Skeletal System



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Skeletal System


Three Types of Skeletons

1. Hydrostatic (water)


2. Exoskeleton (arthropods)
3. Endoskeleton (vertebrates)

The Skeleton of Humans is composed of a special connective tissue called BONE

There are 206 bones in the human body
 

THE BONES THAT MAKE UP THE SKELETON SYSTEM SERVES FOUR IMPORTANT FUNCTIONS:ÊÊ



A. Provides a framework that Supports the Body; the muscles that are attached to the bones move the skeleton.
B. Protects Some Internal Organs from mechanical injury; the rib cage protects the heart and lungs or the skull around the brain.
C. Contains and Protects the Red Bone Marrow, Some White Blood Cells (Leukocytes) are also produced in Bones.
D. Provides a Storage Site of Inorganic Salts, such as CALCIUM.Ê Calcium may be removed from bone to maintain a normal blood calcium level, which is essentially for BLOOD CLOTTING

Bones are classified by their shape

1. Long bones (humerus, femur)
2. Flat bones (skull)
3. Short bones (fingers)
4. Irregular bones (vertebrae)

 

THE HUMAN SKELETON HAS TWO DIVISIONS:Ê



THE AXIAL SKELETON - CONSIST OF THE SKULL, VERTEBRATE COLUMN, AND THE RIB CAGE

The Skull consists of 8 CRANIAL BONES and 13 FACIAL BONES


The Ears consists 6 BONES, AND FLOATING IN THE THROAT 1 BONE THE HYOID
Ribcage - 12 pairs of ribs
Sternum (breastbone)
The Vertebral Column (Spinal Column or Backbone)

7 CERVICAL (NECK) VERTEBRAE,


12 THORACIC
5 LUMBAR,
5 FUSED VERTEBRAE INTO 1 SACRUM,
4 TO 5 SMALL FUSED VERTEBRAE INTO 1 COCCYX (YOUR TAIL BONE)

THE APPENDICULAR SKELETON - CONSIST OF THE BONES OF THE ARMS AND LEGS, SHOULDER, AND THE PELVIC GIRDLE.

THE PECTORAL GIRDLE CONSISTS OF 4 BONES, AND UPPER LIMBS CONSISTS OF 60 BONES (the hands and wrist contain 54 separate bones).
THE PELVIC GIRDLE CONSISTS OF 2 BONES AND THE LOWER LIMB CONSISTS OF 60 BONES (the ankles and feet contain 54 separate bones)

See Image of Skeleton with Labeled Bones

 

JOINTS:Ê WHERE TWO BONES MEET



Joints are responsible for keeping bones far enough apart so they do not rub against each other as they move. At the same time, joints hold the bones in place.

Joints work by attaching muscles which work in in pairs - ANTOGONISTIC MUSCLES - flexors & extensors



Muscles attach to bone via connective tissue called TENDONS
Muscles also attach to bones to each other via LIGAMENTS

 

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