UNIT 3: The Human Urinary System

Question 1

kidneys

Answer 1

filter the blood taking out the waste products of metabolism such as urea.

Question 2

ureters

Answer 2

carry urine from the kidney to the urinary bladder

Question 3

urinary bladder

Answer 3

stores urine

Question 4

urethra

Answer 4

carries urine outside of the body

Question 5

functions of the kidney: excretion

Answer 5

the main function of the kidney is to filter the blood taking out waste products producing urine.

Question 6

functions of the kidney: osmoregulation

Answer 6

the kidneys control the amount of water in the body. If there is too much water in the body, the kidneys will excrete the excess water an, if there is not enough, the kidneys will excrete much less water in an effort to conserve the remaining water in the body.

Question 7

functions of the kidney: pH control

Answer 7

the kidneys can control the acidity and alkalinity of the blood by excreting or conserving hydrogen ions

Question 8

functions of the kidney: hormone production

Answer 8

the kidneys produce the hormone erythropoietin (EPO). EPO stimulates the bone marrow to produce red blood cells (erythrocytes).

Question 9

urine production: filtration

Answer 9

Means that water and small molecules pass under high pressure from the blood into the nephron.

• occurs from the glomerulus into Bowman’s capsule.
• blood enters the glomerulus from the afferent arteriole.
• blood is under high pressure in the glomerulus and substances such as water, urea, salts, glucose and amino acids pass through.
• the liquid that passes through is called the glomerular filtrate.

Question 10

urine production: reabsorption

Answer 10

Molecules pass from the nephron back into the blood

• useful substances such as glucose and amino acids in the glomerular filtrate pass back into the blood stream.
• water is reabsorbed in the proximal convoluted tubule, descending loop of henle, the distal convoluted tubule and the collecting duct.
• all the glucose and amino acids are reabsorbed in the proximal convoluted tubule.
• salts are reabsorbed in the proximal convoluted tubule, the ascending loop of henle and the distal convoluted tubule.

Question 11

urine production: secretion

Answer 11

Some substances pass from the blood into the nephron.

• certain substances pass into the tubules of the nephron from the bloodstream by active transport.
• drugs and poisons are actively transported out of the bloodstream into the proximal and distal convoluted tubules.

Question 12

urination (micturition)

Answer 12

the passing of urine from the body

Question 13

the nephron

Answer 13

the functional unit of the kidney.
there are approx. 1000000 nephrons in each kidney.
composed of:
1. bowmans capsule: where filtration occurs.
2. proximal convoluted tubule: where most the re-absorption occurs.
3. loop of henle: where more re-absorption occurs.
4. distal convoluted tubule: where reabsorption of water and secretion of drugs and hydrogen ions occurs.

Question 14

blood supply

Answer 14

• the nephron receives blood from the renal arterioles.
• the renal arterioles carry blood to afferent arterioles.
• each afferent arteriole enter the bowmans capsule.
• the ‘ball’ of blood vessels within the bowman’s capsule = glomerulus.
• the blood is then carried away from the bowman’s capsule via the efferent arteriole.
• this blood is then circulated around the nephron for reabsorption of useful substances.
• the afferent arteriole is slightly wider than the efferent which causes an increased blood pressure in the glomerulus. this increased blood pressure helps with the process of filtration in the bowmans capsule.

Question 15

glomerulus and bowman’s capsule are adapted to carry out their functions by having the following characteristics:

Answer 15

• the bowman’s capsule is cup-shaped to provide maximum surface area for filtration.
• the endothelium of the bowman’s capsule is only 1 cell thick.
• the capillary walls of the glomerulus are one cell thick and more leaky than normal capillaries.

Question 16

kidney failure

Answer 16

• occasionally the nephrons of the kidney might not work properly and kidney failure may result.
• patients with total kidney failure have to undergo dialysis.
• dialysis is where a machine takes blood from the body and removes wastes and excess water from the blood before returning it to the body.
• in the long term, kidney failure patients usually receive a kidney transplant.

Question 17

osmoregulation: too much water in the body

Answer 17

the brain detects the amount of water in the body. If it is too high, the pituitary stops secreting the hormone anti-diuretic hormone (ADH). This travels in the bloodstream to the distal convoluted tubules and collecting ducts of the kidney and causes them to become less permeable and therefore, more water is excreted.

Question 18

osmoregulation: too little water in the body

Answer 18

the brain detects a reduced amount of water in the body and causes the pituitary to release ADH that travels in the bloodstream to the distal convoluted tubules and collecting ducts and causes them to become more permeable. Water is then reabsorbed into the blood and less is excreted in the urine.

Question 19

Ectotherms

Answer 19

Gain or lose heat from or to their external environment

Question 20

Endotherms

Answer 20

Generate their own heat from metabolic reactions

Question 21

Active transport

Answer 21

Energy in the form of ATP is used to move molecules, often against a concentration gradient