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In biology, the skeleton or skeletal system is a strong framework that supports the body. External rigid frameworks, such as those found in some invertebrates (e.g. insects), are termed exoskeletons. Internal rigid frameworks, such as those found in most vertebrates (e.g. mammals), are termed endoskeletons. A skeleton is usually the internal structure of a thing. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Front view of a skeleton of an adult human Back view of a skeleton of an adult human The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. ... Endoskeleton of a swordfish An endoskeleton is an internal support structure of an animal. ... For the song by Girls Aloud see Biology (song) Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: Βιολογία - βίος, bio, life; and λόγος, logos, speech lit. ... Invertebrate is an English word that describes any animal without a spinal column. ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera... An exoskeleton is an external anatomical feature that supports and protects an animals body, in contrast to the internal endoskeleton of, for example, a human. ... This article does not cite any references or sources. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... Endoskeleton of a swordfish An endoskeleton is an internal support structure of an animal. ...


The average adult human skeleton comprises 206 bones [1] These bones meet at joints, the majority of which are freely movable, making the skeleton flexible and mobile. The skeleton also contains cartilage for elasticity. Ligaments are strong strips of fibrous connective tissue that hold bones together at joints, thereby stabilizing the skeleton during movement. Front view of a skeleton of an adult human Back view of a skeleton of an adult human The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. ... This article is about the skeletal organs. ... This article is about a joint in zootomical anatomy. ... Cartilage is a type of dense connective tissue. ... A ligament is a short band of tough fibrous connective tissue composed mainly of long, stringy collagen molecules. ...

Contents

Main functions

A skeleton provides "cages" to protect the delicate organs. For example: the ribcage helps protect the lungs, heart, etc. Moreover, it gives muscles "sides" or edges to attach to (through tendons). It also maintains balance, and supports the body's shape. But all these functions are perhaps secondary to the primary function of locomotion. The bones allow the muscles of the body to move the limbs. Bones come in different sizes; the longest bone is the femur, and the shortest, the stapes. The outer layer of bones are called compact bones, and the middle, called spongy or cancellous bone, which are hollow and contain bone marrow. Joints of bones are held together by ligaments, which are fine fibers attaching to each bone at joints. In order for bones to not scrape against each other, slippery cartilage and synovial fluid are covered atop the bones. Most bones have three layers. The inner most layer is the bone marrow. The femur or thigh bone is the longest, most voluminous, and strongest bone of the mammalian bodies. ... The stapes or stirrup is the stirrup-shaped small bone or ossicle in the middle ear which attaches the incus to the fenestra ovalis, the oval window which is adjacent to the vestibule of the inner ear. ... For the Dir en grey album, see The Marrow of a Bone. ...


The Skull

The human skull shapes the head and face, protects the fragile brain, and houses and protects special sense organs for taste, smell, hearing, vision, and balance. It is constructed from 22 bones, 21 of which are locked together by immovable joints, to form a structure of great strength.


The bony framework of the head is called the skull, and it is subdivided into 2 parts, namely; For other uses of Skull, see Skull (disambiguation). ...


1. Cranial Bones. The 8 bones of the cranium support, surround and protect the brain within the cranial cavity. They form the roof, sides, and back of the cranium, as well as the cranial floor on which the brain rests. The frontal bones and the parietal bones form the roof and sides of the cranium. Two in the temporal bone, the external auditory meatus, directs sounds into the inner part of the ear that is encased within, and which contains three small, linked bones called ossicles. The occipital bones forms the posterior part of the cranium and much of the cranial floor. The occipital bone has a large opening, the foramen magnum, through which the brain connects to the spinal cord. The occipital condyles articulate with the atlas (first cervical vertebra), enabling nodding movements of the head. The ethmoid bone forms part of the cranial floor, the medial walls of the orbits, and the upper parts of the nasal septum, which divides the nasal cavity vertical into left and right sides, The sphenoid bone, which is shaped like a bat's wings, acts as a keystone by articulating with and holding together, all the other cranial bones. Cranium can mean: The brain and surrounding skull, a part of the body. ... For other uses, see Brain (disambiguation). ... The frontal bone is a bone in the human skull that resembles a cockle-shell in form, and consists of two portions: a vertical portion, the squama frontalis, corresponding with the region of the forehead. ... The parietal bones (os parietale) are bones in the human skull and form, by their union, the sides and roof of the cranium. ... Anatomy of the human ear. ... The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ... The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the cranium, is trapezoid in shape and curved on itself. ... In anatomy, in the occipital bone, the foramen magnum (Latin: great hole) is one of the several oval or circular apertures in the base of the skull (the foramina), through which the medulla oblongata (an extension of the spinal cord) enters and exits the skull vault. ... The Spinal cord nested in the vertebral column. ... Your skull is in your back (this is obviously not true, I was just testing the website to see if it really works) The ethmoid bone (os ethmoidale) is a bone in the skull that separates the nasal cavity from the brain. ... The sphenoid bone (from Greek sphenoeides, wedgelike) is a bone situated at the base of the skull in front of the temporals and basilar part of the occipital bone. ...


2. Facial Bones The 14 facial bones form the framework of the face; provide cavities for the sense organs of smell, taste, and vision; anchor the teeth; form openings for the passage of food, water, and air; and provide attachment points for the muscles that produce facial expressions. Two maxillae form the upper jaw, contain sockets for the 16 upper teeth, and link all other facial bones apart from the mandible (lower jaw). Two zygomatic bones (cheekbones), form the prominences of the cheeks and part of the lateral margins of the orbits. Two lacrimal bones form part of the medial wall of each orbit. Two nasal bones form the bridge of the nose.ss Two palatine bones from the posterior side walls of the nasal cavity and posterior part of the hard palate. Two inferior nasal conchae form part of the lateral wall of the nasal cavity. The vomer forms part of the nasal septum. The mandible, the only skull bone that is able to move, articulates with the temporal bone allowing the mouth to open and close, and provides anchorage for the 16 lower teeth. The maxillae are the largest bones of the face, except for the mandible, and form, by their union, the whole of the upper jaw. ... The mandible (from Latin mandibÅ­la, jawbone) or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face. ... The inferior nasal concha (Concha Nasalis Inferior; Inferior Turbinated Bone) extends horizontally along the lateral wall of the nasal cavity [Fig. ... The nasal cavity (or nasal fossa) is a large air-filled space above and behind the nose in the middle of the face. ... The vomer bone is one of the unpaired facial bones of the skull. ... The nasal septum separates the left and right airways in the nose, dividing the two nostrils. ... The mandible (from Latin mandibÅ­la, jawbone) or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face. ...


Sinuses

Sinuses are air-filled bubbles found in the frontal, sphenoid, ethmoid, and paired maxillae, clustered around the nasal cavity. These spaces reduce the overall weight of the skull. A sinus is a pouch or cavity in any organ or tissue, or an abnormal cavity or passage caused by the destruction of tissue. ...


Skull development

In the fetus, skull bones are formed by intramembranous ossification. A fibrous membrane ossifies to form skull bones linked by areas of as yet unossifued areas of membrane called fontanelles. At birth, these flexible areas allow the head to be slightly compressed, and permit brain growth during early infancy. These are named the anterior (Frontal) fontanelle, posterior (Occipital) fontanelle, anterolateral (Sphenoidal)fontanelle, and the posterolateral (Mastoid) fontanelle. Osteoblasts and osteoclasts on trabecula of lower jaw of calf embryo. ... In human anatomy, a fontanelle (or fontanel) is one of two soft spots on a newborn humans skull. ...


Backbone and ribs

Together with the sternum and ribs, the backbones (also known as the vertebral column, spinal column, or spine) forms the skeleton of the trunk. The backbone consists of a chain of irregular bones called vertebrae that meet at slightly movable joints. Each joint permits only limited movement, but collectively the joints give the backbone considerable flexibility enabling it to rotate, and to bend anteriorly, posteriorly, and laterally. The average backbone makes up about 40 percent of body height. It extends from the skull to its anchorage in the pelvic girdle, where it transmits the weight of the head and trunk to the lower limbs. It also supports the skull; encloses and protects the delicate spinal cord; and provides an attachment point for the ribs, and for the muscles and ligaments that support the trunk of the body. The sternum (from Greek στέρνον, sternon, chest) or breastbone is a long, flat bone located in the center of the thorax (chest). ... This article is about the bones called ribs. ... The vertebral column seen from the side Different regions (curvatures) of the vertebral column The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... A diagram of a thoracic vertebra. ... Human male pelvis, viewed from front Human female pelvis, viewed from front The pelvis is the bony structure located at the base of the spine (properly known as the caudal end). ...


Intervertebral discs

Intervertebral discs are found between adjacent vertebrae from the second cervical vertebra (axis) to the sacrum. Each disc has an inner soft, pulp nucleus coverbrous covering of fibrous cartilage. Each disc forms a strong, slightly movable joint. Collectively, discs cushion vertebrae against vertical shocks, and allow various movements of the backbone. Intervertebral discs lie in between adjacent vertebrae in the spine. ... For the record label, see Sacrum Torch. ...


Vertebral curves

A normal backbone has four curves that give it an S-shape. The cervical and lumbar curves are convex anteriorly, while the thoracic and sacral curves are concave anteriorly. The S-shape allows the backbone to function as a spring rather than a flexible rod, thereby absorbing shock during walking and running; enhancing the strength and flexibility of the backbone; and facilitating balance when upright by placing the trunk directly over the feet.


Regions of the backbone

An adult backbone consists of 26 vertebrae of which two, the sacrum and coccyx, are composites consisting of vertebrae that fuse during childhood. The backbone has five sections. Seven small cervical vertebrae form the neck,which is the most flexible part of the backbone. The uppermost cervical vertebra, the atlas articulates with the occipital condyle of the skull to enable nodding movements of the head; articulation of the atlas with the axis, the second cervical vertebra, produces shaking movement of the head. Twelve thoracic vertebrae each articulate with a pair of ribs. Five large lumbar vertebrae form the hollow small of the back and bear most of the weight of the head and trunk. The triangular sacrum, made of five fused bones, forms a strong anchorage for the pelvic girdle, with which it forms the pelvis. The coccyx, or tailbone, consists of four fused vertebrae. For the record label, see Sacrum Torch. ... The coccyx is formed of up to five vertebrae. ... A political and physical map of the world For other uses, see Atlas (disambiguation). ... In anatomy, the second cervical vertebra (C2) of the spine is named the axis or epistropheus. ... A diagram of a thoracic vertebra. ... A typical thoracic vertebra The thoracic vertebrae (vertebrae thoracales) compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. ... The lumbar vertebrae are the largest segments of the movable part of the vertebral column, and are characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body. ... For the record label, see Sacrum Torch. ... Human male pelvis, viewed from front Human female pelvis, viewed from front The pelvis is the bony structure located at the base of the spine (properly known as the caudal end). ... The coccyx is formed of up to five vertebrae. ...


Bony thorax

The cone-shaped bony thorax surrounds the thoracic cavity, and is formed by 12 thoracic vertebrae posteriorly, 24 ribs laterally, and the sternum and costal cartilages anteriorly. Its cage-like structure protects the thoracic and upper abdominal organs, supports the pectoral girdles and upper limbs, and facilitates breathing. A typical thoracic vertebra The thoracic vertebrae (vertebrae thoracales) compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. ... The sternum (from Greek στέρνον, sternon, chest) or breastbone is a long, flat bone located in the center of the thorax (chest). ... The costal cartilages are bars of hyaline cartilage which serve to prolong the ribs forward and contribute very materially to the elasticity of the walls of the thorax. ... The pectoral girdle is the set of bones which connect the upper limb to the axial skeleton on each side. ...


Ribs

The ribs are curved, flat bones with a slightly twisted shaft. The 12 pairs of ribs form a ribcage that protects the heart, lungs, major blood vessels, stomach, liver, etc. At its posterior end, the head of each rib articulates with the facets on the centra of adjacent vertebrae, and with a facet on a transverse process. These vertebrocostal joints are plane joints that allow gliding movements. At their anterior ends, the upper ten pairs of ribs attach directly or indirectly to the sternum by flexible costal cartilages.. Together, vertebrocostal joints and costal cartilages give the ribcage sufficient flexibility to make movements up and down during breathing. Ribs 1-7 are called "true ribs". Ribs 8-12 are called "false ribs" of which ribs 11 and 12 are "floating" ribs that articulate with the sternum indirectly via the costal cartilage of another rib or not. This article is about the bones called ribs. ...


References

  1. ^ Human Skeleton, EnchantedLearning.com, 2008-05-07.

2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 127th day of the year (128th in leap years) in the Gregorian calendar. ...

See also

Human skeleton Front view of a skeleton of an adult human Back view of a skeleton of an adult human The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. ...

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