Human Body Systems, Diseases and Vitamins

Key body systems

• Digestive – digestion starts in the mouth (salivary amylase); most absorption occurs in the small intestine. The liver is the largest gland and makes bile.
• Circulatory – the heart has 4 chambers; arteries carry blood away from the heart, veins towards it. Normal BP ≈ 120/80 mm Hg.
• Respiratory – gas exchange in the alveoli of the lungs.
• Nervous – brain, spinal cord, nerves; the neuron is the basic unit.

Vitamins and deficiency diseases

Vitamin	Deficiency
A	Night blindness
B1	Beriberi
C	Scurvy
D	Rickets
K	Poor blood clotting

Diseases by cause

Bacteria: tuberculosis, cholera, typhoid. Virus: COVID-19, polio, measles, AIDS. Protozoa: malaria (Plasmodium, spread by female Anopheles).

Exam tips

1. Vitamin D is made in skin under sunlight.
2. Universal donor: O negative; universal recipient: AB positive.

Analogy

The human body is like a well-run railway network. The heart is the main pumping station, blood vessels are the tracks, blood cells are the trains carrying oxygen and food, and the brain is the central control room sending signals down the nerve 'cables'.