3: Platelet production, structure, and function Flashcards
Maturation sequence of megakaryoblast takes about
5 days
is the process in which
chromosomal material (DNA) and the other events of mitosis occur without subsequent division of the cytoplasmic membrane into identical daughter cells.
Endoreduplication
Is a 70,000 dalton molecule that circulates as a hormone in plasma and is the ligand that binds the megakaryocyte and platelet membrane receptor protein, MPL
Thrombopoietin (TPO)
Induces the proliferation and maturation of megakaryocytes and induces thrombocytopoiesis
Thrombopoietin (TPO)
Primary source of Thrombopoietin
Liver
Act in synergy with TPO to
induce the early differentiation of stem cells
Interleukin-3
Acts in the presence of TPO to enhance endometriosis, megakaryocyte, maturation, and thrombocytopoiesis.
Interleukin-6 & Interleukin-11
Three megakaryocyte lineage-committed progenitor stages arising from common myeloid progenitor:
Most primitive progenitor cell committed to megakaryocyte lineage
BFU-Meg
Three megakaryocyte lineage-committed progenitor stages arising from common myeloid progenitor:
Hundreds of colonies
BFU-Meg
Three megakaryocyte lineage-committed progenitor stages arising from common myeloid progenitor:
least mature
BFU-Meg
Three megakaryocyte lineage-committed progenitor stages arising from common myeloid progenitor:
Dozens of colonies
CFU-Meg
Three megakaryocyte lineage-committed progenitor stages arising from common myeloid progenitor:
Cannot divide but it retains DNA replication and cytoplasmic maturation for endomitosis
LD-CFU-Meg
Three megakaryocyte lineage-committed progenitor stages arising from common myeloid progenitor:
more mature progenitor
LD-CFU-Meg
Sequence of development from megakaryocyte to platelets:
Proliferation of progenitors to polypoidization
Nuclear endoreduplication
Cytoplasmic maturation
Formation of platelets
Is a form of mitosis that lacks telophase and cytokines (separation into daughter cells)
Endomitosis
Partially characterized form of mitosis unique to megakaryocytes in which DNA replication and cytoplasmic maturation are normal but cells lose their capacity to divide.
Endomitosis
MK-I stage or Megakaryoblast Cannot be reliably distinguished from bone marrow
myeloblasts or pronormoblasts
Terminal megakaryocyte differentiation:
Vague clue: plasma membrane blebs
MK-I stage or Megakaryoblast
Terminal megakaryocyte differentiation:
Least differentiated precursor
MK-I stage or Megakaryoblast
Begins to develop most of its cytoplasmic ultrastructure, including procoagulant-laden a-granules, dense granules, and demarcation system
MK-I stage or Megakaryoblast
Is a series of membrane-lined channels that invade from the plasma membrane and ultimately delineates the individual platelets during thrombocytopoiesis
DEMARCATION SYSTEM
Is biologically identical to the megakaryocyte plasma membrane
DEMARCATION SYSTEM
Nuclear lobularity first becomes apparent as an indentation at the 4N replication stage
MK-II stage or Promegakaryocyte
Vague clue: Indentation in the nucleus
MK-II stage or Promegakaryocyte
The most abundant
MK-III stage or Megakaryocyte
Are the largest cells in the bone marrow and possess multiple chromosome copies
MK-III stage or Megakaryocyte
MK-III stage or Megakaryocyte size in diameter
30-50 um
Nucleus is intensely indented or
lobulated
MK-III stage or Megakaryocyte
Distinctive feature: it is not multinucleated
MK-III stage or Megakaryocyte
A single megakaryocyte may shed to
2000 to 4000 platelets
platelet lifespan
8 to 9 days
concentration of platelets
150-400 x 10^9/L
Average diameter of platelet
2.5 um
MPV of platelet:
8-10 fL
Resting platelets are
biconvex
Platelets are produced directly from the
megakaryocyte cytoplasm
platelets on the circulation
⅔
platelets found on the spleen
⅓
The platelet is composed of about
60% protein,
30% lipid,
8% carbohydrate,
various mineral,
water, and
nucleotide
Sometimes known as stress platelets, appear in compensation for thrombocytopenia
Reticulated Platelets
Are markedly larger than ordinary mature circulating platelets
Reticulated Platelets
Size of Reticulated Platelets in diameter
6 um
MPV of Reticulated Platelets
12-14 fL
Carry free ribosomes and fragments of rough endoplasmic reticulum
Reticulated Platelets
Stain for Reticulated Platelets
Nucleic acid dye (Thiazole Orange)
Stain for Reticulocytes
Supravital stain (New Methylene Blue)
