Cilia and Ciliary Movements
Cilia
Cilia are small, slender, and hair-like structures on the surface of cells.
Types
Nonmotile Cilia
Cannot move on their own.
Play sensory role
Motile Cilia
Can move on their own → their movement generates flow in the fluid on the surface of the cell.
Structure of a Cilium
Basal Body
Cilium arises from its own basal body.
Basal body is a centriole immediately beneath the cell membrane
Axoneme
Made up of microtubules
2 complete microtubules at the center
9 pairs of microtubules at the periphery.
Each peripheral pair is connected to its neighboring pairs by dynein arms.
Cell Membrane
Covers the Axoneme
Ciliary Movement
Cilia move in a whip-like motion.
Forward Stroke
is a rapid forward thrusting movement.
Moves the fluid on the surface in forward direction.
Backward Stroke
is a slow dragging movement in backward direction.
Produces minimal effect movement of fluid.
Mechanism of Ciliary Movement
Dynein arm of peripheral pairs of tubules crawls over its neighbor pair → As all the pairs are fixed at the base, the crawling results in bending of the cilia.
Dynein arm uses energy from ATP to produce this movement.
Importance of Ciliary Movement
In Respiratory Tract
Ciliary movement on the epithelial cell of the airway generates flow in the mucous → move the inhaled foreign particles and pathogens in nose and lower respiratory tract to pharynx → swallowed → respiratory tract is cleared.
In Fallopian Tube
Move the ovum from ovary to uterus.