6.2 The Blood System

William harvey

• arteries and veins were part of a single connected blood work (through capillaries)

• arteries pumped blood from the heart to the lungs and body tissues

• veins pumped blood to the heart from the lungs and body tissues

artia

• acts as reservoirs, by which blood returning to the heart is collected via veins

ventricles

• act as pumps, expelling the blood from the heart at high pressure via arteries

left side

• this side of the heart pumps oxygenated blood around the body (systematic circulation)

• has a much thicker muscular wall (myocardium) as it must pump blood much further

right side

this side of the heart humps deoxygenated blood to the lungs (pulmonary circulation)

arteries

• convey blood at high pressure from the heart ventricles to the tissues of the body and lungs

• narrow lumen to maintain a high blood pressure

• a thick wall containing an outer layer of collagen to prevent the artery from rapturing under the high pressure

• the walls contain an inner layer of muscle and elastic fibers to help maintain pulse flow (contract and stretch)

muscle fibers

• help to form a rigid arterial wall that is capable of withstanding the high blood pressure without rapturing

• it can contract to narrow the lumen, which, increases the pressure between pumps and help to maintain blood pressure through the cardiac cycle

elastic fiber

• allow the arterial wall to stretch and expand upon the flow of a pulse through the lumen

• the pressure is exerted on the arterial wall is returned to the blood when th artery returns to its normal size (elastic recoil)

  • the elastic recoip helps push the blood forwaed through the artery as well as maintain arterial pressure between pump cycles

capillaries

• exchange materials between the cells in tissue and blood travelling at low pressure (<10 mmHg)

  • arteries split into arterioles which in turn split into _____, decreasing arterial pressure as total vessel volume is increased

  • the branching of arteries into ____ therefore ensures blood is moving slowly and all cells are located near a blood supply

  • after material exhcange has occured, capillaries will pool into venules which will in turn collate into larger veins.

• they have a very small diameter which allow passage of only a single red bloof cell at a time (optimal exchange)

• it is made of a single layer of cells to minimize the diffusion distance for prmeable materials

• they are surrounded by a basement membrane which is permeable to necessary materials

• they man contain pores to further aid in the transport of materials between tissue fluid and blood

veins

• collects blood from tissues and convey it at a low pressure to the atria of the heart

• they have a very wide lumen to minimize blood flow for more effective return

• they have a thin wall containing less muscle and elastic fibers as blood is flowing at a very low pressure

• it possesses valves to prevent backflow and stop the blood from pooling at the lowest extremities

valves

because blood is flowing at a very low pressure in the veins, it makes it difficult for blood to move against the downward force of gravity, in order to maintain the circulation of the blood, ___ helps the vein my preventing backflow.

artery

vein

capillary

myogenic

the process of the cardiac compression arising within the heart tissue itself

• the signal for a heartbeat is initiated by the heart muscles rather than from brain signals.

SA node (sinoatrial node)

• located within the right atrium of the heart

• it is a specialized cluster of cardiomyocytes which direct the contraction of heart muscle tissue

• it acts as the primary peacemaker, controlling the rate at which the heart beats

  • it triggers 60-100 cardiac contractions per minute

  • if this fails, a secondary peacemaker (AV node) may maintain cardiac contractions roughly 40-60 bpm.

  • if both fail, a final tertiary peacemaker may coordinate contractions at a constant rate of roughly 30-40 bpm

• the interference of the peacemakers will lead to the irregular and uncoordinated contractions of the heart muscle