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IMS > W7- Lecture 33- Lymphatic system > Flashcards

W7- Lecture 33- Lymphatic system Flashcards

1
Q

what are the two parts of the circulatory system ?

A

cardiovascular & lymphatic

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2
Q

name the three major components of the lymphatic system

+ purpose

A

Extensive network of capillaries & collecting vessels: receive fluid from loose connective tissues throughout body and transport to CV system

Lymph Nodes: filter fluid in collecting vessels

Lymphoid organs: include lymphatic nodules, tonsils, spleen & thymus

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3
Q

what does a build up of interstitial fluid lead to?

A

oedema

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4
Q

Lymphatic Vessel Types

A

Capillarys form Collecting Vessel from Trunks form Ducts

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5
Q

you find Lymph capillaries occur alongside blood capillaries aside from ?

A

bone, bone marrow, teeth, and entire central nervous system

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6
Q

compare Lymphatic Vessels to capillaries

A

Like blood capillaries but very permeable.
Two unique structural modifications:
Endothelial cells loosely overlap, open easily, create mini-valves.
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.

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7
Q

what are lacteals

A

Highly specialised 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.

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8
Q

compare Collecting Vessels to veins

A 
Collecting Vessels
Three tunics like veins, but:
Thin-walled
More internal valves
More anastomosing(branching )
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9
Q

where do the Larger lymphatic vessels receive blood supply from?

A

vasa vasorum.

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10
Q

which vessels do the collecting vessels in the skin travel with ?

which vessels do the deep lymphatics travel with ?

A

superficial veins

deep arteries

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11
Q

what are the purpose of lymphatic trunks?

A

Drain large areas of body
(named after areas drained
e.g. paired lumbar, bronchomediastinal, subclavian and jugular trunks, single intestinal trunk.)

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12
Q

how are lymphatic trunks formed ?

A

Capillaries collect into vessels which form lymphatic trunks

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13
Q

how are lymphatic ducts formed ?

A

lymphatic trunks form lymphatic ducts

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14
Q

describe the location that the right lymphatic duct empties into

+ what it drains

A

empties at junction of right internal jugular and right subclavian veins

+right arm, thorax

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15
Q

describe the location that the thoracic duct empties into

A

into junction of left internal jugular and left subclavian veins

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16
Q

describe the location that the cisterna chyli empties into

A

most inferior part of the thoracic duct

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17
Q

what actions enable lymph transport ?

A

Milking action of muscles;
Breathing-induced pressure changes in thorax;
Use of valves;
Rhythmic contractions of smooth muscle in the trunks and ducts.

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18
Q

what Lymphoid Tissue is important ?

/why

A

of loose connective tissue (aka reticular connective tissue) in all L. organs except the thymus.

Macrophages live on the fibres & lymphocytes reside temporarily in spaces

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19
Q

describe how Lymphoid tissue is “packaged” in different ways

A

Diffuse - in most body organs especially in mucous membranes & in lymphoid organs.

Follicles/Nodules - solid, tightly packed, spherical bodies with centres (germinal centres via clonal selection ) containing B cells.

Usually found within organs e.g. lymph nodes but also singly in intestine (Peyer’s Patches).

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20
Q

why does more fluid leaves capillaries than enters them?

how much is left per day ?

A

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

Most is reabsorbed at the venous end, but more than 3 L/day remains

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21
Q

name three places where lymphatic vessels converge to form trunks

A

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

22
Q

describe the importance of trabeculae in lymph nodes?

A

divide node into compartments. Provides stroma of support for ever changing resident lymphatic cells. phagocytes an act on them . and divides lymphnode into two distinct regions outer Cortex & inner Medulla. major site of filtration.

23
Q

what are trabeculae?

A

Fibrous capsules and some bits extent into centre of centre of lymph node

24
Q

describe the cortex of a lymph node

A

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

25
Q

describe the medulla of a lymph node

A

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

26
Q

what structure difference enables more time for immune surveillance?
where ?

A

More vessels coming in then out – slows down fluid. Passes through many nodes before returning back to cardiovascular system

less at the hilus

27
Q

what cells trap antigens in the lymph nodes ?

A

Macrophages and dendritic cells trap antigens

28
Q

describe b cell proliferation in lymph nodes after activation

A

Outer cortex – nodules that contain B cells
1 recognition
2 interaction with helper T cells

In the dark zone B cells proliferate undergo clinal selection
Only those that can attach to antigens
If b cell doesn’t receive help from t cell it undergoes apoptosis

29
Q

what happens when b cells move from the dark zone (aka germinal centre ) to the basal light zone

A

positive selection for binding to antigen on follicular dendritic cells

30
Q

describe the structure of Lymph Sinuses

A

Spanned by reticular fibres with resident macrophages, enter the nodes, and phagocytose foreign material. Some leakage of antigens into surrounding reticular tissue that activate lymphocytes.

31
Q

what is the only lymphoid tissue that filters lymph?

A

Lymph Nodes

32
Q

what side of the lymph nodes do the afferent lymphatic vessels enter ?

A

convex side

33
Q

what sinus does the lymph pass through that helps it pass from the ’ cortex to medulla

A

the sub-capsular sinus

34
Q

describe the spleen

A

Largest lymphoid organ; soft, blood-rich organ, fist size Located on left abdomen under diaphragm. Served by large splenic artery & Saphenous vein that enter hilus on concave side.

35
Q

what are the functions of the spleen ?

A

Lymphocyte proliferation & immune surveillance/ response
Cleans blood e.g. remove old RBC/platelets, bacteria, virus, foreign matter, debris, toxins etc.
Storage of red blood cell constituents and release of others to liver
Stores platelets
Site of RBC production in foetus

36
Q

what are the two distinct areas caused by Trabeculae in the spleen ?

A

Areas of L on reticular fibres: white pulp and form “cuffs” around central arteries.

Areas of red cells, venous sinus, splenic cords, and red pulp. Dispose of effete red blood cells and pathogens.

37
Q

what place in the spleen does RBC degradation take place?

A

Splenic chord

38
Q

which cells help the degradation of RBC in the spleen ?

A

Macrophages help break down damaged RBC

39
Q

what is the thymus

+ structure

A

Primary lymphoid organ
Largest as a child
Secretes thymosin, thymopentin to make T L immunocompetent.

structure: thymic lobules each with outer cortex and inner medulla.

Dark-staining cortex Rapidly dividing, densely packed lymphocytes and few macrophages.

Light-staining medulla: fewer lymphocytes, contains bizarre-shaped structures

Hassal’s or thymic corpuscles – responsible for the conversion of self-reactive T-lymphocytes into suppressive T-lymphocytes.

40
Q

describe Hassal’s or thymic corpuscles

A

In medulla of thymus
Increased number of epithelial cells that
1provide support to the medulla
2 help negatively select reactive T cells to generate tolerance against self antigens

41
Q

how does the thymus differ from other lymphoid organs (2)

A

Functions only in T-cell maturation, does not fight antigens directly - blood-thymus barrier - prevents premature activation of immature lymphocytes.

Stroma (framework) consists of star-shaped epithelial cells, not reticular cells, which aid lymphocytes by secreting stimulating hormones

42
Q

describe the steps of t cell maturation

A

please see diagram -
1 Rag caused shuffling of DNA – production of random T cell receptors produced
(recombinases )
2 Binding event occurs(Positive selection )
Binding leads to survival of cells
3 Regulation up/down of cd4 /cd8.
4 Cells bind of MHC 1 or 2 class molecules (negative selection )
If it does react cell undergoes apoptosis

43
Q

name the four types of tonsils

+ where they are located

A

1) Palatine:, largest tonsils and are located on either side of posterior end of oral cavity. Most often infected.
2) Lingual: Located at base of tongue
3) Pharyngeal: (adenoids) in posterior wall of nasopharynx.
4) Tubal: surround opening of auditory tubes into pharynx.

44
Q

describe what a tonsil is

A

Simplest lymphoid organs - ring of tissue around entrance to throat (pharynx). Part encapsulated as swellings in mucosa

Gather/remove pathogens entering in inhaled air/food

45
Q

what takes place in the pits of tonsils?

A

immune surveillance + formation of memory cells

46
Q

describe the germinal centre in the tonsils

A

immune surveillance + formation of memory cells

47
Q

describe the describe the germinal centre in the tonsils of the tonsils

A

Covered by squamous epithelium that invaginates deep into tonsil to form blind-ended crypts that trap bacteria & particles.
Bacteria killed in lymphoid tissue.
Produces ‘memory’ immune cells.

48
Q

what are Peyer’s Patches?

A

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

49
Q

where can you find an aggregate of Lymph Nodules?

A

Appendix & Peyer’s Patches

50
Q

describe what the Appendix & Peyer’s Patches do

A

Destroy bacteria (many in gut)

Generate memory Lymphocytes for long-term immunity.

Mucus associated lymph tissue for respiratory and digestive tract protection.

51
Q

where is the Peyer’s Patches placed ?

important for ?

A

close to the lumen of the ileum and the germinal centre where B-cells proliferate.
Important for anti-microbial, antibody production.

IMS (74 decks)

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