NEET-PG 2012 Practice Questions

Q: Primordial germ cells are derived from:

Yolk sac. ***Yolk sac*** - **Primordial germ cells (PGCs)** arise from **epiblast** cells but are first identifiable in the wall of the **yolk sac** during the **3rd week** of development. - From the yolk sac, they migrate during the **4th-6th week** through the dorsal mesentery to reach the developing **genital ridges** (gonads) where they form **gametes** [2]. - The yolk sac is considered the site where PGCs are recognized and begin their journey to the gonads. *Neural crest* - Neural crest cells are multipotent cells that migrate to various locations and differentiate into structures like **neurons**, **glial cells**, **melanocytes**, and **facial cartilage**, not germ cells. - They arise from the dorsal part of the **neural tube** during neurulation. *Genital ridge* - The genital ridge is the embryonic structure that develops into the **gonads** (testes or ovaries) [1]. - Primordial germ cells migrate *to* the genital ridge, but they do not originate *from* it — it is their destination, not their source. *Somatopleuritic mesoderm* - **Somatopleuritic mesoderm** (somatic mesoderm) forms the **parietal layer** of serous membranes, the dermis of the body wall, and the skeletal elements of the limbs. - It does not give rise to **primordial germ cells**.

Q: Which of the following is NOT a branch of 1st part of maxillary artery?

Greater palatine artery. ***Greater palatine artery*** - This artery is a branch of the **third part** of the maxillary artery, which supplies the palate. - The third part of the maxillary artery (also known as the pterygopalatine part) gives off branches that pass through the pterygopalatine fossa. *Middle meningeal artery* - This is a significant branch of the **first part** of the maxillary artery, entering the cranial cavity via the **foramen spinosum** to supply the dura mater. - It is often injured in head trauma, leading to an **epidural hematoma**. *Accessory meningeal artery* - This artery also arises from the **first part** of the maxillary artery and enters the skull through the **foramen ovale** to supply the dura mater. - It is a smaller branch compared to the middle meningeal artery. *Inferior alveolar artery* - It is a branch of the **first part** of the maxillary artery, descending to enter the mandible via the **mandibular foramen** to supply the teeth and bone of the mandible. - It gives off the **mylohyoid branch** before entering the mandibular foramen.

Q: What is the anatomical significance of the Rhinion in relation to the osseocartilaginous junction?

Rhinion. ***Correct Answer: Rhinion*** - The **rhinion** is the **most prominent anterior point of the nasal bone**, often palpable as a slight bump or angulation on the dorsum of the nose. - It marks the anatomical location of the **osseocartilaginous junction** of the nasal dorsum, where the bony nasal framework transitions to the cartilaginous framework. - This is the key anatomical landmark that defines the transition from bone to cartilage in the external nose. *Incorrect: Nasion* - The **nasion** is located at the **root of the nose**, specifically at the most anterior and superior point of the nasofrontal suture. - It is a bony landmark and does not directly relate to the osseocartilaginous junction of the nasal dorsum. *Incorrect: Radix* - The **radix** (or nasal root) refers to the **uppermost part of the nose**, corresponding to the nasion. - It defines the point where the nose begins to project from the forehead and is a bony landmark, not directly related to the osseocartilaginous junction. *Incorrect: Columella* - The **columella** is the **fleshy, narrow strip of tissue that separates the nostrils**. - It forms the inferior segment of the nasal septum and is composed of skin, soft tissue, and the medial crura of the alar cartilages, thus having no direct relation to the osseocartilaginous junction of the nasal dorsum.

Q: Which of the following structures is not derived from the ectoderm?

Eustachian tube. ***Eustachian tube*** - The **Eustachian tube** (auditory tube) is derived from the **endoderm**, specifically from the first pharyngeal pouch. - It connects the nasopharynx to the middle ear and is responsible for equalizing pressure [1]. *Lens* - The **lens** of the eye develops from the surface ectoderm through an invagination called the **lens placode**. - This ectodermal origin is crucial for its transparency and refractive properties. *Brain* - The **brain** is a primary derivative of the ectoderm, specifically the **neural tube**, which forms from the neural plate during neurulation. - This ectodermal origin gives rise to the entire central nervous system. *Retina* - The **retina** of the eye, along with the optic nerve, develops from the **neuroectoderm** (a part of the neural tube). - Its ectodermal origin is essential for its light-sensing function.

Q: Which vitamin is involved in one-carbon transfer reactions?

Folic acid. ***Folic acid*** - **Folic acid (Vitamin B9)** is a crucial coenzyme in the form of **tetrahydrofolate (THF)**, which acts as a carrier of **one-carbon units**. - These one-carbon units are essential for various metabolic pathways, including the synthesis of **purines**, **thymidylate**, and the metabolism of several **amino acids**. *Pantothenic acid* - **Pantothenic acid (Vitamin B5)** is a precursor to **Coenzyme A (CoA)**, which plays a central role in fatty acid metabolism and the **Krebs cycle**, not one-carbon transfers. - CoA is involved in transferring **acetyl groups**, not one-carbon units. *Niacin* - **Niacin (Vitamin B3)** is a component of **NAD+** and **NADP+**, which are vital coenzymes in **redox reactions** (electron transfer), not one-carbon metabolism. - It functions primarily in **energy metabolism** as an electron carrier. *Thiamine* - **Thiamine (Vitamin B1)** is a coenzyme for **dehydrogenase reactions** and **transketolase** in the **pentose phosphate pathway**, which are involved in carbohydrate metabolism. - It does not directly participate in one-carbon transfer reactions.

Q: Which amino acids are involved in the formation of purines?

Aspartate, glycine, glutamine. ***Aspartate, glycine, glutamine*** - **Glycine** provides the largest single contribution to the purine ring structure: carbons at positions 4 and 5, and nitrogen at position 7 (the entire glycine molecule is incorporated). - **Aspartate** contributes the nitrogen atom at position 1 of the purine ring. - **Glutamine** donates two nitrogen atoms to the purine ring, specifically at positions 3 and 9. *Aspartate, glycine* - While both **aspartate** and **glycine** are crucial, **glutamine** is also required for the complete synthesis of the purine ring, contributing two nitrogen atoms. - Omission of glutamine makes this option incomplete for the full complement of amino acids involved. *Aspartate, glutamate* - **Glutamate** is not directly involved as an amino acid precursor contributing atoms to the purine ring structure. - **Glutamine**, an amide of glutamate, is the active donor of nitrogen atoms for purine synthesis. *Aspartic acid, glycine, uric acid* - **Aspartic acid** is another name for aspartate, and **glycine** is correctly identified as a precursor. - However, **uric acid** is the end product of purine catabolism, not an amino acid involved in its synthesis.

Q: When differentiated cells transform to form cells characteristic of other tissues, the process is called as -

Trans-differentiation. ***Trans-differentiation*** - **Trans-differentiation** refers to the direct conversion of one differentiated cell type into another differentiated cell type without entering a pluripotent stem cell state. - This process is achieved by altering the **gene expression profile** of existing cells to adopt the characteristics of a different lineage. *De-differentiation* - **De-differentiation** is the process where a specialized cell loses its specific characteristics and reverts to a more primitive or stem cell-like state. - This is often observed in certain disease processes, like cancer, or in response to injury where cells regain limited proliferative capacity. *Re-differentiation* - **Re-differentiation** typically describes a cell that has undergone de-differentiation and then differentiates again into a new or its original cell type. - This process is often seen in tissue repair, where progenitor cells proliferate and then re-differentiate to replace damaged tissue. *Sub-differentiation* - **Sub-differentiation** is not a standard or recognized term in cell biology or developmental biology to describe the transformation of stem cells into other tissue types. - The term does not have a defined meaning within the context of cellular lineage alterations.

Q: Which type of carbohydrate is absorbed most efficiently from the gastrointestinal tract?

Monosaccharides. ***Monosaccharides*** - **Monosaccharides**, like glucose and fructose, are the simplest forms of carbohydrates and do not require further digestion. - They are directly absorbed into the bloodstream from the intestinal lumen via specific **transporters** on the enterocyte membrane. *Disaccharides* - **Disaccharides**, such as sucrose and lactose, must first be broken down into their constituent monosaccharides by **brush border enzymes** (e.g., lactase, sucrase) before absorption can occur. - This additional enzymatic step makes their absorption less efficient than that of monosaccharides. *Polysaccharides* - **Polysaccharides**, including starch and glycogen, are complex carbohydrates requiring extensive digestion by enzymes like **amylase** in the mouth and small intestine. - This multi-step breakdown into monosaccharides is the least efficient process and takes the longest time. *5-carbon sugars* - While 5-carbon sugars (**pentoses**) like ribose and deoxyribose are monosaccharides and can be absorbed, they are not a primary energy source in the diet and are not absorbed as efficiently or in as large quantities as the metabolically more significant 6-carbon monosaccharides (hexoses like glucose). - The question asks which *type* of carbohydrate is most efficiently absorbed, and **monosaccharides** as a general category (including 6-carbon sugars) are the most efficient.

Q: What is the normal range of interstitial pressure?

-5 to 0 mmHg. ***-5 to 0 mmHg*** - The interstitial fluid is normally under a **slight negative pressure**, typically ranging from **-5 to 0 mmHg** - This negative pressure helps pull fluid from the capillaries into the interstitial space and facilitates **lymphatic drainage** - Maintained by continuous drainage of fluid and proteins by the **lymphatic system** - This range is the commonly accepted value in standard physiology references for Indian medical exams *-3 to 0 mmHg* - While this range acknowledges the typically **negative nature** of interstitial pressure, it represents a slightly narrower range - Some sources cite this as the average range, but **-5 to 0 mmHg** is the more commonly accepted standard range - Not the most precise or widely cited range for exam purposes *0 to 5 mmHg* - This range suggests a **positive interstitial pressure**, which is generally **abnormal** - Indicates **edema formation** due to excess fluid accumulation in the interstitial space - Positive pressure impairs fluid reabsorption and lymphatic drainage - Represents pathological fluid dynamics *5 to 10 mmHg* - Represents significant **positive interstitial pressure** leading to severe **interstitial edema** - Markedly impairs tissue function and fluid exchange - Indicates pathological conditions where capillary filtration far exceeds lymphatic drainage capacity - Associated with severe edematous states

Q: Nonshivering thermogenesis in adults is due to:

Brown fat between the shoulders. ***Brown fat between the shoulders*** - In adults, the primary **effector tissue** for **non-shivering thermogenesis** is **brown adipose tissue (BAT)**, with major depots located between the shoulders, around the neck, and along the spine. - **BAT** contains specialized mitochondria with **uncoupling protein 1 (UCP1)** that uncouples oxidative phosphorylation, generating heat instead of ATP. - This is the tissue where non-shivering thermogenesis actually occurs, making it the direct answer to what non-shivering thermogenesis is "due to." *Noradrenaline* - **Noradrenaline** is the key neurotransmitter that **activates brown fat** via **β3-adrenergic receptors** to initiate non-shivering thermogenesis. - While noradrenaline is the **trigger/stimulus**, the actual heat production occurs in brown adipose tissue. - Noradrenaline itself does not produce heat directly; it acts as the signal that activates the thermogenic machinery in BAT. *Thyroid hormone* - **Thyroid hormone** increases **basal metabolic rate** and can potentiate the thermogenic response by upregulating UCP1 expression in brown fat. - Its role is **permissive and long-term** rather than being the immediate effector of acute non-shivering thermogenesis. - It modulates overall cellular metabolism but is not the primary mechanism for rapid heat generation in cold exposure. *Muscle metabolism* - **Muscle contraction** during shivering generates heat through increased ATP hydrolysis, which is **shivering thermogenesis**. - **Non-shivering thermogenesis** specifically refers to heat production **without muscle contraction**, making muscle metabolism the mechanism for shivering, not non-shivering, thermogenesis.

Question 1

Primordial germ cells are derived from:

Accepted Answer

Yolk sac

Answer

Neural crest

Answer

Genital ridge

Answer

Somatopleuritic mesoderm

Question 2

Which of the following is NOT a branch of 1st part of maxillary artery?

Accepted Answer

Greater palatine artery

Answer

Accessory meningeal artery

Answer

Inferior alveolar artery

Answer

Middle meningeal artery

Question 3

What is the anatomical significance of the Rhinion in relation to the osseocartilaginous junction?

Accepted Answer

Rhinion

Answer

Nasion

Answer

Radix

Answer

Columella

Question 4

Which of the following structures is not derived from the ectoderm?

Accepted Answer

Eustachian tube

Answer

Brain

Answer

Retina

Answer

Lens

Question 5

Which vitamin is involved in one-carbon transfer reactions?

Accepted Answer

Folic acid

Answer

Pantothenic acid

Answer

Niacin

Answer

Thiamine

Question 6

Which amino acids are involved in the formation of purines?

Accepted Answer

Aspartate, glycine, glutamine

Answer

Aspartate, glycine

Answer

Aspartate, glutamate

Answer

Aspartic acid, glycine, uric acid

Question 7

When differentiated cells transform to form cells characteristic of other tissues, the process is called as -

Accepted Answer

Trans-differentiation

Answer

De-differentiation

Answer

Re-differentiation

Answer

Sub-differentiation

Question 8

Which type of carbohydrate is absorbed most efficiently from the gastrointestinal tract?

Accepted Answer

Monosaccharides

Answer

Disaccharides

Answer

Polysaccharides

Answer

5-carbon sugars

Question 9

What is the normal range of interstitial pressure?

Accepted Answer

-5 to 0 mmHg

Answer

-3 to 0 mmHg

Answer

0 to 5 mmHg

Answer

5 to 10 mmHg

Question 10

Nonshivering thermogenesis in adults is due to:

Accepted Answer

Brown fat between the shoulders

Answer

Muscle metabolism

Answer

Thyroid hormone

Answer

Noradrenaline

NEET-PG 2012

Anatomy

Biochemistry

Pathology

Physiology