Introduction to the Lymphatic System

Question 1

what is the Lymphatic System?

Answer 1

→ countercurrent system draining from the tissues all waste materials and recycling surplus fluid, salts, proteins, fat and immune cells back to body
→ Lymphatic System is the cleansing system

Question 2

The lymphatic system (Drainage)

Answer 2

→network of drainage tubes connected to lymph glands

→act as drainage channels for the body’s tissues

→one way drainage system

→Starting with small blind ending tubes like sea anemones they drain into small streams and then ever bigger channels drain to lymph glands and beyond before eventually draining back into the blood circulation in the great veins of the neck.

Question 3

Lymphatic system appearance

Answer 3

→Dermal lymphatic vascular network

→Lymphatic capillaries (initial lymphatics):
→ Blind ended No smooth muscle
→Incontinuous basement membrane

→Collecting vessels:
→Smooth muscle coverage
→Luminal valves Basement membrane

Question 4

what do Initial lymphatics absorb?

Answer 4

→ fluid
→ salts
→proteins and cells from the tissues to make lymph.

Question 5

where is lymph transported to?

Answer 5

→transported down bigger lymphatic vessels which actually contract so pumping lymph onwards

Question 6

what do valves ensure?

Answer 6

→Valves ensure lymph flow is in one direction (downstream) to the lymph glands (nodes) and beyond

Question 7

what happens once the lymph is absorbed into initial lymphatics?

Answer 7

→Once absorbed into initial lymphatics
→lymph is pumped up the leg
→because larger lymphatic vessel contract in a similar way to our main heart

Question 8

what do lymph nodes filter?

Answer 8

filter the lymph where there is also interaction with the immune system

Question 9

discharging lymph

Answer 9

→After passing through a series of lymph nodes

→ large lymphatic vessels eventually discharge lymph into great veins of the neck

Question 10

what is lymph?

Answer 10

→Lymph is interstitial (tissue) fluid containing
→salts, proteins and cells,
→originally formed from a plasma ultrafiltrate

Question 11

What are lymph nodes (Glands)?

Answer 11

→Lymph glands are filter stations positioned at intervals along the lymph drainage route

Question 12

what is the function of lymph nodes?

Answer 12

→ clean up the lymph before it re-enters the blood stream
→by sieving out
→ trapping and destroying (inorganic) foreign materials
→Monitoring the lymph for tell tale signs of (organic) predators e.g.infection
→ plays a vital role in our immune system responses

Question 13

what is the first function of the lymphatic system?

Answer 13

fluid balance(homeostasis)

Question 14

How many litres of plasma is filtered a day?

Answer 14

8 litres

Question 15

What is the process do filtration dependent on?

Answer 15

dependent on Starlin forces. The balance of foces eg the hydrostatic pressure of the water an osmotic pressure

Question 16

What is the nature of venous filtration?

Answer 16

is only transient and does not occur in the steady state. We now know there is a steady state of filtration along the blood vessels.

Question 17

What is interstitial fluid at any time dependent on?

Answer 17

on how much is filtered from the blood vessel and how much is drained by the lymphatic system.

Question 18

What are the three mechanisms of chronic oedema?

Answer 18

• Lymphatic failure with increased capillary filtration (high lymph load overwhelming lymph drainage capacity) = relative lymphatic failure e.g. heart failure, venous oedema
• Lymphatic failure with no increase in capillary filtration (normal lymph load) = absolute lymphatic failure (lymphoedema)
• Lymphatic failure resulting from sustained increased capillary filtration exhausting lymph drainage capacity = absolute lymphatic failure (lymphoedema)

Question 19

How does venous oedema arise?

Answer 19

• Vecarious veins result in higher venous pressure and hydrostatic pressure within the veins that forced more fluid in to the tissue

Question 20

What happens if one’s drainage is robust?

Answer 20

• If the lymph drainage is robust no oedema occurs despite the high volumes of fluid entering.

Question 21

What is lymphoedema?

Answer 21

Lymphoedema is a chronic swelling due to lymph drainage failure.

results in swelling such as a leg with build up of fluid, cells and fat, as well as a predisposition to infections

Question 22

What happens in varicose veins in venous disease?

Answer 22

there is a higher volume of fluid leaving the blood vessels (small veins and capillaries) and entering the tissues of the feet, ankles and legs

Question 23

Second function of the lymphatic system

Answer 23

tissue immunity

Question 24

What is the lymphatic system responsible in terms of immunity?

Answer 24

houses the immune system and is responsible for tissue immunosurveillance

Question 25

What is cellulitis?

Answer 25

Recurrent cellulitis always means a problem with lymph drainage.

Up to 50% lymphoedema patients suffer at least one attack of cellulitis.

the lymphatic system is damaged or overloaded and does not function adequately to fight infection

Question 26

What is he dermal lymphatic?

Answer 26

holds centre stage immunologically in any tissue.

to promote the movement of interstitial fluid and protein molecules back to the circulation.

Question 27

What is the role of the lymphatic system in terms of fat homeostasis?

Answer 27

responsible for gut fat absorption and peripheral fat resorption:

for absorption of dietary fat.
Lacteal lymphatic capillary that absorbs dietary fats in the villi of the small intestine
Disturbances in lacteal function lead to malabsorption

Question 28

What is the role of the sentinel lymph biopsy?

Answer 28

designed to detect lymphatic spread of cancer and guide treatment.

Question 29

What is podoconiosis?

Answer 29

lymph vessels become poisoned from silicates in the soil entering the skin and lymph system when children walk barefoot

Question 30

Primary Lymphoedema, ad give causes

Answer 30

intrinsic failure of the lymphatic system
• Chronic oedema caused by a developmental abnormality of the lymphatic system
• Phenotypes vary in age of onset, site, inheritance patterns, associated features, genetic causes
AT least 4 genes involved

Question 31

Give examples of lymphoedema treatment

Answer 31

• Intraluminal valves- unidirectional flow

* Lymphatic smooth muscle- pumping

Question 32

Recall some diseases associated with lymphatic dysfunction(7)

Answer 32

• Respiratory disease: Asthma, Chronic airways disease, Bronchiectasis, Plural effusion
• CVS : Hypertension, Body fluid balance, Atherosclerosis, recovery from Myocardial Infarction
• CNS: Glaucoma, Dementia
• Infection and Immunity: HIV, Organ rejection, Autoimmunity, Cellulitis, Sepsis, wound healing, tissue repair
• GI: Crohn’s disease causing disturbed phagocytosis
• Cancer Metastases
• Obesity and Hypercholesterolaemia

Question 33

Describe pulmonary oedema

Answer 33

Pulmonary oedema in heart failure is due to raised pulmonary venous pressure causing increased amounts of interstitial fluid which is not sufficiently cleared by lymph so congesting the lung. This interstitial oedema spills out into the alveoli and interferes with O2 exchange

Question 34

What failure of a side of the heart increases pulmonary capillary?

Answer 34

Left sided heart failure increases pulmonary capillary pressure, increasing filtration. Unless lymph drainage increases accordingly, oedema occurs in lung parenchyma

Question 35

The lung generates lymph even though…

Answer 35

pulmonary capillary pressure (10mm Hg is much lower than plasma COP (25 mm Hg).
Pulmonary capillaries are in a filtration state because pulmonary interstitial protein concentration is high (70% of plasma). The COP gradient is therefore lower than the Hydraulic pressure gradient.

Question 36

What is the role of the sub glycocalyx?

Answer 36

The subglycocalyx acts as a regulator or stabilizer for filtration so the default position is no reabsorption