The body's ability to resist a particular disease
Immunity
The nervous system that consists of the brain and spinal cord
Central
The largest lymphatic organ
Spleen
This carries messages to your brain, causing you to hear
Auditory Nerve
A person trained to examine eyes and prescribe glasses
Optometrist
The chemical which destroys most of the harmful bacteria that enter your stomach
Hydrochloric acid
This runs from the base of your brain to your lower back
Spinal cord
White blood cells inside lymph nodes
Lymphocytes
Sound waves travel from the outer ear through this to reach the eardrum
Auditory canal
This gives the eye its color
Iris
Bacteria and viruses that cause diseases
Pathogens
The hairlike projections that line the mucous membrane
Cilia
Transportation tubes for lymph
Lymph vessels
These receptors send messages to your brain which allow you to smell
Olfactory
The tough outer layer of the eye
Sclera
The enzyme that kills bacteria in your tears and perspiration
Lysozyme
The largest organ of your body
Enlarged bunches of lymphatic tissue
Lymph nodes
The "wires" of your communication system
Nerves
The center of the iris through which light passes
Pupil
The special kind of skin cells that line your mouth, nose, and throat
Mucous membrane
The largest part of the brain, it controls thinking, reasoning, and memory
Cerebrum
Located behind your sternum and between your lungs, this gland tells your white blood cells when to attack foreign cells and when to stay put. It has an important role in the way your immune system works.
Thymus
The hollow space in your skull that surrounds each eye
Eye socket
This becomes thicker when you look at close objects and thinner when you look at distant ones
Lens