head

The vertebrate head contains the brain and brainstem (protected by the cranial vault), cranial nerves (12 pairs in humans), major sense organs (eyes, ears, nose, tongue), the jaw apparatus for feeding, teeth, major blood vessels (carotid arteries, jugular veins), and in many species, the trachea and esophageal openings.

The head is demarcated from the neck at the base of the skull (craniocervical junction), where the foramen magnum allows the brainstem to continue as the spinal cord. The atlas (C1) and axis (C2) vertebrae support the head and enable its rotational movements.

Cephalization is the evolutionary tendency for nervous tissue, sensory organs, and feeding apparatus to concentrate in an anterior head region. This improves coordination of the body's leading end — the first part to encounter the environment — providing evolutionary advantages in prey detection, predator avoidance, and feeding efficiency.