Anatomy
6 questionsWhich of the following is NOT a surface marking of the oblique fissure of the lung?
Coronary sinus develops from?
Which is derived from Wolffian duct?
In which region of the human spine is the number of vertebrae usually constant?
All the following are characteristics of the oculomotor nerve except:
Which muscle stabilizes the clavicle during movement of the shoulder?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 211: Which of the following is NOT a surface marking of the oblique fissure of the lung?
- A. 6th costal cartilage
- B. T3
- C. 5th rib
- D. 7th rib (Correct Answer)
Explanation: ***7th rib*** - The **oblique fissure** typically extends from the spine at approximately the **T3 vertebral level** anteriorly to the **6th costal cartilage**. [1] - The **7th rib** is generally inferior to the typical anterior termination point of the oblique fissure. [1] *T3* - The **oblique fissure** begins posteriorly at the level of the **spinous process of T3**. [1] - This marks the superior-posterior extent of the fissure on the surface. *5th rib* - The **oblique fissure** crosses the **5th intercostal space** on the lateral chest wall. [1] - This point helps map the fissure's path between its posterior and anterior endpoints. *6th costal cartilage* - The **oblique fissure** terminates anteriorly near the **6th costal cartilage** in the midclavicular line. [1] - This represents the inferior-anterior most point of the fissure on the chest wall.
Question 212: Coronary sinus develops from?
- A. Truncus arteriosus
- B. Conus
- C. Sinus venosus (Correct Answer)
- D. AV canal
Explanation: Sinus venosus - The sinus venosus is a primordial cardiac chamber that receives venous blood from the body and placenta in the early embryonic heart. - The left horn of the sinus venosus loses its connection with the systemic venous circulation and becomes the coronary sinus, which drains most of the cardiac veins into the right atrium [1, 4]. Truncus arteriosus - The truncus arteriosus is the embryonic precursor to the ascending aorta and pulmonary trunk. - It does not contribute to the development of the coronary sinus. Conus - The conus (or conus cordis) is the outflow portion of the primitive ventricle and differentiates into the outflow tracts of the right (infundibulum) and left (aortic vestibule) ventricles. - It is not involved in the formation of the coronary sinus. AV canal - The atrioventricular (AV) canal connects the primitive atrium and ventricle and is crucial for the formation of the AV valves and septation of the heart chambers. - It does not directly develop into the coronary sinus.
Question 213: Which is derived from Wolffian duct?
- A. Appendix of epididymis (Correct Answer)
- B. Appendix of the testis
- C. Uterine structure
- D. Hydatid of Morgagni
Explanation: The **appendix of the epididymis** is a vestigial structure directly derived from the mesonephric (Wolffian) duct in males. It is an embryological remnant of this duct, located at the head of the epididymis. *Appendix of the testis* - The **appendix of the testis** (hydatid of Morgagni) is a remnant of the paramesonephric (Müllerian) duct, not the Wolffian duct. - It is usually found on the upper pole of the testis, typically near the epididymis. *Uterine structure* - **Uterine structures** (uterus, fallopian tubes, and upper vagina) are derived from the paramesonephric (Müllerian) ducts in females [1]. - The Wolffian ducts largely regress in females due to the absence of testosterone. *Hydatid of Morgagni* - The term **hydatid of Morgagni** can refer to the appendix of the testis (Müllerian duct remnant) or, less commonly, to the appendix of the epididymis (Wolffian duct remnant). - However, in common clinical and anatomical usage, it almost exclusively refers to the **appendix of the testis**, which is a Müllerian duct derivative.
Question 214: In which region of the human spine is the number of vertebrae usually constant?
- A. Cervical (Correct Answer)
- B. Thoracic
- C. Lumbar
- D. Sacral
Explanation: ***Cervical*** - The human cervical spine almost universally consists of **seven vertebrae (C1-C7)**, making it the most constant region in terms of vertebral number. - This consistent number is crucial for normal neck movement and protection of vital neurological structures. *Thoracic* - While typically having **12 vertebrae**, variations in the thoracic region can occur, with some individuals having 11 or 13 due to transitional vertebrae. - These variations are less common but indicate that the number is not as strictly constant as in the cervical spine. *Lumbar* - The lumbar spine commonly has **five vertebrae (L1-L5)**, but variations such as four or six lumbar vertebrae can be seen due to lumbarization or sacralization. - **Lumbarization** involves the first sacral segment detaching, while **sacralization** involves the fifth lumbar vertebra fusing with the sacrum. *Sacral* - The sacrum is formed by the fusion of **five sacral vertebrae (S1-S5)**, but the number of *individual identifiable* vertebrae before fusion, or in cases of incomplete fusion, can vary. - The sacral region itself is a fused structure, and while it originates from five segments, the concept of "number of vertebrae" can be ambiguous due to its characteristic fusion.
Question 215: All the following are characteristics of the oculomotor nerve except:
- A. Carries parasympathetic nerve fibres
- B. Supplies inferior oblique muscle
- C. Enters orbit through the inferior orbital fissure (Correct Answer)
- D. Enters orbit through the superior orbital fissure
Explanation: ***Enters orbit through the inferior orbital fissure*** - The oculomotor nerve **does not** enter the orbit through the **inferior orbital fissure**; it enters via the **superior orbital fissure**. - The **inferior orbital fissure** transmits structures like the **maxillary nerve (V2)**, **zygomatic nerve**, and **inferior ophthalmic vein**. *Carries parasympathetic nerve fibres* - The oculomotor nerve contains **parasympathetic preganglionic fibers** that synapse in the **ciliary ganglion** [1]. - These fibers control **pupillary constriction** (via the **sphincter pupillae**) and **accommodation** (via the **ciliary muscle**) [1]. *Supplies inferior oblique muscle* - The **inferior oblique muscle** is one of the **extraocular muscles** innervated by the **oculomotor nerve (CN III)** [2]. - This muscle works to **elevate** and **externally rotate** the eye [2]. *Enters orbit through the superior orbital fissure* - The oculomotor nerve indeed passes through the **superior orbital fissure** to enter the orbit. - This fissure serves as the passage for several cranial nerves and vessels, including the **oculomotor (III)**, **trochlear (IV)**, **abducens (VI)**, and branches of the **ophthalmic nerve (V1)**.
Question 216: Which muscle stabilizes the clavicle during movement of the shoulder?
- A. Pectoralis major
- B. Latissimus dorsi
- C. Subclavius (Correct Answer)
- D. Serratus anterior
Explanation: ***Subclavius*** - The **subclavius muscle** originates from the first rib and inserts into the inferior surface of the clavicle, acting to **depress the clavicle** and prevent its displacement, thus enhancing shoulder stability during movement. - It plays a crucial role in protecting the underlying **neurovascular structures** (brachial plexus and subclavian vessels) from external trauma to the shoulder. *Pectoralis major* - This large, fan-shaped muscle primarily functions in **adduction, medial rotation, and flexion of the humerus** at the shoulder joint [1]. - It does not directly stabilize the clavicle but rather acts on the arm. *Latissimus dorsi* - The **latissimus dorsi** is a broad muscle of the back responsible for **extension, adduction, and internal rotation of the humerus** [1]. - Its actions are mainly on the humerus and it does not directly stabilize the clavicle. *Serratus anterior* - The **serratus anterior** muscle primarily **protracts and rotates the scapula**, keeping it pressed against the thoracic wall. - While it's essential for **scapular stability** and overhead arm movements, it does not directly stabilize the clavicle.
Biochemistry
2 questionsIn the electron transport chain (ETC), which enzyme does cyanide inhibit?
Enzymes of glycolysis are found in:
NEET-PG 2012 - Biochemistry NEET-PG Practice Questions and MCQs
Question 211: In the electron transport chain (ETC), which enzyme does cyanide inhibit?
- A. Complex II (Succinate dehydrogenase)
- B. Cytochrome c oxidase (Complex IV) (Correct Answer)
- C. Complex I (NADH dehydrogenase)
- D. Complex III (Cytochrome bc1 complex)
Explanation: ***Cytochrome c oxidase (Complex IV)*** - Cyanide binds to the **ferric iron (Fe3+)** in the heme a3 component of cytochrome c oxidase, blocking the final transfer of electrons to oxygen. - This inhibition effectively halts the entire **electron transport chain** and **oxidative phosphorylation**, leading to rapid cellular energy depletion. *Complex I (NADH dehydrogenase)* - While other toxins can inhibit Complex I (e.g., rotenone, amytal), **cyanide specifically targets Complex IV**. - Inhibition here prevents the entry of electrons from **NADH** into the ETC, but it's not cyanide's primary site of action. *Complex III (Cytochrome bc1 complex)* - Complex III is involved in transferring electrons from **ubiquinol** to cytochrome c, but it is not directly inhibited by cyanide. - Antimycin A is a well-known inhibitor of Complex III. *Complex II (Succinate dehydrogenase)* - Complex II directly receives electrons from **succinate** in the citric acid cycle and passes them to ubiquinone, bypassing Complex I. - Cyanide does not inhibit Complex II; inhibitors of this complex include malonate.
Question 212: Enzymes of glycolysis are found in:
- A. Cytosol (Correct Answer)
- B. Cell membrane
- C. Mitochondria
- D. Ribosomes
Explanation: ***Cytosol*** - Glycolysis is a metabolic pathway that occurs in the **cytosol** of cells. - All the enzymes required for the conversion of glucose to pyruvate are freely dissolved in the **cytoplasm**. *Cell membrane* - The cell membrane is primarily involved in **regulating the passage of substances** into and out of the cell, as well as cell signaling. - Glycolytic enzymes are not associated with the cell membrane. *Mitochondria* - Mitochondria are the primary site of **oxidative phosphorylation** and the **citric acid cycle**, not glycolysis. - While pyruvate (the end product of glycolysis) moves into the mitochondria for further metabolism, the initial glycolytic steps do not occur there. *Ribosomes* - Ribosomes are responsible for **protein synthesis** (translation). - They do not contain enzymes for metabolic pathways like glycolysis.
Obstetrics and Gynecology
1 questionsBlastocyst makes contact with endometrium on ?
NEET-PG 2012 - Obstetrics and Gynecology NEET-PG Practice Questions and MCQs
Question 211: Blastocyst makes contact with endometrium on ?
- A. < 3 days
- B. 5 - 7 days (Correct Answer)
- C. 8 - 11 days
- D. 15-16 days
Explanation: ***5-7 days*** - The **blastocyst makes initial contact** (apposition) with the **endometrium** around **day 5-6 after fertilization**. - **Implantation**, which includes adhesion and invasion, typically begins around day 6 and is complete by day 10. - This timeframe allows the blastocyst to travel from the fallopian tube to the uterus and for the uterine lining to be optimally prepared. *< 3 days* - Within the first few days after fertilization, the zygote is still undergoing **cleavage** and development into a **morula**, then a young blastocyst, while traveling down the fallopian tube. - It has not yet reached the uterus or developed sufficiently to interact with the endometrium. *8-11 days* - By 8-11 days, the process of implantation is usually **well underway or completed**, with the blastocyst already invading the endometrial wall. - Initial contact and attachment occur prior to this period. *15-16 days* - This timeframe is well beyond the typical window for initial blastocyst contact and implantation. - By 15-16 days post-fertilization, the embryo would be undergoing **gastrulation** and early organogenesis, assuming successful implantation.
Physiology
1 questionsHaploid number of chromosomes is first seen in?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 211: Haploid number of chromosomes is first seen in?
- A. Spermatogonia
- B. Primary spermatocytes
- C. Secondary spermatocyte (Correct Answer)
- D. Spermatids
Explanation: ***Secondary spermatocyte*** - A secondary spermatocyte is formed after **meiosis I**, where the homologous chromosomes are separated, resulting in a cell with a **haploid number of chromosomes (n)**, although each chromosome still consists of two sister chromatids. - This is the **first stage** where haploidy is achieved in spermatogenesis. - These cells are transient and quickly undergo meiosis II to form spermatids. *Spermatogonia* - Spermatogonia are **diploid (2n)** germline stem cells that undergo mitosis to produce more spermatogonia or differentiate into primary spermatocytes. - They contain the full complement of chromosomes found in somatic cells. *Primary spermatocytes* - Primary spermatocytes are also **diploid (2n)** cells that enter meiosis I. - Before meiosis I, DNA replication occurs, so each chromosome consists of two sister chromatids, but the cell still maintains a diploid chromosome number. *Spermatids* - Spermatids are formed after **meiosis II** from secondary spermatocytes and are also **haploid (n)**. - However, secondary spermatocytes become haploid **earlier** in the process, immediately following the reductional division of meiosis I.