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By the end of this section, you will be able to:
  • Classify bones according to their shapes
  • Describe the function of each category of bones

The 206 bones that compose the adult skeleton are divided into five categories based on their shapes ( [link] ). Their shapes and their functions are related such that each categorical shape of bone has a distinct function.

Classifications of bones

This illustration shows an anterior view of a human skeleton with call outs of five bones. The first call out is the sternum, or breast bone, which lies along the midline of the thorax. The sternum is the bone to which the ribs connect at the front of the body. It is classified as a flat bone and appears somewhat like a tie, with an enlarged upper section and a thin, tapering, lower section. The next callout is the right femur, which is the thigh bone. The inferior end of the femur is broad where it connects to the knee while the superior edge is ball-shaped where it attaches to the hip socket. The femur is an example of a long bone. The next callout is of the patella or kneecap. It is a small, wedge-shaped bone that sits on the anterior side of the knee. The kneecap is an example of a sesamoid bone. The next callout is a dorsal view of the right foot. The lateral, intermediate and medial cuneiform bones are small, square-shaped bones of the top of the foot. These bones lie between the proximal edge of the toe bones and the inferior edge of the shin bones. The lateral cuneiform is proximal to the fourth toe while the medial cuneiform is proximal to the great toe. The intermediate cuneiform lies between the lateral and medial cuneiform. These bones are examples of short bones. The fifth callout shows a superior view of one of the lumbar vertebrae. The vertebra has a kidney-shaped body connected to a triangle of bone that projects above the body of the vertebra. Two spines project off of the triangle at approximately 45 degree angles. The vertebrae are examples of irregular bones.
Bones are classified according to their shape.

Long bones

A long bone    is one that is cylindrical in shape, being longer than it is wide. Keep in mind, however, that the term describes the shape of a bone, not its size. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges). Long bones function as levers; they move when muscles contract.

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 somewhat 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.

Irregular bones

An irregular bone    is one that does not have any easily characterized shape and therefore does not fit any other classification. These bones tend to have more complex shapes, like the vertebrae 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 patellae (singular = patella) are the only sesamoid bones found in common with every person. [link] reviews bone classifications with their associated features, functions, and examples.

Bone Classifications
Bone classification Features Function(s) Examples
Long Cylinder-like shape, longer than it is wide Leverage Femur, tibia, fibula, metatarsals, humerus, ulna, radius, metacarpals, phalanges
Short Cube-like shape, approximately equal in length, width, and thickness Provide stability, support, while allowing for some motion Carpals, tarsals
Flat Thin and curved Points of attachment for muscles; protectors of internal organs Sternum, ribs, scapulae, cranial bones
Irregular Complex shape Protect internal organs Vertebrae, facial bones
Sesamoid Small and round; embedded in tendons Protect tendons from compressive forces Patellae

Chapter review

Bones can be classified according to their shapes. Long bones, such as the femur, are longer than they are wide. Short bones, such as the carpals, are approximately equal in length, width, and thickness. Flat bones are thin, but are often curved, such as the ribs. Irregular bones such as those of the face have no characteristic shape. Sesamoid bones, such as the patellae, are small and round, and are located in tendons.

Questions & Answers

coronary circulation ?
Juri Reply
Coronary circulation is the circulation of blood in the blood vessels that supply the heart muscle (myocardium). Coronary arteries supply oxygenated blood to the heart muscle, and cardiac veins drain away the blood once it has been deoxygenated. Because the rest of the body.
Riyaz
coronary circulation ,is flow of blood that supplies the heart tissue itself is the coronary circulation. the functional blood supply of the heart,is the shortest circulation in tha body.
Vineeta
what about the easy way to understand action potential
Bright
event of cardiac cycle
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Chandan
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kaso Reply
anatomy is the scientific way of studying the body structure.
cynthia
the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts.
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what is means by LAPE and HAPE
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guys i've question what occur when homeostasis balance mechanisms lost
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Bladder is blank to the small intestine, what is the right directional term for that?
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When peristaltic movement is correct.
Farid
what tissue that support body organ?
Sabrina Reply
the skeleton
veronica
Skeleton
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skeleton
Juwita
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BILAL
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hanuman
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hanuman Reply
go uuu
Prasad
206
Prasad
206
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206
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206
Joey
baby me 360. and human body 206.found bones.....
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what is a tissue in Anatomy and physiology
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what is an example of a molecule that can directly pass through the phospholipid bilayer of the plasma membrane?
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how many bones are there in the hand and wrist
hanuman
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answer 206 bones
GEBAH
axial 80 appendicular 126 total bone is 206
Vineeta
wrist bone 8
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Jo carpus wrist bone h
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206
Musonda
206 bones in human body.
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What is Heart attack?
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A heart attack happens when the flow of oxygen-rich blood to a section of heart muscle suddenly becomes blocked and the heart can't get oxygen. If blood flow isn't restored quickly, the section of heart muscle begins to die. Heart attack treatment works best when it's given right after symptoms occu
Riyaz
how can l understand Anatomy quickly?
Agness Reply
you can't!!!! Anatomy is easy but the physiology takes time to understand. Anatomy is simply systems and organs but you must take time to learn physiology to understand how the anatomy works
Rachael
alright.. so how can l at least memorize the information about physiology?
Agness
what name is given to the fluid that is drawn from the villi to the lymphatic vessels
margaret Reply
I think venous
Noor
lymph
Rachael
I also think it's lymph
Akhi
me too I think lymph
Esmeralda
ans Rhythmic contraction
GEBAH
what are the ten (10) rights for drug administration
GEBAH
importance of muscle in the anatomical structures.
Akomeng Reply
it permits the constant level of movement,and gives structure and shape to the body
Priya
what is assimilation
Asiimwe Reply
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, the current topic
Hilya
cellular level
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Priya
what is anatomy?
Aleah Reply
anatomy is the study of internal parts of body by disecting it.
Shweta
The study of the internal body parts and it's organs are referred as Anatomy.
Adarsh
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Annica Reply
undesrtanding the different part of a cell
Jean
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david
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Urama Reply
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Longvwam
The sperm is _______ to the sternum
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distal
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posterior
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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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