MUSCULOSKELETAL DISORDERS QUESTIONS AND
ANSWERS WITH RATIONALES/GRADED A+/2026
UPDATE/100% CORRECT /INSTANT DOWNLOAD
Section 1: Anatomy & Physiology of Bone, Joint &
Muscle
1. The functional unit of compact bone is the:
A) Osteon (Haversian system)
B) Trabecula
C) Canaliculus
D) Lamella
Rationale: The osteon, or Haversian system, is the cylindrical structural unit of
compact bone. It consists of concentric lamellae of bone matrix surrounding a
central Haversian canal containing blood vessels and nerves.
2. Which cells are responsible for bone resorption?
A) Osteoclasts
B) Osteoblasts
C) Osteocytes
D) Chondrocytes
Rationale: Osteoclasts are large, multinucleated cells derived from hematopoietic
stem cells (monocyte/macrophage lineage) that break down bone tissue through
acidification and enzymatic degradation. Osteoblasts form bone; osteocytes are
mature bone cells that maintain matrix.
3. Which cells synthesize and secrete the organic matrix of bone (osteoid)?
A) Osteoclasts
B) Osteoblasts
,C) Osteocytes
D) Chondroblasts
Rationale: Osteoblasts are bone-forming cells derived from mesenchymal stem
cells. They synthesize and secrete osteoid (unmineralized bone matrix composed
primarily of type I collagen) and regulate mineralization.
4. The organic component of bone matrix is primarily composed of:
A) Type I collagen
B) Type II collagen
C) Type IV collagen
D) Elastin
Rationale: Type I collagen makes up about 90% of the organic bone matrix,
providing tensile strength and flexibility. Type II collagen is found in cartilage; Type
IV in basement membranes.
5. The inorganic component of bone matrix is primarily:
A) Calcium phosphate (hydroxyapatite)
B) Calcium hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂]
C) Calcium carbonate
D) Magnesium phosphate
Rationale: Hydroxyapatite crystals (calcium phosphate) constitute the inorganic
mineral component of bone, providing compressive strength and rigidity. They are
deposited on the collagen framework.
6. Which hormone is the primary regulator of calcium homeostasis and acts to
increase serum calcium?
A) Calcitonin
B) Parathyroid hormone (PTH)
C) Vitamin D (active form - calcitriol)
D) Estrogen
Rationale: PTH is the major hormone regulating calcium homeostasis. It increases
serum calcium by stimulating osteoclastic bone resorption, increasing renal
,calcium reabsorption, and activating vitamin D to enhance intestinal calcium
absorption.
7. Which hormone lowers serum calcium by inhibiting osteoclast activity?
A) Calcitonin
B) Parathyroid hormone (PTH)
C) Vitamin D
D) Growth hormone
Rationale: Calcitonin, produced by the parafollicular (C) cells of the thyroid gland,
lowers serum calcium by inhibiting osteoclast activity and bone resorption. Its
physiologic role in humans is minor compared to PTH.
8. Synovial joints are characterized by:
A) A joint cavity containing synovial fluid, articular cartilage, and a fibrous
capsule
B) Direct bone-to-bone fusion
C) Fibrocartilage connecting bones
D) Hyaline cartilage connecting bones
Rationale: Synovial joints (diarthroses) are freely movable joints with a synovial
cavity, articular cartilage, synovial membrane, and a fibrous joint capsule.
Examples include the knee, shoulder, and hip.
9. Articular cartilage is composed of:
A) Hyaline cartilage (type II collagen and proteoglycans)
B) Fibrocartilage (type I collagen)
C) Elastic cartilage
D) Dense fibrous connective tissue
Rationale: Articular cartilage is hyaline cartilage composed of chondrocytes
embedded in a matrix of type II collagen and proteoglycans (aggregans). It
provides a smooth, low-friction surface for joint movement and absorbs shock.
10. Which of the following is NOT a component of the synovial joint?
A) Synovial fluid
B) Articular cartilage
, C) Joint capsule
D) Intervertebral disc
Rationale: Intervertebral discs are fibrocartilaginous structures between vertebrae,
forming cartilaginous joints (symphyses), not synovial joints. They are not part of a
synovial joint.
11. The primary neurotransmitter at the neuromuscular junction that stimulates
muscle contraction is:
A) Acetylcholine (ACh)
B) Norepinephrine
C) Dopamine
D) Serotonin
Rationale: Acetylcholine is the neurotransmitter released from the motor neuron
at the neuromuscular junction. It binds to nicotinic receptors on the muscle
endplate, causing depolarization and muscle contraction.
12. The contractile unit of skeletal muscle is the:
A) Myofibril
B) Myosin filament
C) Sarcomere
D) Fascicle
Rationale: The sarcomere is the basic functional unit of striated muscle, extending
from Z-line to Z-line. It contains overlapping actin (thin) and myosin (thick)
filaments and is responsible for muscle contraction via the sliding filament theory.
13. Which muscle fiber type is most resistant to fatigue and is rich in
mitochondria and myoglobin?
A) Type I (slow-twitch oxidative)
B) Type IIa (fast-twitch oxidative-glycolytic)
C) Type IIb (fast-twitch glycolytic)
D) Type III
ANSWERS WITH RATIONALES/GRADED A+/2026
UPDATE/100% CORRECT /INSTANT DOWNLOAD
Section 1: Anatomy & Physiology of Bone, Joint &
Muscle
1. The functional unit of compact bone is the:
A) Osteon (Haversian system)
B) Trabecula
C) Canaliculus
D) Lamella
Rationale: The osteon, or Haversian system, is the cylindrical structural unit of
compact bone. It consists of concentric lamellae of bone matrix surrounding a
central Haversian canal containing blood vessels and nerves.
2. Which cells are responsible for bone resorption?
A) Osteoclasts
B) Osteoblasts
C) Osteocytes
D) Chondrocytes
Rationale: Osteoclasts are large, multinucleated cells derived from hematopoietic
stem cells (monocyte/macrophage lineage) that break down bone tissue through
acidification and enzymatic degradation. Osteoblasts form bone; osteocytes are
mature bone cells that maintain matrix.
3. Which cells synthesize and secrete the organic matrix of bone (osteoid)?
A) Osteoclasts
B) Osteoblasts
,C) Osteocytes
D) Chondroblasts
Rationale: Osteoblasts are bone-forming cells derived from mesenchymal stem
cells. They synthesize and secrete osteoid (unmineralized bone matrix composed
primarily of type I collagen) and regulate mineralization.
4. The organic component of bone matrix is primarily composed of:
A) Type I collagen
B) Type II collagen
C) Type IV collagen
D) Elastin
Rationale: Type I collagen makes up about 90% of the organic bone matrix,
providing tensile strength and flexibility. Type II collagen is found in cartilage; Type
IV in basement membranes.
5. The inorganic component of bone matrix is primarily:
A) Calcium phosphate (hydroxyapatite)
B) Calcium hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂]
C) Calcium carbonate
D) Magnesium phosphate
Rationale: Hydroxyapatite crystals (calcium phosphate) constitute the inorganic
mineral component of bone, providing compressive strength and rigidity. They are
deposited on the collagen framework.
6. Which hormone is the primary regulator of calcium homeostasis and acts to
increase serum calcium?
A) Calcitonin
B) Parathyroid hormone (PTH)
C) Vitamin D (active form - calcitriol)
D) Estrogen
Rationale: PTH is the major hormone regulating calcium homeostasis. It increases
serum calcium by stimulating osteoclastic bone resorption, increasing renal
,calcium reabsorption, and activating vitamin D to enhance intestinal calcium
absorption.
7. Which hormone lowers serum calcium by inhibiting osteoclast activity?
A) Calcitonin
B) Parathyroid hormone (PTH)
C) Vitamin D
D) Growth hormone
Rationale: Calcitonin, produced by the parafollicular (C) cells of the thyroid gland,
lowers serum calcium by inhibiting osteoclast activity and bone resorption. Its
physiologic role in humans is minor compared to PTH.
8. Synovial joints are characterized by:
A) A joint cavity containing synovial fluid, articular cartilage, and a fibrous
capsule
B) Direct bone-to-bone fusion
C) Fibrocartilage connecting bones
D) Hyaline cartilage connecting bones
Rationale: Synovial joints (diarthroses) are freely movable joints with a synovial
cavity, articular cartilage, synovial membrane, and a fibrous joint capsule.
Examples include the knee, shoulder, and hip.
9. Articular cartilage is composed of:
A) Hyaline cartilage (type II collagen and proteoglycans)
B) Fibrocartilage (type I collagen)
C) Elastic cartilage
D) Dense fibrous connective tissue
Rationale: Articular cartilage is hyaline cartilage composed of chondrocytes
embedded in a matrix of type II collagen and proteoglycans (aggregans). It
provides a smooth, low-friction surface for joint movement and absorbs shock.
10. Which of the following is NOT a component of the synovial joint?
A) Synovial fluid
B) Articular cartilage
, C) Joint capsule
D) Intervertebral disc
Rationale: Intervertebral discs are fibrocartilaginous structures between vertebrae,
forming cartilaginous joints (symphyses), not synovial joints. They are not part of a
synovial joint.
11. The primary neurotransmitter at the neuromuscular junction that stimulates
muscle contraction is:
A) Acetylcholine (ACh)
B) Norepinephrine
C) Dopamine
D) Serotonin
Rationale: Acetylcholine is the neurotransmitter released from the motor neuron
at the neuromuscular junction. It binds to nicotinic receptors on the muscle
endplate, causing depolarization and muscle contraction.
12. The contractile unit of skeletal muscle is the:
A) Myofibril
B) Myosin filament
C) Sarcomere
D) Fascicle
Rationale: The sarcomere is the basic functional unit of striated muscle, extending
from Z-line to Z-line. It contains overlapping actin (thin) and myosin (thick)
filaments and is responsible for muscle contraction via the sliding filament theory.
13. Which muscle fiber type is most resistant to fatigue and is rich in
mitochondria and myoglobin?
A) Type I (slow-twitch oxidative)
B) Type IIa (fast-twitch oxidative-glycolytic)
C) Type IIb (fast-twitch glycolytic)
D) Type III
