Respiratory System

• Functions:

  • Supply cells with oxygens
  • Remove carbon dioxide waste.
• Nasal Cavity:

  • Filters, warms and moistens air
  • Projections increase the internal surface area
  • Smell receptors, hair and mucus trap dust
• Pharynx:

  • The throat
  • Air passes from the nasal cavity through here.
• Larynx:

  • The voice box
  • Air passes through the larynx, going to and from the lungs.
  • Contains the vocal cords which can vibrate to make sound.
• Epiglottis:

  • A flap of tissue that closes off the trachea during swallowing.
  • Prevents food and lipid entering the lungs
• Trachea

  • Carries air to and from the lungs
  • Lined with a mucous membrane and cells with cilia.
  • Cilia beat to move mucus and trapped particles upwards.
• Lungs:

  • Occupy the chest cavity
  • Left lung has an indentation for the heart
  • Covered by a pleural membrane that also lines the inside of the chest.
  • Pleural fluid between the two layers holds the lung against the inside of the chest.
•  

  Bronchi:

  • Two primary bronchi branch from the trachea
  • They then divide into secondary and tertiary bronchi
• Bronchioles:

  • Very fine tubes with walls of smooth muscle
  • The finest of them end in groups of air sacs, the alveoli
• Alveoli:

  • Tiny air sacks that are one cell thick
  • Very thin to allow gas exchange
• Ribcage:

  • Framework for the chest.
  • Protects the lungs and other organs
  • Used with intercostal muscles during breathing.
• Intercostal Muscles:

  • Muscles between the ribs
  • Move the rib cage upwards and outwards to increase the volume of the chest cavity and thus the lungs when breathing in.
• Diaphragm:

  • A muscle that separates the chest from the abdomen
  • Contracts and flattens downwards - increasing the volume of the chest cavity and lungs during inhalation.
• Gas Exchange

  • To allow blood to receive oxygen from air and allow carbon dioxide to leave the body.
  • Gases move from high ---> low concentration.
  • Alveoli are suited to this task as they:

  1. Have a large surface area
  2. Capillaries nearby  for blood supply
  3. One cell thick for easy diffusion
  4. Deep in the body to prevent fluid evaporation.
• Pathway of carbon dioxide into the Alveoli:

  1. Deoxygenated blood (high in carbon dioxide and in oxygen - Carbaminohaemoglobin) must be transported from the pulmonary artery to the alveoli to be expelled from the body.
  2. The capillary network has a high concentration of CO2 and a low concentration of O2.
  3. This CO2 blood will need to be diffused from the capillary network (1 cell thick wall) and into the thin and moist alveoli wall to be expired.
• Pathway of oxygen from Alveoli to blood Capillary:

  • Oxygen will move from high concentration are to a low concentration area inside the alveoli.
  • Then the oxygen will diffuse through the thin and moist alveoli wall and continue through 1 cell thick walls of the capillary network.
  • Oxygen will then diffuse into the blood, attaching to a red blood cell. This now becomes oxygenated blood called oxyhaemoglobin.
  • Then the blood will now become high in oxygen and low in CO2 and will travel to the heart via the pulmonary vein for oxygenated blood to be pumped around the body to working muscles.
• Inspiration:

  • The process of taking air into the lungs
  • The diaphragm and intercostal muscles contract and chest cavity expands
  • Lung volume increases and lung pressure becomes less than air outside the lungs --> air flows in.
• Expiration:

  • The process of breathing out
  • The diaphragm and intercostal muscles relax so that lung volume decreases.
  • Lung volume decreases and lung pressure becomes greater than pressure outside then lungs --> air flows out.