Embryo gets implanted at what stage of development?
Most common site for Cystic Hygroma is -
Transplanted kidney is relocated to which region in the recipient's body?
Trigone of urinary bladder develops from:
Foot drop occurs due to the involvement of:
Submucosal plexus is -
Which of the following extraocular muscles is not supplied by oculomotor nerve?
Extensor carpi radialis longus is
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 161: Embryo gets implanted at what stage of development?
- A. Two cell stage
- B. Four cell stage
- C. Morula
- D. Blastocyst (Correct Answer)
Explanation: Blastocyst - Implantation into the uterine wall occurs when the embryo has developed into a blastocyst, typically around day 6 post-fertilization [1]. - The blastocyst consists of an inner cell mass (which forms the embryo) and an outer layer called the trophoblast (which contributes to the placenta) [1]. Two cell stage - This stage occurs very early in development, usually within the first 24-30 hours after fertilization [1]. - At this point, the embryo is still in the fallopian tube and has not yet reached the uterus for implantation [1]. Four cell stage - The four-cell stage is also an early cleavage stage, occurring around 2 days post-fertilization [1]. - Like the two-cell stage, the embryo is still in transport through the fallopian tube and is not ready for implantation [1]. Morula - The morula is a solid ball of cells formed by cleavage, typically around day 3-4 post-fertilization [1]. - While it has moved closer to the uterus, it has not yet formed the distinct inner cell mass and trophoblast necessary for successful implantation [1].
Question 162: Most common site for Cystic Hygroma is -
- A. Lower third of neck (Correct Answer)
- B. Overlying the parotid gland
- C. Along the Zygomatic Prominence
- D. Post auricular
Explanation: ***Lower third of neck*** - **Cystic hygromas** (also known as **lymphatic malformations**) most commonly occur in the **posterior triangle of the neck**, which is located in the lower lateral aspect of the neck [1]. - Approximately **75-80%** of cystic hygromas are found in the neck region, with the **posterior triangle** being the predominant site. - The **posterior jugular lymph sac** fails to connect properly with the venous system during embryonic development, leading to these cystic malformations in this characteristic location [1]. - The posterior triangle encompasses the lower lateral neck, making "lower third of neck" an acceptable description of this most common site. *Overlying the parotid gland* - While lymphatic malformations can occur in the parotid region, this represents only about **10-15%** of cases. - This is a less common site compared to the posterior triangle of the neck. - Lesions in this area might raise concern for other parotid pathologies like **pleomorphic adenoma** or **hemangioma**. *Along the Zygomatic Prominence* - This is an unusual location for a cystic hygroma, as the lymphatic drainage and embryonic development in this area are not typically associated with these malformations. - Lesions here might suggest different developmental or neoplastic etiologies such as **dermoid cysts** or **vascular malformations**. *Post auricular* - The post-auricular region is not a common site for cystic hygromas. - Swelling in this area could be due to other conditions like **mastoiditis**, **lymphadenopathy**, or **sebaceous cysts**.
Question 163: Transplanted kidney is relocated to which region in the recipient's body?
- A. Lumbar region
- B. Epigastrium
- C. Beside the dysfunctional kidney
- D. Retroperitoneal region (Correct Answer)
Explanation: ***Retroperitoneal region*** - The transplanted kidney is typically placed in the **iliac fossa** within the **retroperitoneal space** of the recipient [2]. - This location provides adequate space and a convenient site for connecting the transplant's renal artery and vein to the recipient's **iliac vessels**, and the ureter to the bladder [2]. *Lumbar region* - The native kidneys are located in the lumbar region, but a transplanted kidney is not usually placed there due to the complexity of vascular anastomoses and limited access [1]. - Positioning in the lumbar region would require more extensive surgical dissection and potentially longer vascular connections. *Epigastrium* - The epigastrium is the upper central part of the abdomen, above the navel. - This location is not suitable for kidney transplantation due to anatomical constraints and the lack of readily accessible large blood vessels for connection. *Beside the dysfunctional Kidney* - The dysfunctional native kidneys are usually left in place unless they are causing severe complications like uncontrolled hypertension or infection. - Placing the transplanted kidney directly beside the native dysfunctional kidney is not the standard procedure due to space limitations and to avoid operating near potentially diseased native organs.
Question 164: Trigone of urinary bladder develops from:
- A. Ectoderm
- B. Mesoderm (Correct Answer)
- C. None of the options
- D. Endoderm of urachus
Explanation: ***Mesoderm*** - The **trigone** of the urinary bladder develops from the **distal ends of the mesonephric (Wolffian) ducts**, which are **mesodermal in origin**. - These ducts are **absorbed into the posterior wall of the bladder**, forming the smooth triangular area between the two ureteric orifices and the internal urethral orifice [1]. - Although the epithelium of the trigone is later **replaced by endodermal epithelium** from the urogenital sinus, the **structural origin remains mesodermal**. - This is a classic example of **epithelial metaplasia** where endodermal epithelium replaces mesodermal tissue. *Endoderm of urachus* - The **urachus** is the fibrous remnant of the allantois that connects the apex of the bladder to the umbilicus. - It forms the **median umbilical ligament** in adults and does **not contribute to the trigone**. - The **urogenital sinus** (endodermal) forms the majority of the bladder body, but not the trigone. *Ectoderm* - The **ectoderm** forms the nervous system, epidermis, and sensory epithelia. - It does **not contribute** to the development of the urinary bladder or its trigone. - The urinary system is derived from **mesoderm** (kidneys, ureters, trigone) and **endoderm** (bladder body, urethra). *None of the options* - This is incorrect because **mesoderm** is the correct embryological origin of the trigone. - The mesonephric ducts that form the trigone are definitively mesodermal structures.
Question 165: Foot drop occurs due to the involvement of:
- A. Obturator nerve
- B. Sciatic nerve
- C. Direct injury to the dorsiflexors
- D. Common peroneal nerve palsy (Correct Answer)
Explanation: ***Common peroneal nerve palsy*** - The **common peroneal nerve** (also known as the common fibular nerve) innervates the muscles responsible for **dorsiflexion** and eversion of the foot (tibialis anterior, extensor hallucis longus, extensor digitorum longus, peroneus longus and brevis). - Damage to this nerve leads to weakness or paralysis of these muscles, resulting in **foot drop**, which is the most common neurological cause. - The nerve is vulnerable at the **neck of the fibula** where it is superficial and can be compressed or injured. *Sciatic nerve* - The **sciatic nerve** divides into the tibial and common peroneal nerves. - Proximal sciatic nerve injury can cause foot drop, but it would also cause additional deficits including hamstring weakness, loss of ankle plantarflexion, and sensory loss over a wider distribution. - Isolated foot drop typically indicates **common peroneal nerve** injury, not sciatic nerve injury. *Direct injury to the dorsiflexors* - Direct trauma to the **dorsiflexor muscles** (tibialis anterior, extensor hallucis longus, extensor digitorum longus) can mechanically impair dorsiflexion. - However, the term "foot drop" typically refers to **neurological causes** rather than direct muscle injury, making common peroneal nerve palsy the more specific answer. *Obturator nerve* - The **obturator nerve** innervates the **adductor muscles of the thigh** (adductor longus, adductor brevis, adductor magnus, gracilis). - It does not innervate any muscles responsible for dorsiflexion of the foot and therefore **cannot cause foot drop**.
Question 166: Submucosal plexus is -
- A. Myenteric plexus
- B. Tympanic plexus
- C. Meissner's plexus (Correct Answer)
- D. Auerbach's plexus
Explanation: ***Meissner's plexus*** - The **submucosal plexus** is also known as **Meissner's plexus**, located in the submucosal layer of the **gastrointestinal tract** [1]. - It primarily controls local **secretions**, **absorption**, and **blood flow** within the gut [2]. *Myenteric plexus* - The **myenteric plexus** is also known as **Auerbach's plexus**, located between the longitudinal and circular muscle layers of the **gastrointestinal tract** [1]. - It primarily controls **gastrointestinal motility**, not local secretions [1]. *Tympanic plexus* - The **tympanic plexus** is a network of nerves in the **middle ear** that provides sensory innervation to the tympanic cavity. - It is unrelated to the gastrointestinal tract or its intrinsic nervous system. *Auerbach's plexus* - **Auerbach's plexus** is another name for the **myenteric plexus**, which is located between the muscle layers [1]. - It is responsible for gut motility and distinct from the submucosal plexus.
Question 167: Which of the following extraocular muscles is not supplied by oculomotor nerve?
- A. Inferior oblique
- B. Medial rectus
- C. Inferior rectus
- D. Lateral rectus (Correct Answer)
Explanation: ***Lateral rectus*** - The **lateral rectus muscle** is innervated by the **abducens nerve (CN VI)**, not the oculomotor nerve (CN III). [1] - Its primary action is **abduction** of the eye, moving it laterally away from the midline. [1] *Inferior oblique* - The **inferior oblique muscle** is innervated by the **oculomotor nerve (CN III)**. [1] - Its actions include **extorsion**, elevation, and abduction of the eye. [1] *Medial rectus* - The **medial rectus muscle** is innervated by the **oculomotor nerve (CN III)**. [1] - Its primary action is **adduction** of the eye, moving it medially towards the midline. [1] *Inferior rectus* - The **inferior rectus muscle** is innervated by the **oculomotor nerve (CN III)**. [1] - Its actions include **depression**, extorsion, and adduction of the eye. [1]
Question 168: Extensor carpi radialis longus is
- A. Extensor and radial deviator of the wrist (Correct Answer)
- B. Weak extensor of the wrist
- C. Extensor and ulnar deviator of the wrist
- D. Injured in Posterior interosseous nerve injury
Explanation: ***Extensor and radial deviator of the wrist*** - The **extensor carpi radialis longus (ECRL)** is one of the primary muscles responsible for **extension of the wrist**. [1] - Due to its anatomical position on the radial side of the forearm, it also contributes significantly to **radial deviation** (abduction) of the wrist. [1] *Weak extensor of the wrist* - While it is an extensor, the ECRL is considered a **strong extensor** of the wrist, especially when acting with other extensors like the Extensor Carpi Radialis Brevis (ECRB). [1] - Its strength is crucial for tasks requiring **grip and wrist stabilization**. *Extensor and ulnar deviator of the wrist* - The ECRL performs wrist extension but causes **radial deviation**, not ulnar deviation. [1] - **Ulnar deviation** is primarily performed by the **extensor carpi ulnaris** and **flexor carpi ulnaris**. *Injured in Posterior interosseous nerve injury* - The ECRL is innervated by the **radial nerve** **before** it divides into the superficial and deep (posterior interosseous) branches. [2] - Therefore, ECRL function is typically **spared in isolated posterior interosseous nerve injuries**, which mainly affect muscles in the deep compartment of the posterior forearm. [2]