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Grade 12 > Excretory System > Flashcards

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

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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
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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.
3) pH. 7.4, urine more acid (6)
4) calcium absorption from digestive tract.

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3
Q

The Kidneys

A
  • Kidneys form urine to eliminate waste material carried by the blood
  • Bean shaped, reddish brown colour
  • Renal artery enters kidney, brings blood in
  • Renal vein and ureter exit kidney, brings blood out
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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
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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
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5
Q

Secretion of Hormones

A
  • Kidneys assist endocrine system
  • Kidneys secrete two hormones: calcitriol 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
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6
Q

A Filter

A
  • Bowman’s Capsule is the filtration structure at the top of each nephron
  • 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
  • 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
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6
Q

The 3 Regions of the Kidney

A

Renal Cortex
- Outer layer

Medulla
- Inner layer
- Contains cone shaped tissue

Renal Pelvis

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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
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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
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9
Q

A Tubule

A
  • Bowman’s Capsule connected to a narrow tubule

Tubule has 3 sections:
- proximal tubule
- loop of Henle
- distal tubule

Uses a concentration gradient to absorb and secrete materials into/out of urine

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10
Q

A Duct

A
  • Tubule empties into collecting duct
  • Functions as water-conservation device
  • 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
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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.

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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
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12
Q

General Facts

A

Blood path: Aorta to renal arteries to kidneys

Each kidney has a mass of 150 g and are approximately the size of your fist.

They hold 25% of the body’s blood.

They filter 200 L of fluid each day!

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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
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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.
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.
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.

18
Q

Secretion (Blood to Nephron)

A
  • The movement of materials from the blood back into the nephron is called secretion.
  • 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
Q

Kidney functions

A
  • Regulate water-salt balance
  • Maintain pH
  • Release hormones to maintain homeostasis
21
Q

Water Reabsorption

A
  • Regulated by ADH (antidiuretic hormone)
  • Released from APG when blood becomes too concentrated (dehydrated) – detected by osmoreceptors
  • Increases permeability of distal tubule and collecting duct to reabsorb water
22
Q

Diabetes Insipidus

A
  • 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
Q

Bright’s Disease

A
  • 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
Q

Diuretics

A
  • 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
Q

Reabsorption of Salts

A
  • 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
Q

Aldosterone release and effects

A
  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
  5. Aldosterone stimulates tubules to reabsorb Na+
  6. Cl- and H2O follow Na+
  7. Blood pressure and volume increase
27
Q

Maintaining blood pH

A
  • Normal blood pH = 7.4
  • Inhibits bacterial growth, normal enzymes function

3 mechanisms maintain pH balance:
- Bicarbonate Buffer system
- Respiratory Centre
- The Kidneys

  • The food we eat and metabolic waste products produced can alter blood pH
28
Q

Respiratory centre

A
  • 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
Q

Bicarbonate Buffer system

A

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
Q

Releasing Hormones maintain cell levels

A

The kidneys release erythropoietin to regulate oxygen levels
- Erythropoietin stimulates the bone marrow to produce more red 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
Q

Excretory system disorders

A
  • Various causes and effects
  • Due to kidney involvement in homeostasis, these disorders may have various effects on the body
31
Q

Urinary Tract Infection

A
  • Most common disorder of excretory system
  • Cystitis = bladder infected
  • Urethritis = urethra infected
  • More common in females
32
Q

Urinary Tract Infection Symptoms

A
  • 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
Q

Kidney Stones

A
  • 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
  • Treatment depends on size of stone
  • Many stones pass independently
    through urinary tract
  • Medications may break down
    crystals
  • Ultrasound shock waves
  • Surgery
33
Q

Renal Insufficiency

A
  • 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.
  • Nephrons can regenerate and restore kidney function after short-term injuries
  • With severe damage transplant or dialysis needed
34
Q

Dialysis

A
  • Procedure that removes wastes and excess fluid from the blood when kidney function is lost
  • 2 types: Hemodialysis and Peritoneal Dialysis
  • Hemodialysis uses a man-made membrane (dialyzer) to filter wastes and remove extra fluid from the blood
  • Peritoneal dialysis uses the lining of the abdominal cavity (peritoneal membrane) and a solution (dialysate) to remove wastes and extra fluid from the body
35
Q

Hemodialysis

A
  • 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
Q

Urinalysis

A
  • 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

Grade 12 (8 decks)

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