1. Capillary Action and Blood Components
Biology 20
Unit D: Body Systems – Circulation

2. Remember….
Capillaries are so small that blood cells can only pass through single file
Important because they are the only vessels THIN enough for diffusion of nutrients, wastes, and gases

3. Network Capillaries work in NETWORKS or BEDS throughout body
Bed is formed between a branch of an artery and a branch of a vein

4. Precapillary Sphincters
Blood flow not always constant in capillaries
If cells beside certain capillaries don’t need to be serviced by the blood, blood flow can be stopped from going to that capillary

5. Precapillary Sphincters Con’t
Done by PRECAPILLARY SPHINCTERS that contract and close the opening to that specific capillary
Blood then passes right from artery to vein through main capillary

6. When do the these sphincters constrict blood flow?
After eating
Capillaries feeding certain muscles are closed
All the capillaries of the digestive system are open
Ie) capillaries in villi of small intestine
While exercising
Capillaries feeding muscles are open, and the some capillaries feeding the digestive system would be closed

7. Interstitial Fluid Liquid that surrounds body cells and capillaries
Material exchanged between body cells and capillaries must travel through this fluid

8. Sections of Capillaries
Arterial end
Blood is bright red because hemoglobin in red blood cells contain lots of oxygen
Mid-section
Where diffusion of materials takes place
Direction of diffusion decided by a material’s concentration gradient
Venous end
Blood is blue looking because there is minimal oxygen present and lots of carbon dioxide

10. Blood Flow Speed in Capillaries
Slower than any other part of system
Allows time for diffusion of materials
Pressure is lower than arteries, but still more than veins
Ensures blood keeps moving

11. Blood Components 2 main elements: fluid and solid portions
PLASMA = fluid portion
FORMED PORTION = solid portion

12. Plasma
Consists of water, dissolved gas, proteins, sugars, vitamins, minerals, hormones, and waste products
55% of blood volume

13. Formed Portion Consists of: All produced in bone marrow
red blood cells
white blood cells
platelets
All produced in bone marrow
45% of blood volume

14. Red Blood Cells (RBC) Aka Erythrocytes
~44% of the total volume of blood
Specialized for O2 transport
The O2 carrying capacity of blood is based on # of RBC present and the amount of HEMOGLOBIN on each
Mature RBC has no nucleus

15. Hemoglobin Each RBC contains ~280 million Iron-containing
Allows large sums of O2 to be transported in blood
Special properties that let it chemically bind with O2
Then releases O2 by diffusion to cells that need it

16. Hemoglobin Con’t
After CO2 (waste) is diffused into the blood, it enters the RBC where a small amount is chemically binded to hemoglobin

17. Anemia Disorder that occurs when there are:
too few RBC OR
too little hemoglobin inside the RBC in blood
These deficiencies reduce the amount of O2 that is flowing through body
May be caused by not eating enough iron (mineral)

18. White Blood Cells (WBC)
AKA Leucocytes
Apart of body’s response to infection
~1% of total blood volume (X2) when fighting infection
Colorless and have a nuclei
Divided into 3 groups:
Granulocytes
Monocytes
Lymphocytes

19. 1. Granulocytes Consist of:
Neutrophils
Basophils
Eosinophils
Typically found circulating in blood with granulocytes engulfing foreign bodies

20. 2. Monocytes
Can leave bloodstream and become further specialized into MACROPHAGES (destroy bacteria – engulf it)
Typically found circulating in blood with granulocytes engulfing foreign bodies

21. 3. Lymphocytes Some produce ANTIBODIES
Proteins that incapacitate pathogens and allow them to be easily detected and destroyed

22. Platelets
Pieces of cells that form when larger cells in the bone marrow break apart
No nucleus
Breaks down quickly in blood
Play key role in blood clotting

24. Stages of Clotting Blood vessel broken due to injury
Substances released at site to attract platelets
Platelets at site rupture, releasing chemicals that combine with blood components to produce enzyme called THROMBOPLASTIN

25. Clotting Con’t
As long as there is Ca+ present, THROMBOPLASTIN will react with PROTHROMBIN to produce THROMBIN
Prothrombin is a plasma protein produced in liver
THROMBIN (enzyme) reacts with FIBRINOGEN (protein) to produce FIBRIN
FIBRIN forms mesh strands around injured area, thus preventing more blood loss
Forms clot

27. Plasma Fluid portion of blood Carries all blood cells Is a mixture:
92% water
7% Blood Proteins
0.1% Organic Substances (ie.urea)
0.9% Inorganic Ions (sodium, chlorine, magnesium, potassium, calcium, biocarbonates, phosphates, etc)

28. Plasma Con’t
CO2 is dissolved in the water portion of plasma when transported in the blood
Forms carbonic acid in cytoplasm of RBC
Then diffuses out of RBC into the plasma as bicarbonate ions and is carried from tissues to the lungs for gas exchange