Anatomy
5 questionsWhich of the following is a traction epiphysis ?
Cricoid cartilage lies at which vertebral level?
All are derived from ectoderm except for which of the following?
All are lateral branches of the abdominal aorta, EXCEPT which of the following?
Which muscle stabilizes the clavicle during movement of the shoulder?
NEET-PG 2012 - Anatomy NEET-PG Practice Questions and MCQs
Question 201: Which of the following is a traction epiphysis ?
- A. Tibial condyles
- B. Head of femur
- C. Trochanter of femur
- D. Coracoid process of scapula (Correct Answer)
Explanation: ***Coracoid process of scapula*** - A **traction epiphysis** (also called atavistic epiphysis) serves as an attachment site for muscles and tendons, transferring muscle force to the bone without bearing significant weight or forming articular surfaces. - The **coracoid process** is a classic example, anchoring the **pectoralis minor, coracobrachialis, and short head of biceps brachii**, as well as important ligaments (coracoclavicular and coracoacromial). - It develops from a separate ossification center purely for muscle and ligament attachment, not for articulation or weight-bearing. *Tibial condyles* - The **tibial condyles** are **pressure epiphyses** (articular epiphyses) that form the superior articular surface of the tibia. - They articulate with the femoral condyles to form the knee joint and bear significant weight during standing and movement. - Their primary function is joint formation and contribution to longitudinal bone growth. *Trochanter of femur* - The **greater and lesser trochanters** are large bony prominences that serve as muscle attachment sites, but they are better classified as **apophyses** rather than true traction epiphyses. - An **apophysis** is a secondary ossification center that does not contribute to longitudinal bone growth and serves primarily for muscle attachment. - While functionally similar to traction epiphyses, the term "traction epiphysis" is more specifically applied to structures like the coracoid process, tibial tuberosity, and calcaneal tuberosity. *Head of femur* - The **head of femur** is a classic **pressure epiphysis** that articulates with the acetabulum to form the hip joint. - It bears significant body weight and contributes to the longitudinal growth of the femur. - Its primary functions are joint formation and weight transmission, not muscle attachment.
Question 202: Cricoid cartilage lies at which vertebral level?
- A. C3
- B. C6 (Correct Answer)
- C. T1
- D. T4
Explanation: **C6** - The **cricoid cartilage** is an important anatomical landmark, as it signifies the transition from the **laryngopharynx** to the **esophagus** and the start of the **trachea**. - Its location at **C6 vertebral level** is significant for procedures like tracheostomy and in identifying the narrowest part of the adult airway. *C3* - The C3 vertebral level is typically associated with the **hyoid bone**, which is superior to the cricoid cartilage. - The **epiglottis** and the superior aspect of the larynx are more commonly found at C3-C4. *T1* - The T1 vertebral level is in the **thoracic spine**, well below the neck, and is associated with the **apex of the lung** and the **first rib**. - The airway structures at this level are primarily the **trachea** as it enters the thorax. *T4* - The T4 vertebral level is significant as it marks the approximate location of the **carina**, where the trachea bifurcates into the main bronchi. - This level is much lower than the larynx and cricoid cartilage.
Question 203: All are derived from ectoderm except for which of the following?
- A. Hair follicles
- B. Nails
- C. Lens of the eye
- D. Adrenal cortex (Correct Answer)
Explanation: ***Adrenal cortex*** - The adrenal cortex is derived from the **intermediate mesoderm**, specifically from the cells lining the posterior abdominal wall. The cells migrate to develop into the adrenal cortex. - It produces various steroid hormones, including **aldosterone**, **cortisol**, and **androgens**, which regulate diverse bodily functions. *Lens of the eye* - The lens of the eye is derived from the **surface ectoderm**. It forms from an invagination of the surface ectoderm called the lens placode. - Its primary function is to **focus light** onto the retina. *Hair follicles* - Hair follicles develop from the **surface ectoderm** [1]; they are invaginations of the epidermis that extend into the dermis. - They produce hair, which provides **insulation** and **protection** [1]. *Nails* - Nails are also derivatives of the **surface ectoderm**, forming thickened plates on the dorsal surface of the distal phalanges. - They provide **protection** to the fingertips and aid in grasping objects.
Question 204: All are lateral branches of the abdominal aorta, EXCEPT which of the following?
- A. Right testicular artery
- B. Left renal artery
- C. Middle suprarenal artery
- D. Celiac trunk (Correct Answer)
Explanation: ***Celiac trunk*** - The **celiac trunk** is an anterior branch of the abdominal aorta, supplying the foregut derivatives. - It arises from the ventral aspect of the aorta, distinguishing it from lateral branches. *Right testicular artery* - The **testicular arteries** (gonadal arteries) are paired lateral branches of the abdominal aorta. - They arise inferior to the renal arteries and descend to supply the testes in males. *Left renal artery* - The **renal arteries** [1] [3] are large paired lateral branches of the abdominal aorta. - They supply the kidneys [2] and typically arise just inferior to the superior mesenteric artery. *Middle suprarenal artery* - The **middle suprarenal arteries** are paired lateral branches, typically arising directly from the abdominal aorta. - They supply the suprarenal (adrenal) glands [2].
Question 205: Which muscle stabilizes the clavicle during movement of the shoulder?
- A. Pectoralis major
- B. Latissimus dorsi
- C. Subclavius (Correct Answer)
- D. Serratus anterior
Explanation: ***Subclavius*** - The **subclavius muscle** originates from the first rib and inserts into the inferior surface of the clavicle, acting to **depress the clavicle** and prevent its displacement, thus enhancing shoulder stability during movement. - It plays a crucial role in protecting the underlying **neurovascular structures** (brachial plexus and subclavian vessels) from external trauma to the shoulder. *Pectoralis major* - This large, fan-shaped muscle primarily functions in **adduction, medial rotation, and flexion of the humerus** at the shoulder joint [1]. - It does not directly stabilize the clavicle but rather acts on the arm. *Latissimus dorsi* - The **latissimus dorsi** is a broad muscle of the back responsible for **extension, adduction, and internal rotation of the humerus** [1]. - Its actions are mainly on the humerus and it does not directly stabilize the clavicle. *Serratus anterior* - The **serratus anterior** muscle primarily **protracts and rotates the scapula**, keeping it pressed against the thoracic wall. - While it's essential for **scapular stability** and overhead arm movements, it does not directly stabilize the clavicle.
Physiology
5 questionsWhat does Einthoven's law state regarding the relationship between the electrical potentials of the limb leads?
Which sensory modalities are most directly affected by lesions of the primary somatosensory cortex?
What percentage of gastric secretion is attributed to the cephalic phase?
Which hormone primarily inhibits gastric acid secretion in response to acidic chyme?
Wolff–Chaikoff effect is due to?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 201: What does Einthoven's law state regarding the relationship between the electrical potentials of the limb leads?
- A. I + III = II (Correct Answer)
- B. I - III = II
- C. I + II + III = 0
- D. I + III = avL
Explanation: ***I + III = II*** - Einthoven's law describes the relationship between the three **bipolar limb leads** (I, II, and III) in an **electrocardiogram (ECG)**. - It states that the electrical potential of Lead II is equal to the sum of the potentials of Lead I and Lead III (Lead II = Lead I + Lead III). - This can also be expressed as **I + III = II**, which is the **correct mathematical representation** of Einthoven's law. *I - III = II* - This equation is **incorrect** and does not represent Einthoven's law. - The correct relationship involves **addition** of Leads I and III, not subtraction. *I + II + III = 0* - This equation is **incorrect** as written with all positive signs. - Einthoven's law can be rearranged as **I + III - II = 0** (not I + II + III = 0). - The equation shown suggests adding all three leads to get zero, which is **mathematically inconsistent** with the correct formulation (I + III = II). *I + III = avL* - This equation is incorrect and does not relate to Einthoven's law. - **avL (augmented vector left)** is one of the augmented unipolar limb leads calculated as: avL = I - (II/2), not as a direct sum of Leads I and III.
Question 202: Which sensory modalities are most directly affected by lesions of the primary somatosensory cortex?
- A. Pain, temperature, and touch
- B. Vibration and proprioception
- C. Localization and two-point discrimination (Correct Answer)
- D. All of the options
Explanation: ***Localization and two-point discrimination*** - Lesions in the **primary somatosensory cortex** (S1) lead to profoundly impaired **discriminative touch**, which includes the ability to precisely localize tactile stimuli and distinguish between two closely spaced points. - These are the **most characteristic deficits** of S1 lesions, representing the cortex's unique role in processing **spatial discrimination and fine sensory analysis**. - S1 is essential for the **integrative functions** that allow precise spatial mapping of sensory inputs. *Pain, temperature, and touch* - Basic touch perception is affected, but **pain and temperature** are primarily mediated by the **spinothalamic tracts** with substantial processing in the thalamus, insular cortex, and anterior cingulate cortex rather than S1. - Crude touch sensation remains relatively preserved with S1 lesions; it is the **discriminative quality** that is lost. - These modalities are NOT the most directly affected by isolated S1 lesions. *Vibration and proprioception* - **Vibration** and **proprioception** are indeed significantly impacted by S1 lesions as S1 receives thalamic projections from the **dorsal column-medial lemniscus (DCML) pathway**. - However, these modalities have substantial **subcortical representation** in the thalamus and can be partially preserved even with cortical damage. - In contrast, **localization and two-point discrimination** are purely cortical functions with no subcortical processing, making them the MOST directly and exclusively dependent on S1 integrity. *All of the options* - This is incorrect because pain and temperature perception is NOT most directly affected by S1 lesions—these are primarily processed by other pathways and cortical areas (spinothalamic system, insular cortex).
Question 203: What percentage of gastric secretion is attributed to the cephalic phase?
- A. 20% (Correct Answer)
- B. 70%
- C. 10%
- D. 100%
Explanation: ***20%*** - The **cephalic phase** of gastric secretion is initiated by the sight, smell, taste, or even thought of food and accounts for approximately **20-30%** of total gastric acid secretion. - This phase is mediated by the **vagus nerve**, stimulating parietal cells (via acetylcholine) and G cells (via gastrin-releasing peptide) to release acid and gastrin, respectively. *70 %* - **70%** represents the approximate contribution of the **gastric phase** to total gastric secretion, which is the largest phase. - This phase is activated by the presence of food in the stomach, distension, and the presence of amino acids and peptides. *10%* - **10%** is a value that is too low for the cephalic phase; it typically accounts for a more significant portion of initial acid secretion. - This percentage is sometimes associated with the intestinal phase, which produces a smaller amount of acid secretion after chyme enters the duodenum. *100%* - **100%** is incorrect because gastric secretion is a complex process involving multiple phases (cephalic, gastric, intestinal), each contributing a portion of the total secretion. - Each phase has distinct stimuli and regulatory mechanisms, ensuring a coordinated digestive response.
Question 204: Which hormone primarily inhibits gastric acid secretion in response to acidic chyme?
- A. Secretin
- B. Somatostatin (Correct Answer)
- C. Insulin
- D. Gastrin
Explanation: ***Somatostatin*** - **Somatostatin** is the **primary hormone** that inhibits gastric acid secretion in response to acidic chyme. - Released by D cells in the stomach and duodenum when pH drops below 3.0. - **Direct inhibitory effects:** Inhibits parietal cells directly, suppresses gastrin release from G cells, and blocks histamine release from ECL cells. - Acts as the main **negative feedback mechanism** to prevent excessive gastric acidification. *Secretin* - **Secretin** is released by S cells in the duodenum in response to acidic chyme (pH < 4.5). - Its **primary function** is to stimulate pancreatic bicarbonate secretion to neutralize duodenal acid. - While it does have a **secondary effect** of inhibiting gastric acid secretion, this is not its primary role. *Gastrin* - **Gastrin** is a hormone that **stimulates** gastric acid secretion, not inhibits it. - Released by G cells in the gastric antrum in response to peptides, amino acids, and gastric distension. - Promotes acid secretion by stimulating parietal cells and ECL cells (which release histamine). *Insulin* - **Insulin** is a pancreatic hormone primarily involved in **glucose metabolism** and cellular glucose uptake. - It has **no significant role** in the regulation of gastric acid secretion.
Question 205: Wolff–Chaikoff effect is due to?
- A. Decreased iodination of MIT
- B. Excess iodine intake (Correct Answer)
- C. Suppression of TSH secretion
- D. Decreased conversion of T4 to T3
Explanation: ***Excess iodine intake*** - The **Wolff-Chaikoff effect** is a phenomenon where a high intake of iodine acutely **inhibits thyroid hormone synthesis** and release. - This effect protects the body from excessive thyroid hormone production during periods of very high iodine availability. *Decreased iodination of MIT* - While the Wolff-Chaikoff effect does inhibit **iodination**, the direct cause is the excessive iodine itself, which triggers an autoregulatory shutdown. - Decreased iodination is a *consequence* of the high iodine leading to inhibition of thyroid peroxidase activity, but not the primary cause of the effect. *Suppression of TSH secretion* - **TSH (Thyroid Stimulating Hormone)** secretion is primarily regulated by negative feedback from thyroid hormones (T3 and T4) and TRH from the hypothalamus. - The Wolff-Chaikoff effect directly involves the thyroid gland's response to iodine and is not primarily mediated by TSH suppression. *Decreased conversion of T4 to T3* - The **conversion of T4 to T3** primarily occurs in peripheral tissues, mediated by deiodinase enzymes. - The Wolff-Chaikoff effect focuses on the inhibition of **iodine organification** and hormone release within the thyroid gland itself, not peripheral conversion.