Anatomy & Physiology

1. Anatomy & Physiology Unit 7: The Urogenital System

2. Function of the Urinary System • Dispose of excess wastes and ions • Regulate blood volume • Balance water and electrolytes • Regulates acid-base balance

3. Urinary System • Organs: • Kidneys: • 2- each lie against dorsal wall, retroperitoneally • Size of a bar of soap • Extend from T12 to L3, right lower than left • Ureters (2): tubes running from kidneys to bladder • Bladder: located in pelvis—retroperitoneally • Urethra: tube running from bladder to outside

4. Kidney Anatomy • Each kidney is enclosed in a renal capsule and fatty capsule • Inside divided into 3 regions: • Renal cortex: outer region • Renal medulla: dark-red inside layer • Medullary pyramids: triangular regions—apex of each point toward hilus • Separated by renal columns

5. Kidney Anatomy • Renal pelvis: flat, basin-like cavity • Continuous with ureters leaving hilus • Calyces: cup-shaped areas that enclose apex of pyramids • Act to collect urine from pyramids and pass onto the pelvis to be sent out ureters to bladder

7. Kidney Anatomy • Blood Supply: ~ ¼ of total blood supply passes through kidneys each minute • All vessels exit and enter kidney within the hilus • Renal artery: feeds blood into kidneys • Branch into arterioles & capillaries inside kidney • Renal vein: filtered blood draining from kidneys

8. Kidney Anatomy • Blood Flow Through Nephron • Enters afferent arteriole---units with glomerulus—exits efferent arteriole • Efferent arteriole smaller in diameter than afferent—so blood “backs up” • Blood flow slows down—raises blood pressure • Moves onto peritubular capillaries • Porous, low blood prssure, permits lots of movement across walls

9. Kidney Anatomy • Nephrons: structural and functional units of kidney • ~1 million per kidney • Actually form urine • 2 main structures: • Glomerulus (Bowman’s Capsule): knot of capillaries • Renal tubule: starts at glomerulus then continues as a 3 cm. tubule

10. Kidney Anatomy • Renal Tubule continued: 4 parts • Proximal convoluted tubule • Loop of Henle • Distal convoluted tubule • Collecting duct

11. Students-Teaching-StudentsUrine Production • Urine is produced within the nephrons of the kidneys in 3 main steps With your table buddy read pages 505-510 in your text and take notes on urine production. (15 minutes) • List the 3 steps of urine formation. • Explain what is moving out and in and where in the nephron does this taking place • Where does urine go (the pathway) once it’s produced? • Write this down in your notebook. (5 minutes)

12. Kidney Physiology: Urine Formation • Occurs in 3 steps: filtration, reabsorption and secretion 1.Filtration: nonselective, passive process • Filtrate = blood plasma without proteins & blood cells (too big) • Occurs within glomerulus • Blood filtered from afferent arterioles due to high blood pressure within tubule • Blood from glomerulus drained into efferent arterioles which feed the peritubular capillaries— low in blood pressure—great for absorption

13. Kidney Physiology: Urine Formation 2.Re-absorption: begins as filtrate enters proximal convoluted tubule—into peritubular capillaries • Too many “good” things filtered out of blood and need to return—glucose, amino acids, water • Water filtered passively (osmosis) • Solid particles transported actively via carriers • Nitrogenous wastes poorly reabsorbed (no carriers)

14. Kidney Physiology: Urine Formation 3.Secretion: re-absorption in reverse • Last chance to dump out drugs, hydrogen & potassium ions & creatinine • Occurs in proximal & distal convoluted tubule • Anything entering collecting duct from distal convoluted tubule sent through pyramids to calyces and renal pelvis—out to ureters—this is urine

15. Urine • Clear to pale to deep yellow • Urochrome: pigment made from destroyed hemoglobin • Sterile, slightly aromatic, slightly acidic • Composed of: sodium & potassium ions, urea, uric acid,creatinine, ammonia, bicarbonate ions • Should not have: glucose, proteins, RBC’s, hemoglobin, WBC’s and bile • Composition can change based on metabolism and disease

16. Urinalysis Assignment • There are several substances that should not be found in urine-so medical professionals use urinalysis as a tool to diagnose injury and illness • Using your book, look up the name of the condition and its potential causes if the following are found in urine: a. Glucose d. Bile pigment b. Proteins e. Hemoglobin c. Pus (WBCs & bacteria) f. RBCs

17. Urinalysis • Glucose---glycosuria • Too much sugar or diabetes mellitus • Proteins: proteinuria • Physical exertion, pregnancy, hypertension • Pus: pyuria • Urinary tract infection (UTI) • RBCs: hematuria • Bleeding in urinary tract (trauma, stones, infection) • Hemoglobin: hemoglobinuria • Transfusion reaction, hemolytic anemia • Bile: bilirubinuria • Hepatitis

18. Ureters • Slender tubes, 25-30 cm long • Passageways to carry urine from kidneys to bladder • Lined with smooth muscle---peristalsis propels urine • Bladder mucosa blocks urine from back-flowing out of bladder into ureters

19. Bladder • Smooth, collapsable, muscular sac • Temporarily stores urine • 3 openings: 2 for ureters, 1 for urethra • Can hold 1 pint and up to 2 pints • Lined by transitional epithelium—allows bladder to stretch • Not like the stomach, more like a balloon

20. Urethra • Thin-walled tube with smooth muscles—for peristalsis • 2 sphincters • Internal: involuntary • External: voluntary

21. Micturition • aka voiding: the emptying of the bladder • Controlled by the sphincters • Once 200 ml collects in bladder, stretch receptors are activated—stimulates muscular walls to contract—forces urine passed internal sphincter—FEELS LIKE YOU HAVE TO VOID • External sphincter can hold urine if needed • The feeling of needing to go will pass until about 300 ml collects—reflex starts again

22. Fluid, Electrolyte & Acid-Base Balance • Water & Electrolyte Balance • Water accounts for 50% of body weight in females/60% in males • Fluid Compartments • Intracellular Fluid (ICF): 2/3 of total body fluid—contained within living cells • Extracellular Fluid (ECF): 1/3 of total body fluid—located outside cells • Examples: blood plasma, interstitial fluid, CSF

23. Fluid, Electrolyte & Acid-Base Balance • Water & Electrolyte Balance • Remember this: WATER FOLLOWS SALT! • Small changes in electrolyte balance forces water to move b/n compartments • Alters blood volume and pressure and impairs nerve and muscle cells

24. Fluid, Electrolyte & Acid-Base Balance • Water & Electrolyte Balance • Water is gained through food and drink • Water is lost through sweat, breathing and predominately urine • Electrolytes enter through food and “hard” water • Electrolytes leave through sweat, feces and predominately urine

25. Fluid, Electrolyte & Acid-Base Balance • Hormonal Control • Antidiuretic hormone (ADH) • Osmoreceptors in hypothalamus signal release of ADH • This prevents urine loss • Aldosterone • If blood too dilute, water leaves blood stream • Kidneys retain sodium, rids potassium

26. Fluid, Electrolyte & Acid-Base Balance • Maintaining Acid-Base Balance • 3 methods: • Buffers: a chemical that resists changes in pH Weak Acids: release H+ in presence of strong base Weak Bases: combine with excess H+ in presence of strong acid

27. Fluid, Electrolyte & Acid-Base Balance • Maintaining Acid-Base Balance • 3 methods: • Respiratory System CO2 high—too acidic: increase in rate & depth of breathing CO2 low—too basic: decrease in rate & depth of breathing

28. Fluid, Electrolyte & Acid-Base Balance • Maintaining Acid-Base Balance • 3 methods: • Kidneys If blood is acidic: H+ are secreted & bicarbonate ions reabsorbed If blood too basic: rate of H+ secretion decreases, bicarbonate ions secreted

29. Urinary Mishaps • Incontinence: unable to voluntarily control external sphincter • Renal Caliculi: kidney stones • Urine too concentrated—uric acid salts • Urinary Tract Infection: bacterial infection of urethra—can lead to kidney infection • More common in women