The Respiratory System

Respiratory System A. Purpose is to take in oxygen for cellular respiration and get rid of CO2 made 1. Ventilation – act of breathing in and out using lungs a. Maintains concentration gradient for diffusion in lungs

II. Structures Lungs – sponge like structures on either side of heart Divided into lobes – 2 on left, 3 on right side Air must be processed before it enters – filtered, cleaned, warmed, moistened

Nose 1. Hair in nostrils filters air by trapping dust, pollen, etc. 2. Lined by mucous membrane to moisten and warm air 3. Cells have cilia which trap bacteria a. Get coated with mucus, swallowed, and destroyed by stomach acid

Pharynx (Throat) 1. Nose and mouth come together, divides into esophagus and trachea

Larynx (Voicebox) 1. Between pharynx and trachea 2. Made of muscle and ligaments (vocal cords) 3. Epiglottis – flap of tissue – if open, air flows to trachea, closes when you swallow to direct food to esophagus

Trachea (wind pipe) 1. Like a vacuum cleaner hose – rings of cartilage keep it strong 2. Contains mucus to trap debris and cilia to move it back up to throat so it can be swallowed

Bronchi – trachea divides into two tubes, one goes to each lung Bronchioles – bronchi branch into smaller tubes

Alveoli Small air sacs, about 300 million per lung Provide surface area for gas exchange Surrounded by capillary beds – O2 diffuses into blood, CO2 diffuses into alveoli to be exhaled

III. Mechanics of breathing A. Lungs contain no muscle, so the work of breathing must be done by surrounding muscles 1. Diaphragm – sheet of muscle separating chest and abdomen 2. Intercostal muscles – between ribs

Inhalation 1. Diaphragm contracts – moves downward 2. External intercostals contract, expanding ribs outward 3. This expands the chest cavity, increasing its volume and lowering pressure 4. Because pressure in the lungs is now lower than air pressure outside the body, air is sucked in

Exhalation 1. Diaphragm relaxes – moves upward 2. Internal intercostals contract, pulling ribs inward 3. Decreases volume of lungs, increasing pressure 4. Pushes air out

IV. Lung disorders A. Emphysema (COPD – chronic obstructive pulmonary disease) – alveoli destroyed 1. Causes – smoking, pollution 2. Alveoli become large, irregularly shaped with gaping holes which reduces surface area for gas exchange Healthy lung

Lung Cancer 1. Prone to metastasize to brain, bones, liver, adrenal glands (high mortality rate) 2. Takes over space of healthy tissue 3. Often caused by smoking