Excretory system Flashcards
What is the process of excretion?
it is the process of separating and removing metabolic wastes from the body
what does homeostasis refer to
refers to the ability of an organism to maintain its internal makeup, and maintain fairly stable conditions necessary for survival.
what happens during the metabolic processes of the body
waste products are removed from the site of production by the blood
what happens as wastes accumulate
the kidney removes them from the blood and excretes them to the environment
what does the kidney turns the excretory products into
urine
what do the kidneys filter and regulate from the blood
- they regulate the amount of water, salts, and other substances in the blood
- ## they remove nitrogenous wastes (urine) and excess salts from the blood
what are the three functions of the excretory system
- EXCRETION of metabolic wastes
- OSMOREGULATION: regulation of water and salt in body fluids
- REGULATION of body fluid composition (ex: pH, etc.)
What are 3 nitrogenous wastes
- Ammonia
- Urea
- uric acid
what is ammonia (5)
- the first metabolic product of amino acid deamination – (protein digestion).
- highly toxic
- cannot accumulate in the body
- must be converted into less toxic: uric acid and urea
- quickly converts into the less toxic form
what is amino acid deamination
- IN situations of excess protein intake, deamination is used to break down amino acids for energy. the amino group is removes from the amino acid and converted into ammonia
- the removal of an amino group from a molecule
what is urea (7)
- only in mammals
- converted from ammonia
- less toxic than ammonia
- produced in the liver from the breakdown of protein
- can be excreted in concentrated form
- problem: requires more water to excrete than uric acid
- the main component of urine
what is uric acid (5)
- (in birds)
- produced from ammonia
- not very soluble. can be excreted as a paste with little water loss
- non-toxic
- usually produced from breakdown of DNA or RNA
what are ureters
they are tubes that carry urine from the pelvis of the kidneys to the urinary bladder
what is the urinary bladder
it temporarily stores urine until it is released from the body
what is the urethra
the tube that carries urine from the urinary bladder to the outside of the body.
what is a sphincter
it is a circular muscle that controls the outer end of the urethra, there are two of them. it is to prevent drainage. the inner most one is involuntarily controlled by the brain. during childhood, we learn to volunarily control relaxation of the other one
what is the principle function of the kidney
it is to filter blood in order to remove cellular (consisting of living cells) waste products from the body. It also maintains water balance.
how much blood is in the kidneys at any given time
20%.
What happens if one human kidney fails to work
-humans can function with one kidney
- if one ceases to work, the other increases in size to handle the workload
What are some examples of cellular wastes the kidney excretes?
- urea
- Uric acid
- creatine
what is creatine
a waste product of muscle action
the kidney is composed of three sections, which are
- the outer (renal) cortex
- the (renal) medulla
- the hollow inner (renal) pelvis
cortex
the outside of the kidney. it is where the blood is filtered
medulla
- contains the collecting ducts with carry filtrate (filtered substances) to the pelvis
pelvis
a hollow cavity where urine accumulates and drains into the ureter
deamination (2)
- excess proteins are turned into carbs, but the NH3 needs to be discarded
- The liver converts 2 ammonia molecules and CO2 into urea
nephrons (4)
- the filtering units of the kidney, filtering various substances from blood, transforming it into urine.
- approximately one million nephrons in each kidney
- located within the cortex and medulla of the kidney
- tubes of the nephrons are surrounded by cells and a network of blood vessels
Each nephron consists of the following parts
- glomerulus
- bowmans capsule
- proximal tubule
- loop of henle
- distal tubule
- collecting duct
label the kidney
a
label the nephron
a
bowman’s capsule
a double walled, cup-shaped structure
1. large pores to allow water and dissolved substances through
2. blood pressure in the glomerulus is high, which forces filtration
- in each capsule, the renal artery enters and splits into a network on capillaries called the glomerulus
glomerulus
- network of capillaries within the bowmans capsule
- acts as a filtration device
- high pressure (4x higher than in the capillaries (bundle of microscopic blood vessels))
- moves water and solutes (no proteins) from blood into the nephron
- where filtration of blood plasma occurs; plasma that enters capsule = FILTRATE
- moves filtrate into Bowmans capsule
proximal tubule
- leads from the bowmans capsule to the loop of henle
- mitochondria help with activetransport, passive transport also used
- active transport of many valuable substances back into blood network happens here
in the proximal tubule, what are the substances that go back into blood network by active transport? what doesnt get reabsorbed back into the blood?
- glucose
- amino acids
- sodium
not:
- urea
- some salts
- other toxic substances
loop of henle
- the long hair-pin that extends into medulla
- some of the remaining water, ions, and salt in the (glomerular) filtrate will be returned to the blood
distal tubule
- like the proximal tubule, but on the opposite side
- connects the loop of henle to the collecting duct
distal tubule and collecting ducts
- more water reabsorption occurs here
- this depends on the presence of certain hormones – antidiuretic hormone (ADH)
- EXACT amounts of substances are reclaimed to the blood (very precise)
what is not considered to be a process of excretion
wastes of food residue– feces
what are the protection for the kidneys
ribcage and the fat around the kidneys
how long is the urethra in men and women
men- 20cm
wmen- 4cm
what is the renal pelvis connected to?
the mouth of the ureter flares open to form a funnel-like structure called the renal pelvis
renal pelvis
- has cup-like extensions that receive urine from the renal tissue. this tissue is divided into two sections: the medulla and cortex
renal vein
the main blood vessel that carries blood from the kidney and ureter to the inferior vena cava. the one on the bottom, the bigger one
renal artery
large blood vessels that carry blood from your heart to your kidneys. the one on top, the smaller one.
what is the glomerulus impermeable to
- proteins
- large molecules
- red blood cells
what goes through the glomerulus and into the bowmans capsule
Water, small molecules, ions, and urea
when water and other solutes reclaimed during reabsorption are…
returned to the body via renal veins
how are kidneys vital organs to the body
they are the primary excretory organs and are major organs of homeostasis
where are nephrons located in thekidney
the upper part is located in the cortex while the lower part is in the medulla
where do the substances that are secreted from the nephron enter?
nephrons are associated with a network of blood vessels that spreads throughout the nephron, so the substances secreted from the nephron will enter the surrounding tissues of the kidney. most of these subsatnces return to the bloodstream through the network of blood vessels.
glomerular filtration
moves water and solutes, except proteins, from blood plasma into the nephron, which is called filtrate.
- creates a plasma-like filtrate of blood
- occurs from glomerulus into the bowmans capsule
tubular reabsorption
removes useful substances such as sodium from the filtrate and returns them into the blood for reuse by body systems
- occurs in vasa recta, like the extended form of the glomerulius
- ^^ tubule TO efferent arteriole/capillary
Tubular secretion
moves additonal wastes and excess substances from the blood into the filtrate
- occurs in the proximal tubule : arteriole/capillary TO tubule
water reabsorption
removes water from the filtrate and returns it to the blood for reuse by body systems
what are the four processes of the formation of urine
- glomerular filtration
- tubular reabsorption
- tubular secretion (switch 2 and 3?)
- elimination
what is the process of glomerular filtration
- forces some of the water and dissolved substances in blood plasma from the glomerulus into the bowman’s capsule
- ^^ capillaries of the glomerulus have many pores that are big enough to to allow water and most dissolved substances in the blood plasma to pass easily through the capillaries and into the bowmans capsule. These pores are also small enough to prevent proteins and blood cells from entering
- ^^^ blood pressure within the glomerulus is four times greater than it is in the capillaries. The great rush of blood through the glomerulus provides the force for filtration. This means it is a hypertonic environment, where there is higher concentration inside the cell, or in this case, the capillaries, so it will force it to go outside, into the environment??
- filtrate produced is the same as blood plasma minus the proteins and blood cells
- this process filters blood
process of tubular reabsorption
- can return about 85%-99% of filtrate to the blood, but it depends on how much water and salt you must conserve
- reabsorbed substances go to efferent arteriole
- occurs within proximal tube to capillary
- involves both active and passive transport
- cells of proximal tubule are richly endowed with mitochondria, which use the energy-releasing power of ATP to drive the active transport of sodium ions (Na+), glucose, and other solutes back into blood.
- Negatively charged ions tag along passively, attracted by the positive charge on transported ions. water follows ions by osmosis
- water rushes into blood because of osmosis
process of tubular reabsorption– distal tubule
- the active reabsorption of sodium ions from the filtrate into the capillaries depends on the needs of the body.
- passive reabsorption of negative ions like chloride occurs by electrical attraction
- the reabsorption of ions decreases the concentration of the filtrate, which causes water to be reabsorbed by osmosis
- more precise and accurate regulated absorption occurs in the distal tubules
- additonal quantities of salt and water may be reabsorbed.
- under the control of hormones
descending limb filtration - loop of henle
- descending limb- permeable to water, not really to ions
- as the loop gets deeper, it encounters an increasingly salty environment. it lies in the medulla which is relatively salty (hypertonic)
- water moves across through osmosis due to the salty environment. also (?????) solutes diffuse from the ascending CAPILLARY to the descending limb (??????)
- at the bottom of the descending limb, the salt concentration is the highest
ascending limb filtration- loop of henle
ascending limb- no water is transported, only solutes diffuse
- the thin-walled segment of the ascending tubule (near the bend in the loop) is now impermeable to water and slightly permeable to solutes
- sodium ions diffuse from the filtrate along their concentration gradient and pass into nearby blood vessels.
- at the thick -walled portion of the ascending limb, sodium ions are moved out of the filtrate by active transport (potassium K+ and chloride Cl- are also transported by passive transport).
- ^^ this helps replenish the salty environment of the medulla, which aids in the absorption of water from filtrate in the descending limb. the removal of sodium ions from the filtrate in the thick-walled portion of the tubule makes the filtrate less concentrated than the tissues and blood in the surrounding cortex of the tissue. by now, 2/3 of the Na+ and water from the filtrate have been reabsorbed
process of tubular secretion – distal tubule
- potassium ions are actively secreted into the distal tubule from the bloodstream in the capillaries.
- hydrogen ions are also actively secreted as necessary in order to maintain and regulate the pH of the blood. it increases (7.3-7.4) while urine pH decreases (4.5-8.5)
- other subsatances that are normally not apart of the body, such as penicillin and other drugs are secreted into the distal tubule.
- under the control of hormones
- mechanism is active transport (and passive diffusion?)
where does tubular reabsorption take place
proximal tubule»_space; collecting duct
where does tubular secretion take place
distal tubule and collecting duct
why is potassium secretion important in tubular secretion
prevents accumulation of potassium that can create neural and muscular problems
how is water reabsorbed in the nephron during reabsorption
it is passively reabsorbed from the proximal tubule as the solutes are actively removed from the filtrate
during reabsorption, active transport what solutes into the capillary bed? (4)
- glucose
- amino acids
- vitamins
- inorganic ions (Na+)
efferent arteriole
feeds into second capillary network that surrounds the tubule (vasarecta)
- this network receives absorbed substances and eventually leads to the renal vein
- takes away blood from the glomerulus (filtered)
afferent arteriole
carry blood to the glomerulus (unfiltered)
what happens to the permeability of water in the distal tubule and collecting duct if a person is for example, dehydrated
if blood plasma is too concentrated, the permebility to water in the distal tubule and collecting duct is increased. This causes more water to be reabsorbed into the surrounding capillaries in order to conserve water in the body.
only ____ in the blood plasma pass from the glomerulus into the bowmans capsule
fluid and dissolved materials (wastes, nutrients, ions)
what is the elimination pathway for urine
- collecting duct
- renal pelvis
- ureter
- urinary bladder
- urethra
- environment
what do kidneys control and activate
they control water, pH, secrete erythrypoietin ( a hormone that stimulated red blood cell production), and activate vitamin D production in the skin.
- why doctors can tell so much from urine
What is ADH
the anti-diuretic hormone
- influences the rate of water reabsorption into the blood from collecting ducts
- travels through the blood to the kidneys, where it increases the permeability of the distal tubule and collecting duct, allowing more water to be absorbed and into the blood. this dilutes the blood and allows osmotic pressure to become back to normal
- released by the pituitary gland in the brain
- makes the upper part of the distal tubule permeable, this concentrates the urine.
- raises blood pressure
what produced ADH and how.
osmoreceptors in the hypothalamus of the brain produce ADH when stimulated by low blood volume and increased osmotic pressure
what is osmotic pressure
the force generated as water moves by osmosis. The greater the concentration gradient, the greater the osmotic pressure becomes
- if one person is dehydrated, osmotic pressure increases
when does adh stop being produced
if blood plasma is too dilute (when the osmotic pressure is too low). osmoreceptors prevent or completely stop the release of ADH. this makes osmotic pressure of the plasma and tissue fluids rise to normal
about ____% of water filtered in the nephron is reabsorbed in the _____
- 85%
- proximal tube
what kinds of drinks are diuretics in part by decreasing ADH release
alcohol, caffeine, black tea, and many carbonated drinks
- increases the volume of urine
- alcohol stimulates urine production
- increases water loss to urine, and because of that, drinking an alcoholic beverage intensifies thirst and leads to dehydration
what is the result of ADH
- increases permeability to water of the collecting duct
- water is reabsorbed
- urine is more concentrated
- volume is reduced
what happens when body fluids are too concentrated vs when they are too dilute? basically osmotic pressure too high vs too low
high: adh is released and osmotic pressure of body fluids decreases
low: adh stops being released and osmotic pressure of body fluids increases
aldosterone
- released by adrenal glands in response to drop in blood pressure of volume. detected at JGA (juxtaglomerular apparatus)
- simulates distal tubes and collecting ducts to reabsorb Na+.
- since Na+ is followed passively by water and chloride, it has the net effect of retaining both salt and water.
- also stimulates the secretion of potassium ions (K+) into distal tubes and collecting ducts if K+ concentration in the blood is too high
what is the most abundant ion in the blood plasma
sodium ions (Na+)
- although its the most abundant, its concentration can fluctuate dramatically depending on diet and the consumption of beverages with diuretic effects.
Diabetes insipidus and medication
- not enough ADH secreted, excessive urination, results in dehydration
- alcohol, caffine, and many carbonated diuretics take part in decreasing adh release
- weakness
treatment medication, reducing water intake helps in some cases
UTI (urinary tract infection) + med
- very common disorder
- more common in women than men because if differences in anatomy. in females, the urethral and anal openings are closer together, making it easier for bacteria from the bowels to enter the urinary tract and start and infection
- synmptoms include painfyl urination (burning feelng), requent urination (even if no urine present), and bloody or brown urine
- can lead to chills, fever, nausea, vomiting, and upper abdomen tenderness
-if left untreated, all UTIs can lead to permanent kidney damage and possible kidney failure
- general treatment is by antibiotics, but if serious, surgery may be needed
- personal hygeine and increased water consumption can help 9wiping front to back)
- if the bladder has a bacterial or viral infection, the disorder is called cystitis. if only the urethra is involved, the condition is called urethritis
diabetes mellitus
- doesnt produce insulin, take injections of insulin
- causes large amounts of glucose to remain in blood
- opposes osmotic pressure in the nephron which means water stays in and is lost in the urine
- increased thirst and urine production
nephritis
- inflammation (swelling) of the nephrons
- microbes can destory blood vessels and affect the permeability of the nephron
- proteins cannot leave, which alters osmotic pressure > water is lost > damage to kidneys
symptoms
- reduction in urine volume
- dark urine (contains blood)
- increase in blood pressure
kidney stones
- most kidney stones (85%) form due to excess calcium in the urine
- other causes aare recurrent urinary tract infections, insufficient water consumption, and low activity levels
- stones pass through urinary tract
treatment varies depending on the size of the stones
- medications may help to break down crystals
- if the stones are less than 20mm in diameter, ultrasound shock waves (lithotripsy) can be used to disintegrate the crystalline structure
- surgery for larger stones
kidney coronary connection
- high blood pressure (hypertension) is one of the main reasons for kidney damage
- kidney blood vessels are damaged from the pressure
- hypertension can be caused by too much salt in your diet or atherosclerosis
- unfortunately symptoms only become visible once a large amount of damage is done
peritoneal dialysis
- blood is cleaned inside the body in the abdomen in the peritoneal cavity
- this cavity is filled with dialysis fluid that enters the body through a permanently implanted catheter
- excess water and wastes pass through the peritoneum into the dialysis fluid, which is then drained from the body and discarded
- the process is repeated three to five times a day
- this treatment can be preformed without assistance, either at home or at work
hemodialysis
- dialysis - cleaning the blood
- the blood is circulated through an artificial kidney machine, which contains a dialyzer (also called an artificial kidney)
- the dialyzer has two spaces separated by a thin membrane
- blood passes on one side of the membrane and dialysis fluid passes on the other
- the wastes and excess water pass from the blood through the membrane into the dialysis fluid, which is then discarded
- the cleaned blood is then returned to the bloodstrem
kidney transplant + laparoscopy
- dialysis is used when people have kidney disease. however it is not a cure, and is not intended to be a long-term solution
- individuals with 10% or less kidney function will eventually need a kidney transplant
- organ donation rate in canada is less than 40%
- immunosuppressive drugs need to be taken after the transplant
- two sources for kidney transplants: cadaveric donors, live donors
- laparoscopy- minimally invasive surgical technique used to remove kidney from living donor
renal insufficiency
a general term used to describe the state in which the kidneys cannoy maintain homeostasis due to damage in their nephrons
what are some souces of damage in nephrons (6)
- kidney infection
- high BP
- diabetes mellitus
- trauma from a blow to the blower back ot constant vibration from machinery
- poisoning (skin contact, inhalation of fumes, or ingesstion of contaminated food) by heavy metals such as mercury and lead or solvents such as paint thinners
- atherosclerosis (which reduced blood flow to the kidneys)
-blockage of tubules
what are some of the solutions nephrons have when the kidney is damaged
- they can regenerate and restore kidney function after short-term injuries
- when some nephrons are irreversibly damaged, others can compensate for their lost function.
- a person can survive on 1/3 of a kidney
- if 75% or more nephrons are destoryed, urine output is inadequate to maintain homeostasis. under these circumstances, a person requires a means for replacing kidney function
- ^^ achieved either with a kidney transplanted from a donor, or with an artificial kidney that preforms a blood cleansing process called dialysis
what is a way to [protect both the kidneys and the excretory system (kidneys + bladders)
maintaining a healthy blood pressure
how does high blood pressure damage the nephron filtering syste,
forces large particles into nephron, inflames it.
