UPSC-CMS 2017 — Anatomy

Q: The external opening of branchial fistula is present in :

Lower third of the neck. ***Lower third of the neck*** - The external opening of a branchial fistula is typically found in the **lower third of the anterolateral neck**, anterior to the sternocleidomastoid muscle [1]. - This location corresponds to the embryological remnants of the second branchial cleft failing to close completely. *Middle third of the neck* - While other branchial anomalies might present in the middle third, the classic external opening of a **branchial fistula** is usually lower [1]. - Cysts (branchial cleft cysts) are more commonly found in the middle third [1]. *Upper third of the neck* - Anomalies in the upper third of the neck are less common for an external branchial fistula opening. - This region is more associated with anomalies of the first branchial cleft [1]. *Suprasternal notch* - The suprasternal notch is located at the base of the neck, and while cysts can occur in this area (e.g., cervicomediastinal thymic cysts), it is not the typical site for a **branchial fistula** opening. - This location is often associated with abnormalities of thyroid development or other midline defects. [Practice more Anatomy PYQs on OnCourse]

Q: Important landmark in submandibular gland dissection is:

Posterior border of mylohyoid muscle. ***Posterior border of mylohyoid muscle*** - Lifting the **posterior border of the mylohyoid muscle** exposes the deep part of the submandibular gland and crucial structures like the **lingual nerve** and **Wharton's duct**. - This landmark serves as a critical guide during dissection, helping to protect adjacent nerves and vessels while ensuring complete gland removal. *Anterior belly of digastric muscle* - The anterior belly of the digastric muscle forms the anterior boundary of the **digastric triangle**, which contains the superficial portion of the submandibular gland. - While relevant for defining the superficial borders, it is not the key landmark for accessing the deep part of the gland or protecting vital structures during dissection. *Facial artery* - The **facial artery** is closely associated with the submandibular gland, usually looping over or through it, but it is not a primary surgical landmark for deeper dissection or critical structure identification. - It is often ligated or preserved during dissection due to its proximity, but its position can vary, making it less reliable as a consistent access guide. *Posterior belly of digastric muscle* - The posterior belly of the digastric muscle forms the posterior boundary of the digastric triangle. - It is relevant for defining the superficial boundaries of the gland but does not provide direct access or guide the deeper dissection of the submandibular gland or protection of critical associated nerves. [Practice more Anatomy PYQs on OnCourse]

Q: The umbilical cord normally contains:

Two arteries and one vein. ***Two arteries and one vein*** - The umbilical cord typically contains **two umbilical arteries** [1] that carry deoxygenated blood and waste products from the fetus to the placenta. - It also contains **one umbilical vein** [2, 3] that carries oxygenated, nutrient-rich blood from the placenta to the fetus. - This is the **normal anatomical configuration** of the umbilical cord. *One artery and two veins* - This configuration is **incorrect** as there is only **one umbilical vein** [2] in the normal umbilical cord, not two. - The presence of a single artery (single umbilical artery - SUA) is a recognized anomaly associated with certain fetal abnormalities, but even in SUA, there is only one vein. *One artery and one vein* - This arrangement is **incorrect** as the normal umbilical cord contains **two arteries**, not one [1]. - Single umbilical artery (SUA) is the most common umbilical cord anomaly, occurring in about 1% of pregnancies, but this is still an abnormal finding. *Two arteries and two veins* - This statement is **incorrect** because the normal umbilical cord contains only **one umbilical vein**, not two. - The presence of two veins would be a rare anomaly and is not part of normal umbilical cord anatomy. [Practice more Anatomy PYQs on OnCourse]

Q: Regarding “conjoined twins”, which of the following statements is/are true? 1. These are always monozygotic 2. These result when division occurs before the embryonic disc is formed 3. Most common variety is thoracopagus Select the correct answer using the code given below:

1 and 3 only. ***1 and 3 only*** - **Identical (monozygotic)** twins are always conjoined because they develop from a single fertilized egg that imperfectly separates. - **Incomplete division** of the embryonic disc after 13 days from fertilization causes conjoined twins [1]. **Thoracopagus** is the most common type, where twins are joined at the chest [1, 2]. *1 and 2 only* - Conjoined twins are indeed **monozygotic**, but the timing of division is typically *after* the embryonic disc is formed, not before [1]. - Division *before* the embryonic disc forms would usually lead to separate monozygotic twins [1]. *2 and 3 only* - While **thoracopagus** is the most common variety [2], statement 2 regarding the timing of division is incorrect. - Conjoined twins are a result of incomplete separation *after* the formation of the embryonic disc, typically around 13-15 days post-fertilization [1]. *1, 2 and 3* - This option incorrectly states that division occurs *before* the embryonic disc is formed. - The formation of conjoined twins results from an *incomplete* splitting of the **monozygotic embryo** *after* the embryonic disc has already begun to differentiate [1]. [Practice more Anatomy PYQs on OnCourse]

4 Previous Year Questions with Answers & Explanations

Questions

All Subjects Anatomy (4)Anesthesiology (1)Biochemistry (1)Community Medicine (36)Dermatology (2)Internal Medicine (8)Microbiology (2)Obstetrics and Gynecology (26)Ophthalmology (2)Pathology (4)Pediatrics (1)Pharmacology (3)Physiology (2)Surgery (23)

The external opening of branchial fistula is present in :

Important landmark in submandibular gland dissection is:

The umbilical cord normally contains:

Regarding “conjoined twins”, which of the following statements is/are true? 1. These are always monozygotic 2. These result when division occurs before the embryonic disc is formed 3. Most common variety is thoracopagus Select the correct answer using the code given below:

UPSC-CMS 2017 - Anatomy UPSC-CMS Practice Questions and MCQs

Question 1: The external opening of branchial fistula is present in :

A. Middle third of the neck
B. Lower third of the neck (Correct Answer)
C. Upper third of the neck
D. Suprasternal notch

Explanation: ***Lower third of the neck*** - The external opening of a branchial fistula is typically found in the **lower third of the anterolateral neck**, anterior to the sternocleidomastoid muscle [1]. - This location corresponds to the embryological remnants of the second branchial cleft failing to close completely. *Middle third of the neck* - While other branchial anomalies might present in the middle third, the classic external opening of a **branchial fistula** is usually lower [1]. - Cysts (branchial cleft cysts) are more commonly found in the middle third [1]. *Upper third of the neck* - Anomalies in the upper third of the neck are less common for an external branchial fistula opening. - This region is more associated with anomalies of the first branchial cleft [1]. *Suprasternal notch* - The suprasternal notch is located at the base of the neck, and while cysts can occur in this area (e.g., cervicomediastinal thymic cysts), it is not the typical site for a **branchial fistula** opening. - This location is often associated with abnormalities of thyroid development or other midline defects.

Question 2: Important landmark in submandibular gland dissection is:

A. Posterior border of mylohyoid muscle (Correct Answer)
B. Anterior belly of digastric muscle
C. Facial artery
D. Posterior belly of digastric muscle

Explanation: ***Posterior border of mylohyoid muscle*** - Lifting the **posterior border of the mylohyoid muscle** exposes the deep part of the submandibular gland and crucial structures like the **lingual nerve** and **Wharton's duct**. - This landmark serves as a critical guide during dissection, helping to protect adjacent nerves and vessels while ensuring complete gland removal. *Anterior belly of digastric muscle* - The anterior belly of the digastric muscle forms the anterior boundary of the **digastric triangle**, which contains the superficial portion of the submandibular gland. - While relevant for defining the superficial borders, it is not the key landmark for accessing the deep part of the gland or protecting vital structures during dissection. *Facial artery* - The **facial artery** is closely associated with the submandibular gland, usually looping over or through it, but it is not a primary surgical landmark for deeper dissection or critical structure identification. - It is often ligated or preserved during dissection due to its proximity, but its position can vary, making it less reliable as a consistent access guide. *Posterior belly of digastric muscle* - The posterior belly of the digastric muscle forms the posterior boundary of the digastric triangle. - It is relevant for defining the superficial boundaries of the gland but does not provide direct access or guide the deeper dissection of the submandibular gland or protection of critical associated nerves.

Question 3: The umbilical cord normally contains:

A. One artery and two veins
B. One artery and one vein
C. Two arteries and two veins
D. Two arteries and one vein (Correct Answer)

Explanation: ***Two arteries and one vein*** - The umbilical cord typically contains **two umbilical arteries** [1] that carry deoxygenated blood and waste products from the fetus to the placenta. - It also contains **one umbilical vein** [2, 3] that carries oxygenated, nutrient-rich blood from the placenta to the fetus. - This is the **normal anatomical configuration** of the umbilical cord. *One artery and two veins* - This configuration is **incorrect** as there is only **one umbilical vein** [2] in the normal umbilical cord, not two. - The presence of a single artery (single umbilical artery - SUA) is a recognized anomaly associated with certain fetal abnormalities, but even in SUA, there is only one vein. *One artery and one vein* - This arrangement is **incorrect** as the normal umbilical cord contains **two arteries**, not one [1]. - Single umbilical artery (SUA) is the most common umbilical cord anomaly, occurring in about 1% of pregnancies, but this is still an abnormal finding. *Two arteries and two veins* - This statement is **incorrect** because the normal umbilical cord contains only **one umbilical vein**, not two. - The presence of two veins would be a rare anomaly and is not part of normal umbilical cord anatomy.

Question 4: Regarding “conjoined twins”, which of the following statements is/are true? 1. These are always monozygotic 2. These result when division occurs before the embryonic disc is formed 3. Most common variety is thoracopagus Select the correct answer using the code given below:

A. 1 and 2 only
B. 2 and 3 only
C. 1, 2 and 3
D. 1 and 3 only (Correct Answer)

Explanation: ***1 and 3 only*** - **Identical (monozygotic)** twins are always conjoined because they develop from a single fertilized egg that imperfectly separates. - **Incomplete division** of the embryonic disc after 13 days from fertilization causes conjoined twins [1]. **Thoracopagus** is the most common type, where twins are joined at the chest [1, 2]. *1 and 2 only* - Conjoined twins are indeed **monozygotic**, but the timing of division is typically *after* the embryonic disc is formed, not before [1]. - Division *before* the embryonic disc forms would usually lead to separate monozygotic twins [1]. *2 and 3 only* - While **thoracopagus** is the most common variety [2], statement 2 regarding the timing of division is incorrect. - Conjoined twins are a result of incomplete separation *after* the formation of the embryonic disc, typically around 13-15 days post-fertilization [1]. *1, 2 and 3* - This option incorrectly states that division occurs *before* the embryonic disc is formed. - The formation of conjoined twins results from an *incomplete* splitting of the **monozygotic embryo** *after* the embryonic disc has already begun to differentiate [1].