EXCRETION Flashcards
What is excretion?
The removal of the waste substances of metabolic reactions, toxic materials and substances in excess of requirements.
What are excretory organs?
Lungs
Kidneys
liver
What is produced by the breakdown of respiration?
CO2
How is CO2 removed?
It is carried away by the blood and removed in the lungs.
Why must CO2 be removed?
It dissolves in water easily to form an acidic solution which can lower the pH of cells
What can an acidic atmosphere cause?
It can reduce the activity of enzymes in the body which are essential for controlling the rate of metabolic reactions.
What happens to most of the food molecules absorbed into the blood?
They are carried to the liver for assimilation
What is assimilation?
When food molecules are converted to other molecules that the body needs.
What is fibrinogen needed for?
Blood clotting
What happens to excess amino acids?
They are broken down in a process called deamination
What does deamination involve?
The actions of enzymes to split up the amino acid molecules.
What happens to the part that contains carbon?
It is turned into glycogen and stored
What happens to the part that contains nitrogen?
Is removed and turned into ammonia
What happens to the ammonia produced?
Converted to urea which is less toxic
What happens to the urea?
It is dissolved in the blood and is taken to the kidney to be excreted as urine.
Where are the kidneys located?
Back of the abdomen
What functions does the kidney have?
Regulate water content in the blood
Excrete waste products of metabolism and substances of excess requirements
What is osmoregulation?
Regulate water content in the blood
What does the kidney tissue consist of?
Many capillaries and thousands of tiny tubules called renal tubules( nephrons) held together with connective tissue
What color is the cortex?
Dark outer region
What part is the medulla?
Lighter inner zone
What is the renal pelvis?
Where the ureter joins the kidney
Where is blood filtered and where is urine produced?
In the nephrons
Where does each nephron begin?
In the cortex of the kidney
Where do the tubules join up?
In the pelvis to join up with the ureter
Where does the ureter lead to?
To the bladder where urine is stored
What is the glomerlus?
Knot of capillaries that branch of the renal artery and lead to each nephron
Where does the glomerlus sit?
Inside a cup shaped structure called the Bowman’s capsule
What happens as the capillaries get narrower in the glomerulus?
Increase in the pressure on the blood
What does the pressure of the blood cause?
Causes small molecules including water and most substances dissolved in the blood to be squeezed out of the capillaries and into the Bowman’s capsule
What does the filtrate contain?
Water, salt, glucose and urea
Which molecules are too big to pass through?
protein molecules and blood cells
What is the first substance to be reabsorbed?
Glucose
Where is glucose reabsorbed?
In the proximal convoluted tubule.
How is glucose absorbed?
By active transport
What are nephrons surrounded by?
Capillaries where useful substances from filtrate are reabsorbed and passes into the blood
Where does the remaining filtrate continue?
through the hoop of henle
What happens at the loop of Henle?
Necessary salt and water are reabsorbed back into the blood by diffusion and osmosis.
What happens to the remaining liquid?
Continue through the distal convoluted tubule to the collecting duct where water is reabsorbed into the blood according to the body’s demand.
What is the ADH?
Anti diuretic hormone
What happens to the urine?
Flows out of the kidney through the ureter and into the bladder
What does the urine contain?
this contains urea and salts in water.
Where is water reabsorbed at?
Loop of Henle and collecting duct
Where is salts reabsorbed at?
Loop of Henle
Where is glucose reabsorbed at?
First convoluted tubule
What factors affect the volume and concentration of urine?
Water intake
temperature
Exercise
How does water intake affect the volume and concentration of urine change?
More fluids drunk means more water will be removed so a large quantity of urine is produced
How does temperature affect the volume and concentration of urine change?
The higher the temperature the more water is lost in sweat and so less will appear in urine
How does exercise affect the volume and concentration of urine change?
More exercise done the more water is lost in sweat and so less will appear in urine
Why is water and salt concentration controlled?
To keep the concentrations the same inside the cells as around them.
How does osmoregulation help the cells?
Protects the cells by stopping too much water from entering or leaving by osmosis.
How is water lost from the body?
Sweat
Water vapour from when we exhale
Why might a kidney not work?
Accident or disease
What are two treatments of kidney failure?
Dialysis
Kidney transplant
What is kidney dialysis?
This the artificial method of filtering the blood to remove toxins and excess substances
What does the dialysis machine act as?
An artificial kidney
What does the kidney dialysis machine do?
To remove most of the urea and maintain the water and salt balance of the blood
Where is the unfiltered blood taken from in dialysis?
Artery in the arm
Where is the filtered blood returned in dialysis?
In the vein
What are the blood and dialysis fluid separated by?
A partially permeable membrane
What does the dialysis fluid contain?
A glucose concentration similar to normal level in blood
A concentration of salts similar to a normal level in blood
No urea
What happens because the dialysis fluid has no urea in it?
A large concentration gradient is formed meaning the urea diffuses across the partially permeable membrane
What happens because the dialysis fluid has a glucose concentration equal to the normal sugar level?
No net movement of glucose
What happens because the dialysis fluid has a salt concentration equal to the blood?
No net movement
How long does dialysis take?
3- 4 Hours
What is added to the machine?
An anticoagulant is added to the blood to prevent the blood from clotting and slowing the flow.
What is kidney transplant?
Implanting a kidney from an organ donor into the patient’s body.
Benefits of kidney transplant
More freedom
Diets are less restrictive
use of dialysis machines is expensive
long term solution
Disadvantages to kidney transplants
Donors don’t have the same antigens on cell surfaces- organ rejection
You have to take immunosuppressant drugs which have side effects
Tissue typing can lead to long waits
There are not enough donors.
What does kidney dialysis remove?
Urea, ammonia, water
Where is the concentration of urine determined?
Medulla
Explain the function of the renal capsule
This is where ultrafiltration occurs. The high blood pressure assists molecules to diffuse into the glomerulus. Protein and blood cells are too big to go through but substances such as glucose are able to pass through
What is the renal capsule?
The glomerulus and Bowman’s capsule
Where does filtration occur?
In the glomerulus
Describe how urea is transported in the blood to the kidney
Dissolved in plasma
What does Bowman’s capsule do?
Collects the filtrate
Where does reabsorption take place?
In the proximal convoluted tubule
