Human Body Systems
Analyze how major body systems interact to maintain homeostasis. Emphasize nervous, endocrine, circulatory, respiratory, digestive, excretory, and immune systems.
A lesson of Biology, in Homeostasis, Body Systems, and Ecology, about 10 minutes.
By the end of this lesson, you will be able to identify the major human organ systems, describe each system's primary function, and explain how organ systems interact to maintain homeostasis.
The Big Idea
The human body is composed of ~37 trillion cells organized into tissues, organs, and organ systems. Each system has a specialized role, but no system works in isolation — homeostasis requires continuous coordination between systems.
Major Organ Systems
Integumentary System
- Organs: skin, hair, nails
- Functions: protection (barrier), temperature regulation (sweat, hair), sensory reception, vitamin D synthesis
Skeletal System
- Organs: bones, cartilage, ligaments
- Functions: support, protection (skull, ribcage), movement, blood cell production (bone marrow), mineral storage
Muscular System
- Organs: skeletal, cardiac, smooth muscle
- Functions: movement, posture, heat generation
Nervous System
- Organs: brain, spinal cord, peripheral nerves
- Functions: rapid signaling, integration, coordination, sensation
Endocrine System
- Organs: hypothalamus, pituitary, thyroid, adrenals, pancreas, gonads
- Functions: hormone secretion → long-term regulation of metabolism, growth, reproduction, stress response
Cardiovascular System
- Organs: heart, blood vessels, blood
- Functions: transport O₂, nutrients, wastes, hormones, immune cells throughout body
Respiratory System
- Organs: lungs, trachea, bronchi
- Functions: gas exchange (O₂ in, CO₂ out); pH regulation
Digestive System
- Organs: stomach, small intestine, large intestine, liver, pancreas
- Functions: mechanical and chemical digestion; nutrient absorption; waste elimination
Urinary System
- Organs: kidneys, ureters, bladder, urethra
- Functions: filter blood; eliminate nitrogenous wastes (urea); regulate water/salt balance and blood pH