Medullary osmotic gradient is produced by
Active sodium transport by thick ascending limb from lumen into interstitium
Low blood flow countercurrent mechanism
* (of vasa recta)
Recycling of urea
* Between medullary collecting ducts and deep portions of loop of
Henle
Cortex
Rich blood supply (peritubular capillaries)
--> Solutes reabsorbed from lumen do not accumulate in interstitium
Medulla
Lower blood supply
--> Solutes can accumulate in interstitium
Countercurrent exchange system of the vasa recta
--> Preservation of osmotic gradient
Active sodium transport causes the hyperosmolality
Recycling of urea
Diffusion (i.e. resorption) of urea out of lumen into interstitium contribute to medulla osmolality
Urea contribute about half of medullary osmolality
Sodium chloride contribute the other half
ADH
ADH increases water permeability in cortical AND medullary collecting duct
ADH also increases urea resorption by
Increasing urea concentration in lumen
Increasing permeability in the inner medullary collecting
duct
* By increasing urea uniporter
--> Allows recycling of urea
--> Increase medullary osmotic gradient
Inner medulla
Inner medullary collecting ducts has finite water permeability
When ADH is absent
--> Osmotic gradient in MCD (between lumen and interstitium) is large
--> Increased water reabsorption in MCD
* In contrast to cortical and outer medullary collecting ducts
Thus,
Interstitial osmolality in inner medulla is reduced by
Increased water reabsorption
Decreased urea reabsorption
--> Kidney's ability to concentrate urine is reduced
Explain how the renal medullary osmotic gradient is generated and maintained. Describe how this is important...
Section A – Answer only ONE question from this section 1. Explain the physiological concept of flow down gradients and illustrate your understanding by presenting three examples from at least two different body systems. In your answer include the terms gradient and resistance. 2. Explain the physiological concept of structure-function relationships (structure enables function) and illustrate your understanding by presenting three examples from at least two different body systems. Section B – Answer only ONE question from this section 3....
Human Physiology wiz needed 6. Most electrolyte reabsorption by the renal tubules: a. is Tm limited. b. occurs only in the distal convoluted tubule. c. is completed by the time the loop of Henley is reached d. is hormonally controlled in distal tubule segments. e. All of these are correct. 7. The mechanism by which the medullary osmotic gradient is established, depends most on the permeability properties of the a. proximal convoluted tubule. b. loop of Henle c. the distal...
QUESTION 18 Which structure passes urine to the renal pelvis? a. Proximal tubule b. Glomerulus c. Bowman's capsule d. Loop of Henle e. Collecting ducts QUESTION 19 Which of the following structures in the nephron contains transport epithelium that is impermeable to water? a. The proximal tubule b. The distal tubule c. The collecting duct d. The ascending loop of Henle Oe. The descending loop of Henle QUESTION 20 Processing of filtrate in the proximal and distal tubules accomplishes what...
Which structure passes urine to the renal pelvis? a. Proximal tubule b. Glomerulus c. Bowman's capsule d. Loop of Henle e. Collecting ducts QUESTION 19 Which of the following structures in the nephron contains transport epithelium that is impermeable to water? a. The proximal tubule b. The distal tubule c. The collecting duct d. The ascending loop of Henle e. The descending loop of Henle QUESTION 20 Processing of filtrate in the proximal and distal tubules accomplishes what important function?...
A concentration gradient affects the direction that solutes diffusion. Describe how molecules move with respect to the concentration. How does size affect the rate of diffusion? Does polarity affect the rate of diffusion? Explain your answer. If a piece of celery is placed in a glass of pure water, are the celery cells hypertonic, hypotonic or isotonic compared to the water? In which direction will water move? What is the water potential of pure water? Why don’t red blood cells...
1. Describe the hormonal control of Ca2+ homeostasis Key: Parathyroid calcitonin increase calcium PTH The thyroid gland also produces the hormone_________________which causes bones to store calcium ions (Ca+2). ________________________glands are 4 tiny glands located on the thyroid gland that secrete parathyroid hormone (_____) to control calcium metabolism by increasing the levels of _______________ions (Ca+2) in blood. Parathyroids ____________ levels of calcium ions by 1. release Ca++ from bone; 2. Promotion of reabsorption of Ca++ by kidneys; 3. Increase absorption of...
Pre-Lab Questions A concentration gradient affects the direction that solutes diffusion. Describe how molecules move with respect to the concentration. How does size affect the rate of diffusion? Does polarity affect the rate of diffusion? Explain your answer. If a piece of celery is placed in a glass of pure water, are the celery cells hypertonic, hypotonic or isotonic compared to the water? In which direction will water move? What is the water potential of pure water? Why don’t red...
Explain how the sympathetic nervous system acts to directly regulate stroke volume. Include a detailed description of the mechanism (include the target cells, the proteins, signaling molecules, ions, and changes in membrane potential where appropriate). What effect does this have on cardiac output. This will take about half a page to describe. Discuss venous return. Be sure: to define venous return and explain the importance of venous return to cardiac output. What determines venous return? Discuss each way that venous...
Discuss the functional fluid compartments of the body including the methods in which water moves between plasma and interstitial fluid. Discuss the role of hydrostatic pressure, osmotic pressure, and oncotic pressure. Differentiate between osmolality and osmolarity. Explain Starling's Law of Capillary Forces. Differentiate between intracellular fluids and extracellular fluids. Discuss causes of volume imbalances. Describe the assessment, expected findings, laboratory tests, patient-centered care, and complications of fluid volume deficits. Describe the assessment, expected findings, laboratory tests, patient-centered care, and complications...
Chapter 57 1.Explain the glycosylated hemoglobin (hemoglobin A1c), what it reflects (in terms of blood chemistry), and why it is an important adjunct to (total) blood glucose levels in monitoring the response of diabetes to therapy. 2. Be able to discuss diabetic ketoacidiosis 3. Identify the main groups of oral antidiabetic drugs (and a prototype in each). Compare and contrast their main mechanisms of action, their main adverse responses, and drug–drug interactions 4. State three classic signs or symptoms of diabetes and identify...