L18 Lymphatic System Flashcards
What are the lymphoid organs?
Lymphatic nodules, tonsils, spleen, and thymus
Which of the following is the correct sequence?
a) capillary - duct - trunk - collecting vessel
b) collecting vessel - capillary - trunk - duct
c) capillary - collecting vessel - trunk - duct
d) duct - capillary - collecting vessel - trunk
c) capillary - collecting vessel - trunk - duct
Lymph capillaries generally occur alongside blood capillaries. Where would this NOT be the case?
Bone, bone marrow, teeth, and the entire CNS
Lymph capillaries and blood capillaries are very similar. In what 2 ways are the lymph capillaries structurally unique?
1) Permeability: endothelial cells loosely overlap, open easily, create mini-valves. If pressure inside capillary is lower than outside, the pores open. If pressure inside is greater than outside, the pores close to prevent leakage.
2) Filaments: Endothelial cells are anchored to surrounding structures by fine filaments.
What is chyle?
Chyle is a kind of lymph found in lacteals. It is milky white rather than clear because it contains digested intestinal fats.
What are lacteals?
Lacteals are highly specialized lymph capillaries in villi of intestinal mucosa.
They contain chyle.
True or false, lymphatic collecting vessels have 3 tunics.
True.
They are structurally similar to veins, but they are thin-walled, they have more internal valves, and they are more anastomosing.
Do lymphatic vessels have a blood supply?
Yes, larger lymphatic vessels receive blood supply from vasa vasorum. It is a shared supply with the cardiovascular vessels, not their own independent supply.
Collecting vessels in the skin travel with __1__. Deep lymphatics travel with __2__.
1) superficial veins
2) deep arteries
What are lymphatic trunks?
They drain large areas of the body,
e.g. lumbar, bronchomediastinal, subclavian, and jugular trunks. Single intestinal trunk.
What are the two lymphatic ducts called?
1) Right lymphatic duct
(drains right upper arm, right side of head, thorax)
2) Thoracic duct
(drains rest of body, arises from cisterna chyli)
Where do the lymphatic ducts meet the venous circulation?
Each duct empties lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein.
Where are macrophages found in lymphoid tissue?
Macrophages live on the reticular fibres.
Reticular fibres are like branches of trees. Macrophages sit like birds on the twigs of the branches.
Lymphoid tissue can be “packaged” in different ways.
In most body organs (esp. in mucous membranes and lymphoid organs) it is __1__.
It can also be found as __2__ or nodules, which are solid, tightly packed, spherical bodies with centres. These centres are called __3__ and contain __4__. They can be found singly within the intestine, where they are known as __5__.
1) diffuse
2) follicles
3) germinal centres
4) B-cells
5) Peyer’s Patches
What are germinal centres?
Centre of a lymphoid follicle/nodule. Germinal centres contain B cells.
What are Peyer’s Patches?
Large isolated clusters of nodules similar to tonsil, located in wall of ileum (intestine)
What are the 2 regions of a lymph node?
Outer cortex and inner medulla.
Describe the cortex of a lymph node.
Outer region of the LN: 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
Describe the medulla of a lymph node.
Contains cords (inward extensions of the cortex) which contain Ls and plasma cells
Describe the spleen.
Largest L. organ; soft, blood-rich organ, fist size Located on left abdomen under diaphragm.
Thin capsule with Trabeculae, contains lymphocytes & macrophages.
Served by large splenic artery & S. vein that enter hilus on concave side.
What are the functions of the spleen?
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
Where do you find red pulp and white pulp?
In the spleen:
2 distinct areas:
1) Areas of L on reticular fibers: white pulp and form “cuffs” around central arteries.
2) Areas of red cells, venous sinus, splenic cords, and red pulp. Dispose of effete RBC and pathogens
How do T lymphocytes become mature/immunocompetent?
The thymus secretes thymosin and thymopentin to mature the T cells.
What is the structure of the thymus?
It’s like a cauliflower head, each floret is a thymic lobule - each one with it’s own cortex and inner medulla.
