Processes in the nephron 1. Filtration: throw everything out 2. - - PowerPoint PPT Presentation

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Processes in the nephron 1. Filtration: throw everything out 2. - - PowerPoint PPT Presentation

Oct 08, 2022 134 likes •509 views

Processes in the nephron 1. Filtration: throw everything out 2. Reabsorption: bring back what you want to keep 3. Secretion: throw out what you really want to get rid of 4. Excretion: what leaves in the urine Water balance involves the

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Processes in the nephron

  • 1. Filtration: throw

everything out

  • 2. Reabsorption: bring

back what you want to keep

  • 3. Secretion: throw out

what you really want to get rid of

  • 4. Excretion: what leaves

in the urine

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Water balance involves the homeostatic regulation

  • f ECF osmolarity
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Osmosis and osmotic pressure

Figure 5.2

  • p. 125
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Water reabsorption involves the loops of Henle and the collecting ducts in the medulla

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Formation of osmotic gradient by the loop of Henle

NOTE: don’t worry about details; just know that the loop of Henle is the part of the nephron responsible for generating the osmotic gradient

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Regulated water permeability in the collecting duct

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Vasopressin

  • also known as antidiuretic hormone (ADH)
  • hormone released at the posterior pituitary
  • released by neurosecretory cells
  • hormone release regulated by osmoreceptors located in

hypothalamus

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Neurosecretory cell

  • neurosecretory cells have their cell bodies located in the hypothalamus
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Vander’s Physiology 12th edition, Fig. 11-13a

Hypothalamus and pituitary

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Neurosecretory cells of the hypothalamus

anterior pituitary posterior pituitary Vander’s Physiology 12th edition, Fig. 11-13b

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Vasopressin regulates water permeability by increasing aquaporins (AQP2) in the apical plasma membrane of the collecting duct

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Collecting duct

collecting ducts near papilla the collecting duct is lined with a crisp, clear, cuboidal epithelium

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Patient D

What is the term for excessive urine production? Why does hyperglycemia in diabetes mellitus cause increased urine production? What sensors are responsible for promoting thirst?

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Saturation of sodium-glucose cotransporters in the kidney tubules leads to polyuria

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Patient D: Test Results

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Osmolarity: solute/liter of water Osmolality: solute/kilogram of water

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Diabetes insipidus: polyuria due to a defect in the ability to reabsorb water and concentrate urine

central diabetes insipidus: deficiency of vasopressin nephrogenic diabetes insipidus: kidney doesnt respond to vasopressin

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What type of cell releases vasopressin? Where are the cell bodies of vasopressin-secreting cells located? What sensors regulate vasopressin release, and where are they located?

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Patient D

Diagnosis: adipsic diabetes insipidus due to tumor in the hypothalamus Treatment: vasopressin agonist; guidelines for fluid intake

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Patient E

What does a diuretic do? What specific part of the nephron is damaged to cause proteinuria?

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Filtration Occurs in the Renal Corpuscle

Figure 19.5

  • p. 596
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Filtration membrane

Figure 19.5c, d; p.596 schematic of a cross-section through two capillary loops

  • f the glomerulus

schematic cross-section through filtration membrane, highly magnified

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Proteinuria: sign of damage to the filtration membrane

Barriers to filtration of protein:

  • 1. negative charge in glycocalyx
  • 2. meshwork of proteins in

glomerular basement membrane

  • 3. meshwork of proteins in the slit

diaphragm

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serum creatinine

metabolism of creatine from skeletal muscle excretion in the urine Does the patient’s increasing serum creatinine indicated that her kidney function is deteriorating or improving?

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Diabetic Nephropathy

  • leading cause of end-stage renal disease (end stage renal disease is

kidney function so low it requires renal replacement: either dialysis or kidney transplant)

  • hyperglycemia and/or decreased insulin signaling cause changes to

the glomerulus to cause leaky filtration barrier and proteinuria

  • proteinuria damages nephrons and leads to nephron loss
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Incidence of ESRD by primary diagnosis

From US Renal Data System 2014 Report http://www.usrds.org/2014/view/Default.aspx

Data from 1980-2012 Data from 1996-2014

From US Renal Data System 2016 Report http://www.usrds.org/2016/view/Default.aspx

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Glomerular filtration rate (GFR)

  • rate of fluid flow into Bowman’s space
  • important measure of kidney function
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Renal Clearance

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Processes in the nephron

  • 1. Filtration: throw

everything out

  • 2. Reabsorption: bring

back what you want to keep

  • 3. Secretion: throw out

what you really want to get rid of

  • 4. Excretion: what leaves

in the urine

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Inulin

  • don’t confuse with insulin
  • plant carbohydrate (must be injected)
  • freely filtered
  • neither reabsorbed nor secreted
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Filtered Load

  • filtered load = amount filtered
  • filtration: bulk flow of plasma and

all small substances dissolved in it

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