Organisation of Living World Test - 4

Tendons and ligaments belong to connective tissues. Ligaments connect two or more bones together and help stabilize joints. Tendons attach muscle to bone. Tendons vary in size and are somewhat elastic and attach bones to muscles.

The total number of muscles in the body of a human being is 639.

Both muscular and skeletal systems protects the internal organs of the body.The muscles of the muscular system keep bones in place; they assist with movement by contracting and pulling on the bones.

Stripped muscles are attached to bones except in tongue. This exception is also seen in upper part of oesophagus.

Most busy organ is heart because it is continuously pumping blood to all the vital organs in the body to ensure their proper functioning all the time.

Tracheids are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts. Tracheids are one of two types of tracheary elements, vessel elements being the other.

In sclerenchyma, wall is lignified. Due to lignification, the cells lose their living characters at maturity.

Sieve tubes are suited for translocation of food because of broader lumen and perforated cross walls.

In aquatic plants, parenchyma cells have star like air cavities in between the cells. They are called aerenchyma. The air trapped in the cavities make the plants lighter in weight and help them to float in water.

Collenchyma is a mechanical tissue with unlignified walls.These cells are often found under the epidermis, or the outer layer of cells in young stems and in leaf veins.