**Question:** Chewing stroke begins from:

A.
B.
C.
D.

**Correct Answer:** D.

**Core Concept:** The chewing stroke is a part of the masticatory process, which involves the coordinated movements of the jaw muscles to crush, grind, and mix food for easier swallowing and digestion. The four phases of the masticatory process are:

1. **Closing Stroke:** The first phase, also known as the "locking" or "bitting" phase, where the mandible (jaw) is brought together by the temporalis and masseter muscles, leading to food being trapped between the teeth.
2. **Chewing Stroke:** The second phase, which involves the coordinated contraction and relaxation of the temporalis, masseter, and digastric muscles. This phase is essential for crushing and grinding the food.
3. **Opening Stroke:** The third phase, where the mandible is raised by the temporalis and masseter muscles, allowing the food to be released and moved to the pharynx (throat).
4. **Transport Stroke:** The fourth phase, where the mandible is lowered by the temporalis and masseter muscles, guiding the food to the pharynx for further processing in the gastrointestinal tract.

**Why the Correct Answer is Right:**

The correct answer, D, refers to the chewing stroke, which is the second phase of the masticatory process. The chewing stroke primarily occurs due to the coordinated contraction and relaxation of the temporalis, masseter, and digastric muscles. These muscles work together to crush and grind the food, preparing it for swallowing and further digestion.

**Why Each Wrong Option is Incorrect:**

A, B, and C are incorrect because they represent other phases of the masticatory process or muscles involved in different phases.

A. Closing stroke: The closing stroke, also known as the biting phase, is the first phase where the jaw is brought together by the temporalis and masseter muscles, preparing the food for chewing.
B. Opening stroke: The opening stroke is the third phase, where the jaw is raised by the temporalis and masseter muscles, allowing the chewed food to be released and moved to the pharynx.
C. Transport stroke: The transport stroke is the fourth phase, where the jaw is lowered by the temporalis and masseter muscles, guiding the chewed food to the pharynx for further processing in the gastrointestinal tract.

**Clinical Pearl:**

Understanding the masticatory process and its phases is crucial for proper food processing and swallowing. Properly timing and coordinating muscle contractions and relaxations ensure efficient food crushing, grinding, and transport to the pharynx, ultimately leading to smooth swallowing and digestion.