, Overview of the Skeletal System
Function
Support Provides a rigid framework that supports the body’s muscles and
soft tissues, keeping us upright.
Protection Shields internal organs from physical damage (e.g., the skull
protects the brain, the rib cage protects the lungs and heart).
Movement Works with muscles to produce movement. Muscles contract and
pull-on bones, creating movement at the joints.
Mineral Storage Stores essential minerals, particularly calcium and phosphorus,
which can be released into the bloodstream as needed.
Blood Cell Red bone marrow (in certain bones like the pelvis, femur, and
Production sternum) produces red blood cells, white blood cells, and platelets
Bone classifications
Bones are classified based on their shape, which reflects their function.
They can be divided into five main types:
long Bones (e.g., femur, humerus) – Longer than they are wide, they act as
levers for movement.
Short Bones (e.g., carpals, tarsals) – Cube-shaped, providing stability and some
limited motion.
Flat Bones (e.g., sternum, ribs, skull bones) – Thin and flat, offering protection
to organs and providing surfaces for muscle attachment.
Irregular Bones (e.g., vertebrae, pelvic bones) – Complex shapes, providing support and
protection.
Sesamoid Bones e.g., patella) – Embedded within tendons, they help reduce friction
and protect tendons from stress.
Bone structure
Compact Bone: Dense and forms the outer layer of bones. It is strong and designed for
support, providing strength for weight-bearing
Spongy Bone Also known as cancellous bone, it is lighter and less dense than
compact bone. Found mainly at the ends of long bones, helps distribute
weight and absorb shock.
, Bone cells
Osteocytes Mature bone cells that maintain bone tissue and monitor the bone's health
Osteoblasts Bone-forming cells responsible for creating new bone tissue by producing
osteoid, which later mineralises to form bone.
Osteoclasts Large cells that break down bone tissue during bone remodelling, allowing
for the release of minerals (like calcium) into the bloodstream.
Bone Matrix & Composition
The bone matrix is like the “foundation” of your bones. It’s made up of two main components:
organic and inorganic:
Organic Components (Collagen): Inorganic Components (Minerals)
Collagen is a protein that contributes to the The most important minerals in the bone matrix
bone matrix. are calcium phosphate (also called
hydroxyapatite).
Think of collagen as the framework that Phosphorus is another mineral that helps
holds everything together and keeps bones harden the bones, working alongside calcium
from being too brittle. to ensure bones are sturdy and able to
support the body.
NOTE
Degrees of freedom How many ways a joint can move, for example, a joint can bend,
twist, or slide
Range of motion How far a joint can move in each direction. In degrees
Function
Support Provides a rigid framework that supports the body’s muscles and
soft tissues, keeping us upright.
Protection Shields internal organs from physical damage (e.g., the skull
protects the brain, the rib cage protects the lungs and heart).
Movement Works with muscles to produce movement. Muscles contract and
pull-on bones, creating movement at the joints.
Mineral Storage Stores essential minerals, particularly calcium and phosphorus,
which can be released into the bloodstream as needed.
Blood Cell Red bone marrow (in certain bones like the pelvis, femur, and
Production sternum) produces red blood cells, white blood cells, and platelets
Bone classifications
Bones are classified based on their shape, which reflects their function.
They can be divided into five main types:
long Bones (e.g., femur, humerus) – Longer than they are wide, they act as
levers for movement.
Short Bones (e.g., carpals, tarsals) – Cube-shaped, providing stability and some
limited motion.
Flat Bones (e.g., sternum, ribs, skull bones) – Thin and flat, offering protection
to organs and providing surfaces for muscle attachment.
Irregular Bones (e.g., vertebrae, pelvic bones) – Complex shapes, providing support and
protection.
Sesamoid Bones e.g., patella) – Embedded within tendons, they help reduce friction
and protect tendons from stress.
Bone structure
Compact Bone: Dense and forms the outer layer of bones. It is strong and designed for
support, providing strength for weight-bearing
Spongy Bone Also known as cancellous bone, it is lighter and less dense than
compact bone. Found mainly at the ends of long bones, helps distribute
weight and absorb shock.
, Bone cells
Osteocytes Mature bone cells that maintain bone tissue and monitor the bone's health
Osteoblasts Bone-forming cells responsible for creating new bone tissue by producing
osteoid, which later mineralises to form bone.
Osteoclasts Large cells that break down bone tissue during bone remodelling, allowing
for the release of minerals (like calcium) into the bloodstream.
Bone Matrix & Composition
The bone matrix is like the “foundation” of your bones. It’s made up of two main components:
organic and inorganic:
Organic Components (Collagen): Inorganic Components (Minerals)
Collagen is a protein that contributes to the The most important minerals in the bone matrix
bone matrix. are calcium phosphate (also called
hydroxyapatite).
Think of collagen as the framework that Phosphorus is another mineral that helps
holds everything together and keeps bones harden the bones, working alongside calcium
from being too brittle. to ensure bones are sturdy and able to
support the body.
NOTE
Degrees of freedom How many ways a joint can move, for example, a joint can bend,
twist, or slide
Range of motion How far a joint can move in each direction. In degrees
