BIOLOGY FORM 5 CHAPTER 1: 1.4 THE LYMPHATIC SYSTEM

1. 1.4 THE LYMPHATIC SYSTEM
BIOLOGY FORM 5
CHAPTER 1
TRANSPORT

2. Video on The Lymphatic System

3. TISSUE FLUID / INTERSTITIAL FLUID
 bathes the cells and keeps them in the right
condition
 forms from the blood HOW?

4. Tissue fluid:
 forms by filtration when blood passes through
capillaries
 is a watery liquid that resembles plasma minus
its proteins
Tissue cell
Capillary
Tissue fluid
forms Tissue fluid
returns
Direction of
blood flow
Arterial end
of capillary
Venous end
of capillary
15 µm

5. Tissue fluid forms at a capillary bed
under high blood pressure
Arterial flow
Venous flow
Lymphatic flow
As blood flows into
capillaries:
1. Tissue fluid forms.
2. Some tissue fluid
returns to the
blood.

6. EXCHANGE AT A CAPILLARY BED
 capillaries form a dense network in such a
way that every cell is close to a capillary
lymphatic vessel

7. Formation of tissue fluid
 some plasma flows through the capillaries into
the tissues
– become tissue fluid
 tissue fluid is very similar to plasma but does
not have large plasma protein molecules
 Tissue fluid bathes every cell supplying them
with glucose, amino acids, fatty acids, salts and
oxygen
Arterial end Venule end

8. Formation of tissue fluid
 Hydrostatic pressure forces water through the capillary
walls into the cells.
 Other substances move out by diffusion or active
transport
 Tissue fluid also removes carbon dioxide and other
waste material from cells

9. Formation of tissue fluid/Interstitial
fluid & lymph

10. Exchange across the capillaries

11. What forces are involved in tissue
fluid formation?
 two opposing forces :
Blood pressure
forces water
and small
solutes out
Osmotic pressure
created by the large molecules that
cannot leave
Arterial end Venous end

12. Formation & drainage of tissue fluid

13. Formation of tissue fluid
 As blood leaves the capillaries it has lost a lot of its
water and so is far more concentrated
 So water passes back into the capillary by osmosis at
the venous end
 Waste products leave the cells and enter the
capillaries by diffusion

14. tissue fluid
lymphatic vessel
Tissue fluid forms from plasma.
Lymph forms from…………..
10% tissue fluid enters
lymphatic system
lymph
tissue
fluid
plasma
90%

15. Formation of interstitial fluid and
lymphatic fluid (lymph)
Blood
capillary
Interstitial
fluid
Plasma filtered
Body cells
Heart
Reabsorb
lymph

16. Two properties of the capillary network to allow
efficient exchange between the bloodstream & the
cells: 1. Large surface area of the capillary network
2. Being one cell thick

17. Question:
Give a biological explanation for each of the
following.
Tissue fluid forms from blood. (4)
Small molecules are forced out of the
capillary at the arterial end under high
blood pressure from the heart.

18. Kwashiorkor (protein deficiency) results
in the swelling (oedema) of the belly
an osmotic effect
the ability of the blood
to take up water from
the body cavity by
osmosis is reduced
because of the
deficiency of blood
proteins (solutes)

19. What happens to the lymph that
enters the lymphatic system?
Lymph empties into
subclavian veins.

21. The Lymphatic
System

22. An extensive system of blind-ending
tubes which carries lymph
What is the Lymphatic System?

23. Lymph is:
a clear, watery, sometimes faintly
yellowish fluid derived from tissue fluid
similar in composition to blood plasma
1. does not contain erythrocytes
2. contains a much lower concentration of
protein

24. The Lymphatic System consists of:
 Lymphatic
vessels
 Lymphoid tissues
and organs
[Lymphoid tissue: where
lymphocytes develop e.g.
lymph nodes]

25. FORMATION OF LYMPH

26. Lymph
Not all the fluid returns to the blood
capillary
10% enters a separate system of
microscopic tubes called lymph
capillaries
These are part of the lymph system
Lymph vessels have valves that let fluid
enter but not leave them
The lymph capillaries join to form
lymph vessels

27. Lymph
Fluid in the
Blood is called plasma
Surrounding the cells is called tissue
fluid
In the lymphatic system is called lymph
There is very little difference between
these three!

28. Lymph nodes occur all over the body
600-700 lymph nodes
Lymph contains
white blood cells
Lymphocytes
in lymph node

29. Lymph Nodes
• The lymph nodes swell up at times of
infection

30. Three functions of the lymphatic
system:
1. Removes excess tissue fluid from
tissues

31. 2. Absorbs and
transports fats from
the digestive system
Blood
capillary
Thin
epithelium
Lacteal
(lymphatic
vessel)

32. 3. Plays a role in immunity.
A lymph node filters microbes.

33. 4. Transportation

34. How does lymph return to the
blood? Via the:
right
lymphatic duct
left thoracic
duct

35. LYMPHATIC SYSTEM

36. Unidirectional
or
bidirectional
flow of lymph?

37. How is lymph moved through
lymph vessels?
By contraction of the
muscles surrounding
them
By semi-lunar valves present in the
major vessels
How is backflow
prevented?

38. Both the circulatory & the
lymphatic system possess:

39. Lymph
Flow of liquid through the lymph
system is very slow
It depends on movement of our
muscles, the valves in the vessels and
the negative pressure in chest when we
breath in.
Flow is in one direction only, from
tissues towards the heart.

40. What happens if the lymphatic vessels
become blocked as by parasitic worms?
A nematode worm infects
the lymph nodes and
blocks the flow of lymph
throughout the body.
Elephantiasis Disease or
Filariasis: transmitted by a
mosquito bite [over 130
million people are infected]
Wuchereria bancrofti
Female worms: 8 -10 cm long
Males: 4 cm

41. Elephantiasis
– blockage of the lymphatic
system by parasitic worms
Wuchereria bancrofti
- Spread by mosquito

43. Comparison of blood plasma, tissue
fluid and lymph
Blood plasma Tissue fluid Lymph
LOCATION Inside blood vessels Bathing living cells
Inside lymph
vessels
Arterial flow
Lymphatic flow
Venous flow

44. Blood plasma Tissue fluid Lymph
COMPOSITION
Water, proteins,
glucose, salts,
hormones , amino
acids
Oxygen present
Very little protein,
otherwise similar
Oxygen present
More protein than
tissue fluid but less
than plasma. More
lipids, otherwise
similar.
No oxygen
CELLS RBC, WBC, platelets WBC WBC
TRANSPORT
Blood pressure
forces fluid through
capillary at the
arterial end.
Osmosis returns
fluid at the venous
end of the capillary
From capillary
under pressure
and return by
osmosis to
capillary (90%) and
10% to lymph
From tissue fluid
by drainage under
pressure

45. This question is concerned with the
lymphatic system.
a. What is lymph? (2)
Lymph, a colorless to yellowish fluid
whose composition is similar to that
of blood except that it does not
contain red blood cells or platelets,
and contains considerably less
protein.
Question:

46. b. What are the main functions of the
lymphatic system? (2)
- collects fats from the ileum via
lacteals
- plays a role in immunity. Fluid is
filtered in lymph nodes which
contain lymphocytes that kill
microbes
- drains tissue fluid and returns it to
the bloodstream.

47. c. Briefly describe how fluid enters and
leaves the lymphatic system. (3)
Tissue fluid enters the
lymphatic system
located at the venous
end of a capillary.
Lymph is drained into
the subclavian vein by
the right or thoracic
lymph ducts.

48. d. Compare the composition of lymph with that of
blood plasma in the following two situations:
i) Lymph that has just left a lymph node; (1)
Lymph is richer in lymphocytes than plasma as it
leaves the lymph nodes.
ii) Lymph formed in the vicinity of the small intestine.
Is rich in fats as lacteals absorb triglycerides. (1)
e. How is lymph propelled through the lymphatic
system? (2)
By contractions of skeletal muscles. Valves
inside the lymphatic vessels prevent backflow.

50. - blind ended vessels
- permeable to proteins even cells

51. Lymph Nodes
lymphoid organs
- Macrophages and lymphocytes
attack microorganisms
Swollen lymph nodes is caused by
expansion in the number of
lymphocytes