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VETM 425 Sys Path > Lecture 15: Blood and Lymph > Flashcards

Lecture 15: Blood and Lymph Flashcards

1
Q

Describe the species variation seen in the thymic gland

A

All species have a thoracic lobe

ruminants and pigs have a large cervical lobe

cats and horses have a small cervical lobe

dogs don’t have a cervical lobe

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2
Q

Describe the structure of the thymus

A

There is a cortex and medulla

Lymphoid tissue contains educated T lymphocytes from the bone marrow and they can circulate to secondary lymphoid organs

Epithelial tissue is present to support the T cells - hassells corpuscles

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3
Q

What are the 2 consequences of thymic dysfunction?

A

immunodeficiency
autoimmunity

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4
Q

How is an abnormal thymus classified grossly?

A

too small
too big

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5
Q

Why might a thymus be too small?

A

aplasia due (severe combine immunodeficiency disorder)

hypoplasia (normal involution or lymphoid atrophy)

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6
Q

What is SCID and what species does it affect?

A

It is severe combine immunodeficiency disorder. It is a genetic reduction in cell mediated and humoral immunity

It can occur in humans, mice, dogs, and horses

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7
Q

What causes equine SCID and what are the consequences?

A

An autosomal recessive disorder related to Arabian horses

It results in recurrent infection and death
- virus: adenovirus
- fungi - pneumocystis carinii

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8
Q

What are the gross lesions associated with equine SCID?

A

bronchopneumonia
very small thymus, lymph nodes, and spleen

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9
Q

What is lymphoid atrophy and why does it occur?

A

Small thymus. You must differentiate from normal involution

It could be caused by infection/toxins/chemotherapy/radiation/malnutrition/stress
- virus: feline or canine parvo/equine herpes 1/BVDV/canine distemper

It results in an acquired immunodeficiency

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10
Q

Compare 2 neoplastic processes that can occur in the thymus

A

thymoma (from thymic epithelium)
- dogs mainly (also cats/horse/pig/goat)
- older animals
- benign
- uncommon
- can be associated with immune-mediated disease like myasthenia gravis

lymphoma (from T cells)
- cats (FeLV) and cattle (bovine thymic lymphoma)
- young
- aggressive

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11
Q

At necropsy you find an enlarged thymus, what are 2 differentials?

A

thymoma or lymphoma

Cannot differentiate grossly

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12
Q

Describe the structure of lymph nodes

A

They are soft, pale, tan, and oval

The outer cortex is full of B cells and the inner cortex is full of T cells

The medulla contains medullary cords (macrophage/monocyte system) in the medullary sinuses

Lymph and blood circulates

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13
Q

How are lymph node abnormalities classified?

A

too big
too small
generalized
localized

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14
Q

How is reactive lymphoid hyperplasia differentiated from lymphoma?

A

The architecture of hyperplasia is still intact whereas lymphoma destroys the tissue architecture

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15
Q

What are 2 categories of small lymph nodes?

A

aplastic

hypoplastic

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16
Q

What can cause lymph node aplasia?

A

SCID related lymph node hypoplasia

17
Q

What might cause hypoplastic lymph nodes

A

aging
reduced antigen stimulation
viruses (BVDV/CDV)
cachexia
malnutrition

18
Q

4 main causes of lymphadenopathy and what are their primary features?

A

reactive lymphoid hyperplasia which can be due to infection stimulation either localized or generalized

acute or chronic lymphadenitis which is infection and inflammation causing caseous lymph nodes with reduced architecture

primary neoplasia like lymphoma which is usually systemic

metastatic neoplasia which is usually localized due to draining lymph from carcinomas

19
Q

On necropsy you have a horse with lymphadenopathy. The lymph nodes contain caseous material and have lost their architecture. What process has occurred and what is one differential you have?

A

acute lymphadenitis due to streptococcus equi equi infection (strangles)

20
Q

Describe the structure of the spleen

A

There is a thick muscular capsule

White pulp will stain blue/purple on H and E stain and it contains B cell follicles and T cell (PALS)
- cell mediated and humoral immunity

Red pulp will stain red on H and E stain and it contains the macrophage/monocyte system and red pulp vascular space
- phagocytosis of pathogens or senescent (pathologic) or altered (physiologic) RBC
- RBC storage
- intramedullary hematopoiesis

21
Q

Describe species variations in the spleen that are clinically relevant

A

The gastrosplenic ligament
dogs and pigs = large
ruminants = small

Storage vs defence capacity
- most will have defense capacity
- dog and horses (also cats) have larger storage capacity

22
Q

How are abnormal spleen classified?

A

too big
too small
bloody
not bloody
uniform
nodular

23
Q

What are 2 possible causes of a spleen that is too small and why might they occur?

A

contraction (blood) due to excitement or shock

lymphocyte causes:
- SCID related lymphoid hyperplasia
- cachexia
- aging

24
Q

What is the gross appearance of a spleen that is too small?

A

small with a wrinkled capsule

25
Q

What are the 4 categories of splenomegaly? What do they look like grossly

A

uniform with blood: dark red/blue/black and will ooze when cut

uniform without blood: meaty/firm/no oozing

nodules with blood

nodules without blood: firm

26
Q

What are 3 main causes of a big bloody spleen?

A

congestion due to torsion or barbituates

acute hemolytic anemia

acute hyperemia due to acute septicemia

27
Q

What are 4 main causes of a big meaty spleen

A

chronic infection

chronic hemolytic anemia due to macrophage hyperplasia and extramedullary hematopoiesis

lymphoid hyperplasia

diffuse neoplasia

28
Q

What type of neoplastic conditions causes diffuse neoplastic splenic infiltrates?

A

round cell tumors
- lymphoma
- mast cell
- histiocytic
- round cell

29
Q

What are 4 causes of a big spleen with bloody nodules?

A

hematomas due to trauma, or secondary to a splenic mass

incomplete contraction or some areas which is uncommon but primarily occurs in dogs

acute splenic infarcts which is a hallmark sign of classical swine fever

hemangiosarcoma

30
Q

A pig necropsy reveals an enlarged spleen with bloody nodules, which reportable disease should you be thinking about?

A

classical swine fever

31
Q

What are 4 main causes of a big spleen with nodules (no blood)

A

nodular hyperplasia

primary neoplasia

secondary neoplasia

inflammation (abcess/granuloma)

32
Q

List the types of benign tumors of the spleen

A

there are none

33
Q

What is a common incidental finding in the spleen of old dogs

A

siderofibrotic plaques aka gamna gandi bodies

VETM 425 Sys Path (15 decks)

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