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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

why simple columnar support peristalisis
Camilius Reply
why when sex of an individual is determined by y chromosome found in male therefore why there is many women than male
pamfili Reply
I'm not sure if I fully understand your question.
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samir
i don't remember what I said.
I'm not sure if I fully understand your question.
roughly taking a lead.
samir
Muscle of mastication
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difference between seminiferous tubules and ejaculatory duct
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Musibi
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Kity
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Karan Reply
Sir muscle contraction ka topic kis part m milega
sonugora Reply
Sir muscle contraction ka topic kis part m milega
sonugora Reply
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Ambika Reply
life circle of RBC and the life circle of WBC.
Yemi Reply
RBC 120days
Zeph
RBC 120days and WBC 10-12days
sai
what is cardiac vascular system
Hari
what is anatomy?
Md Reply
what is manipulated
Ambika
anatomy is the branch of medical science which deal with the gross structure of body or organ
Ambika
note shoulder joint
jagadeesh
what is cardiovascular system
Hari
what is manipulated
Ambika
anatomical position
Ambika
?
Ambika
Scapula
sonugora
Study of internal structures
sonugora
the system of heart and vessels
Manar
what is collar Bone?
jagadeesh
positive feedback mechanism
Sirimala Reply
what is immunology
Riya Reply
immunology is a branch of medicine that study's the body immune system
SAMUEL
Immunology This is the study of specific and non-specific resistance of the body against infection i.e. the study of the immune response of a host to a foreign substance, which includes study of various reactions which are induced in the body by introduction of a substance.
Kaluki
what is role of elimination need like fluid and also stools
Munmun Reply
bone
Vijay
what is joint pain
Vijay
is the physical suffering caused by illness or injury of the joint
malulu
pls can someone describe shock,types ,pathophysiology and treatment
Isaac
this is what I'm thinking "After taking out everything the body needs, the bowel then expels the leftover waste."
isaiah
I think elimination also helps in the continuation of the digestive system because if the unwanted fluids and stools does not come out of the system it can create a problem in the digestive. system resulting in diseases.
Martha
shock is a condition whereby the circulating system is unable to get enough blood and oxygen to vital organs like the brain,heart,eye,kidney and others.
Martha
causing depression of those organs.
Martha
there are 2 classification of shock. primary shock: this occurs immediately after injury due emotional stimulus or pain.example hearing a bad news,sudden obstruction of airway.sudden heart attack. secondary shock :it occurs when primary shock is delayed
Martha
types of shock syncope (faint) oligaemic or hyppvovaemic shock. Anaphylactic shock. neurogenic/ physical shock septic sock catdiogenic shock.
Martha
What is the difference between dna duplication and chromosomes duplication?

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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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