Overview
This lecture introduces the 11 major human body systems, describing their general functions and key structures, and emphasizes how these systems work together.
Organization of the Human Body
- The human body is made of trillions of specialized, organized cells.
- Cells group into tissues, tissues form organs, and organs form organ systems.
- Organ systems function together rather than in isolation.
Circulatory System
- Transports oxygen, carbon dioxide, and nutrients via blood.
- Heart pumps blood and has four chambers and valves.
- Arteries carry blood away from the heart, veins return it, capillaries connect them.
Digestive System
- Breaks down and absorbs nutrients from food.
- Starts in the mouth and continues through stomach, small intestine (villi absorb nutrients), and large intestine (reabsorbs water).
- Includes accessory structures to aid digestion.
Endocrine System
- Consists of glands that secrete hormones acting as chemical messengers.
- Hormones regulate growth, metabolism, and stress response.
Excretory System
- Maintains water and solute balance and eliminates metabolic wastes like urea and carbon dioxide.
- Involves organs such as kidneys (remove blood wastes), liver, skin, and lungs.
- Kidneys have nephrons; the urinary tract includes bladder, ureters, and urethra.
Integumentary System
- Includes skin, hair, nails, and sebaceous (oil) glands.
- Protects the body, regulates temperature, and prevents water loss.
- Skin has three layers: epidermis, dermis, hypodermis.
Lymphatic and Immune System
- Collects, filters, and returns lymph fluid to blood, aiding immunity.
- Structures include lymph nodes, thymus, spleen, tonsils, and bone marrow.
- White blood cells and antibodies target pathogens.
Muscular System
- Enables movement by working with bones.
- Contains three major muscle types: skeletal, smooth, and cardiac.
Nervous System
- Coordinates voluntary and involuntary actions.
- Central nervous system: brain and spinal cord; peripheral nervous system: nerves throughout the body.
- Neurons and glia enable communication.
Reproductive System
- Allows for reproduction via internal and external structures.
- Female ovaries produce eggs; male testes produce sperm.
Respiratory System
- Facilitates oxygen intake and carbon dioxide expulsion.
- Includes trachea, lungs, and alveoli (site of gas exchange).
Skeletal System
- Provides body support, organ protection, and produces blood cells in bone marrow.
- Adult skeleton has 206 bones, divided into axial and appendicular skeleton.
Key Terms & Definitions
- Cell — Basic unit of life in the body.
- Tissue — Group of similar cells performing a function.
- Organ — Structure composed of tissues working together for a function.
- Organ System — Group of organs performing major body functions.
- Hormone — Chemical messenger produced by glands.
- Nephron — Functional unit of the kidney.
- Alveoli — Air sacs in lungs where gas exchange occurs.
Action Items / Next Steps
- Review the 11 body systems and memorize their general functions.
- Study major structures associated with each system.
- Understand examples of interactions between systems.