Systemic Anatomy — MCQs

Systemic Anatomy Indian Medical PG Practice Questions and MCQs

Question 271: Which artery supplies the anterior part of the interventricular septum?

A. Right coronary artery
B. Posterior descending coronary artery
C. Left anterior descending artery (LAD) (Correct Answer)
D. None of the options

Explanation: ***Left anterior descending artery (LAD)*** - The **LAD** is a branch of the **left main coronary artery** and is also known as the "widowmaker" due to its critical supply to a large portion of the left ventricle and the interventricular septum [1]. - It gives rise to **septal branches** that typically supply the anterior two-thirds of the interventricular septum [1]. *Right coronary artery* - The **right coronary artery (RCA)** primarily supplies the **right ventricle**, the right atrium, the SA node (in 60% of people), and the AV node (in 90% of people). - It typically supplies the **inferior wall** of the left ventricle and the posterior one-third of the interventricular septum [1]. *Posterior descending coronary artery* - The **posterior descending artery (PDA)** arises from the **RCA** (in approximately 85% of individuals, known as right dominance) or less commonly from the circumflex artery (in left dominance) [1]. - It supplies the **posterior one-third** of the interventricular septum and typically the inferior wall of the left ventricle [1]. *None of the options* - This option is incorrect because the **LAD** clearly and predominantly supplies the anterior part of the interventricular septum.

Question 272: Which of the following is not a posterior relation of the right kidney?

A. Subcostal nerve
B. Diaphragm
C. 11th rib (Correct Answer)
D. Ilioinguinal nerve

Explanation: ***11th rib*** - The right kidney typically extends from the 12th thoracic vertebra to the 3rd lumbar vertebra, usually covered by the **12th rib**. - The **11th rib** is usually a posterior relation of the **left kidney**, due to the lower position of the right kidney compared to the left kidney. *Diaphragm* - The diaphragm lies **posterior** to both the right and left kidneys, separating them from the pleura and lungs. - This anatomical relationship means that renal procedures or severe kidney infections can sometimes affect the thoracic cavity. *Subcostal nerve* - The **subcostal nerve** (T12) runs inferior to the 12th rib and passes **posterior** to both kidneys. - It provides sensory innervation to the skin and motor innervation to abdominal muscles. *Ilioinguinal nerve* - The **ilioinguinal nerve** (L1) emerges from the lumbar plexus and travels **posterior** to the inferior pole of both kidneys [1]. - It primarily provides sensory innervation to the groin and parts of the external genitalia.

Question 273: Base of the heart is formed by?

A. Right atrium
B. Right ventricle
C. Left atrium (Correct Answer)
D. Left ventricle

Explanation: ***Left atrium*** - The **left atrium** forms the major part of the **base of the heart**, receiving the four pulmonary veins. [1] - It lies in the posterior-superior aspect of the heart and is separated from the thoracic vertebrae by the **pericardium** and the **esophagus**. *Right atrium* - The **right atrium** forms the right border of the heart and receives deoxygenated blood from the **superior and inferior vena cava**. - It primarily forms part of the **anterior surface** of the heart, not the base. *Right ventricle* - The **right ventricle** forms a large part of the **anterior surface** and inferior border of the heart. - It is responsible for pumping blood to the **pulmonary circulation** but does not form the base. *Left ventricle* - The **left ventricle** forms the **apex** of the heart and much of its **left border** and **diaphragmatic surface**. - Its primary role is to pump oxygenated blood into the **systemic circulation**.

Question 274: Uvula vesicae seen in bladder is formed from the following structure?

A. Lateral lobe of the prostate
B. Anterior lobe of the prostate
C. Posterior lobe of the prostate
D. Median lobe of the prostate (Correct Answer)

Explanation: ***Median lobe of the prostate*** - The **uvula vesicae** is a slight median elevation on the internal surface of the **bladder base**, immediately behind the **internal urethral orifice**. - This elevation is formed by the underlying **median (middle) lobe of the prostate** projecting upward beneath the bladder mucosa. - In **benign prostatic hyperplasia (BPH)**, enlargement of the median lobe accentuates this prominence and can cause significant urinary obstruction. *Lateral lobe of the prostate* - Enlargement of the **lateral lobes** causes lateral compression of the prostatic urethra, not a median elevation at the bladder neck. - While they are the most common site of **BPH**, they do not form the uvula vesicae. *Anterior lobe of the prostate* - The **anterior lobe** (or anterior fibromuscular stroma) is located in front of the urethra and is non-glandular. - It does not contribute to the formation of the uvula vesicae or cause significant urinary symptoms. *Posterior lobe of the prostate* - The **posterior lobe** is located behind the urethra and is the most common site for **prostate cancer**. - It does not project into the bladder base and therefore does not form the uvula vesicae.

Question 275: What is the nerve supply of the cremasteric muscle?

A. Pudendal nerve
B. Femoral branch of genitofemoral
C. Genital branch of genitofemoral nerve (Correct Answer)
D. Ilioinguinal nerve

Explanation: ***Genital branch of genitofemoral nerve*** - The **genital branch of the genitofemoral nerve** (L1-L2) directly innervates the cremaster muscle, controlling its contraction. - This nerve provides the **efferent (motor) limb** of the **cremasteric reflex**, causing elevation of the testis when the inner thigh is stroked. - The afferent (sensory) limb of this reflex is carried by the ilioinguinal nerve or femoral branch of the genitofemoral nerve. *Pudendal nerve* - The **pudendal nerve** (S2-S4) primarily innervates the perineum and external genitalia, responsible for sensation and motor function of the pelvic floor and sphincters. - It does not supply the cremaster muscle. *Femoral branch of genitofemoral* - The **femoral branch of the genitofemoral nerve** supplies sensation to the skin of the upper anterior thigh. - It provides sensory input (afferent limb) for the cremasteric reflex but does not have motor innervation to the cremaster muscle. *Ilioinguinal nerve* - The **ilioinguinal nerve** (L1) provides sensory innervation to the skin of the upper medial thigh, root of the penis/mons pubis, and parts of the scrotum/labia majora. - While it traverses the inguinal canal and may contribute to the afferent limb of the cremasteric reflex, it does not innervate the cremaster muscle itself.

Question 276: Where is Schatzki's Ring present?

A. Upper end of trachea
B. Lower end of esophagus (Correct Answer)
C. Upper end of esophagus
D. Lower end of trachea

Explanation: ***Lower end of esophagus*** - **Schatzki's Ring** is a localized narrowing that can occur at the **gastroesophageal junction**, specifically at the squamocolumnar junction. - This ring is a common cause of intermittent **dysphagia** for solid foods. [2] *Upper end of trachea* - The upper end of the trachea is the **larynx** or a region just below it, which is anatomically distinct from the esophagus. - Constrictions in this area are generally unrelated to Schatzki's Ring and typically involve conditions like **subglottic stenosis**. *Upper end of esophagus* - The upper end of the esophagus contains the **upper esophageal sphincter** (UES), which is a muscular structure. [3] - While strictures can occur here, they are not referred to as Schatzki's Ring. *Lower end of trachea* - The lower end of the trachea **bifurcates into the bronchi** and is part of the respiratory system. [1] - Anatomically, it is separate from the esophagus, and issues here would be related to respiratory conditions, not Schatzki's Ring.

Question 277: Which of the following arteries does NOT contribute to Little's area?

A. Sphenopalatine artery
B. Posterior Ethmoidal artery (Correct Answer)
C. Greater palatine artery
D. Anterior Ethmoidal artery

Explanation: Posterior Ethmoidal artery - The posterior ethmoidal artery primarily supplies the posterior ethmoidal cells and part of the sphenoid sinus, but it does not contribute to the vascular plexus in Little's area. - Little's area, also known as Kiesselbach's plexus, is formed by anastomoses of several arteries on the anterior nasal septum. Sphenopalatine artery - The sphenopalatine artery, a terminal branch of the maxillary artery, is a major contributor to Little's area through its septal branch. - It supplies a significant portion of the nasal septum and is frequently involved in posterior epistaxis. Greater palatine artery - The greater palatine artery, a branch of the descending palatine artery (from the maxillary artery), enters the nasal cavity through the incisive canal and contributes to Little's area on the nasal septum. - It primarily supplies the hard palate and then anastomoses with other vessels in the anterior nasal septum. Anterior Ethmoidal artery - The anterior ethmoidal artery, a branch of the ophthalmic artery, is a key contributor to Little's area. - It supplies the anterior and middle ethmoidal cells and also contributes to the blood supply of the dura mater.

Question 278: Which of the following statements is true regarding the anatomy of the external nose?

A. The lower one-third is primarily cartilaginous. (Correct Answer)
B. The upper two-thirds is entirely bony.
C. The lateral aspect has only a single cartilage.
D. The external nose is supported by two nasal bones.

Explanation: ***The lower one-third is primarily cartilaginous.*** - The **lower one-third** of the external nose, including the nasal tip and alae, is predominantly supported by **alar cartilages** (lower lateral cartilages) and other minor cartilages, giving it flexibility. - This cartilaginous structure allows for movement and shaping of the nostrils. - This statement is **anatomically accurate and complete**. *The upper two-thirds is entirely bony.* - This is **incorrect**. - The **upper one-third** is bony (nasal bones and frontal process of maxilla). - The **middle one-third** is primarily **cartilaginous** (upper lateral cartilages). - Therefore, the upper two-thirds consists of **both bone and cartilage**, not entirely bone. *The lateral aspect has only a single cartilage.* - This is **incorrect**. - The lateral aspect contains **multiple cartilages**: upper lateral cartilages, lower lateral (alar) cartilages, and accessory cartilages. - The presence of multiple cartilages provides structural support and flexibility. *The external nose is supported by two nasal bones.* - This is **incomplete and misleading**. - While two **nasal bones** do form the superior bony bridge (upper one-third), the external nose is also supported by: - Frontal process of the maxilla - Upper and lower lateral cartilages - Septal cartilage - Stating only the nasal bones ignores the majority of nasal support structures.

Question 279: All are parts of anterior segment of eye except?

A. Lens
B. Cornea
C. Aqueous humor
D. Vitreous (Correct Answer)

Explanation: ***Vitreous*** - The **vitreous humor**, or simply vitreous, is a transparent, gel-like substance that fills the space posterior to the lens and anterior to the retina, making it part of the **posterior segment** of the eye [3]. - Its main function is to maintain the shape of the eye and keep the retina in place. *Lens* - The **lens** is a transparent, biconvex structure located behind the iris and in front of the vitreous, making it a key component of the **anterior segment** [2]. - It works to focus light onto the retina, changing shape to alter the focal length of the eye. *Cornea* - The **cornea** is the transparent, outermost layer of the eye that covers the iris, pupil, and anterior chamber, clearly positioning it within the **anterior segment** [2]. - It plays a crucial role in focusing light into the eye. *Aqueous humor* - The **aqueous humor** is a clear, watery fluid located in the space between the cornea and the lens (the anterior and posterior chambers), which is definitively part of the **anterior segment** [1]. - It nourishes the cornea and lens and maintains intraocular pressure.

Question 280: What is the thinnest portion of the sclera?

A. Anterior to the rectus muscle insertion
B. At the posterior pole
C. At the limbus
D. Posterior to the rectus muscle insertion (Correct Answer)

Explanation: ***Posterior to the rectus muscle insertion*** - The sclera is thinnest immediately **posterior to the insertion of the rectus muscles**, where it is about 0.3 mm thick. - This area is clinically relevant as it is a common site for globe rupture during trauma. *Anterior to the rectus muscle insertion* - The sclera is relatively thick in this region, measuring around **0.6 mm thick**. - It provides robust support and attachment for the rectus muscles. *At the posterior pole* - At the posterior pole, the sclera is the **thickest**, reaching about 1.0 mm, especially around the optic nerve. - This thickness is necessary to protect the delicate neural structures exiting the eye. *At the limbus* - The sclera-corneal junction, or **limbus**, has an intermediate thickness, around **0.8 mm**. - This area is critical for surgical procedures but is not the thinnest point.

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