Bones and Joints and Anatomical Terminology

Question 1

What are the two major divisions of the skeleton and what are they used for?

Answer 1

• The axial skeleton (skull, vertebral column, sternum and ribs) forms the longitudinal axis of the body and protects vital structures (brain, spinal cord, heart and lungs). The trunk is made of the ribs, sternum, vertebrae and sacrum.
• The appendicular skeleton (upper and lower limbs and pectoral and pelvic girdles that attach the extremities to the axial skeleton. It provides the body with mobility.

Question 2

Describe the functions of bone.

Answer 2

Mechanical functions:
Support- rigid framework, protection of vital structures
Movement- site of attachment for muscles and acts as lever around joints
Physiological functions:
Haemopoesis (red bone marrow)
Mineral storage (calcium hydroxyapatite- important in calcium homeostasis)
Emergency lipid store (yellow marrow)

Question 3

List the types of bone with examples.

Answer 3

Long bone – clavicle, humerus
Short bone – carpals and tarsals – cuboidal shape
Irregular bone – vertebral column, bones of face
Flat bone – skull – serve protection purposes, scapula
Sesamoid bone – pisiform and patella – bones on tendons which cross the ends of long bone, protecting the tendon from excessive wear and changes the angle of the tendon.

Question 4

List the types of tissue located between joints.

Answer 4

Bone, cartilage, fibrocartilage, ligaments, bursae, synovial membrane.

Question 5

What is a bursa?

Answer 5

A bursa is a small fluid-filled sac lined by synovial membrane with an inner capillary layer of viscous fluid. It provides a cushion between bones and tendons and/or muscles around a joint.

Question 6

What does stability of joints depend on?

Answer 6

• Ligaments- prevent excessive movement- can tear
• Muscle tone
• Shape, size and arrangement of articulating bones (the depth of bony articulation)

Question 7

What are the factors that restrict movement around a joint?

Answer 7

• Ligaments
• Muscle tension (harder to raise thigh if knee straight)
• Interference from other structures
• Depth of bony articulation (less stable- more mobile)

Question 8

How are joints classified?

Answer 8

Structural classification (material in joint):
-Fibrous joint - sutures – tight union between bones of the adult skull. Syndesmoses – bones held together by fibrous tissue eg interosseous membrane between radius and ulna and tibia and fibula.
-Cartilaginous joint:
Primary cartilaginous joint – epiphyseal growth plate in long bones
Secondary cartilaginous joint – disc of fibrocartilage in the joint space e.g. pubic symphysis, intervertebral joint
-Synovial joint – protective fibrous joint capsule, articular surfaces covered by hyaline cartilage and separated by joint cavity, joint cavity lined by synovial membrane which secretes synovial fluid.
Functional classification:
-Synarthrosis – immovable
-Amphiarthrosis – slightly movable
-Diarthrosis – freely movable – synovial joint

Question 9

Describe different types of synovial joint with examples.

Answer 9

Hinge joint – flexion/extension – knee and elbow
Ball and socket joint – flexion/extension, abduction/adduction, external and internal rotation – shoulder and hip
Pivot joint – rotation around another bone – top of neck
Saddle joint – CMC joint of thumb – flexion/extension, abduction/adduction, circumduction
Condyloid joint – wrist, MCP and MTP joints – flexion/extension, abduction/adduction, circumduction
Gliding joint – intercarpal joints

Question 10

What is Hilton’s law?

Answer 10

A nerve that supplies the joint will also supply the muscles moving the joint and the overlying skin.

Question 11

List some problems that can occur with joints.

Answer 11

• Rheumatoid arthritis (autoimmune disease attacking the synovium)
• Osteoarthritis (loss of cartilage, bones rub together (may hear crepidis), pain
• Dislocation of joints
• Ligament tear
• Haemoarthrosis (blood in the synovial cavity)
• Joint effusions (excessive synovial fluid in joint cavity)

Question 12

Describe sagittal, coronal and transverse planes.

Answer 12

Sagittal plane divides right from left
Coronal place divides anterior from posterior
Transverse plane divides superior from inferior

Question 13

What is the metaphysis?

Answer 13

Adjacent to the epiphysial growth plate. It is the part of the bone that grows in length during childhood by endochondral ossification.

Question 14

Can cartilage be converted to bone? Explain.

Answer 14

In foetal development, much of the skeleton starts off as cartilage, which develops into bone by endochondral (and some intramembranous) ossification.
In addition, when repairing a broken bone, a fibrocartilaginous callus is formed, which is later converted to bone by endochondral ossification.

Question 15

What factors are responsible for the appearance of tuberosities, tubercles, ridges and grooves on a typical long bone.

Answer 15

Tuberosites, tubercles and ridges occur due to mechanical forces applied to the bone by the attachment of muscle, tendons and ligaments.
Grooves are formed from pressures exerted on the bone by adjacent nerves and vessels.

Question 16

What is the function of erythropoietin and red bone marrow?

Answer 16

Erythropoietin is released from the kidneys in response to hypoxia and targets the bone marrow, accelerating release and production of erythrocytes. This increases oxygen carrying capacity of the blood so that oxygen levels are restored.
Red bone marrow- production of red blood cells, white blood cells and platelets.

Question 17

An irregular, fixed lump is found on a patient’s breast what might this be?

Answer 17

The lump may be a carcinoma which has attached to other chest tissues e.g. pectoral fascia and may invade the chest wall further to invade the pectoralis major muscle ( C7,C8,T1).
Surgical removal of the tumour will result in removing an extensive part of this muscle. Flexion, adduction and medial rotation of the arm will be compromised.

Question 18

What specific tissues of joints are affected in rheumatoid arthritis and osteoarthritis?

Answer 18

RA: inflammatory response of the synovium, resulting in an increase in synovial fluid secondary to swelling (turgescence) of synovial cells, excess synovial fluid and development of fibrous tissue (pannus) in the synovium.
OA: involves degradation of articular cartilage and some of the underlying bone (usually mechanical). Causes narrowing of the joint space.

Question 19

Describe intramembranous ossification and endochondral ossification.

Answer 19

Intramembranous ossification takes place in flat bones e.g. scapula and bone is formed directly from mesenchymal tissue.
-Mesenchymal cells differentiate into osteoblasts which lay down osteoid
-Osteoid ( bone matrix) becomes calcified
-Extensive trabeculae form to produce spongy bone
-Peripheral regions become compact bone (series of haversian canals with trapped osteocytes)
Endochondral ossification replaces hyaline cartilage for bone and takes place in long bones e.g. clavicle.
-The mesenchymal cells in the perichondrium differentiate into osteoblasts and start laying down osteoid in the primary ossification site, the diaphysis.
-The chondrocytes proliferate, mature and hypertrophy
-The matrix becomes calcified which kills the chondrocytes (loss of nutrients) and osteoblasts replace them
-Growth in diameter occurs as the diaphysis
-The secondary ossification site is the epiphysis
-The epiphyseal growth plate remains during puberty until adulthood allowing growth in length as cartilage cells divide, mature and hypertrophy, the metaphysis grows.
-The growth plate eventually ossifies and growth in length can no longer occur.