Topic 5.2: Excretion

Question 1

Summarize the roles of the urinary system in the body.

Answer 1

-Excretion of metabolic wastes
-Osmoregulation
-Maintaining acid-base balance
-Secretion of hormones

Question 2

List an briefly describe the functions of the specific components of the urinary system.

Answer 2

1. The kidneys produce urine
2. Ureters transport the urine
3. Urinary bladder stores the urine
4. Urethra passes urine

Question 3

Explain why urinary system diseases may cause problems with the overall homeostasis of the body.

Answer 3

With kidney disease, wastes will build up, salt and pH balance will be disrupted, and hormon secretion of the kidneys will be changed, all of which would interfere with homeostasis.

Question 4

Define urinary system

Answer 4

Organ system of humans that includes the kidneys, urinary bladder, and associated structures; excretes metabolic wastes; maintains fluid balance; helps control pH.

Question 5

Define excretion

Answer 5

Elimination of metabolic wastes by an organism at exchange boundaries such as the plasma membrane of unicellular organisms and excretory tubules of multicellular animals.

Question 6

Define urine

Answer 6

Liquid waste product made by the nephrons of the vertebrate kidney through the processes of glomerular filtration, tubular reabsorption, and tubular secretion.

Question 7

Define ammonia

Answer 7

Nitrogenous end product that takes a limited amount of energy to produce but requires much water to excrete because it is toxic.

Question 8

Define uric acid

Answer 8

Main nitrogenous waste of insects, reptiles, and birds.

Question 9

Define gout

Answer 9

Condition caused by the inability of the urinary system to remove uric acid from the body.

Question 10

Define osmoregulation

Answer 10

Regulation of the water-salt balance to maintain a normal balance within internal fluids.

Question 11

Define erythropoietin (EPO)

Answer 11

Hormone produced by the kidneys that speeds red blood cell formation.

Question 12

Define kidneys

Answer 12

Paired organs of the vertebrate urinary system that regulate the chemical composition of the blood and produce a waste product called urine.

Question 13

Define ureter

Answer 13

Tubular structure conducting urine from the kidney to the urinary bladder.

Question 14

Define urinary bladder

Answer 14

Organ where urine is stored.

Question 15

Define urethra

Answer 15

Tubular structure that receives urine from the bladder and carries it to the outside of the body.

Question 16

Identify the parts of a nephron that are found in the renal cortex and the renal medulla.

Answer 16

The renal cortex contains the glomeruli, proximal convoluted tubules (PCTs), and distal convoluted tubules (DCTs). The renal medulla contains the loops of the nephron.

Question 17

Explain why the proximal convoluted tubule is more specialized for reabsorption than the distal convoluted tubule.

Answer 17

The epithelium of the PCT has many microvilli, which increase the surface area for reabsorption.
The DCT is composed of cuboidal epithelial cells that are not designed for reabsorption.

Question 18

Summarize how the kidney uses the processes of diffusion, passive transport, and active transport.

Answer 18

All of these processes involve the movement of a substance across biological membranes. Diffusion and passive transport are dependent on concentration; active transport is not, but it required energy. Active and passive transport usually requires carrier molecules.

Question 19

Explain where in the nephron, and by what process, glucose is normally returned from the glomerular filtrate to the blood.

Answer 19

Glucose is normally returned from the glomerular filtrate to the blood by reabsorption via carrier proteins at the proximal convoluted tubule.

Question 20

Define nephron

Answer 20

Microscopic kidney unit that regulates blood composition by glomerular filtration, tubular reabsorption, and tubular secretion.

Question 21

Define glomerulus

Answer 21

Capillary network within the glomerular capsule of a nephron.

Question 22

Define glomerular capsule

Answer 22

Cuplike structure that is the initial portion of a nephron.

Question 23

Define proximal convoluted tubule

Answer 23

Portion of a nephron following the glomerular capsule where tubular reabsorption of filtrate occurs.

Question 24

Define loop of the nephron

Answer 24

Portion of a nephron between the proximal and distal convoluted tubules; functions in water reabsorption.

Question 25

Define distal convoluted tubule

Answer 25

Final portion of a nephron that joins with a collecting duct; associated with tubular secretion.

Question 26

Define collecting duct

Answer 26

Duct within the kidney that receives fluid from several nephrons; the reabsorption of water occurs here.

Question 27

Define glomerular filtration

Answer 27

Movement of small molecules from the glomerulus into the glomerular capsule due to the action of blood pressure.

Question 28

Define tubular reabsorption

Answer 28

Movement of primarily nutrient molecules and water from the contents of the nephron into blood at the proximal convoluted tubule.

Question 29

Define tubular secretion

Answer 29

Movement of certain molecules from blood into the distal convoluted tubule of a nephron so that they are added to urine.

Question 30

Describe the three processes required for the excretion of a hypertonic urine.

Answer 30

Reabsorption of salt, establishment of a solute gradient, reabsorption of water.

Question 31

Summarize the relationship between aldosterone, the juxtaglomerular apparatus, and renin.

Answer 31

When blood volume and pressure is low, the juxtaglomerular apparatus secretes renin, which converts angiotensin I, which is then converted to angiotensin II that causes aldosterone secretion.

Question 32

Describe how diuretic interacts with the urinary system.

Answer 32

Diuretics can inhibit secretion of ADH, increase the glomerular filtration rate, decrease the tubular reabsorption of sodium, or inhibit active transport of sodium at the loop of the nephron or at the DCT.

Question 33

Explain the ions that the kidneys control to maintain blood pH homeostasis.

Answer 33

Kidneys regulate H+, HCO3-, OH-, and NH4+ to maintain blood pH 7.4.

Question 34

2. _______ is the elimination of metabolic waste, and _______ is the elimination of indigested food.
   a) excretion, absorption
   b) excretion, defecation
   c) defecation, excretion
   d) none of the above

Answer 34

b) excretion, defecation

Question 35

Urea is the by-product of _________ metabolism.
a) glucose
b) salt
c) fat
d) amino acid

Answer 35

d) amino acid

Question 36

Which of the following materials would not be filtered from the blood at the glomerulus?
a) water
b) urea
c) protein
d) glucose
e) sodium ions

Answer 36

c) protein

Question 37

_______ reabsorption from the nephrons is ordinarily 100%
a) sodium
b) glucose
c) water
d) urea

Answer 37

b) glucose

Question 38

The purpose of the loop of the nephron in the process of urine formation is
a) reabsorption of water
b) glucose
c) production of filtrate
d) secretion of solutes

Answer 38

a) reabsorption of water

Question 39

8. Kidneys control blood pH by excreting
   a) HCO3-
   b) H+
   c) NH3
   d) CO2

Answer 39

b) H+

Question 40

Which of these associations is mismatched?
a) atrial natriuretic hormone (ANH)- secreted by the heart
b) renin-secreted by the anterior pituitary
d) aldosterone- secreted by the adrenal cortex
d) antidiuretic hormone (ADH)- secreted by the posterior pituitary

Answer 40

b) renin-secreted by the anterior pituitary

Question 41

Which hormone causes a rise in blood pressure?
a) aldosterone
b) oxytocin
c) erythropoietic
d) atrial natriuretic hormone

Answer 41

a) aldosterone

Question 42

High blood pressure often is accompanied by kidney damage. In some people, the kidney damage is subsequent to the high blood pressure, but in others the kidney damage is what caused the high blood pressure. Explain how a low salt diet would enable you to determine whether the high blood pressure or the kidney damage came first?

Answer 42

If one is not eating large amounts of salt, the the regulation of sodium levels in the blood and the symptom of high blood pressure would be dependent on kidney function rather than diet. If the release of aldosterone is being successfully regulated by the kidney’s release of renin, then blood pressure should be under control.

Question 43

The renin-angiotensin-aldosterone system can be inhibited in order to reduce high blood pressure. Usually, the angiotensin-converting enzyme, which converts angiotensin I to angiotensin II, is inhibited by drug therapy. Why would this enzyme be an effective point to disrupt the system?