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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
What cells make up the cortex of the thymus?
T lymphocytes, macrophages, TEC types I, II, and III
25
What part of the thymus contains a lower cell density?
Medulla
26
Where are T lymphoblasts produced?
Bone marrow
27
What cell types are found in the medulla of the thymus?
Fewer but large T cells, macrophages, dendritic cells (APC), and TEC types IV, V, and VI
28
When the T lymphocytes first enter the thymus, are they immunocompetent?
No; they are immunoINcompetent
29
Where do the T lymphocytes leave the bloodstream?
At the corticomedullary line
30
Where do T cells migrate to divide and are tested through the positive selection process?
Periphery of the cortex
31
What happens to the 98% of T cells that fail the selection process in the cortex of the thymus?
Apoptotic death
32
Where do the surviving T cells from the cortex of the thymus migrate to?
Back to the medulla
33
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?
Cytotoxic (killer) or helper T cells
34
What three things do we lack in the thymus?
Afferent lymph vessels, reticular fibers, reticular cells
35
Why do we lack afferent lymph vessels in the thymus?
Unwanted debris and foreign antigens that come with afferent vessels
36
What are the functions of the spleen?
Immunity, blood filtration using macrophages, long term T cell storage, stores some WBCs and platelets, hemopoietic organ in fetus
37
Large numbers of what kind of WBC are specifically found in the spleen?
Monocytes
38
What is the capsule of the spleen made of?
Thick dense irregular fibroelastic connective tissue
39
What is the convex surface and concave area of the spleen called?
Hilum
40
What are the trabeculae of the spleen?
Thick, numerous, and tortuous dense irregular connective tissue that carries blood vessels, lymphatics, and nerves
41
The capsule of the spleen possesses what kinds of cells?
Some smooth muscle cells and/or myofibroblasts
42
What kind of lymphatic vessels are not seen in the spleen?
No afferent lymphatic vessels
43
Are efferent lymph vessels seen with the spleen?
Yes
44
What supports the cells of the spleen?
Reticular fibers produced by reticular cells
45
White pulp makes up what amount of the spleen?
5-20%
46
What area of splenic parenchyma is an area of concentrated WBCs (primarily lymphocytes)?
White pulp
47
What is the general function of the white pulp of the spleen?
Immunity
48
Where can white pulp be found in the spleen?
Next to capsule and septa
49
What is the primary cell type in a splenic nodule?
B cell
50
Splenic nodules are more common among what age group?
Children
51
What is PALS?
Periarterial lymphatic sheath
52
What kind of immunity is seen in a splenic nodule?
Humoral (due to presence of B cells and antibodies)
53
Splenic nodules and PALS are areas of what kind of splenic parenchyma?
White pulp
54
What is the structure responsible for long term storage for T cells in white pulp?
PALS
55
What is the primary cell type of PALS?
T cells
56
PALS surround what structures?
Central arteries
57
What type of immunity is associated with PALS?
Cell-mediated immunity (due to presence of T cells)
58
What type of parenchyma makes up the majority of the spleen?
Red pulp
59
What are the functions of the red pulp?
Rapid blood filtration, allow contact with blood-bourne foreign antigens
60
Capillaries connected to fenestrated venous sinuses (sinusoids) made of stave cells make up what part of red pulp splenic circulation?
Closed portion
61
What are stave cells?
Unusually elongated endothelial cells
62
Is all of the blood filtered in the closed red pulp circulation of the spleen?
No but most is
63
In what type of circulation do capillaries end abruptly?
Open
64
Does all blood filter through open splenic circulation?
Yes
65
What cells can be seen with splenic cords?
Reticular fiber network, reticular cells, MANY macrophages, whole blood with many monocytes, APCs, plasma cells (sometimes many)
66
What blood changes occur due to a splenectomy?
Increase in platelets and abnormal RBCs
67
What is the effect of infection with a splenectomy?
Increased risk of bacteria septicemia
68
What specific pathogen is a high risk of children who have undergone splenectomies?
Strep pneumo
69
What change is seen in the liver after a splenectomy?
Takes up role of blood filtration (fully functioning in 24 hours), macrophage numbers increase

OrganHisto Exam One (7 decks)

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