1: Renal functions, basic processes, and anatomy

Question 1

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List 7 functions of the kidneys

Answer 1

• water and electrolyte balance
• acid base balance
• blood pressure and extracellular fluid volume regulation
• excretion of metabolic waste and foreign substances
• regulation of RBC production
• regulation of Vitamin D production and Ca, P balance
• gluconeogenesis (more prominent after prolonged fasting)

Question 2

List 3 metabolic waste products (uremic toxins) the kidneys excrete and name their origin

Answer 2

urea - from protein
creatinine - from muscle creatine
uric acid - from nucleic acid

Question 3

How does erythropoietin production differ between the adult and during embryonic development?

Answer 3

adult - produced by interstitial cells in the cortical interstitium near the border of the renal cortex and medulla
embryonic development - produced by the liver

Question 4

What cells produce erythropoietin?

Answer 4

Peritubular interstitial cells in the cortical interstitium at the border between the renal cortex and medulla

Question 5

What is the stimulus for erythropoietin production?

Answer 5

reduction in the partial pressure of O2 in the local environment of the secreting cells

Question 6

Why does erythropoietin production fall in CKD?

Answer 6

reduction in the renal metabolism - less oxygen consumption by cells - local PO2 will be higher - less stimulus for erythropoietin production and secretion

Question 7

What fraction of the fluid entering the glomerulus is transferred into the renal tubules

Answer 7

0.2 i.e., 1/5

Question 8

name the structures

Answer 8

Question 9

What are the interstitial cells of the kidneys and what do they produce?

Answer 9

fibroblasts and immune cells
collagen, proteogylcans, glycoproteins, cytokines

Question 10

How does the structuring of the cortex and medulla differ?

Answer 10

the tubules and capillaries in the cortex are arranged very randomly
the tubules and capillaries in the medulla are organized in parallel arrays

Question 11

Name these structures

Answer 11

Question 12

What part of the kidney does the proximal tubule lie in?

Answer 12

the convoluted proximal tubule lies within the cortes, while a short straight segment descends a short way into the outer medulla

Question 13

Where does the descending thin limb of the loop of Henle begin?

Answer 13

All descending thin loop of Henle limbs begin between the border of the outer and inner stripe of the outer medulla

Question 14

Describe the difference in location between long and short loops of Henle

Answer 14

• long loops reach into the inner medulla, any part of the ascending loop that is still within the inner medulla will remain thin
• all thick ascending limbs begin at the border of the inner and outer medulla
• short loops will not have a thin ascending portion

Question 15

Where does the loop of Henle end?

Answer 15

The final part of the thick ascending loop of Henle reaches into the macula densa - after which it turns into the distal convoluted tubule

Question 16

What are the parts of the collecting duct?

Answer 16

cortical collecting duct
outer medullary collecting duct
inner medullary collecting duct

Question 17

Explain how the types of cells differ between segments of the nephron

Answer 17

• up to the distal convoluted tubules each segment has their own specific epithelial cells
  at the distal convoluted tubules - has principal cells and intercalated cells
• the principal cells are section specfic between the convoluted tubules, connecting tubules, and collecting ducts
• the end of the medullary collecting duct only contains inner medullary collecting-duct cells

Question 18

Name the 3 parts of the juxtaglomerular apparatus (JGA)

Answer 18

1. Granular cells - differentiated smooth muscle cells in the walls of the afferent arteriole, contain granulaes with the hormone RENIN
2. Extraglomerular mesangial cells -
3. Macula densa cells - detectors of flow rate and composition of fluid within the end of the thick ascending loop of Henle

Regulates glomerular filtration rate, renal blood flow, and affects blood pressure

Question 19

Explain the defintion of filtration, secretion, reabsorption, and excretion by the kidneys

Answer 19

filtration - water and solutes leaving the vascular system and entering the Bownman’s space
secretion - substances transported into the tubular lumen from the epothelial cells
reabsorption - subtances moved from the lumen across the epithelium into the interstitium and then capillaries/blood
excretion - substances exiting the body

Question 20

What percentage of blood entering the glomerular capillaries is filtered versus goes to the efferent artioles?

Answer 20

20% (1/5) filtered
80% continues to the efferent arterioles

Question 21

List the 3 most important metabolic processes in the tubules

Answer 21

1. gluconeogenesis
2. ammonium synthesis from glutamine
3. bicarbonate production

Question 22

Give a brief overview of the function of each of these parts of the nephron:
- glomerulues
- proximal tubule
- loop of Henle
- distal tubule
- cortical collecting duct
- medullary collecting duct

Answer 22

• glomerulus - filtration
• proximal tubule - reabsorption of 2/3 of filtered water, Na, and Cl, reabsorption of all useful organic molecules (glucose, AAs, etc.), reabsoprtion of K, P, Ca, bicarbonate
• loop of Henle - reabsorption of 20% of filtered Na and 10% of filtered water –> makes luminal fluid more diluted, contains macula densa
• distal tubule - reabsorb 5% each of water and Na
• cortical and medullary collecting ducts + connecting tubules - water and Na reabsorption in response to ADH, angiotensin II, aldosterone
• medullary collecting duct acid abd base excretion, urea excretion

Question 23

Where are renal corpuscles located?

Answer 23

throughout the cortx