Systemic Anatomy — MCQs

Systemic Anatomy Indian Medical PG Practice Questions and MCQs

Question 191: Food particles mostly get obstructed in which part of the esophagus?

A. Crossing of arch of aorta
B. Cardiac end
C. Cricopharyngeal sphincter (Correct Answer)
D. None of the options

Explanation: ***Correct: Cricopharyngeal sphincter*** - The **cricopharyngeal sphincter** (upper esophageal sphincter at C6 level) is the **most common site** of esophageal food bolus impaction, accounting for approximately **68-70%** of cases - This is the **narrowest part** of the esophagus and represents the first physiological narrowing where poorly chewed food boluses commonly lodge - It is particularly prone to obstruction with **meat boluses** (steakhouse syndrome), bones, and large food particles - The sphincter's tight muscular ring and acute angle make it the primary site for food impaction in otherwise healthy individuals *Incorrect: Crossing of arch of aorta* - The **aortic arch crossing** (at T4-T5 level) is the **second most common** site of food impaction, not the most common - This anatomical constriction occurs due to external compression by the aortic arch and left main bronchus - While important clinically, it accounts for fewer cases than the cricopharyngeal region *Incorrect: Cardiac end* - The **cardiac end** (lower esophageal sphincter at T10-T11 level) is the **third physiological narrowing** and the **least common** site for acute food bolus impaction in healthy individuals - Obstruction here is more commonly associated with pathological conditions like **achalasia**, **strictures**, or **Schatzki rings** rather than simple food impaction [1] - This area is more frequently involved in **reflux-related issues** than acute obstruction *Incorrect: None of the options* - This is incorrect because the esophagus has **three well-defined anatomical narrowings** where food particles characteristically become obstructed, and the correct answer is listed among the options

Question 192: Esophagus is constricted at 4 anatomic locations. Narrowest part of esophagus lies at which of the following constrictions?

A. At the level of the opening in the diaphragm
B. At the crossing of the aortic arch
C. At the crossing of the left main bronchus
D. At the level of the cricopharyngeal constriction (Correct Answer)

Explanation: At the level of the cricopharyngeal constriction - This is the **narrowest point of the entire esophagus** with a diameter of approximately **1.5 cm**. - Located at the **junction of the pharynx and esophagus** (C6 level, ~15 cm from incisors). - Formed by the **cricopharyngeus muscle** acting as the upper esophageal sphincter. - **Clinically significant**: Most common site for **foreign body impaction** and **iatrogenic perforation** during instrumentation. *At the level of the opening in the diaphragm* - This is the **diaphragmatic constriction** at the esophageal hiatus (~40 cm from incisors). - While physiologically important as the lower esophageal sphincter region, it is **not the narrowest** anatomical point. - Acts as an anti-reflux barrier in conjunction with the lower esophageal sphincter. *At the crossing of the aortic arch* - The esophagus passes **posterior to the aortic arch** (~22.5 cm from incisors). - Creates the second anatomical constriction but is **wider than the cricopharyngeal region**. - Can be visualized on barium swallow as an indentation on the esophagus. *At the crossing of the left main bronchus* - The **left main bronchus** crosses anterior to the esophagus (~27 cm from incisors). - This is the third anatomical constriction in the thoracic esophagus. - Also **wider than the upper esophageal constriction**.

Question 193: Which of the following is the primary mechanical action of the tensor tympani muscle?

A. Dampen very loud sound
B. Tenses tympanic membrane (Correct Answer)
C. Tenses pharyngotympanic tube
D. Prevent noise trauma to the inner ear

Explanation: ***Tenses tympanic membrane*** - The **tensor tympani muscle** contracts to pull the **malleus** medially, thereby **tensing the tympanic membrane** [1]. - This action **reduces the amplitude of vibrations** transmitted from the tympanic membrane to the ossicles, protecting the inner ear from loud sounds [1]. *Dampen very loud sound* - While the tensor tympani does play a role in protecting the ear from loud sounds, its primary physiological action is to **tense the tympanic membrane**, which in turn helps dampen sound. - The **stapedius muscle** also contributes significantly to this dampening effect by stabilizing the **stapes** at the oval window [1]. *Tenses pharyngotympanic tube* - The **pharyngotympanic (auditory) tube** is opened by the action of the **tensor veli palatini** and **levator veli palatini muscles** during swallowing and yawning, not the tensor tympani [1]. - Tensing the pharyngotympanic tube is not a known physiological function of the tensor tympani. *Prevent noise trauma to the inner ear* - This is an outcome of the tensor tympani's action, but not its direct physiological function. The tensor tympani directly **tenses the tympanic membrane** to achieve this protective effect [1]. - The **acoustic reflex**, involving both tensor tympani and stapedius muscles, serves to prevent damage from loud sounds, but the question asks for the specific function of the muscle.

Question 194: The squamo-columnar junction is normally located at

A. In esophagus more than 3cms proximal to GEJ
B. Proximal 2-3 cms of stomach
C. Distal 2-3 cms of esophagus (Correct Answer)
D. None of the options

Explanation: ***Distal 2-3 cms of esophagus*** - The **squamo-columnar junction** (SCJ), or Z-line, is the visible endoscopic landmark where the pale, shiny stratified squamous epithelium of the esophagus meets the red, velvety columnar epithelium of the stomach. - In normal anatomy, this junction is typically located within the **distal 2-3 cm** of the esophagus, just above the anatomical gastroesophageal junction (GEJ). *Proximal 2-3 cms of stomach* - This location would imply the SCJ is in the stomach, which is incorrect; the stomach lining is entirely composed of **columnar epithelium**. - While there is a transition at the gastroesophageal junction, the term squamo-columnar junction specifically refers to the meeting point of esophageal squamous and gastric-type columnar epithelia. *In esophagus more than 3cms proximal to GEJ* - If the SCJ is located more than 3 cm proximal to the GEJ, it suggests **Barrett's esophagus**, where gastric-type columnar epithelium has replaced the normal esophageal squamous lining due to metaplasia [1]. - This is an abnormal finding and not the physiological location of the squamo-columnar junction. *None of the options* - This option is incorrect because the distal 2-3 cm of the esophagus accurately describes the normal location of the squamo-columnar junction. - The SCJ's position is a critical clinical landmark for identifying conditions like Barrett's esophagus or hiatal hernia [1].

Question 195: Which of the following is a permanent mucosal fold?

A. Heister's valves
B. Plicae circularis (Correct Answer)
C. Transverse rectal fold
D. Gastric rugae

Explanation: ***Plicae circularis*** - Also known as **Valves of Kerckring**, these are large, **permanent folds** of the mucosa and submucosa in the **small intestine** (jejunum and ileum) [2]. - They are **true structural folds** that remain present regardless of the state of intestinal distension. - They increase the surface area for absorption and are a defining histological feature of the small intestine [1], [2]. *Heister's valves* - These are **spiral folds** found within the **cystic duct** of the biliary system. - While they are consistent anatomical features, they are **not classified as permanent mucosal folds** in the strict anatomical sense, as they can vary in prominence and are more functional structures that prevent collapse of the duct. *Transverse rectal fold* - These are **semilunar folds** (also called Houston's valves) that protrude into the lumen of the rectum. - They are **not permanent** and can appear or disappear depending on the state of rectal distension. *Gastric rugae* - These are **temporary folds** in the gastric mucosa that allow for expansion of the stomach when filled with food. - They **flatten out** when the stomach is distended, making them clearly non-permanent structures.

Question 196: Cremasteric muscle is formed from ?

A. Internal oblique muscle (Correct Answer)
B. External oblique muscle
C. Rectus abdominis muscle
D. Transversus abdominis muscle

Explanation: ***Internal oblique muscle*** - The cremasteric muscle is derived from **muscle fibers of the internal oblique muscle** [1] during testicular descent through the inguinal canal. - The **cremasteric fascia** is derived from the fascia and aponeurosis of the internal oblique muscle [1]. - This muscle allows for the **cremasteric reflex**, which elevates the testis in response to cold or tactile stimulation for temperature regulation and protection. *External oblique muscle* - The **external oblique muscle** contributes the **external spermatic fascia**, which is the most superficial layer covering the spermatic cord. - It does not contribute to the formation of the cremasteric muscle itself. *Rectus abdominis muscle* - The **rectus abdominis muscle** is located medially in the anterior abdominal wall and does not contribute to the formation of the cremasteric muscle or any spermatic cord coverings. - Its primary function is trunk flexion and compression of abdominal contents. *Transversus abdominis muscle* - The **transversus abdominis muscle** and its fascia contribute to the **internal spermatic fascia**, which is the deepest layer of the spermatic cord coverings [1]. - It does not form the cremasteric muscle.

Question 197: Thoracic duct opens into systemic circulation at?

A. junction of SVC and left brachiocephalic vein
B. junction of left internal jugular and left subclavian vein (Correct Answer)
C. Directly into coronary sinus
D. Into azygos vein

Explanation: ***junction of left internal jugular and left subclavian vein*** - The **thoracic duct** is the largest lymphatic vessel in the body and collects lymph from most of the body [1]. - It empties into the venous system at the **venous angle**, which is formed by the union of the **left internal jugular vein** and the **left subclavian vein** [1]. *junction of SVC and left brachiocephalic vein* - The **superior vena cava (SVC)** receives deoxygenated blood from the upper half of the body but is not the direct site for thoracic duct drainage. - The **left brachiocephalic vein** is formed by the union of the left internal jugular and left subclavian veins, but the duct enters before this complete union. *Directly into coronary sinus* - The **coronary sinus** is part of the venous system of the heart and primarily drains deoxygenated blood from the myocardial capillaries into the right atrium. - It has no role in the drainage of general body lymph via the thoracic duct. *Into azygos vein* - The **azygos vein** is a major vein in the posterior mediastinum that drains blood from the posterior walls of the thorax and abdomen. - While it is located near the thoracic duct, the duct does not directly empty into the azygos vein.

Question 198: Which of the following are cusps of the aortic valve?

A. Left, Right, and Posterior
B. Non-coronary, Right, and Anterior
C. Non-coronary, Left, and Right (Correct Answer)
D. Anterior, Non-coronary, and Left

Explanation: ***Non-coronary, Left, and Right*** - The aortic valve is a **semilunar valve** with three leaflets, or cusps, that prevent backflow of blood into the left ventricle during diastole. [1] - These cusps are officially designated as the **non-coronary (posterior)**, **left coronary**, and **right coronary cusps**, based on the presence or absence of a coronary artery ostium originating from the respective sinus. [1] *Left, Right, and Posterior* - While "left" and "right" correctly identify two cusps, "posterior" is a less common and slightly ambiguous term for the third cusp. - The more precise anatomical term for the cusp that does not give rise to a coronary artery is **non-coronary cusp**. *Non-coronary, Right, and Anterior* - "Non-coronary" and "right" are correct designations. - However, "anterior" is not a recognized or anatomically accurate name for any of the aortic valve cusps. *Anterior, Non-coronary, and Left* - "Non-coronary" and "left" are correct designations. - Similar to the previous option, "anterior" is an incorrect and non-standard term for an aortic valve cusp.

Question 199: To which segment of the liver is the gallbladder related?

A. Segment I
B. Segment II
C. Segment III
D. Segment IV (Correct Answer)

Explanation: ***Segment IV*** - The **gallbladder** is anatomically positioned in the **fossa of the gallbladder**, which lies in relation to the **quadrate lobe** of the liver [1]. - The **quadrate lobe** corresponds to **Segment IV** of the Couinaud classification system [1]. *Segment I* - **Segment I** is the **caudate lobe**, which is located posterior to the porta hepatis and is functionally distinct, receiving blood supply from both the right and left hepatic arteries [2]. - It is superior to the gallbladder and not directly related to its fossa [1]. *Segment II* - **Segment II** is located in the **left lateral segment** of the liver, superior and to the left of the falciform ligament [3]. - This segment is far from the anatomical position of the gallbladder. *Segment III* - **Segment III** is also part of the **left lateral segment**, situated anteroinferiorly to Segment II [3]. - Like Segment II, it is anatomically distant from the gallbladder fossa.

Question 200: Where does the great cardiac vein lie?

A. Tricuspid valve
B. Anterior interventricular sulcus (Correct Answer)
C. Posterior interventricular sulcus
D. Coronary sulcus

Explanation: ***Anterior interventricular sulcus*** - The **great cardiac vein** runs alongside the **left anterior descending artery** (LAD) within the **anterior interventricular sulcus**. - This anatomical position allows it to drain the areas supplied by the LAD, primarily the **anterior walls** of both ventricles and the interventricular septum. - From the apex, it ascends in this sulcus before continuing around the left border of the heart. *Tricuspid valve* - The **tricuspid valve** is located between the **right atrium** and **right ventricle** and is involved in blood flow regulation, not venous drainage. - This is a valvular structure, not a sulcus or groove where vessels lie. *Posterior interventricular sulcus* - The **posterior interventricular sulcus** houses the **middle cardiac vein** and the **posterior interventricular artery**. - The great cardiac vein is not found in this sulcus; it drains the anterior aspect of the heart. *Coronary sulcus* - The **coronary sulcus** (atrioventricular groove) contains the **coronary sinus** and circumflex vessels. - While the great cardiac vein eventually continues as the coronary sinus in this region, the vein itself specifically lies in the anterior interventricular sulcus during its ascending course.

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