Human Anatomy

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Human Anatomy

The human body is the most ingenious assembly of purposeful components you will ever find on this planet.

Beneath its envelope of skin and tissue, we find muscles, nerves, a circulatory system for the blood, glands, vital organs and that marvellous system of bones called the Skeleton.

Not only is the skeleton responsible for supporting the muscles and the body as a whole, protecting vital organs such as the brain and lungs, it is responsible for our basic size and shape; although the last word in this matter comes from the muscles, with the subcutaneous tissue and skin adding the final touches.

The skeleton consists of 214 bones (this number includes the six small ossicles found in the ears… these ossicles are not listed below) ……

AXIAL SKELETON

The axial skeleton comprises the skull, vertebral column (backbone), sternum (breastbone) and ribs.

APPENDICULAR SKELETON

The appendicular skeleton comprises the limbs, shoulder and pelvic girdle.

The bones of the skeleton are classified according to their shape and formation:

LONG BONES                mainly found in the limbs, fingers etc

SHORT BONES              such as found in the wrists

FLAT BONES                  the shoulder-blades, large bones of the skull etc

IRREGULAR BONES       some facial bones, vertebrae, etc

SESAMOID BONES        bones developed in the tendons of certain

muscles, the kneecap a good example

 

Starting at the top, we have the SKULL.

The skull consists of two main parts – the Cranium and the Face.

The Cranium consists of 8 bones:

1   Occipital bone

2   Parietal bones

1   Frontal bone

2   Temporal bones

1   Sphenoid bone

1   Ethmoid bone

The Face contains 14 bones:

2   Nasal bones

2   Palatine bones

2   Lacrimal bones

2   Zygomatic bones

1   Vomer

2   Inferior Turbinate bones

2   Maxillae

1   Mandible

The Vertebral Column has 33 (sometimes 34) bones in all.

Each separate bone is called a vertebra, (the plural of Vertebra is Vertebrae)

The upper 7 vertebrae are called the Cervical vertebrae and the upper-most two cervical vertebrae permit movment of the neck.  The first cervical vertebra, situated at the very top of the vertebral column is called the Atlas, and the second cervical vertebra is called the Axis. Together these two vertebrae form the Atlanto-axial joint.

Below the cervical vertebrae we have 12 Thoracic vertebrae.

Moving down the vertebral column we come to 5 Lumbar vertebrae.

After the lumbar vertebrae we come to 5 Sacral vertebrae forming the Sacrum.

These 5 vertebrae are flat and fused together in the adult.

Finally, we come to the Coccyx (tail) which comprises 4 (or 5) Coccygeal vertebrae.

In the adult the coccygeal vertebrae are fused together.

Now we come to what is known as the Thoracic Cage.

This consists of 12 thoracic vertebrae (already mentioned) at the back, 12 pairs of ribs at the sides, and the sternum at the front.

Uppermost in the thoracic cage we have 7 pairs of True ribs.

Below the true ribs are 3 pairs of False ribs and 2 pairs of Floating ribs.

Whereas the true ribs (pairs 1,2,3,4,5,6,7) are all attached directly to the sternum, pairs 8, 9 and 10 are attached indirectly to the sternum by means of an attachment of cartilage extending from eaach rib, to the rib above. The lowest ribs (pairs 11 and 12) are not attached to the sternum in any way.

Above the thoracic cage we have the shoulder girdle:-

Left and Right Clavicle (collarbones) / Left and Right Scapula (shoulderblades)

Situated in isolation in the front of the throat is a small bone known as the Hyoid bone.

Attached to each side of the shoulder girdle we have the limbs of the upper body (arms)

nearest the shoulder is the Humerus bone of the upper arm … in the lower part of the arm we have the Radius and the Ulna, two bones placed side by side …

bones of the wrist and hand are:-

the 8 bones of the carpus :-   navicular (scaphoid),

lunate (semilunar),

triquetral,

pisiform,

trapezium,

trapezoid,

capitate,

hamate

the 5 Metacarpals (bones between the fingers and wrist) and 14 Phalanges forming the thumb and 4 fingers

Below the waist we come to the Pelvic Girdle consisting of the 5th lumbar vertebra, the sacrum, and coccyx at the back and 2 Innominate bones encircling the remainder of the region.

Bones of the leg are:-

Femur (Thigh Bone) / Patella (Kneebone) / Tibia (Shin Bone) / Fibula (placed alongside the Tibia)

Bones of the foot are:-

The 7 bones of the Tarsus = Calcaneum (Heel) / Talus / Navicular / Cuboid / 3 Cuneiforms –

The 5 Metatarsals and 14 Phalanges forming the Toes

 

JOINTS of the SKELETON

A Joint (for articulation) is a union of two or more bones of the skeleton

There are three main types:- 1. Fibrous / 2. Cartilaginous / 3. Synovial

These types vary considerably in the amount of movement they permit and may be classified as:-

1. Immovable / 2. Slightly movable / 3. Freely movable

 

FIBROUS JOINTS (Immovable) – A fixed joint allowing no movement whatsoever, eg the sutures (or joints) of the flat bones of the skull … the teeth in their sockets etc

CARTILAGINOUS JOINTS (Slightly movable) – In this type of joint, the joint surfaces are separated by some intervening substance such as cartilage etc eg the intervertebral joints of the vertebral column with their intervertebral discs of fibro-cartilage.

SYNOVIAL JOINTS (Freely movable) – The ends of the bones forming the joint are covered by hyaline cartilage. Ligaments are necessary to bind the bones together, and the joint cavity is filled with synovial fluid and enclosed by a capsule of fibrous tissue.

Varieties of Synovial Joints :-

1. Gliding                eg  small bones of the carpus etc

2. Ball and Socket   eg  hip joint and shoulder joint

3. Hinge                  eg  elbow joint

4. Condyloid            eg  wrist joint

5. Pivot                   eg  Atlanto-axial joint

6. Saddle                eg  joint between the trapezium and first metacarpal bone