The Four Shapes of Bone and What They Do
The skeleton is the bodys frame.
It provides the foundation to which other structures cling and helps to create our shape.
Each throw in of bone serves a particular purpose and some types have more than one function.
ledwell/ Getty Images
Long Bones
The skeleton of the arms and legs are made up of mostly long bones.
Long bones are so-called because they are longer than they are wide.
Long bones in the arm include thehumerus,radius,ulna, metacarpals, and phalanges.
Long bones of the leg include thefemur,tibia,fibula, metatarsals, and phalanges.
The clavicles (collar bones) are also long bones.
Long bones provide the leverage we need for moving our bodies and for manipulating our environment.
All long bones have two main parts: diaphysis and epiphysis.
Diaphysis
The diaphysis is the shaft of the long bone, the main body.
The diaphysis is a tube with a hollow center called the medullary cavity (or marrow cavity).
The wall of the diaphysis is made up of compact bone, which is dense and very hard.
Yellow bone marrow is basically fat, also known as adipose tissue.
Epiphysis
Each end of a long bone is called an epiphysis.
This shape allows those two long bones to rotate in multiple directions.
The head of the femur fits into a socket in the pelvis.
The head of the humerus fits into a socket in the shoulder.
That punch in of joint is called a ball-and-socket joint.
Joints that only allow movement along one axis are called hinge joints.
The wall of the epiphysis is made of compact bone like the diaphysis and the center contains spongy bone.
Spongy bone is made of many small cavities (also called medullary cavities) filled with red bone marrow.
Red bone marrow manufactures red blood cells and is very well connected to the circulatory system.
It is commonly known as the growth plate.
Short Bones
Short bones are called that because they about as wide as they are long.
There is no diaphysis on a short bone.
It is made up of spongy bone surrounded by compact bone just like the epiphysis.
Short bones also contain red bone marrow.
There are 32 short bones in the human skeleton.
However, the patella is common to everyone while sesamoid bones develop differently between individual people.
Flat Bones
Flat bones are the armor of the body.
Flat bones can also provide protection of soft tissues underneath.
Skull
The bones of the cranium are the part of the skull that encapsulates the brain.
The bones of the cranium are connected together through joints called sutures, which look like they are stitched.
Sometimes, additional small bones can develop between sutured bones of the cranium along the suture lines.
These small bones are called sutural bones.
They develop randomly and are not named bones.
Irregular Bones
Bones that are neither long, short, nor flat are considered irregular bones.
The shapes of these bones provide very specific functions.
Some of the bones of the face appear in mirror image, such as thezygomatic bones(cheekbones).
Irregular bones often have complicated shapes that are used as insertion points for muscles, tendons, and ligaments.
The most common shape is called a process that looks like a protrusion.
Sesamoid Bones
Sometimes, bones will develop due to friction along tendons or ligaments.
Usually, these are very small bones and develop randomly between individuals.They are not named.
Some anatomists consider the patella an example of sesamoid bone.
Frequently Asked Questions
There are 206 bones in the human body.
Compact bone is the middle of three main layers in every bone.
Its material is hard and smooth to protect bones and offer structural support.
The outer layer is called periosteum, and the inner layer is known as spongy bone.
Calcium phosphate is a mineral that gives bones strength.
The strongest bone in the body is the femur, or your thighbone.
It is also the longest bone in the human body.
There are a total of 27 bones in the hand.
This includes 14 phalanges (finger bones), five metacarpal bones, and eight carpal bones.
The diaphysis is a tube-like structure that makes up the main shaft of a long bone.
Its walls are made of compact bone, meaning it is hard and dense.
Its center is filled with yellow bone marrow for most of the long bones life.
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