Immunology- The lymphatic system

Question 1

What is the lymphatic system?

Answer 1

Closely related in both structure & function to CV system. Forms basis of Immune System.

Question 2

What 3 components are apart of the lymphatic system?

Answer 2

1) Extensive network of capillaries & collecting vessels: receive fluid from loose connective tissues throughout body and transport to CV system
2) Lymph Nodes: filter fluid in collecting vessels
3) Lymphoid organs: include lymphatic nodules, tonsils, spleen & thymus

Question 3

What is oedema?

Answer 3

Unchecked, this build-up of plasma proteins would lead to oedema.

Question 4

Plasma proteins can not re enter the capillaries so where do they go?

Answer 4

enter lymphatic vessels

Question 5

Define lymphatics?

Answer 5

interstitial fluid in lymphatics: lymph

One-way system of lymph flow to heart, which begins in tiny, blind-ended lymph capillaries.

Question 6

Name the lymphatic vessel types?

Answer 6

Capillary
Collecting Vessel
Trunk
Duct

Question 7

In the lymphatic vessels what occurs at the arterial ends of the capillaries?

Answer 7

Hydrostatic & osmotic pressures at arterial ends of capillary beds force fluids, with plasma proteins, into interstitial space.

Question 8

What occurs at the venous end in the lymphatic vessels?

Answer 8

Most is reabsorbed at the venous end, but increased 3 L/day remains & needs to be returned to blood.

Question 9

Where do lymph capillaries occur alongside and what is not?

Answer 9

Lymph capillaries occur alongside blood capillaries except: bone, bone marrow, teeth, and entire CNS

Question 10

Define lymphatic capillaries?

Answer 10

Like blood capillaries but v. permeable.

Question 11

What are the 2 unique structural modifications in capillaries?

Answer 11

1) Endothelial cells loosely overlap, open easily, create mini-valves.
2) Endothelial cells anchored to surrounding structures by fine filaments that separate with  interstitial fluid volume. Expose gaps in capillary wall but close if fluid pressure is > inside capillary, preventing leakage.

Question 12

Define inflammation the lymph capillaries?

Answer 12

Lymph capillaries take up large particles eg. debris, pathogens, cells.

Question 13

What is a lacteals?

Answer 13

Highly specialized lymph capillaries in villi of intestinal mucosa. Lymph here is milky white rather than clear as it contains digested intestinal fats and is aka chyle.

Question 14

What are the collecting vessels in the lymphatic system?

Answer 14

3 tunics like veins

Question 15

How do tunic veins differ form normal veins?

Answer 15

a) thin-walled
b) more internal valves,
c) more anastomosing.

Question 16

Which lymphatic vessels receive blood supply from vasa vasorum?

Answer 16

Larger lymphatic vessels receive blood supply from vasa vasorum.

Question 17

Where do collecting vessles in the skin travel?

Answer 17

Collecting vessels in skin travel with superficial veins.

Deep lymphatics travel with deep arteries

Question 18

What does the lymphatic trunk?

Answer 18

Drain large areas of body; named after areas drained eg. paired lumbar, bronchomediastinal, subclavian and jugular trunks, single intestinal trunk.

Question 19

What are the two lymphatic ducts?

Answer 19

Right lymphatic duct

Thoracic Duct

Question 20

What does the right lymphatic duct do?

Answer 20

drains lymph from right upper arm, right side of head and thorax.

Question 21

What does the thoracic duct do?

Answer 21

Much larger, arises from cisterna chyli (enlarged sac), drains rest of body.

Question 22

Where does the 2 lymphatic ducts drain into?

Answer 22

Each duct empties lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein.

Question 23

The lymph transport have the same mechanism as veins what are these?

Answer 23

milking action of muscles;
breathing-induced pressure changes in thorax;
use of valves;
rhythmic contractions of smooth muscle in the trunks and ducts.

Question 24

Define the lymphoid tissue?

Answer 24

Important component of Immune Tissue Is a type of loose connective tissue (aka reticular connective tissue) in all L. organs except the thymus.

Question 25

What are the 2 different ways lymphoid tissues are packaged?

Answer 25

1) Diffuse - in most body organs esp. in mucous membranes & in lymphoid organs.
2) Follicles/Nodules – solid, tightly packed, spherical bodies with centres (germinal centres) containing B cells. Usually found within organs eg. lymph nodes but also singly in intestine (Peyer’s Patches).

Question 26

What is the lymph nodes function?

Answer 26

On way to bloodstream, lymph is filtered through LN that cluster along the lymphatic vessels of the body. Provide protective function via phagocytes and also activate Immune System.

Question 27

Define what cluster means ?

Answer 27

Cluster where lymphatic vessels converge to form trunks

eg. groin (inguinal), Arm pit (axillary), neck (cervical)

Question 28

Define the cortex?

Answer 28

Cortex: Contains densely-packed follicles, many with germinal centres. Dendritic cells wrap around follicles to separate from transit T-cell rich interspaces.T cells circulate between blood, lymph and LNs for immune surveillance

Question 29

Define the medulla?

Answer 29

Contains cords inward extensions of the cortex which contain Ls and plasma cells

Question 30

What are lymph sinuses?

Answer 30

spanned by reticular fibres with resident M, enter the nodes, and phagocytose foreign material. Some leakage of antigens into surrounding reticular tissue that activate L.

Question 31

What is the only lymphoid tissue the filter lymph?

Answer 31

LN

Question 32

What are the lymphoid organs?

Answer 32

Spleen

Thymus

Question 33

Define the Spleen?

Answer 33

Largest L. organ; soft, blood-rich organ, fist size Located on left abdomen under diaphragm. Served by largesplenic artery & S. vein that enter hilus on concave side.

Question 34

What are the function of the spleen?

Answer 34

Functions:

1) L proliferation & immune surveillance/ response
2) Cleans blood eg. remove old RBC/platelets, bacteria, virus, foreign matter, debris, toxins etc.
3) Storage of RBC constituents and release of others to liver
4) Stores platelets
5) Site of RBC production in fetus

Question 35

Define the thymus?

Answer 35

Bilobular organ located in lower neck, prominent in early life. Secretes thymosin, thymopentin to make T L immunocompetent.

Question 36

How does the thymus change with age?

Answer 36

Prominent in newborns, increases in size and is most active in childhood, begins to atrophy in adolescence. Is replaced by fibrous and fatty tissue in old age.

Question 37

How does the thymus differ from other lymphoid organs?

Answer 37

1) Functions only in T cell maturation, does not fight antigens directly - blood-thymus barrier - prevents premature activation of immature L
2) Stroma (framework) consists of star-shaped epithelial cells, not reticular cells, which aid L by secreting stimulating hormones

Question 38

Whats the simplest lymphoid organ?

Answer 38

Tonsils

Question 39

What are the different locations of the tonsils?

Answer 39

1) Palatine:
2) Lingual:
3) Pharyngeal:
4) Tubal:

Question 40

Define Palatine?

Answer 40

Palatine:, largest tonsils and are located on either side of posterior end of oral cavity. Most often infected.

Question 41

Define Lingual?

Answer 41

Lingual: Located at base of tongue

Question 42

Define Pharyngeal?

Answer 42

Pharyngeal: (adenoids) in posterior wall of nasopharynx.

Question 43

Define Tubal?

Answer 43

Tubal: surround opening of auditory tubes into pharynx.

Question 44

Define the exterior surface of the tonsils ?

Answer 44

Exterior surface: Covered by squamous epithelium that invaginates deep into tonsil to form blind-ended crypts that trap bacteria & particles.

Question 45

What happens with the bacteria killed in the lymphatic tissue?

Answer 45

Produces ‘memory’ immune cells.

Question 46

What aggregates of lymphoid nodules?

Answer 46

Peyer’s Patches

Appendix

Question 47

Define Peyer’s Patches?

Answer 47

Large isolated clusters of nodules similar to tonsil, located in wall of ileum

Question 48

What do peyer patches and appendix are in a good position to:

Answer 48

1) destroy bacteria (many in gut)
2) generate memory L for long-term immunity.
3) MALT -for respiratory and digestive tract protection.