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THE SKELETAL SYSTEM

COMPILED BY HOWIE BAUM

INTRODUCTION

With its highly engineered joints, the living skeleton is intimately connected with the muscular system.

It provides a framework of stiff levers and stable plates that permits a multitude of movements.

The skeleton also integrates functionally with the cardiovascular system – as every second, millions of fresh blood cells pour out of the bone marrow.

A healthy diet that provides enough minerals, especially calcium, along with regular moderate exercise, can reduce the risks of many bone and

The skeleton is the framework that provides structure to the rest of the body and facilitates movement.

When you look at the human skeleton the 206 bones and 32 teeth stand out.

But look closer and you’ll see even more structures.

The human skeleton also includes ligaments and cartilage.

Ligaments are bands of dense and fibrous connective tissue that are key to the function of joints.

Cartilage is more flexible than bone but stiffer than muscle.

Cartilage helps give structure to the larynx and nose. It is also found between the vertebrae and at the ends of bones like the femur.

These bones provide structure and protection and facilitate motion.

 Bones are arranged to form structures.

 The skull protects the brain and gives shape to the face.

 The thoracic cage surrounds the heart and lungs.

 The vertebral column, commonly called the spine, is formed by over 30 small bones.

 Then there are the limbs (upper and lower) and the girdles that attach the four limbs to the vertebral column.

THE SKELETON PROTECTS

VITAL ORGANS

The brain is surrounded by bones that form part of the skull.

The heart and lungs are located within the thoracic cavity, and the vertebral column provides structure and protection for the spinal cord.

BONES ARE GROUPED INTO THE AXIAL

SKELETON AND THE APPENDICULAR

SKELETON

Bones of the appendicular skeleton facilitate movement - girdles and limbs

Bones of the axial skeleton protect internal organs – skull, vertebral column and thoracic cage

Of the 206 bones, 80 are in the axial skeleton, with 64 in the upper appendicular and 62 in the lower appendicular skeleton.

BONES CAN BE CLASSIFIED

INTO FIVE TYPES

Bones of the human skeletal system are categorized by their shape and function into five types.

The femur is an example of a long bone.

The frontal bone is a flat bone.

The patella, also called the knee cap, is a sesamoid bone.

Carpals (in the hand) and tarsals (in the feet) are examples of short bones.

Vertebrae are classified as Irregular shaped bones.

SOME BONES PRODUCE

RED BLOOD CELLS

Red bone marrow is soft tissue located in networks of spongy bone tissue inside some bones. (shown in blue in the image)

In adults the red marrow in bones produce blood cells of the:

 Cranium (skull)

 Vertebrae

 Scapulae (shoulder bones)

 Sternum (bone in the center of the chest)

 Ribs

 Pelvis

 The epiphyseal ends of the large long bones

SOME JOINTS DON'T MOVE OR MOVE

VERY LITTLE

One way to classify joints is by range of motion.

Immovable joints include:

 Sutures of the skull

 Articulations between teeth and the mandible

 The joint located between the first pair of ribs and the sternum.

Some joints have slight movement ; an example is the distal joint between the tibia and fibula. Joints that allow a lot of motion (think of the shoulder, wrist, hip, and ankle) are located in the upper and lower limbs.

FLAT BONES PROTECT

INTERNAL ORGANS

There are flat bones in

 the skull (occipital, parietal, frontal, nasal, lacrimal, and vomer),

 the thoracic cage (sternum and ribs)

 the pelvis (ilium, ischium, and pubis).

The function of flat bones is to protect internal organs such as the brain, heart, and pelvic organs.

Flat bones can provide protection, like a shield and can also provide large areas of attachment for muscles.

LONG BONES SUPPORT WEIGHT

AND FACILITATE MOVEMENT

The long bones, longer than they are wide, include:

The femur (the longest bone in the body)

Relatively small bones in the fingers.

Long bones are mostly located in the appendicular skeleton and include

The lower limbs

Bones in the upper limbs

IRREGULAR BONES HAVE

COMPLEX SHAPES

Irregular bones vary in shape and structure and therefore do not fit into any other category (flat, short, long, or sesamoid).

They often have a fairly complex shape, which helps protect internal organs.

For example, the vertebrae, irregular bones of the vertebral column, protect the spinal cord.

The irregular bones of the pelvis protect organs in the pelvic cavity.

SESAMOID BONES

REINFORCE TENDONS

Sesamoid bones are bones embedded in tendons.

These small, round bones are commonly found in the tendons of the hands, knees, and feet.

Sesamoid bones function to protect tendons from stress and wear.

The patella, commonly referred to as the kneecap, is an example of a sesamoid bone.