Chapter 23 Urinary System 11 14 2013 The Urinary System o Makes urine o Gets rid of waste products in our body so they are not harmful o Metabolic wastes substance produced by the body o Nitrogenous wastes nitrogen containing metabolic wastes Includes ammonia urea uric acid creatine Kidneys o Two located in the posterior portion of the abdominal cavity o Right kidney is slightly lower o Region called the hilum where nerves blood vessels lymphatics and a passageway called the ureter pass through o Surrounding kidney are three layers of connective tissue from superficial to deep fascia fat capsule and fibrous capsule o Fascia fused with parietal peritoneum and fascia of lumbar muscles o Perirenal fat capsule protects and cushions kidneys o Fibrous capsule wraps tightly around kidneys and adrenals o Outer portion called renal cortex and inner is called renal medulla o Urine is produced here o Medulla is divided into 6 10 cone shaped renal pyramids o Major and minor calyces collect urine as it is formed and funnels it into o Each kidney is supplied by the renal artery branching off the abdominal o Renal artery branches into interlobar arteries which penetrates the renal the renal pelvis aorta columns o Some arterioles form a coiled mass called the glomerulus o Afferent arteriole feeds into glomerulus larger wider high pressure o Capillary bed intertwined like pasta o Efferent arteriole leads away from the kidney smaller thinner o Oxygen rich Nephrons o Functional units of the kidneys o Site where filtrate from the blood is processed and turned into urine o Bowman s capsule glomerular capsule wraps around glomerulus to catch filtrate from the blood o Beginning portion of nephrons o Bowman s capsule glomerulus renal corpuscle o Podocytes cells that wrap around the glomerular capillaries to prevent large substances from filtering into Bowman s capsule o Cortical nephrons mainly in cortex may dip into medulla o Juxtamedullary nephrons dips very deep into medulla controls how concentrated dilute our urine is o PCT Proximal Convoluted Tubule what was filtered is reabsorbed into blood o Loop of Henle extends into medulla makes 180 turn hairpin turn and back to the cortex provides ability to regulate water and sodium content of filtrate contains thick and thin segments o Thick segment simple cuboidal active transport of transport salts high metabolic activity o Thin squamous o DCT empties into one large connecting duct Pathway of Filtrate o Afferent arteriole glomerulus Bowman s capsule PCT descending limb of loop of Henle hairpin turn ascending limb of loop of Henle DCT collecting duct papillary duct calyces renal pelvis ureter o four main processes glomerular filtration tubular reabsorption tubular urinary bladder urethra secretion water conversation Glomerular Filtration o filtration membrane consists of the capillary basement membrane and filtration slits o capillary endothelium is fenestrated allowing fluids ions and small solutes to pas out of the glomerulus and into Bowman s capsule o basement membrane is made up of negatively charged gel preventing most molecules from passing through based on size or if they are also negatively charged o the filtration slits are spaces between foot processes of the podocytes that wrap around the glomerulus also negatively charged o anything 3 nanometers or smaller can pass through o water electrolytes glucose amino acids fatty acids nitrogenous wastes vitamins o red blood cells are way too big to fit through o Fluid moves from glomerulus to Bowman s capsule o Blood pressure is around 60mmHg here high o Afferent arteriole is wider than efferent arteriole o High rate of filtration high hydrostatic pressure in Bowman s capsule 18mmHg opposing filtration o Blood has proteins which attract water towards them 32mmHg opposing filtration women o NFP 60mmHg out 18mmHg in 32mmHg in 10mmHg out o Glomerular filtration rate GFR 125mL min for men and 105mL min in o Per day males form 180L of filtration and women filter 150L o 99 of filtrate is reabsorbed so urine output is about 1 2L day o GFR too fast filtrate moves too quickly for fluids and solutes to be o GFR too slow filtrate moves slowly and wastes are reabsorbed instead of o Glomerular filtration rate changes and blood flow without involvement of nervous or endocrine systems especially as blood pressure changes properly reabsorbed excreted throughout day o Myogenic mechanism if BP rises afferent arteriole is stretched o Smooth muscle around the afferent arteriole constricts to maintain blood flow to the glomerulus o BP falls smooth muscle relaxes to allow blood to easily flow o Tubuloglomerular feedback glomerulus monitors the composition of the fluid within the tubule and adjust GFR accordingly o Juxtaglomerular apparatus o macula densa cells tell how much salt is in filtrate o based on salt we can tell if the GFR is too fast or slow o juxtaglomerular cells controls GFR o Mesangial cells help influence macula densa o If GFR is too fast there is too much salt in filtrate and concentration is high so macula densa cells detect this and they tell the JG cells to slow down to give time to reabsorb NaCl o If GFR is too slow too much NaCl is reabsorbed so macula densa cells detect the salt concentration is too low and they speed up the rate o The SNS can innervate renal blood vessels constricting the afferent arterioles o JG cells secrete renin in response to drop in BP o Renin hormone from JG cells o Liver makes angiotensinogen to release into blood o Angiotensin II is raised o In lungs enzyme called ACE angiotensin converting enzyme converts angiotensin I into angiotensin II o Adrenal cortex makes aldosterone to bind to the kidneys Tubular Reabsorption o Movement of water and solutes from nephron back into the blood o 65 of filtrate is reabsorbed at the PCT o Secondary active transport o Aquaporins channels specifically designed for water to be reabsorbed o Transport maximum Tm maximum amount able to be reabsorbed o Reached when transporter is saturated o Transport maximum does not typically happen o Glycosuria excess glucose in blood filtered into kidneys exceeds Tm so some glucose passes transporters before it can be reabsorbed into the blood o Extra glucose in the urine o Happens with uncontrolled diabetes o Tubular secretion removal of solutes that were too large to be filtered at the glomerulus o Substances are transported from blood vessels into nephron o Removes certain drugs like penicillin aspirin