The Skeletal System

Anatomical defintions

Bone ClassificationsBones can vary in size and shape based

upon the function that they serve within the body.

These are:1. Long Bones2. Short Bones3. Sesamoid Bones4. Flat Bones5. Irregular Bones

Long Bones

Consist of a long shaft covered by hard bone around a hollow centre which contains yellow marrowThe two ends contain spongy bone and red marrow

Long Bones

These bones are light but very strong, and are the major weight- bearing bones of the body

ie: The Femur in the thigh

Short BonesThese bones are chunky, compact bones that are strong and reinforced by thickening of the bone tissue.

They contain spongy bone and allow a variety of movements at joints

EG: Carpals in the hand

Flat Bones

These bones are made up of two strong layers of spongy bone.

They give protection to organs beneath them and allow for large areas of muscle attachment

EG: The Scapula (Shoulder Blade)

Irregular Bones

These bones are made up of a thin layer of compact bone containing a mass of spongy boneIrregular bones are reinforced where extra strength is required

EG: Vertebrae

Sesamoid Bones

These are small bones that are located within the tendons of some joints. ie: the Patella

Developing Bones

A baby’s bones contain cartilage, a tough, strong tissue is not as hard as bone.

Cartilage is more flexible and tends to bend a little without breaking

**Check the end of your nose**

Developing BonesAs the child grows this cartilage is replaced by bone, becoming harder and less flexible

Therefore it is easier for a teenager to break a bone than it is for a child.

Note: If the bone is flexible it will bend under strain before snapping!

Developing Bones

Bone cells are constantly replaced throughout our lives.During our growth spurt in puberty our bones grow longer, stronger and heavier

Developing Bones

Peak Bone Mass = The formation of mineral deposits

and compact bone that helps give maximum strength to bone

Developing Bones

Osteoporosis =A condition which results in loss of

bone mass and strength, making bones more fragile and likely to break or fracture

SHORT BONE GROWTHThe outside of a short bone is formed by cartilage. The cartilage grows until the final shape of the bone is formed.Meanwhile the bone ossifies (hardens into bone) from the inside outwards. Eventually all cartilage is ossified, and growth is complete.

LONG BONE GROWTHTwo growth processes responsible for bone

development.

First process:OSTEOBLASTS (bone builders) – add bone to the outside surface, enlarging and elongating the bone.OSTEOCLASTS (bone eaters) – tunnel out the marrow cavity and internal spaces (these work at the same time as osteoblasts.)

Long bone growthSecond process (greatest growth occurs):

EPIPHYSEAL PLATES (growth plates) found at either end of the bone where the shaft (diaphysis) meets the head or base (epiphysis). These growth plates are made of cartilage cells which multiply rapidly and the outside cells ossify, increasing the length of the shaft.

GROWTH HORMONE (GH)GH - Responsible for most growth changes occurring.

Produced by the pituitary gland, at the base of the brain.

Growth Hormone:(1) stimulates the epiphyseal plates to expand and form bone(2) increase protein uptake by the muscles, therefore increasing muscle growth

FACTORS AFFECTING GROWTH

Basic control of growth is geneticStarvation and Malnutrition can delay growth spurtMajor illness slow down growth Regular exercise has many growth benefitsAerobic exercise also increases the size and efficiency of the heart, blood and lungs. However, repetitive long distance training for marathons or triathlons may damage epiphyseal plates.