BIO 251 1st Edition Lecture 20 Outline of Last Lecture I. Review of respiration a. External b. internalII. Gas exchangea. Physical principles b. Oxygenc. Carbon dioxideIII. Gas transporta. Oxygenb. Carbon dioxideIV. Local control of respirationV. Control of respirationa. Decreased arterial PO2 in regulating ventilation b. Increased arterial “ “c. Increased H+Outline of Current Lecture I. Overview a. Function 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.b. Components c. Kidney structure d. Nephron structure e. 3 basic renal processes f. Important notesII. Glomerular filtration a. Process of filtration b. Problem of GFR & BPc. Intrinsic regulation d. Extrinsic regulation Current Lecture-OverviewoFunction of Urinary System -Maintaining -Water balance in body-Plasma volume -Acid-base balance -Proper osmolarity of body fluids-Regulating quantity & concentration of most ECF ions -Excreting -End products of bodily metabolism (urea, uric acid)-Foreign compounds (drugs, pesticides, food additives)-Secreting -Erythropoietin (hormone that stimulates RBC production)-Renin (hormone involved in salt regulation)-Converting vitamin D to its active form oMajor components of urinary system (Fig 18.1 &18.2)-Kidneys -2 bean shaped kidneys that lie in back of abdominal cavity -Produce urine from blood plasma -Renal artery -Renal vein -Renal pelvis -Urine collecting cavity in inner core of each kidney -Ureter-Carries urine from each renal pelvis to bladder -Urinary bladder -Temp urine storage area-Urethra -Tube from bladder to environ for elimination or urine oKidney structure (18.2)-Each composed of ~1 million microscopic functional units called nephrons -Arrangement of nephrons give rise to 2 regions -Outer regions: renal cortex -Inner region: renal Medulla oNephron structure: broken into 2 major parts (18.6)-Vascular component -Renal artery enters kidneys then subdivides -Into afferents arterials, 1 of which supplies each nephron, & subdivide -Into glomerular capillaries. The glomerulus of each nephron is ball like tuft of theses capillaries, & is where filtration occurs. The glomerular capillaries join together to form -Efferent arteriole, which leaves the glomerulus. This arteriole carries blood that was not filtered in the glomerulus, and which has not yet exchanged materials with the surrounding tissue. This is the only place in the body where an arteriole leaves capillaries. The efferent arteriole quicklysubdivides into-peritubular capillaries, which supply the renal tissue with blood, and are important in exchanges between the tubular system and the blood during urine production. They completely surround the tubular components.-Tubular component (18.3)-Hollow fluid filled tube formed by a single layer of epithelial cells. Even though it is continuous, it is arbitrarily divided into different segments based on differences in structure and function along its length.-Bowman’s capsule begins the tubular component, and is a doubled wall cup that surrounds the glomerulus and collects the fluid filtered from the glomerular capillaries. From there, filtered fluid passes into -Proximal tubule, which is highly coiled and lies entirely within the cortex-Loop of Henle, which forms a U-shaped loop that dips into the renal medulla. The descending limb goes from the cortex into the medulla; the ascending limb goes back up into the cortex from the medulla, and returns to the glomerular region of its own nephron-The juxtaglomerular apparatus lies next to the glomerulus, is composed of both tubular and vascular components, and is involved in regulating kidney function-the distal tubule, which is highly coiled and lies entirely within the cortex. This empties into a-collecting duct, each of which collects fluid from up to 8 nephrons.oThe Three Basic Renal Processes (18.7) -Glomerular filtration-blood flows through the glomerulus-about 20 % of plasma that enters is filtered into Bowman’s capsule, and enters the tubular system-all blood components (except proteins and red blood cells) are non-selectively filtered along with plasma at this step into the tubular system-on average, ~ 180 liters (47.5 gallons) of glomerular filtrate formed per-Tubular reabsorption-As filtrate flows through tubules, substances of value to the body are returned to the peritubular capillaries and so re-enter the circulatory system-Of the 180 liters of filtrate produced per day, about 178.5 liters are reabsorbed in this process; the other 1.5 liters ultimately eliminated as urine-Tubular secretion-Selective transfer of substances from peritubular capillary into the tubular system-the 80% of the blood that is NOT filtered into Bowman’s capsule thus can have selected components removed by this process; in general, this is a rapid way to remove specific substances from the blood. oImportant Notes: -Don’t forget that there is free exchange between the plasma and the interstitial fluid in the capillaries and lymph in the whole body, so ALL the ECF is filtered through the kidneys. Thus by performing their regulatory and excretory roles on the plasma, the kidneys maintain the proper interstitial fluid environmentfor optimal cell function-At rest, 20% to 25% of the blood volume is pumped to the kidneys, i.e., nearly a quarter of your blood is going to get “cleansed” at any given moment-The rest of Topic 20 and Topic 21 will primarily discuss in detail the 3 basic renal processes; Topic 22 and 23 cover fluid and acid base balance, in which the kidneys play a major role-Glomerular FiltrationoProcess of filtration -Glomerular membrane allows nonspecific passage of plasma and plasmaions from vascular system into tubular system; note that the glomerular capillary walls (which are part of the glomerular membrane) are 100 times more permeable to water and small salutes than normal capillary walls -Glomerular membrane excludes > 99% of all proteins in blood from tubular system-Glomerular Filtration Rate (GFR) is the rate at which plasma is filtered into tubular system from vascular system a) filtration rate is determined by -surface area of glomerular membrane-permeability of glomerular membrane -glomerular capillary blood pressure -hydrostatic pressure (can not be regulated) -plasma osmotic pressure (can not be regulated) -GFR is about 125 ml/min for males for both kidneys -GFR is about 115 ml/min for females