1. Gas Exchange and Smoking
AICE Biology Topic H

2. Learning Outcomes
Describe 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.

3. Human Respiratory System

4. Typical Respiratory Epithelium

5. The Gas Exchange System
Structures
Lungs
Have a HUGE surface area to increase efficiency of gas exchange
Found in the thoracic cavity, surrounded by pleural membranes
Trachea
Tube from the pharynx to the bronchi
Contains c-shaped cartilage rings to prevent collapse and rupture
Lined 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 trachea
Found in the lungs
Lead to bronchioles
Also contain cartilage
Bronchioles
Smaller branches off of the bronchi
Surrounded by smooth muscle to help control diameter (no cartilage)

10. Bronchus cross-section

11. Bronchiole c.s. – no cartilage, walls reinforced only with smooth muscle

13. Alveoli Air sacs at the end of bronchioles
Simple squamous epithelial lining – single, thin cell layer allows for efficient gas exchange
Surrounded by capillaries
Gases are exchanged according to partial pressure gradients
Alveoli 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 Carcinogens
Cigarette 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 exchange
The tar also contains carcinogens, which are toxins that cause cancer

20. Lung Cancer
Smoking is the leading cause (86%) of lung cancer (second-hand smoke causes 3% of cases)
Signs & Symptoms:
Persistent & intense coughing
Chest, shoulder, & back pain
Change in color & amount of sputum
Shortness of breath
Coughing blood
Recurrent bronchitis or pneumonia
Lung 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 deaths
Signs & Symptoms:
Couging
Increased sputum production
Shortness of breath & wheezing
Chest tightness
Fatigue

22. COPD continued 2 Main Forms: Chronic bronchitis Emphysema
Inflammation of the bronchial tubes
Persistent mucus-producing cough, which can lead to damage and scar-tissue formation in the lungs
Emphysema
Linings of the alveoli become damaged, turning them into large irregularly shaped air pockets
Also destroys elastic fibers in the bronchioles, causing them to collapse

25. Carbon Monoxide
One of the 4,000+ chemicals that enters the body as a result of smoking
CO binds irreversibly to hemoglobin (forming carboxyhemoglobin), thus preventing the binding of O2
Hemoglobin’s affinity for CO is approximately 200x its affinity for O2
Since 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 system
Release of adrenaline
Arterioles constrict (diameter decreases)
Leads to an increase in heart rate and blood pressure
Also causes platelets to be stickier, increasing the risk of blood clots

27. Atherosclerosis
Caused by a build up plaque called an atheroma in the arteries, narrowing and hardening them
Atheroma is composed of cholesterol, dead muscle cells, platelets, and fibers
Smoking increases risk of atherosclerosis
Chemicals in cigarette smoke can damage the endothelium in the arteries, increasing the formation of atheromas
High blood pressure (caused by nicotine & CO) can contribute to plaque formation
Smoking 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 heart
Blood pressure increases as the heart has to work harder in order to receive enough oxygen
Because smoking increases the risk of atherosclerosis, it increases the risk of CHD

29. CHD Prevention & Treatment
CHD Preventative measures include:
Diet low in saturated fat
Regular exercise
Not smoking
Treatment options include:
Lifestyle changes
Surgical procedures such as angioplasty & coronary bypass
Can treat CHD, but it will only be a temporary fix unless lifestyle is changed

30. Epidemiological Evidence
Shows correlation but not causation
90% of COPD deaths occur in smokers, and COPD is very rare in non-smokers
98% of people with emphysema are smokers and 20% of all smokers suffer from emphysema
Lung 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 COPD
Cigarette tar was painted on the skins of mice & cancerous growths formed