“The Knowledge Library”

Knowledge for All, without Barriers…

An Initiative by: Kausik Chakraborty.

“The Knowledge Library”

Knowledge for All, without Barriers……….
An Initiative by: Kausik Chakraborty.

The Knowledge Library



Ball and Socket joint – The rounded end of one bone fits into the cavity of the other bone. Such a joint allows movement in all directions. [Shoulder and arm]

Pivot – head joins our neck at a pivot joint.

Hinge Joint – only allows back and forth movements. [Elbow]

Fixed joints – immovable joint [upper jaw and head]

Cartilage – Additional parts of the skeleton but not hard as bones. [Ear]

Muscles – Required to make a movement. Two muscles are needed to move a bone. While one contracts the other expands. Contracting bone moves a muscle in its direction and then its paired muscle expands. When the other muscle contracts the bone moves in the second direction. This causes movement.

Animal Tissues

Animal tissues are of multiple types like:

Epithelial tissue: it is a protective tissue that covers all parts of the body. It has no intercellular space. It allows the material to pass through it but only selective materials. It has many types like squamous, ciliated, columnar, tall, etc depending on the structure.

Connective tissue: Blood, bones [made of calcium and phosphorous compounds] and ligaments [join bones together], cartilage [smoothens bone surfaces at joints], and tendons [connect muscles and bones] are types. Adipose connective tissue stores fats between internal organs to act as an insulator.

Muscular [striated, unstriated, and cardiac] and nervous tissues [made of neurons that receive and conduct impulses] are other types.


Muscles can only pull not push.

Fine hair and mucus in our noses prevent dust from entering the human body.

Earthworm eats their way through the soil. Its body throws undigested material that it eats; this makes the soil more fertile. It breathes through its skin. Air present inside the water and soil is used for breathing by the earthworms. Insects have tracheas to breathe.

Birds have hollow bones.

Snails move with the help of a muscular foot.

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