2: Body systems overview

Section 1: Foundational Concepts - 2: Body Systems Overview

The human body functions through the integrated operation of eleven primary organ systems. Each system consists of specific organs and tissues working together to perform essential physiological tasks. Understanding these systems provides the structural and functional foundation for anatomy.

1. Integumentary System: Forms the body's external barrier. Includes skin (epidermis, dermis), hair, nails, and glands (sweat, sebaceous). Functions: Protection (physical, microbial, UV), thermoregulation, sensation (touch, temperature, pain), vitamin D synthesis, and water retention.
2. Skeletal System: Provides structural support and protection. Comprises bones, cartilage, ligaments, and joints. Functions: Support for the body, protection of internal organs (e.g., skull protects brain), movement facilitation (attachment for muscles), mineral storage (calcium, phosphate), and blood cell production (hematopoiesis in bone marrow).
3. Muscular System: Enables movement and generates heat. Consists of skeletal muscles (voluntary, attached to bones), smooth muscle (involuntary, in organs/vessels), and cardiac muscle (involuntary, heart). Functions: Locomotion, posture maintenance, stabilization of joints, heat production (thermogenesis), and propulsion of substances through hollow organs (peristalsis).
4. Nervous System: Acts as the body's rapid control and communication network. Includes the brain, spinal cord, peripheral nerves, and sensory organs (eyes, ears). Functions: Detects internal/external changes (sensation), processes sensory input, initiates rapid responses (motor output), integrates activities of other systems, and underlies cognition and emotion.
5. Endocrine System: Regulates body activities slowly via hormones. Comprised of hormone-producing glands (pituitary, thyroid, adrenal, pancreas, ovaries, testes) and tissues. Functions: Controls growth, metabolism, reproduction, fluid/electrolyte balance, stress responses, and development through chemical messengers (hormones) secreted into the bloodstream.
6. Cardiovascular System: Transports substances throughout the body. Includes the heart, blood vessels (arteries, veins, capillaries), and blood. Functions: Delivers oxygen and nutrients to tissues, removes carbon dioxide and metabolic wastes, transports hormones and immune cells, and aids in thermoregulation.
7. Lymphatic System (Immune System): Defends the body and maintains fluid balance. Comprises lymph nodes, lymphatic vessels, spleen, thymus, tonsils, and bone marrow-derived cells (lymphocytes). Functions: Returns interstitial fluid to the bloodstream (lymph), houses immune cells, filters pathogens and debris, and mounts specific immune responses.
8. Respiratory System: Facilitates gas exchange. Includes the nasal cavity, pharynx, larynx, trachea, bronchi, and lungs (alveoli). Functions: Obtains oxygen from air, expels carbon dioxide, regulates blood pH via gas exchange in alveoli, and houses receptors for smell.
9. Digestive System: Processes nutrients from food. Consists of the alimentary canal (mouth, esophagus, stomach, small/large intestine, rectum, anus) and accessory organs (liver, pancreas, gallbladder). Functions: Ingests food, mechanically and chemically breaks it down (digestion), absorbs nutrients and water into the bloodstream, and eliminates indigestible waste (feces).
10. Urinary System (Renal System): Regulates blood composition and eliminates waste. Includes kidneys, ureters, urinary bladder, and urethra. Functions: Filters blood to remove metabolic wastes (urea, creatinine), regulates blood volume, pressure, pH, and electrolyte concentrations (Na+, K+, Ca2+), and produces urine.
11. Reproductive System: Responsible for producing offspring. Male system includes testes, epididymides, ductus deferens, accessory glands, and penis. Female system includes ovaries, uterine tubes, uterus, vagina, and mammary glands. Functions: Produces gametes (sperm/ova), secretes sex hormones, supports fertilization, pregnancy (female), and development of offspring.