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The Axial Skeleton

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TaskLabel the diagram of the skeleton

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Introduction

The skeleton is divided into two parts: The axial skeleton The appendicular skeleton

The axial skeleton is made up of 80 bones comprising of the skull, rib cage and vertebral column. We will now look in detail at each section (see separate presentation for the skull).

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The Vertebral Column

o The vertebral column is made up of 33 individual bones, though some are fused together.

o In-between each vertebrae is a pad of fibrous tissue called a disc.

o These discs act as shock absorbers to protect against gravity and injury.

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Functions Of The Vertebral Column

Protects the spinal cord – each vertebrae contains a hole in the centre through which the spinal cord runs.

Provides attachment for the ribs Provides attachment for the muscles

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Cervical Vertebrae

The first seven vertebrae are called the cervical vertebrae.

At the top of the spinal column, these bones form a flexible framework for the neck and support the head.

The first cervical vertebrae is called the atlas and the second is called the axis.

The atlas shape allows the head to nod and the axis allows the head to shake.

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Thoracic Vertebrae

The next twelve vertebrae are called the thoracic vertebrae.

These are found in the upper back.

These bones move with the ribs to form the rear anchor of the ribcage.

Thoracic vertebrae are larger than cervical vertebrae and increase in size from top to bottom.

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Lumbar Vertebrae

The lumbar vertebrae are situated in the lower back.

These five bones are the largest vertebrae in the spinal column.

They support most of the body's weight and many of the back muscles attach to the lumbar vertebrae.

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The Sacrum

The sacrum is a triangular bone located just below the lumbar vertebrae.

It consists of five sacral vertebrae in a child, which become fused into a single bone after age 26.

The sacrum forms the rear wall of the pelvic girdle.

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The Coccyx

The bottom of the spinal column is called the coccyx or tailbone.

It consists of 4 bones that are fused together in an adult.

Many muscles connect to the coccyx.

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Curves

When looked at from the side, the spine forms four curves.

These curves are called the cervical, thoracic, lumbar, and pelvic curves.

These curves allow human beings to stand upright and help to maintain balance.

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Ribs

The ribs are thin, flat, curved bones that form a protective cage around the organs in the thorax.

There are 24 bones arranged in 12 pairs.

The ribs form a cage that encloses the upper body.

The ribs protect the heart and lungs from injuries and shocks.

The ribs also protect parts of the stomach, spleen, and kidneys.

Ribs help you to breathe.

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Sternum

The sternum is a flat, dagger shaped bone located in the middle of the chest.

Along with the ribs, the sternum forms the rib cage.

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The Appendicular Skeleton

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Introduction

The skeleton is divided into two parts: The axial skeleton The appendicular skeleton

The appendicular skeleton is made up of 126 bones comprising of the arms, legs, pelvic girdle and shoulder girdle.

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Clavicle

There are two clavicles, more commonly known as the collar bones.

These slender bones run from the shoulder to the breast bone, below the neck.

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Scapula

The two shoulder blades are situated in the upper back.

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Humerus

The bone of the upper arm, one located in each arm.

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Radius and Ulna

The radius runs from the elbow to the thumb side of the forearm.

The ulna runs from the elbow to the little finger side of the forearm.

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Carpals, Metacarpals and Phalanges

The 16 carpal bones (8 in each) make up the bones of the wrist.

There are 5 metacarpal bones in each hand.

There are 28 phalanges that make up the fingers.

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Pelvic bones

There are two bones that form the pelvic girdle.

The pelvic girdle supports the weight of the body, protects and supports pelvic organs including: the bladder, the reproductive organs, and the developing fetus in a pregnant woman.

The pelvic girdle differs between men and woman.

In a man, the pelvis is larger and the iliac crests are closer together.

In a woman, the pelvis is more delicate and the iliac crests are farther apart to allow for the birthing process.

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Femur and Patella

There are two femur bones, one in each upper leg.

The patella is the knee cap.

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Tibia and Fibula

The tibia is one of the bones of the lower leg and runs medially to the big toe side of the leg.

The fibula is the lateral bone of the lower leg.

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Tarsals, Metatarsals and Phalanges

There are 14 tarsal bones (7 in each ankle) that collectively form the ankle.

There are 5 metatarsal bones in each foot.

There are 28 phalanges that make up the toes.