Heads of humans are sometimes blazoned simply as a "man's head", but are far more frequently described in greater detail, either characteristic of a particular race or nationality (such as Moors' heads, Saxons' heads, Egyptians' heads or Turks' heads), or specifically identified (such as the head of Moses in the crest of Hilton, or the head of St. The heads of humans and other animals are commonly recurring charges in heraldry. In 2014, a transient larva tissue of the lancelet was found to be virtually indistinguishable from the neural crest-derived cartilage which forms the vertebrate skull, suggesting that persistence of this tissue and expansion into the entire headspace could be a viable evolutionary route to formation of the vertebrate head. In the 1980s, the "new head hypothesis" was proposed, suggesting that the vertebrate head is an evolutionary novelty resulting from the emergence of neural crest and cranial placodes. With the progressive development of cephalization, "the head incorporates more and more of the adjacent segments into its structure, so that in general it may be said that the higher the degree of cephalization the greater is the number of segments composing the head". The head segments also lose most of its systems except for the nervous system. In some cases, segments or a portion of the segments disappear. Īccording to Hyman (1979), the evolution of the head in the vertebrates has occurred by the fusion of a fixed number of anterior segments, in the same manner as in other "heteronomously segmented animals". Though invertebrate chordates – such as the tunicate larvae or the lancelets – have heads, there has been a question of how the vertebrate head, characterized by a bony skull clearly separated from the main body, might have evolved from the head structures of these animals. Vertebrates and the "new head hypothesis" There is also an extra mouth part in some insects which is termed as hypopharynx which is usually located between the maxillac. At the back side of the mouth is the labium or lower lip. A pair of mandible is found on backside of the labrum flanking the side of the mouth, succeeded by a pair of maxillae each of which is known as maxilliary palp. Labrum is the "upper lip" which is in the front area of the head and is the most exterior part.
Insects have mouth parts in various shapes depending on their feeding habits.
These are in varying shapes and sizes, in the form of filaments or in different enlarged or clubbed form. Īntennae on the insect's head is found in the form of segmented attachments, in pairs, that are usually located between the eyes. In some cases, the eyes may be seen as marks on the dorsal or located near or toward the head, two or three ocelli (single faceted organs). In many other types of insects the compound eyes are seen in a "single facet or group of single facets". Eyes in the head found, in several types of insects, are in the form of a pair of compound eyes with multiple faces. As these components differ substantially from insect to insect, they form important identification links. Ī typical insect head is composed of eyes, antennae, and components of mouth. Henry Bennet-Clark has stated that the head encloses billions of "miniagents and microagents (with no single Boss)". Philosopher John Searle asserts his identist beliefs, stating "the brain is the only thing in the human head". Proponents of identism believe that the mind is identical to the brain. Though the number of muscles making up the face is generally consistent between sculptures, the shape of the muscles varies widely based on the function, development, and expressions reflected on the faces of the subjects. Sculptures of human heads are generally based on a skeletal structure that consists of a cranium, jawbone, and cheekbone. The term "skull" collectively denotes the mandible (lower jaw bone) and the cranium (upper portion of the skull that houses the brain). The human head is an anatomical unit that consists of the skull, hyoid bone and cervical vertebrae. Main articles: Human head and Head and neck anatomy
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