Head

A head is the part of an organism, which usually comprises the eyes, ears, nose and mouth, each of which aid in various sensory functions, such as sight, hearing, smell, and taste. Some very simple animals may not have a head, but many bilaterally symmetric forms do. Heads develop in animals by an evolutionary trend known as cephalization. In bilaterally symmetrical animals, nervous tissues concentrate at the anterior region, forming structures responsible for information processing. Through biological evolution, sense organs and feeding structures also concentrate into the anterior region; these collectively form the head.

Human head

The human head is an anatomical unit that consists of the skull, hyoid bone and cervical vertebrae. The term "skull" collectively denotes the mandible (lower jaw bone) and the cranium (upper portion of the skull that houses the brain). The skull can also be described as being composed of the cranium, which encloses the cranial cavity, and the facial skeleton (includes the mandible). There are eight bones in the cranium and fourteen in the facial skeleton.

Head (watercraft)

The head (or heads) is a ship's toilet. The name derives from sailing ships in which the toilet area for the regular sailors was placed at the head or bow of the ship.

Design

In sailing ships, the toilet was placed in the bow for two reasons. Firstly, since most vessels of the era could not sail directly into the wind, the winds came mostly across the rear of the ship, placing the head essentially downwind. Secondly, if placed somewhat above the water line, vents or slots cut near the floor level would allow normal wave action to wash out the facility. Only the captain had a private toilet near his quarters, at the stern of the ship in the quarter gallery.

In many modern boats, the heads look similar to seated flush toilets but use a system of valves and pumps that brings sea water into the toilet and pumps the waste out through the hull in place of the more normal cistern and plumbing trap to a drain. In small boats the pump is often hand operated. The cleaning mechanism is easily blocked if too much toilet paper or other fibrous material is put down the pan.

Head (music)

In its broadest sense, the head of a piece of music is its main theme, particularly in jazz, where the term takes on a more specific set of connotations. In other types of music, "head" may refer to the first or most prominent section of a song. The term may, though obtusely, be applied to classical music, insofar as classical pieces generally bear similar thematic elements, but the preferred term in this instance is (main) theme or subject. The term "head" is most often used in jazz and may refer to the thematic melody, an instance of it in a performance of the song, or a more abstract compilation of ideas as to what the song is. It may also, though uncommonly, refer to the first section of the melody, or the theme riff in the melody.

There is a slightly related musical direction, D.C. or da capo (Italian, from head), which means to go back to the very beginning of the sheet music and play to the end, typically ignoring all repeat signs.

What's in a head

The idea a head represents comprises a combination of elements. No one piece of written music defines what the "head" of many jazz tunes really is, but a boiler-plate jazz chart, which is often only a page long in large print, will tell you: