1
A&P 1 101 MODULE 4 EXAM SKELETAL SYSTEM 2026/2027
| Portage Learning | Graded A+ | 100% Correct | Pass
Guaranteed
[Section 1: Bone Tissue & Osseous Histology (Q1-12)]
Q1. A histologist examining a bone biopsy observes large, multinucleated cells
actively resorbing bone matrix in a resorption bay (Howship's lacuna). Which cell type
is responsible for this activity?
A. Osteoblasts B. Osteocytes C. Osteoclasts D. Osteoprogenitor cells
Correct Answer: C
Rationale: Osteoclasts are large, multinucleated cells derived from
monocyte/macrophage lineage that secrete HCl and cathepsin K to dissolve
hydroxyapatite and digest collagen, creating resorption bays called Howship's
lacunae. Students commonly confuse osteoclasts with osteoblasts; osteoblasts are
mononucleated bone-forming cells, not multinucleated bone-destroying cells.
Q2. A bone sample reveals concentric rings of calcified matrix surrounding a central
canal containing blood vessels and nerves. Which structural unit is being described?
A. Trabecula B. Osteon (Haversian system) C. Lacuna D. Canaliculus
Correct Answer: B
Rationale: The osteon, or Haversian system, is the fundamental functional unit of
compact bone consisting of a central (Haversian) canal surrounded by concentric
lamellae, with osteocytes located in lacunae connected by canaliculi. Trabeculae are
the lattice-like structures of spongy bone, not concentric rings.
,2
Q3. A 45-year-old patient presents with brittle bones that fracture easily. Laboratory
analysis reveals normal calcium levels but significantly reduced organic matrix. Which
component deficiency is most likely responsible?
A. Hydroxyapatite crystals B. Collagen type I fibers C. Proteoglycans only D. Calcium
phosphate salts
Correct Answer: B
Rationale: Collagen type I constitutes approximately 35% of bone matrix (organic
portion) and provides tensile strength and flexibility; its deficiency (as in osteogenesis
imperfecta) causes brittle bones despite normal mineralization. Hydroxyapatite
provides compressive strength, so its deficiency would cause soft bones
(osteomalacia), not brittle bones.
Q4. During microscopic examination of compact bone, a student identifies tiny
channels radiating through the calcified matrix connecting lacunae to each other and
to the central canal. These channels are called:
A. Perforating (Volkmann's) canals B. Canaliculi C. Central (Haversian) canals D.
Endosteal canals
Correct Answer: B
Rationale: Canaliculi are microscopic channels containing osteocyte cytoplasmic
processes that allow nutrient/waste exchange and communication between
osteocytes in lacunae and the central canal via gap junctions. Perforating canals run
perpendicular to the long axis and connect osteons to each other and to the
periosteum.
Q5. A histology slide shows bone tissue with a porous, sponge-like appearance
containing red bone marrow between bony struts. No osteons are visible. Which type
of bone is being observed?
, 3
A. Compact (dense) bone B. Spongy (cancellous/trabecular) bone C. Woven
(immature) bone D. Lamellar (mature) bone
Correct Answer: B
Rationale: Spongy bone lacks osteons and instead consists of trabeculae (thin bony
struts) arranged along stress lines with spaces filled by red bone marrow; it is found
at epiphyses and within flat bones. Compact bone is dense with osteons and forms
the diaphyseal shaft exterior.
Q6. A bone cell trapped within its own secreted matrix, residing in a small cavity and
maintaining the surrounding bone tissue, is properly identified as:
A. An osteoblast that has become quiescent B. An osteoclast in a resorption bay C.
An osteocyte in a lacuna D. An osteoprogenitor cell in the periosteum
Correct Answer: C
Rationale: Osteocytes are mature bone cells derived from osteoblasts that become
embedded in the matrix they secreted, residing in lacunae and maintaining bone via
mechanosensing; they comprise 90-95% of all bone cells. Osteoblasts are surface-
lining cells before entrapment, and osteoclasts are on bone surfaces, not trapped
within matrix.
Q7. The inorganic component of bone matrix, providing compressive strength and
hardness, has the chemical formula Ca₁₀(PO₄)₆(OH)₂. This mineral compound is called:
A. Calcium carbonate B. Hydroxyapatite C. Calcium citrate D. Collagen-
hydroxyproline complex
Correct Answer: B
Rationale: Hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] is the primary inorganic mineral salt of
bone, comprising ~65% of bone weight and providing compressive strength; it is not
calcium carbonate (found in shells) or a collagen complex. The 35% organic matrix
(primarily type I collagen) provides tensile strength.
A&P 1 101 MODULE 4 EXAM SKELETAL SYSTEM 2026/2027
| Portage Learning | Graded A+ | 100% Correct | Pass
Guaranteed
[Section 1: Bone Tissue & Osseous Histology (Q1-12)]
Q1. A histologist examining a bone biopsy observes large, multinucleated cells
actively resorbing bone matrix in a resorption bay (Howship's lacuna). Which cell type
is responsible for this activity?
A. Osteoblasts B. Osteocytes C. Osteoclasts D. Osteoprogenitor cells
Correct Answer: C
Rationale: Osteoclasts are large, multinucleated cells derived from
monocyte/macrophage lineage that secrete HCl and cathepsin K to dissolve
hydroxyapatite and digest collagen, creating resorption bays called Howship's
lacunae. Students commonly confuse osteoclasts with osteoblasts; osteoblasts are
mononucleated bone-forming cells, not multinucleated bone-destroying cells.
Q2. A bone sample reveals concentric rings of calcified matrix surrounding a central
canal containing blood vessels and nerves. Which structural unit is being described?
A. Trabecula B. Osteon (Haversian system) C. Lacuna D. Canaliculus
Correct Answer: B
Rationale: The osteon, or Haversian system, is the fundamental functional unit of
compact bone consisting of a central (Haversian) canal surrounded by concentric
lamellae, with osteocytes located in lacunae connected by canaliculi. Trabeculae are
the lattice-like structures of spongy bone, not concentric rings.
,2
Q3. A 45-year-old patient presents with brittle bones that fracture easily. Laboratory
analysis reveals normal calcium levels but significantly reduced organic matrix. Which
component deficiency is most likely responsible?
A. Hydroxyapatite crystals B. Collagen type I fibers C. Proteoglycans only D. Calcium
phosphate salts
Correct Answer: B
Rationale: Collagen type I constitutes approximately 35% of bone matrix (organic
portion) and provides tensile strength and flexibility; its deficiency (as in osteogenesis
imperfecta) causes brittle bones despite normal mineralization. Hydroxyapatite
provides compressive strength, so its deficiency would cause soft bones
(osteomalacia), not brittle bones.
Q4. During microscopic examination of compact bone, a student identifies tiny
channels radiating through the calcified matrix connecting lacunae to each other and
to the central canal. These channels are called:
A. Perforating (Volkmann's) canals B. Canaliculi C. Central (Haversian) canals D.
Endosteal canals
Correct Answer: B
Rationale: Canaliculi are microscopic channels containing osteocyte cytoplasmic
processes that allow nutrient/waste exchange and communication between
osteocytes in lacunae and the central canal via gap junctions. Perforating canals run
perpendicular to the long axis and connect osteons to each other and to the
periosteum.
Q5. A histology slide shows bone tissue with a porous, sponge-like appearance
containing red bone marrow between bony struts. No osteons are visible. Which type
of bone is being observed?
, 3
A. Compact (dense) bone B. Spongy (cancellous/trabecular) bone C. Woven
(immature) bone D. Lamellar (mature) bone
Correct Answer: B
Rationale: Spongy bone lacks osteons and instead consists of trabeculae (thin bony
struts) arranged along stress lines with spaces filled by red bone marrow; it is found
at epiphyses and within flat bones. Compact bone is dense with osteons and forms
the diaphyseal shaft exterior.
Q6. A bone cell trapped within its own secreted matrix, residing in a small cavity and
maintaining the surrounding bone tissue, is properly identified as:
A. An osteoblast that has become quiescent B. An osteoclast in a resorption bay C.
An osteocyte in a lacuna D. An osteoprogenitor cell in the periosteum
Correct Answer: C
Rationale: Osteocytes are mature bone cells derived from osteoblasts that become
embedded in the matrix they secreted, residing in lacunae and maintaining bone via
mechanosensing; they comprise 90-95% of all bone cells. Osteoblasts are surface-
lining cells before entrapment, and osteoclasts are on bone surfaces, not trapped
within matrix.
Q7. The inorganic component of bone matrix, providing compressive strength and
hardness, has the chemical formula Ca₁₀(PO₄)₆(OH)₂. This mineral compound is called:
A. Calcium carbonate B. Hydroxyapatite C. Calcium citrate D. Collagen-
hydroxyproline complex
Correct Answer: B
Rationale: Hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] is the primary inorganic mineral salt of
bone, comprising ~65% of bone weight and providing compressive strength; it is not
calcium carbonate (found in shells) or a collagen complex. The 35% organic matrix
(primarily type I collagen) provides tensile strength.
