Immunology- The lymphatic system Flashcards
What is the lymphatic system?
Closely related in both structure & function to CV system. Forms basis of Immune System.
What 3 components are apart of the lymphatic system?
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
What is oedema?
Unchecked, this build-up of plasma proteins would lead to oedema.
Plasma proteins can not re enter the capillaries so where do they go?
enter lymphatic vessels
Define lymphatics?
interstitial fluid in lymphatics: lymph
One-way system of lymph flow to heart, which begins in tiny, blind-ended lymph capillaries.
Name the lymphatic vessel types?
Capillary
Collecting Vessel
Trunk
Duct
In the lymphatic vessels what occurs at the arterial ends of the capillaries?
Hydrostatic & osmotic pressures at arterial ends of capillary beds force fluids, with plasma proteins, into interstitial space.
What occurs at the venous end in the lymphatic vessels?
Most is reabsorbed at the venous end, but increased 3 L/day remains & needs to be returned to blood.
Where do lymph capillaries occur alongside and what is not?
Lymph capillaries occur alongside blood capillaries except: bone, bone marrow, teeth, and entire CNS
Define lymphatic capillaries?
Like blood capillaries but v. permeable.
What are the 2 unique structural modifications in capillaries?
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.
Define inflammation the lymph capillaries?
Lymph capillaries take up large particles eg. debris, pathogens, cells.
What is a lacteals?
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.
What are the collecting vessels in the lymphatic system?
3 tunics like veins
How do tunic veins differ form normal veins?
a) thin-walled
b) more internal valves,
c) more anastomosing.
Which lymphatic vessels receive blood supply from vasa vasorum?
Larger lymphatic vessels receive blood supply from vasa vasorum.
Where do collecting vessles in the skin travel?
Collecting vessels in skin travel with superficial veins.
Deep lymphatics travel with deep arteries
What does the lymphatic trunk?
Drain large areas of body; named after areas drained eg. paired lumbar, bronchomediastinal, subclavian and jugular trunks, single intestinal trunk.
What are the two lymphatic ducts?
Right lymphatic duct
Thoracic Duct
What does the right lymphatic duct do?
drains lymph from right upper arm, right side of head and thorax.
What does the thoracic duct do?
Much larger, arises from cisterna chyli (enlarged sac), drains rest of body.
Where does the 2 lymphatic ducts drain into?
Each duct empties lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein.
The lymph transport have the same mechanism as veins what are these?
milking action of muscles;
breathing-induced pressure changes in thorax;
use of valves;
rhythmic contractions of smooth muscle in the trunks and ducts.
Define the lymphoid tissue?
Important component of Immune Tissue Is a type of loose connective tissue (aka reticular connective tissue) in all L. organs except the thymus.
What are the 2 different ways lymphoid tissues are packaged?
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).
What is the lymph nodes function?
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.
Define what cluster means ?
Cluster where lymphatic vessels converge to form trunks
eg. groin (inguinal), Arm pit (axillary), neck (cervical)
Define the cortex?
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
Define the medulla?
Contains cords inward extensions of the cortex which contain Ls and plasma cells
What are lymph sinuses?
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.
What is the only lymphoid tissue the filter lymph?
LN
What are the lymphoid organs?
Spleen
Thymus
Define the Spleen?
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.
What are the function of the spleen?
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
Define the thymus?
Bilobular organ located in lower neck, prominent in early life. Secretes thymosin, thymopentin to make T L immunocompetent.
How does the thymus change with age?
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.
How does the thymus differ from other lymphoid organs?
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
Whats the simplest lymphoid organ?
Tonsils
What are the different locations of the tonsils?
1) Palatine:
2) Lingual:
3) Pharyngeal:
4) Tubal:
Define Palatine?
Palatine:, largest tonsils and are located on either side of posterior end of oral cavity. Most often infected.
Define Lingual?
Lingual: Located at base of tongue
Define Pharyngeal?
Pharyngeal: (adenoids) in posterior wall of nasopharynx.
Define Tubal?
Tubal: surround opening of auditory tubes into pharynx.
Define the exterior surface of the tonsils ?
Exterior surface: Covered by squamous epithelium that invaginates deep into tonsil to form blind-ended crypts that trap bacteria & particles.
What happens with the bacteria killed in the lymphatic tissue?
Produces ‘memory’ immune cells.
What aggregates of lymphoid nodules?
Peyer’s Patches
Appendix
Define Peyer’s Patches?
Large isolated clusters of nodules similar to tonsil, located in wall of ileum
What do peyer patches and appendix are in a good position to:
1) destroy bacteria (many in gut)
2) generate memory L for long-term immunity.
3) MALT -for respiratory and digestive tract protection.
