Organ Systems

Definitions and Concepts

An organ is a structure composed of two or more types of tissues that work together to perform specific, complex functions. An organ system is a group of organs that collaborate to carry out major body functions more efficiently than any single organ could alone.

Integumentary System

Structure

• Skin: The largest organ, serving as the body's outer covering.

• Appendages: Hair, nails, microscopic sense receptors, sweat glands, and oil glands.

Functions

• Protection: Acts as a barrier against mechanical injury, pathogens, and water loss.

• Regulation of body temperature: Through sweat production and blood flow regulation.

• Synthesis of chemicals: Such as vitamin D.

• Sense organ: Contains receptors for touch, temperature, and pain.

Skeletal System

Structure

• Bones: 206 named bones form the human skeleton.

• Cartilage: Cushions and connects bones at joints.

• Ligaments: Bands of fibrous tissue connecting bones.

• Joints: Sites where bones meet, allowing movement.

Functions

• Support: Provides a framework for the body.

• Protection: Shields the brain and internal organs.

• Movement: Facilitates movement with muscles and joints.

• Mineral storage: Stores calcium and phosphorus.

• Blood cell formation: Occurs in bone marrow (hematopoiesis).

Muscular System

Structure

• Skeletal muscle: Voluntary, striated muscle attached to bones.

• Smooth muscle: Involuntary muscle in organ walls.

• Cardiac muscle: Specialized muscle in the heart wall.

Functions

• Movement: Enables body movement and facial expressions.

• Posture: Maintains body position.

• Heat production: Generates heat during contraction.

Nervous System

Structure

• Central Nervous System (CNS): Brain and spinal cord.

• Peripheral Nervous System (PNS): Cranial and spinal nerves, sense organs.

Functions

• Communication: Transmits signals between body parts.

• Integration: Processes sensory input and coordinates responses.

• Control: Regulates body functions and activities.

• Recognition of stimuli: Detects changes in the environment.

Endocrine System

Structure

• Pituitary gland

• Pineal gland

• Hypothalamus

• Thyroid gland

• Parathyroid glands

• Thymus gland

• Adrenal glands

• Pancreas

• Ovaries (female)

• Testes (male)

Functions

• Communication, integration, and control: Similar to the nervous system but slower and longer-lasting.

• Hormone production: Regulates metabolism, growth, and reproduction.

Cardiovascular System

Structure

• Heart: Muscular pump that circulates blood.

• Blood vessels: Arteries, veins, and capillaries.

Functions

• Transportation: Delivers oxygen, nutrients, and hormones; removes wastes.

• Regulation: Maintains body temperature and pH balance.

• Immunity: Transports immune cells and antibodies.

Lymphatic and Immune Systems

Lymphatic System Structure

• Lymphatic vessels

• Lymph nodes and tonsils

• Thymus

• Spleen

Lymphatic System Functions

• Transports lymph (fluid containing white blood cells)

• Immunity: Filters pathogens and debris

Immune System Structure

• Phagocytes (protective cells)

• Secretory cells (produce defensive proteins)

• Antibodies and complement proteins

Immune System Functions

• Phagocytosis of bacteria

• Chemical defense against harmful agents

Respiratory System

Structure

• Nose

• Pharynx

• Larynx

• Trachea

• Bronchi

• Lungs

Functions

• Gas exchange: Oxygen in, carbon dioxide out

• Filtration of irritants from air

• Regulation of acid-base balance

Digestive System

Structure

• Primary organs (GI tract): Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anal canal

• Accessory organs: Teeth, salivary glands, tongue, liver, gallbladder, pancreas, appendix

Functions

• Mechanical and chemical digestion of food

• Absorption of nutrients

• Elimination of undigested waste (feces)

• Appendix: Holds bacteria that assist digestion

Urinary System

Structure

• Kidneys

• Ureters

• Urinary bladder

• Urethra (also part of male reproductive system)

Functions

• Removes waste products from blood (urine formation)

• Regulates electrolyte, water, and acid-base balance

Reproductive System

Male Structure

• Gonads: Testes

• Vas deferens

• Urethra

• Prostate

• External genitalia: Penis and scrotum

Female Structure

• Gonads: Ovaries

• Uterus

• Uterine (fallopian) tubes

• Vagina

• External genitalia: Vulva

• Mammary glands (breasts)

Functions

• Survival of genes

• Production of sex cells (sperm and ova)

• Transfer and fertilization of sex cells

• Development, birth, and nourishment of offspring

• Production of sex hormones

Body as a Whole

Integration of Organ Systems

• There are 11 major body systems: Integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic/immune, respiratory, digestive, urinary, and reproductive.

• No system functions independently; all are interrelated and interdependent.

• Homeostasis is maintained by the coordinated function of all systems.

Organ Replacement

Concepts

• Loss of function in nonvital organs is not immediately life-threatening; vital organ failure is.

• Organ replacement can involve prostheses (artificial devices) or transplantation (surgical replacement of organs).

• Modern approaches include free-flap surgeries and stem cell treatments.

Examples of Prostheses

• Cochlear implants, artificial limbs, contact lenses, pacemakers, dialysis machines, artificial joints, insulin infusion devices, artificial heart pumps.