**Question:** All is true about branches of internal carotid artery except:

A. The internal carotid artery (ICA) is a major artery in the neck that supplies blood to the brain and head.
B. Its primary function is to deliver oxygenated blood to the brain.
C. The carotid sinus serves as the main control center for blood pressure regulation in response to changes in blood flow.
D. The external carotid artery (ECA) is the primary artery supplying blood to the face and neck.

**Core Concept:**

The internal carotid artery is a major vessel in the neck that plays a crucial role in supplying oxygenated blood to the brain and head. It is one of the two primary carotid arteries, the other being the external carotid artery. The internal carotid artery is part of the larger systemic arterial system and is crucial for maintaining adequate cerebral perfusion and overall systemic blood pressure regulation.

**Why the Correct Answer is Right:**

D. The correct answer (D) is right because the external carotid artery (ECA) is responsible for supplying blood to the face and neck, not the internal carotid artery (ICA). The ICA primarily supplies blood to the brain and head, ensuring adequate perfusion and blood flow to these vital areas.

**Why Each Wrong Option is Incorrect:**

A. While the ICA does play a significant role in supplying blood to the brain and head, stating that its primary function is solely to deliver oxygenated blood is an oversimplification. The correct answer is that it is one of the main arteries supplying blood to these areas, but its primary function is within the systemic arterial system.

B. Like option A, stating that the primary function of the internal carotid artery is to deliver oxygenated blood to the brain is an oversimplification. The correct answer is that the ICA plays a crucial role in supplying blood to the brain and head, but its primary function is within the systemic arterial system.

C. The carotid sinus is part of the baroreceptor system, which plays a significant role in regulating blood pressure and maintaining homeostasis. It is not directly related to the internal carotid artery.

**Clinical Pearls:**

The internal carotid artery is a vital component of the systemic arterial system, ensuring adequate blood flow to the brain and head. While its primary function is part of the systemic arterial system, it is essential for maintaining brain perfusion and overall cardiovascular stability. Understanding the role of the internal carotid artery and its connections to the brain and head is crucial for medical professionals to accurately diagnose and treat neurological and cardiovascular conditions.