Excretory System Flashcards
1
Q
EXCRETION
A
- Process of separating wastes from body fluids
- Eliminating wastes from body
Excretory System also called the Urinary System
2
Q
Maintenance of Water-Salt Balance
A
- Kidneys regulate salt and water in blood ([Salt] affects osmosis)
- Kidneys also regulate blood pressure
- Maintain appropriate levels of potassium, bicarbonate and calcium in blood
2
Q
Functions of the Excretory System
A
- Produces urine and conduct it to the outside of the body
- As kidneys produce urine, they carry out 4 functions that contribute to Homeostasis:
Excretion of metabolic waste
Maintain of Water-Salt concentration
Maintain Acid-Base balance
Secretion of hormones to vitamin D (bones), erythropoietin (red blood cells)
1) Excrete uric acid, ammonia (nitrogenous waste from breakdown of proteins)
2) water-salt balance in the blood. Keep cells isotonic.
hypertonic - dehydrated - dark pee
hypotonic - more water, light pee
3) pH. 7.4, urine more acid (6)
4) calcium absorption from digestive tract.
3
Q
The Kidneys
A
- Kidneys form urine to eliminate waste material carried by the blood
- Bean shaped, reddish brown color
- Renal artery enters kidney, brings blood in
- Renal vein and ureter exit kidney, brings filtered/good blood out
3
Q
Excretion of Metabolic Wastes
A
- Mostly nitrogenous wastes
- Includes ammonia, urea, uric acid
- Ammonia highly toxic but converted in the liver to less toxic urea
- Urea makes up most nitrogenous waste in body – half eliminated in urine
4
Q
Maintenance of Acid-Base Balance
A
- Kidneys regulate acid-base balance in blood
- Kidneys monitor blood pH @ 7.4
- Human urine usually has pH of 6 or lower
- Because of uric acid in urea makes pee acidic
- Anything nitrogenous makes urine more acidic
5
Q
Secretion of Hormones
A
- Kidneys assist endocrine system
- Kidneys secrete two hormones: calcitriol (Vitamin D as a hormones) and erythropoietin
- Calcitriol active form of Vitamin D, promotes calcium absorption from digestive tract
- Erythropoietin stimulates red blood cells in response to increased oxygen demand
6
Q
A Filter
A
- Bowman’s Capsule is the filtration structure at the top of each nephron
- first site of filtration
- Within each capsule renal artery splits into fine network of capillaries called a glomerulus
- Glomerulus acts as filtration device (Inside of Bowman’s Capsule)
- Impermeable to proteins, large molecules and red blood cells – remain in blood. They should never leave in urine, leave through exiting arterioles from glomerulus
- important because we want to keep them in the body
- getting protein in urine will make kidney failure, that’s why abusing protein is bad
- red blood cells leaking into pee is bad because it says that there’s an infection, UTI
- Water, small molecules, ions and urea (waste products of metabolism) pass through walls and proceed further into nephron
- Filtrate = filtered fluid that proceeds from glomerulus into Bowman’s Capsule
6
Q
The 3 Regions of the Kidney
A
Renal Cortex
- Outer layer
Medulla
- Inner layer
- Contains cone shaped tissue
Renal Pelvis
7
Q
The Nephron
A
- The smallest functional unit of a kidney
- Embedded within renal cortex and extending into renal medulla
- Over 1 million per kidney
- Intertwined with capillaries for fast diffusion
- Filters various substances from blood, transforming it to urine
- 3 main regions: filter, tubule, collecting duct
8
Q
Capillary Pores in the Glomerulus/loop of Henle
A
- The pores are too small to allow proteins, red blood cells through… only metabolic waste (ions, small molecules, urea etc.)
- The pressure here is 4x greater than anywhere else – forces materials along a concentration gradient (high to low) and into the Bowman’s capsule
9
Q
A Tubule
A
- Bowman’s Capsule connected to a narrow tubule
Tubule has 3 sections:
- proximal tubule
- descending loop of Henle
- ascending loop of Henle
- distal tubule
- surrounded by capillaries
- if too much sodium, it will diffuse into nephron through capillary
- there can still be diffusion
Uses a concentration gradient to absorb and secrete materials into/out of urine
10
Q
A Duct
A
- Tubule empties into collecting duct
- Functions as water-conservation device
- if too much water, it can leave to go to body
- if too concentrated, water can come in
- only reabsorb or secrete water
- Filtrate that remains here is a suspension of water and solutes
- Called urine at this point
- Highly concentrated, as little water as necessary unless there is an excess in the body
10
Q
Reabsorption into the Blood
A
The transfer of essential solutes and water from the nephron back into the blood is called reabsorption. occurs at the loop of Henle
If none of the filtrate were reabsorbed, you would form 120mL of urine each minute, and would be requiring 1L of fluids every 10 minutes to maintain water balance.
Both active (glucose, amino acids, NaCl) and passive transport (water via osmosis) help reabsorb the fluid back into the blood.
11
Q
Blood Supply to the Nephrons
A
- Afferent arterioles branch off the renal artery and supplies the nephrons with blood
- Afferent arterioles branch into a capillary bed known as the glomerulus
- Blood leaves the glomerulus via efferent arterioles to the capillaries that wrap around the nephron
- The glomerulus is surrounded by the cup-shaped Bowman’s capsule
- The Bowman’s capsule, afferent arterioles and efferent arteriole are in the renal cortex
- Wastes (“future urine”) enter the Bowman’s capsule from the blood. (Diffuse in)
- The capsule tapers off into the proximal tubule, which carries the filtrate to the loop of Henle
- The loop of Henle descends into the medulla and connects to the distal tubule and then into the collecting ducts
- The collecting ducts collect urine from many nephrons, which merge in the renal pelvis
- This is how Substance-filled blood enters the kidney, and gets filtered from here.
- The waste will diffuse out of the blood into the Bowman’s Capsule, which is filled with fluid (due to concentration gradient)
- The Bowman’s Capsule is thin where it is in contact with the cells to allow for rapid diffusion
12
Q
General Facts
A
Blood path: Aorta to renal arteries to kidneys
Each kidney is approximately the size of your fist.
They hold 25% of the body’s blood.
They filter 200 L of fluid each day!
13
Q
Urine Release
A
- Wastes filtered by the kidneys travel along the ureters to the urinary bladder
- A urinary sphincter is found at the base of the bladder
- When the sphincter relaxes, urine enters the urethra and it is voided
14
Q
4 Processes to Urine Formation
A
1.) Filtration
2.) Reabsorption
3.) Secretion
4.) Water reabsorption
15
Q
Filtration
A
- The movement of fluids from the blood into the Bowman’s capsule is called filtration.
- Each nephron of the kidney has an independent blood supply, and blood moves through the glomerulus, a high pressure filter.
- The pressure in the Bowman’s capsule is about 4x as much as in normal capillary beds.
- Plasma proteins, blood cells, and platelets are too large to move through the walls of the glomerulus.
- Smaller molecules pass through the walls and enter the nephron.
- high pressure
- red blood cells, platelets, and protein cannot get through
15
Q
Capillary Pores
A
- The pores are too small to allow proteins and cells
- The pressure here is 4x greater than anywhere else – forces filtration to lower pressure
16
Q
Active Transport
A
- Carrier molecules move Na+ ions across the cell membranes of the cells that line the nephron.
- Negative ions, such as Cl- follow the positive Na+ ions by charge attraction.
- Reabsorption occurs until the threshold level of a substance is reached, excess NaCl remains in the nephron and is excreted with the urine.
- Other molecules are actively transported from the proximal tubule, such as glucose and amino acids back into the blood.
- When we move ions, we move water
- low to high, against concentration gradient
17
Q
Passive Transport
A
The proteins that remain in the blood draw water out of the nephron interstitial fluid and into peritubular capillaries passively.
- high to low movement
18
Q
Secretion (Blood to Nephron)
A
- The movement of materials from the blood back into the nephron is called secretion.
- through capillaries
- happens throughout nephron
- Nitrogen-containing waste (from metabolism of proteins, creating ammonia NH3), excess H+ ions, and other minerals are secreted via urine
- Secretion occurs by active transport –molecules are shuttled from the blood into the nephron
19
Q
How Much Urine Can My Bladder Hold?
A
- With 200 ml, stretch receptors send nervous impulses to your brain and you feel the urge to urinate
- With 400 ml, the nervous signal becomes more urgent
- After 600 ml, all voluntary control is lost and the micturition reflex occurs
20
Kidney functions (MEMORIZE)
- Regulate water-salt balance
- Maintain pH
- Release hormones to maintain homeostasis
21
Water Reabsorption (MEMORIZE)
- Regulated by ADH (antidiuretic hormone)
- Released from anterior pituitary gland when blood becomes too concentrated (too many solutes) (dehydrated) – detected by osmoreceptors
- Increases permeability of distal tubule and collecting duct to reabsorb water
- water is reabsorbed by blood
- pee is dark
If too concentrated in blood:
- too little h2O in blood
- too much osmotic pressure
- release ADH
- osmoreceptors in hypothalamus sense too much osmotic pressure
- sends signal to anterior pituitary gland, releases ADH
- makes kidneys more permeable, water is being reabsorbed
- Osmotic pressure is normal
If too dilute in blood:
- too hydrated
- low osmotic pressure (low solute)
- osmoreceptors in hypothalamus send signal to anterior pituitary gland to stop releasing ADH
- diahhrea
- blood secretes more water
22
Diabetes Insipidus (MEMORIZE)
- ADH (antidiuretic hormone) activity is insufficient
- Water is not reabsorbed
- Excessive urination – 4-8 L per day
- Intense thirst
- Water more quickly excreted than consumed, leading to severe dehydration and ion imbalances
- Synthetic ADH taken to restore the balance of water reabsorption
How would you alter food/nutrient intake?
- Increase the amount of salt in the diet. This would slow the release of water down
23
Bright’s Disease
- Nephritis
- Invading microbes destroy tiny blood vessels in glomerulus
- Alters permeability of nephron
- Proteins and other large molecules able to pass into nephron
- Proteins cannot be reabsorbed therefore drawing water into the nephrons resulting in increased urine output
- -water diffuses to lower the concentration gradient
24
Diuretics
- Increase passing of urine
- Inhibit ADH release (lower permeability of membrane)
- Ex. Ethanol and caffeine
- Drinking diuretics intensify thirst and lead to dehydration
- Even faster in the heat (summer)
25
Reabsorption of Salts
- Water will diffuse (osmosis) to the area with higher salt concentration
- Aldosterone – stimulates salt reabsorption at the distal tubule
- Excrete K+
- Reabsorb Na+
- This affects the water balance, as water follows solute concentrations
- Recall that aldosterone is a mineralocorticoid (hormone).
- The Loop of Henle uses reabsorption of solutes to move water into and out of vessels
26
Aldosterone release and effects
1. Blood volume decreases (so does pressure)
2. Glomerular filtration rate decreases (low pressure)
3. Kidney secretes RENIN
4. Renin stimulates release of Aldosterone from adrenal cortex (MEMORIZE)
5. Aldosterone stimulates tubules to reabsorb Na+
6. Cl- and H2O follow Na+
7. Blood pressure and volume increase
27
Maintaining blood pH
- Normal blood pH = 7.4
- Inhibits bacterial growth, normal enzymes function
3 mechanisms maintain pH balance:
Bicarbonate Buffer system
- too much protons = too acidic = more towards H2CO3
- too much OH = too basic = CO3
- hyperventilation = too much protons in blood = hyperventilation helps to make acidic blood more basic
Respiratory Centre
The Kidneys
- if blood is too acidic, kidneys put protons into urine
- if blood is too basic, kidneys reabsorb protons and put them in blood
- The food we eat and metabolic waste products produced can alter blood pH
28
Respiratory centre
- Controls H+ ion concentration in blood
- Receptors in the brain alter breathing to utilize the bicarbonate buffer:
H+ HCO3- (Blood pH decreases (acid)) ⇌ H2CO3 ⇌ H2O + CO2 (Blood pH increases (basic))
- Faster breathing forces the reaction right, to generate CO2, and use up the H+ as reactants
- If blood pH rises, breathing slows, generate H+ to lower pH
28
Bicarbonate Buffer system
Prevents changes in pH by consuming H+ or OH- ions produced
Converts carbonic acid to bicarbonate and back
- H2CO3 <-> HCO3-
- If H+ is produced/added (acidic blood): HCO3-+ H+ H2CO3
- If OH- is produced/added (basic blood): OH- + H2CO3 HCO3- + H2O
This system maintains pH around 7.4 as substances are added
29
Releasing Hormones maintain cell levels
The kidneys release erythropoietin to regulate oxygen levels
- Erythropoietin stimulates the bone marrow to produce more red blood cells
- when there's not enough oxygen, oxygen demands are high, makes Kidneys signal and release erythropoietin from bone marrow to make more blood cells
If oxygen demand increases, erythropoietin is released by the kidneys
- More RBC can carry more oxygen to counteract
Used by athletes to ‘blood dope’
- Blood doping: large volume of blood is removed and stored in a refrigerator.
- Kidneys realize lower levels of RBC, release erythropoietin, stimulate RBC production, and levels return to normal
- Original blood removed is injected back in to the body to double the blood volume.
- Increases athletic performance by doubling oxygen carrying capacity
- risks: high blood pressure leading to heart failure
30
Excretory system disorders
- Various causes and effects
- Due to kidney involvement in homeostasis, these disorders may have various effects on the body
31
Urinary Tract Infection (MEMORIZE)
- Most common disorder of excretory system
- Cystitis = bladder infected
- Urethritis = urethra infected
- More common in females
- starts in Urethra, then bladder, then ureter, then kidneys
32
Urinary Tract Infection Symptoms
- Painful burning sensation during urination
- Need to urinate frequently even when no urine present
- Bloody or brown urine
- Tenderness in upper abdomen/lower back
- Chills, fever, nausea, vomiting
- Antibiotic treatment
- Preventative measures = proper hygiene
33
Kidney Stones (MEMORIZE)
- Fairly common disorder
- Crystalline formations due to excess calcium in urine
- Causes: recurrent urinary tract infections, insufficient water consumption & low activity levels, high calcium diet
- too much vitamins and minerals in body cause this, residue build-up
- Treatment depends on size of stone
- Many stones pass independently
through urinary tract
- Medications may break down
crystals
- Ultrasound shock waves
- Surgery
33
Renal Insufficiency
- State in which kidneys cannot maintain homeostasis due to damage to their nephrons
- Causes of nephron damage: infection, high BP, Polycystic kidney disease-PKD (cysts in the kidneys), etc.
- leads to issues with filtration
- Nephrons can regenerate and restore kidney function after short-term injuries
- With severe damage transplant or dialysis needed
34
Dialysis
- Machine that filters blood because kidneys cannot do it because of disorders like renal insufficiency
35
Hemodialysis
- Blood is withdrawn from the body by a machine and passed through an artificial kidney called a dialyzer
- A dialyzer (artificial kidney) is attached to the machine
- The dialyzer has two spaces: a space for blood and a space for dialysis fluid
- Dialysis fluid is a special liquid which helps remove waste products from the blood
- The two spaces in the dialyzer are separated from each other by a very thin artificial membrane
- Blood passes on one side of the membrane and the dialysis fluid passes on the other side
36
Urinalysis
- Reveal information about kidney function
- Important diagnostic tool
- Consists of two parts: chemical tests and a microscopic examination
- Urine is also examined to assess its colour, appearance and odour
- Always done in conjunction with other diagnostic tests/follow up
37
Blood pathway
afferent arterioles
glomerulus
efferent arterioles
capillaries
exit through renal vein
38
Where does diffusion happen?
proximal tubule
descending loop of henle
ascending loop of henle
distal tubule
- This is where diffusion happens across the capillary
- blood supply can reabsorb things from nephron
- blood supply can secrete things into nephron
- reabsorption: enter into blood from nephron
- secretion: from the blood/capillaries into nephron
39
What CANNOT pass through the glomerulus into bowman's capsule
Proteins, red blood cells, platelets
40
Polysistic kidney disease
