A+P - respiratory system

• C1.

  The respiratory system provides oxygen to all living tissues in the body in order for them to function, as well as removing waste products such as carbon dioxide, heat and water vapour​.
• C1.

  Central to the respiratory system are your lungs, which enable oxygen to enter the body and carbon dioxide waste to be removed through the mechanism of breathing​.
• C1.

  Your body’s ability to inhale and transport oxygen while removing waste products is critical to sports performance. ​The better your body is at this process, the better you will be able to train or perform in sport.
• C1.

  Air is drawn into the mouth and nose and passes through a series of airways to reach the lungs​. This series of airways is referred to as the respiratory tract and can be divided into two main parts; upper and lower​:

  Upper: nose, nasal cavity, mouth, pharynx, larynx.

  Lower: trachea, bronchi, bronchioles, alveoli, lungs.
• C1.

  Nasal Cavity.

  • Air enters the nasal cavity by passing through the nostrils​.
  • Hairs within the cavity filter out dust, pollen and any other foreign bodies​.
  • The air is warmed and moistened before it passes through the nasopharynx​.
  • A sticky mucous layer traps smaller foreign particles, with tiny hairs called cilia, which transport to the pharynx to be swallowed​.
• C1.

  Pharynx.

  • AKA the throat​.
  • The wall of the pharynx contains muscle throughout its length​.
  • The funnel-shaped pharynx connects the nasal cavity and mouth to the larynx (air) and oesophagus (food)​.
  • It is this passage way for both food and air, so special adaptations are required to prevent choking when food or liquid is swallowed​.
• C1.

  Larynx​.

  • The larynx or voice box has rigid walls of muscle and cartilage, contains vocal cords and connects the pharynx to the trachea​.
  • It extends for about 5cm from the level of the third to sixth vertebrae​.
• C1.

  Trachea​.

  • Approximately 12cm long and 2cm in diameter​.
  • It contains rings of cartilage to prevent it from collapsing, and it is flexible​.
  • It travels down the neck in front of the oesophagus and branches into the right and left bronchi​.
• C1.

  Lungs.

  • The organ that allows oxygen to be drawn into the body​.
  • The paired left and right lungs occupy most of the thoracic cavity and extend down to the diaphragm​.
  • They hang suspended in the right and left pleural cavities straddling the heart​.
  • The left lung is smaller than the right​.
• C1.

  Bronchi​.

  • The bronchi branch off the trachea and carry air to the lungs​.
  • By the time it reaches here it is warm, clear of impurities and saturated with water vapour​.
  • Each bronchus subdivides into lobar bronchi; 3 on the right and 2 on the left- these continue to branch into smaller bronchi approximately 23 times- forming a bronchial tree​.
• C1.

  Bronchioles​.

  • Small airways that extend from the bronchi and connect the bronchi to small clusters of thin-walled air sacs, known as alveoli​.
  • They are about 1mm in diameter and are the first airway branches of the respiratory system that do not contain cartilage​.
• C1.

  Alveoli​.

  • 300 million gas-filled alveoli in each lung​.
  • These are responsible for the transfer of oxygen into the blood and the removal of carbon dioxide out of the blood- gaseous exchange​.
  • The alveoli are surrounded by a network of capillaries​.
• C1.

  Diaphragm.

  • The diaphragm is a flat muscle that is located beneath the lungs within the thoracic cavity and separates the chest from the abdomen​.
  • The diaphragm is one of the several components involved in breathing, which is the mechanism of drawing in air-including oxygen into the body (inhalation) and removing gases including carbon dioxide (exhalation)​.
  • Contraction of the diaphragm increases the volume of the chest cavity, drawing air into the lungs, while relaxation of the diaphragm decreases the volume of the chest cavity, pushing air out​.
• C1.

  Thoracic Cavity.

  • This is the chamber of the chest that is protected by the thoracic wall (ribs)​.
  • It is separated from the abdominal cavity by the diaphragm​.
• C1.

  Internal and External Intercostal Muscles.

  • The intercostal muscles lie between the ribs and they extend and contract to help with inhalation and exhalation​.
  • The internal intercostal muscles lie inside the rib cage. When they contract they draw the ribs downwards and inwards, decreasing the volume of the chest cavity and forcing air out of the lungs when breathing out​.
  • The external intercostal muscles lie outside the rib cage. When they contract they pull the ribs upwards and outwards, increasing the volume of the chest cavity and drawing air into the lungs when breathing in​.
• C2.

  • Breathing or pulmonary ventilation is the process by which air is transported into and out of the lungs, and it can be considered to have two phases​.
  • It requires the thorax to increase in size to allow air to be taken in (inspiration), followed by a decrease to allow air to be forced out (expiration).
• C2.

  Inspiration.

  • Breathing air into the lungs​.
  • The external intercostal muscles between the ribs contract to lift the ribs up and outwards, while the diaphragm moves downwards​.
  • This expands the thoracic cavity in all directions​.
  • This causes a drop in pressure within the lungs to below atmospheric pressure (the pressure of the air outside the body) which encourages air to be drawn into the lungs​.
• C2.

  Expiration.

  • Breathing air out of the lungs​.
  • Internal intercostal muscles contract, external intercostal muscles relax​.
  • The diaphragm relaxes, moving upwards and the ribs move downwards and inwards​.
  • Pressure within the lungs increases and air is expelled or pushed out of the body​.
• C2.

  • During sport or exercise, greater amounts of oxygen are required, so the intercostal muscles and diaphragm must work harder​.
  • This results in an increase in your breathing rate and an increase in the force of your breath​.
• C2.

  Gaseous Exchange.

  • Gaseous exchange is the process by which one type of gas is exchanged for another​.
  • In the lungs, gaseous exchange occurs by diffusion​.
  • Diffusion- the process by which a substance such as oxygen passes through a cell membrane either to get into the cell or out of the cell. Substances move by diffusion from an area where they are more concentrated to an area where they are less concentrated.
• C2.

  Gaseous Exchange.

  • In the lungs, gaseous exchange occurs by diffusion between the air in the alveoli and blood in the capillaries surrounding their walls.
  • It delivers oxygen from the lungs to the bloodstream and removes carbon dioxide from the bloodstream to the lungs.
• C2.

  Gaseous Exchange.

  • The alveolar and capillary walls form a respiratory membrane that has gas on one side and blood flowing past on the other​.
  • Gaseous exchange occurs readily by simple diffusion across the membrane​.
  • Blood entering the capillaries from the pulmonary arteries has a lower oxygen concentration and a higher carbon dioxide concentration than the air in the alveoli.
• C2.

  Gaseous Exchange.

  • Oxygen diffuses into the blood via the surface of the alveoli, through the thin walls of the capillaries, through the red blood cell membrane and finally latches onto the haemoglobin​.
  • Carbon dioxide diffuses in the opposite direction, from the blood plasma into the alveoli​.
• C2.

  Gaseous Exchange Cycle.

  • Breath in O2.
  • Transport O2 to lungs.
  • O2 enters bloodstream.
  • O2 enters muscle, CO2 is released.
  • CO2 enters bloodstream.
  • Transport CO2 to lungs.
  • Breathe out CO2.
  • Restart cycle.
• C3.

  Lung Volumes.

  • Your lungs are designed to take in more air during exercise so that more oxygen can reach the alveoli and more carbon dioxide can be removed​.
  • Your breathing will become deeper and more frequent to cope with the demands that exercise puts on your body​.
• C3.

  Lung Volumes - respiratory rate.

  • Your respiratory rate is the amount of air you breathe in, in one minute​.
  • For a typical 18 year old this represents about 12 breaths per minute at rest, during which time about 6-9 litres of air passes through your lungs, per minute (L/min)​.
  • It can increase significantly during exercise, by as much as 30-40 breaths per minute​.
• C3.

  Lung Volumes - tidal volume.

  • Tidal volume is the term used to describe the volume of air breathed in and out with each breath​.
  • Under normal conditions this represents about 500cm3 of air breathed, both inhaled and exhaled​.
  • Of this, approximately two-thirds (350cm3) reaches the alveoli in the lungs where gaseous exchange takes place​.
  • The remaining 150cm3 fills the pharynx, larynx, trachea, bronchi and bronchioles and is known as dead or stationary air​.
  • During exercise, tidal volume increases to allow more air to pass through the lungs​.
• C3.

  Lung Volumes - minute ventilation (VE).

  The volume of air passing through the lungs per minute is known as the minute ventilation (VE)​

  ​

  Breathing Rate x Tidal Volume = Minute Ventilation (VE)​

  ​

  (Number of breaths per minute x volume of each breath)​
• C3.

  Lung Volumes - residual volume.

  • The lungs normally contain about 350cm3 of fresh air, 150cm3 dead air and 2500cm3 of air that has already undergone gaseous exchange with the blood​.
  • The lungs are never fully emptied of air otherwise they would collapse​.
  • The air that remains in the lungs after maximal expiration is referred to as residual volume- approximately 1200cm3​.
• C3.

  Lung Volumes - vital capacity.

  • Vital Capacity is the amount of air that can be forced out of the lungs after maximal inspiration, the volume is around 4800cm3​
• C3.

  Lung Volumes - total lung volume/capacity.

  • Total lung volume is your total lung capacity after you have inhaled as deeply as you can, after maximal inspiration​.
  • It is normally around 6000cm3 for an average sized male​.
• C4.

  Control of breathing.

  • There are two ways in which we control our breathing:​

  1. Neural control​.
  2. Chemical control​.
• C4.

  Neural.

  • Breathing is a complex process that is largely under involuntary control by the respiratory centres of your brain​.
  • Inspiration is an active process, as the diaphragm muscle is actively contracting which causes air to enter the lungs​.
  • Expiration is a passive process, as the diaphragm relaxes to allow air to exit the lungs​.
  • This process is controlled by neurones (cells that conduct nerve impulses) in the brain stem​.
  • Neurones in two areas of the medulla oblongata are critical in respiration​.
• C4.

  Neural.

  • There are the dorsal respiratory group (DRG) and the ventral respiratory group (VRG)​.
  • The VRG is thought to be responsible for the rhythm generation that allows rhythmic and continuous breathing.
• C4.

  Chemical.

  • Other factors that control breathing are the continually changing levels of oxygen and carbon dioxide in the blood​.
  • Sensors responding to such chemical fluctuations are called chemoreceptors​.
  • These are found in the medulla and in the aortic arch and carotid arteries​.
  • These chemoreceptors detect changes in blood carbon dioxide levels as well as changes in blood acidity, and send signal to the medulla that will make changes to breathing rates​.
• C5.

  • Your body is surprisingly insensitive to falling levels of oxygen, yet it is sensitive to rising levels of carbon dioxide​.
  • The levels of oxygen in arterial blood varies very little, even during exercise, but carbon dioxide levels vary in direct proportion to the level of physical activity​.
• C5.

  • The more intense the exercise, the greater the carbon dioxide concentration in the blood.​
  • To combat this, your breathing rate increases to ensure the carbon dioxide can be expelled through expiration.​
• C5.

  Increased Breathing Rate.

  • Exercise results in an increase in the rate and depth of breathing​.
  • During exercise your muscles demand more oxygen, and the corresponding increase in carbon dioxide production stimulates faster and deeper breathing​.
  • The capillary network surrounding the alveoli expands, increasing blood flow to the lungs and pulmonary diffusion​.
• C5.

  Increased Breathing Rate.

  • Capillary network expands​.
  • Vessels get wider/bigger​.
  • Increased blood flow.
  • Increased gaseous exchange (oxygen-​Carbon dioxide)​.

  ​

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• C5.

  Increased Breathing Rate.

  • A minor rise in breathing rate prior to exercise is known as the anticipatory rise​.
  • When exercise begins there is an immediate and significant increase in breathing rate, believed to be a result of receptors working in both the muscles and joints​.