The Skin:

Body's first line of defence.
Acts as barrier, prevents entry of microorganisms.
Outer most layers make up epidermis - consists of dead cells, strengthened by the protein keratin.
Sebaceous glands of lower dermis produce water proofing oils (sebum) - keep hair follicles relatively free of bacteria.
Sweat glands produce sweat - contains enzyme lysozyme, destroys bacterial cell walls, results in lysis of bacteria.
Bacteria naturally living on skin compete with pathogens.

Respiratory System:

Surface of organs exposed to outside world (respiratory, digestive and urinary system) act as physical barriers to microbe attack.
Surfaces covered with epithelial tissue - epithelial cells tightly packed and sit on a basement membrane.
Mucus produced in respiratory tract traps bacteria and other microbes - contains lysozyme.
Epithelial cells in upper parts of respiratory system have cilia on outside surface.
Cilia beat steadily, causing net flow of mucus (with entrapped microbes) up bronchioles and trachea towards throat where it is then swallowed.

	Created by Melissa Lamb almost 7 years ago

AS - Level Biology (Cell Recognition & The Immune System) Note on Defence Mechanisms, created by Melissa Lamb on 07/06/2017.