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Foundations Exam 2 > Lymphoid System > Flashcards

Lymphoid System Flashcards

1
Q

3 components of secondary lymphoid organs?

A

lymph nodes: filters lymph and returns it to blood via ducts

spleen: filters blood

MALT (mucosal associated lymphoid tissue): counteracts infection

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2
Q

in the stroma of lymphoid tissues and organs, ____ tissue makes up the capsule and trabecula (septum/septa)

A

dense connective tissue (type I collagen)

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3
Q

fill in the blanks regarding lymph flow:
1. blood plasma exits capillaries as ETC tissue fluid, and excess fluid drains to ____ lymph capillaries
2. lymph flows through vessels, which have _____ for unidirectional flow
3. lymph goes through lymph nodes, enters via ____ lymph nodes/ exits via ____ lymph nodes
4. lymph goes through _______
5. lymph enters blood

A
  1. blood plasma exits capillaries as ETC tissue fluid, and excess fluid drains to BLIND ENDED lymph capillaries
  2. lymph flows through vessels, which have VALVES for unidirectional flow
  3. lymph goes through lymph nodes, enters via AFFERENT lymph nodes/ exits via EFFERENT lymph nodes (*Efferent = Exit)
  4. lymph goes through LYMPHATIC DUCTS
  5. lymph enters blood
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4
Q

where does lymph enter blood (2)

A
  1. thoracic duct: returns lymph from right side of body below the diaphragm and ENTIRE LEFT side of body (at left venous angle)
  2. right lymphatic duct: returns lymph from RIGHT side of body above diaphragm (at right venous angle)
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5
Q

left vs right venous angle

A

thoracic duct returns lymph from entire left side of body at left venous angle: junction between left subclavian vein and left internal jugular vein

right lymphatic duct returns lymph from right side of body above diaphragm at right venous angle: junction between right subclavian vein and right internal jugular vein

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6
Q

a patient presents with edema throughout the left side of their body. You suspect a problem with their lymph drainage. What duct may be at fault?

A

thoracic duct; returns lymph from right side of body below diaphragm and entire left side of body at the left venous angle (junction between L subclavian and L internal jugular veins)

*right lymphatic duct only drains right side above diaphragm via right venous angle

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7
Q

lymphangitis

A

inflammation of lymphatic channels that occurs as a result of infection at a site distal to the channel, may spread within hours

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8
Q

the most common initial path for carcinoma cells (epithelial cancers) after detaching from primary site is _____

A

enter lymphatic vessels and become trapped in lymph nodes as secondary (metastatic) cancer site

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9
Q

lymphedema is caused by

A

interrupted lymph drainage

*removal of axillary lymph nodes during mastectomy is common cause of upper limb lymphedema

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10
Q

what is found in the parenchyma of bone marrow?

A

cords: hematopoietic cells

sinuses: mature cells go to circulation

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11
Q

3 places where you find MALT (mucosal associated lymphoid tissue)

A
  1. GALT (gut associated lymphoid tissue): tonsils, Peyer’s patches (ilium), appendix
  2. BALT (breathing associated): respiratory tract
  3. urinary/reproductive tracts

*MALT can be temporary or permanent (tonsils), early line of defense (mostly lymphocytes)

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12
Q

what is found in the nodules/follicles of MALT?

A

located in loose CT, not fully encapsulated

MOSTLY B CELLS (T cells nearby)

can be primary (resting) and secondary (activated)

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13
Q

where are germinal centers found in MALT nodules/follicles

A

secondary (active) nodules/follicles (stain lighter than primary/inactive) with dark mantle zone/corona with inactive B cells

antigen-activated B cells, follicular DC (FDC) rescue antigen-specific B cells from apoptosis

germinal centres remain for weeks after antigen exposure, disappear when infection is cleared

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14
Q

in lymph nodes, active follicles are _____ follicles, NONactive follicles are ____ follicles

A

primary - NONactive

secondary - ACTIVE

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15
Q

what will you find in the cortex, paracortex, and medulla of lymph node parenchyma?

A

cortex:
- sinuses: afferent lymph vessels, subcapsular/marginal sinus, trabecular/paratrabecular sinus
- nodules/follicles: primary and secondary follicles, B CELLS (proliferation with activation), DC, macrophage, plasma cells

paracortex: HEVs (high endothelial venules - lymphocytes exit blood and enter lymph node), T cells

medulla:
- sinuses: macrophages, reticular cells, efferent lymph vessels
- cords: macrophages, DC, lymphocytes, plasma cells

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16
Q

where in lymph node parenchyma can you find afferent lymph vessels? (be specific)

A

sinuses of cortex have AFFERENT lymph vessels

[sinuses of medulla have efferent lymph vessels, efferent = exit]

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17
Q

where (specifically) in lymph node parenchyma can lymphocytes exit blood and enter lymph node?

A

HEV (high endothelial venules) in paracortex

you will find mainly T cells in paracortex

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18
Q

where can reticular cells be found in lymph node parenchyma?

A

in the medullary sinuses, along with macrophages and efferent lymph vessels

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19
Q

HEVs and location

A

high endothelial vessels, where lymphocytes can exit blood and enter lymph nodes

found in paracortex of lymph node parenchyma

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20
Q

where can you find subcapsular/marginal sinuses and trabecular/paratrabecular sinuses?

A

in the sinuses of the cortex of lymph nodes, along with afferent lymph vessels

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21
Q

lymph node follicles are found in the _____

lymph node cords are found in the ______

A

follicles/nodules are in cortex

cords are in medulla

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22
Q

in DiGeorge syndrome, the thymus is not well developed. What effect does this have on lymph node parenchyma?

A

T cells mature in the thymus

if the thymus is not well-developed, T cells can’t develop well

if T cells can’t develop well, they can’t populate the paracortex of lymph nodes

therefore the paracortex of lymph nodes is also not well developed

23
Q

in viral infections, an extreme immune response is sometimes induced that causes hyperplasia of the _____ of lymph nodes

A

paracortex - contains HEVs (for lymphocyte entry from blood) and population of T cells

24
Q

the connective tissue capsule of lymph nodes continues/protrudes internally as ____

A

trabeculum - makes sort of dividers between pie slices

25
Q

blood vessels and the efferent [exit] lymphatic vessel are found at the ____ of lymph nodes

A

hilum (stalk)

26
Q

describe the journey of lymphocytes through lymph nodes

A

travel via sinuses (discontinuous, porous endothelium with reticular connective tissue)

  1. afferent lymph vessel (afferent = arrive)
  2. subcapsular (beneath the capsule) sinus
  3. trabecular sinus (remember that trabeculum are continuation of capsule)
  4. medullary sinus (within medulla, which = middle)
  5. efferent (exiting) lymph vessels
27
Q

the outer dense connective tissue (note that it is fragile, though) capsule of the spleen continues internally as ____

A

trabecula

28
Q

which of these are TRUE regarding the spleen?
a. contains reticular fibers
b. is divided by cortex and medulla
c. contains a hilum through which blood vessels enter and exit
d. is encapsulated by dense CT that continues internally as trabeculum

A

spleen:
a. contains reticular fibers
c. contains hilum
d. capsule of dense CT continues internally as trabecula/trabeculum (same thing)
*parechyma is organized into pulps

lymph nodes:
- CT capsule continues inwards as trabeculum
- cortex, paracortex, medulla
- also contains reticular fibers and hilum

29
Q

how is splenic parenchyma organized?

A

pulps:
- white pulp (WBC): PALS (periarteriolar lymphoid sheath), nodules

  • red pulp (RBC): sinusoids/sinuses and cords (of Bilroth)
30
Q

what can be found in the white pulp of the spleen (specifically)?

A

PALS (periarteriolar lymphoid sheath): surrounds center arteriole, T cells

nodules: resting or activated follicles, B cells, DC, macrophage, plasma cells

*remember that white pulp is WBC, so its function is immune response to blood-borne antigens

31
Q

what will you find (specifically) in red pulp of spleen parenchyma?

A

sinusoids/sinuses: capillaries with endothelial cell slits, contain macrophages

cords of Bilroth: RBCs, DC, granulocytes, lymphocytes, plasma cells, macrophages with hemosiderin (brown pigment because they have taken up old RBC)

*remember that the role of red pulp in spleen is to remove old RBCs

32
Q

where will you find cords of Bilroth

A

red pulp of the spleen

contains RBCs, DC, granulocytes, lymphocytes, plasma cells, and macrophages with hemosiderin (because they have take up old RBCs)

[also in red pulp are sinusoids/sinuses]

33
Q

where in the spleen will you find:
a. T cells
b. hemosiderin-laden macrophages

A

T cells make up PALS of white pulp (periarteriolar lymphoid sheath, because it surrounds central arteriole)

hemosiderin-laden macrophages are in CORDS OF BILROTH of red pulp (have brown pigment because they cells have taken up old RBC and are degrading them)

34
Q

where are immune responses initiated in the spleen?

A

the marginal zone, between the red and white pulp

35
Q

is splenic circulation in humans open or closed?

A

in humans splenic circulation is open - not all blood goes directly from arterioles into sinuses, most goes right onto cords of spleen

macrophages in cords sample blood and filter it

surviving blood passes through into sinus, then leaves via splenic veins

36
Q

A 7yo pt with Hx of sickle cell disease is admitted with LUQ abdominal pain and tachycardia. Hemoglobin levels are low, spleen is easily palpated below L costal margin.

You recognize that the patient is experiencing splenic sequestration crisis. Explain

A

sickle RBCs pool in the spleen and cause painful splenomegaly

Remember that in the spleen of humans, there is open circulation so most blood goes over cords and is sampled by macrophages before returning to sinus and leaving via veins. The slits in the endothelium are small, so sickle cells could get stuck here

37
Q

where is the thymus located anatomically

A

found in thorax, in the anterior mediastinum, posterior to the sternum

38
Q

what happens to the thymus with age (how is tissue changed?)

A

in children, thymus is mostly T cells

with age, thymus becomes fatty

39
Q

ectopic thymus

A

thymus forms in head/neck region and migrates,

but sometimes some of it is left behind, resulting in ectopic thymus

40
Q

how can you tell if you’re looking at a histology image of a child’s thymus?

A

not a lot of adipose (an adult’s would have more fatty tissue)

41
Q

describe structure of thymus

A
  • 2 lobes (R/L)
  • cortex and medulla
  • outer capsule, continues inwards as trabeculum

*however, trabeculum only partially divides lobes into lobules

*NO nodules in cortex - distinguishes thymus from lymph node (don’t want B cells here - you do not want an immune reaction against developing T cells)

42
Q

how can you histologically differentiate between thymus and lymph nodes? what is the significance of this difference?

A

thymus does NOT have nodules in cortex - you do NOT want a B cell immune reaction against developing T cells (remember that T cells become immunocompetent in the thymus)

lymph nodes have nodules in their cortex

43
Q

are there more T cells in the cortex or medulla of the thymus

A

cortex > medulla

44
Q

where can epithelial reticular cells be found in the thymus?

describe them

A

cortex AND medulla

  • stellate/star shaped
  • connected via desmosomes
  • provide support, secretions, barrier from blood

*** in the medulla, reticular cells form Hassall’s corpuscles (accumulate with age)

45
Q

where does T cell selection occur in the thymus

A

CORTEX

46
Q

Hassall’s corpuscles

A

formed by epithelial reticular cells in the MEDULLA of the THYMUS (look like whorls)

accumulate with age

aka thymic corpuscles

47
Q

why is it important that there is a blood-thymus barrier?

A

what to protect developing T cells from immune reaction

contains:
- continuous capillary endothelium held together with tight junctions
- basement membrane
- perivascular CT
- basement membrane with desmosomes

48
Q

what genetic mutation causes DiGeorge syndrome, and how does it manifest?

A

22q11 deletion —> DiGeorge syndrome (velocardiofacial)

remember Catch 22
Cleft palate
Abnormal face
Thymic aplasia
Cardiac defects
Hypocalcemia
22 gene segment deletion

thymic aplasia epithelial reticular cells don’t form properly in thymus —> immunodeficiency because T cells are not forming —> NO T CELLS in thymus-dependent zones (such as paracortex of lymph node, PALS of white pulp of spleen - wherever you’re supposed to see T cells)

49
Q

do primary lymphoid organs contain nodules?

A

NO

do not want an immune response triggered in bone marrow and thymus, where B/T cells are developing

*secondary lymphoid organs, whose job it is to produce immune response, contain nodules

50
Q

how is parenchyma of tonsils organized

A

crypts

partial capsule of loose CT

51
Q

which lymphoid organs are encapsulated by reticular CT?

A

bone marrow (primary)
lymph nodes and spleen (secondary)

[all others have loose CT]

52
Q

where do immunocompetent T cells exit the thymus?

A

corticomedullary junction

53
Q

open circulation in the spleen occurs where blood cells pass from ____ into ____

A

capillaries into cords

then squeeze through endothelial slits to reach sinuses for exit

54
Q

what are the T-dependent zones of the lymphoid system?

A
  1. paracortex of lymph nodes
  2. PALS of splenic white pulp

Foundations Exam 2 (42 decks)

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