Excretion and kidney function

Question 1

what is excretion?

Answer 1

the process of separating wastes from body fluids and eliminating them from the body.

Question 2

What are the organs that partake in the process of excretion?

Answer 2

Lungs- releases CO2 and water vapour

Skin- releases sweat to remove heat (temperature regulation)
,sweat glands also release small amounts of mineral salts

Liver- detoxifies harmful materials such as poisons or drugs (e.g. alcohol); breaks down old red blood cells; deaminates excess amino acids; excess amino acids converted to carbohydrates (that can be used for energy or stored) and nitrogenous wastes

colon- removes undigested material from digestive system (not considered excretion)
; removes metabolic wastes from the liver (egested with feces)

Kidneys- filter waste from the blood, which is excreted in urine
; adjusts the concentrations of salts and water in the blood

Question 3

What are nitrogenous wastes and what can be produced by certain animals?

Answer 3

-are the toxic byproducts of deamination (the removal of the amino group of amino acids)
- fish produce ammonia; insects and reptiles produce uric acid; mammals produce urea

Question 4

How does blood flow through the excretory system?

Answer 4

1. blood travels into the kidneys through renal arteries
2. blood is filtered in the kidneys to form urine
3. filtered blood is returned to vena cava through renal veins

Question 5

What happens to the newly formed urine after filtered blood is returned?

Answer 5

urine travels to the bladder through ureters
urine is removed from the bladder by the urethra

Question 6

What do the kidneys use to filtrate blood/urine?

Answer 6

the kidneys contain a million filtration units called nephrons

the top of each nephron is located in the outer portion of the kidney (the cortex), and the base of each nephron is located in the medulla

urine drains into the renal pelvis before traveling to the bladder through the ureter

Question 7

How does urinalysis work?

Answer 7

The presence of certain molecules in urine is used to determine health
–> For example: glucose in urine can indicate diabetes; alcohol in urine can indicate alcoholism or liver damage; bacteria in urine can indicate a urinary tract infection; human chorionic gonadotropin hormone can indicate pregnancy

Question 8

what is a nephron?

Answer 8

microscopic tube-like filtration units found in the kidneys that filter and reabsorb various substances from the blood to produce urine.

Question 9

what are the goals/steps of the kidney/formation of urine?

Answer 9

Filtration of blood (600 mL/min)

Reabsorption (water, glucose, amino acids, salt, minerals)
595 of 600 mL is reabsorbed

Secretion (H+ ions, drugs)

This all occurs in the nephron (one million in each kidney).

Question 10

Describe filtration?

Answer 10

blood travels into each nephron through an afferent arteriole
blood reaches the glomerulus (a small cluster of capillaries)
in the glomerulus, pressure forces plasma into Bowman’s capsule
unfiltered blood continues through the efferent arteriole to the capillary network surrounding the nephron
the filtered plasma (called filtrate) travels through the tubule

Question 11

Difference between afferent and efferent arterioles?

Answer 11

Afferent brings blood to the kidneys (glomerulus) for the purpose of regulating blood flow and filtering any wastes, efferent takes blood out of the kidney/glomerulus and splits into the multiple different capillaries around the loop of Henle.

Question 12

What is urine?

Answer 12

filtrate of the nephron upon leaving the collecting ducts; exits the body through the urethra

Question 13

what are the function the excretory system?

Answer 13

Excretion of Metabolic Wastes: nitrogenous-containing wastes

maintenance of water-salt balance: maintenance of water and salt in blood as blood volume is closely tired to the salt balance of the body.
–> by regulating salt in blood, the kidneys are also involved in regulating blood pressure/maintaining levels of k+, bicarbonate, and calcium

maintenance of acid-base balance: help keep blood pH at 7.4 by excreting H+ and reabsorbing bicarbonate, urine is slightly acidic due to our nature to eat more acidic food.

secretion of hormones: erythropoietin and calcitriol.
–> e stimulates red blood cell production. and is released in response to increased oxygen demand or reduced oxygen carrying capacity of blood

Question 14

what are ureters?

Answer 14

a pair of muscular tubes that carry urine from the kidneys to the bladder

Question 15

what are the kidneys?

Answer 15

one of a pair of organs that filters waste from the blood (which is excreted as urine) and adjusts the concentration of salts in the blood

Question 16

what is the urinary bladder

Answer 16

organ where urine is stored before being discharged by way of urethra

Question 17

what are the renal artery and vein?

Answer 17

renal artery; enters the kidney through the concave side, and originates from the aorta; delivers blood to the kidneys and splits into a fine network of capillaries (glomerulus) within the bowman’s capsule of nephron

renal vein: blood vessel that drains from the kidney; returns to the body the solutes and water reabsorbed by the kidney

Question 18

what are the three regions of the kidney?

Answer 18

Renal cortex: outer layer of kidney

Renal medulla: an inner layer that the renal cortex dips down into

Renal pelvis: central space or cavity that is continuous within the ureter

Question 19

what is the nephron

Answer 19

microscopic tube-like filtration unit found in the kidneys that filters and reabsorbs various substances from the blood; produces urine

Question 20

How much water is initially brought back to the blood/blood vessels through the proximal tubule?

Answer 20

70%

Question 21

describe the step of filtration in urine creation

Answer 21

-blood travels into each nephron through an afferent arteriole
-blood reaches the glomerulus (a small cluster of capillaries)
-in the glomerulus, pressure forces plasma into Bowman’s capsule
-unfiltered blood continues through the efferent arteriole to the capillary network surrounding the nephron
-the filtered plasma (called filtrate) travels through the tubule

Question 22

describe the step of reabsorption in urine creation

Answer 22

-water is reabsorbed by passive transport from the filtrate back into the blood; this occurs in the proximal tubule (where 70% of water is reabsorbed), descending loop of Henle, distal tubule, and collecting duct.
-glucose, amino acids, and minerals (Ca, Mg, K, NaCl) are reabsorbed by active transport from the filtrate back into the blood; this occurs in the proximal tubule
-the active transport of salt out of filtrate in the ascending loop of Henle creates a concentration gradient in the medulla which allows for the reabsorption of water

Question 23

Describe the step of secretion in urine production

Answer 23

the secretion of ions into filtrate (H+ and HCO3-) maintains the pH of blood and filtrate; this occurs in the proximal tubule and distal tubule

Question 24

why is a protein not in urine

Answer 24

proteins are simply too large to travel through the glomerulus/filter through it. instead, it stays with the red blood cells in blood vessels

Question 25

describe the step of the regulation of water balance in urine production

Answer 25

-blood pressure is affected by the volume of water in the blood and the quantity of dissolved solutes in blood (osmotic pressure)
-the pituitary produces antidiuretic hormone (ADH, also called vasopressin) that causes more water to be reabsorbed by kidneys, thus increasing blood volume and blood pressure
-when the pituitary produces less ADH, less water is reabsorbed and more water is released in urine; blood volume and blood pressure decreases

Question 26

what are diuretics?

Answer 26

Diuretics are a class of drugs that increase urine output by promoting the excretion of excess water and electrolytes from the body.
–> caffeine and alcohol (diuretics) prevent the action of ADH; more urine is produced; dehydration occurs