Lymphatic system

Question 1

What does the lymphatic system consist of?

Answer 1

• Lymph
• Lymphatic vessels
• Lymphatic tissue
• Red bone marrow

Question 2

What are the functions of the lymphatic system?

Answer 2

1. Drainage of interstitial fluid
2. Transporting dietary lipids and lipid soluble vitamins (A, D, E and K)

Question 3

Explain the formation of lymph

Answer 3

• Blood plasma leaks out of capillaries into the surrounding tissues due to hydrostatic pressure, forming interstitial fluid.
• The blood protein albumin is too large to leave the capillaries and creates an osmotic pressure inside the capillary
• The blood osmotic pressure pulls interstitial fluid back into the blood capillaries.
• Not all interstitial fluid returns, this fluid needs to be drained or else swelling will occur. Drainage occurs via the lymphatic capillaries and lymph vessels.
• Lymphatic capillaries are “blind ended”. Internally they have a lower pressure than the interstitial fluid
  Fluid enters the lymph capillary via one way minivalves – once inside, it is known as Lymph.

Question 4

Explain the drainage of lymph

Answer 4

• lymph capillaries join together to form lymph vessels. In the small intestine, lymph capillaries are known as lacteals.
• lacteals carry fat laden lymph known as chyle.
• the lacteals join together to form vessels.
• lymph vessels are similar to veins and have certain internal structures to ensure the one way flow of lymph
• lymph vessels then drain into one of two ducts called cisterns chyli, which return lymph to the blood

Question 5

Explain the return of lymph to blood

Answer 5

• the right lymphatic duct drains the upper right side of the body and right arm
• the right lymphatic duct return lymph to the right subclavian drain
• the left thoracic duct drains the rest of the body
• the left thoracic duct begins with the cistern chyli and returns lymph to the left subclavian vein

Question 6

Lymph=

Answer 6

Lymph is colorless watery fluid flowing through your lymphatic system. It carries nutrients and proteins to your cells and tissues.

Question 7

Oedema=

Answer 7

Swelling produced by an increase in interstitial fluid volume. Is closely linked with lymphatic system because the system plays a key role in maintaining fluid balance.
Oedema is evident once interstitial fluid volume increases to 2.5 - 3L.
Factors that influence oedema include:
1. Increased capillary filtration pressure
2. Decreased capillary permeability
3. Increased capillary permeability
4. Obstruction to lymph flow = lymphoedema

Question 8

Lymphoedema

Answer 8

An imbalance in fluid dynamics across capillaries, leading to excessive fluid in tissues.

Question 9

What are lymph nodes?

Answer 9

• found in lymph vessels
• surrounded by connective tissue capsule
• trabecular project inward from the capsule to form compartments, each made of a framework of reticular cells
• bean shaped structures that receive lymph from afferent (going towards) vessels
• the lymph is then drained by efferent (going away from) vessels. = lymph nodes filter lymph

Question 10

Reticular cells=

Answer 10

• phagocytise unwanted substances
• between the cells are lymphocytes
• lymphocytes produce antibodies
  The different reticular cells of lobule are: macrophages, lymphocytes, medullary sinus, reticular fibre

Question 11

What are the different lymph nodes?

Answer 11

• tonsils (in pharyngeal region)
• thymus (in thorax)
• spleen (curves around left side of stomach)
• peyer’s patches (in intestine)
• appendix

Question 12

Lymph nodules: Peyer’s patches=

Answer 12

are groupings of lymphoid follicles in the mucus membrane that lines your small intestine.
Collectively known as MALT:
- Mucosa
- Associated
- Lymphoid
- Tissue

Question 13

Tonsils=

Answer 13

Surround the opening of respiratory digestive tracts. Tonsils filter air. There are 5 tonsils:
- 2x palatine (either side of oral cavity
- 2x lingual (at base of the tongue)
- 1x pharyngeal or adenoid (on posterior wall of the nasopharynx)

Question 14

Thymus gland=

Answer 14

• Found in mediastinum of the heart
• Surrounded by a connective tissue capsule with inward projecting trabeculae
• Function to produce Thymic factor
• Thymic factor is important in setting up the immune system and the formation of T lymphocytes (T cells)

Question 15

Spleen=

Answer 15

Located on the left side of abdominal cavity below the diaphragm. It filters blood.
Comprised of:
- Reticular cells (lymphatic tissue)
- Red pulp (removes worn out platelets and red blood cells, stores platelets and produces red blood cells in the foetus
- White pulp (carries out immune function and removes blood borne pathogens

Question 16

Hydrostatic pressure=

Answer 16

is the pushing force exerted by a fluid (30-10mmHg between the arterial end & venous end, respectively)

Question 17

Interstitial fluid pressure=

Answer 17

is proposed to be slightly negative -3mmHg, which contributes to the outward pull of fluid from the capillaries

Question 18

Colloidal osmotic pressure=

Answer 18

is the pulling force created by blood proteins that are too large to pass through the pores of the membrane (28mmHg in the capillaries)

Question 19

Interstitial osmotic pressure=

Answer 19

is 8mmHg; created by small number of plasma proteins that have leaked into the extracellular tissue space