Human Skeleton System

 Human Skeleton System

   

Human Skeleton System

The human skeleton is an internal framework in the human body providing structure, support, protection, and movement.

The skeleton system comprises of bone, cartilages and joints. 

The human skeleton is made up of 206 bones.

There are basically three components of Human Skeleton System:

•  Bones : Bone is a tough and rigid form of fibrous connective tissue. Bones provide strength and support to human skeleton.
• Cartilage : Cartilage is a soft elastic tissue that covers the bones at the region of the joints. It connects the bones together and offers support the skeleton structure. Cartilage is not as tough and rigid as bone.
• Joints : Joints are very important component of human skeleton because they allow different types of movements at different locations. If the skeleton were without joints, no movement would have taken place.

Human Skeleton has two parts

• Axial Skeleton
• Appendicular Skeleton

Axial skeleton

Axial skeleton consists of (1) Skull (2) Vertebral column and (3) Thoracic cage.

Skull:

 Skull is a hard structure made up of small bones.

The skulls are divided into two parts: Cranium bones and facial bones.

Skull consists of 22 bones out of which 8 bones are fixed together to form the cranium and 14 bones fuse to form the face.

 Cranium encloses and protects the brain. The cranium bones are flat and immovable.

The facial bones form upper and lower jaws. The upper jaw is attached to the cranium. The lower jaw is movable and helps us to talk and eat.

Vertebral Column or back bone:

It is a flexible column of vertebrae, connecting the base of the skull to the hips. It is also called spine.

It is composed of 33 vertebrae which is small ring-like bones which are divided into 5 regions: 

(1)Cervical ( Neck Region) – 7 bones

(2)Thoracic (Chest region) – 12 bones

(3)Lumbar (Belly region) – 5 bones

(4)Sacral (Hip region) – 5 bones

(5)Coccygeal (Tail region)- 4 bones

The bones of neck region, chest and belly comprise of 24 bones and are joined end to end with the help of elastic cartilage.

The four bone of coccygeal region are fused together as  single bone.

The five sacral bones are fused together as a single bone.

Vertebral column runs from the base of the skull to the hip bone forming a tube. Spinal cord passes through this hollow tube.

Rib Cage: 

Rib cage occupies the chest region. It is cone-shaped structure made up of 12 pairs of ribs and median plate like structure called sternum.

Ribs are long, curved, rod like bones attached to vertebrae at the back to form a cage.

The first 10 pairs of ribs are attached to the breast bone at the front.

The 2 pairs of lower ribs are free at front. These are called as free-floating ribs.

Rib cage is set up in such a way that it can contract and expand during the process of breathing.

Rib cage protects the underlying lungs, heart and some part of liver etc.

              

Appendicular Skeleton

Appendicular skeleton includes (1) shoulder bone (2) Pelvic bone (3) Arm bone and (4) The leg bone.

a) Shoulder bone

Shoulder bone is formed by collar bone at the front and the shoulder blade at the back.

•The collar bone is supported by breast bone at one end and the shoulder blade at the other end.

•The shoulder bone encloses a socket like cavity into which fixes the ball of the upper arm.

•This forms a ball and socket joint. This girdle is also called as pectoral girdle.

b) Pelvic bone

Pelvic bone is also called as pelvic girdle. It is made up of strong bones to balance entire weight of the body.

•Pelvic girdle is formed by five fused vertebrae at the back and form a cavity in the centre while reaching the front part.

•The thigh bones are attached to either side of the girdle with a ball and socket joint.

c) Arm bone

Arm bone is the upper limb made up of humerus, radius, ulna, carpals, metacarpals and phalanges. All these bones are joined by hinge joints which allow the limb to move only in one direction.

•Humerus makes up the upper arm.

•Fore-arm is made up of radius and ulna.

•Wrist is made up of carpals.

•Palm is made up of metacarpals.

•Fingers are made up of phalanges

d) Leg bone

Leg bone is the lower limb made up of femur, tibia, fibula, tarsals, metatarsals and phalanges. All these bones are joined by hinge joints which allow the limb to move only in one direction. Knee is covered by a cap like structure called as patella or a knee cap.

•Femur makes up the thigh bone.

•Leg is made up of tibia and fibula.

•Ankle is made up of tarsals.

•Foot is made up of metatarsals.

•Toes are made up of phalanges.