HESI A2 Anatomy & Physiology
Insight Series 2025/2026 100%
Confirmed V1–V3 Answers and
Comprehensive System-Based Review
100% Confirmed V1–V3 Answers | Comprehensive System-Based Review 100 Questions –
Answers in red – Full Rationales
INTEGUMENTARY SYSTEM
1. The deepest layer of the epidermis is the: stratum basale
Rationale: The stratum basale (basal layer) is the deepest epidermal layer where mitosis occurs,
producing new keratinocytes that migrate upward.
2. Which protein provides skin with strength and elasticity? collagen
Rationale: Collagen fibers in the dermis provide tensile strength; elastin adds flexibility.
3. The arrector pili muscle contracts in response to: cold or fear
Rationale: Sympathetic stimulation causes contraction, raising hair ("goosebumps") for
insulation or emotional response.
4. The primary function of melanin is to: protect against UV radiation
Rationale: Melanin absorbs UV rays, preventing DNA damage in keratinocytes.
5. First-degree burns affect only the: epidermis
, Rationale: Superficial burns cause erythema and pain without blistering; heal in 3–6 days.
SKELETAL SYSTEM
6. The bone that forms the posterior cranial fossa is the: occipital bone
Rationale: The occipital bone contains the foramen magnum and supports the cerebellum.
7. Which type of bone is the patella? sesamoid
Rationale: Sesamoid bones develop within tendons; the patella is embedded in the quadriceps
tendon.
8. The primary mineral stored in bone is: calcium phosphate
Rationale: Hydroxyapatite crystals (calcium + phosphate) provide rigidity; 99% of body
calcium is in bone.
9. The epiphyseal plate is responsible for: lengthwise bone growth
Rationale: Cartilaginous growth plate allows longitudinal expansion until closure at puberty.
10. The axial skeleton includes: skull, vertebral column, and rib cage
Rationale: 80 bones; supports central body axis and protects vital organs.
MUSCULAR SYSTEM
11. The functional unit of skeletal muscle is the: sarcomere
Rationale: Sarcomere = Z-line to Z-line; contains actin and myosin for contraction.
Insight Series 2025/2026 100%
Confirmed V1–V3 Answers and
Comprehensive System-Based Review
100% Confirmed V1–V3 Answers | Comprehensive System-Based Review 100 Questions –
Answers in red – Full Rationales
INTEGUMENTARY SYSTEM
1. The deepest layer of the epidermis is the: stratum basale
Rationale: The stratum basale (basal layer) is the deepest epidermal layer where mitosis occurs,
producing new keratinocytes that migrate upward.
2. Which protein provides skin with strength and elasticity? collagen
Rationale: Collagen fibers in the dermis provide tensile strength; elastin adds flexibility.
3. The arrector pili muscle contracts in response to: cold or fear
Rationale: Sympathetic stimulation causes contraction, raising hair ("goosebumps") for
insulation or emotional response.
4. The primary function of melanin is to: protect against UV radiation
Rationale: Melanin absorbs UV rays, preventing DNA damage in keratinocytes.
5. First-degree burns affect only the: epidermis
, Rationale: Superficial burns cause erythema and pain without blistering; heal in 3–6 days.
SKELETAL SYSTEM
6. The bone that forms the posterior cranial fossa is the: occipital bone
Rationale: The occipital bone contains the foramen magnum and supports the cerebellum.
7. Which type of bone is the patella? sesamoid
Rationale: Sesamoid bones develop within tendons; the patella is embedded in the quadriceps
tendon.
8. The primary mineral stored in bone is: calcium phosphate
Rationale: Hydroxyapatite crystals (calcium + phosphate) provide rigidity; 99% of body
calcium is in bone.
9. The epiphyseal plate is responsible for: lengthwise bone growth
Rationale: Cartilaginous growth plate allows longitudinal expansion until closure at puberty.
10. The axial skeleton includes: skull, vertebral column, and rib cage
Rationale: 80 bones; supports central body axis and protects vital organs.
MUSCULAR SYSTEM
11. The functional unit of skeletal muscle is the: sarcomere
Rationale: Sarcomere = Z-line to Z-line; contains actin and myosin for contraction.
