Anatomy
8 questionsThe internal anal sphincter is a part of which of the following?
Which artery passes through the anatomical snuffbox?
Heart tube is formed in a gelatinous matrix rich in:
What is the remnant of the umbilical artery?
Which of the following is a derivative of paramesonephric duct in males ?
Common hepatic artery is a branch of:
Prolactin secreting gland develops from -
What is the posterior relation of the neck of the pancreas?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 151: The internal anal sphincter is a part of which of the following?
- A. Puborectalis muscle
- B. Deep perineal muscles
- C. Internal longitudinal fibers
- D. Internal circular fibers (Correct Answer)
Explanation: ***Internal circular fibers*** - The **internal anal sphincter** is an involuntary muscle formed by the thickening of the **circular smooth muscle layer** of the rectum. - This sphincter maintains **tonic contraction** and is responsible for about 80% of resting anal pressure [1]. *Puborectalis muscle* - The **puborectalis muscle** is a voluntary muscle, forming a sling around the anorectal junction to maintain the **anorectal angle** [1]. - It is part of the **levator ani muscles**, which are skeletal muscles, not smooth muscle [1]. *Deep perineal muscles* - The **deep perineal muscles** are a group of skeletal muscles located in the urogenital diaphragm. - They are involved in functions such as **urinary continence** and **erection**, but do not form the internal anal sphincter. *Internal longitudinal fibers* - The **longitudinal muscle layer** of the rectum continues downwards as the conjoined longitudinal muscle, which blends with the external anal sphincter. - These fibers contribute to the **anorectal ring** and support the anal canal but do not form the internal anal sphincter itself.
Question 152: Which artery passes through the anatomical snuffbox?
- A. Radial artery (Correct Answer)
- B. Brachial artery
- C. Ulnar artery
- D. Interosseus artery
Explanation: ***Radial artery*** - The **radial artery** is palpable within the **anatomical snuffbox**, as it courses over the scaphoid and trapezium bones towards the deep palmar arch. - This location is clinically significant for feeling the pulse and is vulnerable to injury, especially during **scaphoid fractures**. *Brachial artery* - The **brachial artery** is found in the **arm**, typically running in the cubital fossa, well proximal to the anatomical snuffbox. - It bifurcates into the radial and ulnar arteries at the level of the elbow, not within the wrist structures. *Ulnar artery* - The **ulnar artery** typically lies on the **medial side of the forearm** and wrist, contributing to the superficial palmar arch. - It does not pass through the anatomical snuffbox, which is located on the lateral aspect of the wrist. *Interosseus artery* - The **interosseus arteries** (anterior and posterior) run between the radius and ulna in the forearm, supplying muscles and bones. - These arteries are deep within the forearm compartments and do not traverse the superficial anatomical snuffbox at the wrist.
Question 153: Heart tube is formed in a gelatinous matrix rich in:
- A. Hyaluronic acid secreted by the endocardium
- B. Chondroitin sulfate secreted by the endocardium
- C. Hyaluronic acid secreted by the myocardium (Correct Answer)
- D. Chondroitin sulfate secreted by the myocardium
Explanation: ***Hyaluronic acid secreted by the myocardium*** - The developing **heart tube** forms within a gelatinous extracellular matrix that is rich in **hyaluronic acid**. - This **hyaluronic acid** is secreted by the **myocardium** (the developing heart muscle), which plays a crucial role in the initial formation and remodeling of the heart. *Hyaluronic acid secreted by the endocardium* - While the endocardium is an important layer of the heart, it is the **myocardium** that primarily secretes the **hyaluronic acid** critical for heart tube formation during early development. - The **endocardium** forms the inner lining and primarily acts in blood-tissue interaction and valvular development later on. *Chondroitin sulfate secreted by the endocardium* - **Chondroitin sulfate** is a component of the extracellular matrix, but it is not the primary proteoglycan responsible for the initial formation environment of the heart tube. - Furthermore, its secretion is not predominantly from the **endocardium** in this context. *Chondroitin sulfate secreted by the myocardium* - Although the myocardium is responsible for secreting extracellular matrix components, **chondroitin sulfate** is not the predominant or critical molecule responsible for the initial gelatinous matrix allowing heart tube formation. - **Hyaluronic acid** plays this key role in early cardiogenesis.
Question 154: What is the remnant of the umbilical artery?
- A. Ligamentum arteriosum
- B. Ligament teres
- C. Ligamentum venosum
- D. Medial umbilical ligament (Correct Answer)
Explanation: ***Medial umbilical ligament*** - The **umbilical arteries** (paired structures) carry deoxygenated blood from the fetus to the placenta during development [2]. - After birth, these arteries obliterate and persist as the **medial umbilical ligaments** (two in number, one on each side), extending from the internal iliac arteries to the umbilicus along the anterior abdominal wall. - The proximal portions of the umbilical arteries remain patent as the **superior vesical arteries**, which supply the bladder. *Ligamentum arteriosum* - This is the remnant of the **ductus arteriosus**, which shunted blood from the pulmonary artery to the aorta, bypassing the fetal lungs [2]. - It connects the arch of the aorta to the pulmonary artery. *Ligament teres* - Also known as the **round ligament of the liver**, this is the remnant of the **fetal umbilical vein** (a single midline structure) [1]. - The umbilical vein carried oxygenated blood from the placenta to the fetus [1], [2]. *Ligamentum venosum* - This is the fibrous remnant of the **ductus venosus**, a shunt in fetal circulation that bypassed the liver by connecting the umbilical vein to the inferior vena cava [1]. - It is located deep within the liver, forming a fissure.
Question 155: Which of the following is a derivative of paramesonephric duct in males ?
- A. Trigone of bladder
- B. Paraphoron
- C. Prostatic utricle (Correct Answer)
- D. Gartner's duct
Explanation: ***Prostatic utricle*** - The **prostatic utricle** is a blind-ending pouch located in the prostatic urethra. - It represents a **rudimentary derivative of the paramesonephric (Müllerian) duct** in males, which normally regresses due to the presence of Müllerian-inhibiting substance (MIS). *Trigone of bladder* - The trigone of the bladder is derived from the caudal ends of the **mesonephric ducts** (Wolffian ducts), not the paramesonephric ducts. - It forms through the incorporation of these ducts into the posterior wall of the bladder. *Paraphoron* - The **paraphoron** is a vestigial structure found in females, representing remnants of the caudal parts of the **epoophoron tubules**. - These are derived from the **mesonephric tubules**, not the paramesonephric ducts, and are not found in males. *Gartner's duct* - **Gartner's duct** is a remnant of the **mesonephric (Wolffian) duct** in females, typically running along the lateral wall of the vagina or uterus. - It is not found in males and is derived from a different embryonic structure than the paramesonephric duct.
Question 156: Common hepatic artery is a branch of:
- A. Splenic artery
- B. Superior mesenteric artery
- C. Inferior mesenteric artery
- D. Coeliac trunk (Correct Answer)
Explanation: ***Coeliac trunk*** - The **common hepatic artery** is one of the three main branches arising from the **coeliac trunk**, which is the first major anterior branch of the abdominal aorta [1]. - It typically supplies the **liver**, gallbladder, pylorus of the stomach, and part of the duodenum through its various branches [1]. *Splenic artery* - The **splenic artery** is another major branch of the coeliac trunk, primarily supplying the **spleen**, and also gives off branches to the stomach and pancreas [1]. - It does not directly give rise to the common hepatic artery. *Superior mesenteric artery* - The **superior mesenteric artery (SMA)** originates just inferior to the coeliac trunk from the abdominal aorta and supplies structures of the **midgut**, including the small intestine, and parts of the large intestine. - It is not a direct source of the common hepatic artery. *Inferior mesenteric artery* - The **inferior mesenteric artery (IMA)** arises from the abdominal aorta further inferior to the SMA and supplies the **hindgut**, including the distal transverse colon to the superior part of the rectum. - It is anatomically distinct and separate from the arterial supply to the foregut-derived organs supplied by the common hepatic artery.
Question 157: Prolactin secreting gland develops from -
- A. Infundibulum
- B. Rathke's pouch (Correct Answer)
- C. Tuber cinereum
- D. 3rd ventricle
Explanation: ***Rathke's pouch*** - The **anterior pituitary gland**, which secretes prolactin [2], develops embryologically from **Rathke's pouch**. - Rathke's pouch is an **ectodermal evagination** from the roof of the primitive oral cavity (stomodeum). *Infundibulum* - The **infundibulum** is also known as the pituitary stalk, connecting the hypothalamus to the posterior pituitary [1]. - It is derived from **neuroectoderm** and forms part of the posterior pituitary, not the prolactin-secreting anterior pituitary [1]. *Tuber cinereum* - The **tuber cinereum** is a part of the **hypothalamus**. - It is involved in regulating several bodily functions but does not directly give rise to the prolactin-secreting gland. *3rd ventricle* - The **3rd ventricle** is one of the four ventricles of the brain, filled with **cerebrospinal fluid**. - It is a part of the central nervous system and is not involved in the embryological development of the pituitary gland.
Question 158: What is the posterior relation of the neck of the pancreas?
- A. IVC
- B. Aorta
- C. Common bile duct
- D. Origin of portal vein (Correct Answer)
Explanation: ***Origin of portal vein*** - The **neck of the pancreas** is intimately associated with the formation of the **hepatic portal vein** [1]. - The **superior mesenteric vein** and **splenic vein** unite behind the pancreatic neck to form the **hepatic portal vein** [1]. *IVC* - The **inferior vena cava (IVC)** lies posterior to the **head of the pancreas**, not the neck. - While it's in proximity, it does not directly relate to the neck in the same way the portal vein does. *Aorta* - The **abdominal aorta** lies posterior to the **body** and **tail of the pancreas**, further superior and to the left. - It is not a direct posterior relation of the pancreatic neck. *Common bile duct* - The **common bile duct** passes through a groove on the posterior surface of the pancreatic **head**, sometimes even embedded within it. - It is not a direct posterior relation of the pancreatic neck, which is a different segment.
Physiology
2 questionsWhich of the following is not a recognized stage of prophase I in meiosis?
Spermatogenesis begins at -
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 151: Which of the following is not a recognized stage of prophase I in meiosis?
- A. Diakinesis
- B. Leptotene
- C. Zygotene
- D. Arachytene (Correct Answer)
Explanation: ***Arachytene*** - **Arachytene** is not a recognized stage of prophase I in meiosis. - The correct stages are leptotene, zygotene, pachytene, diplotene, and diakinesis. *Diakinesis* - **Diakinesis** is the final stage of prophase I, where homologous chromosomes condense further, and the nuclear envelope begins to break down. - Chiasmata terminalize, and the bivalents are ready for metaphase I. *Leptotene* - **Leptotene** is the first stage of prophase I, characterized by the condensation of chromatin into visible chromosomes. - Chromosomes appear as long, thin threads. *Zygotene* - **Zygotene** is the second stage of prophase I, where homologous chromosomes pair up in a process called **synapsis**, forming bivalents. - The synaptonemal complex begins to form between homologous chromosomes.
Question 152: Spermatogenesis begins at -
- A. Birth
- B. 5 years
- C. Puberty (Correct Answer)
- D. 18 years
Explanation: ***Puberty*** - **Spermatogenesis**, the process of sperm production, is initiated and sustained by the surge of **gonadotropin-releasing hormone (GnRH)**, which begins at puberty. - This hormonal signal leads to the secretion of **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)**, crucial for testicular function and sperm development. *Birth* - At birth, the male testes contain **spermatogonia**, but these cells remain dormant and do not begin active sperm production. - Hormonal levels at birth are not conducive to initiating spermatogenesis. *5 years* - While some hormonal changes occur in early childhood, they are not sufficient to trigger the full process of spermatogenesis. - The reproductive system is still in a quiescent state before puberty. *18 years* - By 18 years, spermatogenesis is typically well-established and has been ongoing for several years, having started at puberty. - This age marks a period of full reproductive maturity, not the initiation of sperm production.