Excretory System Flashcards
What is excretion?
The process by which the body ride itself of metabolic wastes
What are the major contributors of the excretory system and their roles?
- The lungs eliminate carbon dioxide
- The large intestine eliminates toxic digestive wastes
- The liver changes toxic and products of protein metabolism into soluble compounds that the kidney can collect and eliminate
What is the process that converts protein to carbohydrates?
Deamination
How does deamination produce a carbohydrate and ammonia (a toxic gas)?
The removal of an amino group from amino acids
What is produced when two molecules of toxic ammonia react with carbon dioxide?
Urea
How many times less toxic is urea than ammonia?
About 100,000x
What can be done with urea?
Can be safely transported through the bloodstream
What are nucleus acids broken down into?
Uric acid
What can excess uric acid cause?
Kidney stones or gout
What are the 4 roles of the kidneys?
- Removal of poisonous nitrogenous wastes
- Maintenance of blood pH
- Maintenance of water balance
- Maintenance of blood pressure
- Removal of poisonous nitrogenous wastes
What is blood carried to the kidneys from?
Renal arteries (branch off the aorta)
How much blood can the kidneys hold?
As much as 25% of the entire blood supply
Where are wastes taken to after being filtered by the kidneys?
The urinary bladder via the ureters
What is the muscle at the base of the urinary bladder that acts as a valve?
The sphincter muscle
When the sphincter muscle relaxes, where is stored urine released?
Through the urethra
When the bladder is about 200mL full of urine, what happens?
The signal to urinate is relayed to the brain
What are the three major structures of the kidney?
- The cortex
- The medulla
- The renal pelvis
What are ureters?
Tubes that conduct urine from the kidneys to the bladder
What does the renal artery do?
Delivers blood back to the kidney (dirty blood)
What does the renal vein do?
Sends blood back to the body (clean blood)
What are renal calyces?
Outer extensions of the renal pelvis that filter blood
What is the cortex?
Outer layer of connective tissue
What is the medulla?
Inner layer beneath the cortex, hold the major part of the nephron
What is the renal pelvis?
Hollow chamber that joins the kidney with the ureter
What is the functional unit of the kidney?
The nephron
How many nephrons are there?
About one million
What are nephrons (generic)?
Slender tubules
What supplies blood to nephrons (branch from the renal artery)?
Afferent arterioles
What do afferent arterioles lead into?
A high pressure capillary bed; the glomerulus
What occurs in the glomerulus?
Filtration
What does blood leave the glomerulus through?
Efferent arterioles
Where is blood carried to from the efferent arterioles?
A capillary network (2nd set of capillaries); the peritubular capillaries
What do peritubular capillaries wrap around?
The kidney tubule
Where is blood transferred to from the peritubular capillaries?
The renal vein
Where is blood transferred to from the renal vein?
The venous blood system (veins)
What is another name for the filtrate pathway?
Urine pathway
What is the glomerulus surrounded by?
Bowman’s capsule; a cup-like portion of the nephron
What does the cortex contain?
Bowman’s capsule, afferent and efferent arterioles
Where do fluids that are to be processed into urine enter?
Bowman’s capsule from the glomerulus
Where so fluids move after Bowman’s capsule?
- The proximal tubule (loop of henle)
- Distal tubule
- Collecting duct
What does the collecting duct do?
Collects urine from many different nephrons and merges into the renal pelvis
What three things does the formation of urine depend on?
- Filtration
- Re-absorption
- Secretion
How is filtration accomplished/steps of filtration?
- Through the movement of fluid into Bowman’s capsule
- Afferent arteriole carries blood to the glomerulus (small dissolved solutes and water pass into Bowman’s capsule)
What allows only some substances to filtered in the Bowman’s capsule?
Pressure gradient (low pressure in B.c.)
What are too big to pass through Bowman’s capsule?
Plasma proteins, RBC’s, WBC’s, and platelets
What is the “back-up” to filtration?
Re-absorption
What does re-absorption involve?
The transfer of essential solutes and water from the nephron back into the blood
Why is re-absorption so important?
Very important in maintaining the body’s water balance
Where does re-absorption occur?
Mostly in the proximal tubule, with some in the distal tubule (minor solutes)
Where does most water re-absorption occur?
The descending limb of the loop of henle
What are most substances re-absorbed through?
Passive diffusion
What is actively transported out of the nephron?
Na+; sodium
What follow sodium by charge attraction?
Cl- and HCO3-
What might also diffuse out but will be re-absorbed later, creating the need for secretion?
Urea and uric acid
Re-absorption occurs until when?
A threshold level of a substance is reached
What will not be re-absorbed into the blood, instead being excreted in the urine?
Excess amounts of glucose and salts
When is the only time particles move back into the blood stream?
If they are low in concentration
When will particles stop moving back?
When threshold/equilibrium is met
What is the “back-up” to re-absorption (backup to the backup)?
Secretion
What does tubular secretion involve?
The movement of materials from the blood back into the nephron
How are nitrogenous wastes, histamines, excess H+, minerals, drugs, penicillin, etc. removed from the body?
By the cells in the distal tubule
How do cells in the distal tubule remove these substances?
Actively transport these substances back to the nephron
What does the distal tubule contain in order to maintain this high energy demand?
Lots of mitochondria
What does ADH stand for?
Anti-Diuretic Hormone
What does ADH do?
Helps regulate the osmotic pressure of body fluids
How does ADH regulate osmotic pressure?
Causes the kidneys to increase water re-absorption
What does the increased water re-absorption do?
Produces more concentrated urine
What does ADH do to the distal tubules?
Makes them more permeable to the last 15% of water that can be re-absorbed into the blood
How can you tell ADH has been released in your body?
Your urine is in low volume and is highly concentrated (dark yellow)
What detect changes in osmotic pressure of the blood?
Osmoreceptors
What do osmoreceptors do control?
They stimulate or inhibit the secretion of ADH
What response do osmoreceptors elicit?
Thirst response, inspire you to increase fluid consumption
Where are osmoreceptors located?
The hypothalamus in the brain
What substances decrease the release of ADH?
Alcohol and caffeine
What does the decreased release of ADH cause?
Increased urine output and dehydration
How do kidneys regulate blood pressure?
Regulate the amount of fluid in the blood
What hormone acts on the nephrons to increase sodium re-absorption from the distal tubule back into the blood?
Aldosterone
What will follow sodium, causing the blood volume to increase?
Chloride ions and water
Where is aldosterone secreted?
Adrenal cortex (just above the kidney)
What detects a drop in blood pressure?
The juxtaglomerular apparatus (near the glomerulus)
What does the juxtaglomerular apparatus do?
Causes the release of liver proteins, angiotensinogen and rennin
What does angiotensinogen and rennin do?
Stimulates the release of aldosterone from the adrenal gland
What mostly controls the pH balance?
The distal tubule
What is diabetes mellitus?
Caused by the inadequate production of insulin from the pancreas
What happens without insulin?
Blood glucose levels are extremely high and excess glucose remains in the nephron
What does the high osmotic gradient prevent?
Prevent water re-absorption and increases urine production
What are the two types of diabetes mellitus?
Type I and type II
What is type I diabetes mellitus?
The inability to produce insulin, degeneration of beta cells; (genetic)
What is type II diabetes mellitus?
Decreased insulin production or ineffective use of insulin; (lifestyle)
What is diabetes insipidus?
Caused by inadequate production of ADH
Without ADH what happens?
Urine input increases dramatically; extremely thirsty
What is nephritis/Bright’s Disease?
Inflammation of the nephrons
What is a common sympton of nephritis?
Protein in the urine
What does the osmotic gradient have to do with nephritis?
The osmotic gradient causes an increase in urine production
What can nephritis lead to?
Irreversible kidney damage and eventual kidney failure
What are kidney stones?
Caused by the precipitation of mineral solutes from the blood
Where do kidney stones lodge?
In the renal pelvis or ureter, cause major pain and bleeding
How can kidney stones be removed?
Surgery or by using ultrasonic waves that blast the stones into smaller fragments
What is dialysis?
Used for patients whose kidneys no longer function properly
What is hemodialysis?
A machine is connected to the patient’s circulatory system by a vein. Blood is pumped through a series of semi-permeable tubes submerged in solutes that remove wasted from the blood
What is peritoneal dialysis?
Is done through the lining of the abdominal cavity. A catheter tube is inserted and solution is fed into the abdominal cavity for two to six hours. This fluid collects waste from the body and is drained from the catheter when the process is complete
