Systemic Anatomy — MCQs
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Food particles mostly get obstructed in which part of the esophagus?
Which of the following is the primary mechanical action of the tensor tympani muscle?
Which of the following is not a part of the uveal tract?
The squamo-columnar junction is normally located at
Cremasteric muscle is formed from ?
Left recurrent laryngeal nerve passes between ?
To which segment of the liver is the gallbladder related?
Which of the following is a permanent mucosal fold?
Which respiratory structure is most distal to the primary bifurcation and participates in gas exchange?
Thoracic duct opens into systemic circulation at?
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: 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 193: Which of the following is not a part of the uveal tract?
- A. Iris
- B. Ciliary body
- C. Retina (Correct Answer)
- D. Choroid
Explanation: ***Retina*** - The **retina** is the light-sensitive layer at the back of the eye, responsible for converting light into neural signals. It is part of the **sensory layer** of the eye, distinct from the uveal tract [1]. - While essential for vision, the retina originates from the **neural ectoderm** and is functionally separate from the uvea, which is primarily vascular and pigmented [2]. *Iris* - The **iris** is the colored part of the eye that surrounds the pupil and regulates the amount of light entering the eye. It is the **anterior-most part** of the uveal tract [3]. - It contains pigmented cells and smooth muscle fibers (sphincter and dilator pupillae) that control pupil size. *Ciliary body* - The **ciliary body** is a ring of tissue behind the iris that produces **aqueous humor** and contains the ciliary muscle, which is involved in accommodating the lens [3]. It is the **middle part** of the uveal tract. - It plays a crucial role in maintaining intraocular pressure and focusing vision [3]. *Choroid* - The **choroid** is the vascular layer of the eye, situated between the retina and the sclera, providing oxygen and nourishment to the outer layers of the retina [1]. It is the **posterior part** of the uveal tract. - Its rich blood supply and pigmentation help absorb excess light, preventing reflections within the eye.
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: 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 196: Left recurrent laryngeal nerve passes between ?
- A. Trachea & larynx
- B. Trachea & esophagus (Correct Answer)
- C. Esophagus and bronchi
- D. Esophagus and aorta
Explanation: ***Trachea & esophagus*** - The **left recurrent laryngeal nerve** ascends in the **tracheoesophageal groove**, running between the trachea and the esophagus [1]. - This anatomical position makes it vulnerable to injury during **thyroid surgery** or with esophageal/tracheal masses [1]. *Trachea & larynx* - The recurrent laryngeal nerve ultimately innervates the **intrinsic muscles of the larynx** (except the cricothyroid), but it does not pass between the trachea and the larynx itself. - Its path is more inferior and posterior to the larynx, specifically within the tracheoesophageal groove [1]. *Esophagus and bronchi* - The recurrent laryngeal nerve is not located directly between the **esophagus and bronchi**. - The bronchi are more laterally positioned relative to the esophagus, and the nerve's primary course is along the midline structures. *Esophagus and aorta* - While the **left recurrent laryngeal nerve** loops under the **aortic arch**, it does not course between the esophagus and the aorta for its entire ascent [1]. - Its final ascent is in the tracheoesophageal groove, distinct from the main bulk of the aorta [1].
Question 197: 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 198: 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 199: Which respiratory structure is most distal to the primary bifurcation and participates in gas exchange?
- A. Terminal bronchiole
- B. Primary bronchi
- C. Respiratory bronchiole (Correct Answer)
- D. Secondary bronchi
Explanation: ***Respiratory bronchiole*** - Respiratory bronchioles are part of the **transition zone** in the respiratory tree, characterized by the presence of scattered **alveoli** in their walls [1]. - This anatomical feature allows them to participate in **gas exchange**, unlike more proximal conducting airways [1]. *Primary bronchi* - These are the first and largest airways branching off the trachea, primarily involved in **conduction** and lacking structures for gas exchange [1]. - They are the most proximal structures listed to the primary bifurcation, not the most distal. *Terminal bronchiole* - Terminal bronchioles are the smallest purely **conducting airways** and do not contain alveoli, so they do not participate in gas exchange [1]. - They precede the respiratory bronchioles in the respiratory tree structure [1]. *Secondary bronchi* - Also known as lobar bronchi, these are branches of the primary bronchi that supply specific lung lobes and are part of the **conducting zone** [1]. - They are much more proximal and do not have alveoli for gas exchange.
Question 200: 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.
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