Exam 3: Lecture 35

Question 1

Which hormone influences the kidneys and their regulation of phosphate?

Answer 1

Parathyroid hormone

Question 2

Phosphate is the most dense where in the body?

Answer 2

Bone matrix

Question 3

T/F: Majority of plasma phosphate is not filtered.

Answer 3

False - 90% is filtered

Question 4

Where is about 15% of filtered phosphate reabsorbed?

Answer 4

Proximal straight tubule

Question 5

What is the importance of the phosphate that is excreted?

Answer 5

it is important for acid buffering

Question 6

About how much filtered phosphate is excreted?

Answer 6

15%

Question 7

How does PTH regulate the reabsorption of phosphate in the PT?

Answer 7

Inhibiting Na+/phosphate co-transport

Question 8

What macromolecule induces negative phosphate balance directly by inhibiting renal phosphate reabsorption in PT?

Answer 8

Phosphatonins

Question 9

What is the most important phosphate-regulating substance?

Answer 9

Fibroblast growth factor 23 (FGF-23)

Question 10

What causes the secretion of FGF-23 from osteocytes?

Answer 10

Elevated calcitriol

Question 11

What are the two ways that FGF-23 acts on the kidneys?

Answer 11

• decreases Na/phosphate co-transporter
• suppresses 1-alpha-hydroxylase

Question 12

What is the end result of FGF-23 effects on the kidneys?

Answer 12

Phosphaturia

Question 13

Where is the most amount of filterable Ca located?

Answer 13

Bound to plasma proteins

Question 14

What three systems in the body help to regulate Ca?

Answer 14

Bone, GIT, and kidneys

Question 15

What regulates Ca absorption in the intestine?

Answer 15

Vitamin D

Question 16

Where in the kidney does PTH stimulate Ca reabsorption?

Answer 16

Distal convoluted tubule

Question 17

T/F: Ca reabsorption is inversely related to Na reabsorption.

Answer 17

False - Ca and Na reabsorption is tightly coupled together in the PT and Loop of Henle

Question 18

Where is about 25% of filtered Ca reabsorbed?

Answer 18

Thick ascending limb

Question 19

Which nephron segment is the only place where Ca reabsorption is not coupled with Na reabsorption?

Answer 19

Early distal tubule

Question 20

What is the effect of thiazide diuretics on Ca?

Answer 20

Increase absorption

Question 21

About how much Mg is filterable?

Answer 21

80%

Question 22

How much filtered Mg is reabsorbed in the PT?

Answer 22

30%

Question 23

How much filtered Mg is reabsorbed in the TAL?

Answer 23

60%

Question 24

How much filtered Mg reabsorbed in the DT?

Answer 24

5%

Question 25

Where is the major site of Mg reabsorption?

Answer 25

Thick ascending limb