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BIOL 141 notes 13

by: Camryn McCabe

BIOL 141 notes 13 Biol 141

Marketplace > Science > Biol 141 > BIOL 141 notes 13
Camryn McCabe
Penn State
GPA 3.81

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urinary system; notes from lecture 13; first notes for exam 4
Janelle Malcos
Class Notes
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This 4 page Class Notes was uploaded by Camryn McCabe on Saturday March 26, 2016. The Class Notes belongs to Biol 141 at a university taught by Janelle Malcos in Spring 2016. Since its upload, it has received 24 views.

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Date Created: 03/26/16
Lecture 13 notes Urinary System Kidneys: function to remove metabolic wastes from the blood  Alter pH by absorbing or secreting protons  Alter blood volume by absorbing or secreting water (plays a role in blood pressure)  Function occurs at the nephron (functional unit of the kidney) Nephron: cellular, tube-like structure  Intimately associated with capillary beds  Nephrons connect to ureters (muscular tubes)  Ureters connect to bladder (muscular sac to hold urine)  Bladder connects to urethra (tube to external environment)  ^^^ All of these structures are continues o Have a lumen (inside opening) o Lumen is considered part of the “external world”  Nephrons are continuous to the outside world Nephrons processes:  Filtration- initial movement of molecules from capillary into nephron  Reabsorption- movement of a molecules in nephron back into the capillary o Involves movement of molecules into the body (into tissues rather than lumen; lumen is considered outside world)  Secretion- movement of a molecule from the capillary into the nephron after filtration Kidneys remove…  Metabolic waste: by products from normal body function  Some of the most toxic nitrogenous wastes o Urea- protein, metabolism, produced in liver o Uric acid- DNA metabolism, produced in liver o Creatinine- protein metabolism, produced in muscles  All are found in urine and are removed by filtration and secretion Nephron structure  2 types (based on location in kidney) o Cortical (mainly in cortex) o Juxtamedullary (next to medulla)’ Lecture 13 notes Urinary System  Five regions o Glomerular (Bowman’s) capsule  Start with filtration  Glomerulus = capillary bed  Consists of 2 layers associated with glomerulus  Visceral cell layer- consists of podocytes that wrap cell extensions around the capillaries o Capillaries are fenestrated (perforated with pores)  Parietal cell layer o Proximal convoluted tubule (PCT)  Proximal  close to glomerulus  Secretion and reabsorption o Nephron loop (loop of Henle)  Secretion and reabsorption o Distal convoluted tubule (DCT)  Distal  far from glomerulus (when considering flow of urine)  Secretion and reabsorption o Collection duct  Secretion and reabsorptions Nephron Blood supply  Associated vessels o Afferent arteriole- blood flow to glomerulus o Glomerulus- capillary bed o Efferent arteriole- blood flow leaving glomerulus o Peritubular capillaries- associated with PCT and DCT o Vasa recta capillaries- loop of Henle, only in juxtamedullary nephrons Initial Filtration (step 1)  Filtration membrane- where initial filtration of blood occurs  Based on size of molecules  Filtration- initial movement of stuff into nephron  Filtration membrane consists of 2 cell layers o Endothelial cell of capillary (with fenestrations-protein that causes little holes to form) o Cell body and extensions of podocytes (visceral layer)  Filtration slits- small spaces between podocytes o 2 are connected by basement membrane  Filtration occurs at filtration slits Lecture 13 notes Urinary System o Anything small enough to fit between slits enters the nephron (like water, minerals, ions, glucose, wastes) o Cells and large proteins are trapped in capillaries (like blood, proteins) Reabsorption/secretion at PCT (step 2)  PCT- closely associated with peritubular capillaries bed o Function:  Passive and active transport  Reabsorption of water, ions, glucose, and amino acids, and some wastes into capillaries (good things)  Water is reabsorbed because of osmosis  Secretion of nitrogenous wastes and toxins (aspirin, morphine) “Salty” medulla in Nephron loop (step 3)  Nephron loop- major function is to use active transport to move Na+Cl- into kidney medulla o Descending limb- only permeable o water o Ascending limb- only permeable to ions (Na+Cl-) o Associated with vasa recta capillary bed  The only way our body can move water is by creating a concentration gradient (for osmosis), so we created a salty area, driving water into the kidney  Nephron loop uses active absorption of NaCl (ascending limb) to drive the absorption of water (descending limb and collecting duct)  Difference in solutes will cause water to move from descending limb to medulla Countercurrent Multiplier- function of nephron  Filtrate in descending and ascending loops ins moving in opposite directions- countercurrent  Filtrate in descending lib becomes MORE concentrated as it approaches the bend bc movement of water into medulla- multiplier  Salt is reabsorbed in ascending limb- creates gradients Reabsorption/secretion at DCT (step 4)  Distal convoluted tubule (DCT) o Reabsorption of water is influenced by hormones o Secretion of any extra wastes Lecture 13 notes Urinary System o Important site of proton absorption or secretion  Works with respiratory system to balance pH  Problem with DCT that prevents secretion/absorption of protons  metabolic acidosis (too many protons)/ metabolic alkalosis (too few protons) o Can occur in conjunction with respiratory alkalosis/acidosis Water Conservation in collecting duct (step 5)  Main function- absorb more water  Relies of solute gradient created by nephron loop o Osmosis drives water to be reabsorbed from duct  Influenced by hormones  Antidiuretic hormone (ADH) o Produced by pituitary gland in response to dehydration o Causes production of aquaporins in collecting duct o Allows for uptake of water faster o As rehydration occurs, production of aquaporins decreases o Alcohol blocks ADH production


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