Explanation

(Option B) Inferior mesenteric artery: The superior rectal artery is a continuation of the inferior mesenteric artery. It supplies blood to the upper part of the rectum.

(Option A) Internal iliac artery: The internal iliac artery is responsible for supplying blood to the pelvic organs and the gluteal region. It does not directly give rise to the superior rectal artery.

(Option C) Middle rectal artery: The middle rectal artery is a branch of the internal iliac artery, and it supplies blood to the middle part of the rectum. It is not directly involved in the continuation of the superior rectal artery.

(Option D) Common iliac artery: The common iliac artery is a large vessel that branches into the internal iliac artery and the external iliac artery. While it is related to the blood supply of the pelvic region, it does not directly give rise to the superior rectal artery.

(Option E) Emerging from the external iliac artery:The superior rectal artery does not emerge directly from the external iliac artery.

Subject: Anatomy

System/ Title: Abdomen

Topic: Rectal Arterial Supply

Explanation

The primary site responsible for the production of red blood cells, also known as hematopoiesis, is the red marrow. Red marrow is primarily found in the trabecular or spongy bone. Trabecular bone has a porous and lattice-like structure, providing spaces for the red marrow to house blood-forming cells.

(Option C) Trabecular bone: Trabecular bone, also known as spongy or cancellous bone, contains spaces filled with red marrow, where hematopoiesis occurs. This makes it the correct option for the production of red blood cells.

(Option A) Yellow marrow: Yellow marrow is found in the central cavities of long bones and consists mainly of adipose (fat) cells. It is not actively involved in the production of red blood cells but does play a role in fat storage.

(Option B) Compact bone: Compact bone forms the outer layer of bones and is dense and strong. While it provides structural support and protection, it is not the primary site for red blood cell production. The red marrow is usually found within the trabecular or spongy bone.

(Option D) Spongy bone: Spongy bone is another term for trabecular bone. It is not responsible for the production of red blood cells per se, but rather provides structural support and flexibility to bones.

(Option E) Medullary cavity: The medullary cavity is a central cavity within the diaphysis of long bones, and it contains both yellow and red marrow. However, the term “red marrow” is more specifically associated with trabecular bone, making option C more accurate in the context of red blood cell production.

Subject: Anatomy

System/ Title: General (Skeletal System)

Topic: Hematopoiesis in Bones

Explanation

(Option D) Infratrochlear nerve: The infratrochlear nerve is a branch of the nasociliary nerve, which is a branch of the ophthalmic division of the trigeminal nerve (V1). It primarily supplies sensory innervation to the skin over the medial canthus of the eye, the lacrimal sac area, and the upper eyelid. It does not play a significant role in supplying the scalp with sensory fibers.

(Option A) Auriculotemporal nerve: The auriculotemporal nerve is a branch of the mandibular division of the trigeminal nerve (V3). While it primarily supplies sensory innervation to the skin of the temporal region and the external ear, it does provide some sensory fibers to the scalp. These fibers contribute to the overall sensory perception of the scalp, although the auriculotemporal nerve’s main focus is on the temporal region and external ear.

(Option B) Zygomatic nerve: The zygomatic nerve is a branch of the maxillary division of the trigeminal nerve (V2). It plays a role in providing sensory innervation to the skin over the zygomatic bone (cheekbone) and the temple area. While its primary focus is not the scalp, it does contribute to the sensory input in the general facial region, which includes parts of the scalp.

(Option C) Occipital nerve: The occipital nerve is actually a branch of the cervical plexus, derived from the cervical spinal nerves (C2 and C3). It is responsible for providing sensory innervation to the posterior scalp and the skin over the posterior neck region. It does not originate directly from the trigeminal nerve, so it is not related to the scalp’s innervation through the trigeminal nerve branches.

(Option E) Supraorbital nerve: A branch of the ophthalmic division of the trigeminal nerve, the supraorbital nerve supplies sensation to the forehead and scalp above the eyes.

Subject: Anatomy

System/ Title: Head & Neck

Topic: Trigeminal Nerve and Scalp Innervation

Explanation

(Option B) The gluteus medius muscle: The gluteus medius muscle is located in the buttock region and is responsible for hip abduction. When a patient is in the supine position with the hip and knee joints extended and is asked to abduct the lower limb against resistance, it specifically tests the strength of the gluteus medius muscle. This muscle is essential for maintaining stability and balance during activities like walking and standing on one leg.

(Option A) The semitendinosus muscle: The semitendinosus muscle is one of the hamstring muscles located in the back of the thigh. It primarily functions to flex the knee and extend the hip. Testing its strength would typically involve different movements, such as knee flexion or hip extension, rather than abduction of the lower limb.

(Option C) The pectineus muscle: The pectineus muscle is located in the front of the thigh and is primarily involved in hip flexion and adduction. Testing its strength would typically involve movements related to these functions, rather than abduction.

(Option D) The gracilis muscle: The gracilis muscle is also located in the inner thigh and is involved in hip adduction and knee flexion. Similar to the pectineus, it is not the primary muscle responsible for hip abduction.

(Option E) The semimembranosus muscle: The semimembranosus muscle is another hamstring muscle, like the semitendinosus, and is involved in knee flexion and hip extension. It is not the primary muscle responsible for hip abduction.

Subject: Anatomy

System/ Title: Lower Limb

Topic: Muscle Function in Lower Limb

Explanation

(Option D) All of the above: Given that weakness, spasticity, and brisk reflexes are all potential outcomes of an injury to the corticospinal pathway, the correct answer is “All of the above.”

(Option A) Left-sided limb muscle weakness: The corticospinal pathway is responsible for the voluntary control of movements. If there is an injury on the left side at the C2 level, it would affect the descending motor fibers, leading to weakness in the muscles controlled by this pathway on the left side of the body.

(Option B) Left-sided muscle spasticity: Spasticity is a condition characterized by increased muscle tone and exaggerated reflexes. Damage to the corticospinal pathway can disrupt the normal inhibitory signals to the spinal cord, leading to increased muscle tone or spasticity. This is especially relevant when the upper motor neurons are affected, as is the case in corticospinal pathway injuries.

(Option C) Brisk reflexes on the left side: The corticospinal pathway plays a crucial role in modulating reflexes. When this pathway is injured, there is a lack of inhibitory control, resulting in brisk or exaggerated reflexes on the affected side. Therefore, brisk reflexes on the left side would be expected in this case.

(Option E) None of the above: This option is not correct in the context of an injury to the corticospinal pathway. Such an injury would likely result in neurological changes, as described in options A, B, and C.

Subject: Anatomy

System/ Title: Neuroanatomy

Topic: Corticospinal Pathway Injury at C2 Level