Term
| What are the two sections of the nephron? |
|
Definition
1. the glomerulus - filtering unit
2. the tubular unit - PCT, loop of Henle, DCT, and cortical collecting tubule |
|
|
Term
| How much fluid is filtered by the glomeruli everyday? |
|
Definition
| 2.5 million glomeruli filter about 187 liters per day |
|
|
Term
| How can one visualize the difference between the PCT and DCT? |
|
Definition
| The PCT has brush borders for added surface area! |
|
|
Term
| How much of the total filtrate is absorbed in the PCT? |
|
Definition
| 2/3. Only 1/3 is left afterwards |
|
|
Term
| Does the PCT change the concentrations of the filtrate? |
|
Definition
| No, it absorbs iso-osmotically so that solute concentrations remain the same |
|
|
Term
| What is reabsorbed in the PCT? |
|
Definition
| Na, K, and urea. HCO3 reabsorption and H Secretion also occurs here |
|
|
Term
| Is the fluid iso-osmotic when it enters the loop of henle? |
|
Definition
| Yes, b/c the PCT does not change the concentrations beforehand |
|
|
Term
| What part of the loop of henle is permeable to water, and which part is not? |
|
Definition
The descending portion is permeable, and the ascending portion is not permeable.
Note: the first part lets water through |
|
|
Term
| What does the loop of henle do? |
|
Definition
| It reabsorbs Na. About 25% of the Na that is filtered at the glomerulus is reabsorbed bythe loop of Henle, whereas only about 5% of the water is reabsorbed. K is also reabsorbed here |
|
|
Term
| What is the first functional part of the DCT and what does it do? |
|
Definition
1. Early DCT - the epithelial cells have many mitochondria. The cells are not under hormonal control, but do have transport mechanisms for various solutes. Responsible for fine tuning parts of the urine.
Reabsorption - Na and Cl
Secretion - H and K and ammonia
Permeable to water? - normally not |
|
|
Term
| What is the second functional part of the DCT and what does it do? |
|
Definition
It is the cortical collecting tubule. It differs from the early DCT in that it is under hormonal control.
Under normal circumstances, it is impermeable to water and urea.
When under hormonal regulation, the CCT becomes permeable to water, but not urea |
|
|
Term
| How exactly does the early DCT differ from the late DCT? |
|
Definition
The early part is NOT under hormonal regulation, but the later part is. This means that ADH will directly affect the water reabsorption of the late DCT, but not the early DCT.
Also, the early DCT reabsorbs Na and Cl, while secreting H and K and ammonia. The late DCT is only involved with water reabsorption, when activated hormonally. |
|
|
Term
| Are the collecting ducts under hormonal control? |
|
Definition
| yes, they are under intense hormonal control |
|
|
Term
| What anatomic characteristic of the kidney allows urine to become concentrated? |
|
Definition
| The fact that nephrons are located in part within the cortex and in part within the medulla. In combination with the collecting ducts, urine can flow through the renal medullary area to concentrate. |
|
|
Term
| What are the two types of cells lining the cortical collecting tubules? |
|
Definition
Principle Cell - involved in Na, Cl, K, and water reabsorption
Intercalated Cells - alpha and beta types |
|
|
Term
| What do the intercalated cells do? |
|
Definition
Intercalated alpha - secrete H, but do not reabsorb Na
Intercalated Beta - secrete bicarb
Both are significant in acid/base regulation |
|
|
Term
| What part of the kidney is not iso-osmotic with the plasma? |
|
Definition
| The renal medulla. The renal cortex is iso-osmotic |
|
|
Term
| Why is it important that the renal medulla remain hypertonic compared to the rest of the plasma? |
|
Definition
| It is important for concentrating urine. All of the collecting ducts must pass through the hypertonic section of the renal medulla before entering the renal pelvis. This is responsible for concentrating the final urine. |
|
|
Term
| What are the two subpopulations of nephrons and how do they differ? |
|
Definition
Cortical nephrons - found in the renal cortex; comprise 85% of nephron pop.; PCT, DCT, and loop of Henle are located in the cortex in these nephrons (the tip of their loops enter the outer zone of the medulla)
juxtamedullary nephrons - glomeruli are located in the cortex along with the PCT and DCT; the loop of henle dips into the inner zone of the renal medulla; efferent arterioles form the vasa recta |
|
|
