BIOL 252 1st Edition Lecture 23 Outline of Last Lecture I Steps in Urine Formation II Renal Corpuscle III Regulation of Glomerular Filtration IV Proximal Convoluted Tubule Tubular reabsorption Outline of Current Lecture I PCT Tubular Reabsorption II Tubular Secretion III Loop of Henle IV Distal Convoluted Tubule and Collecting Duct V What about the loop VI Urine Storage and Elimination VII Digestive System VIII Saliva and Salivary Glands IX Layers of Digestive Tract X Peristalsis XI Stomach Current Lecture I II PCT Tubular Reabsorption a Why do peritubular capillaries absorb substances from ISF i High ISF hydrostatic pressure 1 Pushing inward because water and solutes accumulating in ISF ii Low blood hydrostatic pressure 8 mmHg 1 Volume of blood is much smaller than that going into glomerulus pressure drops 2 Because filtration removed fluid from blood iii High osmotic pressure high blood protein levels 1 Because filtration concentrated blood proteins Tubular Secretion a Waste removal urea uric acid bile acids ammonia catecholamines some drugs b Acid base balance H and HCO3i If pH is too low too acidic blood can get rid of H to fix the problem ii Reason urine is more acidic than blood These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute III IV V Loop of Henle a Kidney has an osmolarity gradient b Descending limb reabsorbs water volume of filtrate 35 c Ascending limb reabsorbs NaCl volume of filtrate 20 d Generates salinity gradient enabling collecting duct to concentrate urine Distal Convoluted Tubule and Collecting Duct a Site of hormonally controlled reabsorption and secretion b ADH stimulated by high blood osmolarity detected by hypothalamus i Tells us need to conserve water c If we leave water alone we can have 20 leave the body as urine i With ADH put channels aquaporins for water to go back to blood ii Why does water leave through aquaporins 1 Because of the increasing osmolarity gradient d When sodium levels too low i Aldosterone promotes Na reabsorption and K secretion ii We reabsorb more sodium e High blood volume i ANP atrial natriuretic peptide dilates afferent arteriole constricts efferent arteriole inhibits ADH renin and aldosterone secretion ii If atrium exposed to high venous pressure heart will release ANP iii Increases GFR iv Aldosterone if reabsorb salt water follows must decrease v Must also decrease water retention w ADH vi More of what s filtered leaves as urine f Low blood calcium i PTH promotes Ca2 reabsorption and PO4 secretion promotes calcitriol synthesis by PCT What about the loop a Loop of Henle comprises a countercurrent multiplier i Because fluids are flowing in opposite direction ii Multiplier part multiplying effect on salt concentration due to actions of two sides iii As water is reabsorbed solute concentration in filtrate increases iv If ascending was same as descending would absorb water 1 But made impermeable to water 2 So pump more and more salt out Na Cl 3 Pump less out at the top less to pump out 4 In ISF more salt at the bottom increased osmolarity 5 So lose water and then salt v How do we keep it extra salty at the bottom 1 At bottom of collecting duct allow small amount of urea to escape 2 Goes to tip of Loop of Henle VI VII VIII IX 3 Benefit extra solutes added to medulla to maintain salty environment a Important for water reabsorption 4 Recycling of urea lower end of CD permeable to urea urea contributes to osmolarity of deep medullary tissue Urine Storage and Elimination a Whatever comes out of collecting ducts bladder b Micturition reflex involuntary i Stretch receptors detect filling of bladder ii Signals return to bladder via parasympathetic fibers iii Signals excite muscular contraction iv Signals relax internal urethral sphincter v Voluntary control vi Micturition center in pons receives signals from stretch receptors vii Pons enhances signals 3 and 4 OR viii Pons signals to keep external urethral sphincter contracted urine retained in bladder ix When it is time to urinate signals from pons cease and external urethral sphincter relaxes urine is voided Digestive System a Ingestion intake of food b Digestion mechanical and chemical breakdown of food c Absorption uptake of molecules through the epithelial cells of digestive tract and then into blood or lymph d Compaction absorbing water and consolidating indigestibles into feces e Defecation elimination of feces f Excretion removing a waste from inside to outside Saliva and Salivary Glands a First mechanical and chemical digestion b 3 pairs of extrinsic salivary glands not in oral cavity but secrete to oral cavity i Connected to oral cavity by ducts c Parotid sublingual submandibular d Saliva components i Mucous helps you swallow food and liquefy food made of water and glycoproteins ii Bicarbonate ions controls pH keeps oral cavity from getting to acidic iii Amylase breaks up carbohydrates iv Lipase breaks down fats v Lysozyme lyses bacteria attacks the cell of bacterium Layers of Digestive Tract a As propel food downward goes through a tube w basic pattern b OUTER membrane visceral peritoneum serosa X XI c Muscularis externa important for muscular contractions organized into circular layer on inside contraction of these cells contracts tube longitudinal cells contracted shortens the tube d Submucosa capillaries lacteals lymph vessels e Mucosa epithelial layer barrier to the body Peristalsis a Muscular waves of contraction that propel substances through lumen Stomach a Functions storage mechanical digestion liquefies bolus producing chime chemical digestion of protein and fat b Delimited by pyloric sphincter and lower esophageal sphincter c Tissues i Mucosa Submucosa Muscularis externa serosa ii Mucosa gastric glands 1 Parietal cells secrete HCl secrete intrinsic factor needed for B12 absorption otherwise have pernicious anemia a Why HCl i Activates enzymes pepsinogen becomes pepsin once activated do not want active form in your cells because it breaks down proteins ii Denatures proteins iii Converts Fe3 to Fe2 form we can absorb iv Destroys many pathogens 2 Mucous cells secrete mucous 3 Enteroendocrine cells secrete paracrine factors and hormone gastrin G cells a Gastrin made by G cells target is the stomach b Affects other stomach cells and neighboring cells enhances activity of secretion 4 Chief cells secrete pepsinogen and lipase 5 Regenerative cells stem cells to replace all