Blood cells develop in the bone marrow from a common stem cell in the process known as haematopoiesis. Once mature, cells are divided into groups that reflect their morphological and functional characteristics including the erythrocytes, or red blood cells, the granulocytes, the agranulocytes and the megakaryocytes.
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It is important that all aspects of haemostasis can be independently evaluated. This will help to identify the phase affected and to pinpoint what the abnormality is. There are tests available to assess primary haemostasis, secondary haemostasis and fibrinolysis.
Transfer of passive immunity in the bovine neonate occurs solely through maternal colostrum. This is in contrast to humans where placental transfer of immunity via specific Fc receptors is the predominant mechanism. However, inadequate transfer of immunity is a relatively commonly diagnosed problem affecting young stock. This is particularly the case in modern Holstein dairy herds, where large milk yields dilute the antibody concentration in the colostrum meaning relatively more must be consumed to have the same immunity transferred. Due to the lower yields and possibly other genetic reasons, this tends to be less of a problem in suckler herds.
The innate response to bacterial infection lies in its first-response role of detection of a foreign organism. By using the tools of Pattern-Recognition Receptors (PRRs), the innate response flags up problems while the adaptive response gets itself organized.
Phagocytosis is a very primitive system of defence against infection, having even been shown to exist in invertebrates and single cell organisms. The discovery was made in starfish larvae by Elle Metchnikoff who subsequently won the Nobel Prize for Medicine or Physiology in 1908. The process of phagocytosis itself is a form of endocytosis (cell eating), with vesicular internalisation being the method of removal of pathogens and dead cells (those that have undergone apoptosis, or Programmed Cell Death). This internalised vesicle is referred to as the "phagosome".