HESI A2 Anatomy and Physiology practice questions

Correct answer: D

Simple squamous epithelium consists of a single layer of thin, flat cells, which allows rapid diffusion and filtration. It is found in lung alveoli and blood vessel walls.

Why the other options are wrong:
A: Protection against abrasion is provided by stratified squamous epithelium, which has multiple layers.
B: Stretching is a property of transitional epithelium, found in the urinary bladder.
C: Secretion and absorption are functions of simple cuboidal or columnar epithelium, which have more cytoplasm and organelles.

Correct answer: B

After the stomach, food enters the duodenum (first part of small intestine), then the jejunum, then the ileum. It then passes into the cecum (first part of large intestine), followed by the ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. Option A is the only correct sequence.

Why the other options are wrong:
A: The small intestine order is reversed (ileum first) and the colon order starts with ascending but misses cecum.
C: The order of the small intestine is incorrect (jejunum before duodenum) and the colon order is reversed (descending before transverse).
D: The small intestine order is incorrect (ileum before jejunum) and the colon order has descending before transverse.

Correct answer: A

Osteoclasts are large, multinucleated cells that secrete acids and enzymes to dissolve bone matrix, releasing calcium and phosphate into the bloodstream. This process is essential for bone remodeling and calcium homeostasis.

Why the other options are wrong:
B: Osteoblasts are responsible for bone formation (deposition of new bone matrix), not resorption.
C: Osteocytes are mature bone cells that maintain the bone matrix and regulate mineral exchange; they do not actively resorb bone.
D: Chondrocytes are cells found in cartilage, not in bone tissue, and are involved in cartilage maintenance and growth.

Correct answer: D

ACTH from the anterior pituitary acts directly on the adrenal cortex (zona fasciculata) to stimulate cortisol secretion.

Why the other options are wrong:
A: Epinephrine is released by the adrenal medulla; it does not directly stimulate cortisol release.
B: CRH from the hypothalamus stimulates ACTH release, so it acts on the pituitary, not on the adrenal cortex.
C: Aldosterone is a separate adrenal cortex hormone that regulates sodium and potassium; it does not trigger cortisol release.

Correct answer: C

The urinary system, via the kidneys, regulates blood volume and composition, including fluid and electrolyte balance. The respiratory system regulates oxygen and carbon dioxide levels; the endocrine system secretes hormones that affect many processes but does not directly filter blood; the digestive system breaks down food and absorbs nutrients.

Why the other options are wrong:
A: The endocrine system uses hormones to regulate various functions but does not directly control fluid and electrolyte balance.
B: The respiratory system primarily exchanges gases (O₂ and CO₂), not fluid and electrolytes.
D: The digestive system is responsible for breaking down food and absorbing nutrients, not for maintaining fluid and electrolyte balance.

Correct answer: C

The skin provides barrier protection against pathogens and helps regulate temperature via sweat evaporation and blood flow changes. Severe burns damage these functions directly. Sensation and vitamin D synthesis are also affected but the primary risks are infection and temperature dysregulation.

Why the other options are wrong:
A: Excretion (sweat) and melanin production (pigment) are affected, but they are secondary to protection and thermoregulation in this scenario.
B: Blood reservoir (vasodilation/constriction) and keratinization (tough outer layer) are part of thermoregulation and protection, but the option does not explicitly name protection and thermoregulation as the primary compromised functions.
D: Sensation and vitamin D synthesis are functions of the skin, but they are not the most directly compromised in terms of infection risk and temperature regulation.

Correct answer: B

This is the Bohr effect: higher CO₂ and lower pH shift the oxygen-hemoglobin dissociation curve to the right. Hemoglobin's affinity for oxygen drops, so more oxygen is released to the working muscle.

Why the other options are wrong:
A: A left shift occurs with alkalosis and low CO₂, the opposite of conditions in exercising muscle.
C: pH directly changes hemoglobin's oxygen affinity, which is the basis of the Bohr effect.
D: A right shift decreases affinity and increases oxygen release, so this choice pairs the right shift with the wrong effect.

Correct answer: C

Negative feedback reverses a deviation from the set point—here, high temperature triggers responses to cool the body. Positive feedback amplifies a change, feedforward anticipates a change, and the process actually maintains homeostasis, not disrupts it.

Why the other options are wrong:
A: Feedforward control involves anticipatory responses before a change occurs, not after the fact.
B: The process is a homeostatic mechanism that corrects the disruption, not a disruption itself.
D: Positive feedback amplifies a change (e.g., childbirth contractions), it does not reverse a deviation.

Correct answer: C

The withdrawal reflex is processed in the spinal cord through a reflex arc: sensory neurons relay the signal to interneurons and motor neurons in the cord, which activate the muscles. The pain signal travels to the brain separately, so the hand moves before pain is felt.

Why the other options are wrong:
A: The cerebellum coordinates balance and smooth voluntary movement, but it does not integrate spinal withdrawal reflexes.
B: The cerebral cortex is where pain is consciously perceived, which happens after the hand has already moved.
D: The hypothalamus regulates temperature, hunger and hormone release; it is not part of the withdrawal reflex arc.

Correct answer: C

At high altitude, less oxygen reaches the tissues. The kidneys sense this hypoxia and secrete more erythropoietin, which stimulates the bone marrow to produce more red blood cells over several weeks.

Why the other options are wrong:
A: Iron is needed to build hemoglobin, but extra iron alone does not signal the marrow to make more red cells.
B: Erythropoietin production increases with hypoxia, and less of it would lower the red cell count.
D: Reduced marrow activity would lower the red cell count, not raise it.