Respiratory System Anatomy and Physiology

Parts of the Respiratory System  Nasal Cavity  Pharynx – common passage of food and air  Larynx – 8 rings or cartilage and the mucous membrane has 2 pairs of folds – vocal cords – vibrate for speech  Epiglottis – flap of cartilage that closes off the larynx when swallowing so that food goes down the esophagus and not to the lungs (if anything but air enters the larynx – it causes us to cough)  Thyroid cartilage – big piece of shield-shaped cartilage in front of the larynx (Adam’s apple) – only males have  Trachea – windpipe (4”) – lined with ciliated mucosae – reinforced with cartilage rings to keep it open

Parts Continued  Bronchi – trachea divides into 2 to go to each lung  Bronchioles or bronchiole tree – smaller and smaller branches  Alveoli – air sacs lined with epithelium  Lungs – most of the lungs are made of the alveoli (millions) with connective tissue  Left lung – 2 lobes/ Right lung – 3 lobes  Covered by serous membrane (pleura) – keep the lungs from rubbing against the thoracic cavity and adhere lungs to the chest wall for inflation during breathing

Alveoli  Happens from the alveoli to the capillaries by simple diffusion (oxygen enters the capillaries and carbon dioxide leaves them and enters the alveoli)  Macrophages move in and out and destroy bacteria that get in  Embedded in the epithelial cells are cells that make lung surfactant – lipid coating that keeps alveoli from collapsing  Surface area for gas exchange of each lung is about the size of 1 tennis court

Alveoli

Breathing  Diaphragm contracts (pulls down)  The volume in the lungs increases so the pressure decreases  Atmospheric pressure is higher than the pressure in the lungs so it automatically flows in  Intercostal muscles also expand the ribs aiding in lung expansion and the decrease in pressure (lungs adhere to the thoracic wall by the pleural membrane)

Breathing Continued  Tidal Volume – volume of air inhaled and exhaled (500 mls/1pt.)  Inspiratory Reserve Volume – amount that can forcibly be taken in over tidal volume ( mls)  Vital capacity – Maximum air the lungs can hold (4500 mls)  Expiratory Reserve Volume – amount that can be forcibly exhaled after tidal expiration (about 1000 mls)  Residual Volume – amount of air left in the lungs even after forced expiration (about 1000 mls) – allow gas exchange between breaths and keeps alveoli inflated  Sneezing and coughing clear the air passages of debris and excess mucous

Gas Exchange  Oxygen diffuses from inside the alveoli (20%) to the capillaries of the lungs (~0%)  Most of it is picked up by hemoglobin  After the blood is pumped to the body and reaches the capillaries of the body’s tissues – the oxygen is dumped off by hemoglobin and diffuses out of the RBC into the interstitial fluid surrounding the cells – it then diffuses into the cells

How does more Oxygen Get to the Cells that Need it the Most? i.e. cells doing the most work 1. Blood is diverted to the most active areas (precap. sphincters shut off blood to certain areas not in use) 2. Hemoglobin drops off Oxygen quicker in areas of low oxygen and high CO 2 (higher acidity) 3. The higher the concentration difference of oxygen between blood and cells, the faster the rate of diffusion

Control of Respiration  Controlled by the autonomic nervous system  Normally breath times/minute  Do have some conscious control over breathing but autonomic centers will ignore information if ph of blood is low (can’t hold your breath until you die)  Mostly controlled by level of carbon dioxide in the blood (pH) – act on the medulla oblongata in the brain  Oxygen concentration is also measured in the aorta and carotid arteries which send signals to the medulla – only when oxygen is dangerously low  Hyperventilating – breathing real fast – lose too much carbon dioxide too fast, blood becomes a little basic and breathing may stop – breath into a bag to increase carbon dioxide levels

Lung Disease  COPD – usually caused by smoking – hard to breath, coughing, lung infections, don’t properly get rid of carbon dioxide –Emphysema - lungs become less elastic and airways collapse during expiration so air can’t get out – take huge amounts of energy to exhale –Chronic Bronchitis – mucous membranes become inflamed and excess mucus clogs air passages  Lung cancer – 1/3 of all cancer deaths – over 90% of people with lung cancer smoked – about 15 carcinogens in cigarette smoke – metastasizes quickly with a 7% survival rate