CO1 Hemolymphatic Flashcards
(35 cards)
Hemolymphatic System: What is it?
- Hematopoietic cells
- Where they are derived & where they develop
- Routes they travel & sites they work
- Myeloid tissues = bone marrow & the circulating cells derived there (RBCs, neutrophils, eosinophils, basophils, mast cells, platelets)
- Lymphoid tissues = lymph nodes, spleen, thymus, circulating lymphocytes, Bursa of Fabricius
hematopoietic cell lines
pluripotent stem cell becomes:
1. myeloid stem cell
> macrophage
> neutrophil
> eosinophil
> basophil
> mast cell
> platelets
> erythrocyte
2. lymphoid stem cell
- T lymphocyte
- B lymphocyte
> plasma cell
primary lymphoid organs
- Bone Marrow
- Thymus
secondary lymphoid organs
- Lymph nodes
- Tonsils
- Spleen
- Mucosa-associated lymphoid tissue (MALT)
bone marrow function
= Major hematopoietic organ in adults
= Major site for B-cell development throughout life
Where does hematopoiesis occur?
Yolk-sac
– Embryo: shifts to liver & spleen in fetus
Liver & Spleen
– Fetus: shifts to bone marrow prior to birth
– Mature: Extramedullary hematopoiesis (EMH)
Bone Marrow
– Young: all marrow spaces
– Mature: marrow spaces of the axial bones, proximal humerus and femur
reasons for bone marrow hyperplasia
Increased demand
– Loss of RBCs/platelets
> Hemorrhage, Hemolytic anemia etc.
– Inflammatory stimulus
> Liver abscess, Pneumonia etc.
when do we see myelopthisis
(bone marrow replacement)
– Myelofibrosis, Chronic Leukemia etc.
when do we see serous atrophy of fat in bone marrow
– Cachexia, Starvation
* Fat is metabolized, bone marrow reticular cells produce a mucoid substance
gross pathology of bone neoplasia vs osteomyelitis? what about bone marrow activiation?
osteomyelitis - craters with pus
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neoplasia / osteosarcoma - lack of support / weakness, new bone added to outside
> activated endosteal bone marrow to clean necrosis
what is the structure and function of the thymus?
- Differentiation, selection, & maturation of T-cells
– T-cell receptor (TCR) rearrangement
– Positive selection (MHC binding)
– Negative selection (self-reactive)
<><> - 3 Zones:
1. Subcapsular: T-cells from bone marrow enter thymus
2. Cortex: positive/negative selection + TCR rearrangement
3. Medulla: negative selection
- What % of T-cells exit the Thymus?
2%
Two main cell types of the thymus:
- Lymphocytes
- Epithelial cells (Hassall’s corpuscles)
thymus location and appearance
- intrathoracic mediastinum, cranial to the heart and ventral to the trachea
- pink, lobulated
What is the term used to describe the normal physiologic change in the thymus with age?
thymic involution (replacement of thymus with adipocytes)
- begins after puberty / sexual maturity
reasons for a smaller thymus
- Involution (physiological NOT pathological)
- Inadequate Nutrition
- Stress (glucocorticoids)
- Infectious Agents (viruses)
- Intoxicants (lead, mercury)
- Medical Tx (radiation, chemotherapy)
- Aplasia (SCID)
reasons for a large thymus (diffuse and focal)
Diffuse:
- variation (physiological NOT pathological)
- Hyperplasia (repeated immunization)
Focal/Localized:
- Cysts (persist during involution or acquired)
- Neoplasia (thymoma*) > associated with paraneoplastic syndromes
Thymic Hemorrhage
* Important features of signalment/history? (3)
- age
- access, eg. to anticoagulants
- automobile??
Ddx for thymic hemorrhage
I. Idiopathic hemorrhage
II. Anticoagulant toxicity (rodenticide)
III. Traumatic hemorrhage
ante and post mortem diagnostic tests for thymic hemorrhage
- Antemortem (CBC, clotting times)
- Postmortem (stomach content…freeze it)
Signalment: canine, 11 mos, CM
Spontaneous Idiopathic Thymic Hemorrhage
– Proposed pathogenesis:
– This is a diagnosis of:
- Thymic involution → thin walled vessels no longer have structural support from adjacent parenchyma → (minor trauma?, sudden increase in BP?) → hemorrhage
– This is a diagnosis of: exclusion
prepubescent dog with thymic hemorrhage - histologic findings?
– absence of evidence of thymic involution (pre-onset of sexual maturation)
– extensive hemorrhage
pathogenesis of rodenticide toxicity causing thymic hemorrhage
- Ingestion of anticoagulant rodenticide → vitamin K deficiency → clotting factors consumed without replacement → hemorrhage
Spontaneous Idiopathic Thymic Hemorrhage
- Rule outs? how? requires what?
R/O: Trauma, anticoagulant rodenticide
– History
– Physical examination
– Clotting times
– Examination of ingesta
– Toxicological screening for anticoagulant rodenticides
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* Required: Currently undergoing thymic involution
– Signalment: begins at 6-12 mos depending on the breed
