muscle can generate a greater force than a parallel muscle of the same length as it has a greater number of muscle fibres. However, the amount of shortening achieved is less than for a parallel muscle, so there is a trade-off between force generation and movement.

Question 21

what is the difference between deep fascia and superficial fascia

Answer 21

superficial fascia is a subcutaneous fatty layer. found under the skin ,surrounding organs , glands, neurovascular bundles etc
serves as a storage medium for fat and water, passageway for lymphatics, nerves, blood vessels and as a protective padding for organs.
deep fascia is a thickened elaboration of epimysium enveloping the muscle compartments and compromises collagen bundles and elastin fibres.

Question 22

what are tendons

Answer 22

connect muscle to bone

anchored to bone by sharpey’s fibres

Question 23

what are Aponeuroses

Answer 23

sheet-like structures

connect muscle to muscle

Question 24

what is Hilton’s law

Answer 24

the nerves supplying the muscles moving the joint also supply the joint capsule and the skin overlying the insertions of these muscles.

Question 25

what is segmentation in the early embryology controlled by

Answer 25

hox genes

Question 26

what is a homeotic mutation

Answer 26

mutation that causes tissues to alter their normal differentiation pattern producing integrated structures in unusual locations.

Question 27

how are the limbs formed (embryology)

Answer 27

limb buds first appear as small projections on the lateral body wall during 4th week of development.
the limb bud consists of a mass of mesenchyme covered by a layer of ectoderm. the ectodermal cells on the tip divide to form an apical ectodermal ridge.
the limb buds elongate by the proliferation of mesenchyme. in the early embryo the limb buds project laterally from the trunk.
the developing upper and lower limbs rotate. upper limb rotates 90 degrees laterally and lower limb 90 degrees medially.