The lymphatic system

Question 1

What are the functions of the lymphatic system?

Answer 1

• Tissue drainage
• Return of plasma and plasma proteins
• Absorbed fat transport from gut
• Immunity

Question 2

What do lymphatic vessels carry?

Answer 2

Lymph vessels act as reservoirs for plasma and other substances including cells and proteins that have leaked from the vascular system and transport lymph fluid back from the tissues to the circulatory system. Without functioning lymph vessels, lymph cannot be effectively drained and edema typically results.

Question 3

How much cell-free plasma (tissue fluid) is drained on average every day?

Answer 3

~8L

Question 4

What factors influence lymphatic flow?

Answer 4

Muscle contraction
Pressure
Gravity
Infection and inflammation

Question 5

Why is lymphatic flow unidirectional?

Answer 5

Valves prevent back flow of lymph

Question 6

How does infection affect lymphatic flow?

Answer 6

Fluid flow into extracellular spaces increases during infection due to protein accumulation (osmosis) and exudation, this drives increased lymph flow as its responsible for maintaining the balance of fluid in the body works to transport extravasated fluid in the lymphatic vessels. As well as this, is results in increased immune response in nodes, as more antigens are presented and phagocytosis occurs.

Question 7

How much of the daily fluid that enters the lymphatic system reenters circulation through the lymph nodes?

Answer 7

~4L (half)

Question 8

How many lymph nodes are there in average in young adults?

Answer 8

~450

Question 9

Describe the structure of the lymph nodes

Answer 9

Lymph nodes are kidney or oval shaped and range in size from a few millimeters to about 1–2 cm long.
Each lymph node is surrounded by a fibrous capsule, and inside the lymph node the fibrous capsule extends to form trabeculae.
The substance of the lymph node is divided into the outer cortex and the inner medulla.

Question 10

Where are the B cells in the lymph nodes?

Answer 10

Follicles (germinal centres)

Question 11

Where are the T cells in the lymph nodes?

Answer 11

Cortex

Question 12

Which lymph nodes are associated with the midline of the body?

Answer 12

Pre-aortic lymph nodes

Question 13

Which lymph nodes are associated with paired, lateral branches to body wall and paired organs?

Answer 13

Para-aortic (lateral/ lumbar) nodes

Question 14

Where are lymphatic vessels absent?

Answer 14

Eyeball
CNS
Inner ear
Epidermis
Cartilage 
Bone

Question 15

What % of nodes are associated with the gut and found around the abdomen and pelvis?

Answer 15

50%

Question 16

Describe some lymph node pathologies

Answer 16

Primary tumours (lymphomas) such as Hodgkins
Secondary tumours as a result of metastasis
Infections such as tuberculosis and glandular fever (mononucleosis)
Inflammatory hyperplasia
Lymphodenopathy - abnormal no., size or consistency

Question 17

What are the two lymph ducts and what regions of the body do they drain?

Answer 17

Thoracic - rest of body

Right lymphatic duct - upper right quadrant of body

Question 18

Whats the difference between primary and secondary lymphoid tissue?

Answer 18

• Primary lymphoid tissues - where lymphocytes are generated and mature
• Secondary or peripheral lymphoid organs, which include lymph nodes and the spleen, maintain mature naive lymphocytes and initiate an adaptive immune response. The peripheral lymphoid organs are the sites of lymphocyte activation by antigens. Activation leads to clonal expansion and affinity maturation.

Question 19

Give some examples of primary lymphoid organs

Answer 19

Thymus

Bone marrow

Question 20

Give some examples of secondary lymphoid organs

Answer 20

– Spleen
– Lymph nodes
– Peyer’s patches
– Tonsils

Question 21

What is the largest lymphatic organ?

Answer 21

Spleen

Question 22

Where do the lymph ducts drain into?

Answer 22

Jugular/ Subclavian junction in the subclavian vein