Unit 3 Lecture 1: Intro to Renal Physiology

Question 1

What is the renal cortex & renal medulla

Answer 1

The outer portion is the cortex & the inner more part is the medulla; both are key to filtration

Question 2

What are the main roles of the Kidney

Answer 2

1. Fluid and Ion homeostasis
2. Waste excretion
3. Drug removal (can determine when it can be removed)
4. Hormone production
5. Glucose synthesis

Question 3

When it comes to Fluid and Ion homeostasis what does this include?

Answer 3

• ECF volume/blood pressure (more fluid in the system can acutely change blood pressure)
• Regulates osmolarity and ion balance (it can secrete or absorb many ions depending on how the body is feeling or excrete or absorb more water depending on how much water the body has)
• Can balance out pH by H+ excretion or reuptake

Note: A lot of fluid and ion homeostasis is done through either excretion or uptake of the things mentioned above

Question 4

What are some examples of hormones produced or activated when it comes to the kidneys?

Answer 4

• Erythropoietin (EPO)
• Renin ==> Angiotensin 2
• Vitamin D activation

Question 5

Total Body Fluid Volume is?

Answer 5

The amount of fluid in the entire body if you were to dehydrate every cell: 40L

• 3L of it is plasma

Question 6

How much blood and plasma do the kidneys receive?

Answer 6

The renal blood flow is 22% of CO (1500L/day) but since plasma is 60% of blood, that is equal to 900L/day

Question 7

Do the kidneys filter blood itself?

Answer 7

The kidneys technically filter through the plasma in the blood which makes up 60% of the blood.

HOWEVER; Only 20% of the renal plasma flow is filtered by the glomerulus (180L/day)

REMEMBER: 60% of renal blood flow is taken up (renal plasma flow) but of that 60%, only 20% of the renal plasma flow is filtered through the glomerulus)

Question 8

According to the GFR we should lose about 180L/day but that doesn’t make sense. Why is that?

Answer 8

We realistically lose only 1.5L/day because most of the fluid lost is reabsorbed

Question 9

Explain how the glomerulus works when it comes to plasma and blood?

Answer 9

The glomerulus takes in plasma and blood through the afferent arteriole and siphs through it to see what ions and hormones it needs to take then whatever is not needed is sent back to the venous system via the efferent arteriole

Question 10

When ions and hormones are filtered by the glomerulus where do they head down through?

Answer 10

They head down through the Bowman’s Capsule

Question 11

If we have 625mL plasma/min arriving at the afferent arteriole and into the glomerulus and we only filter 20% of it, how much plasma is filtered? How much goes back to the vasculature?

Answer 11

125mL/min is filtered; 500mL plasma/min goes back to the vasculature

Question 12

When the plasma is being filtered what is something unique that occurs with the fluid?

Answer 12

More than 19% of the 20% of fluid is going to be reasborbed into the peritubular capillary and into the venous system; cannot lose too much fluid in one sitting

Note: >99% is being reabsorbed while <1% is being secreted (5mL leaves; 620mL remains in the system)

Question 13

What is the Juxtaglomerular apparatus?

Answer 13

Is it the site where Renin is produced

Question 14

Explain the path of filtrate from the glomerulus

Answer 14

1. Glomerulus to Bowman’s space (Renal corpuscle)
2. Proximal convoluted tubule
3. Proximal straight tubule
4. Descending thin loop of henle
5. Ascending loop of henle
6. Ascending thick loop
7. Distal convoluted tubule
8. Cortical collecting duct
9. Medullary collecting duct
10. Renal Pelvis

Question 15

What is the pathway for renal blood supply?

Answer 15

1. Renal Artery
2. Afferent Arteriole
3. Glomerulus (i.e. Capillaries)
4. Efferent Arteriole
5. Pertibular Capillaries or Vasa Recta
6. Venules
7. Renal Vein

Note: Typically after afferent arteriole blood should go to the capilaries then the veins but they go to the efferent arteriole instead of the veins

Question 16

At different parts of the nephrons, what is happening?

Answer 16

Different ions will be secreted or absorbed

Note: Back and forth filtration and secretion happens through both passive and active transport

Question 17

How many types of nephrons are there? What are they called?

Answer 17

2 Nephrons; Juxtamedullary nephrons & Cortical Nephrons

Question 18

What are some distinct features when it comes to Juxtamedullary and Cortical Nephrons?

Answer 18

1. Both are in the renal corpuscle
2. Cortical = shorter loop of Henle
3. Most nephrons = cortical (80%)
4. Large vasa recta in Juxtamedullary
5. More concentrated urine = long Henle loop = Juxtamedullary
6. Excretory & regulatory functions (water reabsorption) = Cortical

Question 19

Define Glomerular filtration

Answer 19

Non-discriminant filtration of protein-free plasma from glomerulus into Bowman’s Capsule

• Non-discriminant - The size of the holes determine what siphs through

Note: This allows small ions and proteins to go through and prevent RBCs and WBCs from being filtered

Question 20

What is Tubular Reabsorption?

Answer 20

The reabsorption of select substances that have already been filtered; Tubule to capillaries

Question 21

What is Tubular Secretion?

Answer 21

Things not filtered by glomerulus (sent to efferent arteriole), are secreted into the tubules

Question 22

What is the formula for figuring out the amount of solute excreted?

Answer 22

(Amount Filtered - Amount reabsorbed) + Amount Secreted

Question 23

What determines whether filtration occur?

Answer 23

The filtration barrier; if the substance is an ion or small protein it can then go through the barrier

• Water, ions, small molecules can go through
• RBCs, WBCs, Plasma Proteins cannot

Question 24

What property of the glomerulus allows for it to filter? What property of the Tubule allows for the substances to not leak through?

Answer 24

• The glomerulus capillary is composed of endothelial cells (easily allows things to pass)
• Epithelial cells which are what make the tubule make sure substances don’t slip out

Question 25

What are podocytes?

Answer 25

Found on the glomerular capillary, these are large spaces in between where filtration occurs

Question 26

Explain the movement of filtrate from the glomerular capillary to the bowman’s capsule

Answer 26

1. Filtrate moves through gaps between endothelial cells known as fenestrations
2. Moves through basement membrane
3. Goes through podocyte slits (surrounded around the glomerular capillary) and moves into the lumen of Bowman’s capsule

Question 27

When would we refer to the peritubular capillaries as the vasa recta?

Answer 27

In the renal medulla (Vasa Recta)
* Typically see this in juxtamedullary nephrons where the vasa recta is long and goes all the way down to the level of the renal medulla

Question 28

What does the pertibular capillary and vasa recta do that are the same but not in the same location?

Answer 28

They both provide nutrients but peritubular capillary is in the cortex region while the vasa recta is in the medulla region of the nephron