24.2: Mammalian Circulatory system

Partial Pressure

The pressure exerted by one gas in a mixture of gases.

Haemoglobin

Respiratory pigment in red blood cells that binds to oxygen and transports it to tissues.

Components of circulatory system

• coronary - provides blood to heart

• pulmonary - includes heart and lungs

• systemic - rest of body

Right Atrium

Upper chamber of the heart that receives blood from the systemic circuit and pushes blood into right ventricle

Right Ventricle

Heart chamber that receives blood from the right atrium and pumps it to the pulmonary circuit through pulmonary artery

Left Atrium

Upper chamber of the heart that receives blood from the pulmonary vein and pushes blood into left ventricle

Left Ventricle

Heart chamber with a thicker wall that pumps blood to the entire body via the aorta.

Aorta

The main artery that carries blood from the left ventricle to the systemic circuit.

Arterioles

Small vessels that arteries divide into before reaching capillaries.

Capillaries

Smallest blood vessels where gas and nutrient exchange occur.

Venules

Small vessels that capillaries converge into to return blood to the heart.

Veins

Vessels that return blood to the heart and lungs.

Epicardium

Outermost layer of the heart tissue.

Myocardium

Middle layer of the heart tissue made up of cardiac muscle cells.

Endocardium

Innermost layer of the heart tissue.

4 valves

• tricuspid - separates right atria and ventricle

• mitral/bicuspid - separates left atria and ventricle

• semilunar valves that ensures blood leaves the heart

  • pulmonary valve - in pulmonary artery on right side

  • aortic - in aorta on left side

heart valves

connective tissue for unidirectional blood flow and prevents back flow

Systole

The contraction phase of the cardiac cycle.

Diastole

The relaxation phase of the cardiac cycle.

Sinoatrial Node

Electrical node near the right atrial wall causing both atria to simultaneously contract and push blood into ventricles

Atrioventricular Node

Electrical node, between the right atrium and ventricle, it pauses for approx. 1/10th of second to allows blood to completely empty from the atria

Vasodilation

The dilation of blood vessels, which decreases blood pressure.

Vasoconstriction

The constriction of blood vessels, which increases blood pressure.

process of when oxygen enters lungs

oxygen mixes with residual air = decreases alveolar partial pressure of oxygen which increases oxygen uptake which diffuses through alveoli into neighbouring capillaries (lower partial pressure). Oxygen binds to haemoglobin in red blood cells which travels to tissues where partial pressure of oxygen is lower = oxygen dissociates from blood cells

movement of CO2

CO2 goes down its pressure gradient from tissue to blood and transported back to lungs where pressure gradient drives CO2 into the alveoli

cardiac cycle

coordination of systole and diastole. Electrical signal from sinoatrial node causes contraction of atria which pushes blood into ventricle. Signal reaches atrioventricular node which pauses before causing contraction of ventricles. Charge then spreads through bundle of His towards intraventricular septum into ventricles’ Purkinje fibres causing contraction of blood out of heart

why does blood travel faster in veins

Smooth muscles in vessels’ walls and compression from neighbouring skeletal muscles