respiratory & digestive system

• Respiratory system


  Biological system consisting of specific organs and structures used for gas exchange in humans
• Components of the respiratory system

  • Nose and nasal cavity
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi and smaller branches
  • Lungs containing alveoli
• Functional zones of the respiratory system

  • Respiratory zone (site of gas exchange)
  • Conducting zone (filters, warms, and moistens incoming air)
• Respiration


  1. Ventilation

  2. External respiration

  3. Internal respiration

  4. Transport of respiratory gases in the blood
• External respiration


  Process of inhaling oxygen into the lungs, and exhaling carbon dioxide
• Internal respiration


  Metabolic process by which living cells use blood flowing through the capillaries, absorbing the oxygen they need and releasing the carbon dioxide they create
• Nose


  • Provides an airway for respiration
  • Moistens and warms entering air
  • Filters and cleans inspired air
  • Serves as a resonating chamber for speech
  • Houses the olfactory (smell) receptors
• Openings into the pharynx

  • 2 openings from the eustachian tubes of the ear
  • 2 openings from the posterior nares of the nose
  • 1 opening from the mouth
• Lymphatic tissues in the pharynx

  • Pharyngeal tonsils (adenoids)
  • Palatine tonsils
  • Lingual tonsils
• Functions of the pharynx

  • Serves as a passageway for air
  • Serves as a passageway for food
  • Aids in phonation by changing its shape
• Larynx


  • Commonly called the voicebox
  • Located at the upper end of the trachea, below the root of the tongue and hyoid bone
  • Lined with mucous membrane
  • Contains vocal cords which produce sound
• Vocal cords


  • Short, tense vocal cords produce high notes
  • Long relaxed vocal cords produce low notes
• Cartilage structures of the larynx

  • Thyroid cartilage (Adam's apple)
  • Epiglottis
  • Cricoid cartilage
• Trachea


  • Smooth, muscular tube leading from the larynx to the main bronchi
  • Cartilage rings prevent crushing of the trachea
  • Passageway for air to and from the lungs
  • Lined with cilia (hairs) which sweep foreign matter out of the pathway
  • About 1 inch in diameter and 4 1/2 inches long
• Bronchi


  • Two main branches at the bottom of the trachea, providing passageway for air to the lungs
  • Divide further into the bronchial tree
  • As branches get smaller, become bronchioles and then alveolar ducts
• The left bronchi is smaller than the right bronchi, because room is needed to accommodate the heart
• If a foreign body is inhaled or aspirated, it usually lodges in the larger right bronchi or enters the right lung
• Lungs


  • Two spongy organs located in the thorax
  • Consist of elastic tissue, filled with an interlacing network of tubes and sacs that carry air and blood vessels that carry blood
  • Right lung divided into 3 lobes, left lung divided into 2 lobes
  • Left lung has an indentation called the cardiac depression or notch for placement of the heart
• Alveoli


  • Air cells at the end of each bronchiole where the exchange of oxygen and carbon dioxide takes place with the capillaries
  • Lungs contain about 300 million alveoli sacs
• Diaphragm


  • Muscular wall separating the thorax from the abdominal cavity
  • Involved in respiration, drawing downward in the chest during inhalation, and pushing upward during exhalation
• Tidal volume


  Amount of air inhaled or exhaled during normal breathing, about 500 ml
• Total lung capacity


  3.6-9.4 liters in an average male
• Pulmonary ventilation


  The act of breathing, movement of air into and out of the lungs
• Atmospheric pressure (Patm)


  Air pressure surrounding the body
• Alveolar pressure (Palv)


  Air pressure within the alveoli
• Intrapleural pressure (Pip)


  Pressure within the pleural cavity
• Boyle's law


  Pressure of a gas is inversely proportional to its volume
• Atmospheric pressure


  • Amount of force exerted by gases in the air surrounding any given surface, such as the body
  • Can be expressed in terms of the unit atmosphere (atm) or millimeters of mercury (mm Hg)
  • One atm is equal to 760 mm Hg, which is the atmospheric pressure at sea level
• Intra-alveolar pressure


  Pressure of the air within the alveoli, changes during different phases of breathing
• Intrapleural pressure


  • Pressure of the air within the pleural cavity, between the visceral and parietal pleurae
  • Always lower than, or negative to, the intra-alveolar pressure (and therefore also to atmospheric pressure)
  • Fluctuates during inspiration and expiration but remains approximately -4 mm Hg throughout the breathing cycle
• The lungs themselves are passive during breathing, meaning they are not involved in creating the movement that helps inspiration and expiration
• Contraction and relaxation of the diaphragm and intercostals muscles cause most of the pressure changes that result in inspiration and expiration
• Resistance


  • Force that slows motion, in this case the flow of gases
  • The size of the airway is the primary factor affecting resistance
• Inspiration


  Process that causes air to enter the lungs
• Expiration


  Process that causes air to leave the lungs
• Respiratory cycle


  One sequence of inspiration and expiration
• Muscle groups used during normal inspiration

  • Diaphragm
  • External intercostal muscles
• Tidal volume (TV)


  Amount of air that normally enters the lungs during quiet breathing, about 500 ml
• Expiratory reserve volume (ERV)

  Amount of air you can forcefully exhale past a normal tidal expiration, up to 1200 ml for men
• Inspiratory reserve volume (IRV)


  Extra volume that can be brought into the lungs during a forced inspiration