BLOOD CLOTTING,
FORMATION, &
DISORDERS
February 19-20, 2015
Hemostasis
Hemostasis is the process of
blood clotting
• Occurs when small blood
vessel (capillary) is damaged
• Clot seals the blood vessel
until the it regenerates
• Occurs in just 3-6 minutes
Process of Hemostasis
Three major events occur, all beginning the moment the
vessel is damaged:
1) Vasoconstriction
2) Platelet plug formation
3) Coagulation of blood
Coagulation takes longer, and
is completed after
vasoconstriction and platelet
plug formation occur
Process of Hemostasis
Watch me!
This is a
simplified
overview of
the clotting
cascade
Hemostasis: Review & Connections
What is the recommended way to treat a bleeding wound (until
you see a doctor)? Why?
Gauze and pressure
The gauze acts much like collagen fibers – provide a rough surface
that helps activate platelets.
Pressure manually constricts blood vessels and also increases the
release of thromboplastin, which helps initiate coagulation.
Never remove gauze or a bandage from an actively bleeding
wound. Why?
Removing the bandage will remove both clotting factors and the
beginnings of a platelet plug or blood clot, causes an increase in
bleeding.
Hemostasis: Review & Connections
How is blood clotting an example of positive feedback?
Which part(s) of the process best exemplify positive
feedback?
(Turn & Talk – 2 min)
Platelet plug formation
Activated platelets release chemicals that cause more
platelets to activate, until a large number of platelets clump
together forming a plug.
Hemostatic Disorders – Blood Clots
A thrombus is a blood clot that forms in an unbroken vessel. A
large thrombus may block blood flow, causing tissue death.
An embolus is a blood clot
that forms then breaks away
and floats freely in the blood
vessels. An embolus may
then lodge in a capillary and
block blood flow.
coronary thrombosis
cerebral embolism –
pulmonary embolism –
Hemostatic Disorders – Blood Clots
A thrombus is a blood clot that forms in an unbroken vessel. A
large thrombus may block blood flow, causing tissue death.
An embolus is a blood clot
that forms then breaks away
and floats freely in the blood
vessels. An embolus may
then lodge in a capillary and
block blood flow.
coronary thrombosis – in heart
cerebral embolism – in brain
pulmonary embolism – in lungs
Hemostatic Disorders – Blood Clots
Causes of thrombus
• Injury to blood vessel or build-up of fatty
plaques
 Both create rough surfaces inside
vessel, which may activate platelets
• Poor blood circulation
 Clotting factors may accumulate
Immobility increases the risk of
deep vein thrombus in legs!
Hemostatic Disorders – Blood Clots
Blood thinners (such as warfarin, aspirin, and heparin) can be
used to prevent thrombus
Aspirin –
blocks thromboxane
reduces formation of platelet plug
Wafarin –
blocks production of certain clotting factors
reduces coagulation interrupting clotting cascade
Heparin –
helps inactivate thrombin
reduces coagulation by preventing conversion of
fibrinogen to fibrin
Review your notes – how exactly does each of these reduce
clotting?
Hemostatic Disorders - Hemophilia
Causes
• lack of one or more clotting factors
• Recessive sex-linked trait (more common in men)
Symptoms
•
•
•
•
Prolonged bleeding even from minor injuries
Excessive bruising
Bruised and swollen joints
Excessive clumsiness and falling
Treatment
• Intravenous injection of clotting
factors
• Donated plasma
• Synthetic clotting factors
Hematopoiesis
Hematopoiesis is the process of blood formation.
• Occurs in the red bone marrow
Where is this found?
In babies, nearly all bones have red marrow
In adults, just the flat bones and epiphyses
• All blood cells and platelets derive from hemocytoblast stem cells
Erythrocyte life cycle and production
Develop in red marrow (for 3-5 days)
Eject nucleus, then enter blood stream.
Red blood cells life for 3-4 months
Digested by phagocytes
Production is controlled by
hormone erythropoietin.
Erythropoietin release is
stimulated by low levels of
O2 in blood.
Erythrocyte life cycle and production
Develop in red marrow (for 3-5 days)
Eject nucleus, then enter blood stream.
Red blood cells life for 3-4 months
Digested by phagocytes
Why is there no hormone to
decrease RBC production?
- High numbers of RBCs
don’t cause major
problems
- High levels are temporary.
RBC levels will decline
due to death of cells.
Erythrocyte life cycle and production
Develop in red marrow (for 3-5 days)
Eject nucleus, then enter blood stream.
Red blood cells life for 3-4 months
Digested by phagocytes
Why do world-class athletes train
at high altitude before major
competitions?
-
High altitude has lower
oxygen levels, which
stimulates the production of
erythrocytes
- The high levels of erythrocytes
will persist for a while after
leaving high altitude
Closure
• What were our objectives, and what did you learn about
them?
• What was our learner profile trait and how did we
exemplify it?
• How does what we did today address our unit question?
Exit Ticket
Make mini posters illustrating the following terms.
The posters should
• be in color
• prominently feature the term
• have both a picture
• a definition / explanation of the term
Exit Ticket
Neutrophil
hemostasis
Fibrin
hemophilia
Basophil
Serotonin
fibrinogen
agglutination
Eosinophil
Platelet plug
Platelet factor 3
Albumin
Lymphocyte
Thromboplastin
coagulation
Antibody
Monocyte
Prothrombin
Clotting factor
Antigen
platelet
thrombin
vasoconstriction
Plasma
hemocytoblast erythropoietin
Thrombus
Erythrocyte
hemotopoeisis Prothrombin
activator
embolus
leukocyte