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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

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

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)

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