NEET-PG 2015 - Anatomy Practice Questions

Q: Azygos vein drains into:

Superior vena cava. ***Superior vena cava*** - The **azygos vein** is a major venous channel that drains the walls of the thorax and abdomen, emptying directly into the **superior vena cava (SVC)**. [1] - This connection is crucial for venous return from the posterior thoracic wall, pericardium, and bronchi, especially bypassing the inferior vena cava if it's obstructed. [1] *Right subcostal vein* - The right subcostal vein is a tributary that helps form the **azygos vein**; it does not receive drainage from the azygos vein. - It contributes to the initial formation of the azygos system, not its termination. *Brachiocephalic* - The **brachiocephalic veins** are formed by the union of the internal jugular and subclavian veins, and they merge to form the **superior vena cava**. - The azygos vein drains into the superior vena cava, not directly into the brachiocephalic veins. *Right ascending lumbar vein* - The **right ascending lumbar vein** is a major tributary that contributes to the formation of the **azygos vein** in the lumbar region. - It drains into the azygos system, illustrating its origin rather than its termination.

Q: The structure which lies outside the femoral sheath is:

Femoral nerve. ***Femoral nerve*** - The **femoral nerve** lies lateral to the femoral artery and is therefore situated outside the **femoral sheath**, which encloses the femoral artery, femoral vein, and lymphatic vessels [2]. - It originates from the lumbar plexus (L2-L4) and provides motor innervation to the quadriceps femoris and sensory innervation to the anterior thigh and medial leg. *Femoral artery* - The **femoral artery** is a primary content of the **femoral sheath**, occupying the most lateral compartment. - It is a continuation of the external iliac artery and is a major blood supply to the lower limb. *Femoral vein* - The **femoral vein** lies within the **femoral sheath**, positioned medial to the femoral artery. - It is the primary vein responsible for draining blood from the lower limb and eventually becomes the external iliac vein. *Genitofemoral nerve* - The **genitofemoral nerve** typically emerges on the anterior surface of the psoas major muscle and then usually divides into genital and femoral branches [1]. - While its femoral branch supplies sensory innervation to the skin over the femoral triangle, it does not course within the femoral sheath itself but rather anterior to it or outside its immediate vicinity [1].

Q: What is the medial boundary of the cubital fossa?

Pronator teres. ***Pronator teres*** - The **pronator teres muscle** forms the **medial boundary** of the cubital fossa, running obliquely from the medial epicondyle to the lateral side of the radius. - This muscle defines the medial aspect of the triangular space at the anterior elbow. *Brachioradialis* - The **brachioradialis** muscle forms the **lateral boundary** of the cubital fossa. - It arises from the humerus and inserts into the distal radius, helping to delineate the region laterally. *Supinator* - The **supinator muscle** is located deep within the forearm and is not a direct boundary of the cubital fossa. - It lies on the posterior aspect of the radius and ulna, deep to some of the cubital fossa contents. *None of the options* - This option is incorrect because the **pronator teres** clearly defines the medial boundary of the cubital fossa.

Q: Which intrinsic ocular muscle responsible for pupillary constriction is supplied by parasympathetic innervation?

Constrictor pupillae. ***Constrictor pupillae*** - The **constrictor pupillae** (or **sphincter pupillae**) muscle is responsible for **miosis** (pupil constriction) and is innervated by **parasympathetic fibers** from the **oculomotor nerve (CN III)** via the **ciliary ganglion** [1]. - Stimulation of this muscle reduces the pupil size, which is a key part of the **light reflex** and **accommodation reflex** [1]. - This is the **only pupillary muscle** with parasympathetic innervation. *Ciliary muscle* - The **ciliary muscle** is involved in **accommodation**, altering the shape of the lens for focusing on near objects [1]. - While it also receives **parasympathetic innervation** from the ciliary ganglion, it does **not control pupil size**. - Its function is to change **lens curvature**, not pupillary diameter. *Levator palpebrae superioris* - This muscle is responsible for **elevating the upper eyelid**. - It is innervated by the **somatic motor fibers** of the **oculomotor nerve (CN III)**, not parasympathetic fibers. - It is **not an intrinsic ocular muscle** but rather an extraocular muscle. *Dilator pupillae* - The **dilator pupillae** muscle causes **mydriasis** (pupil dilation). - This muscle is innervated by **sympathetic fibers**, originating from the superior cervical ganglion, not parasympathetic fibers.

Q: Spleniculi are most commonly found in which of the following locations?

Hilum of the spleen. No relevant citations could be added to the explanation as the provided text passages did not contain information regarding spleniculi (accessory spleens), their location, or their embryology. ***Hilum of the spleen*** - **Spleniculi** (accessory spleens) are most commonly found at the **hilum of the spleen**, accounting for approximately **75% of cases**. - During **embryonic development**, the spleen forms from mesenchymal tissue in the dorsal mesogastrium, and small fragments of splenic tissue can separate and persist as accessory spleens. - The **splenic hilum** is the most frequent location due to the close proximity during development, followed by the gastrosplenic ligament, tail of pancreas, and greater omentum. - Accessory spleens are found in **10-30% of the population** and are clinically significant in conditions requiring complete splenectomy (e.g., ITP, hereditary spherocytosis). *Colon* - The colon is part of the **gastrointestinal tract** with a completely different embryological origin (endodermal). - Splenic tissue development occurs in the **dorsal mesogastrium** (mesodermal origin), making the colon an anatomically and embryologically implausible location for spleniculi. *Liver* - The liver develops from the **ventral foregut endoderm** and is anatomically distant from the spleen's developmental region. - **Splenosis** (traumatic implantation) could theoretically occur, but congenital spleniculi in the liver are exceptionally rare and not a recognized common location. *Lungs* - The lungs are part of the **respiratory system**, developing from the foregut endoderm in the thoracic cavity. - There is no embryological connection between lung and splenic tissue development, making this an impossible location for congenital accessory spleens.

Q: Which of the following is not a derivative of foregut?

Cecum. ***Cecum*** - The **cecum** and the entire large intestine (except the distal third of the transverse colon) are derivatives of the **midgut** [1]. - The midgut is supplied by the **superior mesenteric artery**, differentiating it developmentally from the foregut. *First part of the duodenum* - The **first part of the duodenum** (from the pylorus to the major duodenal papilla) is derived from the **foregut**. - This section receives its blood supply from branches of the **celiac trunk**, consistent with its foregut origin. *Liver* - The **liver** develops as a budding from the distal foregut and is therefore a **foregut derivative** [2]. - It plays a crucial role in metabolism and detoxification, consistent with its early development from this segment. *Pancreas* - The **pancreas** develops from dorsal and ventral buds of the distal foregut, making it a **foregut derivative**. - Both its exocrine and endocrine functions are vital for digestion and glucose homeostasis.

Q: Blood testis barrier in testis is formed by?

Sertoli cells. ***Sertoli cells*** - **Sertoli cells** form tight junctions with each other, creating the **blood-testis barrier** [1] - This barrier divides the seminiferous epithelium into **basal and adluminal compartments** [1] - Essential for protecting developing **germ cells** from immune attack and maintaining a specialized microenvironment for **spermatogenesis** [1] - The tight junctions between Sertoli cells are among the tightest in the human body *Granulosa cells* - **Granulosa cells** are found in the **ovary**, not the testis - They surround the oocyte in ovarian follicles and produce **estrogen** - Completely unrelated to testicular structure or function *Germ cells* - **Germ cells** (spermatogonia, spermatocytes, spermatids, spermatozoa) are the developing sperm cells [1] - They are **protected by** the blood-testis barrier, not forming it [1] - Located within the seminiferous tubules but do not create barrier structures [1] *Leydig cells* - **Leydig cells** are interstitial cells located in the connective tissue **between seminiferous tubules** - Their primary function is production of **testosterone**, not forming barriers [2] - They are outside the seminiferous tubules and not involved in barrier formation [2]

Q: In the context of blood pressure regulation, where are baroreceptors primarily located?

Tunica adventitia. ***Tunica adventitia*** - **Baroreceptors** are specialized mechanoreceptive nerve endings that detect changes in blood pressure by sensing arterial wall stretch. - These sensory nerve endings are primarily located in the **tunica adventitia** (outermost layer) of the **carotid sinus** and **aortic arch** [1]. - The adventitia contains the **nerve fibers and endings** (including baroreceptors), as well as the vasa vasorum and connective tissue supporting the vessel wall [1]. - The nerve terminals extend from the adventitia toward the adventitial-medial border where they sense wall tension changes. *Tunica media* - The **tunica media** is the middle layer composed of **smooth muscle cells** and elastic fibers. - While this layer responds to stretch and changes thickness with blood pressure variations, it does **not contain nerve endings or baroreceptors** [1]. - The media is responsible for vasoconstriction and vasodilation but lacks the sensory innervation needed for baroreception. *Tunica intima* - The **tunica intima** is the innermost layer lined by **endothelial cells**. - Its primary functions include providing a smooth surface for blood flow and regulating vascular permeability. - This layer does not house baroreceptors or other mechanoreceptive nerve endings. *None of the options* - This option is incorrect because **tunica adventitia** is indeed the correct location of baroreceptors. - The adventitia contains the neural elements necessary for blood pressure sensing in these specialized arterial regions [1].

Q: Which type of glial cell is derived from mesodermal origin?

Microglial cells. ***Microglial cells*** - **Microglial cells** are unique among glial cells as they originate from **mesoderm**, specifically from **monocyte/macrophage precursors** in the bone marrow [1]. - They function as the **immune cells of the central nervous system (CNS)**, scavenging for plaques, damaged neurons, and infectious agents [1]. *Macroglial cells* - This is a broad category that includes **astrocytes, oligodendrocytes, and ependymal cells**, all of which are derived from **neuroectoderm**, not mesoderm [1]. - They perform various supportive roles but are distinct in origin from microglial cells [1]. *Oligodendrocytes* - **Oligodendrocytes** are derived from **neuroectoderm** and are responsible for forming the **myelin sheath** around axons in the CNS [2]. - Myelination is crucial for rapid and efficient nerve impulse conduction. *Ependymal cells* - **Ependymal cells** are derived from **neuroectoderm** and line the **ventricles of the brain** and the **central canal of the spinal cord**. - They play a role in the production and circulation of **cerebrospinal fluid (CSF)**.

Q: Trigone of bladder is derived from?

Mesonephric duct. The trigone of the bladder is formed from the caudal ends of the **mesonephric ducts**, which are absorbed into the primitive bladder wall [1]. This mesenchymal origin explains why the trigone has a smooth lining [1] and is less prone to infection compared to the rest of the bladder. *Paramesonephric duct* - The **paramesonephric ducts** (Müllerian ducts) are involved in forming the female reproductive organs, specifically the fallopian tubes, uterus [2], and upper vagina. - They do not contribute to the formation of the urinary bladder or its trigone. *Absorbed anal membrane* - The **anal membrane** separates the endoderm-derived hindgut from the ectoderm-derived anal pit. - Its absorption is relevant to the development of the anus, not the urinary bladder. *Mullerian duct* - The **Müllerian ducts** are synonymous with the paramesonephric ducts and are primarily involved in the development of the female reproductive tract [2]. - They play no role in the development of the urinary bladder or its trigone.

Question 1

Azygos vein drains into:

Accepted Answer

Superior vena cava

Answer

Right subcostal vein

Answer

Right ascending lumbar vein

Answer

Brachiocephalic

Question 2

The structure which lies outside the femoral sheath is:

Accepted Answer

Femoral nerve

Answer

Genitofemoral nerve

Answer

Femoral vein

Answer

Femoral artery

Question 3

What is the medial boundary of the cubital fossa?

Accepted Answer

Pronator teres

Answer

Brachioradialis

Answer

Supinator

Answer

None of the options

Question 4

Which intrinsic ocular muscle responsible for pupillary constriction is supplied by parasympathetic innervation?

Accepted Answer

Constrictor pupillae

Answer

Dilator pupillae

Answer

Levator palpebrae superioris

Answer

Ciliary muscle

Question 5

Spleniculi are most commonly found in which of the following locations?

Accepted Answer

Hilum of the spleen

Answer

Colon

Answer

Liver

Answer

Lungs

Question 6

Which of the following is not a derivative of foregut?

Accepted Answer

Cecum

Answer

Liver

Answer

Pancreas

Answer

First part of the duodenum

Question 7

Blood testis barrier in testis is formed by?

Accepted Answer

Sertoli cells

Answer

Germ cells

Answer

Leydig cells

Answer

Granulosa cells

Question 8

In the context of blood pressure regulation, where are baroreceptors primarily located?

Accepted Answer

Tunica adventitia

Answer

Tunica intima

Answer

None of the options

Answer

Tunica media

Question 9

Which type of glial cell is derived from mesodermal origin?

Accepted Answer

Microglial cells

Answer

Macroglial cells

Answer

Oligodendrocytes

Answer

Ependymal cells

Question 10

Trigone of bladder is derived from?

Accepted Answer

Mesonephric duct

Answer

Paramesonephric duct

Answer

Absorbed anal membrane

Answer

Mullerian duct

NEET-PG 2015 — Anatomy