Basic Urinary System Functions 1.5.26

Question 1

What are the major renal functions?

Answer 1

1. Acid-base regulation
2. Water/Fluid balance
3. Electrolyte Balance
4. Toxin and Waste product removal
5. Blood pressure production
6. Enzyme/hormone production (EPO, renin)
7. Vitamin D activation

Question 2

What percentage of total Cardiac Output (CO) is delivered to the kidneys at rest?

Answer 2

Approximately 20%

Question 3

What is the primary hormone responsible for regulating water/fluid balance in the kidney?

Answer 3

Antidiuretic Hormone (ADH), also known as Vasopressin.

Question 4

Why is the renal medulla more at risk for hypoxia than the cortex?

Answer 4

It receives less than 1% of total renal blood flow to prevent “washing out” the medullary osmotic gradient.

Question 5

Which enzyme is released by the Juxtaglomerular (JG) cells to initiate blood pressure regulation?

Answer 5

Renin.

Question 6

What hormone does the kidney produce to stimulate red blood cell production in the bone marrow?

Answer 6

Erythropoietin (EPO).

Question 7

Which specific form of Vitamin D is produced by the kidney?

Answer 7

Calcitriol

Question 8

How do the kidneys contribute to acid-base regulation?

Answer 8

By reabsorbing Bicarbonate (HCO_3-) and secreting Hydrogen ions (H+).

Question 9

Where is the glomerulus located in a Juxtamedullary nephron?

Answer 9

In the cortex, but close to the medulla.

Question 10

Where is the glomerulus located in a Cortical (superficial) nephron?

Answer 10

In the outer and middle cortex.

Question 11

How deep do the loops of Henle penetrate in Juxtamedullary nephrons?

Answer 11

They are long loops that extend deeply into the renal medulla.

Question 12

How deep do the loops of Henle penetrate in Cortical nephrons?

Answer 12

they are short loops that extend only to the junction of the cortex/medulla or the outer zone of the medulla.

Question 13

Which type of nephron has a higher relative filtration rate?

Answer 13

Juxtamedullary nephrons.

Question 14

Which type of nephron has a lower relative filtration rate?

Answer 14

Cortical (superficial) nephrons.

Question 15

Are vasa recta present in Juxtamedullary nephrons?

Answer 15

Yes, they are present.

Question 16

Are vasa recta present in Cortical (superficial) nephrons?

Answer 16

No

They are surrounded by peritubular capillaries

Question 17

Which nephron type is more numerous in most domestic mammalian species

Answer 17

Cortical (superficial) nephrons (though the ratio varies by species and their ability to concentrate urine)

around 85%

Question 18

What is a nephron?

Answer 18

fundamental structural and functional unit of the kidney.

Each kidney contains hundreds of thousands to millions of these units.

Question 19

Which nephron type is primarily responsible for concentrating urine?

Answer 19

Juxtamedullary nephrons.

Question 20

Explain the nephron more in detail

Answer 20

Tiny tubule responsible for filtering blood, reabsorbing essential nutrients and excreting waste as urine.

Question 21

What are the two main parts of a nephron?

Answer 21

Renal corpuscle : the filter where blood enters, includes the Glomerulus and Bowman’s capsule

Renal Tubule : the refinery where the filtrate is modified. Includes the proximal convoluted tubulte (PCT), Loop of Henle, and Distal Convoluted Tubule (DCT)

Question 22

The length of the loop of Henle varies according to the amount of water in the habitat. Which kidney belongs to the animal living in the desert?

Answer 22

Image shows a very long loop of Henle

Longest loop of Henle belongs to the Kangaroo Rat

Question 23

What is the first step of urine formation where plasma leaves the blood?

Answer 23

Glomerular Filtration.

The movement of fluid and solutes from the glomerular capillaries into Bowman’s space.

Question 24

In which step do essential substances from the filtrate move from the tubule back into the peritubular capillaries?

Answer 24

Tubular Reabsorption. (step 2)

Question 25

What is the term for moving solutes from the peritubular capillaries into the tubule?

Answer 25

Tubular Secretion. (step 3)

Question 26

Where does the process of filtration specifically take place?

Answer 26

Between the Glomerular capillaries and Bowman's capsule.

Question 27

What is the final step where urine leaves the nephron?

Answer 27

Excretion.

Question 28

Which two steps of urine formation are considered "required"?

Answer 28

Step 1 (Filtration) and Step 4 (Excretion).

Question 29

Why are Reabsorption and Secretion considered "optional" or variable steps?

Answer 29

Because not all substances need to be reclaimed or added; the kidney chooses what to move based on the body's needs.

Question 30

In which step does the body "reclaim" essential nutrients like glucose and amino acids?

Answer 30

Tubular Reabsorption (Step 2).

Question 31

In which step are drug metabolites and excess K+ often added to the filtrate?

Answer 31

Tubular Secretion (Step 3).

Question 32

What is the definition of Glomerular Filtration Rate (GFR)?

Answer 32

The volume of fluid filtered from the glomerulus into the Bowman's space per unit time.

Question 33

**What is the definition of Filtered Load?

Answer 33

The total amount of a specific substance (S) filtered into Bowman's space per unit time.

Question 34

What is the formula for calculating Filtered Load?

Answer 34

Ps x GFR (Plasma concentration of substance times Glomerular Filtration Rate).

Question 35

If GFR is 180 L/day and Plasma Sodium is 3.5 g/L, what is the Filtered Load of Na+?

Answer 35

630 g/day (180 times 3.5).

Question 36

Why is GFR considered the best overall measure of kidney function?

Answer 36

Because it represents the total volume of fluid the kidneys can "clean" per unit of time.

Question 37

How do you calculate the Amount Reabsorbed of a substance?

Answer 37

Amount Filtered – Amount Excreted.

Question 38

How do you calculate the Amount Secreted of a substance?

Answer 38

Amount Excreted – Amount Filtered.

Question 39

**What is the definition of Renal Clearance (Cx)?

Answer 39

The volume of plasma cleared of a specific substance per unit time.

Question 40

**What is the standard equation for Clearance (Cx)?

Answer 40

Cx = [Ux x V] / Px Ux = urine concentration of substance x (mg/ml) V = urine flow rate (mL/min) Px = plasma concentration of substance x (mg/mL) Ux X V = urinary excretion rate of substance x

Question 41

What properties must a substance have for its clearance to exactly equal GFR?

Answer 41

It must be freely filtered and have no net reabsorption, secretion, or metabolism by the kidney. Used to estimate GFR because their clearance equals GFR: Inulin (the gold standard) and Creatinine (clinical marker).

Question 42

If the clearance of a substance is GREATER than the GFR (Cx > GFR), what does this indicate?

Answer 42

It indicates net secretion of that substance from the peritubular capillaries into the tubule.

Question 43

Name two substances that typically have a clearance greater than GFR.

Answer 43

Potassium (K+) and Hydrogen ions (H+)

Question 44

If the clearance of a substance is LESS than the GFR (Cx < GFR), what does this indicate?

Answer 44

It indicates net reabsorption of that substance from the tubule back into the blood

Question 45

Name two types of substances that typically have a clearance much lower than GFR.

Answer 45

Glucose and Amino acids (both are normally 100% reabsorbed).

Question 46

What are the two primary "jobs" or phases of the bladder?

Answer 46

Filling (Storage) and Voiding (Peeing).

Question 47

Which branch of the nervous system predominates during the Filling phase?

Answer 47

The Sympathetic nervous system.

Question 48

Which branch of the nervous system is responsible for the Voiding phase?

Answer 48

The Parasympathetic nervous system.

Question 49

Which nerve provides sympathetic innervation to the bladder?

Answer 49

The Hypogastric nerve.

Question 50

Which nerve provides parasympathetic innervation to stimulate the detrusor muscle?

Answer 50

The Pelvic nerve.

Question 51

The Pudendal nerve provides what type of innervation to the external urethral sphincter?

Answer 51

Somatic (voluntary) innervation

Question 52

During filling, does the detrusor muscle contract or relax?

Answer 52

It relaxes to allow for low-pressure storage of urine.

Question 53

What must happen to the urethral sphincters for voiding to occur?

Answer 53

They must relax while the detrusor muscle contracts.

Question 54

Which vessel directly supplies blood to the glomerulus?

Answer 54

The Afferent Arteriole.

Question 55

Which specific artery gives rise to the Afferent Arterioles?

Answer 55

The Interlobular Artery (also called Cortical Radiate Artery). which comes from the arcuate artery

Question 56

What is the primary function of the Renal Venous Side compared to the arterial side?

Answer 56

It collects processed blood and returns reabsorbed water and solutes to general circulation rather than "supplying" oxygen to the nephron.

Question 57

Where does the Renal Vein deposit the blood once it exits the kidney?

Answer 57

Into the Caudal Vena Cava.