Which of the following structures is not derived from the ectoderm?
Nutrient artery runs ?
Crural index is:
Unilateral lacrimal gland destruction may be caused by?
Which of the following extraocular muscle has the longest tendon?
After trauma, a person cannot move their eye outward beyond the midpoint. Which nerve is injured?
Most common site for medulloblastoma is-
Which of the following is not a neural plate inducer?
Identify the type of connective tissue present in the image.
Which nerve is primarily involved in cubital tunnel syndrome?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 81: Which of the following structures is not derived from the ectoderm?
- A. Brain
- B. Retina
- C. Eustachian tube (Correct Answer)
- D. Lens
Explanation: ***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.
Question 82: Nutrient artery runs ?
- A. Away from epiphysis (Correct Answer)
- B. Towards metaphysis
- C. None of the options
- D. Away from metaphysis
Explanation: ***Away from epiphysis*** - The **nutrient artery** runs away from the **dominant (faster-growing) epiphysis** towards the non-dominant end of the bone. - This follows the classic anatomical rule: **"To the elbow, from the knee"** - nutrient arteries point towards the elbow in upper limb bones and away from the knee in lower limb bones. - The **nutrient foramen** is directed obliquely away from the more actively growing end, established during bone development. - Examples: In the humerus, it runs towards the elbow (away from proximal epiphysis); in the femur, it runs away from the knee (away from distal epiphysis). *Towards metaphysis* - While the artery does course towards the metaphyseal region of the slower-growing end, this option is less anatomically precise. - The standard teaching emphasizes the relationship with the **dominant epiphysis** rather than the metaphysis. *Away from metaphysis* - This is **incorrect** - the nutrient artery actually runs **towards** the metaphysis of the non-dominant end. - It runs **away from** the dominant epiphysis, not away from the metaphysis. *None of the options* - This is incorrect as **"Away from epiphysis"** correctly describes the direction of the nutrient artery relative to the dominant growing end.
Question 83: 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 84: 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 85: 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 86: 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 87: 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 88: 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 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: Which nerve is primarily involved in cubital tunnel syndrome?
- A. Radial nerve
- B. Ulnar nerve (Correct Answer)
- C. Median nerve
- D. Axillary nerve
Explanation: Ulnar nerve - **Cubital tunnel syndrome** is a condition caused by compression of the **ulnar nerve** as it passes through the cubital tunnel at the medial epicondyle of the elbow. - Symptoms typically include numbness and tingling in the **little finger** and **half of the ring finger**, along with weakness of intrinsic hand muscles [2]. *Radial nerve* - The **radial nerve** is primarily involved in conditions like **radial tunnel syndrome** or radial nerve palsy (**wrist drop**), affecting primarily extensor muscles of the forearm and hand. - Its compression site is typically in the **radial tunnel** near the elbow, distinct from the cubital tunnel. *Median nerve* - The **median nerve** is involved in **carpal tunnel syndrome** at the wrist, causing numbness and tingling in the thumb, index, middle, and radial half of the ring finger [2]. - Compression around the elbow (e.g., pronator teres syndrome) can also affect the median nerve, but this is less common than cubital tunnel syndrome [1]. *Axillary nerve* - The **axillary nerve** is responsible for sensation over the deltoid region and motor function of the deltoid and teres minor muscles. - It is often injured with **shoulder dislocations** or fractures of the surgical neck of the humerus, unrelated to cubital tunnel syndrome.