Human Body Systems

The Integumentary System
  • Composed of skin, hair, and nails.
  • Functions:
    • Barrier: Protects against infection and injury.
    • Thermoregulation: Regulates body temperature.
    • Waste Removal: Removes waste from the body (e.g., sweat).
    • Protection from UV Light: Shields underlying tissues from harmful radiation.
Skin Structure
  • Epidermis:
    • Outer layer, mainly composed of dead cells.
    • Contains keratin (for strength) and melanocytes (produce melanin, skin pigment).
  • Dermis:
    • Inner layer with blood vessels, nerves, glands, smooth muscle, and hair follicles.
    • Functions in temperature regulation and includes sweat glands and sebaceous glands (produce sebum).
  • Subcutaneous Layer (Hypodermis):
    • Primarily composed of adipose (fat) cells.
Skin Disorders
  • Carcinomas: Skin cancers arising from non-pigmented cells, high cure rate.
  • Malignant Melanoma: Skin cancer occurring in pigment-producing melanocytes, low cure rate.
  • Acne: Caused by clogged oil ducts leading to infection.
  • Psoriasis: Inherited condition characterized by rapid growth of epidermal cells, resulting in scaly white skin.
Hair and Nails
  • Hair:
    • Protects the scalp from UV light and prevents entry of particles (e.g., in nose, ears, eyes).
  • Nails:
    • Protect fingertips, composed heavily of keratin, grow from the nail root.
The Skeletal System Functions
  • Support: Provides structural support for the body.
  • Protection: Shields internal organs.
  • Mobility: Facilitates movement.
  • Mineral Storage: Stores vital minerals.
  • Blood Cell Formation: Site of hematopoiesis (blood cell formation).
Bone Structure
  • Components:
    • Osteocytes: Mature bone cells.
    • Osteoblasts: Cells that build bone.
    • Osteoclasts: Cells that break down bone.
  • Haversian Canals: Contain blood vessels and nerves.
  • Bone Marrow: Red marrow produces blood cells.
  • Periosteum: The tough connective tissue covering bones.
  • Ossification: The process of bone tissue formation, with most bones ossifying from cartilage.
Joints
  • Types:
    • Immovable: Skull sutures.
    • Slightly Movable: Vertebrae.
    • Freely Movable:
    • Ball and Socket: Hip, shoulder.
    • Hinge: Elbow.
    • Pivot: Neck.
    • Saddle: Thumbs.
  • Components:
    • Ligaments: Connective tissues that hold bones together.
    • Bursae: Sacs filled with synovial fluid that lubricate joints.
Common Joint Problems
  • Sprains: Injuries caused by forcible twisting.
  • Arthritis: Inflammation of joints.
  • Bursitis: Inflammation of the bursa.
  • Rheumatoid Arthritis: An autoimmune condition where the immune system attacks joints.
The Muscular System
  • Muscle Types:
    • Skeletal Muscle: Voluntary, striated muscle attached to bones (via tendons).
    • Cardiac Muscle: Involuntary, striated muscle of the heart.
    • Smooth Muscle: Involuntary, non-striated muscle found in hollow organs (e.g., blood vessels, stomach).
Muscle Contraction
  • Components:
    • Sarcomere: The unit of a muscle fiber.
    • Thick Filaments: Composed of myosin.
    • Thin Filaments: Composed of actin.
  • Process: Contraction occurs as thin filaments slide over thick filaments, shortening the sarcomere; ATP is required.
The Digestive System
  • Process Overview: Food passes through the digestive tract, is broken down, and nutrients are absorbed.
  • Mouth: Begins digestion.
    • Mechanical: Chewing.
    • Chemical: Enzymes in saliva (e.g., amylase breaks down carbohydrates).
  • Esophagus: Moves food as a bolus to the stomach through peristalsis.
  • Stomach: Site of both chemical (HCl, pepsin) and mechanical digestion, producing chyme.
Accessory Organs
  • Pancreas:
    • Produces insulin/glucagon and digestive enzymes (lipase, trypsin, amylase).
  • Liver: Produces bile for lipid emulsification.
  • Gallbladder: Stores bile.
The Respiratory System
  • Airway Path: Nose/mouth → pharynx → trachea → larynx → bronchi → bronchioles → alveoli (gas exchange site).
  • Gas Exchange: Oxygen and carbon dioxide are exchanged across alveolar membranes.
Breathing Mechanics
  • Diaphragm:
    • Contracts to increase chest volume (inhalation).
    • Relaxes to decrease volume (exhalation).
  • Regulation: Controlled by the medulla oblongata, which monitors CO₂ levels.
The Circulatory System
  • Structure: Composed of the heart, blood vessels, and blood.
  • Heart Chambers:
    • Atria: Upper chambers receiving blood.
    • Ventricles: Lower chambers pumping blood.
  • Types of Circulation:
    • Pulmonary: Right side pumps blood to lungs; oxygen-poor blood gains oxygen.
    • Systemic: Left side pumps oxygen-rich blood to the body.
Blood Vessels
  • Arteries: Carry oxygen-rich blood (except pulmonary artery).
    • Aorta: Major artery from the heart.
  • Capillaries: Sites of gas exchange.
  • Veins: Carry oxygen-poor blood back to the heart (except pulmonary vein).
Blood Composition
  • Plasma: Liquid component, mostly water.
  • Formed Elements:
    • Red Blood Cells: Transport oxygen; contain hemoglobin.
    • White Blood Cells: Immune components (phagocytes, lymphocytes).
    • Platelets: Cell fragments that assist in clotting.
The Lymphatic System
  • Functions: Collects excess fluid, absorbs nutrients, filters bacteria/pathogens, and aids in immune responses.
  • Organs: Thymus (T cell maturation), spleen (removes damaged blood cells).
The Excretory System
  • Functions: Eliminates metabolic wastes (excess salts, CO₂, urea), regulates blood pH/water content.
  • Structures:
    • Kidneys: Filter blood and maintain homeostasis.
    • Ureters: Transport urine to the bladder.
    • Bladder: Stores urine; urethra provides exit.
Kidney Function
  • Nephrons: The functional units of the kidneys, filter blood to form urine through filtration and reabsorption.
  • Loop of Henle: Conserves water, reducing urine volume.
The Endocrine System
  • Function: Regulates bodily functions through hormones that act on target cells over longer periods than the nervous system.
  • Glands:
    • Pituitary: Master gland controlling others.
    • Thyroid: Metabolic rate regulation.
    • Adrenals: Stress response hormones.
    • Pancreas: Regulates blood sugar.
Hormone Action
  • Steroid Hormones: Pass through the cell membrane and affect gene expression directly.
  • Nonsteroid Hormones: Bind to cell surface receptors and activate secondary messengers within the cell.
Feedback Mechanisms
  • Negative Feedback: Activity is decreased in response to the accumulation of a product (e.g., thermostat).
Reproductive System
  • Male System:
    • Scrotum regulates temperature for testes; hormone FSH and testosterone facilitate sperm production.
  • Female System:
    • Ovaries contain follicles that produce eggs; hormones regulate the menstrual cycle and pregnancy changes.
The Immune System
  • Defenses: Nonspecific (skin, inflammatory response) and specific (B cells, T cells).
    • Antigens: Trigger immune responses leading to antibody production.
    • Acquired Immunity: Active (natural exposure, vaccination) and passive (transfer of antibodies from mother to child).
Nervous System
  • Neurons: Carry electrical impulses.
    • Types: Sensory, motor, interneurons.
    • Parts include cell body, dendrites, axon, and myelin sheath.
Nerve Impulses
  • Resting State: Neuron is negatively charged; stimuli lead to ion movement across the membrane - action potential.
  • Synapse: Communication between neurons via neurotransmitters.
Central Nervous System (CNS)
  • Structure: Comprises the brain and spinal cord.
  • Functions: Processes information and coordinates responses.
Brain Structure
  • Includes cerebrum, cerebellum, brain stem, thalamus, and hypothalamus.
  • Spinal Cord: Handles reflexes and relays messages.
Peripheral Nervous System (PNS)
  • Function: Connects the CNS to limbs and organs, managing involuntary and voluntary responses.