RESPIRATORY SYSTEM

Increasing complexity in respiration Earthworms – gases diffuse through skin Insects – tracheal system (limited capacity) Fish – gills (good for aquatic environments) Frogs – balloon-like lungs (increased surface area) Mammals – complex respiratory system

Main function? To ensure that O 2 is brought into the body and ready for cellular use all the time (cellular respiration in mitochondria) sugar + 6 O 2  32 ATP + 6H 2 O + 6 CO 2 To ensure that CO 2 can leave each cell and is removed from the body (we can’t store it)

Stages of respiration Breathing (inspiration and expiration) Gas exchange inside the lungs and between blood and cells (also cellular respiration – inside the cell)

In order for gas exchange to occur, several requirements are essential: 1) a tube to connect internal/external environments 2) muscles to bring the air in contact with the exchange surface 3) a moist surface where gas exchange occurs through diffusion

How does it work? a.k.a. The mechanics of breathing The brain controls it all – breathing movements, breathing rate, air volume, gas levels in blood, etc. What causes air to move in and out of lungs? Changes in air pressure – controlled by the diaphragm and rib (intercostal) muscles

Inhalation Rib muscles contract and diaphragm moves down This expands the rib cage upward and outward, floor of chest cavity moves down volume of lungs increases (they expand) therefore air comes in (pressure inside lungs is lower than pressure outside lungs, air moves along the concentration gradient)

Exhalation Begins when diaphragm and rib muscles relax – reduces volume of chest cavity ribs move in and diaphragm moves up volume of lungs decreases (higher pressure), and air is forced out (lower pressure outside)

Muscles to Pull Air in/Push it Out the ribs and the diaphragm work together to bring air in and push it out

Human Respiratory System Two parts, upper and lower respiratory tracts (passageways) 1) Upper Tract air enters the body through nostrils then nasal passages (also through mouth during exercise) passes through the pharynx (throat) to the opening of the trachea (windpipe – made of c- shaped cartilage rings to keep it open) travels down the trachea (made of cartilage rings to keep it open)

Opening is called the glottis, can be closed by the epiglottis (covers the glottis when eating) The larynx (voice box) is between the glottis and trachea - two vocal chords, which move closer together, as air passes they vibrate to make sound Then air goes down the trachea (10-12 cm long), then into two tubes (the lower respiratory tract)