ANAT – module 2
Organization of the skeletal system
- It’s composed of bones, cartilages, joints and ligaments
- It accounts for approximately 20% of body mass
- App and axial together make approximately 206 named bones
- It is divided into two divisions – the axial and appendicular skeletons
o Axial is comprised as the skull, vertebral column, ribs and sternum
remember this like North South West East – skull, vertebral column, ribs
and sternum
o Appendicular make up our upper limb and our lower limb
The 206 bones are categorized into five different types based on their shape.
o Flat bones like the bones of the skull. These bones have a large surface area that
are used for muscles attachments and for protection of organs.
o Long bones. These are longer than they are wide. Most long bones are found in
our appendicular skeleton. Example is femur.
o Short bones, these are about as wide as they are tall. These short bones provide
stability and some movement. Examples of short bones are the ones in your
wrist or ankle.
o Sesamoid bones, these are embedded in tendons. In the patella or kneecap.
o Lastly, irregular bones. The bone shape does not fit any other category. Example
is a vertebra.
Five main functions of the skeletal system.
First three are more apparent just by gross anatomical observation:
- Support
- Movement
- Protection
Our bones provide us with structure for our body, without them we would be a pile of tissue.
Our skeleton is like a beamed framework for a house; it provides support for the muscles. Our
bones also provide an attachment point for our muscles. When our muscles contract, our bones
act as levers to make movement. Also, where our bones meet we have joints. These joints also
provide different movements for our body. Because our bones are strong and they cover many
of our internal organs, they can act as protection. (axial protects most of our internal organs).
- Storage
Osseous tissue has two more functions. It acts as a reservoir for minerals and fats. These
minerals can be tapped into at any time by the body and released into the bloodstream for use,
and this is important. Bones store calcium, which is really important for muscle contraction and
nerve impulses. There are two types of bone marrow – yellow marrow which stores fat and red
marrow. Red marrow is important for the last function of the skeletal system, hematopoiesis.
- Hematopoiesis
, (also known as the production of blood cells).
basic composition of bone
every bone is composed of two layers:
outer cortical layer: made up of compact bone which is hard
and strong.
Inner cancellous layer: made up of spongy bone, which
appears porous and sponge-like.
Blood cells are produced by the bone marrow, which is found
within the medullary cavity, the inner cavity of the bone.
Structure of long bones
- Most common type of bone found in the body
- Long bones can be as large as the femur and tibia, or as small as the bones of the fingers
and toes.
Epiphysis: knobby, enlarged regions at the end, form joints and serve as attachment sites for
tendons and ligaments.
Metaphysis: region between the diaphysis and epiphysis.
Diaphysis: elongated cylindrical shaft.
Organization of the skeletal system
- It’s composed of bones, cartilages, joints and ligaments
- It accounts for approximately 20% of body mass
- App and axial together make approximately 206 named bones
- It is divided into two divisions – the axial and appendicular skeletons
o Axial is comprised as the skull, vertebral column, ribs and sternum
remember this like North South West East – skull, vertebral column, ribs
and sternum
o Appendicular make up our upper limb and our lower limb
The 206 bones are categorized into five different types based on their shape.
o Flat bones like the bones of the skull. These bones have a large surface area that
are used for muscles attachments and for protection of organs.
o Long bones. These are longer than they are wide. Most long bones are found in
our appendicular skeleton. Example is femur.
o Short bones, these are about as wide as they are tall. These short bones provide
stability and some movement. Examples of short bones are the ones in your
wrist or ankle.
o Sesamoid bones, these are embedded in tendons. In the patella or kneecap.
o Lastly, irregular bones. The bone shape does not fit any other category. Example
is a vertebra.
Five main functions of the skeletal system.
First three are more apparent just by gross anatomical observation:
- Support
- Movement
- Protection
Our bones provide us with structure for our body, without them we would be a pile of tissue.
Our skeleton is like a beamed framework for a house; it provides support for the muscles. Our
bones also provide an attachment point for our muscles. When our muscles contract, our bones
act as levers to make movement. Also, where our bones meet we have joints. These joints also
provide different movements for our body. Because our bones are strong and they cover many
of our internal organs, they can act as protection. (axial protects most of our internal organs).
- Storage
Osseous tissue has two more functions. It acts as a reservoir for minerals and fats. These
minerals can be tapped into at any time by the body and released into the bloodstream for use,
and this is important. Bones store calcium, which is really important for muscle contraction and
nerve impulses. There are two types of bone marrow – yellow marrow which stores fat and red
marrow. Red marrow is important for the last function of the skeletal system, hematopoiesis.
- Hematopoiesis
, (also known as the production of blood cells).
basic composition of bone
every bone is composed of two layers:
outer cortical layer: made up of compact bone which is hard
and strong.
Inner cancellous layer: made up of spongy bone, which
appears porous and sponge-like.
Blood cells are produced by the bone marrow, which is found
within the medullary cavity, the inner cavity of the bone.
Structure of long bones
- Most common type of bone found in the body
- Long bones can be as large as the femur and tibia, or as small as the bones of the fingers
and toes.
Epiphysis: knobby, enlarged regions at the end, form joints and serve as attachment sites for
tendons and ligaments.
Metaphysis: region between the diaphysis and epiphysis.
Diaphysis: elongated cylindrical shaft.
