Ch18 Renal Function

APK2105C @ UD | Dr. Nguyen | Module 4 | Ch 18

ions; blood; osmolarity; waste

Main functions of the kidneys:

• Ensure there’s enough _____ in the blood (e.g. Na⁺, K⁺, Ca²⁺, etc.)

• Ensure an appropriate ______ volume

• Ensure an appropriate _______ (solutes to plasma)

• Mechanism to remove metabolic _______ and foreign substances

• Ultimately regulate ALL body fluid volume and composition

cortical nephron

Which nephron is found primarily in the kidney’s cortex?

juxtamedullary nephron

Which nephron is found b/t the border of the cortex and medulla?

longer; vasa recta

Besides being (1) closer to the cortical/medullary border and (2) having a ______ loop of Henle, what is another characteristic of the juxtamedullary nephron?

distal; arterioles

In the juxtamedullary nephron, the _______ tubule is wedged b/t the efferent and afferent _________.

collecting duct; urine

The term renal filtrate is always used until it leaves the _________ ______, where it’s then called ______.

granular cells; renin

What specialized cells (AKA juxtaglomerular cells) are found in the wall of the afferent arteriole? What hormone do they secrete, that ensures there’s enough driving force (i.e. blood pressure and volume) for the blood to enter the glomerulus?

macula densa cells; paracrine

What specialized cells are found in the wall of the distal tubule? What hormone do they secrete if osmolarity and water content aren’t normal (thus affecting blood volume and pressure)?

afferent; glomerulus; efferent; peritubular; vasa recta

Series blood flow in the kidneys:

1. Blood enters _______ arteriole

2. Goes into _______

3. Blood is filtered into Bowman’s capsule

4. Remaining blood exits via the _______ arteriole

5. Blood enters the _______ capillaries, where gas exchange for the nephron occurs

6. [In juxtamedullary nephron only] Blood enters _______ _______

filtration

Basic nephron functions:

• Bulk flow of protein-free plasma → Bowman’s capsule

• Non-specific

• Internal env. → external env.

reabsorption

Basic nephron functions:

• Transport of molecules from renal tubule lumen → peritubular capillaries

• External env. → internal env.

secretion

Basic nephron functions:

• Transport of molecule from the peritubular capillaries lumen (i.e. plasma) → renal tubule (i.e. renal filtrate)

• Internal env. → external env.

filtration and secretion

Which process(es) involve(s) movement from the internal → external environment?

reabsorption

Which process(es) involve(s) movement from the external → internal environment?

renal filtrate

Plasma-derived liquid that gets filtered at the renal corpuscle and travels through the tubular portion of the nephron

epithelium

Bowman’s capsule has a layer of ________ in both its inside and outside layer.

internal

A capillary is part of the ________ environment.

external

Bowman’s capsule/space and tubules are part of the ________ environment.

glomerular filtration pressure (GFP)

Net filtration pressure of four forces: P_GC, π_GC, P_BC, and π_BC

GFP = (P_GC + π_BC) - (P_BC + π_GC)

GC hydrostatic pressure (P_GC)

Pressure that pushes fluid out of the glomerular capillaries into the Bowman’s capsule; favors filtration

GC osmotic pressure (π_GC)

Pressure that pulls fluid into the glomerular capillary, primarily due to proteins; against filtration

BC hydrostatic pressure (P_BC)

Pressure from fluid that pushes it back into the glomerular capillary; against filtration

BC osmotic pressure (π_BC)

Pressure that pushes water into Bowman’s capsule; favors filtration

favor filtration

Do P_GC and π_BC favor or oppose filtration?

oppose filtration

Does P_BC and π_GC favor or oppose filtration?

glomerular filtration rate (GFR)

volume of plasma filtered per min; typically 125 mL/min

filtration fraction

ratio of the GFR to renal plasma flow (typically 625 mL/min)

125 / 625 mL/min = 20%

filtered load

• The quantity of a solute that is filtered per min

• GFR x Plasma [X] (how much of the solute is in the plasma)

• Will increase if either of these terms increases

reabsorbed; work

Because GFR is so large, even small changes would result in a HUGE effect on the volume of fluid filtered. So, if GFR increases, more solute must be ________, requiring more _______.

mean arterial pressure (MAP)

What is the primary factor in GFR?

GC hydrostatic pressure

Which of the Starling forces is impacted by a change in MAP?

plateau; work; normal fluctuations

The ______ in this graph shows that the body doesn’t need to ______ more for GFR for ________ __________ in BP.

actively

Are solutes mainly passively or actively reabsorbed?

renal tubule wall (cuboidal epithelium)

Which structure has a greater barrier to reabsorption?

capillary wall (simple epithelium)

Which structure has a smaller barrier to reabsorption?

water; up

________ reabsorption follows solute movement. It moves ____ the osmotic pressure gradient.

simple diffusion; lipophilic; concentration gradient

In order for a solute to be passively reabsorbed through ______ ______, it must be membrane-permeant (i.e. _______) and follow a _______ ______.

transport maximum (T_m)

• Highest rate (mg/min) at which reabsorption can occur for a substance.

• Remember: Carrier proteins can become saturated.

  • Different molecules have different number of receptors.

renal threshold

• Plasma concentration of a solute at which “spillover” into the urine occurs.

• Means that it has already reached the transport max.

increases; decreases; glucose; facilitated diffusion

Glucose reabsorption:

1. The Na⁺/K⁺ pump ________ [K⁺] and ________ [Na⁺] inside the cell via primary active transport

2. Na⁺ is brought into the cell w/ ________ via secondary transport

3. Increased [glucose] drives it to be passively reabsorbed into the plasma/capillary via ________ ________

increased; increased; decreased; decreased

Clinical correlation - Diabetes and renal disease:

1. Elevated plasma [glucose]

2. ________ solute in renal filtrate (b/c carriers are saturated)

3. ________ osmolarity of renal filtrate

4. ________ water reabsorption (b/c water remains in renal tubule)

5. ________ water in plasma (b/c of less reabsorption)

6. Diuresis, dehydration, thirst

active transport

Through which type of transport are ions, waste products, and foreign substances secreted?

PCT; leaky; microvilli; mitochondria; active

Non-regulated reabsorption occurs in the ______ and is characterized by…

1. ______ tight junction

2. A lot of ________

3. A lot of ________, meaning it occurs via _______ transport

4. NO secretion

DCT; microvilli; mitochondria; ADH

Regulated reabsorption occurs in the ______ and is characterized by…

1. ______ tight junction

2. Little amount of _______

3. Little amount of _______

4. ______ receptors on the basolateral membrane

5. Secretion

PCT

Is all glucose reabsorbed in the PCT or DCT?

PCT

Where is most of Na⁺ and H₂O (follower) reabsorbed?

PCT

Does most reabsorption occur in thee PCT or the DCT?

excretion

Elimination of solute and water in the form of urine

filtration; secretion; reabsorbed

Substances can enter the tubule via ________ or _______. It is all excreted unless it is ________.

E = F - R + S