Bones and Skeleton

Summary

LearnNext Lesson Video

 
Skeleton
The skeleton is an internal framework of all the bones and cartilage in the human body. It is made up of 206 bones. It gives the shape and structure to support the body. Babies at birth possess 300 separate bones. Later some of the bones fuse together and finally an adult has 206 bones making up the skeleton.
  • Bone is a type of fibrous connective tissue. Bones provide support to the structures in the body. Bone cells are embedded in a hard matrix composed of calcium and phosphorus compounds. Bones also anchor the muscles. The strongest longest and the heaviest bone in the human body is femur. It is located in the thigh region of the leg. 
  • Cartilage is a soft elastic tissue that covers the bones at the region of the joints. It offers support to the structure. It connects the bones together. Cartilage has widely spaced cells suspended in a matrix of proteins and sugars. It is found in the nose, ears, and the rings of the trachea to give flexibility. 


Types of bones
Bones can be of different types based on their rigidity.
  • Round and long: Bones can be round and long as in limbs.
  • Ring like bones with outgrowths: Bones in the vertebrae are ringlike with outgrowths on both the sides.
  • Flat and strong: Bones in the skull are flat and strong.
  • Girdles: Bones are present in the form girdles in the shoulder region and pelvic region.

Parts of skeleton
Human skeleton is of two parts, axial skeleton and appendicular skeleton.
Axial skeleton includes the skull, vertebral column and the rib cage.
Appendicular skeleton includes shoulder bone, pelvic bone, arm bone, and the leg bone.

Axial skeleton
a) Skull
Skull is a hard structure made up of small bones. It forms the cranium and the face. Cranium protects the brain.
  • Skull is formed by 22 bones out of which 8 bones are fixed together to form the cranium and 14 bones fuse to form the face.
  • The only bone which has movable joint is the lower jaw. This movable joint is supported by muscles and ligaments.
  • Skull placed on the top of the backbone can be moved up, down and sidewards.

b) Vertebral column
Vertebral column running at the back of the body is also called as spine or the backbone.
  • It is in the trunk region to offer support to the upper part of the body.
  • Vertebral column is made up of individual bones called as vertebrae.
  • Total vertebral column consists of 7 cervical vertebrae, 12 lumbar vertebrae, 5 fused sacral and 3 fused coccygeal vertebrae.
  • Vertebral column runs from the base of the skull to the hip bone forming a tube. Spinal cord passes through this hollow tube.
  • Movement of neck can be up, down or sidewards.
  • Vertebrae are joined by gliding joints which offer spring movement to the backbone. Body can be bent back, front or sidewards.

Functions of vertebral column
  • It protects the spinal cord.
  • It supports the head.
  • It serves as an attachment for the ribs.
  • It provides support and place of attachment for the pectoral and pelvic girdle.
  • It provides movement for the human skeleton.
  • It helps in walking and standing erect, correct posture.

c) Rib cage
Rib cage occupies the chest region. It is cone-shaped structure made up of 12 pairs of ribs.
  • Ribs are attached to vertebrae at the back which curve around to form a cage.
  • 10 pairs of ribs are attached to the breast bone at the front.
  • 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
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.

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Activities & Simulations


Activity 1
Manchester.ac.uk has composed an user interface on different types of bones forming the skeletal system in our body. It provides information about functions of the bones. The entire labelled diagram of a skeleton is represented. If a student clicks on a particular part, information about that part is displayed. An added feature is a drag and drop option to fit a particular bone into its right place in the skeleton.  
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Activity 2
Rigb.org has created an interactive module which allows the student to build skeletons of different animals. Stepwise instructions are given to the user to complete the activity. This module helps the student to know about the internal structure of the skeleton present in different organisms.
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