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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

send me a cytoplasm arganles anatomy and thire physology
Hayat Reply
the organelles r found within the cytoplasm e.g. mitochondria etc.
one by one detail
the cell contains the cytoplasm, organelles, cytoskeleton, inclusions(foreign material), cytosol. of course the cell membrane. the nucleus. the nucleus is inside the nucleus. the rough endoplasmic reticulum is usually next to the smooth er
nucleolus inside nucleus
the mitochondria is in there and the Golgi apparatus, lysosomes, ribosomes, peroxisomes and centrioles
everything I mentioned after the nucleus kinda the nucleolus: r organelles
Bones that are bind together by inelastic tissue connective tissue are called
Augustina Reply
the skull too can be part
the skull is 22 bones
vertebral bones
what are the body plains
Sanjana Reply
median plane,transverse or horizontal plane and coronal or frontal plane
How do I summarize the whole of muscular system
Mary Reply
briefly explain the similarities between transcription and DNA replication
Emmanuel Reply
transcription copies DNA into RNA while replication makes another copy of DNA
A general explanation: Replication occurs when a copy of DNA is made. Transcription is the first step in the process of protein synthesis. Messenger RNA is made using a portion of the DNA molecule as a template.
please what group is this?
hello guys
Relationship between essential amino acids and immune response
transcription from DNA to rna involves the matching of the nucleotides represented by c,g, t and A, but where there is a t, it is replaced by a u- uracil
what is the main function of the pcn?
career in the health professions, respond appropriately to signs of illness, help you in your roles as a parent, spouse
Coach Reply
student would have an appreciation of the heart anatomy to give understanding of anatomy while opening ideas of function and physiology
study of the parts of the body
macro anatomy, study of big structures of the body that can be viewed with the naked eye
that is called gross anatomy
what is integumentry
Amiebo Reply
chemical level cell level tissue level organs level organ system organism
sam Reply
when you sitting close to a campfire your sense smell adapts the smell but when the trace of smoke is introduced into your environments it becomes unsual for you
I need to know mechanism of body fluid
OK but I need to know where are you coming from
ask how
oh ft, help out with integumentary system now
Pls give me a brief description of vetebra
Deborah Reply
7 cervical (c1 atlas and c2 axis help the neck rotate) 12 thoracic 5 lumbar 1 sacral and 2 coccyx
breakfast at 7, lunch at 12, and dinner at 5. sacrum holds 5, coccyx holds 4
really there's just one coccyx and sacrum
atlas like the Greek God holds the weight of the world on top of him
elasticity of the vagina
Mariam Reply
The vagina is an elastic muscular wall
It has I think squamous cuboidal or maybe columnar epithelium designed for secretion, expansion and friction.
how can you remember the integumentary system
Naomi Reply
integumentary system is the skin the skin is protection all the body and contain deid cells
how can you remember the formation of bone?
the largest organ of the body
skin is largest organ
what is the best way to remember the cranial bones or any other bones ?
skeletal system?
look at the diagram structure and then remember it considering it your own body i memorise like that
hi guys! do you have to remember ALL the structures of the bones- I mean every single hole, depression or tuberosity?
hey guz i hv to remember Immune antibodies and antigens how? i found it difficult
well, they are all grouped, aren't they? I mean they all come in series like H1, H2A, H2B and so on. In this case I learn the common part first and then that what's different
nd what about IgG , IgE etc.
the majors
the thin skin does not have stratum lucidium I believe
if u know the bones, the muscle has part of the name of the bone in it
epidermis, I believe epi means on top. dermis in the middle and hypodermis, hypo meaning below. the hypodermis is actually considered not part of the skin or int system
big sweet guys love candy = basale, spinosum, granulosum, lucidum ( only in thick skin), corneum
I love it ☝🏾
thank you Zara !
can anyone send diet plan for asthma patients
jam how are you
Hey guys l am Matrin
blood is a connective tissue which transport oxygen and other nutrients to body
Zara Reply
which type of protein is blood?
what is blood?
Masthan Reply
blood is a connective tissue which transport oxygen and nutrients to body
which type of protein is blood?
and what about its structure i think its Quartenary structure 🤔💭
yes it is
it is globular
a vascular structure compose of vessels.
what is the functions of lymph
moula Reply

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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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