Heart and the Blood Vessels Flashcards
Circulatory System in Mammals
Closed, blood is confined to vessels
Double, passes through the heart for both the 2 complete circuits of the body
Atrium
thin walled
elastic
stretches as it collects blood
Ventricle
thick
muscular
contracts strongly to send blood to body or lungs
Right Ventricle
pumps deoxygenated blood, via the pulmonary artery, to the lungs, thinner muscular wall
Left Ventricle
pumps oxygenated blood, via the aorta, to rest of the body, thicker muscular walls.
Vena Cava
brings deoxygenated from the body excluding lungs to the right atrium
Pulmonary Vein
brings oxygenated blood to the left atrium from the lungs
Pocket Valves
Valves in veins that prevent the backflow of blood ensure blood in veins travels back to the heart.
Atrioventricular (AV) Valves
Valves between atria and ventricles.
Prevents backflow of blood from ventricles into atria
Open when pressure in atria is greater than pressure in ventricles.
Semilunar Valves
Valves between left ventricle and aorta and right ventricle and pulmonary artery.
Prevents backflow of blood from aorta and pulmonary artery into ventricles.
Open when pressure in ventricles is greater than in aorta and pulmonary artery
Cardiac Diastole
Ventricles and Atria relaxed
Atria fill with blood from vena cava and pulmonary vein.
Pressure in the atria increase above pressure in ventricles, AV valves open.
Blood flows into the ventricles passively.
Pressure in the ventricles lower than in aorta and pulmonary artery so SL valves are closed.
Atrial Systole
Atria contract (ventricles relaxed), volume of atria decreases, pressure of atria increases forcing any remaining blood into the ventricles.
AV valves still open, SL valves still closed
Ventricular Systole
Ventricles contract (atria relax).
Volume of ventricles decrease, pressure in ventricles increases and is greater than in atria, AV valves to shut to prevent backflow.
Pressure in ventricles greater than in aorta or pulmonary artery, so SL valves open, blood pushed from ventricles and out of heart through aorta and pulmonary artery.
Cardiac Output
Stroke Volume x Heart Rate
Stroke Volume: the volume of blood pumped out of the left ventricle during one cardiac cycle
Vein Structure/Function
Veins receive blood at very low pressures
Wall of the vein is relatively thin with thinner layers of collagen, smooth muscle and elastic fibres
Lumen is much larger
Artery Structure/Function
Transport high pressure blood away from the heart.
Wall of the artery is relatively thick with layers of collagen, smooth muscle and elastic fibres
Elastic fibres allow the artery wall to expand around high pressure blood when the heart contracts, these fibres then recoil when the heart relaxes
Narrow lumen maintains high blood pressure
Arteriole Structure/Function
Arteries branch into narrower blood vessels called arterioles which transport blood into capillaries
Arterioles have a lower proportion of elastic fibres and a large number of muscle cells
Muscle cells allows them to contract and close their lumen to stop blood flow to specific organs, such as during exercise
Tissue Fluid
A watery liquid containing glucose, amino acids, oxygen and other nutrients. (similar to blood plasma but without the proteins as they are too big to leave capillaries)
Bathes all most all cell thus delivering the glucose etc. to tissues and removes waste materials.
Exchange of substances between cells and the blood occurs via the tissue fluid
Movement of Tissue Fluid Out of Capillaries
Heart pumping blood creates hydrostatic pressure at the arteriole end of the capillaries.
Opposed by water potential in the capillaries being lower than in tissues due to the plasma proteins and hydrostatic pressure of tissue fluid outside of capillaries.
Hydrostatic pressure inside capillaries overcomes this and forces the tissue fluid out of the pores but the pressure is only enough to force small molecules out but not proteins (ultrafiltration).
Movement of Tissue Fluid Into Capillaries
Tissue fluid leaves capillaries, hydrostatic pressure in the capillaries decreases
Hydrostatic pressure in the venous end of the capillaries is lower than in the tissue fluid outside the capillaries. Tissue fluid moves back in.
Proteins in the blood plasma means water potential in capillaries is lower than outside, water leaves tissues into capillaries down a water potential gradient.
Tissue Fluid and Lymphatic System
Not all tissue fluid goes back to capillaries.
Rest goes into the lymphatic system as lymph.
This moves along the vessels in the lymph system.
Backflow prevented by valves.
The lymph re enters the blood stream through veins close to the heart
