We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
from PART I - PHYSIOLOGY
Published online by Cambridge University Press: 10 May 2010
Introduction
Platelets are small anucleated cell fragments, which are essential components of primary haemostasis. They are derived from the cytoplasmic fragmentation of a giant precursor cell, the megakaryocyte (MK). MKs arise and mature in the bone marrow, along with the other blood cell precursors, e.g. granulocytes and erythroblasts. 150 to 400 × 109/l platelets usually circulate within normal human blood with an average lifespan of approximately 10 days. Therefore one would predict that about 15 × 109 – 40 × 109 platelets have to be produced each day to maintain normal levels. Appropriate platelet production is not only dependent upon a normal rate of thrombopoiesis but also upon the delivery of platelets of the correct size and functionality with normal subcellular organization. Therefore, the qualitative as well as the quantitative aspects of thrombopoiesis will be discussed in this chapter.
Cellular aspect of platelet production
MK localization
Normal human MKs, are mainly located in the bone marrow (Fig. 2.1, see colour plate). They are often gathered into small groups usually up to three, which consist of different cells of various size, ploidy and maturation stages. They are usually located in close proximity to a vascular sinusoid: This is important as MKs and endothelial cells can communicate by many potential pathways: MKs contain mitogenic factors for endothelial cells, e.g. vascular endothelial growth factor (VEGF), whereas endothelial cells express receptors and adhesion molecules which can potentially retain MK close to the bloodstream where future platelets could be delivered.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.
