15a – Intro to Hematopoietic Flashcards
What are the 2 tissues of the hematopoietic system?
- Myeloid tissue
- Lymphoid tissue
Myeloid tissue consists of
- Bone marrow
- Blood cells
- Mononuclear-phagocyte system
Lymphoid tissue consists of
- Lymph nodes
- Spleen
- Thymus
- Accessory lymphoid tissue
How can you clinically evaluate the hematopoietic system? (easily accessible ones)
- CBC
- Blood smears
- Peripheral lymph node aspirate
How can you clinically evaluate the hematopoietic system? (more invasive techniques)
- Bone marrow aspirates
- Biopsies: lymph nodes, spleen, bone marrow
- Necropsy: useful for lymphoid organs, less for marrow
Where are blood cells made in the embryo?
- Yolk sac
Where are blood cells made in the fetus?
- Liver
- Spleen
- Thymus
- Lymph node
- Bone marrow
Where are blood cells made in neonates?
- Mostly bone marrow
o Long and flat bones
Where are blood cells made in the adults?
- Bone marrow in all regions of flat bones and extremities of long bones
Extramedullary hematopoiesis (EMH)
- When it is NEEDED!
Even though bone marrow is in multiple sites, it will respond as a
- *SINGLE TISSUE
Samples of bone marrow can be taken from any bone with red marrow
- Proximal femur, iliac crest, proximal humerus of dogs and cats
- Sternum of horses
- Proximal rib of cattle
- *aspirates and core biopsies
What are some abnormalities IDed on hematology that indicate bone marrow issues?
- Unexplained cytopenia’s
- Maturation or morphological defects (atypical cells in circulation)
- Suspected myeloproliferative diseases
- Potential malignancies metastatic to marrow
Bone marrow aspirate/smears: microscopic evaluation
- Interpreted by clinical pathologists
- Important for
o Cell morphology
o Erythroid to myeloid ratio
o Primary or metastatic neoplasia
Bone marrow core biopsy: microscopic evaluation
- Interpreted by anatomic pathologists
- Import for
o Ratio of fat to hematopoietic cells
o Myelofibrosis
o Primary or metastatic neoplasia
The END result of pathology of bone marrow and blood cells depends on TYPE of cell damage
- Multipotent stem cells: multiple cell lines affected
- Committed stem cells: one or more lines affected
- Differentiated cells: one cell type affected
Cytopenias and anemia mean
- Decreases in cell lines
Cytoses and philias mean
- Increases in cell lines
What are changes reflected by in the bone marrow?
- Increased OR decreased cellularity
- *changes in proportion of hematopoietic tissue (red marrow) to adipose tissue (yellow marrow)
What are the different ‘diseases’/disorders that can occur to bone marrow?
- Hereditary disorders
- Degeneration/necrosis
- Inflammation
- Adaptations of growth
- Neoplasia
Hematopoietic tissue is HIGHLY ACTIVE=it is susceptible to insults, what are some examples?
- Radiation
- Toxins/drugs
- Viral agents
- Immune mediated
- Idiopathic
Osteomyelitis
- Inflammation of bone (osteitis) AND medullary cavity (myelitis)
Bone marrow hypoplasia/aplasia
- Decrease proliferative activity
- One or multiple cell lines can be affected
What are 3 causes of bone marrow hypoplasia/aplasia?
- Bone marrow suppression
- Lack of nutrients
- Endocrine dysfunction
What are reasons for bone marrow suppression? (hypoplasia/aplasia)
- Estrogen (exogenous and endogenous)
- Chronic disease
- Chronic renal disease
What are some nutrients, that if lacking can lead to bone marrow hypoplasia/aplasia?
- Iron
- Vitamin B12
- Folate
What type of endocrine dysfunction can lead to bone marrow hypoplasia/aplasia?
- Hypothyroidism
What does bone marrow hypoplasia look like GROSSLY?
- Increased white or yellow marrow
What does bone marrow hypoplasia look like histologically?
- Increased ratio of fat to hematopoietic cells
- Normal: 50/50
What is bone marrow hyperplasia?
- Proliferative response
o May affect one or multiple cell lines - *response to increased peripheral damage or hypofunction of blood cells
Erythroid hyperplasia is a response to
- Anemia
Megakaryocytic hyperplasia is a response to
- Decreased platelets
What are the types of myeloid hyperplasia? (3)
- Neutrophilia
- Eosinophilia
- Monocytosis
Neutrophilia may indicate
- Bacterial infections
- Tissue necrosis
Eosinophilia may indicate
- Parasites
- Hypersensitivities
Monocytosis may indicate
- Chronic infections
- Specific agents
What are the gross lessions of bone marrow hyperplasia?
- Red marrow replaces the yellow marrow
o Metaphyses
o Endosteal surfaces of diaphysis
o Progresses to occupy entire marrow cavity
What are the histological lesions of bone marrow hyperplasia?
- Increased cellularity (decreased ratio of fat to hematopoietic cells)
- One or more cells lines can be affected
- Shift toward immaturity (ex. left shift in neutrophils)
- Extramurally hematopoiesis (spleen and liver) IF SEVERE
Serous atrophy of fat (bone marrow atrophy)
- Gelatinous transformation of fat within marrow
- *due to cachexia
o Secondary to chronic diseases, inflammatory reactions, cancer - *amber colour
o Sometimes osteopenia=reduced thickness of cortical bone
