NEET-PG 2012 Practice Questions

Q: Which bone has the maximum anatomical contribution to the floor of the orbit?

Maxillary. ***Maxillary*** - The **maxilla** contributes the most significantly to the **orbital floor**, forming approximately **75%** of its surface area. - The orbital plate of the maxilla is a thin, triangular bone that also forms the roof of the **maxillary sinus**. *Zygomatic* - The **zygomatic bone** forms the **lateral wall** and the **lateral portion** of the **orbital floor**. - Its contribution to the overall floor is less extensive than that of the maxilla (approximately 20-25%). *Sphenoid* - The **sphenoid bone** does **NOT** contribute to the **orbital floor** at all. - It forms parts of the **posterior wall** and **lateral wall** (via greater and lesser wings) of the orbit, but has no anatomical contribution to the floor. *Palatine* - The **palatine bone** (via its orbital process) contributes a very small, **posterior-most part** of the **orbital floor**. - Its contribution is minimal (less than 5%) compared to the maxilla and zygomatic bone.

Q: All are lateral branches of the abdominal aorta, EXCEPT which of the following?

Celiac trunk. ***Celiac trunk*** - The **celiac trunk** is an anterior branch of the abdominal aorta, supplying the foregut derivatives. - It arises from the ventral aspect of the aorta, distinguishing it from lateral branches. *Right testicular artery* - The **testicular arteries** (gonadal arteries) are paired lateral branches of the abdominal aorta. - They arise inferior to the renal arteries and descend to supply the testes in males. *Left renal artery* - The **renal arteries** [1] [3] are large paired lateral branches of the abdominal aorta. - They supply the kidneys [2] and typically arise just inferior to the superior mesenteric artery. *Middle suprarenal artery* - The **middle suprarenal arteries** are paired lateral branches, typically arising directly from the abdominal aorta. - They supply the suprarenal (adrenal) glands [2].

Q: During incision and drainage of ischiorectal abscess, which nerve is most likely to be injured?

Inferior rectal nerve. ***Inferior rectal nerve*** - The **inferior rectal nerve** innervates the **external anal sphincter** and the skin around the anus, making it vulnerable during an incision and drainage of an **ischiorectal abscess** due to its anatomical proximity. - Injury to this nerve can lead to **fecal incontinence** or altered sensation in the perianal region. *Superior rectal nerve* - The **superior rectal nerve** is primarily involved in the innervation of the **rectum** and is not directly located in the area of an **ischiorectal abscess**. - This nerve supplies the smooth muscle of the rectum and is not anatomically vulnerable during incision and drainage of an abscess in the ischiorectal fossa. *Superior gluteal nerve* - The **superior gluteal nerve** supplies the **gluteus medius**, **gluteus minimus**, and **tensor fasciae latae muscles**, which are typically located much more superior and lateral to an **ischiorectal abscess**. - Damage to this nerve causes a characteristic **Trendelenburg gait**, which is unrelated to perianal surgery. *Inferior gluteal nerve* - The **inferior gluteal nerve** innervates the **gluteus maximus muscle**, which is also located more superiorly and laterally relative to the **ischiorectal fossa**. - Injury to this nerve would primarily affect hip extension and is not a common complication of **ischiorectal abscess** drainage.

Q: Ovarian fossa is formed by all except?

Round ligament of ovary. ***Round ligament of ovary*** - The **round ligament of ovary** (ovarian ligament) connects the ovary to the lateral wall of the uterus and does NOT form any boundary of the ovarian fossa [1]. - It lies medial to the ovary and is not involved in forming the depression of the ovarian fossa [1]. - This ligament anchors the ovary but is separate from the peritoneal boundaries defining the fossa [1]. *Obliterated umbilical artery* - The **obliterated umbilical artery** (medial umbilical ligament) forms the **anterior boundary** of the ovarian fossa [2]. - This is a key anatomical landmark running along the lateral pelvic wall anterior to the ovary [2]. *Internal iliac artery* - The **internal iliac artery** forms the **posterior boundary** of the ovarian fossa [2]. - It lies on the lateral pelvic wall, deep and posterior to the ovarian fossa [2]. - This is one of the main structures defining the fossa's posterior limit [2]. *Ureter* - The **ureter** runs along the lateral pelvic wall and forms part of the **posterior/floor boundary** of the ovarian fossa [2]. - It passes posteroinferior to the ovary, contributing to the fossa's posterior limits [2].

Q: Which of the following substances is not derived from tyrosine?

Nicotinic acid. ***Nicotinic acid*** - **Nicotinic acid** (niacin, vitamin B3) is synthesized from **tryptophan** in the body, not tyrosine. - It plays a crucial role in metabolism as a precursor for NAD+ and NADH, which are involved in various enzymatic reactions. *Thyroxine* - **Thyroxine** (T4), a thyroid hormone, is derived from the amino acid **tyrosine**. - **Iodine** is incorporated into tyrosine residues on thyroglobulin to form monoiodotyrosine (MIT) and diiodotyrosine (DIT), which then couple to form T4 (and T3). *Melanin* - **Melanin**, the pigment responsible for skin, hair, and eye color, is synthesized from **tyrosine** through a pathway involving the enzyme **tyrosinase**. - This process involves the hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine (DOPA) and subsequent oxidation reactions. *Dopamine* - **Dopamine**, an important neurotransmitter, is synthesized from **tyrosine** in a two-step process in the brain and adrenal medulla. - Tyrosine is first hydroxylated to DOPA by **tyrosine hydroxylase**, and then DOPA is decarboxylated to dopamine by DOPA decarboxylase.

Q: What are isoenzymes?

Physically distinct forms of the same enzyme. ***Physically distinct forms of the same enzyme*** - Isoenzymes are **multiple forms of an enzyme** that catalyze the **same reaction** but differ in their **physical or biochemical properties**, such as electrophoretic mobility, optimal pH, or kinetic parameters. - These differences usually arise from **genetic variations** (different genes encoding isoforms) or **post-translational modifications** (e.g., phosphorylation, glycosylation). *Physically same forms of different enzymes* - This statement is incorrect as isoenzymes are forms of the **same enzyme**, not different enzymes. - While different enzymes can catalyze similar reactions in certain pathways, they are not referred to as isoenzymes if they are structurally identical. *Forms of same enzyme that catalyze different reactions* - This describes enzymes with **broad substrate specificity** or those that act on different substrates but are not necessarily isoenzymes. - Isoenzymes specifically catalyze the **same chemical reaction**, but they may do so with different efficiencies or under different regulatory controls. *Forms of different enzyme that catalyze same reactions* - This describes a scenario where different enzymes might exhibit **catalytic promiscuity** or broad specificity, but not isoenzymes. - Isoenzymes are always derived from the **same parent enzyme** and catalyze the identical reaction.

Q: Which of the following is an ω-6 fatty acid?

Linoleic acid. ***Linoleic acid*** - **Linoleic acid** (LA), an 18-carbon fatty acid with two double bonds (18:2), is classified as an **ω-6 fatty acid** because its first double bond is located at the sixth carbon atom from the methyl end of the fatty acid chain. - It is an **essential fatty acid** that must be obtained through diet, serving as a precursor for other ω-6 fatty acids like arachidonic acid. *Cervonic acid* - **Cervonic acid** is another name for **docosahexaenoic acid (DHA)**, which is an **ω-3 fatty acid** (22:6). - Its first double bond is located at the third carbon from the methyl end. *Alpha linolenic acid* - **Alpha-linolenic acid** (ALA) is an **ω-3 fatty acid** (18:3). - Its first double bond is located at the third carbon atom from the methyl end. *Elaidic acid* - **Elaidic acid** is a **trans fatty acid** (18:1 trans-9). - It is classified as an **ω-9 fatty acid** due to the position of its double bond, but its trans configuration is the primary distinguishing feature.

Q: The thickness of the endometrium at the time of implantation is:

7 - 10 mm. ***7 - 10 mm*** - At the time of **implantation** (day 6-10 post-fertilization, around day 20-24 of the menstrual cycle), the endometrium is in the **mid-secretory phase** and measures **7-10 mm** in thickness. - This is the **optimal thickness** for successful embryo implantation, characterized by a receptive endometrium with **decidualization**, **spiral artery development**, and **glycogen-rich glandular secretions**. - Endometrial thickness <7 mm is associated with **poor implantation rates** and reduced pregnancy success. *3 - 4 mm* - An endometrial thickness of 3-4 mm is **too thin** for successful implantation. - This thickness is typically seen in the **early proliferative phase** (immediately after menstruation), not during the implantation window. - Thin endometrium (<7 mm) is associated with **poor receptivity** and lower pregnancy rates in both natural conception and assisted reproduction. *20 - 30 mm* - An endometrial thickness of 20-30 mm is **abnormally thick** and not conducive to normal implantation. - Such thickness may indicate **endometrial hyperplasia**, **polyps**, or other pathological conditions requiring investigation. *30 - 40 mm* - An endometrial thickness of 30-40 mm is **severely abnormal** and would likely prevent successful implantation. - This extreme thickness suggests significant pathology such as **endometrial hyperplasia** or **malignancy** and requires urgent evaluation.

Q: What is the chromosomal translocation associated with Acute Myeloid Leukemia M3?

t(15;17). ***T (15,17)*** [1][2][3] - This translocation pertains to **Acute Promyelocytic Leukemia (APL)**, associated with the fusion gene **PML-RARA** [1][3]. - APL is characterized by **promyelocytes** with heavy granulation and a clinical presentation that includes coagulopathy [2][3]. *T (8, 21)* - This translocation is associated with **AML M2**, involving the **RUNX1-RUNX1T1** fusion gene [3]. - It does not correlate with the classic features of AML M3, which is specifically characterized by T (15,17). *T (9,11)* - Primarily seen in **AML M5**, this translocation is not related to the pathophysiology of AML M3. - The fusion commonly observed here is **MLL-AFF1**, which affects different types of leukemias, not APL. *T (18,21)* - This translocation does not have a significant association with any specific type of acute myeloid leukemia. - Unlike T (15,17), it is not linked to the classic features or unique clinical presentation seen in AML M3. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 620-621. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 621-622. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 620.

Q: Which tumor marker is most commonly associated with lung and breast carcinoma?

CEA. ***CEA*** - **Carcinoembryonic antigen (CEA)** is a tumor marker commonly associated with **lung** and **breast cancers** [1]. - Elevated levels of CEA are often observed in **various malignancies**, making it useful for monitoring treatment response and recurrence. *CA-15-3* - While **CA-15-3** is a breast cancer marker, it is less specific than CEA and often used primarily for **monitoring** but not for initial diagnosis. - It is primarily elevated in **breast carcinoma**, not typically associated with **lung cancer**. *11CG* - This ppears to be incorrectly referenced and may not exist as a recognized tumor marker for lung or breast cancer. - There are no clinical associations with lung or breast cancer, making it irrelevant in this context. *AFP* - **Alpha-fetoprotein (AFP)** is primarily associated with **liver** and **germ cell tumors**, not commonly associated with lung or breast cancers [1]. - Elevated AFP levels do not correlate with lung or breast carcinomas, distinguishing it from CEA's relevance. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 346.

Question 1

Which bone has the maximum anatomical contribution to the floor of the orbit?

Accepted Answer

Maxillary

Answer

Zygomatic

Answer

Sphenoid

Answer

Palatine

Question 2

All are lateral branches of the abdominal aorta, EXCEPT which of the following?

Accepted Answer

Celiac trunk

Answer

Right testicular artery

Answer

Left renal artery

Answer

Middle suprarenal artery

Question 3

During incision and drainage of ischiorectal abscess, which nerve is most likely to be injured?

Accepted Answer

Inferior rectal nerve

Answer

Superior rectal nerve

Answer

Superior gluteal nerve

Answer

Inferior gluteal nerve

Question 4

Ovarian fossa is formed by all except?

Accepted Answer

Round ligament of ovary

Answer

Internal iliac artery

Answer

Ureter

Answer

Obliterated umbilical artery

Question 5

Which of the following substances is not derived from tyrosine?

Accepted Answer

Nicotinic acid

Answer

Thyroxine

Answer

Melanin

Answer

Dopamine

Question 6

What are isoenzymes?

Accepted Answer

Physically distinct forms of the same enzyme

Answer

Physically same forms of different enzymes

Answer

Forms of same enzyme that catalyze different reactions

Answer

Forms of different enzyme that catalyze same reactions

Question 7

Which of the following is an ω-6 fatty acid?

Accepted Answer

Linoleic acid

Answer

Cervonic acid

Answer

Alpha linolenic acid

Answer

Elaidic acid

Question 8

The thickness of the endometrium at the time of implantation is:

Accepted Answer

7 - 10 mm

Answer

20 - 30 mm

Answer

30 - 40 mm

Answer

3 - 4 mm

Question 9

What is the chromosomal translocation associated with Acute Myeloid Leukemia M3?

Accepted Answer

t(15;17)

Answer

t(18;21)

Answer

t(9;11)

Answer

t(8;21)

Question 10

Which tumor marker is most commonly associated with lung and breast carcinoma?

Accepted Answer

CEA

Answer

hCG

Answer

AFP

Answer

CA-15-3

NEET-PG 2012

Anatomy

Biochemistry

Obstetrics and Gynecology

Pathology