Blood tissue barrier in testis is formed by?
Which nucleus is primarily involved in the Papez circuit?
Which thalamic nuclei can produce basal ganglia symptoms?
Which of the following is a cerebellar nucleus?
What is the approximate number of cones in the human retina?
What is the approximate length of the tibia in centimeters for an average adult?
What anatomical structure is formed after the obliteration of the umbilical vein?
T cells in lymph node are present in:
In current medical practice, cephalic index is primarily used for
Which is the earliest secondary ossification center to develop chronologically?
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 71: Blood tissue barrier in testis is formed by?
- A. Basal lamina & interstitial cells
- B. Basal lamina & spermatogonia
- C. Basal lamina & leydig cells
- D. Adjacent Sertoli cells with basal lamina (Correct Answer)
Explanation: ***Adjacent Sertoli cells with basal lamina*** - The **blood-testis barrier** is primarily formed by **tight junctions** between adjacent **Sertoli cells**, which divide the seminiferous epithelium into basal and adluminal compartments [1]. - The **basal lamina** of the seminiferous tubule also contributes to this barrier, regulating the passage of substances from the interstitial fluid to the basal compartment [1]. *Basal lamina & interstitial cells* - While the **basal lamina** is part of the barrier, **interstitial cells (Leydig cells)** are located outside the seminiferous tubules and are primarily involved in **testosterone production**, not barrier formation [1]. - **Interstitial cells** are part of the connective tissue between the tubules and do not form tight junctions that would restrict molecular movement into the seminiferous epithelium. *Basal lamina & spermatogonia* - **Spermatogonia** are germ cells located in the **basal compartment** of the seminiferous tubule, *beneath* the Sertoli cell tight junctions [1]. - They are able to cross the barrier as they differentiate and move into the adluminal compartment, but they do not form the barrier itself. *Basal lamina & leydig cells* - As mentioned previously, **Leydig cells** (interstitial cells) are responsible for **androgen synthesis** and are located outside the seminiferous tubule [2]. - They do not form components of the physical blood-testis barrier.
Question 72: Which nucleus is primarily involved in the Papez circuit?
- A. Pulvinar nucleus
- B. Intralaminar nucleus
- C. Anterior nucleus of the thalamus (Correct Answer)
- D. Ventral posterolateral (VPL) nucleus
Explanation: ***Anterior nucleus of the thalamus*** - The **anterior nucleus of the thalamus** is a key relay station in the Papez circuit [1], receiving input from the mamillary bodies and projecting to the cingulate gyrus. - This circuit is crucial for **memory formation** [2] and emotional processing. *Pulvinar nucleus* - The pulvinar nucleus is primarily involved in **visual processing**, attention, and eye movements. - It does not form a direct part of the classic Papez circuit for emotion and memory. *Intralaminar nucleus* - The intralaminar nuclei are involved in **arousal**, attention, and pain perception, with widespread projections to the cerebral cortex [1]. - They are not considered a primary component of the Papez circuit. *Ventral posterolateral (VPL) nucleus* - The VPL nucleus is a major **somatosensory relay** in the thalamus, transmitting touch, proprioception, and vibration information from the body to the cortex. - It has no direct role in the Papez circuit or limbic functions.
Question 73: Which thalamic nuclei can produce basal ganglia symptoms?
- A. Lateral dorsal
- B. Pulvinar
- C. Ventral anterior (Correct Answer)
- D. Intralaminar
Explanation: ***Ventral anterior*** - The **ventral anterior (VA)** and **ventral lateral (VL)** nuclei of the thalamus receive significant input from the **basal ganglia** and project to the motor cortex [1]. - Dysfunction in these nuclei can disrupt the basal ganglia's influence on motor control, leading to symptoms like **dyskinesia** or **rigidity** [1]. *Lateral dorsal* - The **lateral dorsal nucleus** is primarily involved in **limbic system** functions and episodic memory. - It does not have direct nor significant connections with the basal ganglia motor circuits that would produce typical basal ganglia symptoms. *Pulvinar* - The **pulvinar** is the largest thalamic nucleus, primarily involved in **visual processing**, attention, and eye movements. - While it has extensive cortical connections, it is not directly involved in the motor circuits of the basal ganglia. *Intralaminar* - The **intralaminar nuclei** (e.g., centromedian and parafascicular) receive input from the basal ganglia but primarily project diffusely to the cerebral cortex and are involved in **arousal** and consciousness [2]. - While they modulate cortical activity, their dysfunction typically wouldn't produce the classic motor symptoms associated with basal ganglia disorders.
Question 74: Which of the following is a cerebellar nucleus?
- A. Putamen
- B. Caudate nucleus
- C. Subthalamic nucleus
- D. Fastigial nucleus (Correct Answer)
Explanation: ***Fastigial nucleus*** - The **fastigial nucleus** is one of the four principal deep cerebellar nuclei, involved in regulating **balance** and **posture** [2]. - The deep cerebellar nuclei are crucial for the cerebellum's output, relaying processed information to other brain regions [2]. *Caudate nucleus* - The **caudate nucleus** is part of the **basal ganglia**, a group of subcortical nuclei in the forebrain [1]. - It plays a significant role in **motor control**, learning, memory, and reward processing. *Subthalamic nucleus* - The **subthalamic nucleus** is a small nucleus located in the **diencephalon**, below the thalamus and above the substantia nigra [1]. - It is also part of the **basal ganglia system** and is critical for modulating motor control [1]. *Putamen* - The **putamen** is another structure belonging to the **basal ganglia**, located in the forebrain [1]. - It is primarily involved in regulating various types of **motor behavior** and learning.
Question 75: What is the approximate number of cones in the human retina?
- A. Approximately 3-5 million cones (Correct Answer)
- B. Approximately 25-50 million cones
- C. Approximately 50-100 million cones
- D. Approximately 10-20 million cones
Explanation: Approximately 3-5 million cones - The human retina contains roughly **4.5 million cones**, concentrated in the **fovea**, which is responsible for **high-acuity vision** and color perception [1]. - Cones are light-sensitive cells that detect **fine details** and are essential for vision in **bright light conditions** [1]. *Approximately 10-20 million cones* - This range is significantly higher than the actual number of cones found in the human retina. - While there are millions of photoreceptors, the *majority are rods*, not cones [1]. *Approximately 25-50 million cones* - This figure vastly *overestimates* the number of cones in the human eye. - The total number of photoreceptor cells (rods and cones combined) in the retina typically ranges from **100-125 million** [1]. *Approximately 50-100 million cones* - This range is incorrect as it refers more closely to the *total number of rods* in the human retina, which is about **90-120 million** [1]. - Cones constitute a much smaller proportion of the total photoreceptor population [1].
Question 76: What is the approximate length of the tibia in centimeters for an average adult?
- A. 30 cm
- B. 35 cm (Correct Answer)
- C. 40 cm
- D. 45 cm
Explanation: ***35 cm*** - The **tibia**, or shin bone, is the larger of the two bones in the lower leg and plays a crucial role in supporting body weight. - Its average length in adults is approximately **36-38 cm**, with **35 cm** being well within the normal range for an average adult. - Females typically have tibiae measuring **36-37 cm**, while males average **38-39 cm**. *30 cm* - A length of **30 cm** would be unusually short for an adult tibia, falling well below the normal range for average adults. - Such a short length might be associated with specific medical conditions or skeletal dysplasias. *40 cm* - A length of **40 cm** would be at the upper end or slightly above the typical average for an adult tibia. - This measurement might be seen in taller individuals, but it exceeds the average for most adults. *45 cm* - A length of **45 cm** would be comparatively long for an average adult tibia. - This measurement is significantly above average and would only be seen in very tall individuals.
Question 77: What anatomical structure is formed after the obliteration of the umbilical vein?
- A. Ligamentum venosum
- B. Ligamentum arteriosum
- C. Medial umbilical ligament
- D. Round ligament of the liver (ligamentum teres) (Correct Answer)
Explanation: ***Round ligament of the liver (ligamentum teres)*** - The **umbilical vein** carries oxygenated blood from the placenta to the fetus during development [1]. - After birth, the umbilical vein obliterates and forms the **round ligament of the liver**, also known as the **ligamentum teres hepatis**. *Ligamentum venosum* - This structure is the obliterated remnant of the **ductus venosus**, which shunted blood from the umbilical vein to the inferior vena cava, bypassing the fetal liver [1]. - It is located in a fissure on the posterior surface of the liver, separate from the round ligament. *Ligamentum arteriosum* - This ligament is the remnant of the **ductus arteriosus**, a fetal blood vessel connecting the pulmonary artery to the aorta. - Its obliteration allows blood to flow through the lungs after birth. *Medial umbilical ligament* - This ligament is formed from the obliterated **umbilical arteries**, which carry deoxygenated blood from the fetus back to the placenta. - There are two medial umbilical ligaments, one from each umbilical artery.
Question 78: T cells in lymph node are present in:
- A. Paracortical area (Correct Answer)
- B. Mantle layer
- C. Medullary cords
- D. Cortical follicles
Explanation: ***Paracortical area*** - The **paracortical area** contains a high concentration of **T cells**, particularly activated T cells in response to antigenic stimulation [1]. - It plays a crucial role in **immune responses**, bridging the cortex and medulla of the lymph node [1]. *Mantle layer* - The **mantle layer** surrounds the follicles and primarily consists of **B cells**, not T cells. - It is involved in the initial immune response but does not contain a significant number of T lymphocytes. *Medullary cords* - **Medullary cords** mainly contain **plasma cells** and macrophages, with very few T cells present. - Their primary function is the secretion of antibodies rather than T cell activation or response. *Cortical follicles* - **Cortical follicles** are primarily sites for **B cell activation and proliferation**. - While they may have some T cells at their periphery, the majority of T cells are located in the paracortical area.
Question 79: In current medical practice, cephalic index is primarily used for
- A. Evaluation of skull deformities
- B. Assessment of craniosynostosis (Correct Answer)
- C. Clinical documentation of head shape
- D. Neurosurgical planning
Explanation: ***Assessment of craniosynostosis*** - The **cephalic index** (ratio of maximum head width to maximum head length × 100) provides a quantitative measure of head shape that can help characterize types of **craniosynostosis** [1]. - It helps differentiate patterns: **scaphocephaly** (dolichocephaly, CI <76), **brachycephaly** (CI >81), and **normocephaly** (CI 76-81). - In current practice, while **CT imaging** is the gold standard for diagnosing craniosynostosis, the cephalic index remains a useful **anthropometric measurement** in clinical assessment and documentation of cranial deformities. - It is particularly helpful in distinguishing **positional plagiocephaly** from **true craniosynostosis** when combined with clinical examination. *Evaluation of skull deformities* - The cephalic index can be used to evaluate various skull deformities, but this is too broad a description. - Its most specific clinical utility is in the context of **craniosynostosis assessment** where quantitative head shape measurements are diagnostically relevant [1]. - Many other skull deformities are assessed through direct clinical observation or specialized imaging rather than anthropometric indices. *Clinical documentation of head shape* - While the cephalic index does provide objective documentation of head shape, this describes its function rather than its primary **clinical indication**. - Documentation alone lacks the diagnostic and therapeutic implications that make cephalic index measurement clinically valuable. - In modern practice, simple descriptive terms (dolichocephaly, brachycephaly) are often used without calculating the precise index. *Neurosurgical planning* - Neurosurgical planning for craniosynostosis repair relies primarily on **CT scans with 3D reconstruction** to visualize suture fusion patterns, bone thickness, and intracranial anatomy. - The cephalic index provides diagnostic context but does not directly guide surgical technique, approach, or reconstruction planning. - Surgical decisions are based on imaging findings, age of the patient, and specific suture involvement rather than the numerical cephalic index value.
Question 80: Which is the earliest secondary ossification center to develop chronologically?
- A. Lower end of femur (Correct Answer)
- B. Upper end of humerus
- C. Lower end of fibula
- D. Upper end of tibia
Explanation: ***Lower end of femur*** - The **distal femoral epiphysis** is typically the first secondary ossification center to appear, often present at birth or shortly before [1]. - Its presence at birth is an indicator of **fetal maturity**, making it a key developmental landmark [1]. *Upper end of humerus* - The **proximal humeral epiphysis** typically ossifies around 6 months of age, significantly later than the distal femur. - This center contributes to the growth of the humeral head and greater tubercle. *Lower end of fibula* - The **distal fibular epiphysis** appears around the first year of life, after both the distal femur and proximal humerus. - It forms part of the ankle joint and contributes to its stability. *Upper end of tibia* - The **proximal tibial epiphysis** typically ossifies around 6-12 months of age, well after the distal femur. - This center is crucial for the growth of the upper tibia and knee joint development.