6.2: Blood system Use stethoscopes listen to heart beat. Microscopes and blood slides. What types of cells are you looking at? What do you already know? How did we acquire this knowledge?

William Harvey (1578 – 1657) English physician First known person to completely describe the detail for the circulatory system and the properties of blood.

Published 1889, William Harvey explaining circulatory system using a deer to Chares I (Charles was eventually executed which concluded the English Civil war 1649)

His work… Demonstrated that blood flows in one direction in larger blood vessel's (unidirectional) and these vessels contain valves to prevent back flow. Also demonstrated that the heart pumps blood out in arteries, and blood returns in the veins ready to be ‘recycled’ by the body He predicted the existence of capillaries (no microscopes yet) Blood was seen flowing in capillaries in 1660, after his death. *before Harvey, it was believed blood was consumed by the body

Harvey disproved theories by Galen Galen was an ancient Greek philosopher. Galen’s theories included the ‘vital spirit’ (for details see page 290). Harvey would never have been able to disprove Galen’s theories without evidence from systematic scientific investigations. “Diligent observation is therefore requisite in every science, and the senses are frequently to be appealed to. We are, I say, to strive after personal experience, not to rely on the experience of others, without which no one can properly become a student of any branch of natural science” Harvey, W., 1651. On the Generation of Animals.

Blood plasma The body has 4–6 liters of blood. About 45% of blood volume is cells. The other 55% is plasma —a straw-colored fluid. Plasma is 90% water and 10% dissolved gases, salts, nutrients, enzymes, hormones, waste products, and plasma proteins.

Blood Composition Plasma Platelets White blood cells Red blood cell Blood consists of plasma, blood cells, nutrients, hormones, waste products, and plasma proteins. Red blood cell Whole Blood Sample Sample Placed in Centrifuge Blood Sample That Has Been Centrifuged

Blood Cells Blood Cells The cellular portion of blood consists of: red blood cells (erthrocytes) white blood cells (Leucocytes) platelets

Blood Cells Red Blood Cells The most numerous cells in the blood are the red blood cells. Red blood cells are called Erythrocytes Red blood cells transport oxygen.

Blood Cells Red blood cells get their color from hemoglobin. Hemoglobin is an iron-containing protein that transports oxygen from the lungs to tissues of the body.

Blood Cells Red blood cells (erythrocytes) look like disks that are thinner in the center. They are produced in red bone marrow. They have no nuclei. They live for about 120 days. Then they are destroyed by the liver.

Blood Cells White Blood Cells -- Leukocytes White blood cells do not contain hemoglobin. They are less common than red cells. White blood cells are produced in bone marrow. They contain nuclei. White blood cells may live for days, months, or years.

Blood Cells White blood cells are the “army” of the circulatory system—they guard against infection, fight parasites, attack bacteria.

Blood Cells There are many types of white blood cells. Phagocytes engulf (eat) and digest bacteria and other disease-causing microorganisms.

Blood Cells B Lymphocytes produce antibodies. Antibodies are essential to fighting infection and help to produce immunity to many diseases.

Arteries Thick muscular, elastic walls Blood away from heart Blood at v. high pressures No valves (except aorta & pulmonary artery) Blood flow is rapid in pulses (pulsatile) Figure 3, page 292. Sketch this diagram of the artery. Label: tunica externa, tunica media, tunica intima and lumen.

Arteries and pressure… Systolic pressure: highest pressure lumen widens, and the elastic stretches storing potential energy. Diastolic pressure: at the end of the heart beat, pressure falls. Stretched elastic fibers, squeeze blood in the lumen. Vasoconstriction: circular muscles in arteries contract, lumen narrows. Blood pressure increases. Controlled through hormones/nervous system – when might this happen? Vasodilation: opposite of vasoconstriction.

veins Blood back to heart Blood at lower pressure Thinner walls than arteries Can dilate and be flattened Contain valves Moderate speed blood flow Hold more blood than arteries, in a sedentary person, it has been estimated that 80% of the blood is in the veins. When skeletal muscles contract, they will often contract the nearby veins, acting like a pump. Any movement – walking, improves venous blood flow.

Veins and valves Prevent backflow A valve is described as a three cup-shaped flap of tissue (pocket valve) Ensure blood circulates in the correct direction.

Artery or vein?

Capillaries Microscopic Form network throughout body Blood at moderate pressure but low speed V. thin, permeable walls (10µm), materials easily exchange No valves Bruises are caused by damage to the capillaries. Capillaries are repaired quickly, hemoglobin is broken down into green and yellow bile pigments and are transported away. Using this knowledge, you could investigate the speed at which hemoglobin is removed…

Skill: identifying blood vessels Figure 6, page 294. 1. Sketch this diagram 2. Use this table to make sure you are able to distinguish between and correctly identify the different blood vessels.