Chapter 7 - Cartilage and Bone

Question 1

Which of the following statements character­izes osteoclasts?
(A) They are enucleated cells.
(B) They produce collagen.
(C) They secrete osteoid.
(D) They are derived from osteoprogenitor
cells.
(E) They occupy Howship lacunae.

Answer 1

E. Osteoclasts are multinucleated cells that produce proteolytic enzymes and occupy Howship lacunae. They are not derived from osteoprogenitor cells but from monocyte precursors (see Chapter 7 II C 4).

Question 2

Which one of the following statements is
correct concerning the periosteum?
(A) It is devoid of a blood supply.
(B) It produces osteoclasts.
(C) It is responsible for interstitial bone
growth.
(D) Its inner layer contains osteoprogenitor cells.
(E)
Its outer layer is devoid of fibers.

Answer 2

D. The inner layer of the periosteum possesses osteoprogenitor cells, whereas the outer layer of the periosteum is fibrous. The periosteum functions to distribute blood vessels to the bone; thus, appositional bone growth takes place here (see Chapter 7 II B 2).

Question 3

Which one of the following statements is characteristic of osteocytes?
(A) They communicate via gap junctions between their processes.
(B) They contain large amounts of RER.
(C) They are immature bone cells.
(D) They are housed as isogenous groups in
lacunae.
(E) They give rise to osteoclasts.

Answer 3

A. Osteocytes communicate with each other via gap junctions on narrow cytoplasmic pro­cesses that extend through canaliculi. They are mature bone cells that occupy individual lacu­nae as mature resting bone cells (see Chapter 7 II C 3).

Question 4

Which one of the following statements con­cerning hyaline cartilage is correct?
(A) It is vascular.
(B) It contains type IV collagen.
(C) It undergoes appositional growth only.
(D) It is located at the articular ends of long
bones.
(E) Its chondrocytes are aligned in rows.

Answer 4

D. Hyaline cartilage is a vascular, contains type II collagen, and grows both interstitially and appositionally. It is located at the articulating ends o flong bones (see Chapter 7 I A).

Question 5

A 7-year-old boy is seen by his pediatrician because the child broke his humerus as he tripped and fell while walking. The pediatrician asked about the child's diet and learned that he might have a dietary deficiency. Which of the following may be lacking in his diet?
(A) Potassium
(B) Calcium
(C) Iron
(D) Carbohydrates
(E) Protein

Answer 5

B. Because calcium must be maintained at a constant level in the blood and the tissues, a diet deficient in calcium leads to calcium loss from the bones. As a result, the bones become fragile (see Chapter 7 II C 4 Clinical Considerations).

Question 6

A 22-year-old woman is seen for the first time by her new physician, who notes that she has verythick bones in her extremities and face. The physician suspects acromegaly, caused by which of the following?
(A) Hypervitaminosis A
(B) Excess growth hormone
(C) Hypovitaminosis A
(D) Hypervitaminosis D
(E) Hypovitaminosis D

Answer 6

B. Excessive growth hormone causes acromegaly. Excessive vitamin D causes bone resorption. Both an excess and a deficiency of vitamin A result in short stature (see Chapter 7 II J Clinical Considerations).

Question 7

Which of the following statements is characteristic of bone?
(A) Bone matrix contains primarily type II collagen.
(B) About 65% of the dry weight of bone is organic.
(C) Haversian canals are interconnected via Volkmann canals.
(D) Bone growth occurs via interstitial growth only.
(E) Bone growth occurs via appositional growth only.

Answer 7

C. Haversian canals run longitudinally, parallel to the long axis of bone. They are connected to one another by Volkmann canals that run perpendicular (or obliquely) to them (see Chapter 7 II E 1).

Question 8

Which one of the following inhibits
histogenesis of cartilage?
(A) Thyroxine
(B) Hypervitaminosis A
(C) Hypovitaminosis D
(D) Hydrocortisone
(E) Hypovitaminosis C

Answer 8

D. Hydrocortisone inhibits cartilage growth and matrix formation (see Chapter 7 I A 2).

Question 9

Which one of the following stimulates cartilage histogenesis?
(A) Thyroxine
(B) Hypervitaminosis A
(C) Hypovitaminosis D
(D) Hydrocortisone
(E) Hypovitaminosis C

Answer 9

A. Thyroxine, testosterone, and somatotropin stimulate cartilage growth and matrix formation
(see Chapter 7 I A 2).

Question 10

Which one of the following accelerates epiphyseal ossification?
(A) Thyroxine
(B) Hypervitaminosis A
(C) Hypovitaminosis D
(D) Hydrocortisone
(E) Hypovitaminosis C

Answer 10

B. Hypervitaminosis A accelerates ossification of epiphyseal plates, whereas hypovitaminosis A reduces the width of the epiphyseal plates (see Chapter 7 II I).

Question 11

Which one of the following makes epiphyseal cartilage matrix fail to calcify?
(A) Thyroxine
(B) Hypervitaminosis A
(C) Hypovitaminosis D
(D) Hydrocortisone
(E) Hypovitaminosis C

Answer 11

C. In the absence of vitamin D, epiphyseal chondrocytes continue to proliferate, but their matrix does not calcify, which leads to rickets (see Chapter 7 II I Clinical Considerations).

Question 12

A 25-year-old patient, anemic for several years, complains of failing eyesight and hearing loss. During a physical examination, it is deter­mined that the patient has lost function of some of the cranial nerves. The diagnosis could be which one of the following?
(A) Osteoporosis
(B) Osteomalacia
(C) Rickets
(D) Acromegaly
(E) Osteopetrosis

Answer 12

E. Osteopetrosis is a genetic defect involving the osteoclasts. Persons with this defect possess osteoclasts without ruffled borders, which prohibit them from resorbing bone. Therefore, bone forms but is not resorbed. This leads to increased bone density, anemia, blindness, deafness, and cranial nerve involvement because the nerves are impinged upon as they exit the cranium via their foramina (see Chapter 7 II B Clinical Considerations).