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OrganHisto Exam One > Chapter Three - Thymus & Spleen > Flashcards

Chapter Three - Thymus & Spleen Flashcards

0
Q

At what age do we see that little functioning of the thymus is left?

A

About 25 years of age

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1
Q

Is the thymus a primary or secondary lymphoid organ?

A

Primary

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2
Q

Is the thymus larger in a child or an adult?

A

Child

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3
Q

When does involution of the thymus begin?

A

After puberty

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4
Q

What is the pattern of the involution process of the thymus?

A

1st - septa
2nd - cortex
3rd - medulla

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5
Q

What is the important function of the thymus?

A

Establish immunocompetent T cells

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6
Q

What two steps are involved in the thymus establishing immunocompetent T cells?

A

Being able to distinguish self from non self antigens and to develop self-tolerance

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7
Q

What is a thymocyte?

A

T lymphoblast in the thymus

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8
Q

What makes up the thin capsule of the thymus?

A

Dense irregular connective tissue

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9
Q

What makes up the lobules of the thymus?

A

Peripheral cortex and a central medulla

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10
Q

What is the term for the support tissue of the thymus?

A

Stroma

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11
Q

What makes up the stroma of the thymus?

A

Capsule, septa, adipose, microstroma

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12
Q

What is the microstroma of the thymus?

A

Thymic epithelial cells (TECs)

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13
Q

What is another name for thymic epithelial cells?

A

Epithelioreticular cells or epithelial reticular cells

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14
Q

How many types of TECs are there?

A

6

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15
Q

What are the functions of the thymic epithelial cells?

A

Support using cytoplasmic processes (NOT reticular fibers), secrete thymic hormones and cytokines, form thymic corpuscles (Hassall’s bodies), important component to the blood-thymic barrier, function as an APC

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16
Q

What are the functions of the hormones and cytokines that can be secreted by TECs?

A

Influence T cell maturation, division, and activities (immunity elsewhere in the body too)

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17
Q

What type of TEC are the thymic corpuscles (Hassell’s bodies)?

A

Type VI

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18
Q

Where can thymic corpuscles be found?

A

In the medulla

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19
Q

What is the function of the thymic corpuscles?

A

Secrete cytokines to influence local dendritic cells and the development of some T cells

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20
Q

What type of TEC is found in the blood-thymic barrier?

A

TEC type I

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21
Q

What makes up the perivascular component of the blood-thymic barrier?

A

Connective tissue with many macrophage to destroy foreign molecules

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22
Q

What is the function of the blood-thymic barrier?

A

To prevent T cells from physically contacting foreign antigens

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23
Q

What part of the thymus contains a high cell concentration?

A

Cortex

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24
Q

What cells make up the cortex of the thymus?

A

T lymphocytes, macrophages, TEC types I, II, and III

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25
Q

What part of the thymus contains a lower cell density?

A

Medulla

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26
Q

Where are T lymphoblasts produced?

A

Bone marrow

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27
Q

What cell types are found in the medulla of the thymus?

A

Fewer but large T cells, macrophages, dendritic cells (APC), and TEC types IV, V, and VI

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28
Q

When the T lymphocytes first enter the thymus, are they immunocompetent?

A

No; they are immunoINcompetent

29
Q

Where do the T lymphocytes leave the bloodstream?

A

At the corticomedullary line

30
Q

Where do T cells migrate to divide and are tested through the positive selection process?

A

Periphery of the cortex

31
Q

What happens to the 98% of T cells that fail the selection process in the cortex of the thymus?

A

Apoptotic death

32
Q

Where do the surviving T cells from the cortex of the thymus migrate to?

A

Back to the medulla

33
Q

T cells that continue the maturation process after the selection process in the cortex of the thymus go through the negative selection process to become what kind of cells?

A

Cytotoxic (killer) or helper T cells

34
Q

What three things do we lack in the thymus?

A

Afferent lymph vessels, reticular fibers, reticular cells

35
Q

Why do we lack afferent lymph vessels in the thymus?

A

Unwanted debris and foreign antigens that come with afferent vessels

36
Q

What are the functions of the spleen?

A

Immunity, blood filtration using macrophages, long term T cell storage, stores some WBCs and platelets, hemopoietic organ in fetus

37
Q

Large numbers of what kind of WBC are specifically found in the spleen?

A

Monocytes

38
Q

What is the capsule of the spleen made of?

A

Thick dense irregular fibroelastic connective tissue

39
Q

What is the convex surface and concave area of the spleen called?

A

Hilum

40
Q

What are the trabeculae of the spleen?

A

Thick, numerous, and tortuous dense irregular connective tissue that carries blood vessels, lymphatics, and nerves

41
Q

The capsule of the spleen possesses what kinds of cells?

A

Some smooth muscle cells and/or myofibroblasts

42
Q

What kind of lymphatic vessels are not seen in the spleen?

A

No afferent lymphatic vessels

43
Q

Are efferent lymph vessels seen with the spleen?

A

Yes

44
Q

What supports the cells of the spleen?

A

Reticular fibers produced by reticular cells

45
Q

White pulp makes up what amount of the spleen?

A

5-20%

46
Q

What area of splenic parenchyma is an area of concentrated WBCs (primarily lymphocytes)?

A

White pulp

47
Q

What is the general function of the white pulp of the spleen?

A

Immunity

48
Q

Where can white pulp be found in the spleen?

A

Next to capsule and septa

49
Q

What is the primary cell type in a splenic nodule?

A

B cell

50
Q

Splenic nodules are more common among what age group?

A

Children

51
Q

What is PALS?

A

Periarterial lymphatic sheath

52
Q

What kind of immunity is seen in a splenic nodule?

A

Humoral (due to presence of B cells and antibodies)

53
Q

Splenic nodules and PALS are areas of what kind of splenic parenchyma?

A

White pulp

54
Q

What is the structure responsible for long term storage for T cells in white pulp?

A

PALS

55
Q

What is the primary cell type of PALS?

A

T cells

56
Q

PALS surround what structures?

A

Central arteries

57
Q

What type of immunity is associated with PALS?

A

Cell-mediated immunity (due to presence of T cells)

58
Q

What type of parenchyma makes up the majority of the spleen?

A

Red pulp

59
Q

What are the functions of the red pulp?

A

Rapid blood filtration, allow contact with blood-bourne foreign antigens

60
Q

Capillaries connected to fenestrated venous sinuses (sinusoids) made of stave cells make up what part of red pulp splenic circulation?

A

Closed portion

61
Q

What are stave cells?

A

Unusually elongated endothelial cells

62
Q

Is all of the blood filtered in the closed red pulp circulation of the spleen?

A

No but most is

63
Q

In what type of circulation do capillaries end abruptly?

A

Open

64
Q

Does all blood filter through open splenic circulation?

A

Yes

65
Q

What cells can be seen with splenic cords?

A

Reticular fiber network, reticular cells, MANY macrophages, whole blood with many monocytes, APCs, plasma cells (sometimes many)

66
Q

What blood changes occur due to a splenectomy?

A

Increase in platelets and abnormal RBCs

67
Q

What is the effect of infection with a splenectomy?

A

Increased risk of bacteria septicemia

68
Q

What specific pathogen is a high risk of children who have undergone splenectomies?

A

Strep pneumo

69
Q

What change is seen in the liver after a splenectomy?

A

Takes up role of blood filtration (fully functioning in 24 hours), macrophage numbers increase

OrganHisto Exam One (7 decks)

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