Skeletal System Questions and Answers

Answer: C

The correct match is a-II, b-III, c-IV, d-I.

• Humerus, the bone of the upper arm: paired here with II, Hand (the upper limb).
• Femur, the thigh bone: III, Leg.
• Parietal bone, forming the sides and roof of the skull: IV, Head.
• Sternum, the breastbone: I, Thorax.

The other options misplace at least one bone. For example, the first pairs the humerus with the thorax, and the second pairs it with the head; only the third option puts every bone in its region.

Answer: C

Cattle have 7 cervical vertebrae.

Almost all mammals, from mice to giraffes, have seven neck (cervical) vertebrae; a long neck comes from longer vertebrae, not more of them. The bovine vertebral formula is C7, T13, L6, S5 and Cy18-20.

5 and 6 are too few, and 8 is not found in cattle. Birds are the group with varying and larger numbers of cervical vertebrae.

Answer: B

Pneumatic bones are found in the bird.

Pneumatic bones are hollow bones whose cavities are filled with air and connected to the air sacs of the respiratory system. They make the skeleton light without losing strength, an adaptation for flight. In the fowl the humerus is the classic example.

Mammals such as goats, dogs and mice have marrow-filled long bones; their only air-filled bony spaces are the sinuses of the skull.

Answer: D

The space is occupied by bone marrow.

Bone marrow fills the medullary cavity of long bones and the spaces between the trabeculae of spongy (cancellous) bone. Red marrow produces blood cells; with age much of the marrow in the medullary cavity becomes fatty yellow marrow.

Lymph is a fluid that flows in lymphatic vessels, and the thymus and spleen are separate lymphoid organs. None of them lies inside bone.

Answer: D

The hardness of bone is mainly due to Calcium phosphate.

The mineral part of bone is mostly calcium phosphate in the form of hydroxyapatite crystals, laid down on a framework of collagen fibres. The crystals give bone its hardness and the collagen gives it some flexibility.

Calcium carbonate is present only in small amounts. Calcium sulphate is not a significant bone mineral, and 'calcium disulphate' is not a constituent of bone.

Answer: A

The pisiform bone is in the wrist.

It is one of the eight carpal bones, the small pea-shaped bone in the proximal row on the little-finger side. It sits within the tendon of flexor carpi ulnaris, which makes it a sesamoid bone, and can be felt at the base of the palm.

The ankle is made of the tarsal bones (talus, calcaneus and others), the spine of vertebrae, and the skull of cranial and facial bones such as the frontal, parietal and mandible. None of them includes the pisiform.

Answer: B

The shoulder joint is a ball and socket joint.

At the shoulder (glenohumeral) joint the rounded head of the humerus, the ball, fits into the shallow glenoid cavity of the scapula, the socket. This allows movement in all planes: flexion, extension, abduction, adduction and rotation. The hip is the other ball and socket joint of the limbs.

A hinge joint, such as the elbow or knee, moves in one plane only. A pivot joint, such as the joint between the atlas and axis, allows rotation. A saddle joint is found at the base of the thumb, between the trapezium and the first metacarpal.

Answer: A

Hyperextension is prevented by the anterior longitudinal ligament.

The anterior longitudinal ligament is a broad, strong band along the front of the vertebral bodies and discs, from the occiput to the sacrum. Because it lies in front of the column, it is stretched when the spine bends backwards and so limits extension. It is the ligament torn in whiplash hyperextension injuries.

The posterior longitudinal ligament, the ligamentum flavum and the interspinous ligament all lie behind the vertebral bodies. They tighten in flexion, so they limit forward bending, not hyperextension.