Organ Systems Notes
Organ and Organ System Definitions
An organ is a structure composed of two or more kinds of tissues performing a complex function.
An organ system is a group of organs that together perform a more complex function than any individual organ.
Integumentary System
Structure: Consists of skin (the sole organ) and attached appendages including hair, nails, microscopic sense receptors, sweat glands, and oil glands.
Functions: Primary function is protection; also regulates body temperature, synthesizes Vitamin D, and acts as a sense organ for temperature, touch, pressure, pain, and vibration.
Skeletal System
Structure: Composed of bones (206 named adult bones, approximately 300 in babies, plus individual variable bones), cartilage, ligaments, and joints.
Functions: Provides body framework, protects the brain and internal organs, enables movement, stores minerals ( and phosphorus), and forms blood cells in red bone marrow.
Muscular System
Structure: Composed of voluntary (striated skeletal) muscle, involuntary (smooth) muscle in walls of hollow organs (arteries, veins, airways, uterus, GI tract, bladder, ureters, iris of the eye), and cardiac muscle in the heart wall.
Functions: Enables movement and fluid movement through organs; functions with the skeletal system as the skeletomuscular system.
Nervous System
Structure: Divided into the Central Nervous System (brain, spinal cord) and Peripheral Nervous System (cranial nerves, spinal nerves, sense organs).
Functions: Facilitates communication between organs, integrates and controls body functions, and recognizes sensory stimuli.
Endocrine System
Structure: Includes pituitary gland, pineal gland, hypothalamus, thyroid gland, parathyroid glands, thymus gland, adrenal glands, pancreas, ovaries (female), and testes (male).
Functions: Provides slow, long-duration communication, integration, and control; combines with the nervous system as the neuroendocrine system.
Cardiovascular System
Structure: Composed of the heart, blood vessels, and blood pumped within a closed circuit.
Functions: Transports substances throughout the body, regulates body temperature, and provides immunity.
Lymphatic and Immune Systems
Lymphatic System: Includes lymphatic vessels, lymph nodes, tonsils, thymus, and spleen; transports lymph and provides immunity.
Immune System: Consists of protective phagocytes and secretory cells that produce defensive protein compounds (antibodies, complements); performs phagocytosis and chemical protection against harmful agents.
Respiratory System
Structure: Consists of nose, pharynx, larynx, trachea, bronchi, and lungs.
Functions: Exchanges carbon dioxide for oxygen in alveoli, filters air irritants, and regulates acid-base balance.
Digestive System
Structure: Primary organs forming the gastrointestinal (GI) tract include mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anal canal; accessory organs include teeth, salivary glands, tongue, liver, gallbladder, pancreas, and appendix.
Functions: Mechanically and chemically breaks down food, absorbs nutrients, and eliminates undigested waste (feces).
Urinary System
Structure: Composed of kidneys, ureters, urinary bladder, and urethra (which is part of both urinary and reproductive systems in males).
Functions: Cleans blood of waste (excreted as urine), regulates electrolyte balance, water balance, and acid-base balance.
Reproductive Systems
Male Structure: Gonads (testes), vas deferens, urethra, prostate, and external genitalia (penis and scrotum).
Female Structure: Gonads (ovaries), uterus, uterine (fallopian) tubes, vagina, external genitalia (vulva), and mammary glands (breasts).
Functions: Produces sex cells (sperm/ova), transfers and fertilizes sex cells, supports offspring development, birth, and nourishment, produces sex hormones, and ensures survival of genes.
Body Integration and Organ Replacement
Homeostasis: The 11 body systems are structurally and functionally interdependent to maintain homeostasis.
Organ Replacement: Loss of function in nonvital organs is treated with prostheses (e.g., artificial limbs, dialysis machines, pacemakers); loss of function in vital organs is immediately life-threatening and treated via surgical transplants, free-flap surgeries, or stem cell treatment.