Have a short loop of henle and are more numerous

This preview shows page 11 - 14 out of 43 pages.

have a short Loop of Henle and are more numerous-Juxtamedullary nephronshave a much longer Loop of Henle that extends deep into the medulla11
-Descending limb of Loop of Henle-Impermeable to solutes-Permeable to water-Osmolarity thus increases as we descend the Loop of Henle, all the way up to about 1200 mOsm/liter at the actual loop, since water is being reabsorbed (obligatory reabsorption!) due to the salty interstitial fluid-Why is the interstitial fluid so salty? -I’m glad you asked...-Ascending limb of Loop of Henle-The salty guy-In its thickest part there are symporters which actively pump Na+-K+-2Cl- into the surrounding interstitial fluid – so, this is where the solutes are reabsorbed-Why? -Well, the ascending limb is essentially impermeable to water, so osmolarity within the tubule goes all the way down to about 150 mOsm/Liter by the time we reach the distal convoluted tubule-Still why?-Well, this is what we call a COUNTERCURRENT MULTIPLIER;we’re using this mechanism to concentrate the urine without spending excess energy. By using energy only in the thick, ascending limb to pump out Na+-K+-2Cl-, we establish an osmotic gradient between the two limbs that naturally pulls water out of the tubules in the water-permeable descending limb. -What really eventually decides whether the urine is concentrated or dilute is the presence of ADH, which exerts its effects predominantly on our celebrity guest star, the collecting duct. As you know, ADH promotes facultative water reabsorption, which makes the urine more and more concentrated because water is leaving but solutes are remaining. -The Early Distal Convoluted Tubule -Reabsorbs about 10-15% of filtered water, and 5% of filtered Na+ & Cl--Sensitive to parathyroid hormone, which promotes reabsorption of Ca2+-Late Distal Convoluted Tubule (Sensitive to hormonal regulation)-Solute and water reabsorption depend on body’s needs, moderated by aldosterone and ADH-Major site of K+ secretion -Principalcells reabsorb water when ADH presence is high-Intercalatedcells reabsorb K+ and HCO3- and secrete H+-Guest Starring: The Collecting Duct, Who is Not Actually a Part of The Nephron-ADH(facultative reabsorption; decreasesinterstitial fluid osmolarity, increases blood volume and pressure) -Aldosterone(obligatory reabsorption; increasesinterstitial fluid osmolarity, blood volume and pressure)12
Micturition-To urinateDetrusor Muscle-Smooth muscle in the wall of the urinary bladder, which involuntarily contracts when distendedInternal urethral sphincter-Relaxes during micturition reflex External urethral sphincter-Inhibited during the micturition reflex so you don’t pee on yourselfUrinary bladder-Stores your urineUreter-Transports urine from kidneys to urinary bladderUrethra-Passageway for discharging urine out of the bodyAging and the kidneys -Less blood flow to kidneys during older age leads to reduced size and functionality of kidneys.

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture