Human head

Human head
Human head
	Thehumanhead drawn byLeonardo da Vinci
Details
Identifiers
Latin	caput
MeSH	D006257
TA98	A01.1.00.001
TA2	98
FMA	7154
	Anatomical terminology [edit on Wikidata]

In human anatomy, theheadis at the top of thehuman body.It supports thefaceand is maintained by theskull,which itself encloses thebrain.

Structure

Anatomy of the human head

The human head consists of a fleshy outer portion, which surrounds the bonyskull.The brain is enclosed within the skull. There are 22 bones in the human head. The head rests on theneck,and the sevencervical vertebraesupport it. The human head typically weighs between 2.3 and 5 kilograms (5.1 and 11.0 lb) Over 98% of humans fit into this range. There have been odd incidences where human beings have abnormally small or large heads. The Zika virus was responsible for underdeveloped heads in the early 2000s.

The face is theanteriorpart of the head, containing theeyes,nose,andmouth.On either side of the mouth, thecheeksprovide a fleshy border to theoral cavity.The ears sit to either side of the head.

Blood supply

The head receives blood supply through the internal and externalcarotid 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 thevertebral arteries,which travel up through the cervical vertebrae.

Nerve supply

Sensory areas of the head, showing the general distribution of the three divisions of the fifth nerve. From Gray's Anatomy 1918

The twelve pairs ofcranial nervesprovide the majority of nervous control to the head. The sensation to the face is provided by the branches of thetrigeminal nerve,the fifthcranial nerve.Sensation to other portions of the head is provided by thecervical nerves.

Modern texts are in agreement about whichareas of the skin are served by which nerves,but there are minor variations in some of the details. The borders designated by diagrams in the 1918 edition ofGray's Anatomyare similar but not identical to those generally accepted today.

The cutaneous innervation of the head is as follows:

Ophthalmic nerve(green)
Maxillary nerve(pink)
Mandibular nerve(yellow)
Cervical plexus(purple)
Dorsal ramiofcervical nerves(blue) and others are in picture which show following in upper column

Function

The head containssensory organs:two eyes, two ears, a nose andtongueinside of the mouth. It also houses thebrain.Together, these organs function as a processing center for the body by relaying sensory information to the brain. Humans can process information faster by having this central nerve cluster.

Society and culture

Forhumans,the front of the head (the face) is the main distinguishing feature between different people due to its easily discernible features, such as eye and hair colors, shapes of the sensory organs, and the wrinkles. Humans easily differentiate between faces because of the brain's predisposition toward facial recognition. When observing a relatively unfamiliar species, all faces seem nearly identical. Human infants are biologically programmed to recognize subtle differences in anthropomorphic facial features.^[1]

Dayak peoplewere feared for their headhunting practices

People who have greater than average intelligence are sometimes depicted in cartoons as having bigger heads as a way of notionally indicating that they have a "larger head". Additionally, inscience fiction,anextraterrestrialhaving a big head is often symbolic of high intelligence. Despite this depiction, advances inneurobiologyhave shown that the functional diversity of the brain means that a difference in overall brain size is only slightly to moderately correlated to differences in overall intelligence between two humans.^[2]

The head is a source for many metaphors andmetonymiesinhuman 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" ), and things that represent some characteristics associated with the head, such as intelligence ( "there are a lot of good heads in this company" ).^[3]

Ancient Greeks had a method for evaluatingsexual attractivenessbased on theGolden ratio,part of which included measurements of the head.^[4]

Headhuntingis the practice of taking andpreserving a person's headafter killing the person. Headhunting has been practiced across the Americas, Europe, Asia, and Oceania for millennia.^[5]

Clothing

A man wearing astraw hat

Headpieces can signify status, origin, religious/spiritual beliefs, social grouping, team affiliation, occupation, or fashion choices.

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, theMiddle East,andSouth Asiahave covered their head 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 religions require men to wear specific head clothing—such as theIslamic taqiyah,Jewish yarmulke,or theSikh turban.The same goes for women with theMuslim hijaborChristiannun'shabit.

Ahatis a head covering that can serve a variety of purposes. Hats may be worn as part of a uniform or used as a protective device, such as ahard hat,a covering for warmth, a covering that meets sensory needs in someneurodivergentpeople, or a fashion accessory. Hats can also be indicative of social status in some areas of the world.

Anthropometry

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 featurehomogeneoussamples and fail to take height and weight into account.^[6]

One study in the United States estimated the average human head circumference to be57 centimetres (22+1⁄2in) in males and55 centimetres (21+3⁄4in) in females.^[7]^{[dubious–discuss]}A British study byNewcastle Universityshowed an average size of 57.2 cm for males and 55.2 cm for females with average size varying proportionally with height^[8]

Macrocephalycan be an indicator of increased risk for some types of cancer in individuals who carry the genetic mutation that causesCowden syndrome.For adults, this refers to head sizes greater than 58 centimeters in men or greater than 57 centimeters in women.^[9]^[10]

References

^"Infants process faces long before they recognize other objects, Stanford vision researchers find".Stanford University.Retrieved2018-11-14.
^Brain Size and Intelligence
^Lakoff and Johnson 1980, 1999
^Pallett PM, Link S, Lee K (January 2010)."New" golden "ratios for facial beauty".Vision Research.50(2): 149–54.doi:10.1016/j.visres.2009.11.003.PMC2814183.PMID 19896961.
^Christine Quigley (13 October 2005).The Corpse: A History.McFarland. pp. 249–251.ISBN 978-0-7864-2449-8.
^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 (October 1992)."Centiles for adult head circumference".Archives of Disease in Childhood.67(10): 1286–7.doi:10.1136/adc.67.10.1286.PMC1793909.PMID 1444530.
^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.
^Mester JL, Tilot AK, Rybicki LA, Frazier TW, Eng C (July 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): 763–8.doi:10.1038/ejhg.2011.20.PMC3137495.PMID 21343951.

Human head

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