Which structures are located anterior to the transverse sinus?
Anal valve is found in which part of anal canal?
After trauma, a person cannot move their eye outward beyond the midpoint. Which nerve is injured?
Most common site for medulloblastoma is-
Unilateral lacrimal gland destruction may be caused by?
Which of the following is not a neural plate inducer?
Which of the following extraocular muscle has the longest tendon?
Crural index is:
Identify the type of connective tissue present in the image.
Unable to consolidate long-term memory. Which lobe of the brain is involved?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 81: Which structures are located anterior to the transverse sinus?
- A. Right atrium
- B. Left atrium
- C. Right pulmonary artery
- D. Aorta (Correct Answer)
Explanation: ***Aorta*** - The **transverse sinus of the pericardium** is a passage within the pericardial cavity that separates the great arteries (aorta and pulmonary trunk) anteriorly from the atria and great veins posteriorly. - The **ascending aorta** and **pulmonary trunk** are both located anterior to the transverse sinus. - This anatomical relationship is clinically important during cardiac surgery, as the transverse sinus can be used to pass ligatures around the great vessels. *Right atrium* - The **right atrium** is located posterior to the transverse sinus. - It forms part of the posterior wall of the pericardial cavity and receives the superior and inferior venae cavae. - The transverse sinus separates the atria from the anteriorly positioned great arteries. *Left atrium* - The **left atrium** is also positioned posterior to the transverse sinus. - It forms the base of the heart and receives the pulmonary veins. - Like the right atrium, it lies behind the plane of the transverse sinus. *Right pulmonary artery* - The **right pulmonary artery** is a branch of the pulmonary trunk that passes to the right lung. - While the **pulmonary trunk** itself is anterior to the transverse sinus, the **right pulmonary artery** branch courses laterally and posteriorly, passing behind the ascending aorta and superior vena cava. - Therefore, the right pulmonary artery is NOT considered anterior to the transverse sinus in the same way the main great vessels (aorta and pulmonary trunk) are.
Question 82: Anal valve is found in which part of anal canal?
- A. Lower
- B. At anus
- C. Middle (Correct Answer)
- D. Upper
Explanation: ***Middle*** - The **anal valves** are crescentic folds located at the level of the **pectinate (dentate) line** in the middle portion of the anal canal. - They mark the inferior limit of the **anal columns** and form small recesses called **anal sinuses**. *Lower* - The lower part of the anal canal, below the pectinate line, is lined by **anoderm** and lacks anal valves. - This region is sensitive to pain due to somatic innervation. *At anus* - The anus refers to the external opening and perianal skin, which does not contain anal valves. - The anal canal transitions into the perianal skin at the anocutaneous line. *Upper* - The upper part of the anal canal, above the pectinate line, contains the **anal columns (columns of Morgagni)** but not the anal valves themselves, which are located at the base of these columns. - This region is lined by columnar epithelium and is relatively insensitive to pain.
Question 83: After trauma, a person cannot move their eye outward beyond the midpoint. Which nerve is injured?
- A. 3rd
- B. 4th
- C. 6th (Correct Answer)
- D. 2nd
Explanation: ***6th*** - The **abducens nerve (CN VI)** innervates the **lateral rectus muscle**, which is responsible for moving the eye **outward (abduction)** [1]. - Injury to the abducens nerve would result in an inability to move the eye laterally, causing an **esotropia** (eye turned inward at rest) [1]. *2nd* - The **optic nerve (CN II)** is responsible for **vision**, not eye movement [2]. - Damage to this nerve would cause **visual field defects** or **blindness** [3]. *3rd* - The **oculomotor nerve (CN III)** controls most extraocular muscles, including the **medial, superior, and inferior rectus** and **inferior oblique muscles**, as well as the **levator palpebrae superioris** and **pupillary constriction** [2]. - Injury to CN III would lead to a **down and out deviation of the eye**, **ptosis**, and a **dilated pupil** [2]. *4th* - The **trochlear nerve (CN IV)** innervates the **superior oblique muscle**, which primarily causes **intorsion** (rotation downward and inward) [1]. - Damage to this nerve results in **vertical diplopia**, especially when looking down and in, and a characteristic **head tilt** to compensate [3].
Question 84: Most common site for medulloblastoma is-
- A. Cerebellum (Correct Answer)
- B. Pituitary
- C. Cerebrum
- D. Pineal gland
Explanation: ***Cerebellum*** - **Medulloblastoma** is a highly malignant primary brain tumor that characteristically arises in the **cerebellum** [1]. - It is the most common malignant brain tumor in children, typically originating from the **roof of the fourth ventricle**. *Pituitary* - The **pituitary gland** is mostly associated with **adenomas**, which are benign tumors arising from anterior pituitary cells. - Tumors like **craniopharyngiomas** can also be found in the sellar region, but medulloblastomas do not originate here. *Cerebrum* - The **cerebrum** is the most common site for **gliomas** (e.g., glioblastoma multiforme) and metastatic tumors in adults. - Medulloblastoma specifically originates from primitive neuroectodermal cells in the posterior fossa [1]. *Pineal gland* - The **pineal gland** is associated with **pinealomas** (e.g., pineoblastoma, pineocytoma) and **germinomas** [2]. - These are distinct from medulloblastomas in their cellular origin and typical anatomical location.
Question 85: Unilateral lacrimal gland destruction may be caused by?
- A. Fracture of roof of orbit (Correct Answer)
- B. Inferior orbital fissure fracture
- C. Fracture of lateral wall
- D. Fracture of sphenoid
Explanation: ***Fracture of roof of orbit*** - The **lacrimal gland** is situated in the **lacrimal fossa** on the anterior-lateral part of the **orbital roof**. A fracture in this specific area can directly damage the gland. - Trauma to the **orbital roof** can lead to laceration, avulsion, or compression of the lacrimal gland, resulting in its destruction and impairing tear production. *Inferior orbital fissure fracture* - The **inferior orbital fissure** transmits nerves and vessels to the orbit but is located inferior to the lacrimal gland, making direct injury unlikely. - Fractures here are more associated with **infraorbital nerve damage** or disruption of orbital contents into the maxillary sinus, not lacrimal gland destruction. *Fracture of lateral wall* - The **lateral wall of the orbit** forms the outer boundary and protects structures deeper within the orbit, but the lacrimal gland is situated superiorly and anteriorly. - While significant trauma to the lateral wall can impact orbital contents, it is less likely to directly cause unilateral lacrimal gland destruction compared to a direct roof fracture. *Fracture of sphenoid* - Fractures of the **sphenoid bone** are typically more posterior and central, affecting structures like the **optic canal** or **cavernous sinus**. - While it can indirectly affect orbital function, it is not a direct cause of isolated lacrimal gland destruction due to its anatomical location.
Question 86: Which of the following is not a neural plate inducer?
- A. FGF upregulation
- B. Prechordal mesoderm
- C. High BMP (Correct Answer)
- D. Notochord appearance
Explanation: High BMP - **Bone Morphogenetic Proteins (BMPs)** are primarily involved in promoting epidermal differentiation in the ectoderm, and actively **inhibiting neural differentiation**. - Therefore, high levels of BMP would **prevent neural plate formation**, rather than induce it. *FGF upregulation* - **Fibroblast Growth Factors (FGFs)** are crucial in the early development of the nervous system. - They play a key role in **inducing neural plate formation** and maintaining its identity. *Prechordal mesoderm* - The **prechordal mesoderm**, located anterior to the notochord, is an important signalling center during early embryonic development. - It contributes to the **induction of the forebrain** and plays a role in patterning the anterior neural plate. *Notochord appearance* - The **notochord**, a transient rod-like structure, is a primary inducer of the neural plate. - It secretes factors like **Sonic Hedgehog (Shh)** which induce the overlying ectoderm to differentiate into neuroectoderm, forming the neural plate.
Question 87: Which of the following extraocular muscle has the longest tendon?
- A. Medial rectus
- B. Superior rectus
- C. Superior oblique (Correct Answer)
- D. Inferior oblique
Explanation: ***Superior oblique*** - The superior oblique muscle has the **longest tendon** and overall length of all extraocular muscles because it passes through the **trochlea**, a cartilaginous pulley. - Its long course allows it to have a complex action, primarily **intorsion, depression, and abduction** of the eye [1]. *Superior rectus* - The superior rectus is one of the **straight muscles** (recti) and is not the longest. - Its primary actions are **elevation, adduction, and intorsion** of the eyeball [1]. *Medial rectus* - The medial rectus is another **straight muscle** and is generally considered the **strongest** but not the longest extraocular muscle. - Its main action is **adduction** (moving the eye inward) [1]. *Inferior oblique* - The inferior oblique is the **shortest** of all the extraocular muscles. - Its primary actions are **extorsion, elevation, and abduction** of the eyeball [1].
Question 88: Crural index is:
- A. Length of tibia/femur x 100 (Correct Answer)
- B. Length of radius/humerus x 100
- C. Length of fibula/tibia x 100
- D. Length of radius/ulna x 100
Explanation: ***Length of tibia/femur x 100*** - The **crural index** is a measure used in physical anthropology and comparative anatomy to describe the proportion of the lower leg to the thigh. - It is calculated by dividing the **length of the tibia** (lower leg bone) by the **length of the femur** (thigh bone) and multiplying by 100 to express it as a percentage. *Length of radius/humerus x 100* - This formula describes the **brachial index**, which measures the proportion of the forearm to the upper arm. - It does not represent the crural index, which refers specifically to the **lower limb**. *Length of fibula/tibia x 100* - This ratio compares the two bones within the lower leg but is not the definition of the **crural index**. - The crural index focuses on the relative length of the lower leg to the entire thigh, reflecting overall **limb proportions**. *Length of radius/ulna x 100* - This ratio compares the lengths of the two bones in the forearm and does not correspond to the **crural index**. - The crural index involves the **tibia** and **femur**, which are bones of the lower limb.
Question 89: Identify the type of connective tissue present in the image.
- A. Loose and irregular
- B. Specialized
- C. Dense irregular (Correct Answer)
- D. Dense regular
Explanation: ***Dense irregular*** - The image shows **densely packed collagen fibers** arranged in an **irregular, haphazard fashion**, characteristic of dense irregular connective tissue. - This type of tissue provides **strength** and resistance to stress from multiple directions, found in the **dermis of the skin** and organ capsules. *Loose and irregular* - **Loose connective tissue** would show more ground substance and fewer, loosely arranged fibers, whereas this image displays high fiber density. - While it is "irregular" in fiber arrangement, the density of fibers rules out the "loose" classification. *Specialized* - **Specialized connective tissues** include cartilage, bone, blood, and adipose tissue, which have distinct cellular and extracellular matrix components not seen here. - This tissue lacks the specific cellular and matrix characteristics that would classify it as specialized (e.g., chondrocytes in lacunae, osteocytes, blood cells). *Dense regular* - **Dense regular connective tissue** features collagen fibers arranged in parallel bundles, providing strength in one direction. - Examples include **tendons and ligaments**, which are structurally organized in an orderly, aligned manner, unlike the displayed irregular arrangement.
Question 90: Unable to consolidate long-term memory. Which lobe of the brain is involved?
- A. Frontal
- B. Parietal
- C. Temporal (Correct Answer)
- D. Occipital
Explanation: ***Temporal*** - The **temporal lobe**, particularly the **hippocampus** within it, is critically involved in the formation and consolidation of new long-term memories [1]. - Damage to the temporal lobe can result in **anterograde amnesia**, the inability to form new memories after the injury [1]. *Frontal* - The **frontal lobe** is primarily responsible for executive functions, **planning**, decision-making, and working memory [1]. - While it contributes to memory retrieval and strategic memory processes, it is not the primary site for the consolidation of long-term memories. *Parietal* - The **parietal lobe** is involved in processing **sensory information**, spatial awareness, and navigation. - It plays a role in attention and short-term memory, but not in the consolidation of long-term memory. *Occipital* - The **occipital lobe** is dedicated to **visual processing** and interpretation of visual information. - It has no direct primary role in the consolidation of long-term memories.