Transport in mammals

Alevel AS 生物第八章知识结构图。内容包括：血红蛋白，氧转运问题，哺乳动物心血管系统，血管，血浆和组织液，淋巴等等。

Transport in mammals

• Transport systems in animals
• The mammalian cardiovascular system
  • 
    • It is made up of the heart and the blood vessels; a closed blood system; the blood travels twice through the heart on one complete‘circuit’
    • the systemic circulation: From the left ventricle into the aorta to the right side of the heart in the vena cava; through all parts of the body except the lungs
    • the pulmonary circulation:From the right ventricle into the pulmonary arteries to the left side of the heart;through the lungs
• Blood vessels
  • Arteries
    • Structure:3 layers(tunica intima;tunica media; tunica externa )
    • Function: to transport blood, swiftly and at high pressure, to the tissues
    • arterioles- control the volume of blood flowing into a tissue at different times
  • Capillaries
    • Structure:the walls are made up of a single layer of endothelial cells
    • Function: take blood as close as possible to all cells, allowing rapid transfer of substances between cells and blood
  • Veins
    • Structure: the same 3 layers as arteries, but the tunica media is much thinner and has far fewer elastic fibres and muscle fibres
    • Function:to return blood to the heart
• Blood plasma and tissue fluid
  • plasma: a pale yellow liquid include nutrients, waste products, protein molecules
  • tissue fluid: 1/6 of your body consists of spaces between your cells, in which are filled with leaked plasma; far fewer protein molecules than blood plasma
  • homeostasis:the maintenance of a constant internal environment
    • 
• Lymph
  • lymph vessels or lymphatics: tiny, blind-ending vessels, which are found in almost all tissues of the body;contain tiny valves
    • The valves allow large protein molecules to pass through
    • the movement of fluid along the lymphatics: the contraction of muscles around the vessels, and kept going in the right direction by valves
  • lymph:The fluid inside lymphatic; it is different in composition in a different place
    • in the liver: particularly high concentrations of protein
    • After a meal in the walls of the small intestine:high concentrations of lipids
  • lymph nodes
    • protection against disease
    • At intervals along lymph vessels
    • Bacteria and other unwanted particles are removed from lymph by some types of white blood cells as the lymph passes through a node, while other white blood cells within the nodes secrete antibodies
      • 
• Blood
  • Erythrocytes/Red blood cells
    • First:in the liver while still a fetus inside the uterus;Later:the bone marrow
    • pigment haemoglobin ;not live long(120d); membranes become more and more fragile
    • Structure:1.shaped like a biconcave disc- a large surface area, oxygen can diffuse quickly into or out of the cell;2. very small- 7 μm, bringing oxygen as close as possible to cells ;3. very flexible - a specialised cytoskeleton ause the cells have a specialised cytoskeleton, made up of a mesh-like network of protein fibres; 4.no nucleus, no mitochondria and no endoplasmic reticulum- more room for haemoglobin, maximising the amount of oxygen which can be carried
  • Leucocytes/White blood cells
    • bone marrow
    • fighting disease;group1-Phagocytes( destroy invading microorganisms by phagocytosis，eg. Monocytes ）;group2-Lymphocytes(secrete antibodies to destroy microorganisms)( smaller than most phagocytes; a large round nucleus ;a small amount of cytoplasm)
    • Structure:1. have a nucleus, although the shape of this varies in different types of white cell;2. larger than red blood cells except lymphocytes;3. either spherical or irregular in shape
• Control of heart beat
  • 
    • sinoatrial node/ SAN/pacemaker
    • atrioventricular node/AVN
    • Purkyne tissue
  • Electrocardiograms (ECGs)
    • 
      • P: the wave of excitation sweeping over the atrial walls
      • Q, R and S: the wave of excitation in the ventricle walls
      • T: the recovery of the ventricle walls
• The cardiac cycle
  • 
    • 
  • heart beats around 70 times a minute. The cardiac cycle is the sequence of events which makes up one heart beat.
• The heart
  • 
  • a bag made of cardiac muscle and filled with blood
  • atrioventricular valves:The atria and ventricles have valves between them; left:the mitral/bicuspid valve;the right: the tricuspid valve.
• Problems with oxygen transport
  • Carbon monoxide
    • Haemoglobin combines very readily, and almost irreversibly, with carbon monoxide
    • 250 times more readily than it does with oxygen;carboxyhaemoglobin is a very stable compound
    • Treatment : administration of a mixture of pure oxygen( favour the combination of haemoglobin with oxygen ) and carbon dioxide(stimulate an increase in the breathing rate)
  • High altitude
    • altitude sickness
      • from sea level to a very high altitude, the body does not have enough time to adjust to this drop in oxygen availability
    • As the body gradually acclimatises to high altitude
      • the number of red blood cells increases (pro 40-50%,now 50-70%)
    • live permanently
      • larger lung capacities ;The heart is larger(especially the right side) ; more haemoglobin
• Haemoglobin
  • transport oxygen from the gas exchange surfaces of the alveoli in the lungs to tissues all over the body
  • made up of four polypeptides; each containing one haem group;.Each haem group can combine with one oxygen molecule (HbO8 oxyhaemoglobin)
  • The haemoglobin dissociation curve
    • 
      • The S-shaped curve
      • When an oxygen molecule combines with one haem group, the whole haemoglobin molecule is slightly distorted
  • 
    • The Bohr shift
    • the amount of oxygen the haemoglobin carries is affected not only by the partial pressure of oxygen, but also by the partial pressure of carbon dioxide
    • 
      • By removing the hydrogen ions from solution, haemoglobin helps to maintain the pH of the blood close to neutral. It is acting as a buffer.
      • the Bohr effect：The presence of a high partial pressure of carbon dioxide causes haemoglobin to release oxygen
  • Carbon dioxide transport
    • 
      • When blood reaches the lungs, the reactions described above go into reverse
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• 1. describe the structure of the mammalian circulatory system 2. relate the structures of arteries, veins and capillaries to their functions 3. describe and explain the structure and functions of blood, including oxygen transport 4. describe and explain the formation of tissue fluid and lymph 5. explain the structure and function of the heart 6.describe the cardiac cycle and its control