Systemic Anatomy — MCQs

Systemic Anatomy Indian Medical PG Practice Questions and MCQs

Question 91: Which of the following is an example of a syndesmosis joint?

A. Tibiotalar joint
B. Tibiofibular joint (Correct Answer)
C. Elbow joint
D. Carpometacarpal joint

Explanation: **Explanation:** A **syndesmosis** is a type of fibrous joint where two adjacent bones are linked by a strong membrane or ligament (interosseous membrane). Unlike sutures, the gap between bones is wider, allowing for slight functional movement (amphiarthrosis). **1. Why the Tibiofibular joint is correct:** The **inferior (distal) tibiofibular joint** is the classic example of a syndesmosis. It is held together by the anterior and posterior tibiofibular ligaments and the interosseous membrane. This stability is crucial for maintaining the integrity of the "ankle mortise." (Note: The superior tibiofibular joint is technically a plane synovial joint, but in the context of standard medical exams, "tibiofibular joint" refers to the syndesmosis). **2. Analysis of Incorrect Options:** * **Tibiotalar joint (A):** This is the true ankle joint. It is a **synovial hinge joint** allowing dorsiflexion and plantarflexion. * **Elbow joint (C):** A complex **synovial hinge joint** involving the humerus, radius, and ulna. * **Carpometacarpal joint (D):** These are **synovial joints**. Specifically, the CMC joint of the thumb is a saddle joint, while the others are plane synovial joints. **3. NEET-PG High-Yield Pearls:** * **Other Syndesmosis Examples:** The middle radio-ulnar joint (interosseous membrane). * **Clinical Correlation:** A "High Ankle Sprain" refers to an injury of the distal tibiofibular syndesmosis. * **Classification Reminder:** * *Fibrous:* Sutures, Gomphosis (teeth), Syndesmosis. * *Cartilaginous:* Primary (Synchondrosis - e.g., growth plate) and Secondary (Symphysis - e.g., Pubic symphysis). * *Synovial:* Most mobile joints (Hinge, Pivot, Saddle, etc.).

Question 92: Which of the following muscles is a convergent muscle?

A. Subscapularis
B. Deltoid
C. Temporalis (Correct Answer)
D. Pectoralis minor

Explanation: ### Explanation The classification of muscles based on fascicular architecture is a high-yield topic in anatomy. Muscle fibers are arranged to balance the range of motion and force production. **1. Why Temporalis is the Correct Answer:** A **convergent muscle** (also known as a triangular muscle) is characterized by a broad origin where muscle fibers converge toward a single, narrow tendon of insertion. The **Temporalis** muscle originates from the wide temporal fossa and converges into a thick tendon that inserts onto the coronoid process of the mandible. This arrangement allows for a powerful contraction concentrated on a single point. **2. Analysis of Incorrect Options:** * **Subscapularis (Option A):** This is classified as a **multipennate** muscle. While it has a broad origin, its internal structure consists of multiple septa of tendons with fibers arranged obliquely, similar to several feathers joined together. * **Deltoid (Option B):** This is the classic example of a **multipennate** muscle (specifically the acromial part). It is designed for high force production but limited range of motion. * **Pectoralis Minor (Option D):** While often confused with convergent muscles, the Pectoralis minor is typically classified as a **flat/procerus** muscle or sometimes a simple triangular muscle. However, in standard anatomical classification for exams, **Pectoralis Major** is the classic convergent muscle, whereas Pectoralis Minor is less representative of the "convergent" definition compared to the Temporalis. **3. NEET-PG High-Yield Pearls:** * **Parallel Muscles:** Sartorius (longest muscle), Rectus Abdominis (straplike with tendinous intersections). * **Pennate Muscles:** Unipennate (Flexor Pollicis Longus), Bipennate (Rectus Femoris), Multipennate (Deltoid, Subscapularis). * **Circular Muscles:** Orbicularis Oculi/Oris (act as sphincters). * **Convergent Examples:** Pectoralis Major and Temporalis are the two most frequently tested examples.

Question 93: What is the solid and largest lymphatic organ of the body?

A. Spleen (Correct Answer)
B. Thymus
C. Lymph node
D. Liver

Explanation: **Explanation:** The **Spleen** is the correct answer because it is the largest single mass of lymphoid tissue in the human body. Located in the left hypochondrium (under the 9th to 11th ribs), it acts as a sophisticated filter for blood [1]. Unlike lymph nodes, which filter lymph, the spleen filters blood, removing aged red blood cells and responding to blood-borne antigens [1]. It is considered a "solid" organ due to its dense parenchyma, consisting of red pulp (blood filtration) and white pulp (lymphoid tissue). **Analysis of Incorrect Options:** * **B. Thymus:** While a primary lymphoid organ essential for T-cell maturation, it is much smaller than the spleen and undergoes atrophy (involution) after puberty, being replaced by fat. * **C. Lymph node:** These are small, bean-shaped structures scattered throughout the body [2]. While they are numerous, an individual lymph node is significantly smaller than the spleen. * **D. Liver:** Although the liver is the largest **gland** and the largest internal organ in the body, it is not classified as a lymphatic organ, despite its role in producing a large volume of the body's lymph. **High-Yield Clinical Pearls for NEET-PG:** * **Harris’s Rule of Odd Numbers:** The spleen measures 1 x 3 x 5 inches, weighs 7 ounces, and relates to ribs 9, 10, and 11. * **Kehr’s Sign:** Referred pain to the left shoulder due to diaphragmatic irritation following a splenic rupture. * **Post-Splenectomy:** Patients are at high risk for infections by encapsulated organisms (e.g., *S. pneumoniae*, *H. influenzae*, *N. meningitidis*); OPSI (Overwhelming Post-Splenectomy Infection) is a critical complication [1].

Question 94: As a general rule, veins carry which of the following?

A. Urine
B. Lymph fluid
C. Oxygenated blood
D. Deoxygenated blood (Correct Answer)

Explanation: **Explanation:** In the human circulatory system, **veins** are blood vessels that carry blood toward the heart. As a general rule, systemic veins carry **deoxygenated blood** from the peripheral tissues back to the right atrium [3]. This blood is rich in carbon dioxide and metabolic waste products after gas exchange has occurred at the capillary level. **Analysis of Options:** * **Option A (Urine):** Urine is transported from the kidneys to the bladder via the **ureters** and excreted via the **urethra**. It is never carried by blood vessels. * **Option B (Lymph fluid):** This is carried by the **lymphatic system** (lymphatic vessels). While the lymphatic system eventually drains into the venous system (at the junction of the internal jugular and subclavian veins), veins themselves primarily carry blood. * **Option C (Oxygenated blood):** This is the characteristic of **arteries** in the systemic circulation. Arteries carry oxygen-rich blood away from the heart to the tissues. **Clinical Pearls & High-Yield Facts for NEET-PG:** 1. **The "Exception" Rule:** In NEET-PG, always remember the exceptions to the general rule. The **Pulmonary Veins** carry oxygenated blood (from lungs to left atrium), and the **Umbilical Vein** carries oxygenated blood (from placenta to fetus) [1]. 2. **Valves:** Unlike arteries, most veins (especially in the lower limbs) contain **valves** to prevent the backflow of blood due to gravity [2]. 3. **Capacitance Vessels:** Veins are known as "capacitance vessels" because they hold approximately **65-70%** of the body's total blood volume at any given time. 4. **Portal Vein:** The Hepatic Portal Vein is unique as it begins and ends in capillaries, transporting nutrient-rich (but deoxygenated) blood from the GI tract to the liver.

Question 95: How many parathyroid glands do humans typically have?

A. 4 (Correct Answer)
B. 3
C. 2
D. 1

Explanation: **Explanation:** **Correct Option: A (4)** In the majority of humans (approximately 85–90%), there are **four parathyroid glands**. These are small, lentil-shaped endocrine glands located on the posterior aspect of the thyroid gland [1], [2]. They are organized into two pairs: * **Superior Parathyroid Glands:** Typically located at the middle of the posterior border of the thyroid lobe, above the entry of the inferior thyroid artery [1]. * **Inferior Parathyroid Glands:** Usually located near the inferior pole of the thyroid gland [1]. **Why other options are incorrect:** * **Options B, C, and D:** While anatomical variations exist, having only 1, 2, or 3 glands is rare and usually the result of surgical removal, congenital aplasia (e.g., DiGeorge Syndrome), or failure to locate ectopic glands during dissection. Some individuals (up to 15%) may actually have supernumerary glands (5 or more), often found within the thymus or mediastinum. **NEET-PG High-Yield Pearls:** 1. **Embryology (Crucial):** * **Superior Parathyroids** develop from the **4th pharyngeal pouch**. * **Inferior Parathyroids** develop from the **3rd pharyngeal pouch** (along with the Thymus). 2. **Blood Supply:** Both superior and inferior glands are primarily supplied by the **Inferior Thyroid Artery** (a branch of the thyrocervical trunk) [1]. This is a vital landmark during thyroidectomy to avoid accidental ischemia. 3. **Clinical Correlation:** During a total thyroidectomy, surgeons must identify and preserve these glands to prevent **hypocalcemia**, which manifests clinically as Trousseau’s sign or Chvostek’s sign.

Question 96: Which of the following enzyme activities is NOT increased in the fasting state?

A. Acetyl CoA carboxylase (Correct Answer)
B. Carnitine acyl transferase
C. Phosphoenolpyruvate carboxykinase
D. Pyruvate carboxylase

Explanation: ### Explanation The metabolic state of the body is governed by the **Insulin:Glucagon ratio**. In the **fasting state**, glucagon levels rise, shifting the metabolism toward energy mobilization (lipolysis and gluconeogenesis) rather than energy storage (lipogenesis) [4]. **Why Acetyl CoA Carboxylase (ACC) is the correct answer:** ACC is the **rate-limiting enzyme for Fatty Acid Synthesis**. It converts Acetyl CoA to Malonyl CoA. In the fasting state, high glucagon levels lead to the phosphorylation and subsequent **inactivation** of ACC (via AMP-activated protein kinase). Since the body needs to burn fat rather than store it during a fast, ACC activity is significantly decreased. **Analysis of Incorrect Options:** * **Carnitine Acyl Transferase (CAT-I):** This is the rate-limiting enzyme for **Beta-oxidation** (fatty acid breakdown) [1]. In fasting, Malonyl CoA levels drop (due to inactive ACC), relieving the inhibition on CAT-I and allowing fatty acids to enter the mitochondria for energy production. Thus, its activity is effectively **increased**. * **Phosphoenolpyruvate Carboxykinase (PEPCK):** This is a key regulatory enzyme of **Gluconeogenesis**. It converts oxaloacetate to phosphoenolpyruvate [2]. Its transcription is induced by glucagon and glucocorticoids during fasting to maintain blood glucose levels [2]. * **Pyruvate Carboxylase:** This enzyme converts pyruvate to oxaloacetate, providing the substrate for **Gluconeogenesis** [3]. It is allosterically activated by Acetyl CoA, which accumulates during fasting from increased beta-oxidation. **High-Yield NEET-PG Pearls:** * **Rate-Limiting Enzymes:** Always remember ACC for Fatty Acid Synthesis and HMG-CoA Reductase for Cholesterol Synthesis; both are **inhibited** by Glucagon/Fasting. * **Malonyl CoA:** Acts as a "switch" by inhibiting CAT-I, preventing a futile cycle where fatty acids are synthesized and degraded simultaneously. * **Hormonal Control:** Glucagon/Epinephrine generally stimulate **phosphorylation** of enzymes, which activates catabolic enzymes (e.g., Glycogen Phosphorylase) but inactivates anabolic ones (e.g., ACC, Glycogen Synthase).

Question 97: Sympathetic stimulation increases blood flow to all of the following except:

A. Skin (Correct Answer)
B. Coronary circulation
C. Cerebral
D. Renal

Explanation: The sympathetic nervous system (SNS) is designed for the "fight or flight" response, prioritizing blood flow to vital organs while diverting it from non-essential areas. [1] **Why Skin is the correct answer:** Sympathetic stimulation causes **vasoconstriction** in the skin via **$\alpha_1$-adrenergic receptors**. [1] This reduces cutaneous blood flow to minimize bleeding in case of injury and to shunt blood toward the heart and muscles. Therefore, sympathetic activity decreases, rather than increases, blood flow to the skin. [2] **Analysis of Incorrect Options:** * **Coronary Circulation:** During sympathetic stimulation, the heart rate and contractility increase. This leads to the accumulation of local metabolites (like adenosine) and activation of $\beta_2$ receptors, causing **vasodilation** to meet the increased oxygen demand of the myocardium. [2] * **Cerebral Circulation:** While primarily controlled by autoregulation ($CO_2$ levels), sympathetic stimulation helps maintain cerebral perfusion pressure during stress. It does not cause significant vasoconstriction in the brain compared to the skin or viscera. [2] * **Renal Circulation:** This is a nuanced point. While strong sympathetic stimulation causes vasoconstriction to divert blood to the heart/muscles, moderate sympathetic activity (via the Renin-Angiotensin-Aldosterone System) maintains perfusion pressure. However, in the context of "redistribution," the skin is the primary site where flow is actively and significantly reduced. [2] **High-Yield NEET-PG Pearls:** * **Receptor Rule:** $\alpha_1$ = Vasoconstriction (Skin, GI tract); $\beta_2$ = Vasodilation (Skeletal muscle, Coronary arteries). * **Exception:** Sympathetic postganglionic fibers to **sweat glands** are **cholinergic** (release Acetylcholine), not adrenergic. * **Skeletal Muscle:** Sympathetic stimulation causes vasodilation here to facilitate physical exertion. [1]

Question 98: Agonistic action at which of the following adrenergic receptors results in the reduction of excess secretion?

A. Beta 1 receptor
B. Beta 2 receptor
C. M2 receptor
D. Alpha 2 receptor (Correct Answer)

Explanation: The correct answer is **Alpha 2 receptor (D)**. This question tests the understanding of the autonomic nervous system's regulatory mechanisms, specifically **presynaptic inhibition**. **Why Alpha 2 is correct:** Alpha 2 ($\alpha_2$) receptors are primarily located on the **presynaptic nerve terminals**. They function as "autoreceptors" that provide a negative feedback loop. When an agonist binds to these receptors, it inhibits the further release of neurotransmitters (like norepinephrine and acetylcholine) from the nerve endings [1]. By reducing the release of these neurotransmitters, $\alpha_2$ agonism effectively leads to a **reduction in glandular secretions** and sympathetic outflow. **Why the other options are incorrect:** * **Beta 1 ($\beta_1$):** These are primarily found in the heart. Agonism leads to increased heart rate (chronotropy) and contractility (inotropy), rather than a reduction in secretions. * **Beta 2 ($\beta_2$):** Agonism here typically causes smooth muscle relaxation (bronchodilation, vasodilation) and can actually increase certain secretions (e.g., aqueous humor in the eye). * **M2 receptor:** While these are inhibitory receptors found in the heart (slowing the heart rate), they are **muscarinic**, not adrenergic receptors as specified by the question's context of "adrenergic receptors." **High-Yield NEET-PG Pearls:** * **Clonidine and Dexmedetomidine** are classic $\alpha_2$ agonists used clinically to reduce sympathetic tone and provide sedation/analgesia. * **Apraclonidine/Brimonidine** ($\alpha_2$ agonists) are used in glaucoma specifically because they **reduce the secretion** of aqueous humor. * Remember: $\alpha_1$ is generally excitatory (postsynaptic), while $\alpha_2$ is generally inhibitory (presynaptic).

Question 99: Metformin is NOT effective in lowering of blood sugar level in which of the following patients?

A. Non-diabetics (Correct Answer)
B. Obese diabetics
C. Type 2 diabetics
D. Diabetics not responding to sulfonylureas

Explanation: **Explanation:** The core mechanism of **Metformin** (a Biguanide) is that it acts as an **euglycemic agent**, not a hypoglycemic agent. It lowers blood glucose levels primarily by inhibiting hepatic gluconeogenesis and increasing peripheral insulin sensitivity. Crucially, it does **not** stimulate insulin secretion from pancreatic beta cells [1]. Therefore, in a non-diabetic individual with normal blood sugar levels, Metformin will not further lower the blood glucose, making it ineffective for inducing hypoglycemia. **Analysis of Options:** * **Non-diabetics (Correct):** Since Metformin does not increase insulin levels, it has no significant effect on blood glucose in healthy individuals. It only lowers elevated blood sugar toward normal levels. * **Obese diabetics:** Metformin is the first-line drug of choice here. It promotes modest weight loss and improves insulin resistance, which is the hallmark of obesity-related Type 2 Diabetes Mellitus (T2DM). * **Type 2 diabetics:** This is the primary indication for Metformin [2]. It effectively reduces HbA1c by suppressing hepatic glucose output. * **Diabetics not responding to sulfonylureas:** Metformin is often added as a second-line agent or used in patients who have "secondary failure" to sulfonylureas, as it works via a different, insulin-independent mechanism [1]. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Metformin is the first-line treatment for T2DM. * **Mechanism:** Activates **AMP-activated protein kinase (AMPK)**. * **Side Effects:** Most common are GI upset (diarrhea/nausea); most serious is **Lactic Acidosis** (rare but fatal). * **Contraindication:** Avoid in patients with significant renal impairment (CrCl <30 mL/min) due to the risk of lactic acidosis. * **Vitamin Deficiency:** Long-term use can lead to **Vitamin B12 deficiency**.

Question 100: Which of the following is a fibrous joint?

A. Pubic symphysis
B. Fronto-parietal suture (Correct Answer)
C. Manubrio-sternal joint
D. Inferior radio-ulnar joint

Explanation: Joints are classified based on the type of connective tissue that binds the bones together. **Fibrous joints** are characterized by bones joined by dense fibrous connective tissue with little to no movement (synarthrosis). **1. Why the Correct Answer is Right:** * **Fronto-parietal suture (Option B):** This is a classic example of a **Suture**, a type of fibrous joint found exclusively in the skull [1]. Specifically, the fronto-parietal suture is the **Coronal Suture**. These joints provide stability and protect the brain by allowing no movement once the fontanelles have closed. **2. Analysis of Incorrect Options:** * **Pubic symphysis (Option A):** This is a **Secondary Cartilaginous joint** (Symphysis). It consists of a fibrocartilaginous disc between the bone surfaces and is located in the midline of the body. * **Manubrio-sternal joint (Option B):** This is also a **Secondary Cartilaginous joint**. Although it may ossify with age (synostosis), it is functionally classified with the symphyses. * **Inferior radio-ulnar joint (Option D):** This is a **Pivot-type Synovial joint**. It allows for the rotation of the radius around the ulna during pronation and supination. (Note: The *middle* radio-ulnar joint is a fibrous syndesmosis, but the *inferior* and *superior* are synovial). **3. NEET-PG High-Yield Pearls:** * **Types of Fibrous Joints:** Remember the triad: **Sutures** (skull), **Gomphosis** (teeth in sockets), and **Syndesmosis** (e.g., inferior tibio-fibular joint). * **Primary vs. Secondary Cartilaginous:** Primary (Synchondrosis) involves hyaline cartilage and usually disappears with age (e.g., epiphyseal plate) [1]. Secondary (Symphysis) involves fibrocartilage and occurs in the midline. * **Sutural Growth:** The fontanelles are the membrane-filled spaces between cranial bones in neonates; the anterior fontanelle typically closes by 18–24 months.

Practice by Chapter

Skeletal System

Practice Questions

Articular System

Practice Questions

Muscular System

Practice Questions

Cardiovascular System

Practice Questions

Lymphatic System

Practice Questions

Nervous System

Practice Questions

Respiratory System

Practice Questions

Digestive System

Practice Questions

Urinary System

Practice Questions

Reproductive System

Practice Questions

Endocrine System

Practice Questions

Integumentary System

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free