The Lymphatic System

Question 1

Why does fluid leak out at arterial end?

Answer 1

Fluid tends to leak out at the arterial end of a blood capillary due to the high pressure in the vessel.

Question 2

What happens to the leaked fluid?

Answer 2

Some, but not all, of this fluid returns to the capillary at the venous end.

Question 3

What happens to the excess fluid and proteins?

Answer 3

The excess fluid and plasma proteins in the tissues is returned to the blood by the lymphatic system.

• Fluid returned this way is known as lymph.

Question 4

How does lymph flow towards the heart?

Answer 4

The lymph vessels form a one-way system in which lymph flows only towards the heart and away from the tissue.

Question 5

What do the lymph vessels originate as?

Answer 5

The lymph vessels originate as blind-ended tubes in the spaces between the cells of most tissues.

Question 6

What are lymph capillaries?

Answer 6

Microscopic, close-ended tubes that extend into interstitial spaces to form a network of vessels that parallels blood capillaries.

Question 7

What is the role of lymphatic capillaries?

Answer 7

To absorb interstitial fluid that leaks out of the blood and is not reabsorbed.

Question 8

Describe the structure of lymph capillaries

Answer 8

Usually slightly larger than blood capillaries. They are also more permeable than most blood capillaries

Question 9

What can pass through the lymph capillaries?

Answer 9

Proteins and disease-causing organisms in the intercellular fluid can easily pass through the walls of the lymph capillaries into the lymph.

Question 10

Describe 3 ways the walls of lymphatic capillaries are adapted to absorb interstitial fluid

Answer 10

1. The walls are formed from a single layer of simple squamous epithelial cells.
2. The walls are more permeable than blood capillaries - lack basement membrane
3. The cells partially overlap, forming simple valves that prevents the backflow of fluid.

Question 11

What are lymph vessels?

Answer 11

Found in the small intestine and are like highways that carry lymph throughout the body.

Question 12

What are lymph vessels

Answer 12

Absorb fats and fat-soluble vitamins ensuring proper absorption

Question 13

What do lymph vessels join to make?

Answer 13

The network of lymph vessels joins to form two lymphatic ducts that empty the lymph into large veins in the upper chest.

Question 14

How does lymph through the lymphatic vessels?

Answer 14

Lymph is moved through the lymphatic vessels as a result of smooth muscle, skeletal muscle and valves

Question 15

How does smooth muscle move lymph through the lymphatic system?

Answer 15

The smooth muscle layer of the vessels is able to contract to push the lymph along the vessels.

Question 16

How does skeletal muscle move lymph through the lymphatic system?

Answer 16

The skeletal muscles surrounding the vessels are also able to contract, providing additional force.

Question 17

How does valves move lymph through the lymphatic system?

Answer 17

As there is no central pump, there is no force driving the direction of the flow of lymph.

Therefore, the larger lymph vessels have valves that close when the pressure drops, preventing the backflow of lymph.

Question 18

Where are lymph nodes located?

Answer 18

Occur at intervals along the lymphatic vessels. They are most numerous in the neck, armpits, groin and around the alimentary canal

Question 19

Describe the structure of lymph nodes?

Answer 19

Nodes are bean-shaped and range in length from 1mm-25mm. Each surrounded by a capsule of connective tissue that extends into the node, forming a framework

Question 20

Describe the framework surrounding lymph nodes

Answer 20

Within the framework are masses of lymphoid tissue, containing lymphocyte.

Question 21

What is the function of lymph nodes?

Answer 21

They filter, trap and remove foreign particles and pathogens from lymph before it returns to the bloodstream

Question 22

How does lymph enter lymph nodes?

Answer 22

Lymph enters through vessels on the convex side of the node, filters through the spaces and passes out through vessels on the opposite side

Question 23

How does lymph enter the circulatory system via the lymph nodes?

Answer 23

The lymph passes through several nodes before entering the circulatory system.

Question 24

What does lymph enter the lymph nodes contain?

Answer 24

Cell debris, foreign particles and micro-organisms that have penetrated the body’s external defences.

Question 25

Why are the microorganisms bad?

Answer 25

Some of these micro-organisms may be able to cause disease and must therefore be destroyed.

Question 26

What happens to larger particle in nodes?

Answer 26

Larger particles, such as bacteria, are trapped in the meshwork of fibres as the lymph flows through the spaces in the nodes

Question 27

What is the role of macrophages?

Answer 27

Large phagocytic cells called macrophages destroy these particles. The macrophages ingest the particles by phagocytosis.

Question 28

What happens during phagocytosis?

Answer 28

Projections from the macrophage surround the particle and take it into the cell, where it is destroyed by enzymes

Question 29

How long does it take for bacteria to be destroyed during phagocytosis?

Answer 29

Most bacteria ingested in this way are killed within 10 to 30 minutes.

Question 30

What happens when infections occur?

Answer 30

The formation of lymphocytes increases causing the lymph nodes to become swollen and sore.

Question 31

What happens to an infected finger?

Answer 31

An infected finger may result in swelling and tenderness in the armpit, where they are a large number of lymph nodes

Question 32

What are the functions of the lymphatic system?

Answer 32

1. Fluid Balance 2. Fat Absorption 3. Defense

Question 33

How does the lymphatic system provide fluid balance?

Answer 33

Absorbs excess tissue fluid to return it to the bloodstream

Question 34

How does the lymphatic system provide fat absorption?

Answer 34

Absorbs lipids and fat-soluble vitamins from the digestive tract

Question 35

How does the lymphatic system provide defence?

Answer 35

Removes harmful substances from lymph and blood

Question 36

What is lymph?

Answer 36

A clear to faintly yellow fluid similar in composition to blood plasma. It is derived from blood plasma as fluid pass through blood capillary walls at the arterial end.

Question 37

What is lymph composed of?

Answer 37

Lymph is composed over 96% water and 6% solids which are composed of WBCs and solutes.

Question 38

Describe how the lymphatic system maintains proper fluid balance

Answer 38

1. 30L of fluid passes from blood capillaries into the interstitial spaces 2. Only 27L (90%) is reabsorbed by blood capillaries 3. If the extra 3L (10%) of fluid remained in the interstitial space, dangerous Edema (swelling) would result. 4. The lymphatic system returns this excess fluid to the bloodstream

Question 39

Describe how the lymphatic system allows for fat absorption

Answer 39

1. The lining (mucosa) of the SI is covered with villi. 2. In centre of each villus are blood capillaries and special lymphatic capillaries called lacteals

Question 40

What is the function of lacteals?

Answer 40

Lacteals absorb fats and fat soluble vitamins (A, D, E, K)

Question 41

Describe how the lymphatic system helps defend the body

Answer 41

1. Pathogens are filtered from lymph by lymph nodes and from blood by the spleen 2. Lymphatic organs contain lymphocytes and other immune cells that inactivate and destroy pathogens and other harmful substances such as toxins and cancer cells.