Chronic Kidney Disease
GFR (ml/min)
Stage 1 Normal function 90 or higher
Stage 2 Mild loss of function 60-89
Stage 3a Mild to moderate 45-59
Stage
... [Show More] 3b Moderate to severe 30-44
Stage 4 Severe loss of function 15-29
Stage 5 Kidney failure less than 15
Dialysis is required when Glomerular Filtration Rate (GFR) is less than 15
37 million American adults have chronic kidney disease
From the National Kidney Foundation
End of Lecture 17,
Part 1
✓ Part 1. Blood Flow Through the Kidneys Part 2. The Nephron
Part 3. Filtration
Part 4. Glomerular Filtration Rate
Chapter 19
BIO 3200
Human Physiology
The Kidneys
Lecture 17
Part 2: The Nephron
The Urinary System
• The kidneys are located on the back wall of the abdomen
• Note the prominent
renal arteries and renal veins providing substantial circulation through the kidneys
• The kidneys regulate
the volume and composition of the blood and remove waste products
The Kidney
The blood supply circulates up and around the nephrons. The nephron is the functional unit of the kidney
The Nephron
• The strategy of the kidney is to transfer everything to the urine and then take back what is needed
• Chemicals in the
blood will show up in the urine unless they are very effectively reabsorbed
The Nephron
• The blood supply of the nephron breaks up into capillaries in the glomerulus and surrounding the tubules
• The efferent arteriole connects the two capillary beds
• Blood is filtered into the nephron from the glomerulus and reabsorption occurs in the tubules
HUMAN PHYSIOLOGY, LECTURE 17, PART 2 12
Structure of the Nephron
The ascending and descending limbs of the loop of Henle are untwisted in this drawing
The Nephron
Most nephrons (80%) are contained in the cortex Juxtamedullary nephrons (longer nephrons, 20%) descend into the medulla
End of Lecture 17,
Part 2
Part 1. Blood Flow Through the Kidneys
✓ Part 2. The Nephron Part 3. Filtration
Part 4. Glomerular Filtration Rate
Chapter 19
BIO 3200
Human Physiology
The Kidneys
Lecture 17
Part 3: Filtration
Filtration, Reabsorption, Secretion, Excretion
Filtration, Reabsorption, Secretion, Excretion
Filtration
Blood except for blood cells and proteins is filtered into the lumen of the nephron in Bowman’s capsule
Reabsorption occurs as the urine travels through the proximal tubule, loop of Henle, distal tubule and collecting duct
About 20% of the plasma volume is filtered into the lumen of the nephron
More than 99% of that filtrate volume is reabsorbed
Filtration
Filtration occurs from the glomerular capillary into the lumen of Bowman’s capsule.
The filter is formed by the endothelial cells of the capillaries and the podocytes forming the boundary of Bowman’s capsule.
Note the foot processes on the podocytes.
Filtration
Plasma is filtered through the capillary endothelium, the basal lamina and the podocytes lining Bowman’s capsule.
Filtration does not allow blood cells or most blood proteins to enter the lumen of the nephron
Filtration Pressure
• Filtration is driven by pressure
• Net filtration
pressure is the difference between the blood pressure, the hydrostatic pressure in the lumen of Bowman’s capsule and the colloid osmotic pressure
HUMAN PHYSIOLOGY, LECTURE 17, PART 3 23
The colloid osmotic [Show Less]