The human head consists of a fleshy outer portion surrounding the bony skull, within which sits the brain. The head rests on the neck, and is provided bony support for movement by the seven cervical vertebrae.
The face is the anterior part of the head, containing the sensory organs the eyes, nose and mouth. The cheeks, on either side of the mouth, provide a fleshy border to the oral cavity. To either side of the head sit the ears.
The twelve pairs of cranial nerves provide the majority of nervous control to the head. The sensation to the face is provided by the branches of the trigeminal nerve, a cranial nerve. The sensation to other portions of the head is provided by the cervical nerves.
The head receives blood supply through the internal and external carotid arteries. These supply the area outside of the skull (external carotid artery) and inside of the skull (internal carotid artery). The area inside the skull also receives blood supply from the vertebral arteries, which travel up through the cervical vertebrae .
The head contains numerous sensory organs, including the brain eyes, ears, nose and mouth.
Society and culture
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 and wrinkles. The human head typically weighs between 5 and 11 pounds (2.3 and 5.0 kg). Human faces are easily differentiable to us due to our brains' predispositions toward discriminating human facial forms. When observing a relatively unfamiliar species, all faces seem nearly identical, and human infants are biologically programmed to recognize subtle differences in anthropic facial features.
People who are more intelligent than normal are sometimes depicted in cartoons as having bigger heads, as a way of notionally indicating that they have a "larger brain"; in science fiction, an extraterrestrial having a big head is often symbolic of high intelligence. Outside of this symbolic depiction, however, advances in neurobiology have shown that the functional diversity of the brain means that a difference in overall brain size is not a reliable indicator of how much, if any, difference in overall intelligence exists between two humans.
The head is a source for many metaphors and metonymies in human language, including referring to things typically near the human head ( "the head of the bed"), things physically similar to the way a head is arranged spatially to a body ("the head of the table"), metaphorically ("the head of the class/FBI") and things that represent some characteristic we associate with the head, such as intelligence ("there are a lot of good heads in this company").
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 South 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 Islamic Taqiyah, Jewish yarmulke, or the Sikh turban; or Muslim women, who cover their hair, ears, and neck with a scarf.
People may cover the head for other reasons. A hat is a piece of clothing covering just the top of the head. This may be part of a uniform, such as a police uniform, a protective device such as a hard hat, a covering for warmth, or a fashion accessory.
Different headpieces can also signify status, origin, religious/spiritual beliefs, social grouping, team affiliation, occupation, and/or fashion choices.
While numerous charts detailing head sizes in infants and children exist, most do not measure average head circumference past the age of 21. Reference charts for adult head circumference also generally feature homogeneous samples and fail to take height and weight into account.
One study in the United States estimated the average human head circumference to be 55 centimetres (21 3⁄4 in) in females and 57 centimetres (22 1⁄2 in) in males. An English study showed an average size of 55.2 cm for females and 57.2 cm for males with average size varying proportionally with height
Macrocephaly can be an indicator of increased risk for some types of cancer in individuals who carry the genetic mutation that causes Cowden syndrome. Cowden Syndrome Detection Will Allow For Early Discovery of Cancerous Polyps. Date: December 7, 2010. Principal Investigator: Charis Eng, MD, PhD. Institution: Cleveland Clinic Genomic Medicine.]</ref><ref>Mester, J. L. (2011). "Analysis of prevalence and degree of macrocephaly in patients with germline PTEN mutations and of brain weight in Pten knock-in murine model.". European Journal of Human Genetics. 19 (7): 763. doi:10.1038/ejhg.2011.20.
- Brain Size and Intelligence
- Lakoff and Johnson 1980, 1999
- Nguyen, A.K.D (2012). "Head Circumference in Canadian Male Adults: Development of a Normalized Chart". International Journal of Morphology. 30 (4): 1474–1480. doi:10.4067/s0717-95022012000400033.
- TECHNICAL BRIEF - Relationship Between Head Mass and Circumference in Human Adults. Date: July 20, 2007. Principal Investigator: Randal P. Ching, Ph.D. Institution: University of Washington. Applied Biomechanics Laboratory.
- Bushby, KM; Cole, T; Matthews, JN; Goodship, JA (1992). "Centiles for adult head circumference" (PDF). Arch. Dis. Child. 67: 1286–7. doi:10.1136/adc.67.10.1286. PMC 1793909. PMID 1444530.
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- Campbell, Bernard Grant. Human Evolution: An Introduction to Man's Adaptations, 4th edition (ISBN 0-202-02042-8).