Heart and Blood Vessels Flashcards
What are the structures of the heart?
- Vena cava.
- Pulmonary artery.
- Pulmonary vein.
- Right atrium.
- Atrioventricular valves.
- Right ventricle.
- Apex.
- Left ventricle.
- Left atrium.
- Aorta.
What is the pulmonary circuit?
The right side of the heart sends deoxygenated blood from the body along the pulmonary artery to the lungs.
What is the system circuit?
The pump on the left side sends oxygenated blood from the lungs along the aorta to the rest of the body.
What is oxygenated and deoxygenated blood?
- High in oxygen concentration and low in carbon dioxide concentration.
- Low in oxygen concentration and high in carbon dioxide concentration.
Why is it an advantage for the human heart to have two separate pumps?
- The right hand side generates pressure to send blood through the lungs where pressure drops.
- When it is returned to the left side of the heart, it generates more pressure so the blood can travel around the body at a fast enough rate to generate a high metabolic rate.
What do coronary arteries do?
Deliver oxygenated blood to the cardiac muscle that makes up the walls of the heart.
Why does the cardiac muscle need a rich supply of blood?
It needs a good supply of oxygen and glucose for a hugh rate of aerobic respiration to produce lots of ATP for heart muscle contraction.
Explain the structure of the heart.
- Atria are thin wall add and receive blood from the veins.
- Blood from the vena cava flows into the right atrium while blood from the pulmonary veins flows into the left atrium.
- Atria contract and blood passes through atrioventricular valves into the thicker walled ventricles.
- Ventricles contract and blood passes up through the the open semi-lunar valves.
- Right ventricle: blood passes into the pulmonary artery and then onto the lungs.
- Left ventricle: blood passes into aorta and from there to the rest of the body.
What is the description and role of the septum?
The two chambers on the left side of the heart are completely separated from those on the right side by a wall of muscle called the septum.
What is the description and role of atrioventricular valves?
- Prevent back flow of blood when they close.
- Atrioventricular valves prevent back flow from ventricles to atria.
What is the description and role of semi-lunar valves?
- Prevent backflow of blood when they close.
- Semi-lunar valves prevent back flow from arteries to ventricles.
What is the description and role of tendinous cords?
- Inelastic connective tissue attached to the atrioventricular valves.
- Prevent the valves from inverting.
Why are the walls of the left ventricle thicker than those of the right?
They have thicker muscle so contract with greater force creating enough pressure to pump blood into the aorta and around the body.
What is the cardiac cycle?
• Diastole:
- The heart muscle relaxes.
• Atrial systole:
- Blood fills the atria from the vena cava and pulmonary vein.
- The atrial muscle contracts, increasing the pressure above that of the ventricles.
- This forces the atrioventricular valves to open and blood flows into the ventricles.
• Ventricular systole:
- The ventricle muscles contract.
- The volume of the ventricle decreases, increasing the pressure.
- This causes the atrioventricular valves to close as pressure is greater in ventricles than atria.
- The blood is pushed upwards, towards the arteries at the top of the heart.
- The semi-lunar valves have an en and blood flows into the aorta and pulmonary artery as pressure is greater in ventricles than arteries.
How is the cardiac cycle controlled?
- A wave of electrical impulses is sent out from the sinoatrial node.
- It spreads across both atria, causing them to contract.
- The impulses reach the atrioventricular node where it is delayed.
- This delay allows the atria to fully empty, and the ventricles to fill with blood before the ventricles contract.
- The impulses are then transmitted down to the ventricles by the Bundle of His. This contains specialised conducting tissue called purkyne fibres.
- The impulses spread up the ventricle wall from the base via purkyne fibres, causing the ventricles to contract from the base up.
- Blood is forced up into the arteries.
What is the equation for cardiac output?
Cardiac output (dm^3 min^-1) = Stroke volume (cm^3) X Heart rate (bpm)
What is the advantage of increasing cardiac output during exercise?
- Allows more glucose and oxygen to be delivered to working muscles.
- Allows a higher rate of aerobic respiration and more ATP produced.
What is the structure of the arteries?
- The wall is thick to withstand the high pressure of blood.
- The thick middle coat contains many elastic fibres.
- Allowing them to stretch during systole and recoil during diastole to maintain blood pressure and smoothes pressure.
- The lumen is relatively small.
What is the structure of arterioles?
- Lots of muscle tissue.
- Thinner than arteries.
- Have an inner coat of a single layer of endothelium - reduces friction.
- The muscle can contract, narrowing the diameter of the lumen (vasoconstriction).
- The muscle can relax, to widen the lumen diameter (vasodilation).
What is the structure of the veins?
- Three layers, but the middle coat contains far fewer elastic or muscle fibres than arteries.
- Walls are very thin.
- Have valves.
- Lumen is relatively large.
What is the structure of the capillaries?
- Rate of blood flow is reduced allowing more time for diffusion/exchange.
- Single layer of squamous endothelial cells, providing a short diffusion pathway.
- Tiny pores between the cells in the wall - so highly permeable.
- Small size and large number in total provides a large surface area to volume ratio.
What does blood plasma transport?
- Carbon dioxide from the organs to the lungs.
- Soluble products of digestion from the small intestine to other organs.
- Urea from the liver to the kidneys.
What are the adaptations of red blood cells?
- Very small so there is a short diffusion pathway and had large surface area to volume ratio.
- It has a biconcave disc that increases the surface area to volume ratio. The ‘dent’ also provides a shorter diffusion.
- No organelles so it can carry more haemoglobin.
How is tissue fluid formed and returned?
- At the arteriole end of the capillary, there is high hydrostatic pressure due to the contraction of the left ventricle.
- Water, ions and small molecules are forced out of the blood into the spaces between the cells. This is now tissue fluid.
- Loss of fluid from the blood leads to a fall in hydrostatic blood pressure.
- Soluble plasma proteins remain in the blood so some of the water re-enters the capillary by osmosis down a water potential gradient.
- Excess tissue fluid is drained away from the cells by lymph vessels and returned to the circulation near the heart.
