Systemic Anatomy Practice Questions

Q: Which muscle does not have a dual nerve supply?

Thyrohyoid. The concept of **dual nerve supply** (hybrid muscles) refers to muscles innervated by two different nerves, often reflecting their complex embryological origins. ### **Why Thyrohyoid is the Correct Answer** The **Thyrohyoid** is a unique infrahyoid muscle. Unlike other muscles in this region, it is supplied **solely by the C1 nerve fibers** traveling via the **Hypoglossal nerve (CN XII)**. It does not receive a second nerve supply, nor is it supplied by the Ansa cervicalis (which supplies the Omohyoid, Sternohyoid, and Sternothyroid). ### **Analysis of Incorrect Options** * **Digastric:** This is a classic hybrid muscle. The **Anterior belly** is derived from the 1st pharyngeal arch (Nerve to Mylohyoid, CN V3), while the **Posterior belly** is derived from the 2nd arch (Facial nerve, CN VII). * **Trapezius:** It receives a dual supply: **Spinal accessory nerve (CN XI)** provides motor innervation, while the **ventral rami of C3 and C4** provide sensory (proprioceptive) fibers. * **Adductor Magnus:** This is a "hybrid" muscle of the lower limb. The **Adductor part** is supplied by the **Obturator nerve**, and the **Hamstring part** is supplied by the **Tibial component of the Sciatic nerve**. ### **High-Yield NEET-PG Pearls** * **Geniohyoid:** Like the Thyrohyoid, it is also supplied exclusively by **C1 via CN XII**. * **Pectineus:** Often considered a hybrid muscle, supplied by the **Femoral nerve** and occasionally the **Obturator nerve**. * **Brachialis:** Supplied by the **Musculocutaneous nerve** (motor) and the **Radial nerve** (proprioceptive). * **Flexor Digitorum Profundus:** Medial half by the **Ulnar nerve**, lateral half by the **Median nerve** (Anterior Interosseous Nerve).

Q: Small bones are supplied by which type of vessels?

Periosteal vessels. **Explanation:** The blood supply of bones varies significantly based on their morphology. **Small bones** (such as the carpals and tarsals) are primarily supplied by **periosteal vessels**. These vessels form a rich plexus on the surface of the bone and enter through numerous small foramina to supply the underlying cortex and cancellous tissue. Unlike long bones, most small bones lack a distinct medullary cavity and a single dominant nutrient artery. **Analysis of Options:** * **Periosteal vessels (Correct):** These are the primary source for small bones and the outer one-third of the cortex in long bones. In small bones, they provide a circumferential supply. * **Nutrient artery (Incorrect):** This is the principal source for **long bones**, entering through a specific nutrient foramen to supply the inner two-thirds of the cortex and the bone marrow. * **Subperiosteal vessels (Incorrect):** This is a descriptive term for vessels located beneath the periosteum, but "periosteal vessels" is the standard anatomical term for the functional supply. * **Epiphyseal vessels (Incorrect):** These are specific to the ends (epiphyses) of **long bones**, arising from the arterial anastomosis around joints (e.g., circulus vasculosus). **High-Yield Facts for NEET-PG:** * **Long Bones:** Supplied by four sets of arteries: Nutrient, Periosteal, Epiphyseal, and Metaphyseal. * **Vertebrae:** Supplied by spinal branches of segmental arteries. * **Clinical Pearl:** In cases of fractures where the periosteum is extensively stripped (e.g., comminuted fractures of small bones), the risk of **avascular necrosis (AVN)** increases because the primary blood supply (periosteal) is compromised. * **Nutrient Foramen Rule:** "To the elbow I go, from the knee I flee"—this dictates the direction of the nutrient canal in long bones.

Q: Which is the most vascular part of a bone?

Metaphysis. ### Explanation The **Metaphysis** is the most vascular part of a bone. This high vascularity is primarily due to the presence of **hairpin-like capillary loops** derived from the nutrient artery. These vessels are thin-walled, have a sluggish blood flow, and lack a basement membrane, making the metaphysis a highly active metabolic zone. **Why Metaphysis is the Correct Answer:** * **Vascular Anatomy:** It receives a rich blood supply from three sources: the nutrient artery, metaphyseal arteries, and periosteal arteries. * **Clinical Significance:** Because of the slow, turbulent blood flow in the capillary loops, bacteria tend to settle here. This makes the metaphysis the **most common site for Acute Hematogenous Osteomyelitis** in children. Similarly, its high metabolic activity makes it a frequent site for primary bone tumors (e.g., Osteosarcoma). **Why Other Options are Incorrect:** * **Epiphysis:** While vascularized by epiphyseal arteries, it is less vascular than the metaphysis. In children, the growth plate acts as a barrier, preventing metaphyseal vessels from crossing into the epiphysis. * **Diaphysis:** This is the shaft of the bone. It has a relatively lower blood supply compared to the metaphysis, consisting mainly of the nutrient artery canal and periosteal vessels. * **Epiphyseal Cartilage (Growth Plate):** This is essentially **avascular**. It receives nutrients via diffusion from surrounding vessels but does not have an intrinsic vascular network. **High-Yield NEET-PG Pearls:** 1. **Osteomyelitis Site:** Metaphysis is the most common site in children; however, in adults (after growth plate closure), the infection can spread to the **Epiphysis**. 2. **Tumor Location:** Most primary bone tumors (Osteosarcoma, Giant Cell Tumor, Ewing’s Sarcoma) occur near the metaphysis due to rapid cell turnover and high vascularity. 3. **Blood Supply:** The **Nutrient Artery** provides 70% of the blood supply to a long bone.

Q: What type of joint is indicated at the site marked by the arrow?

Synovial Joint. ***Synovial Joint*** - Contains a **joint cavity** filled with **synovial fluid**, allowing for free movement and lubrication between bone surfaces. - Features **articular cartilage**, **synovial membrane**, and a **joint capsule**, making it a freely movable (**diarthrodial**) joint. *Syndesmosis* - A **fibrous joint** where bones are connected by **ligaments** or **interosseous membranes** without a joint cavity. - Allows only **slight movement** and is classified as **amphiarthrodial**, unlike the freely movable joint shown. *Synarthrosis* - Refers to **immovable fibrous joints** where bones are directly connected by **fibrous tissue**. - Lacks a **joint cavity** and permits **no movement**, which contradicts the mobile nature of the arrowed joint. *Symphysis* - A **secondary cartilaginous joint** where bones are united by **fibrocartilage** (like the **pubic symphysis**). - Allows only **slight movement** and lacks the **synovial cavity** characteristic of the joint in question.

Question 1

Which muscle does not have a dual nerve supply?

Accepted Answer

Thyrohyoid

Answer

Digastric

Answer

Trapezius

Answer

Adductor magnus

Question 2

Small bones are supplied by which type of vessels?

Accepted Answer

Periosteal vessels

Answer

Nutrient artery

Answer

Subperiosteal vessels

Answer

Epiphyseal vessels

Question 3

Which of the following is NOT an end artery?

Accepted Answer

Splenic artery

Answer

Central artery of retina

Answer

Artery of Wilkie

Answer

Appendicular artery

Question 4

Which is the most vascular part of a bone?

Accepted Answer

Metaphysis

Answer

Epiphysis

Answer

Diaphysis

Answer

Epiphyseal cartilage

Question 5

What type of joint is indicated at the site marked by the arrow?

Accepted Answer

Synovial Joint

Answer

Syndesmosis

Answer

Synarthrosis

Answer

Symphysis

Systemic Anatomy — MCQs

Systemic Anatomy — MCQs

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