Head (anatomy)

In anatomy, the head of an animal is the rostral part (from anatomical position) that usually comprises the brain, eyes, ears, nose, and mouth (all 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.

Bilateral symmetry
The very simplest animals do not have a head, but many bilaterally symmetric forms do. Vertebrates in particular have distinctive heads, which is associated with the development of the neural crest in the developing vertebrate embryo. The contents of the vertebrate head are protected by an enclosure of bone called the skull, which is attached to the spine. The head is the most complex anatomical construct in the anatomy of vertebrates.

Cultural import
For humans, the head and particularly the face are the main distinguishing feature between different people, due to their easily discernible features such as hair and eye color, nose, eye and mouth shapes, wrinkles, etc.

People who are more intelligent than normal are sometimes depicted in cartoons as having bigger heads, as a way of indicating that they have more brains; in science fiction, an extraterrestrial having a big head is often symbolic of high intelligence. However, minor changes in brain size do not have much effect on intelligence in humans. 

In English slang, sometimes a boastful individual is said to have a "big head."

The weight of the average adult human head is about 3.6 kilograms or 8 pounds.

Clothing
In many cultures, covering the head is seen as a sign of respect. Often, some or all of the head must be covered and veiled when entering holy places, or places of prayer. For many centuries, women in Europe, the Middle East, and parts of Asia, have covered their hair as a sign of modesty. This trend has changed drastically in Europe in the 20th Century, although is still observed in other parts of the world. In addition, a number of religious paths require men to wear specific head clothing- such as the Jewish yarmulke, or the sikh turban; or Muslim women, who cover their hair, ears and neck with a scarf.

Different headpieces can also signify status, origin, religious/spiritual beliefs, social grouping, occupation, and fashion choices.

Pseudoscientific study of the human head
Because the human head is the location of the thinking organ, it has been the subject of intense study. Some of the early modern research on the human head by German physician Franz Joseph Gall has resulted in the pseudoscience of phrenology, which reached its peak in the 19th century. It attributes character traits and mental abilities to the shape of the head. The measurement of the human head and skull, known as craniometry, gained popularity at the same time. Some, notably in Nazi Germany, have used these measurements and other comparative research as the underpinnings of racist, pseudoscientific theories.

The procedure of trepanation has also been advocated and practiced for pseudoscientific reasons.