Lymphatic system

Question 1

Name the components of the lymphatic system

Answer 1

Red bone marrow

Lymphatic vessels

Lymph nodes

Lymph tissues

Question 2

What are the main functions of the lymphatic system?

Answer 2

To drain interstitial fluid

To transport dietary molecules and lipid soluble vitamins (A,D,E,K)

Facilitation of immune system
carry pathogens to lymph nodes
return leaked proteins to the blood

Question 3

What are the 4 types of pressure involved in the lymphatic system?

Answer 3

Hydrostatic pressure
Interstitial osmotic pressure
interstitial fluid pressure
colloidial osmotic pressure

Question 4

Define hydrostatic pressure

Answer 4

It is the pushing force exerted by a fluid at arterial through venous ends, It is the pressure exerted by the blood against the vessels
(30-10mmHg)

Question 5

Define Interstitial Osmotic pressure

Answer 5

is the pressure created when a small number of proteins link from capillaries into extracellular space around 8mmHg

Question 6

Define Colloidal osmotic pressure

Answer 6

Is the force created by the exertion of plasma proteins that are too large to fit through capillaries e.g., albumin
(28mmHg in capillaries)

Question 7

Define Interstitial fluid pressure

Answer 7

Contributes to the outward pull of the capillaries, is slightly negative (-3mmHg)
It is the hydrostatic pressure in the interstitial fluid

Question 8

Describe the formation of the lymph

Answer 8

1. Blood has high hydrostatic pressure which pushes plasma out of capillaries into surrounding tissue forming interstitial fluid
2. albumin a plasma protein is too large to leave capillaries, so exerts osmotic pressure inside capillaries
3. this osmotic pressure pulls interstitial fluid into capillaries
4. not all interstitial fluid re-enter capillaries, 10% forms lymph & drained into lymphatic system
5. lymph needs to be drained to prevent oedemas
6. lymph capillaries contain a lower pressure than interstitial fluid, fluid enters lymph capillaries via mini valves, once fluid enters it is known as lymph

Question 9

Describe the draining of the lymph

Answer 9

Lymph capillaries join to form lymph vessels, lymph flows in 1 direction (valves)
The lymph drains into 1 of 2 ducts (left/right)
Lymph is returned to the blood

In small instestine (ileum), lymph capillaries are called lacteals which join to form vessels. They carry chyle (fatty lymph) which drain into a cisternae (sac) chyli.
Acts as a channel for lipid products from digestions

Question 10

Describe how the lymph is returned to the blood

Answer 10

upper right duct drains the upper right side of the body and returns the lymph via right subclavian vein in chest
upper left duct drains the left side of the upper body, returns the lymph through left subclavian vein

Question 11

Describe the relationship between the cardiovascular & lymphatic system

Answer 11

These systems are both part of the circulatory system. Both are involved in waste removal and transportation of fluid around the body.
Work together to keep a balance of nutrient dispersal and waste removal.
Lymph is returned to cardiovascular system

Question 12

What is an oedema and what factors induce an oedema

Answer 12

An oedema is a build up of fluid, occurs where there is an increase in intersitial fluid. (from 2.5 to 3L)
Factors:
- increased capillary permeability
- obstruction to the lymph
- increased capillary filtration pressure,
- decreased capillary colloidal pressure

Question 13

What are lymph nodes and describe their structure

Answer 13

A lymph node is a bean-shaped structure found over the body. They receive lymph from afferent vessels
The lymph nodes are then drained by an efferent vessels. Lymph nodes filter the lymph
Structure:
- are surrounded by capsules
- contain trabeculae to make compartments
- Each compartment has reticular cells
- reticular cells are involved in phagocytosis, engulf & digest pathogens
- lymphocytes found between reticular cells, they produce antibodies

Question 14

What is a melanoma

Answer 14

A melanoma is a form of skin cancer. When a melanoma cells form they often spread to a nearby lymph node.
A stage 3 melanoma is where cancer cells have spread to a lymph node

Question 15

What is the peyer’s patch

Answer 15

A small cluster of lymphatic cells found in the ileum (small intestine)
They analyze and respond to gut microbes
Peyer’s patch contains T & B cells to respond to molecules, act as a line of defense against harmful/ inflammatory dietary agents & harmful microbes

Question 16

Describe the role of tonsils and their location in the lymphatic system

Answer 16

There are 5 tonsils
- 2 palatine tonsils found in the oral cavity
- 2 linguae tonsils found at the base of the tongue
- 1 Pharyngeal tonsil found at posterior wall of nasopharynx
Tonsils are used to filter air, they filter germs & pathogens to protect the body from infection. They contain a lot of WBC

Question 17

Describe the role of the thymus gland in the lymphatic system

Answer 17

Located in the mediastinum, surrounded by a connective tissue capsule containing inward projecting trabeculae.
The thymus produces thymulin, which sets up the production of T-cells & stimulates the maturation of T-cells
Largest in childhood, during adulthood thymus decreases in size

Question 18

Describe the role of the spleen in the lymphatic system

Answer 18

The spleen is involved in the breakdown
& removal of RBC + plaetelets. Located on the left hand side below the diaphragm, contains reticular cells, red pulp which filters blood, stores WBC, removes old defective RBC
Also contains white pulp which is involved in the immune response

Question 19

Order of capillaries

Answer 19

1. Lymphatic capillaries
2. collecting lymphatic vessels
3. lymphatic trunks
4. lymphatic ducts

Question 20

Define function of lymphatic trunk

Answer 20

Collecting lymphatic vessels form together into the lymphatic trunk which drain large areas of the body. Named after the region they are found in e.g., subclavanian

Question 21

Define the function of the Thoracic duct

Answer 21

Drains the rest of the body, it collects lymph from lumbar trunks (lower limb), intestinal trunk

Question 22

Describe the transport of lymph in the lymphatic system

Answer 22

The lymphatic system lacks a pump, so lymph flows slowly & at low pressure through capillaries
Skeletal muscle, and breathing mechanism aid in the flow of lymph & prevent backflow
During physical activity lymph flows rapidly

Question 23

Function of dendritic cells

Answer 23

Capture antigen and return them to lymph nodes

Question 24

Function of reticular cells

Answer 24

The produce reticular fibre stroma which is a network that supports other cells types in lymph tissue

Question 25

Describe the importance of lymphatic tissue

Answer 25

It houses lymphocytes and provides a site where they can multiply and become active. It also provides a good lookout point for macrophages & lymphocytes

Question 26

Name the 2 types of lymphatic tissue

Answer 26

Diffuse lymphoid tissue
Lymphoid follicles (nodules)

Question 27

Describe the structure &function of diffuse tissue

Answer 27

a loose arrangement of lymphoid cells & some reticular fibres,
Found in most organs
Large amounts found in the digestive tract

Question 28

Describe the structure &function of lymphoid follicles

Answer 28

consists of tightly packed lymphoid cells & reticular fibres
They have germinal centres where B cells can be found
These centres enlarge when B cells divide to produce plasma cells
Found in the peyer’s patch & appendix

Question 29

Describe the structure &function of the primary lymphoid organ

Answer 29

This is where B & T cells mature, in the red bone marrow & thymus.

Question 30

Describe the structure &function of the secondary lymphoid organ

Answer 30

Where mature lymphocytes first encounter their antigens and become activated
Includes spleen, peyer’s patch, MALT, lymph nodes ETC

Question 31

What are the role of lymph nodes?

Answer 31

• To cleanse the lymph by containing macrophages which destroy microorganisms that enter lymph from connective tissue, preventing them from being delivered to the blood & spreading elsewhere
• immune activation: lymph nodes & lymph organs are strategically located in areas where antigens are commonly found so they can be activated and attack them
  Many antigens brought by dendritic cells to lymph nodes. This causes the activation of T cells