Lymphatics

Question 1

What vessel aids the movement of lymph in lymph vessels? What vessels specifically do not?

Answer 1

Adjacent arteries aid the movement of lymph down the lymph vessel - adjacent veins do not!

Question 2

In what direction is flow in lymph vessels?

Answer 2

Superficial to deep

Question 3

How much plasma is returned to venous system each day by the lymphatics?

Answer 3

3 litres

Question 4

Describe the surface of the primary lymph capillaries.

Answer 4

Endothelial cells that overlap to form microvalves that open only in one direction

Question 5

List 3 body movements that passively act to compress lymph nodes and maintain the flow of lymph.

Answer 5

Skeletal muscle contractions
Movement of respiratory components
Intestinal smooth muscle contraction

Question 6

How do microvalves act when pressure within the lymphatic capillary is greater than outside?

Answer 6

They remain shut, as not to let lymph flow out of the vessel and back into the interstitium

Question 7

What 3 organs are associated with the lymphatics?

Answer 7

Lymph nodes
Spleen
Thymus

Question 8

What is the function of a lymph node?

Answer 8

Lymph nodes act to filter lymph as it transported back to the bloodstream, in an effort to prevent harmful pathogens/material re-entering circulation

Question 9

Describe the structure of a lymph node.

Answer 9

Afferent vessels enter the lymph node which is surrounded by a capsule - initially the lymph enters the cortex, which contains the cortex which contain the terminal centres - they then pass through trabeculae to the medulla before leaving the hilum via efferent lymphatic vessels

Question 10

What are germinal centres?

Answer 10

Sites of B cell activation and proliferation

Question 11

How does the number of afferent lymph vessels compare to the number of efferent lymph vessels? How does this affect the activity of the lymph node?

Answer 11

There is a greater number of afferent lymph vessels compared to efferent lymph vessels - this causes a back-log of lymph, giving time for lymphocytes to carry out their appropriate functions

Question 12

List 3 functions of the spleen.

Answer 12

Lymphocyte proliferation
Immune surveillance
Blood-cleansing functions

Question 13

What are the 2 main structural components of the spleen? What are their roles?

Answer 13

The spleen contains red pulp and white pulp:

• white pulp - involved in immune regulation, and is where most B and T lymphocytes are located, attached to reticular fibres
• red pulp - involved in processing of ‘worn-out’ erythrocytes and blood-borne pathogens - both are engulfed by macrophages - red pulp also recycles iron from worn-out erythrocytes haemoglobin

Question 14

What is the role of the thymus?

Answer 14

The thymus is the site of T lymphocyte maturation, particularly regulatory T cells

Question 15

Where are follicular dendritic cells located? What is there role?

Answer 15

Follicular dendritic cells are located in the germinal centres of lymph nodes - they capture antigen-antibody complexes which adhere to their dendritic processes, and stimulate the proliferation of B cells

Question 16

What cell-line is involved in the adaptive immune response? What specifically means they do not participate in the innate immune response?

Answer 16

T cells are involved in the adaptive immune response - they aren’t involved in the innate immune response as they require antigen-presentation before they can be activated

Question 17

Which lymphocyte type governs humoral immunity? Which lymphocyte type governs cell-mediated immunity?

Answer 17

B lymphocytes govern humoral immunity

T lymphocytes govern cell-mediated immunity

Question 18

After activation, what does a B lymphocyte differentiate into? What do these secrete?

Answer 18

B lymphocytes differentiate into plasma cells upon activation by an antigen - these plasma cells secrete antibody

Question 19

What cells of the immune response trigger inflammation?

Answer 19

Macrophages and neutrophils

Question 20

What is the term used to describe a disease affecting the lymph node?

Answer 20

A lymphadenopathy

Question 21

What is oedema?

Answer 21

Oedema is swelling caused by fluid retention

Question 22

What attracts a phagocyte (eg a macrophage) to a pathogen?

Answer 22

Opsonisation - the coating of a pathogen with C3b - macrophages contain C3b receptors which draws them to the pathogen

Question 23

What 3 mechanisms do complement activate?

Answer 23

Opsonisation
Inflammation
Membrane-attack complex (cell death)

Question 24

Why type of muscle is a pre-capillary sphincter made of?

Answer 24

Smooth muscle

Question 25

What is lymphoedema?

Answer 25

Swelling as a result of lymph node blockage or obstruction - there is therefore an accumulation of excessive lymph material in this region

Question 26

Is lymphoedema pitting/non-pitting and unilateral/bilateral? Why?

Answer 26

Lymphoedema is:

• non-pitting - the excess fluid has nowhere else to move
• unilateral - it will only swell at the lymph node that has been blocked

Question 27

How might congestive heart failure result in oedema?

Answer 27

Congestive heart failure involves enlargement of the ventricles of the heart as they are not pumping properly - this leads to a build up of blood entering the heart which leads to an increase in pressure within the vessel - this build up of pressure forces fluid out of the vessel

Question 28

What are Starling’s forces?

Answer 28

The relationship between the hydrostatic pressure and oncotic pressure within a capillary and how this affects the fluid (plasma) within it

Question 29

How do Starling’s forces act at the arteriole end of a capillary? State appropriate forces and measurements.

Answer 29

At the arteriole end of a capillary, blood hydrostatic pressure (35mmHg) is greater than the blood colloidal osmotic pressure (25mmHg) so blood plasma and proteins leave the capillaries (net filtration pressure is 10mmHg) and enter the interstitial fluid that bathes the cells

Question 30

How do Starling’s forces act at the venule end of a capillary? State appropriate forces and measurements.

Answer 30

At the venule end of a capillary, blood hydrostatic pressure (15mmHg) is lower than the blood colloidal osmotic pressure (25mmHg) so blood plasma and proteins enter the capillaries (net filtration pressure is -10mmHg) containing CO2 and waste products that require removal

Question 31

Why does oedema often first appear at the ankles?

Answer 31

Gravity causes a vertical gradient where the weight of water governs that it moves to the lower extremities (i.e. the ankles)

Question 32

How do Starling’s forces affect fluid at the central portion of the capillary?

Answer 32

The hydrostatic pressure of the blood (25mmHg) is equal to the blood colloidal oncotic pressure (25mmHg) so there is no net movement of fluid here (net filtration pressure is 0mmHg)

Question 33

If ankle swelling affects only one side of the body, what is the likely implication?

Answer 33

The swelling is not due to a heart problem as this would cause swelling at both ankles

Question 34

Other than oedema, how else might high blood pressure affect the vessels of an individual?

Answer 34

High pressure may cause a rupture in a vessel leading blood to spill into the local tissue, causing skin staining (a brownish hue of the skin)

Question 35

Describe the mechanism behind skin staining.

Answer 35

Red blood cells in local tissue are attacked by phagocytes in an oxidative manner - this involves the conversion of ferrous oxide (with a red colouring) to ferric oxide (with a brown colouring) - this is why skin stain here is usually brown

Question 36

What is the chemical formula for ferric oxide? What colour tinge does this give local skin?

Answer 36

Fe2O3 - this gives skin a brown tinge, as seen in skin staining