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Kidney anatomy Urinary system Renal Aids homeostasis by cortex removing cellular wastes and Renal medulla foreign compounds, and Cortex maintains salt and water Renal balance of plasma pelvis Medulla Ureter Nephrons Let’s make the filtrate... Each kidney has about one million nephrons Blood is filtered at the glomerulus. Water Afferent arteriole brings and solutes leave the blood to glomerulus and blood and enter then forms efferent Bowman’s capsule. arteriole. Efferent arteriole branches to peritubular capillaries 1 Glomerulus physiology Bowman’s capsule contains podocytes that encircle Glomerular filtration the glomerulus. Glomerular filtration Normally blood cells and plasma proteins are not is similar to Capillary filtered ultrafiltration of 55 blood pressure capillaries Osmotic Hydrostatic 20% of plasma pressure 30 15 pressure becomes filtrate Glomerular filtration rate (GFR) determined by: Net filtration pressure and glomerulus permeability Adjusting GFR Filtrate is adjusted along the nephron Distal Blood pressure tubule Proximal tubule Cortex region Bowman’s capsule Radius of afferent arteriole Juxtaglomerular apparatus - helps in Decreasing GFR helps retain adjustments to filtration rate fluid and salts Loop of Henle Medulla region 2 Tubular reabsorption and secretion 180 liters per day are filtered, most is reabsorbed Reabsorption: filtered substances leave the nephron and enter peritubular capillaries Secretion: some substances from the peritubular capillaries enter the nephron So what is urine, then? Everything in the nephron that does not get Reabsorption physiology reabsorbed into the blood leaves as ….urine!!! 3 + Reabsorption of Na + (the key to it all…) Na reabsorption Na+ reabsorption (RA) drives the movement of many other substances in the tubule Water will “follow” Na+ movement Lumen Proximal tubular cell Control of sodium RA Page 533 When ECF volume is low, need to Na+ RA Osmosis Interstitial fluid Peritubular + Water capillary Na RA at distal and collection tubules with channel aldosterone. More Na+K+ pumps and Na+ Hydrostatic channels are made Osmosis pressure Renin is the trigger for eventual release of aldosterone, along a chain of events (renin- angiotensin-aldosterone system or RAAS) 4 Jux.App. monitors NaCl and ECF levels Efferent arteriole Distal tubule Bowman’s capsule Bowman’s capsule Juxtaglomerular Glomerular apparatus capillaries Podocyte Distal Glomerular capillaries tubule Granular cells Juxtaglomerular apparatus Afferent arteriole Glucose and amino acid reabsorption Hypertension can be due to increased renin leading to more plasma and thus high blood pressure Glucose and AA’s are cotransported w/Na+ via carriers Actively RA substances have a “tubular maximum” (when all carriers are used) 5 Na+ movement allows passive RA of substances. Our old friend, cotransport 80% of water reabsorption occurs before distal tub. by following Na+ Glucose, amino acids are reabsorbed via cotransporters If plasma levels get too high, renal threshold is reached (AAs or glucose leave in urine) Tubular secretion H+ and K+, and organic anions are secreted to Adjusting the concentration of urine tubule Our body tissues and filtrate are 300 mosm (osmolarity) K+ secretion is driven by the Na+K+ pump We can make urine as dilute as 100 or concentrated as 1200 mosm Na+ gradient in renal medulla allows for control of urine osmolarity for water balance 6 Loop of Henle functions to set up high osmolarity along the collecting tubule (duct) Collecting tubule (duct) Changing the permeability to H20 along the Distal collecting duct controls H O RA tubule 2 Cortex Vasopressin hormone controls permeability Medulla at distal and collecting tubules Collecting Long loop Tubule or Duct of Henle Collecting duct permeability Needing water Filtrate has concentration determines final amount of H2O RA of 100 mosm/liter 65 % of H20 RA is obligatory in the proximal tubule, 15% at Loop of Henle. Cortex Medulla 20% determined by vasopressin Collecting tubule Concentration of urine may be up to 1,200 = passive diffusion of = portions of tubule impermeable to H O H2O 2 = active transport of NaCl * = permeability to H2O increased by vasopressin 7 Too much water Why increased urination Filtrate has concentration of 100 mosm/liter from alcohol? Alcohol inhibits vasopressin Cortex Medulla It can also temporarily reduce blood glucose (via liver effects) Collecting tubule Concentration of urine may be as low as 100 = passive diffusion of = portions of tubule impermeable to H O H2O 2 = active transport of NaCl * = permeability to H2O increased by vasopressin Medical problems Kidney stones – caused when hard deposits form in the kidney (usually calcium, sometimes uric acid). They can enter the ureter and cause extreme pain. End of exam 4 material Urinary tract infection – 2nd most common type of infection. Bacteria introduced to urethra multiply and travel to bladder (cystitis) or further. 8 What goes on during Things I’m assuming you know: digestion… Know layers found throughout alimentary Motility - propulsion and mixing canal (mucosa, submucosa, muscular Secretion of digestive enzymes, bile, layers) and the term lumen mucus, water Chemical digestion Accessory structures (pancreas, liver, salivary glands, other exocrine glands) are Absorption a part of the digestive system Signaling Intrinsic nerve plexus Down the chute…oral cavity Network of nerve fibers that controls digestive activity in gut. “Your 2nd brain” Physical digestion Mastication - mixes food with saliva Saliva - amylase - digests starch mucus Tooth decay from lysozyme bacterial activity on food debris 9 Making saliva... Pressure and gustation promotes autonomic impulses to salivary glands PNS and SNS signals both influence salivary glands Bolus touches receptors in the pharynx to stimulate swallowing Peristaltic contractions push food Into the ....stomach through the esophagus. Storage, physical and chemical digestion Distention will cause a second wave and saliva release HCl Mixing in the antrum Bolus Chyme 10 Gastric emptying Pyloric sphincter Duodenum Peristaltic Peristaltic Movement contraction contraction of chyme Mucosa Stomach mucosa of stomach Gastric juices! Gastric Mucosa pH as low as 2 pits Gastric pit Mucosa cells Gastric glands Chief cells (Pepsinogen) Submucosa Parietal cells (HCl) 11 autocatalysis Digestion Pepsinogen Pepsin Controlling gastric juices.. Cephalic (“head”) phase - stimuli from the Protein head stimulate chief and parietal cells via HCI Peptide fragments intrinsic plexus, gastrin released Controlling gastric juices.. Protecting the stomach from itself… Stomach lining is protected from Gastric phase – proteins, distension at stomach gastric secretions by mucus. H+ cannot also stimulate gastric secretions via intrinsic enter cells plexus Cells are continually replaced Low protein, low pH is inhibitory, decreasing flow of gastric juices 12 Stomach lining problems Leaving the stomach… Peptic ulcer - stomach wall injured by acid Emptying controlled by duodenum and and enzymes stomach Chyme volume promotes emptying Injured tissue releases histamine, which stimulates acid production (…not good) Acid and fats in duodenum prevent gastric emptying Leaving the stomach... Pancreas Gastroesophageal sphincter Stomach Pyloric sphincter Islets of Langerhans Duodenum Duodenum Movement Peristaltic Cells contraction of chyme secrete alkaline Cells secrete solution Gastric emptying digestive enzymes 13 Pancreas An endocrine and exocrine gland Enzymes: protease, amylase, lipase 14.
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