Heart and Blood vessels 6a

• What type of muscles is the heart made from?

  Cardiac muscle
• Diagram of heart

  
• Why do mammals have a double circulatory system?

  Blood passes through the heart twice

  on one complete circulation of the body.

  • The pulmonary circulation pumps blood to the lungs to be oxygenated.

  • The systemic circulation pumps oxygenated blood to every other part of the

  body that uses oxygen.
• The right side of the heart receives deoxygenated blood from the body, which it then sends to the lungs via the pulmonary artery. In the lungs, carbon dioxide diffuses out of the blood into the air sacs (alveoli) and oxygen diffuses into the blood. Oxygen-rich blood returns to the left atrium of the heart via the pulmonary vein.
• What are the valves between the atria and ventricles called?

  The right atrio ventricular valve or the tricuspid valve .

  the left atrio ventricular valve or the bicuspid valve
• Where is the semi lunar valve located?

  where the heart connects with both the aorta and the pulmonary artery
• Why are the atrioventricular valves important?

  To prevent back flow of blood in opposite direction
• What happens in diastole?

  Relaxation of the heart chambers and filling with blood. As the atria fill with blood, the pressure increase. There is a higher pressure in the atria than the ventricles so blood is forced through the AV valves into the ventricles. Semi lunar valve is closed
• Describe atrial systole?

  Contraction of the atria, forcing blood into ventricles. Semi lunar valves closed, av valves open
• Describe ventricular systole?

  Contraction of the ventricles. blood pumped into pulmonary arteries and the aorta. Semi lunar valves open. AV valves close, ventricles contract. After a short delay ( to allow ventricles to fill with blood) they contract. Pressure higher in ventricles than atria so Av valves close
• Why is the left side of the heart a thicker muscular wall?

  Must force blood over a larger distance
• How to calculate cardiac output?

  Cardiac output = stroke volume ( dm3) x heart beat (bpm)
• How is the cardiac cycle controlled?

  Sinoatrial node in right atrium sends impulses to atrioventricular node. There is a delay to allow atria to fill with blood. The bundle of His is a collection of conducting tissue that transmits the electrical activity to the apex (bottom) of the heart and around the ventricle walls along fibres called the Purkyne fibres. As the waves of electrical activity pass along the Purkyne fibres, the ventricles contract together. Blood is forced out of the ventricles and out of the heart.
• What does myogenic mean?

  Contractions originating from within the muscle itself.
• describe the arteries

  • Arteries transport blood away from the heart to the organs.
  • Artery walls have thick layers of muscle.
  • The walls maintain a high pressure so blood can be pumped around the body.
  • Elastic fibres in the artery wall allow the arteries to stretch.
  • The endothelium is folded which also allows the arteries to stretch.
  • no valves except in pulmonary artery
• the arterioles :

  • When arteries reach an organ, they split into many smaller vessels called arterioles.
  • The direction of blood flow can be controlled by contracting the arterioles to restrict blood flow and relaxing the arterioles to allow blood to flow.
  • pressure lower than artery but higher than vein.
  • no valves present
• • Veins transport blood back to the heart.
  • The lumen of veins is wider than the arteries which allows the blood to flow at low pressure.
  • There is a thin muscle wall and elastic tissue in the vein walls.
  • Valves are located throughout the veins to ensure blood flows towards the heart.
  • thickness is small which allows veins to be flattened/compressed thereby aiding blood flow.
• Venules:

  • Connect capillary bed to veins.
• Capillaries:

  • Microscopic blood vessels that link arterioles and venules. 
  • Just large enough for 1 red blood cell to pass through.
  • Fenestrations (gaps) in endothelium allow substances dissolved in blood plasma to move in and out.
  • Gaseous exchange between oxygenated blood and respiring tissues occurs in capillaries.
  • Adapted to their role because...
  • They have a large SA:V ratio for diffusion.
  • They are only 1 cell thick so there is a small diffusion distance.
  • Total area of capillary bed > total area of arterioles, so pressure drops causing blood to move slower to allow more time for diffusion.
• artery

  
• veins

  
• which vessel carries oxygenated blood to the kidneys?

  Renal artery
• which vessel carries deoxygenated blood away from kidneys?

  Renal Vein
• which is the vein with oxygenated blood

  pulmonary vein
• the artery with deoxygenated blood?

  Pulmonary artery
• arteries and veins are organs as they are a collection of different tissues which work together to achieve a particular function - to carry blood
• why are there spaces between endothelial cells (pores) in capillaries?

  allow white blood cells to enter into tissues to deal with infection
• why is there low blood pressure in capillaries?

  allows exchange of o2 and co2 and glucose. blood flows slower and so more time for exchange of material
• function of elastic tissue in arteries?

  Maintaining blood pressure and allowing for expansion and recoil. when ventricles contract and force blood into arteries, they bulge, stretching the elastic tissue. recoil of the elastic tissue smoothes out the blood flow and forces it along the arteries when heart relaxes
• function of muscle tissue?

  contracts and relaxes- vasoconstriction (contracts) or relax (vasorelaxtion) and control the flow of blood to different tissues in the body.
• tough outer layer- contains collagen fibres that allow expansion of the artery and its function is to be resistant to pressure changes from within and outside the artery.
• what happens in coronary heart disease?

  layers of fatty material (atheroma) build up inside walls of the coronary arteries that supply the heart muscle with blood. this narrows them and reduces flow of blood through them. can lead to thrombosis i.e. blood clot. blocks artery completely causing a myocardial infarction (heart attack).
• Unavoidable risk factors with CHD

  advancing age

  ethnicity

  male gender
• how does smoking cause CHD?

  Nicotine: increases heart rate and also acts as a vasoconstrictor, narrowing artery lumen and so increasing blood pressure

  increases risk of developing atheroma and thrombosis
• diet

  high blood cholesterol: eating lots of saturated fat or cholesterol can lead to high levels of LDL cholesterol in blood which in turn leads to atheroma. to increase HDL cholesterol, eat more unsaturated fats and fewer saturated. high levels of salt raise blood pressure
• high blood pressure

  prolonged stress, certain diets and lack of exercise increase risk of high blood pressure. higher blood pressure damages artery endothelium so begins atheroma formation. also increases risk of thrombosis