Blood Flashcards
What are the functions of blood?
- Transport of gases, nutrients, and waste products
- Transport of processed molecules: e.g: a sustance produced in one organ and moved to a different location.
- Transport of hormones and enzymes
- Regulation of blood pH and osmosis
- Maintenance of body temp
- Protection against foreign substances
- Clot formation
What is blood composed of?
Blood is composed of a liquid matrix and formed elements (cells etc)
The liquid matrix is plasma, which is mainly composed of water and proteins.
The formed elements are platelets, white blood cells, and red blood cells.
Describe hematopoiesis in fetuses and after birth
Hematopoiesis is the process that produces the formed elements of the blood (white and red BCs, platelets).
In the fetus, H occurs in several tissues, including the liver, thymus, spleen, lymph nodes and red bone marrow.
After birth, it is confined primarily to the red bone marrow, but some WBCs are produced in lymphatic tissues.
All formed elements are derived from stem cells.
Why are red blood cells disk shaped?
For increased surface area during gas exchange. Also allows the RBC to fold in on itself to pass more easily through smaller blood vessels.
How long is a RBCs life span in a human male vs. female?
Approx. 120 days in male, 110 in female
Under what conditions is production of RBCs stimulated?
Low oxygen levels, which could be caused by several factors:
- decreased number of RBCs
- decreased or defective hemoglobin
- disease of the lungs
- high altitude
- inability of cardiovascular system to deliver blood to tissues
- increased tissue demand of oxygen (as occurs during endurance exercises)
What are the two categories of white blood cells, and what separates them?
Granulocytes, which contain large cytoplasmic granules.
Agranulocytes, which contain very small granules that cannot easily be seen with the light microscope.
What are the three types of granulocytes, and what characteristics do they have?
Neutrophils, basophils and eosinophils.
Neutrophils: phagocytize microorganisms and other foreign substances. Most common white blood cell.
Basophils: least common. Release histamines and other chemicals that promote inflamation. Also releases heparin to prevent formation of clots.
Eosinophils: involved with inflammatory responses associated with allergies and asthma. Destroys certain worm parasites.
Where/how are platelets produced?
Platelets are produced in the red bone marrow from large cells called megakaryocytes.
What is a platelet?
Mini fragments of cells, each consisting of a small amount of cytoplasm surrounded by a cell membrane.
What are the three stages of preventing blood loss?
- vascular spasm
- platelet plug formation
- blood clotting
Explain the processes of vascular spasm.
A vascular spasm is when a blood vessel constricts after an injury to prevent blood loss. It is stimulated by chemicals released by cells of the damaged blood vessel wall and by platelets.
Explain the process of platelet plug formation.
A platelet plug formation begins when platelets adhere to the collagen exposed by blood vessel damage. This is called platelet adhesion, which is mediated through von Willebrand factor, a protein. After platelets adhere to collagen, they become activated, change shape, and releases chemicals which activates more platelets.
Explain the process of blood clotting.
Inactive clotting factors in the plasma are activated by exposure to connective tissue or by chemicals released from tissues. Through a series of reactions, the activated clotting factors form prothrombinase.
Prothrombinase converts prothrombin to thrombin.
Thrombin then converts fibrinogen to fibrin (the clot).
Mention two anticoagulants that prevent the blood from clotting under normal circumstances.
Antithrombin and heparin (which is released by basophils).
