Haematopoietic system

Question 1

What is myeloid tissue?

Answer 1

• Bone marrow
• Blood cells
• Mononuclear-phagocyte system

Question 2

What is lymphoid tissue?

Answer 2

• Lymph nodes
• Spleen
• Thymus
• Accessory lymphoid tissue

Question 3

What infectious agents can cause anaemia?

Answer 3

• Equine infectious anaemia
• Anaplasmosis
• Haemotropic mycoplasma
• Babesiosis
• Trypanosomiasis
• Theileriosis

Question 4

What is the function of lymph nodes and what do they contain?

Answer 4

Function:
* Filtration of lymph
* Immune response
Structure:
* Outer cortex -> follicles (mostly B cells)
* Inner cortex -> paracortex (mostly T cells)
* Medulla -> mostly B cells and macrophages

Question 5

What is lymphadenopathy?

Answer 5

• Enlargement of lymph node(s) of unknown cause
• Can be localised or generalised

Question 6

What can cause enlarged lymph nodes?

Answer 6

• Lymphadenitis
• Lymphoid hyperplasia
• Hyperplasia of the monocyte/macrophage system
• Primary neoplasia
• Secondary Neoplasia

Question 7

What can cause lymph nodes to decrease in size?

Answer 7

• Lymphoid atrophy
• Lymph node degeneration/necrosis
• Lymph node hypoplasia

Question 8

What causes acute lymphadenitis? (inflammation)

Answer 8

• Usually the result of a regional lymph node draining a site of inflammation and becoming infected.

Question 9

What is an example of chronic suppurative lymphadenitis?

Answer 9

Strangles -strep equi var equi
if spreads to viscera = bastard strangles
can drain to guttural pouch = guttural pouch emphysema

Question 10

What causes caseous lymphadenitis?

Answer 10

Corynebacterium pseudotuberculosis - enters via shearing wound
-enlargement of LN - onion ring look - becomes systemic with time

Question 11

what can cause nodular granulomatous lymphadenitis?

Answer 11

• Mycobacterium bovis (bovine tb)
• Mycobacterium avium subsp.
  Paratuberculosis (Johne’s disease)
• Actinobacillus lignieresii (wooden tongue)
• Migrating parasitic larva

Question 12

What can cause Diffuse granulomatous lymphadenitis?

Answer 12

• Porcine Circovirus type 2
• Histoplasma capsulatum
• Blastomyces dermatitidis
• Cryptococcus neoformans

Question 13

What can lymph nodes metastasis occur from?

Answer 13

• Common with carcinomas, melanomas, mast cell tumours

Question 14

What is a lymphoid leukaemia and lymphoma?

Answer 14

• Lymphoid leukaemia = neoplastic lymphocytes in bone marrow/ blood
• Lymphoma (lymphosarcoma) = Neoplastic lymphocytes in tissues/ organs

Question 15

What lymphoma is notifiable?

Answer 15

Enzootic bovine lymphoma

Question 16

What are the 3 types of sporadic bovine lymphoma?

Answer 16

1.Calf form - <6m/o, symmetrical lymphadenopathy
2.Juvenile form - yearlings - mediastinal mass
3.Cutaneous form - 2-3y/o - skin only

Question 17

What is the function of the thymus?

Answer 17

• Proliferation and maturation of T cells

Question 18

When does thymic hypoplasia occur?

Answer 18

• Occurs as part of severe combined
  immunodeficiencies (SCID) in foals and
  some breeds of dogs

Question 19

When does thymic atrophy occur?

Answer 19

• Shrinkage of thymic organ by: inadequate nutrition,
  intoxications, infectious agents (eg canine distemper
  virus), lack of antigenic stimuli, drugs etc.

Question 20

What is a thymoma?

Answer 20

• Neoplastic proliferation of epithelial cells
• Less common- dogs, sheep, goats
• Slow growing, encapsulated

Question 21

What is a thymic lymphoma?

Answer 21

• Neoplastic proliferation of T- cells (lymphocytes)
• Often younger animals (cats, calves, and dogs)
• Malignant behaviour

Question 22

What is the structure and function of the red pulp of the spleen?

Answer 22

Structure
* Sinusoids/vascular spaces
* Splenic cords
Function
* Filters blood- removal of foreign material (phagocytosis)
* RBC storage
* Haematopoiesis (EMH)

Question 23

What is the structure and function of the white pulp of the spleen?

Answer 23

Structure
* Periarterial lymphatic sheaths (PALS) (T-cells)
* Lymphoid nodules (B-cells)
* Marginal zone (Macrophages)
Function
* Immune response

Question 24

What are the miscellaneous diseases of the spleen?

Answer 24

*Splenic amyloidosis - friable and waxy -orange discolouration
*Splenic torsion - twist around gastrosplenic ligament
*Siderotic plaques - firm encrustations on the surface
*Splenic haematoma - from splenic rupture, haemoabdomen,
hypovoloaemic shock
*Accessory spleens

Question 25

What are the 2 different types of acute splenitis and their causes+ gross morphology?

Answer 25

multifocal necrosuppurative splenitis - multifocal milliary white foci within the spleen
* Francisella tularensis (Tularemia)
* Yersinia pseudotuberculosis (Yersiniosis)
Septicaemic splenitis - Splenomegaly, Dark discolouration, Engorged with blood
* African swine fever
* Erysipelas
* Anthrax **

Question 26

What are the 2 different types of chronic splenitis and causes?

Answer 26

Nodular granulomatous splenitis
* Mycobacterium avium infection (Mycobacteriosis) in a chicken
Diffuse granulomatous splenitis
* Histoplasma capsulatum (Histoplasmosis) in a dog

Question 27

What are the 2 disturbances of growth within the spleen?

Answer 27

Benign nodular hyperplasia
* Common finding in old dogs
* Usually incidental
* May predispose to splenic haematomas
Lymphoid hyperplasia
* Hyperplasia of the white pulp
* Response to blood-borne antigen/chronic antigenic stimulation