The Skeletal System
o The skeletal system is made up of three main components:
Bones
Cartilages
Ligaments
o These components are tightly joined together, meaning they are connected in
a way that creates a unified structure.
o Together, they form a strong and flexible framework that supports the entire
body.
“Strong” refers to the ability to withstand force and protect internal
organs.
“Flexible” refers to the ability to allow movement without breaking.
Cartilage
Cartilage is described as the embryonic forerunner of most bones, meaning:
o During early development (in embryos), cartilage appears first.
o Later, most of this cartilage is replaced by bone as the skeleton matures.
In the mature skeleton, cartilage does not disappear completely.
o Instead, it covers many joint surfaces.
o This covering helps joints move smoothly and reduces friction during
movement.
Ligaments
Ligaments are structures that hold bones together at joints.
o They act as stabilizing connections between bones.
o Their purpose is to maintain proper alignment and prevent excessive
movement at joints.
Tendons
Tendons are structurally similar to ligaments:
o Both are strong connective tissues.
The key difference (as stated) is their attachment:
o Tendons attach muscles to bones, allowing muscles to move the skeleton
when they contract.
Variety of Bone Shapes
, Bones come in a wide variety of shapes.
These shapes are correlated with their different protective and locomotor
(movement-related) functions.
o This means the shape of each bone is related to the specific job it performs.
Flat Bones
Most cranial bones (bones of the skull) are flat bones.
Flat bones are described as thin, curved plates.
Example:
o The paired parietal bones, which form the dome of the top of the head, are
flat bones.
Other bones that are also classified as flat bones include:
o Sternum (breastbone)
o Scapula (shoulder blade)
o Ribs
o Hip bones
Long Bones
The most important bones for body movement are the long bones of the limbs.
Examples of long bones in the arm and forearm:
o Humerus
o Radius
o Ulna
Examples of long bones in the thigh and leg:
o Femur
o Tibia
o Fibula
Examples of long bones in the hands and feet:
o Metacarpals (hand)
o Metatarsals (foot)
o Phalanges (fingers and toes)
Long bones function like crowbars, acting as rigid levers.
o These levers are acted on by skeletal muscles.
o This interaction produces major body movements.
Short and Irregular Bones
Some bones do not fit into the long bone or flat bone categories.
These bones may be categorized as:
o Short bones
o The skeletal system is made up of three main components:
Bones
Cartilages
Ligaments
o These components are tightly joined together, meaning they are connected in
a way that creates a unified structure.
o Together, they form a strong and flexible framework that supports the entire
body.
“Strong” refers to the ability to withstand force and protect internal
organs.
“Flexible” refers to the ability to allow movement without breaking.
Cartilage
Cartilage is described as the embryonic forerunner of most bones, meaning:
o During early development (in embryos), cartilage appears first.
o Later, most of this cartilage is replaced by bone as the skeleton matures.
In the mature skeleton, cartilage does not disappear completely.
o Instead, it covers many joint surfaces.
o This covering helps joints move smoothly and reduces friction during
movement.
Ligaments
Ligaments are structures that hold bones together at joints.
o They act as stabilizing connections between bones.
o Their purpose is to maintain proper alignment and prevent excessive
movement at joints.
Tendons
Tendons are structurally similar to ligaments:
o Both are strong connective tissues.
The key difference (as stated) is their attachment:
o Tendons attach muscles to bones, allowing muscles to move the skeleton
when they contract.
Variety of Bone Shapes
, Bones come in a wide variety of shapes.
These shapes are correlated with their different protective and locomotor
(movement-related) functions.
o This means the shape of each bone is related to the specific job it performs.
Flat Bones
Most cranial bones (bones of the skull) are flat bones.
Flat bones are described as thin, curved plates.
Example:
o The paired parietal bones, which form the dome of the top of the head, are
flat bones.
Other bones that are also classified as flat bones include:
o Sternum (breastbone)
o Scapula (shoulder blade)
o Ribs
o Hip bones
Long Bones
The most important bones for body movement are the long bones of the limbs.
Examples of long bones in the arm and forearm:
o Humerus
o Radius
o Ulna
Examples of long bones in the thigh and leg:
o Femur
o Tibia
o Fibula
Examples of long bones in the hands and feet:
o Metacarpals (hand)
o Metatarsals (foot)
o Phalanges (fingers and toes)
Long bones function like crowbars, acting as rigid levers.
o These levers are acted on by skeletal muscles.
o This interaction produces major body movements.
Short and Irregular Bones
Some bones do not fit into the long bone or flat bone categories.
These bones may be categorized as:
o Short bones
