D312 ANATOMY AND PHYSIOLOGY I - Set 3 - Part 3

Correct Answer: Deltoid

Option d is correct because the deltoid is the large triangular muscle covering the shoulder that serves as the primary mover for abducting the arm, lifting it directly outward away from the body. Option a is incorrect because the teres major is a smaller muscle that assists with adduction and medial rotation of the arm, which are movements toward the body rather than away from it. Option b is incorrect because the pectoralis major is a large chest muscle that primarily performs adduction, flexion, and medial rotation of the humerus, not the abduction movement described. Option c is incorrect because the latissimus dorsi is a broad back muscle that primarily extends, adducts, and medially rotates the arm, performing the opposite of the abduction movement described.

Correct Answer: Biceps brachii

Option a is correct because the biceps brachii is one of the primary flexor muscles located in the anterior compartment of the arm, responsible for flexing the elbow and supinating the forearm. Option b is incorrect because the triceps brachii is located in the posterior compartment of the arm and functions as the primary extensor of the elbow, performing the opposite action of flexion. Option c is incorrect because the deltoid is a shoulder muscle responsible for arm abduction and is not located in the anterior arm compartment where the elbow flexor muscles are found. Option d is incorrect because while the brachioradialis assists with elbow flexion, it is classified as a forearm muscle rather than being part of the anterior arm compartment with the biceps brachii.

Correct Answer: Serratus anterior

Option c is correct because the serratus anterior is positioned along the lateral chest wall and functions to protract the scapula while holding it firmly against the thoracic rib cage during movement. Option a is incorrect because the rhomboid major is a posterior muscle located between the spine and scapula that retracts the scapula, pulling it toward the midline rather than protracting it forward. Option b is incorrect because the pectoralis minor is an anterior chest muscle that depresses and protracts the scapula but is not the muscle specifically described as running along the lateral chest wall. Option d is incorrect because the trapezius is a large superficial back muscle with upper, middle, and lower fibers that elevate, retract, and depress the scapula respectively, rather than protracting it.

Correct Answer: Hypothenar group

Option b is correct because the hypothenar group contains the muscles specifically responsible for controlling movements of the little finger, including the flexor digiti minimi brevis and opponens digiti minimi. Option a is incorrect because the thenar group is the set of intrinsic hand muscles associated with the thumb, not the little finger, controlling movements like opposition and adduction of the thumb. Option c is incorrect because the mid-palmar group includes the lumbricals and interossei muscles that control movements of the fingers in general, not specifically the dedicated little finger muscle group. Option d is incorrect because the dorsal interossei are part of the mid-palmar group and function to abduct the fingers away from the midline of the hand rather than being a dedicated little finger group.

Correct Answer: Triceps brachii

Option d is correct because the triceps brachii is the sole muscle in the posterior compartment of the arm and serves as the primary extensor responsible for straightening the elbow joint. Option a is incorrect because the biceps brachii is located in the anterior compartment of the arm and functions as a flexor and supinator, performing the opposite movement of elbow extension. Option b is incorrect because the brachialis is an anterior arm compartment muscle positioned deep to the biceps that assists with elbow flexion, not the extension movement being assessed here. Option c is incorrect because the supinator is a forearm muscle responsible for rotating the forearm so the palm faces upward and is not involved in the extension of the elbow joint.

Correct Answer: Gluteus maximus

Option a is correct because the gluteus maximus is the largest and most powerful gluteal muscle, serving as the primary extensor of the hip joint used during climbing, rising, and powerful leg movements. Option b is incorrect because the gluteus medius is a smaller gluteal muscle that primarily performs abduction of the hip, moving the leg outward away from the midline rather than extending it backward. Option c is incorrect because the gluteus minimus is the smallest of the three gluteal muscles and primarily assists with hip abduction along with the gluteus medius, not hip extension. Option d is incorrect because the iliacus is a hip flexor muscle that works with the psoas major to flex the hip, performing the opposite movement of the extension produced by the gluteus maximus.

Correct Answer: Adduction

Option c is correct because the medial thigh compartment contains the adductor muscles, including the adductor magnus and gracilis, which pull the leg inward toward the midline of the body. Option a is incorrect because knee extension is the primary action of the anterior thigh compartment muscles, specifically the quadriceps group, not the medial compartment adductor muscles that move the leg inward. Option b is incorrect because hip flexion is primarily performed by the iliopsoas muscles and the rectus femoris, not by the medial thigh compartment muscles whose main function is pulling the leg toward midline. Option d is incorrect because abduction moves the leg outward away from the midline, which is the opposite of adduction, and is primarily performed by the gluteal muscles rather than the medial thigh compartment.

Correct Answer: Schwann cells

Option d is correct because Schwann cells are the glial cells of the peripheral nervous system responsible for producing the myelin sheath that insulates axons, mirroring the role of oligodendrocytes in the CNS. Option a is incorrect because astrocytes are glial cells found exclusively in the central nervous system where they provide structural support, not in the peripheral nervous system where myelination is needed. Option b is incorrect because microglia are immune surveillance cells found in the central nervous system that perform phagocytosis of pathogens and debris, not myelin production in peripheral nerves. Option c is incorrect because satellite cells are glial cells in the peripheral nervous system that provide support to neuron cell bodies in ganglia, but they do not produce the myelin sheaths around axons.

Correct Answer: Abductor hallucis

Option b is correct because the abductor hallucis is a plantar foot muscle that specifically abducts the great toe, moving it away from the other toes, with "hallucis" referring to the big toe. Option a is incorrect because the extensor digitorum brevis is a dorsal foot muscle that extends the toes and is located on the top of the foot rather than the plantar surface discussed in the question. Option c is incorrect because the extensor hallucis brevis is also a dorsal foot muscle that extends the great toe and is not one of the plantar muscles found on the bottom of the foot. Option d is incorrect because the abductor digiti minimi is a plantar muscle that abducts the little toe, not the great toe, with "digiti minimi" specifically referring to the smallest toe.

Correct Answer: Fibularis longus and fibularis brevis

Option a is correct because the fibularis longus and fibularis brevis are the lateral compartment muscles of the lower leg that primarily perform eversion, turning the sole of the foot outward. Option b is incorrect because the tibialis anterior performs dorsiflexion in the anterior compartment while the tibialis posterior assists with inversion in the deep posterior compartment, neither performing eversion. Option c is incorrect because the gastrocnemius and soleus are superficial posterior compartment muscles that perform plantar flexion of the ankle, not the eversion movement turning the sole outward. Option d is incorrect because the flexor digitorum longus and flexor hallucis longus are deep posterior compartment muscles that flex the toes and assist with plantar flexion, not lateral eversion.