16.1 Intro to the Excretory System

Systems The excretory system includes: Respiratory system (already studied) Circulatory system (already studies) Urinary system (focus of this unit) Integumentary (skin) system (brief intro in this unit)

Main Functions of Urinary System To maintain homeostasis by: Removing metabolic waste products, notably nitrogenous waste from breakdown of amino acids: Urea Creatine Uric acid Maintaining water-salt balance Kidneys perform this function Blood volume and blood pressure are closely connected More salts = more blood volume = higher blood pressure

Main Functions of Urinary System Maintaining acid-base balance Kidneys perform this function Monitor and maintain blood pH at 7.4 Excrete H+ ions and reabsorb HCO3- ions as needed Secretion of hormones Kidneys excrete renin (hormone) that stimulates the excretion of aldersterone. Aldersterone promotes the reabsorption of Na+ ions in the kidneys Kidneys secrete eruthropoietin, which stimulates red blood cell production

Organs of Urinary System A. Kidney 1. Bean-shaped 2. Located between peritoneum and the back muscles 3. Renal pelvis – funnel-shaped structure at the beginning of the ureter 4. Medulla a, Inner, striated layer b. Striated cones are renal pyramids c. Base of pyramids empty into cuplike cavities called calyces 5. Cortex – composed of millions of microscopic nephrons

Organs of Urinary System B. Nephron – functional unit of kidney 1. Bowman’s capsule 2. Glomerulus 3. Proximal convoluted tubule 4. Loop of Henle 5. Distal convoluted tubule 6. Collecting tubule C. Ureters 1. One from each kidney 2. Smooth muscle tube with mucous membrane lining

Organs of Urinary System D. Urinary bladder 1. Hollow, muscular organ 2. Made of elastic fibers and involuntary muscle 3. Stores urine – about 500 cc E. Urethra 1. Connects bladder with urinary meatus 2. Urinary meatus is opening to body