Unit 2: The Excretory System Flashcards
What are the jobs of the excretory system?
- Nitrogen waster
2. Maintenance of water levels, pH, salts and hormones in the blood
What is excretion?
Separating waster products from the body fluids and removing from the body
What is the nitrogen waste?
(Ammonia, urea, uric acid) from deaminating the amine group from amino acids must be removed
How does the excretory system maintain homeostasis?
Putting any unwanted substances into the urine
What are the parts of the excretory system?
Ureter
Bladder
Urethra
Kidneys
What is the ureter?
Uses peristalsis to push urine down the bladder
What is the bladder?
Stores it one with the help of sphincters that keep urine in until voluntary release
Approximately how much urine can an adult bladder hold?
600 mL makes the body lose bladder sphincter control
What is incontinence?
The constant loss of bladder control
What is the urethra?
Carries urine out of the body (in males, it also carries sperm)
What are the kidneys?
Receives blood from the renal arteries, filters it to remove unwanted substances and sends it back out the body through the renal vein (the unwanted substances then for urine) … Contains over 1 million filters called nephrons
What hormones does the kidney make?
Epo
Renin
Calcitrol
What is the first segment of a nephron?
Bowmans capsule: filtration
- a ball of capillaries (the glomerulus) allows most blood substances (some good and some bad) (water, glucose, ammonia, urea, vitamins) to leave the blood and enter the nephron due to high blood pressure in the capillaries pushing them … This filtrate then moves on through the nephron
What cannot be filtrated through the Bowmans capsule?
Protein, red blood cells and platelets stay in the blood as they are too large
What are the second and third segment of the nephron?
- Proximal tubule
- Loop of Henie
Reabsorption
- some of the filtrate is returned back to the blood
- glucose and vitamins are returned by active transport and then water follows by osmosis
What is the fourth segment of the nephron?
Distal tube: secretion
- controlled by hormones
- the blood secretes hydrogen and potassium ions and any antibiotics, electrolytes, and drugs present in order to maintain the pH of the blood
What is the fifth segment of the nephron?
Collecting duct: water Reabsorption
- controlled by hormones
- blood reabsorbs most remaining water, leaving very concentrated urine (containing some water, salt, urea, ammonia, creatinine) in the collecting duct, which will then empty into a ureter
What steps control water levels?
2, 3 and 5
Why steps of the nephron are controlled by hormones?
4 and 5
Explain the diagram of the excretory system…
Kidneys at the top … Ureter from kidneys to bladder … Bladder - roundish structure … Urethra from bladder to outside
How do the kidneys help control water balance of the body?
Antidiuretic hormone (ADH)
- made by the pituitary gland when blood is hypertonic or when blood volume is too low (called hypovolemia)
- promotes water reabsorption into the blood by making the walls of the collecting duct very permeable to water
- inhibited by alcohol and caffeine
- a 10% loss of water in body tissues = death
Describe the negative feedback loop for maintenance of water balance?
Sensor: hypothalamus
- senses blood is hypertonic
Control center: brain
Effector: pituitary gland
- releases ADH to cause water to leave the collecting duct and re enter the blood
Turns off
How do the kidneys help control salt balance?
- aldosterone is made the adrenal cortex when blood levels of sodium are too low (called hyponatremia)
- promotes sodium (Na+) Reabsorption into the blood by simulating the active transport pumps in the distal tubule
Describe the negative feedback loop for salt balance maintenance…
Sensor: hypothalamus senses blood salt level is too low (detects hyponatremia) and sends a signal to the control center: the brain, through a hormone signal … Renin
