Name the muscular tissue which is present in the iris of the eye and what is the shape of this cell?

The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. Eye color is defined by that of the iris.

The muscle cells of the iris are smooth muscle in mammals.

Smooth muscle

They occur as a bundle or sheets of spindle shaped cells. They have single centrally located nucleus in the centre of cytoplasm.

Although they do not have striations and sarcomeres, smooth muscle fibers do have actin and myosin contractile proteins, and thick and thin filaments.

They are Delicate, contractile thread called myofibrils that run longitudinally through the cell. They are found in walls of alimentary canal, internal organs, ducts of glands, stomach, bronchi, iris of eyes.

Functions of smooth muscles:

a) They do not work according to our will, so they are called involuntary muscles. Movement of food in alimentary canal, opening and closing of tubes are involuntary movement.

b) Help in contraction and relaxation of blood vessels.

Smooth muscle is also present in the eyes, where it functions to change the size of the iris and alter the shape of the lens.