Learning Objectives  Explain, with the use of diagrams, the process of breathing  Examine Respiratory Tissue slides under the microscope and Identify tissue types within them

Mechanism of breathing …  Movement of the ribcage and diaphragm ventilate the lungs.  This is important:  Inspiration (inhalation) brings fresh supplies of O 2 to maintain the O 2 concentration gradient.  Expiration (exhalation) removes waste air with its cargo of CO 2 to maintain the CO 2 gradient.  Movement of respiratory gases is by diffusion so it is driven by concentration differences.

Inspiration  External intercostal muscles contract, pulling the ribcage upwards and outwards.  Diaphragm contracts, pulling it from a domed to a flattened shape.  Combined effect is:  volume of the thorax and lungs increase  pressure is reduced  air enters, goes down the pressure gradient.

Expiration - relaxed  External intercostal muscles relax and the ribcage falls under its own weight.  Diaphragm relaxes and gut pressure pushes it back into its domed shape.  Elastic recoil of lung tissue.  Combined effect is:  volume of the thorax and lungs decrease  pressure is increased  air is forced out.

Expiration - forced  Internal intercostal muscles contract, pulling the ribcage down and in.  Abdominal muscle contracts pushing the diaphragm upwards.  Combined effect is:  volume of the thorax and lungs decrease  pressure is increased  air is forced out.  Exercise, singing, playing a wind instrument.

To Do:  Draw diagrams to explain the process of breathing.  Help yourself to a Microscope and examine slide of lung tissue under high magnification – What tissues do you expect to see? Can you identify some of these tissues?

bronchiole and alveolar tissue Lumen or airway Epithelium – ciliated in bronchiole but not respiratory bronchiole Smooth muscle Alveolar space Capillary – blood vessels have been injected with dye Alveolar wall cell (nucleus purplish stain)

Trachea Blood vessel with numerous blood cells clearly visible Cilia Goblet cell Cartilage – chondrocytes clearly visible Ciliated epithelium Smooth muscle Elastic tissue

PREP  The content of today’s lesson (found on page 46 – 49) to be written up, in the format of your choice, in your Prep Books  To be completed and checked by next lesson (Monday)