Neurovasculature of the Head

Olfaction represents an ancient, evolutionarily critical physiologic system. Humans have the ability to detect and discriminate at least 10,000 different odorants. The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction is responsible for the detection of hazards, pheromones, and food.

The head and neck examination is the portion of the physical examination done to observe for signs of head and neck disease or illness. The head and neck examination consists of inspection, palpation, and auscultation. The information gathered from the physical examination of the head and neck, along with the information from the history, is used by the physician to generate a differential diagnosis and treatment plan for the patient.

There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. Some CNs are involved in special senses, like vision, hearing, and taste, and others are involved in muscle control of the face. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain.

Blood supply to the brain can be divided into an anterior and a posterior circulation, which interconnect to form the circle of Willis. The anterior circulation is derived from the internal carotid arteries and consists mainly of the anterior and middle cerebral arteries. The posterior circulation is derived from the vertebral arteries and consists primarily of the cerebellar and posterior cerebral arteries. The primary venous drainage of the brain occurs via the internal jugular vein.