Many anatomical terms descriptive of bone are defined in anatomical terminology, and are often derived from Greek and Latin.

Bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...

in the human body is categorized into

long bone The long bones are those that are longer than they are wide. They are one of five types of bones: long, Short bone, short, Flat bone, flat, Irregular bone, irregular and Sesamoid bone, sesamoid. Long bones, especially the femur and tibia, are subj ...

short bone Short bones are designated as those bones that are as wide as they are long. Their primary function is to provide support and stability with little to no movement. They are one of five types of bones: short, long, flat, irregular and sesamoid. ...

, flat bone,

irregular bone The irregular bones are bones which, from their peculiar form, cannot be grouped as long, short, flat or sesamoid bones. Irregular bones serve various purposes in the body, such as protection of nervous tissue (such as the vertebrae protect the sp ...

and

sesamoid bone In anatomy, a sesamoid bone () is a bone embedded within a tendon or a muscle. Its name is derived from the Arabic word for ' sesame seed', indicating the small size of most sesamoids. Often, these bones form in response to strain, or can be pres ...

Types of bone

Long bones

A long bone is one that is cylindrical in shape, being longer than it is wide. However, the term describes the shape of a bone, not its size, which is relative. Long bones are found in the arms (

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

) and legs (

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

), as well as in the fingers ( metacarpals,

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

) and toes ( metatarsals, phalanges). Long bones function as levers; they move when muscles contract. They are responsible for the body's height.

Short bones

A short bone is one that is cube-like in shape, being approximately equal in length, width, and thickness. The only short bones in the human skeleton are in the carpals of the wrists and the tarsals of the ankles. Short bones provide stability and support as well as some limited motion.

Flat bones

The term “flat bone” is something of a misnomer because, although a flat bone is typically thin, it is also often curved. Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs. Flat bones do not have a medullary cavity because they are thin.

Irregular bones

An irregular bone is one that does not have an easily classified shape and defies description. These bones tend to have more complex shapes, like the

vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

that support the spinal cord and protect it from compressive forces. Many facial bones, particularly the ones containing sinuses, are classified as irregular bones.

Sesamoid bones

A sesamoid bone is a small, round bone that, as the name suggests, is shaped like a sesame seed. These bones form in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome compressive forces. Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. The only type of sesamoid bone that is common to everybody is the kneecap (''patella'', pl. ''patellae'') which is also the largest of the sesamoid bones.

Protrusions

Rounded

A '' condyle'' is the round prominence at the end of a bone, most often part of a joint – an articulation with another bone. The ''

epicondyle An epicondyle () is a rounded eminence on a bone that lies upon a condyle ('' epi-'', "upon" + ''condyle'', from a root meaning "knuckle" or "rounded articular area"). There are various epicondyles in the human skeleton, each named by its anatomic ...

'' refers to a projection near a condyle, particularly the medial epicondyle of the humerus. These terms derive from Greek. , from "knuckle" ( el, kondylos), with "epi" referring to "Upon". An ''eminence'' refers to a relatively small projection or bump, particularly of bone, such as the medial eminence. A ''process'' refers to a relatively large projection or prominent bump, as does a ''promontory'' such as the sacral promontory. Both ''tubercle'' and ''tuberosity'' refer to a projection or bump with a roughened surface, with a "tubercle" generally smaller than a "tuberosity". These terms are derived from ''

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...

'' ( la, swelling)., as is also ''

protuberance Protuberance may refer to: * Mental protuberance * Occipital protuberances, of which may refer to ** Internal occipital protuberance ** External occipital protuberance * Laryngeal protuberance, also known as Adam's apple See also * Anatomical t ...

'', which occasionally is synonymous with "tuberosity". A ''ramus'' ( la, branch) refers to an extension of bone, such as the ramus of the mandible in the

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

or Superior pubic ramus. Ramus may also be used to refer to nerves, such as the ramus communicans. A ''facet'' refers to a small, flattened articular surface.

Pointed

A ''line'' refers to a long, thin projection, often with a rough surface. ''Ridge'' and ''crest'' refer to a long, narrow line. Unlike many words used to describe anatomical terms, the word ''ridge'' is derived from

Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlement of Britain, Anglo ...

. A ''spine'', as well as referring to the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

, may be used to describe a relatively long, thin projection or bump.

Special

These terms are used to describe bony protuberances in specific parts of the body. The '' Malleolus'' ( la, "small hammer") is the bony prominence on each side of the ankle. These are known as the medial and lateral malleolus. Each leg is supported by two bones, the

on the inner side (medial) of the leg and the

on the outer side (lateral) of the leg. The ''medial malleolus'' is the prominence on the inner side of the ankle, formed by the lower end of the tibia. The ''lateral malleolus'' is the prominence on the outer side of the ankle, formed by the lower end of the fibula. The '' trochanters'' are parts of the femur, to which muscles attach. It may refer to the greater,

lesser Lesser, from Eliezer (, "Help/Court of my God"), is a surname. Notable people with the surname include: * Adolf Lesser (1851–1926), German physician * Aleksander Lesser (1814–1884), Polish painter and art critic * Anton Lesser (born 1952), Bri ...

, or third trochanter

Cavities

Openings

The following terms are used to describe cavities that connect to other areas: A ''

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

'' is any opening, particularly referring to those in

bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...

. Foramina inside the

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anima ...

humans Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

and other animals typically allow

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

s, arteries,

vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

s, or other structures to connect one part of the body with another. A ''canal'' is a long, tunnel-like foramen, usually a passage for notable nerves or blood vessels.

Blind-ended

The following terms are used to describe cavities that do not connect to other areas: A ''

fossa Fossa may refer to: Animals * Fossa (animal), the common name of a carnivoran mammal of genus ''Cryptoprocta'' endemic to Madagascar * ''Fossa'', the Latin genus name of the Malagasy civet, a related but smaller mammal endemic to Madagascar Pla ...

'' (from the Latin "''fossa''", ditch or trench) is a depression or hollow, usually in a bone, such as the

hypophyseal fossa The sella turcica (Latin for 'Turkish saddle') is a saddle-shaped depression in the body of the sphenoid bone of the human skull and of the skulls of other hominids including chimpanzees, gorillas and orangutans. It serves as a cephalometric ...

, the depression in the

sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of occipital bone, basilar part of the occipital bone. The sphenoid bone is one of the seven bones ...

.Venieratos D, Anagnostopoulou S, Garidou A., A new morphometric method for the sella turcica and the hypophyseal fossa and its clinical relevance. Folia Morphol (Warsz). 2005 Nov; 64(4): 240–47. A '' meatus'' is a short canal that opens to another part of the body. A ''

fovea Fovea () (Latin for "pit"; plural foveae ) is a term in anatomy. It refers to a pit or depression in a structure. Human anatomy *Fovea centralis of the retina * Fovea buccalis or Dimple * Fovea of the femoral head * Trochlear fovea of the fr ...

'' ( la, pit) is a small pit, usually on the head of a bone. An example of a ''fovea'' is the

fovea capitis The femoral head (femur head or head of the femur) is the highest part of the thigh bone (femur). It is supported by the femur neck, femoral neck. Structure The head is globular and forms rather more than a hemisphere, is directed upward, medialw ...

of the head of the femur.

Walls

The following terms are used to describe the walls of a cavity: A ''

labyrinth In Greek mythology, the Labyrinth (, ) was an elaborate, confusing structure designed and built by the legendary artificer Daedalus for King Minos of Crete at Knossos. Its function was to hold the Minotaur, the monster eventually killed by the ...

'' refers to the bony labyrinth and membranous labyrinth, components of the inner ear, due to their fine and complex structure. A '' sinus'' refers to a bony cavity, usually within the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

Joints

A joint, or articulation is the region where adjacent bones contact each other, for example the elbow, shoulder, or costovertebral joint. Terms that refer to joints include: * ''articular process'', referring to a projection that contacts an adjacent bone. * ''suture'', referring to an articulation between cranial bones.

Features of long bones

Gross features

Bones are commonly described with the terms ''head'', ''neck'', ''shaft'', ''body'' and ''base'' The ''head'' of a bone usually refers to the distal end of the bone. The shaft refers to the elongated sections of

, and the ''neck'' the segment between the head and shaft (or body). The end of the long bone opposite to the head is known as the ''base''.

Internal regions

Internal and external

The cortex of a bone is used to refer to its outer layers, and medulla used to refer to the inner surface of the bone.

Red marrow Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoietic ce ...

, in which blood is formed is present in

spongy bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and ...

as well as in the medullary cavity, while the fatty yellow marrow is present primarily in the medullary cavity.

Notes

References

''This Wikipedia entry incorporates text from the freely licensed Connexion

edition of Anatomy & Physiolog

text-book by OpenStax College'' ;Books * {{cite book , editor = J. A. Simpson , title = The Oxford English dictionary. , url = https://archive.org/details/oxfordenglishdic12simp , url-access = registration , year = 1989 , publisher=Clarendon Press , location=Oxford , isbn=9780198611868 , ref={{harvid, OED, 1989 Skeletal system Human anatomy Anatomy