UNIT 3: The Human Musculoskeletal System

Question 1

structure and function of the human skeleton

Answer 1

• shape and support.
• protection: of internal organs.
• movement: muscles use skeleton as levers.
• production of red and white blood cells.
• hearing: ossicles vibrate and amplify vibrations.
• ingestion and digestion: physical digestion in the mouth.
• storage: of minerals (calcium and phosphorus) that can be taken by the body when needed.

Question 2

axial skeleton

Answer 2

80 bones including:

• skull
• ossicles
• spine
• ribs
• sternum

Question 3

skull

Answer 3

also known as the cranium.

consists of 8 fused bones and facial bones.

Question 4

vertebral column

Answer 4

consists of 33 small bones which appear as only 26 due to fusion of the vertebrae of the sacrum (5 fused vertebrae) and coccyx (4 fused vertebrae)

Question 5

vertebrae

Answer 5

• protect the spinal cord.

- give support to thoracic cavity and abdomen.

Question 6

invertebral discs

Answer 6

• located between each vertebra - held in by ligaments.
• elastic and compressible.
• provide flexibility and act as shock absorbers.
• can ‘slip’ - when soft centre of disc bulges out. it is called prolapsed invertebral disc. can push against nerve often causing severe pain.

Question 7

ossicles

Answer 7

consist of 3 small bones - smallest in the body.

• hammer (malleus)
• anvil (incus)
• stirrup (stapes)

Question 8

ribs

Answer 8

• 12 pairs originate from the vertebral column.
• 7 pairs are ‘true ribs’ (attached directly to sternum).
• 3 pairs are ‘false ribs’ (attached indirectly to the sternum by only cartilage).
• 2 pairs are ‘floating ribs’ (attached to spine only).

Question 9

appendicular skeleton

Answer 9

consists of 126 bones including:

• pelvic girdle
• pectoral girdle
• scapula
• clavicle
• limbs
• arms: humerus, radius, ulna, carpals, metacarpals, phalanges.
• legs: femur, tibia, fibula, tarsals, metatarsals, phalanges.

Question 10

macroscopic anatomy of long bone

Answer 10

• bone is a mixture of organic 35% and inorganic 65% material.
• periosteum - thin layer of connective tissue that covers the outer surface of bone in all places except at joints (which are protected by articular cartilage).

Question 11

macroscopic anatomy of long bone: compact bone

Answer 11

dense and forms the surface of bones (80% of the weight of human skeleton).
Hard with very few gaps.
Function: support and protection

Question 12

macroscopic anatomy of long bone: medullary cavity

Answer 12

Central cavity of the bone shaft where yellow marrow (adipose tissue) is stored.
Located in the main shaft of the bone (diaphysis).
In children this area is also involved in the formation of red blood cells, so red marrow is present.
Function: storage of fat and formation of red blood cells in children.

Question 13

macroscopic anatomy of long bone: spongy bone

Answer 13

Found at the expanded heads of long bones.
Low density and low strength but very high surface area.
Fills the inner cavity of long bones.
In some bones the spaces are filled with red bone marrow where the production of blood cells occurs.
Contains most of the arteries and veins.
Function: production of red blood cells and delivery of oxygen and nutrients.

Question 14

macroscopic anatomy of long bone: cartilage

Answer 14

Type of dense connective tissue.
Composed of collagenous fibres and/or elastic fibres which are embedded in a firm gel-like ground substance called the matrix.
Cartilage is avascular (contains no blood vessels) and nutrients can only diffuse through the matrix.
Cartilage is found in many places in the body including the joints, rib cage, ear, nose, bronchial tubes and between intervertebral discs.
Functions: provides framework upon which bone deposition can begin and supplies smooth surfaces for the movement of articulating bones.

Question 15

joints

Answer 15

• immovabe - fused joints of the skull
• slightly moveable - vertebral joints
• free-moving / synovial
• ball-and-socket joints of the shoulder and hip.
• hinge joints like elbow and knee

Question 16

ligaments

Answer 16

strong, slightly elastic bands of fibrous tissue (collagen) - they control the range of movement in a joint.

Question 17

tendons

Answer 17

extremely strong, inelastic bands/cords of collagen - they attach muscles to bone

Question 18

skeletal muscle

Answer 18

• contractile tissue - has ability to shorten and generate a pulling force.
• voluntary muscle - we can consciously control contractions of skeletal muscles.
  Function: movement and temperature regulation in the body as they generate a lot of heat during movement.

Question 19

antagonistic muscle pairs

Answer 19

pairs of muscles where the action of each pulls the attached bone in the opposite direction to the other.
most of the bodys 700 muscles operate as part of antagonistic muscle pairs.
e.g. biceps and triceps in upper arm.
e.g. hamstrings and quadriceps in upper leg

Question 20

musculoskeletal disorder - osteoporosis

Answer 20

• brittle-bone disease - bones are porous / less dense.
• often results in compression fractures in the vertebrae and in the neck of the femur (broken hip).
• possible cause: bone replacement has slowed down.
• prevention: physical exercise during puberty reduces risk of developing the disease in old age.
• calcium-rich diet and drinking flourinated water maintains bone density.
• treatment: females use HRT (but bone material already lost is not replaced)
• physical exercise, dietary calcium and vitamin D are recommended

Question 21

regions of the vertebral column

Answer 21

cervical - 7 
thoracic - 12
lumbar - 5
sacral - 5
coccygeal - 4

Question 22

growth and development in bones

Answer 22

• skeleton of early embryo is mostly cartilage.
• bone formation begins just before week 8.
• specialised cells called osteoblasts secrete a thick layer of bone around the cartilage of the diaphysis - a tube of bone now encircles the diaphysis.
• cartilage continues to grow at ends - epiphyses - bone elongates.
• after birth the epiphyses start to calcify.
• cartilage remains at the junctions between the diaphysis and epiphyses - this area is called the growth plate.
• the growth plate enables the bone to elongate during childhood and puberty and eventually calcify and are replaced by bone at the end of puberty when fully grown - 18 in females, 21 in males.

Question 23

bone renewal

Answer 23

• bone is a living organ and is capable of self renewal.
• bone is constantly broken down and replaced (parathormone involved).
• skeleton is completely replaced every 7 years and complete replacement slows down with age.
• oesteoclasts remove calcium and osteoblasts lay calcium down.
• renewal of bones is affected by the hormone parathormone (secreted by the parathyroids) but also by exercise levels and Dietary calcium.

Question 24

Osteoblasts

Answer 24

A bone forming cell

Question 25

Growth plate

Answer 25

The area between the epiphysis and the diaphysis in a long bone within which bone growth occurs

Question 26

Osteoclasts

Answer 26

Bone digesting cell

Question 27

Synovial fluid

Answer 27

Produced in moveable joints to lubricarte and reduce friction