Respiratory system

• Mitochondria - supply the cells with energy for metabolism and functions such as muscle contraction and nerve impulse conduction
• Mitochondria - Site of respiration
• The mitochondrion has an inner and an outer membrane

  The inner membranes form the cristae

  Mitochondria have their own DNA
• The pharynx opens into two tubes:  

  Oesophagus (food pipe)

  Trachea (wind pipe)
• The Epiglottis is an important structure to ensure food does not enter the trachea
• Trachea

  Lined with ciliated epithelium

  Cilia move in waves towards the pharynx

  Secrete thick mucus

  Trap dust and move it to the oesophagus
• Macrophages

  Macrophages in the lung trap particulate matter by phagocytosis

  Macrophages migrate up the trachea and deposit material into oesophagus
• Alvioli

  Tiny ‘air sacs’ packed in the lungs

  Site of gaseous exchange in lungs – oxygen + carbon dioxide

  Extremely specialised
• During inspiration high volume and low pressure forces air to move in. volume of thorax increases
• in expiration the size of the thorax decreases and the the pressure increases forcing air out
• Inspiration

  Diaphragm contracts and chest wall moves out

  Expands volume of chest cavity

  Reduces fluid pressure in the pleural cavity

  Reduces pressure in alveoli below atmospheric pressure

  Air enters lung
• Expiration

  Muscles relax

  Diaphragm returns to resting position

  Chest wall returns to resting position

  Increases pressure in pleural cavity

  Increases pressure in alveoli

  Air is expired
• expiratory reserve - most breath out

  Tidal volume - amount of air in and out in a normal respiratory cycle (500ml)

  Inspiratory reserve - Inspiration forced (2500 - 3000 ml)
• Gas exchange

  Oxygen diffuses across the membranes of the lung into the blood plasma and is carried around the body

  Relies on a rich blood supply to ensure efficient diffusion
• O2 in the blood

  About 10% dissolves in the blood plasma2 and CO2

  Remainder (90%) becomes absorbed into the red blood cells

  Effects of hyperventilation (too much O2 that is not needed) and hypoventilation (pressure gradient too steep) on arterial pressure of O2 and CO2
• Erythrocytes

  Only 10% will dissolve in  the plasma

  Most oxygen binds to haemoglobin a major constituent of red blood cells

  Blood contains about 5 million red cells per ml

  30% of cell weight is haemoglobin

  ‘Biconcave disc’
• higher O2 pressure and saturation higher affinity to heamoglobin and more likely to bind
• High pH higher affinity of heamoglobin for O2 and easier to attain a higher saturation as there is a higher pH
• Haemoglobin has less affinity for oxygen at low pH

  Less acid in the lung encourages binding of oxygen to haemoglobin

  More acid in capillaries encouraging release of oxygen from haemoglobin to the tissues
• CO2 has less affinity for haemoglobin, therefore cannot fully be carried by RBCs as ‘CO2’. However, CO2 needs to somehow be in the plasma to be removed by the lungs. CO2 combines with water to form carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions. CO2 + H2O  → H2CO3 →  HCO3- + H2. It is in the form of bicarbonate ions that CO2  is mostly carried by the blood to the lungs
• removal of CO2 from cells

  A) carbaminoheamoglobin

  B) 67%

  C) cell

  D) plasma

  E) red blood cells

  
• diffusion of CO2 into lungs

  A) alvioli

  B) lower CO2 pressure

  C) higher CO2 pressure

  D) plasma

  E) tred blood cells