Mass transport in animals

• Tuberculosis (TB) 


  results in the formation of small lumps in the lungs called ‘tubercles’

  This damages the gas exchange surface so tidal volume is reduced

  This leads to coughing up blood, chest pain, shortness of breath, and fatigue
• • Ciliated epithelium is a specialised tissue found along the trachea down to the bronchi. Each cell has small projections of cilia which sweep mucus, dust and bacteria upwards and away from the lungs and the epithelium itself is covered in mucus.
• 
  

  Goblet cells can be found scattered throughout the ciliated epithelium in the trachea

  They are mucus - producing cells that secrete viscous mucus which traps dust, bacteria and other microorganisms and prevents them from reaching the lungs

  The mucus is then swept along by the cilia of the ciliated epithelium upwards and is swallowed

  The mucus and any microorganisms will then be destroyed by the acid in the stomach
• Smooth muscle can be found throughout the walls of the bronchi and bronchioles

  It helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when less air is needed
• squamous epithelium


  • The alveoli have a lining of thin and squamous epithelium, that allows for gas exchange
  • The squamous epithelium forms the structure of the alveolar wall and so is very thin and permeable for the easy diffusion of gases
• cartilage


  • Cartilage is a strong and flexible tissue found in various places around the body
  • One place is in rings along the trachea, called Tracheal rings
  • These rings help to support the trachea and ensure it stays open, while allowing it to move and flex while we breathe
• arteries

  have a thick muscular layer that contracts and relaxes to control blood flow

  have a thick elastic layer that stretches and recoils to maintain high blood pressure

  and the arteries have a thick arterial wall to prevent bursting from high pressure
• arterioles

  have a thicker muscular layer than arteries which contracts to reduce blood flow in capillaries

  have a thin elastic layer as they do not need to withstand high blood pressure
• veins

  have a thin muscle layer as blood flow does not need to be controlled

  have a thin elastic layer as low blood pressure is needed

  veinal walls are thin

  veins contain valves to prevent the backflow of blood
• capillaries

  only consist of lining layer and lumen

  the thin lining layer and narrow lumen provide a short diffusion pathway

  capillaries exist as numerous and highly branched providing a large surface area
• Tissue Fluid

  Tissue fluid is formed from blood plasma, the fluid that moves out of capillaries

  Tissue fluid is the fluid by which substances are exchanged between the blood and cells

  Made up of substances which are small enough to escape through gaps in the capillaries wall
• blood moving into the capillaries has a high hydrostatic pressure ( pressure exerted by a fluid )

  high hydrostatic pressure forces water and dissolved substances out of the capillaries forming tissue fluid
• • Tissue fluid bathes almost all the cells of the body that are outside the circulatory system
  • Exchange of substances between cells and the blood occurs via the tissue fluid
  • For example, carbon dioxide produced in aerobic respiration will leave a cell, dissolve into the tissue fluid surrounding it, and then move into the capillary
• Oncotic pressure

  This is the osmotic pressure exerted by plasma proteins within a blood vessel

  when there is movement of fluid out of the capillaries (due to hydrostatic pressure), the water potential of the capillaries becomes more negative (though this is usually stable).
• Blood vessels generally contain a muscle layer. What is its function?

  The function of the muscle layer is to contract to control the flow of 

  blood
• Blood vessels generally contain an elastic layer. What is its function?

  The function of the elastic layer is to recoil and stretch to maintain blood pressure
• How is the artery wall adapted to its function?

  the wall is thick to prevent the artery from bursting under high pressure
• Describe how tissue fluid is formed

  Blood moving into the capillaries has a high hydrostatic pressure.

   

  This pushes blood plasma, which is made up of water and other dissolved substances, out of the capillaries. The result is tissue fluid.
• Describe how tissue fluid returns to the capillaries

  At the venous end of the capillaries the loss of fluid, combined with the remaining plasma proteins, reduces the water potential and hydrostatic pressure.

   

  This allows tissue fluid to return to the blood as a result of osmosis and external hydrostatic pressure

   
• Explain how haemoglobin shows different affinities for oxygen in different species

  Haemoglobin in different species has different amino acid sequence/primary structure

  This affects their tertiary and quarternary structures

  This affects their oxygen binding affinities as the shapes of haemoglobin are different
• Why does the oxygen dissociation curve for haemoglobin have a sigmoid (S-shaped) shape?​

  cooperative binding makes it easier for additional oxygen to bind after the first oxygen molecule​
• What causes the oxygen dissociation curve to shift to the right?​

  Increased carbon dioxide concentration, increased temperature, and decreased pH
• What is the correct order of structures that blood passes through on the right side of the heart?

  right atrium, atrioventricular valve, right ventricle, semi-lunar valve
• Blood returns to the heart from the lungs via the pulmonary vein

  it enters the left atrium then passes into the left ventricle through the atrioventicular valve

  blood the passes through the semi-lunar valve before exiting the heart through the aorta
• What are the vessels that supply the heart with blood called?

  coronary arteries
• Explain how a myocardial infarction occurs

  A myocardial infarction occurs when blood flow in the coronary arteries reduces

   

  This means the amount of oxygen reaching the heart muscle also reduces

   

  As a result, the heart cells respire less and start to die
• What happens in the cardiac cycle?

  first, blood enters the atria

  Then, the atrium contract

  Finally, the ventricles contract
• What happens during diastole in the cardiac cycle?

  Atria and ventricles are relaxed
• What causes the atrioventricular valves to open?

  Pressure in atria is greater than in ventricles
• What occurs after the atrioventricular valves open?

  Blood starts entering the ventricles
• What happens during atrial systole?

  Atria contract and pressure increases
• What is the effect of atrial contraction on blood flow?

  It pushes blood into the ventricles
• What occurs during ventricular systole?

  Ventricles fill with blood
• When do the atrioventricular valves close?

  When pressure in ventricles is greater than in atria
• What happens when the ventricles contract?

  Volume decreases and pressure increases
• What causes the semi-lunar valves to open?

  Pressure in ventricles is greater than in blood vessels
• What happens when the semi-lunar valves open?

  Blood is pushed out of the heart
• When do the semi-lunar valves close?

  When pressure in blood vessels is greater than in ventricles
• What are the key phases of the cardiac cycle related to valve function?

  • Diastole: Atria and ventricles relaxed
  • Atrial systole: Atria contract, pressure increases
  • Ventricular systole: Ventricles contract, pressure increases
  • Valve opening and closing based on pressure differences
• The semi-lunar valves open when the pressure in the ventricles is greater than the pressure in the blood vessels