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Head

life science Maturity 11-13 Next article →

A head is a specialized anatomical part of an organism. It typically houses sensory organs like eyes, ears, noses, and mouths. These organs allow an animal to experience sight, hearing, smell, and taste. While very simple animals may lack a head, many bilaterally symmetric organisms possess one. Bilateral symmetry means an organism has matching left and right sides.

Heads develop through an evolutionary process called cephalization. In bilaterally symmetric animals, nervous tissue concentrates at the anterior, or front, region. This concentration forms structures used for processing information. Through biological evolution, sense organs and feeding structures also gather in this anterior area. This collection of parts creates the head. As cephalization progresses, the head incorporates more adjacent body segments. Higher degrees of cephalization result in a head composed of more segments.

Insects provide a detailed look at diverse head structures. A typical insect head includes eyes, antennae, and mouth components. Many insects possess compound eyes, which consist of multiple facets or faces. Some insects also have ocelli, which are single-faceted organs located near the head. Antennae are usually found in pairs between the eyes. These segmented attachments can be filaments or clubbed shapes.

Insect mouths vary based on their specific feeding habits. The labrum acts as an upper lip at the front of the head. Behind the labrum, a pair of mandibles flanks the mouth. These are followed by a pair of maxillae, which include maxillary palps. The labium serves as the lower lip at the back of the mouth. Some insects also have a hypopharynx located between the maxillae. These specialized parts allow insects to process different types of food.

Vertebrate heads have a unique evolutionary history. Scientists have studied how bony skulls evolved from invertebrate chordates like lancelets. One theory suggests the vertebrate head formed by fusing a fixed number of anterior segments. In the 1980s, researchers proposed the "new head hypothesis." This suggests the head is a novelty from the emergence of neural crest and cranial placodes. In 2014, researchers found lancelet tissue that looked like vertebrate skull cartilage. This discovery suggests a possible evolutionary route for the vertebrate head.

The human head is a complex anatomical unit. It consists of the skull, the hyoid bone, and the cervical vertebrae. The skull is divided into the brain case and the facial skeleton. The brain case contains eight bones that enclose the cranial cavity. The facial skeleton contains fourteen bones, including the mandible, or jawbone.

Beethovendeathmask
Beethovendeathmask

Some philosophers, called identists, believe the mind is identical to the brain. John Searle argued that the brain is the only thing in the human head.

Human heads are also central to art and culture. Artists like Leonardo da Vinci used grid structures to draw perfectly proportioned faces. In cuisine, animal heads are often used as offal, or variety meat. For example, Cabeza is a Mexican dish of pit-roasted livestock heads. In Scandinavia, sheep heads are eaten as smalahove or svið.

Flag of Corsica
Flag of Corsica

Heads also appear in heraldry, the study of coats of arms. These can include specific figures like a "man's head" or a "nun's head." Many common English idioms also use the word head, such as "having one's head in the clouds."

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File:Beethovendeathmask.jpg
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Nomada krugii, F, face, Dominican...
File:Flag of Corsica.svg
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