Memmler's Structure and Function of the Human Body, 12th
Edition - Cohen EXAM with Questions and Answers/Plus a
Rationale Updated 2026 A+/Instant Download PDF
EXAM COVERAGE
1. Organization of the Human Body and Chemistry of Life
2. Cells, Tissues, and the Integumentary System
3. Skeletal and Muscular Systems
4. Nervous System and Special Senses
5. Endocrine and Cardiovascular Systems
6. Blood, Lymphatic, and Immune Systems
7. Respiratory, Digestive, and Urinary Systems
8. Fluid, Electrolyte Balance, and Reproductive Systems
1. A 45-year-old male is admitted to the intensive care unit with severe dehydration secondary to
acute gastroenteritis. Laboratory findings reveal profound hypernatremia and elevated serum
osmolarity. Which physiological compensatory mechanism occurs across the cellular membrane
in response to this extracellular hyperosmolar environment?
A. Water shifts via osmosis from the intracellular fluid compartment into the extracellular fluid
compartment.
B. Solutes actively pump into the cell against the concentration gradient to maintain baseline
volume.
C. Sodium ions diffuse rapidly into the intracellular matrix to neutralize electrical charge
balance.
D. Potassium channels close permanently to prevent intracellular electrolyte leaking.
, CORRECT ANSWER : A
Rationale: In a hyperosmolar extracellular environment, water moves by osmosis from the
intracellular fluid to the higher solute concentration of the extracellular fluid, causing cellular
shrinkage (crenation). Active solute pumping does not counteract acute osmotic shifts of this
magnitude, and sodium and potassium dynamics are governed primarily by electrochemical
gradients and active transport pumps rather than direct neutralization.
2. A biomedical researcher is analyzing the transport kinetics of a specialized renal tubular cell line.
She discovers that a specific amino acid crosses the plasma membrane against its concentration
gradient by coupling its movement directly to the downhill electrochemical gradient of sodium
ions established by the Na+/K+ ATPase pump. What specific category of membrane transport
does this represent?
A. Simple diffusion through the lipid bilayer matrix
B. Primary active transport utilizing direct ATP hydrolysis
C. Secondary active transport (cotransport or symport)
D. Facilitated diffusion mediated by carrier protein channels
CORRECT ANSWER : C
Rationale: Secondary active transport utilizes the stored energy of an electrochemical gradient
established by primary active transport (such as the Na+/K+ pump) to move another substance
against its gradient in the same direction (symport) or opposite direction (antiport). Simple and
facilitated diffusion move substances down their concentration gradients without energy
coupling, while primary active transport directly hydrolyzes ATP.
3. Histological examination of a chronic smoker's bronchial biopsy reveals that the normal
pseudostratified ciliated columnar epithelium has been replaced by stratified squamous
epithelium. How should the pathologist categorize and explain this cellular adaptation?
A. Irreversible dysplasia progressing directly to aggressive anaplastic carcinoma.
B. Pathological atrophy resulting from prolonged cellular hypoxia and nutrient deprivation.
C. Metaplasia, representing a reversible substitution of one differentiated cell type for another
better suited to chronic irritation.
D. Hypertrophy characterized by massive enlargement of individual pseudostratified cells.
CORRECT ANSWER : C
, Rationale: Metaplasia is a reversible cellular adaptation where one adult cell type is replaced by
another cell type better able to withstand adverse environmental stressors, such as cigarette
smoke irritants. Dysplasia involves disordered growth and loss of uniformity, atrophy is cell
shrinkage, and hypertrophy is cell enlargement.
4. A clinical pharmacologist is evaluating a novel chemotherapeutic agent designed to arrest
actively dividing cancer cells during the metaphase stage of mitosis. Which specific cytoskeletal
structure targeted by this drug is responsible for forming the mitotic spindle apparatus?
A. Intermediate filaments composed of keratin subunits
B. Microfilaments composed of polymerized actin polymers
C. Microtubules composed of alpha- and beta-tubulin heterodimers
D. Myosin thick contractile cross-bridges within the cytoplasm
CORRECT ANSWER : C
Rationale: Microtubules are hollow cylindrical tubes composed of alpha- and beta-tubulin
heterodimers that form the mitotic spindle apparatus necessary for chromosomal segregation
during cell division. Microfilaments (actin) handle cell motility and cytokinesis, and intermediate
filaments provide mechanical structural support.
5. A 22-year-old female presents with severe sunburn after prolonged UV exposure at the beach.
Which specific epidermal layer contains actively dividing keratinocytes responsible for
continually regenerating the superficial epithelial layers destroyed by UV radiation?
A. Stratum corneum
B. Stratum lucidum
C. Stratum granulosum
D. Stratum basale
CORRECT ANSWER : D
Rationale: The stratum basale (stratum germinativum) is the deepest layer of the epidermis,
containing actively mitotic stem cells (keratinocytes) that continuously divide to replenish the
upper layers of the epidermis. The stratum corneum consists of dead, keratinized superficial
cells, while lucidum and granulosum represent intermediate maturation zones.
6. During a forensic bone analysis of an adult human skeleton, an anthropologist examines the
structural units of compact bone consisting of concentric lamellae arranged around a central
Haversian canal. What are these structural pillars called?
, A. Trabeculae
B. Osteons (Haversian systems)
C. Canaliculi networks
D. Epiphyseal growth plates
CORRECT ANSWER : B
Rationale: Osteons (Haversian systems) are the structural units of compact bone, consisting of
concentric rings of calcified matrix (lamellae) surrounding a central canal containing blood
vessels and nerves. Trabeculae form the lattice network of spongy bone, canaliculi are
microscopic nutrient canals, and epiphyseal plates mediate longitudinal bone growth.
7. A medical student reviews the sliding filament theory of muscle contraction. During the
contraction cycle of a skeletal muscle sarcomere, binding of calcium ions to which regulatory
protein triggers a conformational shift that exposes myosin-binding sites on actin filaments?
A. Myosin heavy chain head
B. Tropomyosin
C. Troponin complex
D. Dystrophin matrix
CORRECT ANSWER : C
Rationale: Calcium ions bind to the troponin complex, inducing a conformational shift that
moves tropomyosin away from the myosin-binding sites on the actin filament, enabling cross-
bridge formation. Myosin forms the thick filament, and dystrophin is a structural stabilization
protein.
8. An electrical impulse travels down a myelinated motor neuron axon to stimulate a skeletal
muscle fiber. Which ion influx across the postsynaptic motor end-plate sarcolemma generates the
end-plate potential that triggers an action potential?
A. Potassium efflux through voltage-gated channels
B. Sodium influx through ligand-gated acetylcholine receptor channels
C. Calcium release from the intracellular sarcoplasmic reticulum
D. Chloride influx through inhibitory channel pores
Edition - Cohen EXAM with Questions and Answers/Plus a
Rationale Updated 2026 A+/Instant Download PDF
EXAM COVERAGE
1. Organization of the Human Body and Chemistry of Life
2. Cells, Tissues, and the Integumentary System
3. Skeletal and Muscular Systems
4. Nervous System and Special Senses
5. Endocrine and Cardiovascular Systems
6. Blood, Lymphatic, and Immune Systems
7. Respiratory, Digestive, and Urinary Systems
8. Fluid, Electrolyte Balance, and Reproductive Systems
1. A 45-year-old male is admitted to the intensive care unit with severe dehydration secondary to
acute gastroenteritis. Laboratory findings reveal profound hypernatremia and elevated serum
osmolarity. Which physiological compensatory mechanism occurs across the cellular membrane
in response to this extracellular hyperosmolar environment?
A. Water shifts via osmosis from the intracellular fluid compartment into the extracellular fluid
compartment.
B. Solutes actively pump into the cell against the concentration gradient to maintain baseline
volume.
C. Sodium ions diffuse rapidly into the intracellular matrix to neutralize electrical charge
balance.
D. Potassium channels close permanently to prevent intracellular electrolyte leaking.
, CORRECT ANSWER : A
Rationale: In a hyperosmolar extracellular environment, water moves by osmosis from the
intracellular fluid to the higher solute concentration of the extracellular fluid, causing cellular
shrinkage (crenation). Active solute pumping does not counteract acute osmotic shifts of this
magnitude, and sodium and potassium dynamics are governed primarily by electrochemical
gradients and active transport pumps rather than direct neutralization.
2. A biomedical researcher is analyzing the transport kinetics of a specialized renal tubular cell line.
She discovers that a specific amino acid crosses the plasma membrane against its concentration
gradient by coupling its movement directly to the downhill electrochemical gradient of sodium
ions established by the Na+/K+ ATPase pump. What specific category of membrane transport
does this represent?
A. Simple diffusion through the lipid bilayer matrix
B. Primary active transport utilizing direct ATP hydrolysis
C. Secondary active transport (cotransport or symport)
D. Facilitated diffusion mediated by carrier protein channels
CORRECT ANSWER : C
Rationale: Secondary active transport utilizes the stored energy of an electrochemical gradient
established by primary active transport (such as the Na+/K+ pump) to move another substance
against its gradient in the same direction (symport) or opposite direction (antiport). Simple and
facilitated diffusion move substances down their concentration gradients without energy
coupling, while primary active transport directly hydrolyzes ATP.
3. Histological examination of a chronic smoker's bronchial biopsy reveals that the normal
pseudostratified ciliated columnar epithelium has been replaced by stratified squamous
epithelium. How should the pathologist categorize and explain this cellular adaptation?
A. Irreversible dysplasia progressing directly to aggressive anaplastic carcinoma.
B. Pathological atrophy resulting from prolonged cellular hypoxia and nutrient deprivation.
C. Metaplasia, representing a reversible substitution of one differentiated cell type for another
better suited to chronic irritation.
D. Hypertrophy characterized by massive enlargement of individual pseudostratified cells.
CORRECT ANSWER : C
, Rationale: Metaplasia is a reversible cellular adaptation where one adult cell type is replaced by
another cell type better able to withstand adverse environmental stressors, such as cigarette
smoke irritants. Dysplasia involves disordered growth and loss of uniformity, atrophy is cell
shrinkage, and hypertrophy is cell enlargement.
4. A clinical pharmacologist is evaluating a novel chemotherapeutic agent designed to arrest
actively dividing cancer cells during the metaphase stage of mitosis. Which specific cytoskeletal
structure targeted by this drug is responsible for forming the mitotic spindle apparatus?
A. Intermediate filaments composed of keratin subunits
B. Microfilaments composed of polymerized actin polymers
C. Microtubules composed of alpha- and beta-tubulin heterodimers
D. Myosin thick contractile cross-bridges within the cytoplasm
CORRECT ANSWER : C
Rationale: Microtubules are hollow cylindrical tubes composed of alpha- and beta-tubulin
heterodimers that form the mitotic spindle apparatus necessary for chromosomal segregation
during cell division. Microfilaments (actin) handle cell motility and cytokinesis, and intermediate
filaments provide mechanical structural support.
5. A 22-year-old female presents with severe sunburn after prolonged UV exposure at the beach.
Which specific epidermal layer contains actively dividing keratinocytes responsible for
continually regenerating the superficial epithelial layers destroyed by UV radiation?
A. Stratum corneum
B. Stratum lucidum
C. Stratum granulosum
D. Stratum basale
CORRECT ANSWER : D
Rationale: The stratum basale (stratum germinativum) is the deepest layer of the epidermis,
containing actively mitotic stem cells (keratinocytes) that continuously divide to replenish the
upper layers of the epidermis. The stratum corneum consists of dead, keratinized superficial
cells, while lucidum and granulosum represent intermediate maturation zones.
6. During a forensic bone analysis of an adult human skeleton, an anthropologist examines the
structural units of compact bone consisting of concentric lamellae arranged around a central
Haversian canal. What are these structural pillars called?
, A. Trabeculae
B. Osteons (Haversian systems)
C. Canaliculi networks
D. Epiphyseal growth plates
CORRECT ANSWER : B
Rationale: Osteons (Haversian systems) are the structural units of compact bone, consisting of
concentric rings of calcified matrix (lamellae) surrounding a central canal containing blood
vessels and nerves. Trabeculae form the lattice network of spongy bone, canaliculi are
microscopic nutrient canals, and epiphyseal plates mediate longitudinal bone growth.
7. A medical student reviews the sliding filament theory of muscle contraction. During the
contraction cycle of a skeletal muscle sarcomere, binding of calcium ions to which regulatory
protein triggers a conformational shift that exposes myosin-binding sites on actin filaments?
A. Myosin heavy chain head
B. Tropomyosin
C. Troponin complex
D. Dystrophin matrix
CORRECT ANSWER : C
Rationale: Calcium ions bind to the troponin complex, inducing a conformational shift that
moves tropomyosin away from the myosin-binding sites on the actin filament, enabling cross-
bridge formation. Myosin forms the thick filament, and dystrophin is a structural stabilization
protein.
8. An electrical impulse travels down a myelinated motor neuron axon to stimulate a skeletal
muscle fiber. Which ion influx across the postsynaptic motor end-plate sarcolemma generates the
end-plate potential that triggers an action potential?
A. Potassium efflux through voltage-gated channels
B. Sodium influx through ligand-gated acetylcholine receptor channels
C. Calcium release from the intracellular sarcoplasmic reticulum
D. Chloride influx through inhibitory channel pores
