The Lymphatic System

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Based on the Integrated Curriculum for Secondary Schools. KBSM.
Biology Form 5, Chapter 1-Transport,
1.4-The Lymphatic System

1) Formation of interstitial fluid
Blood enters the arterial end of capillaries is under high pressure , the pressure is sufficient to cause fluid leak continuously from blood to spaces between cells.

**What is interstitial fluid? 
Fluid that fills the spaces between the cells.

2) Composition of interstitial fluid.

Interstitial fluid consists of:

• water
• dissolved nutrients
• hormones
• waste products 
• gases 
• small protein from blood 
• leucocytes ( that can ooze through the openings between the capillaries cells )

Interstitial fluid does not consists ( because they are TOO LARGE to pass through capillaries):

• plasma proteins ( albumin, fibrinogen, globulin )
• erythrocytes
• platelets

3) Importance of interstitial fluid 
a) Important to cell because through this fluid that exchanges material between blood capillaries & cells occurs.
b) Nutrient & oxygen diffuse through interstitial fluid into body cells.
c) Carbon Dioxide and waste product diffuse through interstitial fluid into the blood.

4) Fate of interstitial fluid

Where did the 15% of the fluid go?
-The fluid must be returned to the circulatory system to maintain normal blood volume.

For more understanding about the fate of interstitial fluid, please watch the following video. This video also explain breifly about the lymphactic system.
(Which uploaded by Rene LaMontagna on Aug 10, 2010 on YouTube.)

Starts from 1:35- 3:18


5) Structure of lymphatic system

What is lymph?
Interstitial fluid that are not absorb back to the bloodstream drains into the LYMPH CAPILLARIES. This collected fluid is known as Lymph. Lymph is a transparent yellowish fluid.

Lymph also contain tiny droplets of lipids.
-The intestinal lining of the small intestine is covered by villi
-villi contain lacteals
-lacteals are lymph capillaries (droplets of lipid and fat-soluble vitamins are transported to the bloodstream)

Lymphatic system?
-Collect most of the excess interstitial fluid (lymph) from the spaces between the cells and returns it to the circulatory system.
-is a network of lymph capillaries and larger vessels.

Lymph capillaries
- are blind-ended tubes or closed at one end.
- located in spaces between cells.
-interstitial fluid which is not absorbed into the bloodstream drains into these capillaries.

Lymphatic vessels
-lymph capillaries unite to form this lymphatic vessels.
-valves are found to
i) ensure the continuos flow of the lymph away from the tissues.
ii) prevent back flow of lymph

Lymph Nodes
-located at intervals along the lymphatic vessels.
- produce and store lymphocytes.
-defend the body against infection.

Lymphatic system does not have its pumps to move the lymph around through the lymphatic vessels.
It moves forward the subclavian veins with the help of:-
i) one-way valves,
ii) muscular contraction
iii) intestinal movements, and
iv) pressure changes that occur during inhalation& exhalation.

6) How lymphatic system complements the circulatory system?
According to an example in Wiki Answer, Cajohnson27 answered that:-

The lymphatic system is conected with circultion system by the body temp carring large blood vessels around the lymph.The lymphatic system is composed of lymphatic vessels, which are tubes that assist the cardiovascular system in the removal of tissue fluid, also known as lymph, from the tissue spaces of the body. The vessels then return fluid to the blood within the circulatory system.The circulatory system is composed of arteries, veins, and capillaries. This system allows the lymph to travel to lymph nodes where it is filtered of bacteria and other foreign particles. in general, the cardiovascular system and lymphatic system make up the circulatory system. (Johnson, A. 2010)

The following diagram shows the path of lymph in lymphatic system.

The following diagram shows the relationship between lymphatic system and circulatory.

From the lymphatic vessels, lymph will eventually passes one of two main channels which is either:
a) Thoracic duct, or
b) Right lymphatic duct.

7) Role of the lymphatic system in transport
- carry excessive interstitial fluid back to the bloodstream
-helps to maintain the balance of fluid in body
-the process is crucial because water, nutrients and other molecules continously leak out of blood capillaries into the surrounding body tissues.

8) If interstitial fluid not return to the circulatory system, will cause
-swollen of body tissues ( because too much fluid is retained)
-Oedema ( condition of excessive accumulation of interstitial fluid in the spaces between the cells, cause by a blocked lymphatic vessel)

Prepared by Emma.
Pictures and diagram from Google Image.