2 Learning OutcomesDescribe the structure of the human gas exchange system, including the microscopic structure of the walls of the trachea, bronchioles and alveoli with their associated blood vessels.Describe the distribution of cartilage, ciliated epithelium, goblet cells and smooth muscle in the trachea, bronchi and bronchioles.Describe the functions of cartilage, ciliated epithelium, goblet cells, mucous glands, smooth muscle and elastic fibers in the gas exchange system.
5 The Gas Exchange System StructuresLungsHave a HUGE surface area to increase efficiency of gas exchangeFound in the thoracic cavity, surrounded by pleural membranesTracheaTube from the pharynx to the bronchiContains c-shaped cartilage rings to prevent collapse and ruptureLined with pseudostratified columnar epithelium with ciliated cells and goblet cells
7 SEM image of trachea epithelium, including both ciliated and non-ciliated epithelial cells (called goblet cells)Goblet cells secrete mucous to trap dust and pathogens, and the cilia sweep it up the trachea so it can be swallowed
9 Structures cont’d Bronchi Bronchioles Two main branches from the tracheaFound in the lungsLead to bronchiolesAlso contain cartilageBronchiolesSmaller branches off of the bronchiSurrounded by smooth muscle to help control diameter (no cartilage)
13 Alveoli Air sacs at the end of bronchioles Simple squamous epithelial lining – single, thin cell layer allows for efficient gas exchangeSurrounded by capillariesGases are exchanged according to partial pressure gradientsAlveoli have elastic fibers to help them to withstand changes in pressure
16 Learning Outcome (d) Describe the process of gas exchange between air in the alveoli and the blood
17 Learning Outcomes(e) Describe the effects of tar and carcinogens in tobacco smoke on the gas exchange system. (f) Describe the signs and symptoms that enable diagnosis of lung cancer and chronic obstructive pulmonary disease (COPD) (emphysema and chronic bronchitis) (g) Describe the effects of nicotine and carbon monoxide on the cardiovascular system.
18 (h) Explain how tobacco smoking contributes to atherosclerosis and coronary heart disease (CHD) Evaluate the epidemiological and experimental evidence linking cigarette smoking to disease and early death.(j) Discuss the difficulties in achieving a balance between preventions and cure with reference to coronary heart disease, coronary by-pass surgery, and heart transplant surgery.
19 Tar and CarcinogensCigarette tar is the residue that is deposited in the airways when the chemical particulates in tobacco smoke condense.It can coat the cilia on the epithelial tissue, preventing them from functioning properly & decreasing gas exchangeThe tar also contains carcinogens, which are toxins that cause cancer
20 Lung CancerSmoking is the leading cause (86%) of lung cancer (second-hand smoke causes 3% of cases)Signs & Symptoms:Persistent & intense coughingChest, shoulder, & back painChange in color & amount of sputumShortness of breathCoughing bloodRecurrent bronchitis or pneumoniaLung tissue biopsy is used to confirm diagnosis & determine the type & stage
21 Chronic Obstructive Pulmonary Disease (COPD) Smoking is the leading cause of COPD, and is reponsible for 85-90% of COPD deathsSigns & Symptoms:CougingIncreased sputum productionShortness of breath & wheezingChest tightnessFatigue
22 COPD continued 2 Main Forms: Chronic bronchitis Emphysema Inflammation of the bronchial tubesPersistent mucus-producing cough, which can lead to damage and scar-tissue formation in the lungsEmphysemaLinings of the alveoli become damaged, turning them into large irregularly shaped air pocketsAlso destroys elastic fibers in the bronchioles, causing them to collapse
25 Carbon MonoxideOne of the 4,000+ chemicals that enters the body as a result of smokingCO binds irreversibly to hemoglobin (forming carboxyhemoglobin), thus preventing the binding of O2Hemoglobin’s affinity for CO is approximately 200x its affinity for O2Since the blood is carrying less oxygen, the heart has to work harder, increasing chances of cardiovascular disease
26 Nicotine Addictive chemical in cigarette smoke Stimulates the nervous systemRelease of adrenalineArterioles constrict (diameter decreases)Leads to an increase in heart rate and blood pressureAlso causes platelets to be stickier, increasing the risk of blood clots
27 AtherosclerosisCaused by a build up plaque called an atheroma in the arteries, narrowing and hardening themAtheroma is composed of cholesterol, dead muscle cells, platelets, and fibersSmoking increases risk of atherosclerosisChemicals in cigarette smoke can damage the endothelium in the arteries, increasing the formation of atheromasHigh blood pressure (caused by nicotine & CO) can contribute to plaque formationSmoking can interact with other risk factors that increase cholesterol level
28 Coronary Heart Disease (CHD) Caused by atherosclerosis in the coronary arteries, which supply oxygen to the heartBlood pressure increases as the heart has to work harder in order to receive enough oxygenBecause smoking increases the risk of atherosclerosis, it increases the risk of CHD
29 CHD Prevention & Treatment CHD Preventative measures include:Diet low in saturated fatRegular exerciseNot smokingTreatment options include:Lifestyle changesSurgical procedures such as angioplasty & coronary bypassCan treat CHD, but it will only be a temporary fix unless lifestyle is changed
30 Epidemiological Evidence Shows correlation but not causation90% of COPD deaths occur in smokers, and COPD is very rare in non-smokers98% of people with emphysema are smokers and 20% of all smokers suffer from emphysemaLung cancer is 18x more likely in smokers than in non-smokers
31 Experimental Evidence Animals exposed to smoke (or forced to smoke) have developed both tumors and COPDCigarette tar was painted on the skins of mice & cancerous growths formed