Larynx Trachea Bronchus Bronchiole Lung Lobes - 3 on Right & 2 on Left Diaphragm Thoracic Cavity – Chamber of chest protected by the thoracic wall. Separated from abdominal cavity but diaphragm Alveoli Pleural Membrane
Visceral Pleura The visceral pleura is the innermost of the two pleural membranes. It covers the surface of the lung and dips into the spaces between the lobes
Pleural Fluid The pleural membrane produce pleural fluid which fills the space between them. This acts a lubricant to allow to glide over the thoracic wall during respiration Whilst membranes slide easily over each other, their separation is resisted by the surface tension of the pleural fluid that keeps the lung surface in contact with the chest wall
Gaseous Exchange This happens by a process called DIFFUSION. DIFFUSION is the name given to the process of exchanging gases in the tissues in the body Diffusion Is When – Air comes into the body Oxygen separated out and passed around the body. Carbon dioxide removed and expelled. This happens every time you breathe.
The blood in these capillaries passes its carbon dioxide into the capillaries before taking in oxygen from the alveoli. Alveoli ---------oxygen-----------capillaries Whilst the oxygen is taken in, carbon dioxide is given out into the alveoli and breathed out.
Mechanisms of Breathing Breathing is when air transported in and out of the lungs, and can be split into two phases Inspiration & Expiration
Inspiration Within inspiration the intercostals muscle contract to lift the ribs upwards and outwards, while the diaphragm is forced downwards and the sternum forwards This expansion of the thorax in all directions causes a drop in pressure which encourages air to flood into the lungs. At this point oxygen is exchanged for carbon dioxide through the capillary walls
Expiration Expiration follows inspiration as the intercostals muscles relax, the diaphragm extends upwards and the ribs and sternum collapse At that point, pressure within the lungs is increased and air is expelled. When the body is in action, greater amounts of oxygen are required, meaning the intercostal muscles and diaphragm need to work harder
Lung Volumes Respiratory Rate – Amount you can breathe in in one minute Equal to approx 12 BPM = 6 Litres of air passes through lungs During exercise = 30 – 40 BPM Other measurements include, Tidal Volume, Inspiratory & Expiratory Reserve Volume, Vital Capacity, residual Volume, Total Lung Capacity, Chemical Control
Tidal Volume Tidal volume is the lung volume representing the normal volume of air displaced between normal inspiration and expiration when extra effort is not applied. Typical values are around 500ml or 7ml/kg bodyweight
Mechanisms of Breathing The volume of air which you normally breathe in and out is called the tidal volume. This is normally about 500 cm 3 when you are at rest However if you breathe in as much as you can you can breathe in more than 500 cm 3. The extra volume of air breathed in (inspiration) is called the inspiratory reserve volume Similarly when you breathe out as much as you can, the extra volume of air breathed out (expiration) is called the expiratory reserve volume These three volumes added together give you your vital capacity: the maximum volume of air you can breathe in or out When you have breathed out as much as you can there is still some air left in your lungs i.e. you cannot empty your lungs completely. This volume is called the residual volume The vital capacity plus the residual volume equals your total lung capacity
Vital Capacity Vital Capacity is the amount of air that can be forced out of the lungs after maximal inspiration. The volume is around 4,800cm3
Residual Volume The amount of air remaining in the lung at the end of a maximal exhalation
Control of Breathing – Neural & Chemical Control Breathing rate is primarily regulated by neural and chemical mechanisms. Respiration is controlled by spontaneous neural discharge from the brain to nerves that innervate respiratory muscles. The primary respiratory muscle is the diaphragm, which is innervated by the phrenic nerve. The rate at which the nerves discharge is influenced by the concentration of oxygen, carbon dioxide and the acidity of the blood Chemical Control There are chemoreceptors in the brain and the heart that sense the amount of oxygen, carbon dioxide and acid present in the body. As a result, they modulate the respiratory rate to properly compensate for any disruptions in balance of any of these chemicals. Too much carbon dioxide or acidity and too little oxygen cause the respiratory rate to increase and vice versa. Carbon dioxide chemoreceptors are much more sensitive than oxygen chemoreceptors and, thus, exert an effect with smaller changes. Neural Control There are two neural mechanisms that govern respiration -- one for voluntary breathing and one for automatic breathing. The voluntary impulse originates in the cerebral cortex region of the brain and the automatic impulse originates in the medulla oblongata.