Human Anatomy and Physiology: An Overview

Anatomy is the study of the structure of body parts, while Physiology is the study of how these parts function and work together. The human body is organized into several systems that maintain Homeostasis—a stable internal environment.

1. Levels of Organisation

The human body follows a hierarchical structure:

• Cells: The basic unit of life (e.g., muscle cells).
• Tissues: Groups of similar cells (e.g., nervous tissue).
• Organs: Different tissues working together (e.g., the heart).
• Organ Systems: Groups of organs performing a major function (e.g., the circulatory system).
• Organism: The complete human being.

2. Major Organ Systems

A. The Skeletal and Muscular Systems

• Function: Provide support, protection, and movement.
• Key Organs: Bones, joints, and muscles.

B. The Digestive System

• Function: Breaking down food into nutrients that the body can absorb.
• Key Organs: Mouth, esophagus, stomach, small intestine, large intestine, liver, and pancreas.

C. The Respiratory System

• Function: Exchange of gases ($O_2$ in and $CO_2$ out).
• Key Organs: Nose, trachea (windpipe), and lungs (containing alveoli).

D. The Circulatory System

• Function: Transporting oxygen, nutrients, and hormones to cells and removing waste products.
• Key Organs: Heart, blood, and blood vessels (arteries, veins, capillaries).

E. The Excretory System

• Function: Removing metabolic waste products from the blood.
• Key Organs: Kidneys, ureters, urinary bladder, and urethra.

F. The Nervous System

• Function: Controlling and coordinating body activities and responding to stimuli.
• Key Organs: Brain, spinal cord, and nerves.

3. The Vital Organs

Certain organs are considered "vital" because they are essential for survival:

1. Brain: The control center of the nervous system.
2. Heart: Pumps blood throughout the body.
3. Lungs: Facilitate breathing and gas exchange.
4. Liver: Filters blood and produces bile for digestion.
5. Kidneys: Filter blood to produce urine.

4. Key Physiological Processes

5. Summary Table: System Functions