72 Questions
What is the primary function of reticular cells in the marrow spaces?
To provide structural support by producing reticulin and cytoplasmic processes
What is the role of adipocytes in the marrow environment?
To store or provide energy and regulate the marrow environment
What type of collagen is produced by reticular cells?
Reticulin
What is the term for adipose-derived hormones secreted by adipocytes?
Adipokines
What is the composition of the hematopoietic cells and adipose tissue in the marrow?
Changes with age
What is the function of the osteogenic layer of endosteal cells in the periosteum?
To support bone growth and development
What is the term for the network of stromal cells and extracellular matrix that provides support to hematopoietic cells?
Stromal scaffolding
What type of stains are used to visualize reticulin and cytoplasmic processes in the marrow?
Silver reticulin stains
What is the primary function of macrophages in the bone marrow?
To store iron and aid in erythrocyte maturation
What is the name of the vessels that arise from the periosteal arteries and penetrate the cortical bone?
Periosteal vessels
What percentage of the total marrow space do adipocytes constitute?
25% to 75%
What is the name of the process by which hematopoietic cells enter vascular sinusoids?
Diapedesis
What is the role of stromal cells in the bone marrow?
To provide structural and metabolic support to hematopoietic cells
What is the name of the cells that line vascular sinusoids and release cytoplasmic fragments (platelets) into sinusoidal lumens?
Megakaryocytes
What is the function of osteoblasts in the bone marrow?
To structurally support the marrow
What do chemokines influence in the bone marrow?
Cell trafficking and metabolism
What is the function of sinusoidal endothelial cells?
To regulate traffic of chemicals and particles between the intravascular and extravascular spaces
Where does hematopoiesis occur in the bone marrow?
In the interstitium between the venous sinusoids
What is the role of the extracellular matrix in the hematopoietic microenvironment?
To regulate the behavior of hematopoietic cells
What is the characteristic of hematopoietic tissue?
It is highly proliferative and produces billions of cells per kilogram of body weight per day
What is the role of pluripotent hematopoietic stem cells (HSCs)?
To give rise to cells with committed differentiation programs
What is the process of hematopoietic differentiation shown in?
Fig. 13.2
What is the term used to describe cells in the bone marrow that have stopped dividing?
Postmitotic compartment
What is the functional interplay among hematopoietic cells influenced by?
All of the above
What is the primary regulator of thrombopoiesis?
Thrombopoietin (Tpo)
What is the function of β1-tubulin microtubules within megakaryocytes?
Platelet shedding
What happens to thrombopoietin when platelet mass is increased?
It decreases
What is the term for the production of platelets?
Thrombopoiesis
What is the result of platelet activation?
Shape change and granule release
What is the function of platelets in primary hemostasis?
Central role in primary hemostasis
What is the characteristic of megakaryocytes?
Large cells with multiple nuclei
What is released by activated platelets, which supports coagulation?
Calcium and von Willebrand factor
What is the function of platelet glycoprotein surface receptors?
To facilitate platelet aggregation and adherence to subendothelial collagen
Which of the following coagulation complexes involves factors X, V, and II?
Prothrombinase complex
What is the primary reason for the decreased concentration of blood lymphocytes with age?
Increased destruction of lymphocytes
What is the term for the process of platelet formation?
Thrombopoiesis
What is the purpose of the open canalicular system in platelets?
To expand the surface area of platelets
What is the method of examination of the bone marrow that involves the visualization of reticulin and cytoplasmic processes?
Microscopic examination
Which of the following is NOT a mechanism of disease in bone marrow?
Homeostasis
What is the term for the study of the formation and development of blood cells?
Hematopoiesis
What is the result of marrow-directed injury or disturbances in hematopoietic cells?
Production of abnormal hematopoietic cells (dysplasia)
Why is bone marrow not routinely sampled during postmortem examinations?
It is not necessary for diagnosis
What is the term for a decrease in hematopoietic cells in the bone marrow?
Hypoplasia
What is the ideal approach for evaluating bone marrow?
Multimodal evaluation
What is the indication for bone marrow evaluation in cases of suspected leukemia?
All of the above
What is the difference between hypoplasia in the bone marrow and non-marrow sites?
Hypoplasia is used to describe a decrease in production after normal development in the bone marrow, but a failure of initial development in non-marrow sites
What is the term for a failure of hematopoietic cell development in the bone marrow?
Aplasia
What is the result of extramarrow tissue-directed injury or disturbances in hematopoietic cells?
Production of fewer hematopoietic cells
What is the characteristic of neutrophils in animals with leukocyte adhesion deficiency?
Migrate into the tissues
What is the term for the anomaly in which the nuclei of neutrophils, eosinophils, and basophils fail to segment?
Pelger-Huët Anomaly
What is the average blood half-life of neutrophils in health?
5 to 10 hours
What is the result of oxidative injury in domestic species?
Hemolytic anemia and/or MetHgb
What is the typical appearance of bone marrow in cases of pancytopenia?
Hypocellular with markedly reduced hematopoietic cells
What is the name of the condition that mimics Pelger-Huët Anomaly, but is acquired and reversible?
Pseudo–Pelger-Huët anomaly
What is the characteristic of neutrophils in healthy animals with Pelger-Huët Anomaly?
Hyposegmented nuclei with mature, condensed chromatin
What is the name of the disorder characterized by the accumulation of porphyrins in the body?
Erythropoietic Porphyria
What is the term for the study of the formation and development of blood cells?
Hematopoiesis
What is a characteristic of granulocytes in Pelger-Huët Anomaly?
Hyposegmented
What type of cells replace hematopoietic cells in the bone marrow of individuals with pancytopenia?
Adipose tissue
What is the result of G6PD deficiency in erythrocytes?
Oxidative injury and hemolytic anemia
What is the primary manifestation of G6PD deficiency in erythrocytes?
Oxidative hemolytic anemia
What is the consequence of marrow-directed injury or disturbances in hematopoietic cells?
Aplastic Anemia
Leukocyte Adhesion Deficiency (LAD) is characterized by a deficiency in which integrin?
β2 (CD18)
What is the name of the section that focuses on the more common, well-characterized, or recently reported congenital disorders of blood cells?
Congenital Disorders
What is the term for the production of platelets?
Thrombopoiesis
What is the duration of platelet circulation in the blood?
5-10 days
What is a characteristic of blood neutrophils in Leukocyte Adhesion Deficiency?
Segmented with more than five nuclear segments
What is the consequence of the development of signs of anemia?
Variable appearance of anemia
What is the mode of inheritance of Pelger-Huët Anomaly in Australian Shepherd dogs?
Autosomal dominant with incomplete penetrance
What is the result of impaired leukocyte adhesion in Leukocyte Adhesion Deficiency?
Impaired migration from blood into tissues
What is a common consequence of Leukocyte Adhesion Deficiency?
Recurrent infections
What is the outcome of G6PD deficiency in erythrocytes?
Oxidative hemolytic anemia
Study Notes
Structure and Function of Bone Marrow
- Bone marrow is supported by an anastomosing network of trabecular bone that radiates centrally from the compact bone of the cortex
- Trabecular bone is covered by periosteum, consisting of an inner osteogenic layer of endosteal cells, osteoblasts, and osteoclasts, and an outer fibrous layer
- Reticular cells (fibroblasts) provide structural support to hematopoietic cells by producing a fine network of reticulin and extending long cytoplasmic processes around other cells and structures
- Adipocytes store or provide energy, secrete adipose-derived hormones (adipokines), and help regulate the marrow environment by paracrine signaling and cytokine secretion
Hematopoietic Compartment
- Erythroid and myeloid precursors (hematopoietic cells) undergo differentiation and maturation in marrow spaces before their release into vascular sinusoids
- Hematopoietic cells enter vascular sinusoids via diapedesis or proplatelet shearing
- Trabecular bone structurally supports the marrow
- Osteoblasts produce trabecular bone
- Endothelial cells sit on a basal lamina and separate the vascular sinusoidal lumens from marrow hematopoietic and stromal cells
Megakaryocytes and Platelet Production
- Megakaryocytes line vascular sinusoids and release cytoplasmic fragments (platelets) into sinusoidal lumens
- Thrombopoiesis refers to the production of platelets
- Thrombopoietin (Tpo) is the primary regulator of thrombopoiesis
- Platelets circulate in a quiescent form and become activated by binding platelet agonists, such as thrombin, adenosine diphosphate (ADP), and thromboxane
Hematopoietic Stem Cells and Differentiation
- Hematopoietic stem cells (HSCs) are self-renewing and give rise to cells with committed differentiation programs
- Hematopoietic cells undergo sequential divisions as they develop, resulting in progressively higher numbers of cells as they mature
- Cells also continue to mature after they have stopped dividing
- Hematopoietic cells can be conceptually divided into mitotic and postmitotic compartments
Bone Marrow Diseases and Disorders
- Bone marrow disease can result from hypoplasia, hyperplasia, dysplasia, aplasia, or neoplasia
- Blood cells can be affected by hemorrhage, consumption, neoplasia, altered distribution, or abnormal function
- Bone marrow evaluation is indicated in cases of suspected leukemia, metastatic neoplasia, infectious myelitis, or cytopenia(s) of unknown cause
- Multimodal evaluation, including gross and microscopic examination, complete blood count, and additional tests, is ideal for diagnosing bone marrow diseases
Learn about the structure and function of bone marrow, including the trabecular bone and periosteum.
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