The following are identified systems of the human body followed by their function and cellular evidence. 

For more information on the general systems of the human body see: 
BODY BASICS: WHAT THE BODY'S SYSTEMS DO 

1. Cardiovascular System:

• Function: Transports oxygen, nutrients, hormones, and waste products throughout the body.

• Cellular Evidence: This system is primarily made up of three types of cells:

  • Endothelial cells lining the blood vessels, ensuring smooth blood flow.

  • Red blood cells (erythrocytes) that carry oxygen to tissues and remove carbon dioxide.

  • White blood cells (leukocytes) which play crucial roles in immunity.

2. Nervous System:

• Function: Sends, receives, and interprets information from all parts of the body.

• Cellular Evidence: Neurons are the primary cells in this system, transmitting electrical signals across the body. Different types of neurons (sensory, motor, interneurons) have specialized functions, allowing for communication, interpretation, and action based on stimuli.

3. Digestive System:

• Function: Breaks down food into nutrients, which can be absorbed and utilized by the body.

• Cellular Evidence: This system features:

  • Epithelial cells in the stomach lining that secrete gastric juices to aid in digestion.

  • Exocrine cells in the pancreas producing digestive enzymes.

  • Enterocytes in the intestines that absorb nutrients.

4. Respiratory System:

Function: Facilitates the exchange of oxygen and carbon dioxide between the body and the environment.

• Cellular Evidence: 

  • Ciliated epithelial cells line the airways, helping to move mucus and trapped particles out of the lungs.

  • Alveolar cells in the lungs allow for the exchange of gases with the blood.

5. Musculoskeletal System:

Function: Provides support, movement, and protection.

Cellular Evidence:

• Myocytes or muscle cells contract to facilitate movement.

• Osteocytes, the primary cell type in bones, help maintain bone structure and mineral content.

6. Endocrine System:

Function: Produces and secretes hormones to regulate bodily processes.

Cellular Evidence: Endocrine glands contain cells that produce and release specific hormones. For example, the beta cells of the pancreas produce insulin, a hormone vital for glucose regulation.

7. Lymphatic/Immune System:

Function: Defends the body against pathogens and maintains fluid balance.

Cellular Evidence: Lymphocytes, like T-cells and B-cells, play a key role in immune responses, targeting and neutralizing pathogens.