The Excretory (Urinary) System

Question 1

What is the purpose of the excretory system?

Answer 1

To filter and remove wastes from the body fluids of an organism.

Question 2

What is the function of the kidney, and what are its main layers?

Answer 2

The kidney filters blood to remove metabolic wastes and is composed of three main layers:

Cortex: The outer layer of connective tissue.
Medulla: Inside the cortex.
Renal Pelvis: Connected to the ureter.

Question 3

What is the medulla’s function in the kidney, and what is it composed of?

Answer 3

The medulla is the primary site of filtration in the kidney and is composed of smaller subunits called nephrons.

Question 4

How many nephrons are in a kidney?

Answer 4

A kidney contains about 1 million nephrons.

Question 5

What is the glomerulus and what is its function in the nephron?

Answer 5

The glomerulus is the first part of the nephron where blood plasma and its solutes flow into the Bowman’s capsule.

Question 6

What doesn’t normally pass from the glomerulus into the Bowman’s capsule?

Answer 6

Proteins, red blood cells (RBCs), and platelets.

Question 7

What path does the filtrate take after entering the Bowman’s capsule?

Answer 7

The filtrate passes through the proximal tubule, loop of Henle, distal tubule, collecting duct, then the ureter, and finally the bladder.

Question 8

Q: What happens at the proximal tubule of the nephron?

Answer 8

At the proximal tubule, HCO3-, NaCl, H2O, nutrients, and K+ are reabsorbed into capillaries, while H+ and NH3 move into the proximal tubule from capillaries.

Question 9

What happens at the descending and ascending loops of Henle?

Answer 9

At the descending loop of Henle, H2O is reabsorbed into capillaries. At the ascending loop of Henle, NaCl is reabsorbed into capillaries.

Question 10

What happens at the distal tubule of the nephron?

Answer 10

At the distal tubule, HCO3-, NaCl, and H2O are reabsorbed into capillaries, while H+ and K+ move into the distal tubule from capillaries.

Question 11

What happens at the collecting duct of the nephron?

Answer 11

At the collecting duct, NaCl, H2O, and some urea are reabsorbed into capillaries.

Question 12

what do capillaries do in the nephron?

Answer 12

Capillaries reabsorb anything the body needs from the nephron and secrete wastes back into it. Sometimes, small amounts of wastes, like urea, are unintentionally reabsorbed with water.

Question 13

Q: What waste molecules are secreted back into the nephron?

Answer 13

A: H+ (acids), excess minerals (e.g., Na+, K+), nitrogenous wastes (e.g., urea, creatinine, uric acid, ammonia), and drugs.

Question 14

What is Antidiuretic Hormone (ADH) and what does it do?

Answer 14

ADH, also known as vasopressin, is released by the pituitary gland (stimulated by the hypothalamus) and increases water reabsorption in the distal tubule and collecting duct.

Question 15

What additional effects does ADH have on the body, and when is it released?

Answer 15

ADH causes vasoconstriction, increasing blood pressure. It is released when blood pressure is low, or a person is dehydrated or sleeping.

Question 16

What do the juxtaglomerular cells release when they detect low blood flow or pressure?

Answer 16

They release the hormone renin.

Question 17

How is angiotensin I formed in the blood?

Answer 17

Renin converts angiotensinogen (made by the liver) into angiotensin I.

Question 18

How is angiotensin II formed, and what does it do?

Answer 18

ACE (angiotensin-converting enzyme) from the lungs converts angiotensin I into angiotensin II, which stimulates vasoconstriction and the release of ADH and aldosterone.

Question 19

What does aldosterone do in the nephron?

Answer 19

Aldosterone stimulates thirst and increases NaCl and water reabsorption in the nephron.

Question 20

What are kidney stones and what do they do?

Answer 20

Kidney stones are mineral solutes that precipitate into stones, tearing and damaging the kidney.

Question 21

What is diabetes mellitus and how does it affect the kidneys?

Answer 21

Diabetes mellitus is caused by low insulin levels, leading to high blood glucose. Over time, high glucose damages the renal tubules, reducing their ability to reabsorb water.

Question 22

How does high glucose concentration in the nephron filtrate affect water balance?

Answer 22

High glucose concentration shifts the osmotic balance, drawing water into the urine instead of being reabsorbed into the capillaries.

Question 23

What happens in diabetes insipidus?

Answer 23

In diabetes insipidus, damage to the ADH-producing cells or the connection between the hypothalamus and pituitary gland results in very little water reabsorption due to a lack of ADH.

Question 24

What is nephritis and what effects does it have on the kidneys?

Answer 24

Nephritis is inflammation of the kidney, leading to reduced glomerular blood flow, decreased urine production, passage of cells or proteins into urine, and retention of wastes.