1. The Respiratory System
Internal Systems and Regulation

2. Video: What do the lungs do?
(3:21)

3. Mammalian Respiration
Respiration is made up of 4 parts:
Breathing – inspiration (inhalation) and expiration (exhalation)
External Respiration – gas exchange between air and blood
Internal Respiration – gas exchange between blood and cells of the surrounding tissue
Cellular Respiration – metabolic reactions/processes in cells
Respiratory Tract
Upper and Lower
External respiration is a physical process during which oxygen is taken up by capillaries of lung alveoli and carbon dioxide is released from blood.
Internal respiration or tissue respiration/cellular respiration refers to a metabolic process in which oxygen is released to tissues or living cells and carbon dioxide is absorbed by the blood. Once inside the cell the oxygen is used for producing energy in the form of ATP 

4. Upper Respiratory Tract
Nostrils
Air is passed into the nasal passages
Turbinates (thin bones in nasal passage) secrete mucous to moisten the air
Many capillaries warm incoming air
Tiny hairs filter foreign particles
Pharynx – connects mouth and nasal cavity to trachea and esophagus
Glottis – opening of the trachea
Epiglottis – protects the glottis as it is a flap like structure and prevents food from entering trachea
Must warm and moisten incoming air so it doesn’t dry out sensitive lung cells that must remain wet

5. Upper Respiratory Tract
Larynx – voice box
Holds the vocal cords using a cartilaginous material
When breathing, muscles attached to the folds are relaxed and when we prepare to speak the muscles contract bringing the folds closer together and they vibrate. (p.286, fig. 2)
Trachea – windpipe
Supported by cartilage rings  keep it open
Cilia-tiny hairs on cells help sweep debris back into pharynx
Most structures in upper respiratory tract are lined with mucous traps particles, keeps cells lining cavities moist
Larynx sits above trachea and in front of esophagus. 2 inch long tube
Vocal cords: mucous membrane foldings/sheets of elastic ligaments

7. Lower Respiratory Tract
Trachea branches into bronchi
Each bronchus subdivides into bronchioles
Each bronchiole ends in a cluster of tiny sacs known as alveoli, surrounded by capillaries
This is where gas exchange (external respiration) takes place
Gases diffuse between air and blood according to concentration gradients. O2 and CO2 move from areas of high to low concentration
Each lung contains ~150 million alveoli: provides enough surface area to cover half a tennis court!
Bronchi has cartilaginous rings, bronchioles don’t

9. Lower Respiratory Tract
Each lung is divided into lobes
Right has 3, left has 2
A bronchus enters each lobe
Lungs are enveloped in tissue called pleura which contains the lungs but allows them to expand and contract (reduces friction with chest cavity)

10. Mechanics of Breathing
Two muscular structures allow ventilation:
Intercostal muscles – muscles that run between the ribs of the rib cage
Diaphragm – dome-shaped sheet of muscle that separates chest cavity from abdominal cavity
Both work in unison to move air in and out of the lungs to allow ventilation.

12. In order to breathe, we need:
Lungs with a moist respiratory surface
Need water (mucous) for oxygen to dissolve into before it can diffuse into cells
A means of forcibly bringing air into contact with the lung surface.
A circulatory system to move the gases around the body.