43 Questions
What is the main function of hemostasis?
Prevention of blood loss
Which is NOT a mechanism for achieving hemostasis?
Blood clot removal
What is the normal concentration of platelets in the blood?
150,000 - 300,000 per microliter
What happens to platelets when they come in contact with a damaged vascular surface?
They adhere to the vessel wall and each other, forming a plug
What is the life span of platelets in the blood?
8 to 12 days
What is the first mechanism for achieving hemostasis?
Vascular constriction
What are platelets also called?
Thrombocytes
What structures form on the surfaces of platelets when they come in contact with damaged vascular surfaces?
'Pseudopods' and 'sticky' surfaces
What initiates the clotting process in the blood vessel?
Damaged tissue and platelets
Which test is used to evaluate capillary resistance by counting the number of petechial hemorrhages?
Hess test
What does the Duke's method of bleeding time test involve?
Puncturing the thumb and touching the bleeding site with a filter paper every 30 seconds
What is the normal range for bleeding time as per Ivy's method?
2 - 8 minutes
Which condition causes excessive bleeding in humans due to platelet deficiency?
Thrombocytopenia
What is responsible for cleaning up extra and old clots by breaking them down?
Fibrinolysis
What type of abnormal clot freely travels through the bloodstream?
Embolus
"What is activated by tissue plasminogen activator (t-PA) to break down unnecessary blood clots?"
Plasminogen
"What is the function of the cuff of the sphygmomanometer in Duke's method of Bleeding Time test?"
To maintain pressure at 40 mmHg
"What does an abnormal clot that develops in a blood vessel occlude?"
Small blood vessels only
"What does an emboli refer to?"
A clot that freely circulates through the bloodstream
Platelets are formed in the liver from megakaryocytes.
False
Vascular constriction is not a mechanism for achieving hemostasis.
False
The normal concentration of platelets in the blood is less than 100,000 per microliter.
False
Platelets have a life span of 12 to 16 days.
False
Platelets have a nucleus.
False
The formation of a platelet plug involves platelets adhering to smooth vessel walls.
False
Vascular constriction results from factors released from undamaged tissue.
False
Platelets undergo phagocytosis in the spleen after 12 to 15 days.
False
The growth of fibrous tissue into the blood clot occurs to dissolve the clot and prevent further damage to the vessel.
False
Platelets do not change their characteristics upon contact with a damaged vascular surface.
False
The formation of a blood clot is not a mechanism for achieving hemostasis.
False
Hemostasis does not involve the eventual growth of fibrous tissue into the blood clot.
False
The injured tissues and vascular endothelium release tissue plasminogen activator (t-PA) immediately after the clot has stopped the bleeding.
False
The Hess test involves applying the cuff of the sphygmomanometer above a marked circle and maintaining pressure for five minutes.
True
The Duke's method of bleeding time test involves wrapping the cuff of the sphygmomanometer around the upper arm and inflating it to a pressure of 50 mmHg.
False
The normal range for bleeding time as per Ivy's method is 2 – 6 minutes.
False
The Clotting time (CT) is the time taken for the blood to clot inside the vascular system.
False
Vitamin K deficiency, hemophilia, and thrombocytopenia are conditions that cause excessive bleeding in humans due to platelet deficiency.
False
An abnormal clot that develops in a blood vessel is called an emboli.
False
The Hess test determines capillary resistance by counting the number of spots formed on a filter paper after puncturing the thumb.
True
Platelets are also called thrombocytes.
True
Thromboembolic conditions involve a freely circulating clot called a thrombus.
False
The Duke's method of bleeding time test provides information about the function of platelets and the capillary wall.
True
Thromboembolic conditions prevent blood from flowing normally by occluding small blood vessels.
True
Study Notes
Hemostasis
- The main function of hemostasis is to prevent excessive bleeding when a blood vessel is injured.
- Hemostasis involves three main mechanisms: vascular constriction, platelet plug formation, and blood coagulation.
Platelet Function
- Platelets, also called thrombocytes, are formed in the bone marrow from megakaryocytes.
- The normal concentration of platelets in the blood is 150,000-450,000 per microliter.
- Platelets have a life span of 12 to 16 days.
- When platelets come into contact with a damaged vascular surface, they undergo a change in their characteristics, leading to the formation of pseudopodia and release of granules.
Platelet Plug Formation
- Platelet plug formation is the first mechanism for achieving hemostasis.
- When platelets come into contact with a damaged vascular surface, they adhere to the surface, forming a platelet plug.
- On the surface of platelets, pseudopodia form and granules are released, leading to platelet activation.
Blood Clotting
- The formation of a blood clot is the second mechanism for achieving hemostasis.
- The clotting process is initiated by the release of tissue plasminogen activator (t-PA) from injured tissues and vascular endothelium.
- t-PA activates plasminogen, which breaks down fibrin clots.
Bleeding Time Test
- The bleeding time test is used to evaluate platelet function and capillary resistance.
- Duke's method of bleeding time test involves inflating a cuff on the upper arm to a pressure of 40 mmHg and making a small puncture wound to measure the time it takes for bleeding to stop.
- The normal range for bleeding time as per Ivy's method is 2-6 minutes.
Clotting Disorders
- Thrombocytopenia is a condition that causes excessive bleeding due to platelet deficiency.
- Thromboembolic conditions involve the formation of abnormal clots that can occlude small blood vessels.
- Plasmin activators, such as t-PA, break down unnecessary blood clots.
Other
- The Hess test, also known as the tourniquet test, is used to evaluate capillary resistance.
- An emboli refers to an abnormal clot that breaks loose and travels through the bloodstream.
- Fibrous tissue growth into the blood clot helps to dissolve the clot and prevent further damage to the vessel.
Test your knowledge of the mechanisms involved in hemostasis, the process of preventing blood loss when a blood vessel is damaged. This quiz covers topics such as vascular constriction, platelet plug formation, blood clotting, and fibrous tissue growth.
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