1. CHAPTER 11
Excretion

2. Chapter 11
Excretion
11.1 The Need for Excretion
11.2 Excretion in Humans
11.3 Urine Formation
11.4 Osmoregulation
11.5 Kidney Failure

3. The Need for Excretion 11.1 Learning Outcomes
After this section, you should be able to:
define metabolism and excretion; and
explain why metabolic waste products need to be removed.

4. Chemical reactions in cells
11.1
The Need for Excretion
Chemical reactions in cells
The chemical reactions that take place in living cells can be categorised into:
________ reactions that build up complex molecules
_________ reactions that break down complex molecules
complex substance
simple substance
enzyme
enzyme
complex substance
simple substances

5. Chemical reactions in cells
11.1
The Need for Excretion
Chemical reactions in cells
Examples:
_________
Photosynthesis – synthesis of glucose using carbon dioxide and water
Formation of glycogen from glucose molecules
__________
Oxidation of glucose during respiration to form carbon dioxide and water
Deamination of proteins and amino acids to form urea

6. Chemical reactions in cells
11.1
The Need for Excretion
Chemical reactions in cells
__________ is the sum of all the chemical reactions within the body of an organism.
Metabolic reactions produce _____ ________ that can harm the body if they accumulate.
Therefore, these waste products need to be _______.
anabolism +
catabolism =
metabolism

7. The Need for Excretion 11.1 What is excretion?
The process by which ______________________ and ______________ are __________ from the body.
While most unicellular organisms excrete waste products via simple diffusion, larger organisms have __________________ for excretion.
Examples of excretory organs found in mammals:
skin
lungs
liver
kidneys

8. Chapter 11
Excretion
11.1 The Need for Excretion
11.2 Excretion in Humans
11.3 Urine Formation
11.4 Osmoregulation
11.5 Kidney Failure

9. Excretion in Humans 11.2 Learning Outcomes
After this section, you should be able to:
state the organs involved in excretion and state the excretory products of each of these organs;
state the components of the human urinary system and their functions; and
describe the structure of the kidney and kidney tubule (nephron).

10. in faeces through the intestines
11.2
Excretion in Humans
Waste products excreted by:
skin
lungs
liver
kidneys
urea
excess water
excess salts
carbon dioxide
excess water
bile pigments
urea
excess water
excess salts
in faeces through the intestines
in expired air
in sweat
in urine

11. Excretion in Humans 11.2 Excretory product Organ Mode of excretion
Carbon dioxide
Urea and excess mineral salts
Excess water
Bile pigments
(from breakdown of haemoglobin)
Lungs
Expired air
Kidneys
Urine
Skin
Sweat
Kidneys
Urine
Skin
Sweat
Lungs
Expired air
(as water vapour)
Liver
Faeces
via the intestines

12. Components of the human urinary system
11.2
Excretion in Humans
11.3
Components of the human urinary system
____________
- produce urine
- connect the kidneys to the
bladder
- stores urine temporarily
- passage through which urine is
discharged from the bladder

13. Components of the human urinary system
11.2
Excretion in Humans
11.3
Components of the human urinary system
____________________
- controls the exit of urine from the bladder. When the muscle relaxes, it allows urine to flow into the urethra.
_________
- a concave depression where the blood vessels are connected to the kidney
right kidney
inferior vena cava
aorta
left renal artery
left renal vein

14. Structure of a human kidney
11.2
Excretion in Humans
11.3
Structure of a human kidney
fibrous capsule
The kidney consists of an outer cortex and an inner medulla.
The ________ is the outer dark red region that is surrounded by a fibrous capsule.
The ________ is the inner pale red region that contains medulla pyramids.
________________ are conical structures that contain a large number of kidney tubules.

15. Structure of a human kidney
11.3
11.2
Excretion in Humans
Structure of a human kidney
________________ are narrow tubules that are richly supplied with blood vessels.
Urine is formed in the kidney tubules.
The _________________ is the enlarged portion of the ureter inside the kidney. The pyramids project into this funnel-like space.

16. Structure of a kidney tubule
11.3
11.2
Excretion in Humans
Structure of a kidney tubule
cortex
pyramid
fibrous capsule
renal pelvis
medulla
_________________________
A short, coiled tubule that straightens out as it enters the medulla
____________________
A cup-like structure found at the beginning of the kidney tubule
_______________
The U-shaped portion of the tubule in the medulla

17. Structure of a kidney tubule
11.3
11.2
Excretion in Humans
Structure of a kidney tubule
________________
The tubule opens into a collecting duct which passes through the medulla and opens into the renal pelvis.
_____________________
As the tubule re-enters the cortex, it coils again to form the distal convoluted tubule.
cortex
pyramid
fibrous capsule
renal pelvis
medulla

18. Blood circulation at the kidney tubule
11.3
11.2
Excretion in Humans
Blood circulation at the kidney tubule
Blood enters the kidney via the _____________. 1
Bowman’s capsule 3
Arterioles branch into a mass of blood capillaries (_____________)
glomerulus 2
Renal artery branches into many arterioles
Blood leaves glomerulus and enters blood capillaries surrounding the kidney tubule 4
renal artery 1
Blood exits the kidney via the renal vein 7
Venules join to
form ________. 6
Blood capillaries unite to form venules 5
renal vein

19. Chapter 11
Excretion
11.1 The Need for Excretion
11.2 Excretion in Humans
11.3 Urine Formation
11.4 Osmoregulation
11.5 Kidney Failure

20. Urine Formation 11.3 Learning Outcome
After this section, you should be able to:
outline the function of the kidney tubules in urine formation with reference to ultrafiltration and selective reabsorption.

21. 11.3
Urine Formation
Urine formation involves two main processes within the kidney tubule:
_______________ (occurs at the _________ ____________)
_________ ____________ (occurs at the _________ ____________)

22. Urine Formation 11.3 Ultrafiltration
The mechanical filtration that occurs at the renal corpuscle is called _______________.
Ultrafiltration occurs because:
afferent arteriole (larger)
efferent arteriole (smaller)
there is a _________ ___________ _____ ________ at the glomerulus, and
The ________ ________ around the glomerular capillaries is like a fine filter.
glomerulus
Bowman’s capsule
filtrate

23. Urine Formation 11.3 Ultrafiltration
The two conditions required for ultrafiltration to take place:
_____: high hydrostatic pressure
______: basement membrane around glomerular blood capillaries is _________ _________ and acts as a filter

24. Urine Formation 11.3 Ultrafiltration What is in the filtrate? Water
Small molecules such as glucose, amino acids, mineral salts, urea.
What is not filtered out?
Large molecules such as plasma proteins and red blood cells
afferent arteriole (larger)
efferent arteriole (smaller)
glomerulus
Bowman’s capsule

25. Selective reabsorption
11.3
Urine Formation
Selective reabsorption
Allows ______ ___________ to be reabsorbed
> 80% of filtrate reabsorbed at the ________ __________ ______
Glucose, amino acids, and salts are reabsorbed via _________ and ______ _________.
Water is reabsorbed via _______.

26. Selective reabsorption
11.3
Urine Formation
Selective reabsorption
At the loop of Henle, some _____ is reabsorbed from the filtrate in the tubule.
At the distal convoluted tubule, some _____ are reabsorbed.
At the collecting duct, some _____ is reabsorbed.
The remaining fluid in the tubule passes out of the collecting duct into the renal pelvis to form _____.

27. Chapter 11
Excretion
11.1 The Need for Excretion
11.2 Excretion in Humans
11.3 Urine Formation
11.4 Osmoregulation
11.5 Kidney Failure

28. Osmoregulation 11.4 Learning Outcome
After this section, you should be able to:
outline the role of anti-diuretic hormone in the regulation of osmotic concentration.

29. crenated red blood cell
11.4
Osmoregulation
Osmoregulation
The _____ _________ of blood plasma needs to be kept relatively ________.
red blood cell
If there are large fluctuations in the water potential, numerous problems can occur.
For example, if the blood plasma is too concentrated, the red blood cells (rbcs) would _________ and undergo _________.
dilute plasma
concentrated plasma
burst red blood cell
crenated red blood cell
If the blood plasma is too dilute, the RBCs would absorb water, ______ and _____.

30. Osmoregulation 11.4 Osmoregulation
The regulation of the water potential of blood plasma is called ______________.
The water potential of blood plasma depends on the amount of _____ and _______ in the plasma.
The water potential of blood plasma is controlled by _____________ _______ (ADH).
hypothalamus
pituitary gland
ADH is produced by the __________ and released by the _________ _____.
ADH ____________ reabsorption of water by the kidney tubules.

31. Osmoregulation 11.4 Osmoregulation
Since kidneys help to regulate the concentration of water and salts in blood, they are called ________________.
Osmoregulation maintains the concentration of water and salts within an organism. It is a type of ___________.
As _____ ______ is controlled by removing excess salts and water, _____ ________ is also indirectly regulated by osmoregulation.
High blood pressure can cause blood vessels in the brain to burst, and this would result in a ______.

32. The mechanism of osmoregulation
11.4
Osmoregulation
The mechanism of osmoregulation
The amount of water reabsorbed in the kidney tubules is controlled by ___.
ADH secretion by the _________ _____ depends on ‘instructions’ from the hypothalamus.
The ____________ has receptors that detect changes in blood water potential.

33. The mechanism of osmoregulation
11.4
Osmoregulation
The mechanism of osmoregulation
If there is ______ water in the blood, less ADH is secreted  less water is reabsorbed. The urine excreted is more dilute.
If the body is __________, more ADH is secreted  less water reabsorbed. The urine excreted is more concentrated.

34. Osmoregulation (excess water)
11.4
Osmoregulation
Osmoregulation (excess water)
hypothalamus
causes
stimulates
Pituitary gland secretes less ___
Water potential of plasma _________
Kidney tubules reabsorb less _____
Large intake of _____ (e.g. drinking)
Water potential of plasma returns to ______ level

35. Osmoregulation (dehydration)
11.4
Osmoregulation
Osmoregulation (dehydration)
hypothalamus
causes
stimulates
Pituitary gland secretes more ___
Water potential of plasma _________
Kidney tubules reabsorb more _____
Loss of _____ through sweating
Water potential of plasma returns to ______ level

36. Chapter 11
Excretion
11.1 The Need for Excretion
11.2 Excretion in Mammals
11.3 Urine Formation
11.4 Osmoregulation
11.5 Kidney Failure

37. Kidney Failure 11.5 Learning Outcome
After this section, you should be able to:
outline the mechanism of dialysis as treatment for kidney failure.

38. Kidney failure and dialysis
11.5
Kidney Failure
Kidney failure and dialysis
hemodialyser
(where filtering takes place)
Kidneys are __________ _______ and ______________.
Each person has two kidneys. Therefore, when one kidney fails to function, the person can still lead a normal life.
If both kidneys fail, the person requires either a _________ __________ or ________.
A dialysis machine mimics the function of a kidney.
dialysis machine
filtered blood returning to body
blood flows to dialyser

39. Kidney Failure 11.5 How dialysis works
Blood is drawn from a ______ in the patient’s arm 1
artery 2
Blood is pumped into the dialysis machine through a tubing
filtered
blood
vein 1
The _________ _____ is returned to a ______ in the patient’s arm 6
dialysis tubing 3
The tubing is bathed in a _______ ______ and the tubing is _________________
used dialysis fluid 5
______ ________(e.g. platelets and blood cells) _____ in the tubing
pump
______ _______(e.g. urea) and metabolic waste products ______ out of the tubing 4
dialysis fluid
dialysis
machine
fresh dialysis
fluid

40. essential mineral salt
11.5
Kidney Failure
How dialysis works
The dialysis fluid has the _____ ___________ __ _____ but it _____ ____ ___________ _____. 1
Patient’s blood enters dialysis machine 2
essential mineral salt
urea molecule
protein molecule
red blood cell
dialysis machine
partially permeable membrane
dialysis fluid
patient’s blood 2
dialysis fluid 1
Blood flows in the direction ________ to the flow of the dialysis fluid. 3

41. essential mineral salt
11.5
Kidney Failure
How dialysis works
Filtered blood is returned to the patient 6
essential mineral salt
urea molecule
protein molecule
red blood cell
dialysis machine
partially permeable membrane
dialysis fluid
patient’s blood
filtered blood 6 5
dialysis fluid with
waste products
dialysis fluid
Removal of _________ _____ products from the blood 5
A _______________ ________ is set up between dialysis fluid and the blood. 4 4

42. Chapter 11
Excretion

43. Chapter 11
Excretion
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