Chapter 6B Flashcards
Under the influence of the hormone
thrombopoietin (TPO, produced primarily in
liver with much smaller amounts being
made in the kidney and bone marrow),
myeloid stem cells develop into
megakaryoblasts.
- Megakaryoblasts transform into
megakaryocytes, huge cells that splinter into
2000 to 3000 fragments. - Each fragment, enclosed by a piece of the
plasma membrane, is a X - Platelets break off from the megakaryocytes
in red bone marrow and then enter the
blood circulation.
platelet
Their granules contain chemicals that,
once released, promote X.
* Platelets help stop blood loss from
damaged blood vessels by forming a
platelet plug.
blood clotting
Hemostasis is a sequence of responses that stops ….
bleeding
Three mechanisms reduce blood loss:
1. vascular spasm
2. platelet plug formation
3. …. (coagulation)
blood clotting
Platelets store an impressive array of chemicals:
* clotting factors: ADP, ATP, Ca2+ and serotonin
* hormone platelet-derived growth factor: promote cell proliferation
* fibrin-stabilizing factor: helps to strengthen a blood clot
* enzymes
* …..
lysosomes
Platelet plug formation occurs as follows:
1. Platelet X: platelets contact and stick to
parts of a damaged blood vessel.
- Platelet release reaction:
* Due to adhesion, the platelets become
activated: they extend many projections that
enable them to contact and interact with one
another, and begin to liberate the contents of
their vesicles.
* Nearby platelets are activated and
vasoconstrictors release causes contraction of
vascular smooth muscle which decreases
blood flow through the injured vessel - Platelet aggregation (platelet plug)
adhesion
Serum: is blood plasma minus the X proteins.
clotting
Blood clot: It consists of a network of insoluble protein
fibers called X in which the formed
elements of blood are trapped.
fibrin
Clotting is a complex cascade of enzymatic reactions in
which each clotting factor activates many molecules of
the next one in a fixed sequence.
* The blood-clotting cascade of reactions includes
…. feedback cycles.
* Finally, a large quantity of fibrin (insoluble protein) is
formed.
positive
- Clotting can be divided into three stages:
1. Two pathways (extrinsic pathway and intrinsic
pathway) lead to the formation of
prothrombinase. Once prothrombinase is
formed, the following steps are referred to as the
common pathway.
- Prothrombinase converts prothrombin (a plasma
protein formed by the liver) into the enzyme
…. - The thrombin converts soluble fibrinogen
(another plasma protein formed by the liver) into
insoluble fibrin. Fibrin forms the threads of the
clot
thrombin
If the blood takes too long to clot,
hemorrhage can occur. Eg. Hemophilia:
inherited bleeding disorder where the
blood doesn’t clot properly. It is caused
when blood does not have enough
X
clotting factor
If blood clots too easily, the result can be
X: clotting in an undamaged
blood vessel at a site of minor roughness
or at a developing atherosclerotic plaque
inside a blood vessel.
thrombosis
The clot itself (thrombus), may dissolve
spontaneously.
A blood clot, bubble of air, fat from
broken bones, or a piece of debris
transported by the bloodstream is
called an X.
When an embolus lodges in the lungs,
the condition is called X
embolism.
embolus
pulmonary
The fibrinolytic system dissolves small, inappropriate clots; it also dissolves clots at a site
of damage once the damage is repaired.
* Dissolution of a clot is called X.
fibrinolysis
