Homeostasis - Renal Structure and Function

Question 1

Cortex

Answer 1

Superficial region of kidney. Produces erythropoietin. Receives most of blood flow and primarily concerned with reabsorbing filtered material. Contains 1 million nephrons.

Question 2

Medulla

Answer 2

Deep to cortex. Highly metabolically active area which serves to concentrate urine. No arteries.

Question 3

Renal pyramids

Answer 3

Made up of loops of Henle and collecting tubules. Broad base towards cortex and apex (papilla) towards pelvis. Separated by renal columns.

Question 4

Renal pelvis

Answer 4

Funnel-shaped tube continuous with ureter. Made up of smaller calyces which receive fluid from papillae of renal pyramid. Collects urine for excretion.

Question 5

Renal interstitium

Answer 5

Peri-tubule and peri-arterial space. Builds up high osmolality for reabsorption. Contains fibroblasts and macrophages for support.

Question 6

Afferent arterioles

Answer 6

Arise from cortical radial arteries to supply glomerulus.

Question 7

Efferent arterioles

Answer 7

Leave glomerulus to form the peritubular capillaries.

Question 8

Bowman’s capsule

Answer 8

Part of renal corpuscle. Consists of visceral layer of podocytes closely applied to glomerulus and an outer parietal layer.

Question 9

Glomerulus

Answer 9

Bundle of specialized capillaries. Site of renal filtration.

Question 10

Juxtaglomerular apparatus (JGA)

Answer 10

Juxtaglomerular cells of afferent arteriole and macula densa of distal tubule. Structure initiates renin-angiotensin mechanism to elevate blood pressure and increase sodium retention.

Question 11

Convuluted tubule

Answer 11

Long unbranching tube where urine is produced.

Question 12

Proximal tubule

Answer 12

Receives ultrafiltrate from bowman capsule. 50-60% of solute and water reabsorbed.

Question 13

Distal tubule

Answer 13

Reabsorbs sodium, bicarb and secretes ammonia.

Question 14

Ascending loop of Henle

Answer 14

Impermeable to water, reabsorbs salt

Question 15

Descending loop of Henle

Answer 15

Impermeable to sodium, reabsorbs water

Question 16

Collecting duct

Answer 16

Water reaborbs via aquaporins regulated by ADH (as well as urea reabsorb). Aldosterone regulates by reabsorb sodium and secrete potassium. pH regulation by bicarb/hydrogen reabsorb and/or secretion.

Question 17

Describe major excretory functions of kidney

Answer 17

Excretion of waste products (urea, uric acid, creatinine, bilirubin), hormones, drugs and their byproducts. Clearance - related to function (creatinine clearance).

Question 18

Describe major non-excretory functions of kidney

Answer 18

Regulation of salt content of extracellular fluid, salt concentration of body, potassium homeostasis, acid-base balance, mineral-bone metabolism, and endocrine gland.

Question 19

Describe glomerular filtration

Answer 19

First step in urine formation. Small molecules are able to pass through glomerular capillaries.

Question 20

Tubular reabsorption and secretion

Answer 20

Only a small percentage of glomerular filtrate leaves body. Most is reabsorbed. Secretion is addition of substances to tubular filtrate.

Question 21

Describe assessment of GFR

Answer 21

Describes flow rate in which filtered fluid runs through the kidney. Gauges how well kidneys are functioning and removing excess wastes and fluids. Involves creatinine levels. Clinically useful in determining progression or improvement of chronic kidney disease.

Question 22

Describe normal daily water intake and output

Answer 22

Water output is about 2-3 liters per day. Includes: urine, feces, inactive perspiration, respiration. About 2.5 liters need to be taken in orally while remaining is contributed by metabolic water.

Question 23

Thirst mechanism: renal hypotension

Answer 23

Activate renin-angiotensin system. Angiotensin II acts on brain to stimulate thirst.

Question 24

Thirst mechanism: general hypotension

Answer 24

Baroreceptors in aorta and carotid artery cause hypothalmus to release ADH

Question 25

Thirst mechanism: Hyperosmolarity

Answer 25

Chemoreceptors in hypothalmus cause release of ADH. This concentrates urine and increases thirst.

Question 26

Describe third spacing

Answer 26

Fluid collection somewhere it’s not supposed to. First two “spaces” are intracellular and extracellular (vascular, interstitial). Ascites is an example of fluid being where it should not; in the peritoneum. Edema is just an excessive fluid buildup, not third spacing.

Question 27

Osmosis

Answer 27

Net diffusion of water across a membrane from a region of high water concentration to one that has a lower water concentration.

Question 28

Osmolarity

Answer 28

How much solute is in a solution.

Question 29

Tonicity

Answer 29

Relative concentration of solutions that determine direction and extent of diffusion.

Question 30

Isotonic

Answer 30

Osmolarity equal in and out of cell.

Question 31

Hyperosmotic

Answer 31

Solution has higher osmolarity outside of cell that inside; cell shrinks.

Question 32

Hypoosmotic

Answer 32

Solution has lower osmolarity outside of cell than inside; cell swells.

Question 33

Distribution of salt and water in human body

Answer 33

Sodium is primary extracellular cation. Extracellular spaces contain 90% of sodium in body. Water follows sodium through principle of osmosis.

Question 34

Describe general process of volume homeostasis

Answer 34

Sodium increase in blood results in kidneys excreting sodium to avoid cell shrinkage.
Sodium decrease in blood results in kidneys excreting water to retain sodium.