Lecture 1

Question 1

Location of kidneys

Answer 1

Kidney is posterior to the perineum and partially protected by the 11-12th rib.

Question 2

What are the different functions of the kidneys?

Answer 2

1. Blood ionic composition 2. Blood pH 3. Blood volume and pressure 4. Blood osmolarity 5. Key role in exertion of waste products 6. Hormone production 7. Balance of glucose levels.

Question 3

Why is the regulation of body fluid volume important?

Answer 3

Regulation of body fluid volume is important for homeostasis; if not controlled, it can lead to irregularities.

Question 4

What are the effects of too little fluid?

Answer 4

Symptoms include thirst, confusion, low JVP, weight loss, reduced skin turgor, and decreased urine output.

Question 5

What are the effects of too much fluid?

Answer 5

Symptoms include ankle swelling and breathlessness; signs include raised JVP (jugular venous pressure) and weight gain.

Question 6

How does the regulation of fluid balance occur?

Answer 6

The kidneys balance plasma, managing the movement of Na, as water should follow.

Question 7

What is osmolarity?

Answer 7

Measurement of solute concentration or osmotically active solutes within a fluid, measured in osmoles (osmol/L).

Question 8

What is osmolality determined by?

Answer 8

Osmolality is a more accurate measurement of volume, as volume can change with temperature (osmol/kg).

Question 9

What is osmotic pressure?

Answer 9

Pressure applied to a solution to prevent inward movement of fluid across a semi-permeable membrane; higher osmolarity results in higher osmotic pressure.

Question 10

What is oncotic pressure?

Answer 10

The osmotic pressure exerted by proteins in the blood that pulls water into that compartment.

Question 11

What is hydrostatic pressure?

Answer 11

The force exerted by a fluid against a capillary wall; for example, a pipe forced at one end causes water to accumulate, creating high hydrostatic pressure if a hole is opened.

Question 12

What is tonicity?

Answer 12

The ability of a surrounding solution to cause a cell to gain or lose water.

Question 13

What is a hypo-osmotic solution?

Answer 13

<300 mOsm/L of solute; low osmotic pressure outside the cell and high osmotic pressure inside.

Question 14

What is an iso-osmotic solution?

Answer 14

300 mOsm/L of solute; high osmotic pressure inside and outside of the cell.

Question 15

What is a hyper-osmotic solution?

Answer 15

> 300 mOsm/L of solute; very high osmotic pressure outside the cell and high osmotic pressure inside the cell.

Question 16

What is the basic structure of the kidney?

Answer 16

Contains an outer cortex and an inner medulla; each kidney has a hilum with a renal artery, renal vein, and ureter.

Question 17

How does the production of urine occur?

Answer 17

1. Collecting duct 2. Minor calyx 3. Major calyx 4. Renal pelvis 5. Ureter 6. Bladder.

Question 18

What is the structure and function of a nephron?

Answer 18

Makes urine by removing waste and excess substances from the blood; consists of the renal corpuscle (Bowman’s capsule/glomerulus) and the renal tubule (PCT, loop of Henle, DCT).

Question 19

What is the juxtamedullary nephron and the flow of fluid?

Answer 19

A nephron with its loop of Henle extending deep into the renal medulla; fluid flows through the descending limb, thin ascending limb, and thick ascending limb of the nephron loop.

Question 20

What is the function of the juxtamedullary nephron?

Answer 20

Filtration, tubular reabsorption, tubular secretion, and micturition.

Question 21

What is the juxtaglomerular apparatus?

Answer 21

A system that regulates the rate of filtrate formation and systemic blood pressure, comprised of macula densa cells, extraglomerular mesangial cells, and granular cells of the afferent arteriole.

Question 22

What is the function of macula densa cells?

Answer 22

Contain chemoreceptors that test for solute concentration in the fluid.

Question 23

What is the function of granular cells of the afferent arteriole?

Answer 23

Acts as mechanoreceptors that detect pressure in the vasculature and release renin in response to low sodium.

Question 24

What are the different cell types in Bowman’s capsule?

Answer 24

1. Mesangial cells for constriction and relaxation
2. Fenestrations of the glomerular endothelial cell prevent filtration of RBC but allow plasma components
3. Basal lamina prevents filtration of larger proteins
4. Slit membrane between pedicels prevents filtration of medium-sized proteins.

Question 25

Why does filtration occur in a greater extent in the renal corpuscle?

Answer 25

Larger surface area of glomerular capillaries, thin and fenestrated endothelial membrane, and higher blood pressure due to the difference in diameter of afferent and efferent arterioles.

Question 26

What is net filtration pressure?

Answer 26

10 mmHg.

Question 27

What is glomerular filtration rate?

Answer 27

The amount of filtrate formed by all renal corpuscles of both kidneys per minute.

Question 28

How does the control of GFR occur?

Answer 28

1. Through adjustment of blood flow into and out of the glomerulus 2. Alteration of glomerular capillary surface area.

Question 29

What are the mechanisms of controlling GFR?

Answer 29

Reno-autoregulation, consisting of myogenic and tubuloglomerular responses.

Question 30

What does the myogenic response consist of?

Answer 30

Increase in BP and GFR leads to stretching of arterioles, causing JG smooth muscle fibers to contract and narrow the lumen of the afferent arteriole, decreasing renal blood flow.

Question 31

What does the tubuloglomerular response consist of?

Answer 31

Negative feedback regulation via macula densa cells; increased flow of filtrate leads to decreased reabsorption of ions and water, sensed by the JGA, causing afferent arterioles to constrict.

Question 32

What substances are filtered/reabsorbed and excreted?

Answer 32

Water is filtered, with more reabsorbed than excreted (e.g., 178-179L reabsorbed, 1-2L excreted). Proteins are filtered with more reabsorbed than excreted (e.g., 2.0g filtered, 1.9g reabsorbed, 0.1g excreted). Creatinine is filtered with more excreted than reabsorbed (e.g., 1.6g filtered, 0g reabsorbed).