Skeletal system

Question 1

What are the major functions of the skeletal system?

Answer 1

• Support
• Movement
• Protection
• Blood cell production
• Fat storage
• Calcium storage

Question 2

Describe the supportive function of the skeleton.

Answer 2

Provides a rigid framework to support the soft tissues of the body

Question 3

Describe the movement function of the skeleton

Answer 3

Articular joints facilitate movement of the body when bones are acted upon by skeletal muscle

Question 4

Describe the protective function of the skeleton

Answer 4

The skeleton protects vulnerable regions of the body, e.g. the skull protects the brain, the
ribcage protects the heart and lungs

Question 5

How does the skeleton produce blood cells?

Answer 5

Red bone marrow produces the formed
elements of blood including: Erythrocytes (red blood cells), leukocytes (white blood cells) and
platelets (thrombocytes)

Question 6

How does the skeleton store fat?

Answer 6

Many bones (particularly long bones) are hollow
and filled with yellow bone marrow which is adipose tissue (fat)

Question 7

How does the skeleton store calcium?

Answer 7

The skeleton acts as a reservoir for calcium with calcium deposited in bones when plasma
calcium levels are high and released from the skeleton into the blood when plasma calcium levels are low.

Question 8

What are the two major divisions of the skeleton?

Answer 8

• The axial skeleton
• The appendicular skeleton

Question 9

The axial skeleton

Answer 9

Consists predominantly of the bones which are located on the central axis of the body.
Includes; skull, spinal column, ribcage and sacral area of pelvic gridle

Question 10

The appendicular skeleton

Answer 10

Consists predominantly of the bones of the
arms and legs (appendages) together with the lateral components of the pelvic girdle

Question 11

What are the major structural components of the bone and what are their roles?

Answer 11

Organic component = collagen - prevents fragmentation
Inorganic component = predominantly calcium phosphate - impacts hardness and rigidty of the bone

Question 12

Describe the structure of a typical long bone

Answer 12

• Longer than they are wide e.g. humerus and femur
• Mostly found in appendicular skeleton within the arms and legs
• Function primarily as levers to facilitate movement
• Each long bone consists of a diaphysis and the epiphyses regions.
• Diaphysis: The shaft of a long bone is composed of incredibly strong compact bone (also known as cortical bone). Running longitidudinally through the length of the diaphysis there is usually hollow cavity termed the medullary cavity which is filled with yellow bone marrow (fat).
• Epiphyses: Each long bone has a proximal epiphysis (close to the trunk of the body) and a distal epiphysis (away from the trunk of the body). The epiphyses are the bulbous ends of a long bone and are predominantly composed of softer spongy bone (also known as cancellous bone) which may contain small amounts of red bone marrow.

Question 13

Describe the structure of a typical flat bone

Answer 13

• Flat bones have a thin, flattened appearance e.g. the sternum; many are also curved e.g. the ribs and several of the major bones that form the skull
• Most flat bones are located in the axial skeleton where they cover and protect vulnerable areas of the body, e.g. the ribs protect the heart and
  lungs
• Flat bones have a characteristic sandwich-like structure
• Each flat bone has outer layers of compact bone and an inner core of spongy (also known as cancellous) bone.
• This structure is excellent at absorbing physical impacts since the spongy bone at the centre is slightly deformable allowing impact forces to
  be effectively dissipated.
• Within the spongy bone at the core of a flat bone the second type of bone marrow called red bone marrow is located.
• Red bone marrow is part of the lymphatic system and functions as the primary organ of haematopoiesis (the formation of blood cells).

Question 14

Differentiate between a simple fracture and a compound fracture.

Answer 14

Simple fracture = Where only the bone itself is broken with limited damage to the surrounding tissues
Compound fracture = Here the bone is fractured and penetrates the surrounding tissues and usually out through the skin.
- Since bones are innervated and have a rich blood supply, fractures are incredibly painful and the fracture will result in bleeding and
haemotoma (collection of blood) formation
- It is important to be aware that fractures also have the potential to damage major blood vessels in proximity to the bone and occasionally bone splinters may enter blood vessels to form emboli (bone embolus).

Question 15

Describe how bone density is regulated

Answer 15

• When blood calcium levels rise (e.g. when drinking a pint of milk) the thyroid gland releases
  the hormone calcitonin.
  Calcitonin directs excess calcium into the bones increasing bone density, this explains why dairy products (which are rich in calcium) are promoted as being excellent for strong bones and teeth.
• When the blood calcium level is low e.g. when calcium intake in the diet is inadequate or during pregnancy when the foetus is taking calcium from the mother’s blood to build its skeleton,
  the parathyroid glands release parathyroid hormone (PTH).
  PTH stimulates the release of calcium from the bones and teeth ensuring a stable level of calcium in the blood. It is essential that calcium
  levels in the blood are maintained since calcium is a blood clotting factor as well as being essential for muscle contraction, cell division and many other physiological process.

Question 16

What are the two major types of joints?

Answer 16

• Fixed joints
• Articular joints

Question 17

Fixed joints

Answer 17

• As implied by the name these joints are usually non-articular (non-movable) and are most
  frequently found where bones need to
  be joined together.
• Fixed joints include the sutures of the skull and some of the joints which fuse portions of the pelvis together.
• The sutures of the skull are knitted
  together primarily by collagen fibres
  and for this reason these types of
  fixed joints are also commonly
  referred to as fibrous joints.

Question 18

Articular joints

Answer 18

These are the most common joints in the body and allow movement (articulation) of bones.

Articular joints consist of:
Outer fibrous joint capsule: This is composed of connective tissue and elastic ligaments (which connect bone to bone); these allow the integrity and proximity of the bones to be maintained, whilst still allowing free movement.

Inner joint capsule: This is lined by a synovial membrane which secretes synovial fluid, this acts as an internal lubricant within the joint reducing friction as the joint articulates. The ends of each bone are usually covered in a fairly robust layer of articular cartilage. This type of cartilage is
incredibly smooth and allows the bones to glide over each other during movement, this gliding movement is aided by the synovial fluid which
lubricates the surfaces of the cartilage.