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of an Elephant]]
and a Horse placed in a lifelike pose in a museum display]]
of a Frog]]

s and other reptiles]]

of an Ant]]

In biology, a skeleton is a rigid framework that provides protection and structure in many types of animal, particularly those of the phylum Chordata and of the superphylum Ecdysozoa. Exoskeletons are external, as is typical of many invertebrates; they enclose the soft tissues and organs of the body. Exoskeletons may undergo periodic moulting as the animal grows. Endoskeletons are internal, as is typical of many vertebrates; they are usually surrounded by skin and musculature, though they often enclose vital organs. Endoskeletons are attachment points for musculature and act as leverage for movement, and in many animals contain marrow, which produces blood cells. Skeletons may or may not be mineralized - human skeletons are calcified, while shark skeletons are cartilaginous - and may be jointed for flexibility and motility or rigid for structural strength.

The average adult human skeleton has around 206 bones. [1] These bones meet at joints, the majority of which are freely movable. 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.

Contents

The Human Skull

The human skull shapes the head and face, protects the 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:

Cranial bones

The eight 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.

Facial bones

The 14 (mainly 7 on each side) 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. 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.

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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.

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 unossifed 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.

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.

Limbs

A limb (from the Old English lim)[citation needed] is a jointed or prehensile (as octopus tentacles or new world monkey tails), appendage of the human or animal body.

Most animals use limbs for locomotion, such as walking, running, or climbing. Some animals can use their front limbs (or upper limbs in humans) to carry and manipulate objects. Some animals can also use hind limbs for manipulation.

In the human body, the upper and lower limbs are commonly called the arms and the legs. Human legs and feet are specialized for two-legged locomotion; however, most other mammals walk and run on all four limbs. Human arms are weaker, but very mobile, allowing us to reach at a wide range of distances and angles. The arms end in specialized hands that are capable of grasping and fine manipulation of objects. Femur, Humerus, Radius and Ulna, Cranium, Sternum, Clavicle, Fibulu and Tibia, Vertebrae, Scalpula, Pelvic Bone, and Coccyx.

Animal skeletons

References

See also


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

Contents

English

Etymology

From Ancient Greek σκελετός (skeletos), dried up, withered, dried body, parched, mummy), from σκελλώ (skellō), dry, dry up, make dry, parch).

Pronunciation

Noun

Singular
skeleton

Plural
skeletons

skeleton (plural skeletons)

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  1. (anatomy) The system that provides support to an organism, internal and made up of bones and cartilage in vertebrates, external in some other animals.
    • 1883, Robert Louis Stevenson, Treasure Island,
      At the foot of a pretty big pine, and involved in a green creeper, which had even partly lifted some of the smaller bones, a human skeleton lay, with a few shreds of clothing, on the ground.
  2. A frame that provides support to a building or other construction.
  3. A very thin person.
    She lost so much weight while she was ill that she became a skeleton.
  4. (From the sled used, which originally was a bare frame, like a skeleton.) A type of tobogganing in which competitors lie face down, and descend head first (compare luge).
  5. (geometry) The vertices and edges of a polyhedron, taken collectively.
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Synonyms

  • (anatomy): ottomy (obsolete)
  • (type of tobogganing): skeleton tobogganing

Translations

The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Help:How to check translations.

Derived terms

Related terms

See also

Verb

to skeleton (archaic)

  1. to reduce to a skeleton; to skin
  2. to minimize

Esperanto

Noun

skeleton

  1. accusative singular of skeleto

French

Noun

skeleton m.

  1. skeleton (tobogganing)

Simple English

A skeleton is the hard structure that supports the body of a living thing. Skeletons can be inside the body or outside the body. In mammals, which include humans, the skeleton is made of bones. All the bones, when they are joined together, make the "skeletal system" of a body. The skeletal system or "skeleton" is under the skin, the muscle and the tissue of the body. The skeleton supports the skin, muscle and tissue, and all the organs that are inside the body. The skeleton protects important internal organs like the brain, heart and lungs.

  • Creatures that have skeletons inside their bodies are mammals, birds, reptiles and fish. A skeleton that is on the inside is called an endoskeleton.

Contents

Human skeleton

[[File:|thumb|300px|The skeleton of a woman with the scientific names for the bones]] [[File:|thumb|300px|A skeleton from the back]]

The important parts of a human body are the head, the spine, the chest, the abdomen, the arms and hands, and the legs and feet.

Bones of the head

The head bones all together are called the skull.

  • The skull is made of a group of curved bones fitted together like a ball, which protects the brain, the eyes and the inside parts of the ears. The bones of this part of the head, together, are called the cranium.
  • The skull has a top jaw, and a bottom jaw, with teeth in them. The jaws are called the "upper" and "lower" mandibles. The "lower mandible" is moved by strong muscles so that the teeth can bite and chew food.
  • There are several other small bones which make up the face. There are also several small bones in the front and side of the neck.
  • The smallest bones in the body are three tiny bones inside the ear, which vibrate to help a person hear sounds.

Bones of the spine

The spine supports the head, the chest and the structure that carries the arms. It is made of small bones called vertebrae. The spine, all together, is called the spinal column. It is not straight, but has curves that help to support the body, and help the person to move and bend. One bone is a "vertebra". Lots are "vertebrae". The "vertebrae" have different names, depending on the part of the body they are joined to.

  • The neck vertebrae are called cervical vertebrae. (ser-vick-al ver-ta-bray)
  • The chest vertebrae are called thoracic vertebrae. (thor-assic vert-ta-bray)
  • The vertebrae of the "lower back" are called the lumbar vertebrae.
  • The next vertebrae are joined together in a triangular shape called the sacrum. The hip bones are attached to the sacrum and support it.
  • At the bottom of the "sacrum" are some little tail-bones. They are called the coccyx. On many animals the "coccyxal vertebrae" are long, making a tail that the animal can move, but on humans, apes and some other creatures, they are very short.

Bones of the pelvis

This part of the body is made of the sacrum and the two pelvic bones which are joined to it on either side. The pelvic bones are carried by the leg bones, and they support the "spinal column". Each pelvic bone has a strong structure for the leg bone to fit into, so that a person can stand, walk, run and jump. Each pelvic bone spreads into a large flat plate which supports the person's "internal organs". The pelvis of a woman spreads into a wider shape than a man's, so that when the woman is pregnant, the baby is supported by the pelvis, until it is ready to be born. At the bottom of the pelvis is a large opening, big enough for a baby to pass through.

Bones of the chest

The chest is called the thorax, and the vertebrae that are part of it are the thoracic vertebrae. The thorax is made up of long flat curved bones called ribs. At the back, the ribs are joined to the vetebrae. At the front, most of the ribs are joined to the sternum, which is often called the "breast bone". All together, the "thorax" protects the heart, lungs and stomach.

At the top of the "thorax" is the shoulder girdle. This is made of two thin horizontal bones at the front, joined to the "sternum". These two bones are called the clavicles or "collar bones". At the back of the "thorax" are two flat triangular-shaped bones called the scapulae, or "shoulder blades". The "clavicles" and "scapulae" come together on each side to make "shoulders". The bones of the arms fit into sockets (cup-like holes) in the "scapulae".

Bones of the limbs

Arms and legs both have a thicker bone at the top and two thinner bones at the bottom. They both have a rotating joint at the top, and a hinge joint in the middle. The hands and feet have lots of bones and are joined to the arms and legs by small bones with sliding parts.

Bones of the arms

  • The upper bone is the humerus, which sounds like "humorous", so when people bang their elbow, they often say that they bumped their "funny bone".
  • The bone that sticks out at the elbow and runs down the outside of the arm is the ulna.
  • The bone that is on the thumb-side is called the radius. Near the elbow, it is joined to the "ulna" in a way that allows it to rotate. The "radius" and the "ulna" can twist around each other, allowing a person to turn their hand.
  • The small bones of the wrist are called carpals, and the bones inside the hand are called metacarpals.
  • The finger bones are the phalanges.

Bones of the legs

  • The upper bone of the leg, which is the longest bone in the body, is called the femur.
  • The bone at the front of the leg is called the tibia, or "shin bone". It makes the inside ankle bone.
  • The thinner bone at the side of the leg is called the fibula. It makes the ouside ankle bone.
  • The small bones that join the foot to the leg bones and allow it to move are called the tarsals. The bones inside the foot are the metatarsals.
  • The toe bones are called phalanges, like the finger bones.
  • The leg has another bone. At the front of the joint where the "tibia" meets the "femur" is a small round bone like a little shield, to protect the joint. It is called the patella.

Skeletons in culture

Skeletons as symbols

A skeleton, or just a skull, has often been used as a symbol for Death.

  • Skeletons and skulls can be seen carved on many tombs, from ancient times to the 20th century.
  • Skeletons or skulls are often seen in Medieval and Renaissance paintings or stained glass windows, reminding people that life is short.
  • Skeletons or skulls were often used as a sign to frighten people. Skeletons would be left hanging in public places, such as cross-roads or bridges to remind the people of a town that they would be punished by death if they broke the law.
  • Skeletons or skulls were a symbol used by pirates.

Skeletons in popular culture

[[File:|thumb|right|Animated skeletons from La Danse Macabre by Hans Holbein the Younger (1538)]] Skeletons, particularly living skeletons, have often been used in horror stories and comedies.

  • There are stories where skeletons rise from the dead. Things that come back to life are called undead. In these stories, most skeletons are controlled by a person who brings them back to life. These people are called necromancers. A Necromancer uses magic to make the skeleton move and act upon his/her will.

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