A&P Lecture Chapter 11: Renal Physiology, Fluid and Electrolytes

Urine formation occurs in 3 steps:

Filtration ( = ultrafiltration), reabsorption, tubular secretion

Filtration ( = ultrafiltration):

Glomerular filtrate (like plasma)

____ % of filtrate get reabsorbed back into the body

99

1. Glomerular filtrate contains ____

2. These will get ____

1. Everything plasma has (i.e., glucose, amino acids, small albumins)

2. 100% reabsorbed

1. Glomerular filtrate also contains ____

2. These are ____, meaning some are reabsorbed, and some are excreted as urine

1. Ions (i.e., sodium, potassium, chloride, magnesium, bicarbonate, phosphate)

2. Regulated

Regulation of some ions in glomerular filtrate is under hormonal control

1. Sodium reabsorption is under ____ control.

2. Calcium and magnesium reabsorption is under ____ control.

1. Aldosterone

2. PTH

Glomerular filtrate also contains ____

Urea, creatinine, creatine

1. Urea in glomerular filtrate is ____

2. Creatinine in glomerular filtrate is ____

1. Filtered, reabsorbed, and secreted

2. Filtered but not reabsorbed

GFR is also called:

Renal clearance

Glomerular filtrate also contains ____ because it is just like plasma

Water

Glomerular filtrate should not contain ____ or ____

Hemoglobin, RBCs

Blood in urine may be because of ____, ____, ____

Pyuria, nephritis, nephropyelitis

Nephritis occurs when the ____ or ____ are inflamed

Glomerulus, tubules

1. Nephropyelitis occurs when the ____, ____, ____, or ____ is inflamed

2. This can happen in a ____

1. Ureter, urethra, urethra, renal pelvis

2. UTI

____ % of filtrate is reabsorbed at renal tubules

99

1. Tubular secretion is when ____, which takes place in ____

2. ____ can be added

1. Substances are added to filtrate, DCT

2. Potassium, phosphate, antibiotics, conjugated hormones, toxins/poisons

Filtration is a passive transport process, meaning ____, and ____

No ATP is needed, only a concentration gradient is needed

Efferent arteriole is ____, and afferent arteriole is ____

Narrow, wider

Hydrostatic pressure of blood ( = blood pressure) is equal to:

60 mmHg

Osmotic pressure ( = colloid pressure) is equal to:

32 mmHg

Filtrate hydrostatic pressure ( = capsular hydrostatic pressure) is equal to:

18 mmHg

Hydrostatic pressure of blood works to ____

Get fluid out into the Bowman's capsule

Osmotic pressure works to ____

Pull fluid into the blood capillary

Filtrate hydrostatic pressure works to ____

Pull fluid into the blood capillary

Net filtration pressure is equal to:

Hydrostatic pressure of blood - osmotic pressure + capsular hydrostatic pressure = 10 mmHg

Positive net filtration pressure allows ____

Filtrate to get into the Bowman's capsule

Autoregulation of GFR means that:

GFR remains relatively constant (125 mL/min) despite blood pressure changes from 80-180 mmHg.

But if blood pressure goes too low, GFR decreases. And if blood pressures goes too high, GFR increases.

Concentration of glomerular filtrate is ____ mOsmols

300

1. As filtrate goes through the PCT, ____, ____, ____, ____, ____, ____, and ____ is reabsorbed

2. Because water and solute are reabsorbed, the concentration ____

3. Before entering the PCT, the filtrate is ____ % and ____ with plasma. After going through the PCT, the filtrate is ____ % and ____ with plasma (____)

1. Glucose, amino acids, proteins, sodium, chloride, calcium, water

2. Does not change and remains 300 mOsmols

3. 100, isotonic, 20, still isotonic, 300

1. As filtrate goes through the descending limb of the loop of henle, ____ goes out

2. Because only water and no solute is going out, the concentration ____

3. By the time the filtrate reaches the tip of the loop of henle, the filtrate is ____ % and ____ with plasma (____)

1. Water

2. Increases (400 → 600 → 800 → 1,000 → 1,200)

3. 5, hypertonic, 1,200

1. As filtrate goes through the ascending limb of the loop of henle, ____ goes out via ____

2. Because sodium is going out, the concentration ____

3. By the time the filtrate reaches the end of the loop of henle, the filtrate is ____ % and ____ with plasma (____)

1. Sodium, active transport (uses ATP)

2. Becomes more and more dilute (1,200 → 1,000 → 800 → 600 → 400 → 300 → 200 → 100)

3. 4.5, hypotonic or isotonic, 100

The ____ part of the descending segment of the loop of henle reabsorbs water, and the ____ part of the ascending segment of the loop of henle reabsorbs sodium

Thin, thick

1. As filtrate goes through the DCT, ____ is reabsorbed under ____ effect and some ____ may be absorbed

2. By the time the filtrate reaches the end of the DCT, the filtrate is ____ % and the concentration becomes ____ with plasma (____)

1. Sodium, aldosterone, water

2. 4.5, hypotonic or isotonic, 300

1. As filtrate goes down the collecting duct and collecting tubule, ____ is reabsorbed under ____ control

2. Because ____ is going out, the filtrate becomes ____

3. By the time the filtrate reaches the end of the collecting duct and collecting tubule, it is now called ____, is ____ %, and is ____ with plasma (____)

4. If the person is ____, more water is reabsorbed. Otherwise, less water is reabsorbed

5. Water reabsorption through the collecting duct and collecting tubule is called ____ because ____

6. If the person does not have ADH, they will have ____

1. Water, ADH

2. Water, more and more concentrated (400 → 600 → 800 → 1,000 → 1,200)

3. Urine, 0.5, hypertonic, 1,200

4. Dehydrated

5. Facultative, it is facilitated by ADH

6. Hormonal diuresis

1. In the PCT, ____ is reabsorbed due to ____ and is called ____ water reabsorption.

2. If there is a problem with the PCT, the person has ____

1. Water, osmotic gradient, obligatory

2. Osmotic diuresis

1. As ____ leaves the ascending segment of the loop of henle, an ____ is created in the ____

2. The concentration increases (____)

1. Sodium, osmotic gradient, renal medulla (outside the nephron)

2. 400 → 600 → 800 → 1,000 → 1,200

1. The Bowman's capsule, glomerulus, PCT, and DCT are in the ____

2. The loop of henle, collecting duct, and collecting tubule are in the ____

1. Cortex

2. Medulla

The juxtaglomerular apparatus has 2 types of cells:

Macula densa cells and JG cells

Macula densa cells of the juxtaglomerular apparatus are cells of the DCT that can detect ____ concentration of filtrate

Sodium

JG cells of the juxtaglomerular apparatus are the source of ____, which helps make ____

Renin, angiotensin II

Transport mechanisms for reabsorption includes:

Osmosis, primary active transport, secondary active transport, facilitated diffusion, Na/Amino acid cotransporter, epithelial Na channels, aquaporins, Na/K/2Cl transporter

Osmosis involves ____ reabsorption

Water

Primary active transport involves ____ reabsorption and includes ____

Sodium, Na/K-ATPase

Secondary active transport involves ____ reabsorption and includes ____

Glucose, SGLT-1, 2

Facilitated diffusion involves ____ reabsorption on the ____ side and includes ____

Glucose, basolateral, GLUT

Na/Amino acid cotransporter involves ____ reabsorption and includes ____

Amino acid, Na/Amino acid

Epithelial Na channels (ENa) involves ____ reabsorption under ____ effect

Sodium, aldosterone

Aquaporins involve ____ reabsorption and includes ____

Water, AQP I & II & III

Na/K/2Cl involve ____ and ____ reabsorption

Sodium, chloride

____ % reabsorption occurs in the PCT

80

PCT cells are ____ and have ____

Cuboidal, microvilli

The apical side of PCT cells have ____

Filtrate

The basolateral side of PCT cells have ____

Blood

____ are on the apical side of PCT cells

Transporters

Transporters on the apical side of the PCT include:

1. Urea transporter

2. Sodium-dependent glucose transporter (SGLT)

3. Renal outer medullary K channels (ROMK)

4. Na/Amino acid cotransporter

5. Aquaporins (AQP I)

Transporters on the basolateral side of the PCT include:

1. Glucose transporter (GLUT 2)

2. Na/K-ATPase pump

SGLT is ____

Secondary active transport

GLUT 2 is ____

Facilitated diffusion

Na/K-ATPase pump is ____

Primary active transport

Calcium and magnesium is reabsorbed in the PCT by ____, not transporters

Paracellular pathway

Albumins are reabsorbed in the PCT by ____

Pinocytosis

____ should not be found in the urine because it indicated renal failure

Albumins

1. In chronic renal failure, ____ are not reabsorbed back into the blood

2. In chronic renal failure, the person will lose ____ % of their body weight within ____ months because ____ are lost with urine

1. Albumins

2. 60, 6, muscles and proteins

DCT cells do not have ____

Microvilli

DCT cells are called ____ cells

Principal

1. On the apical side of DCT cells, ____ allow ____ entry into the DCT cells under aldosterone effect

2. Sodium goes through the DCT cell and then gets reabsorbed into the blood via ____ on the ____ side

1. ENa channels, sodium

2. Na/K pumps, basolateral

____ inserts ENa channels on the apical side of DCT cells

Aldosterone

1. ____ occurs if Na/K pumps of the DCT are mislocated → on the apical side instead of the basolateral side due to gene mutation

2. This causes ____ in the kidneys

1. Polycystic kidney disease

2. Cysts filled with fluid

As sodium enters DCT cells for reabsorption, ____ also follows due to ____

Water, osmotic gradient

1. On the apical side of collecting tubule (CT) cells, ____ allows ____ entry into the CT cell under ADH effect

2. Water goes through the CT cell and then gets reabsorbed into the blood via ____ on the ____ side

1. AQP II, water

2. AQP III, basolateral

ADH helps aquaporins located ____ to go to the ____ to allow water to be absorbed

Inside CT cells, apical side

ADH only acts if there is ____

Water

Loop of henle makes ____ filtrate, so ADH causes water reabsorption in the ____ to make ____ urine

Hypotonic, CT, hypertonic

The longer the loop of henle, the ____ water that can be reabsorbed

More

Filtrate concentration starts as ____ mOsmols, but then gradually increases to ____ mOsmols as filtrate becomes urine

300, 1,200

If ADH is present, ____ is reabsorbed

Water

1. If no ADH is present, ____ is not reabsorbed and ____ occurs

2. There is no ADH in ____

1. Water, diuresis

2. Diabetes insipidus

The collecting tubules also have intercalated cells:

1. Type A intercalated cells excrete ____

2. Type B intercalated cells excrete ____

1. H+ ions in acidosis

2. Bicarbonate ions in alkalosis

Intercalated cells have a ____ mechanism to keep blood pH between ____

Buffering, 7.3 to 7.4

Tubular secretion is when substances are ____ to filtrate throughout ____ of the nephron

Added, the length

1. In tubular secretion, ____, ____, ____, ____, ____, ____, ____, ____, and ____ are added to the filtrate from the blood

2. Substances added to filtrate during tubular secretion will be ____

3. At the same time, ____, ____, and ____ is reabsorbed back into the blood

1. Ammonium, sulfate, organic acids, antibiotics, H+ ions, toxins, conjugated hormones, phosphate, urea

2. Lost with urine

3. Sodium, calcium, bicarbonate

Transport maximum (Tm) refers to:

How much of a substance can be reabsorbed

There is a maximum for how much of a substance can be reabsorbed, because:

There is a limited number of transporters

Tm for glucose =

375 mg/min

(In 1 minute, only 375 mg of glucose can be reabsorbed)

If GFR is 125 ml/min and blood glucose is 100 mg/100 ml of blood, how much glucose is filtered in 1 minute and then how much of that will be reabsorbed?

125 mg glucose will be filtered per minute

Since 375 mg of glucose can be filtered per minute, 100% will be reabsorbed

If GFR is 125 ml/min and blood glucose is 300 mg/100 ml of blood, how much glucose is filtered in 1 minute and then how much of that will be reabsorbed?

375 mg glucose will be filtered per minute

Since 375 mg of glucose can be filtered per minute, 100% will be reabsorbed

If GFR is 125 ml/min and blood glucose is 400 mg/100 ml of blood, how much glucose is filtered in 1 minute and then how much of that will be reabsorbed?

500 mg glucose will be filtered per minute

Since 375 mg of glucose can be filtered per minute, only 375 mg can be reabsorbed and the remaining 125 mg will be excreted as urine

Transport maximum depends on renal threshold, which is ____

The limit to which a certain substance can be kept in the body

GFR = ____ L/day

180

1. GFR can be calculated with ____ or ____

2. Creatinine is produced by the body, but inulin (polysaccharide) must be ____

1. Creatinine, inulin

2. Given to the body

GFR = ____ x ____ / ____

Urine concentration of creatinine (mg/ml), urine flow (ml/min), plasma concentration of creatinine (mg/ml)

What is the value of GFR, given that:

Urine concentration of creatinine = 125 mg/ml

Urine flow = 1 ml/min

Plasma concentration of creatinine = 1 mg/ml

125 ml/min

Urine flow can be calculated by:

1. First, ____

2. Then, use the bathroom again after ____ minutes, but ____

3. Divide the ____ by time passed to see how ____ ( = urine flow)

4. Example: After 30 minutes, 300 ml of urine came out → ____ / ____ = ____

1. Empty your bladder fully

2. 30, measure how much urine comes out

3. Measured amount of urine, time passed, much urine was produced per minute

4. 300 ml, 30 min, 10 ml/min

Renal clearance is:

The volume of plasma that has been cleared of a certain substance per unit time (usually per minute)

Renal absorption for glucose is ____ %, and renal clearance for glucose is ____ % and

100, 0

(Because 100% of the glucose was reabsorbed back into the blood, 0% of the blood is cleared of glucose)

Renal absorption for creatinine is ____ %, and renal clearance for creatinine is ____ % and

0, 100

Every minute, ____ ml of blood goes through the kidneys

1250

____ is filtered in the kidneys, not the ____

Plasma, whole blood

1. Plasma is ____ % of blood

2. This means that out of the ____ ml of blood traveling in the kidneys, only ____ % is actually filtered

3. ____ ml of plasma is filtered per minute

4. Only ____ ml is glomerular filtrate, so the filtration fraction → ____ = ____

1. 55

2. 1250, 55

3. 700

4. 125, 125/700, 16-18%

Of all the plasma going through the kidneys, only ____ % is actually filtered into the nephrons

16-18