cardiovascular system

• the cardiovascular system consists of the heart, which pumps blood around the body through an associated system of blood vessels
• there are three main types of blood vessels which carry blood around the body:

  • arteries- carry blood away from the heart
  • veins- bring blood back to heart
  • capillaries- connects arteries to veins
• label the blood vessels:

  A) deoxygenated blood

  B) oxygenated blood

  C) artery

  D) capillaries

  E) vein

  
• blood pressure decreases as it moves away from the heart and so blood pumped out of the heart in arteries is at higher pressure than blood returning to the heart in the veins
• each blood vessel has a central channel through which the blood travels, which is known as the lumen
• surrounding the central lumen is an endothelium lining which is surrounded by layers of tissue
• the composition of the tissues surrounding this endothelium differs between the different types of blood vessels
• arteries have:

  • a central lumen through blood flows
  • single layer of endothelium cells which line lumen- minimises friction between the blood and walls of the vessel
  • middle layer of smooth muscle and elastic fibres
  • outer layer of connective tissue and elastic fibres
• elastic walls of the arteries stretch and recoil to accommodate the surge of blood after each contraction of the heart
• the smooth muscle of the arteries can contract or relax to cause vasoconstriction narrowing the lumen which decreases blood flow, or vasodilation widening the lumen which increases blood flow, allowing blood flow to be controlled
• label the contraction and relaxation of the heart:

  A) vasodilation

  B) vasoconstriction

  
• veins are similar in structure to arteries
• veins have:

  • central lumen (wider than artery)
  • endometrium lining
  • thinner muscular wall than arteries
  • outer layer of connective tissue containing elastic fibres
  • valves- prevent backflow of blood, could occur when die to low blood pressure in veins
• label the artery and vein similarities:

  A) artery

  B) vein

  C) connective tissues and elastic fibres

  D) lumen

  E) lumen

  F) muscular tissue

  G) endothelium

  
• label the similarities between the artery and vein:

  A) artery

  B) vein

  C) endothelium

  D) valves

  E) muscular tissue

  F) connective tissues and elastic fibres

  
• capillaries are the smallest of the blood vessels and form connections between the arteries and veins
• due to capillaries length they have a very large surface area to allow them to be more efficient at their function of exchanging substances (oxygen, glucose, etc) between the blood and surrounding body cells
• capillaries have only a single layer of endothelial cells lining their lumen and do not possess any muscular or connective tissue
• the tiny gaps between the endothelial cells allow the walls of capillaries to be permeable
• label the capillary:

  A) endothelium

  B) lumen

  
• blood pressure and flow rate are both low within the capillaries, however, they are still higher than the surrounding fluid and tissues
• the higher pressure in the capillaries forces some plasma (liquid part of blood) out through the capillary walls into the surrounding cells
• carbon dioxide and other metabolic waste products diffuse into surrounding cells and into the tissue fluid to be excreted; much of this tissue fluid will return to the blood
• blood plasma is very similar in composition to tissue fluid with the exception of protein content; tissue fluid does not contain plasma proteins as they are too large to pass through capillary walls
• the lymphatic system which is composed of lymphatic vessels carrying a liquid known as lymph, will absorb excess tissue fluid and return the lymph fluid to the circulatory system
• the term cardiac refers to the heart
• the heart is a muscular pump consisting of 4 chambers through which blood flows
• the left and right side of the heart are completely separated from each other by a central wall
• the right side of the heart receives deoxygenated blood from the body in the vena cava and pumps this to the lungs in the pulmonary artery; this is then oxygenated in the lungs to the rest of the body through the aorta
• the two upper chambers of the heart are known as the atria and the lower chambers of the heart are known as the ventricles
• between the atria and ventricles are the atrioventricular valves, which prevent the backflow of blood from the ventricles back to the atria
• the two arteries which leave the heart- the pulmonary artery and the aorta- possess semi-lunar valves which prevent backflow of blood into the ventricles
• label the heart:

  A) vena cava

  B) pulmonary artery

  C) pulmonary vein

  D) right atrium

  E) right ventricle

  F) vena cava

  G) aorta

  H) pulmonary artery

  I) pulmonary vein

  J) left atrium

  K) left ventricle

  L) central wall (septum)

  
• label the valves

  A) semi-lunar valves

  B) atrioventricular valves

  
• the coronary arteries, which are visible on the exterior of the heart, supply the heart itself with oxygenated blood
• the left and right ventricles pump the same volume of blood through the aorta and the pulmonary artery
• cardiac output is the volume of blood pumped through each ventricle per minute (ml blood/min)
• cardiac output can be determined from the heart rate and stroke volume using the calculation:

  cardiac output= heart rate (bpm) x stroke volume (ml/beat)
• heart rate is simply the number of heart beats per minute
• stroke volume is the volume of blood, in millilitres (ml), pumped out of the heart with each beat