Key systems and their primary components include:

1. Nervous System – Includes the brain, spinal cord, and peripheral nerves.
2. Cardiovascular System – Comprises the heart and blood vessels.
3. Respiratory System – Involves the lungs and airways.
4. Digestive System – Consists of the mouth, esophagus, stomach, intestines, liver, and related organs.
5. Musculoskeletal System – Encompasses bones, muscles, and connective tissues.
6. Endocrine System – Made up of glands (like the thyroid and adrenal glands) that produce hormones.
7. Urinary System – Includes the kidneys, bladder, and related structures.
8. Reproductive System – Comprises the organs involved in sexual reproduction.

Each of these systems works in unison to maintain the body’s overall function and health.