FMGE 2018 — Anatomy

Q: Which bone attaches the sternum to the scapula?

Clavicle. **Explanation:** The **Clavicle** (collarbone) is the correct answer because it serves as the only bony attachment between the upper limb and the axial skeleton. This connection is formed through two primary joints: 1. **Sternoclavicular (SC) Joint:** The medial end of the clavicle articulates with the manubrium of the sternum. 2. **Acromiovicular (AC) Joint:** The lateral end of the clavicle articulates with the acromion process of the scapula. By bridging these two points, the clavicle acts as a "strut," holding the scapula and humerus away from the thorax to allow for maximum range of motion. **Why other options are incorrect:** * **Manubrium:** This is the superior part of the sternum itself. While it provides the site for clavicular attachment, it does not directly reach or attach to the scapula. * **First Rib:** It lies inferior to the clavicle and articulates with the manubrium and the T1 vertebra. It does not articulate with the scapula (the scapula "glides" over the ribs via the physiological scapulothoracic joint, but there is no bony attachment). * **Second Rib:** It articulates with the sternal angle (Angle of Louis) and the T2 vertebra, playing no role in connecting the sternum to the scapula. **High-Yield NEET-PG Pearls:** * **First bone to ossify:** The clavicle is the first bone in the body to begin ossification (5th–6th week of fetal life). * **Ossification type:** It is the only long bone that undergoes **intramembranous ossification** (though its ends undergo endochondral ossification). * **Fracture Site:** The most common site of fracture is the junction of the medial two-thirds and lateral one-third. * **Clinical Sign:** In clavicular fractures, the medial fragment is elevated by the **Sternocleidomastoid** muscle.

Q: Which branch of the facial nerve supplies the muscles of the lower lip?

Mandibular. The facial nerve (CN VII) exits the stylomastoid foramen and enters the parotid gland, where it divides into five terminal branches that provide motor innervation to the muscles of facial expression. **1. Why Mandibular is Correct:** The **Marginal Mandibular branch** emerges from the lower part of the parotid gland and runs along or just below the lower border of the mandible. It supplies the muscles of the lower lip and chin, specifically the **depressor anguli oris, depressor labii inferioris, and mentalis**. Damage to this branch results in an asymmetrical smile due to the inability to depress the corner of the mouth on the affected side. **2. Why Other Options are Incorrect:** * **Temporal:** Supplies the muscles above the eye, including the frontalis, orbicularis oculi (upper part), and corrugator supercilii. * **Cervical:** Runs downward to supply the **platysma** muscle in the neck. * **Buccal:** Supplies the muscles of the cheek (**buccinator**) and the upper lip (orbicularis oris, levator labii superioris). While it contributes to the mouth area, the specific innervation for *lower lip depression* is mandibular. **3. High-Yield Clinical Pearls for NEET-PG:** * **Pes Anserinus:** The "goose's foot" pattern formed by the five terminal branches (Temporal, Zygomatic, Buccal, Mandibular, Cervical) within the parotid gland. * **Danger Zone:** The marginal mandibular nerve is vulnerable during submandibular gland surgery as it can dip up to 1–2 cm below the inferior border of the mandible. * **Buccinator Paradox:** The buccinator is a muscle of facial expression (supplied by the Buccal branch of CN VII) but is often confused with muscles of mastication (supplied by CN V3).

22 Questions — Page 3 of 3

Q21Easy

Which bone attaches the sternum to the scapula?

Q22Easy

Which branch of the facial nerve supplies the muscles of the lower lip?