Human Body Systems Part 2

Digestive System We must eat food for ENERGY! Need water, carbs (sugars), fats (lipids), proteins, vitamins and minerals Digestion breaks foods into smaller molecules the body can use and nutrients that can be absorbed Provides energy and nutrients necessary for the function of other systems

Digestion Begins in the mouth Chewing and the enzyme amylase in saliva starts the break down Passes through the esophagus to the stomach Churning and more enzymes continue break down Passes into intestines  small and then large Contains more digestive enzymes Where many nutrients are absorbed and water is removed Also contain many colonies of bacteria to aid in digestion Undigested material is excreted out (poop!)

Excretory System Rids the body of metabolic wastes like extra salts, carbon dioxide, and urea (in urine) Main excretion organ  the kidneys Remove wastes from blood Maintain blood pH Regulate water content in blood Also involves skin, lungs, liver, and bladder

Kidneys Consist of functional units called nephrons Nephrons purify blood through filtration and reabsorption Purified blood is returned to circulation and urine is collected in the bladder

Endocrine System Consists of glands that secrete hormones or other substances Hormones are chemicals that are released in one part, but have an effect in another part of the body Target cells have receptors for specific hormones

Exocrine glands release secretions into ducts direct to organs Endocrine glands release hormones into the blood stream Many glands secrete hormones that control other glands

Endocrine and other systems Hormones play a major role in maintaining homeostasis and other important functions Maintaining water balance Controlling metabolism Controlling blood concentration Handling stress Maintaining blood sugar levels Reproduction and development Growth

Reproductive System Male – produce sperm Female – produce ova (eggs) Ovulation – release of an egg Development Zygote (fertilized egg)  implantation  gastrulation (results in three cell layers)  neurulation (development of the nervous system)

Immune System Fight infection by producing cells that inactivate foreign pathogens or cells Called immunity Remember a pathogen is anything that causes disease Bacteria, viruses, protists, parasites, fungi

Nonspecific Defenses Treat all pathogens the same First line: Skin, mucus, sweat, and tears Second line: If bacteria enter… Inflammatory response – blood vessels expand; phagocytes (WBCs) engulf pathogens; temp. increases If viruses enter… Interferons (proteins) are released to help other cells resist viruses

Specific Defenses Called immune response Humoral immunity – antibodies are produced by B cells in response to specific antigen Produce memory B cells for next infection Cell-mediated immunity – T cells differentiate into killer T cells that destroy the pathogen with a certain antigen Also produces memory T cells

Vaccinations The injection of a weakened form of a pathogen Triggers an immune response which builds immunity to that pathogen Will stop infection or weaken the symptoms