Lymphatics Flashcards

1
Q

What is the main function of the lymphatic system?

A

To prevent swelling due to edema.

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2
Q

How much plasma does the lymphatic system collect per day?

A

Collects about 3 liters a day; Returns it to the general circulation near the base of the neck.

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3
Q

Aside from phagocytosis, what is a leukocytes special function?

A

Diapedesis; Requires selectins and adhesins

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4
Q

What are the primary lymphoid tissues?

A

Fetal liver, Red marrow, and Thymus; Sites of hematopoiesis

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5
Q

Why is the fetal liver large in comparison to the body?

A

Due to the demands of hemopoisis and to make formed elements of the fetal blood.

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6
Q

What are the secondary lymphoid organs?

A

Spleen, lymph nodes, MALT, SALT; MALT contains tonsils, peyer’s patches, appendix and BALT.

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7
Q

When is a lymphocyte naive?

A

Lymphocytes are considered naive until they’re activated by antigens.

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8
Q

Where can red bone marrow be found in fetuses and infants?Adults?

A

All fetal and infant bone marrow is red. Adults have red bone marrow in the hips, sternum, scapula, skull, vertebra and the heads of femur and humerus

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9
Q

Where does most of B lymphocyte producion occur?

A

In red bone marrow; Once produced, they migrate away from endosteum and towards an artery and mature in periphery.

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10
Q

Where is the thymus?

A

Superior mediastinum; Anterior to great vessels; Recieves blood from internal thoracic, and superior thyroid arteries

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11
Q

Describe thymic involution

A

Adipocytes slowly infiltrate the thymic cortex and medulla replacing functional cells.

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12
Q

Histologically describe the outer capsule of the thymus

A

Eosinophilic, thin, dense CT; Partially penetrates the thymus as septa

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13
Q

Histologically describe the outer cortex of the thymus.

A

Highly Basophilic, outer cellular region due to high cell density; Contains T cells in earliest stage of development.

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14
Q

Histologically describe the medulla of the thymus.

A

Less basophilic, No septa; Contains T cells in later stages of development; No follicles in the thymus.

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15
Q

Where can Epithelioreticular cells be found in the thymus?

A

Both the cortex and medulla.

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16
Q

What is the function of the Blood-Thymus barrier

A

Protects developing thymocytes from encountering circulating antigen too early during education.

17
Q

Describe the Blood-Thymus barrier.

A
  1. Pro T-cells must pass through endothelium of capillary and basal lamina.
  2. Must not be eaten by resident macrophages in perivascular connective tissue.
  3. Pass through ERCs and their basal lamina.
18
Q

What other cells are in the Thymic cortex?

A

Dendritic cells and macrophages; They phagocytose the debris of more than 95% of thymocytes that undergo apoptosis.

19
Q

What happens to thymocytes that pass their education?

A

They migrate from the cortex to the medulla and re-enter blood circulation in postcapillary venules as naive T cells.

20
Q

What are Thymic corpuscles?

A

Closely packed ERCs that are dying and lost their nuclei.