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Path II > Thymus > Flashcards

Thymus Flashcards

1
Q

What is the function of the thymus?

A

Immunity

Differentiate T lymphocytes and dissemination

Secrete hormones, etc..

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2
Q

During embryogenesis, where does the thymus develop?

epithelial portion

lymphocytes

A

3rd and 4th branchial (pharyngeal) pouches

bone marrow

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3
Q

What is the structure?

A

Lymphoepithelial

stroma: epithelial cells, macrophages, dendritic cells

thymocytes

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4
Q

Where does the thymus lie in most animals?

what animals does it lie elsewhere

A

cranial mediastinum

Pig-jugular groove along the ventro-lateral neck and NOT in the thoracic cavity

Avian- above jugular groove on either side and occupy almost the entire length of the neck.

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5
Q

What are the precursor cells that enter the thymus?

A

Prothymocytes

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6
Q

What is your portal of entry into the thymus?

A

Hematogenous

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7
Q

What are your responses to injury?

A

Atrophy
Enlargement
Inflammation

Lymphoid hyperplasia

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8
Q

Why would you have a small thymus?

C/S

A

Primary or acquired immunodeficiency
Congenital and Degenerative disorders

infections
Combined immunodeficiency disorders (CIDs)

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9
Q

Why would you have a large thymus?

C/S

A

Hemorrage, hematomas

Neoplasia

Thymic Cysts

Dyspnea

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10
Q

If you have CID how would your thymus look and why?

A

Small

Inadequate T and B lymphocyte function.

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11
Q

What CS would you see with CID?

A

Nasal discharge

Unthrifty haircoat

Loss of of condition

Pneumonia

Diarrhea

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12
Q

Lesions of CID in a horse?

A

Severe bronchopneumonia

Small thymus, spleen, LN

Thymus may be difficult to ID

Reduction in the white pulp of the spleen due to absence of germinal centers and PALS

Lymphocyte depletion in LN

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13
Q

Who does XSCID affect and what kind of cell?

A

Male pups

lack mature, functional T lymphocytes

*males are Xtra…

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14
Q

Lesions of XSCID in dogs?

A

Small thymus, obscured by medistinal fat

other lymphoid organs usually unidentifiable at necropsy

Small dysplastic lobules w/a variable number of Hassalls corpuscles

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15
Q

Who gets JLIDS and what cell does it affect? CS?

A

Juvenile Llamas

B-cell

Wasting and sysceptible to chronic dz that fail to respond to therapy. Mild nonreg anemia

*alpacas are A’s and Llamas are Bs? so think B cell?

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16
Q

What are some reasons for acquire immunodeficient thymus atrophy?

A

Lack of antigenic stimulation

toxins
chemo
radiation
infection
malnutrition
age
17
Q

What are some viruses that can cause thymus atrophy?

A

Parvo
distemper
adeno

BVDV,
EHV
FIV

18
Q

What will you see in the thymus after atrophy?

A

lymphocytolysis

loss of architecture

decreased lymphocyte populations

19
Q

What kind of toxins can cause atrophy?

A

metals

fungus

20
Q

Why does chemo and radiation cause atrophy

A

Inhibition of cell division and activation of lymphocytes=

immunosuppression

21
Q

What are some causes for thymic hemorrhage/hematomas?

A

Trauma:
Fall
HBC
pulling on the leash too hard

Rupture of dissecting aortic aneurysm

Rodenticides

22
Q

Thymic lymphosarcoma is common in?

A

cats with FeLV

Calves with BLV

dogs

23
Q

What are you gonna find in an aspirate of a thymic lymphosarcoma?

A

Medium to large lymphocytes with vacuolated cytoplasm

24
Q

Will you see chylous with lymphosarcoma or thymoma?

A

sarcoma bc of lipid accumulation

25
Q

Thymomas are a tumor of what cell type?

A

Epithelial cells

26
Q

What life stage will you see a thymoma in a dog?

A

older

27
Q

What can thymomas cause?

A

Myasthenia gravis

megaesophagus

28
Q

What is the pathogenesis behind MG caused by a thymoma?

A

Thymic myoid cells express epitopes that are cross-reactive w/skeletal m proteins–ACh receptors.

29
Q

Histo for thymoma

A

Round to spindle shaped epithelial cells

small lymphocytes with few medium and large lymphocytes

30
Q

Thymic cysts

A

Lined by ciliated epithelium

usually no significance

31
Q

Thymitis

A

Rare

infections from PMWS, salmon poisoning

Path II (12 decks)

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