The Blood and heart

blood

Composition and Functions of Blood Components Connective tissue Living cells (formed elements) are suspended in a non living fluid matrix (plasma) Physical Characteristics and Volume slightly alkaline (pH 7.35-7.45) Accounts for about 8% of body weight Volume is 5-6 liters Plasma makes up 55% of volume and formed elements make up 45%

Plasma The liquid part of the blood Over 100 different substances are dissolved in the fluid Nutrients, electrolytes, gases, hormones, plasma proteins, various wastes

Plasma Proteins Most abundant solutes in the plasma Made by the liver (except antibodies and hormones) Albumin Carrier to shuttle certain molecules through circulation Blood buffer Contributes to osmotic pressure (keeps water in the blood) Clotting proteins Stem blood loss after injury Antibodies Protect body from pathogens

Formed Elements Erythrocytes (red blood cells) Function to ferry oxygen in the blood to all cells of the body Carry hemoglobin Iron bearing protein that carries the oxygen Anucleated (without a nucleus) Makes them biconcave disks Can roll up to fit through capillaries Have large surface area perfect for gas exchange Normally about 5 million cells per cubic millimeter of blood

Formed Elements cont. Leukocytes (white blood cells) Platelets 4,000-11,000 per square millimeter of blood Part of the immune system Can leave the blood vessel Platelets Fragments of megakaryocytes Megakaryocytes are cells that are housed in the bone marrow, only their pieces are found in the blood 300,000 per square millimeter Needed for clotting blood during vessel damage

Hematopoiesis Occurs in the red bone marrow After the cells mature they are discharged into the blood stream On average 100 billion new cells are made every day All formed elements originate from a hemocytoblast stem cell

Formation of Red Blood Cells Live only 100-120 days Remains are eliminated in the spleen and liver Rate of production is controlled by a hormone erythropoietin Made by the kidneys in response to blood oxygen levels

Formation of White Blood Cells and Platelets Stimulated by hormones Colony stimulating hormone Interleukins Released in response to inflammatory chemicals, bacterial toxins, and increased body temperature

Hemostasis

Hemostasis Normally takes 3-6 minutes Step 1: Vascular spasm Immediate response to blood vessel injury is vasoconstriction Also stimulation of pain receptors and release of serotonin Spasms narrow the blood vessel at that point decreasing blood loss until clotting can occur Step 2: Platelet plug forms When vessels are broken the underlying collagen fibers are exposed Platelets become sticky and cling to the damaged site These anchored platelets release chemicals that enhance the vascular spasms and attract more platelets

Hemostasis cont Step 3: Coagulation events occur Tissue factor is released PF3 interacts with vitamin K and calcium ions to form an activator that triggers the clotting cascade The cascade leads to the formation of a fibrin meshwork that traps the red blood cells

The cardiovascular system