HEMATOPOIESIS Flashcards
what is red marrow composed of
hematopoietic cells and macrophages
how are hematopoietic cells and macrophages arranged?
extravascular cords
how do erythroblasts develop in the red marrow?
they develop in small clusters, and the more mature forms are located adjacent to the outer surfaces of the vascular sinuses
where are megakaryotes located in the red marrow
adjacent to the walls of the vascular sinuses, which facilitates the release of platelets into the lumen of the sinus
the layer under adventitial cells
basement membrane
why do adventitial cells contract?
this allows mature blood cells to pass through the basement membrane and interact with the endothelial layer
function of megakaryoctes in the red marrow
they facilitate the release of platelets into the limen of the sinus
what supplies nutrition and oxygenation of the marrow
nutrient and periosteal arteries
this artery only supplies blood to the marrow
nutrient artery
this artery provides nutrients for the osseous bone and the marrow
periosteal artery
which vein does blood exit the marrow
central longitudinal vein
nurtures and protexts HSCs and is important in regulating a balance among their quiescence, self-renewal, and differentiation
hematopoietic inductive microenvironment, or niche
true or false
as the site of hematopoiesis transitions, so must the microenvironmental niche for HSCs
true
_______ form an extracellular matrix in the niche to promote cell adhesion and regulate HSCs through complex signaling networks involving cytokines, adhesion molecules, and maintenance proteins.
a. reticular adventitial cells
b. stromal cells
c. endothelial cells
d. adipocytes
b
what are the key stromal cells that support HSCs in bone marrow niches
osteoblasts, endothelial cells, mesenchymal stem cells, CXCL 12-abundant reticular cells, perivascular stromal cells, glial cells, and macrophages
intimate interaction with this factor maintains the quiescent state of HSCs
thrombopoietin-producing osteoblasts
true or false
intimate interaction with this factor maintains the quiescent state of HSCs
opposing srudies suggest that vascular cells are critical to HSC maintenance through CXCL12, which regulates migration of HSCs to the vascular niche
true
overlapping niches produces which of the following:
a. inhibition of functionality
b. provides multiple signals simultaneously
c. delineation between transcription factors and regulators
d. HSCs become predominantly quiescent
b
is the major site of hematopoiesis during the second trimester of fetal development
liver
what are the functions of hepatocytes?
protein synthesis and degradation coagulation factor synthesis carbohydrate and lipid metabolism drug and toxin clearance iron recycling and storage hemoglobin degradation
how are hepatocytes arranged?
anatomically, they are arranfes in radiating plates emanating from a central vein
what are kupffer cells
they are macrophages of the liver that remove senescent cells and foreign debris from the blood that circulates through the liver. they also secrete mediators that regulate protein synthesis in the hepatocytes.
what are senescent cells?
The process of growing old. In biology, senescence is a process by which a cell ages and permanently stops dividing but does not die. Over time, large numbers of old (or senescent) cells can build up in tissues throughout the body. These cells remain active and can release harmful substances that may cause inflammation and damage to nearby healthy cells. Senescence may play a role in the development of cancer and other diseases.
this is known as the liver’s response to infectious agents or in pathologic myelofibrosis of the bone marrow characterized by the maintenance of hematopoietic stem and progenitor cells to produce various blood cells
extramedullary hemetopoiesis
the largest lymphoid organ in the body
spleen
where is the spleen located?
below the diaphragm behind the fundus of the stomach in the upper left quadrant of the abdomen
how much blood does the spleen contain in healthy individuals?
350 mL
what are the three types of splenic tissue?
white pulp, red pulp, and marginal zone
this splenic tissue consists of scattered follicles with germinal centers containing lymphocytes, macrophages, and dendritic cells
white pulp
what is PALS?
or periaortal lymphatic sheath, is the region made from the aggregates of T lymphocytes surrounding arteries that pass through the white pulp
what can be located in the periaortal lymphatic sheath?
lymphoid nodules containing B lymphocytes
where are activated B lymphocytes found?
germinal centers
what is the marginal zone
this surrounds the white pulp and forms a reticular meshwork containing blood vessels, macrophages, memory B cells, and CD4+ cells
what is the red pulp?
it is composed primarily of vascular sinuses separated bu cords of reticular cell meshwork (cords of bilbroth) containing loosely connected specialized macrophages
serves as the storage site for platelets
spleen
there are two methods in which the spleen removes senescent or abnormal RBCs. what are these?
culling, and pitting
what is culling?
the spleen phagocytoses cells with subsequent degradation of cell organelles
what is pitting?
splenic macrophages remove inclusions or damaged surface membrane from the circulating RBCs
through which artery does blood enter the spleen?
central splenic artery located at the hilum and branches outward through the trabeculae
