BIOLOGY OF HUMAN AGING

1. BIOLOGY OF HUMAN AGING Chapter 11 The Respiratory System

3. Human Respiratory System Functions: Works closely with circulatory system, exchanging gases between air and blood: Takes up oxygen from air and supplies it to blood (for cellular respiration). Removal and disposal of carbon dioxide from blood (waste product from cellular respiration). Homeostatic Role: Regulates blood oxygen and carbon dioxide levels.

4. Human Respiratory System Components: Nasal cavity, throat (pharynx), larynx (voice box), trachea, bronchi, alveoli, and lungs. Pathway of Inhaled Air: Nasal cavity Pharynx (Throat) Larynx (Voice Box) Trachea (Windpipe) Bronchi Bronchioles Alveoli (Site of gas exchange) Exhaled air follows reverse pathway.

6. Pressure Relationships

8. Human Respiratory System Nasal cavity: Air enters nostrils, is filtered by hairs, warmed, humidified, and sampled for odors as it flows through a maze of spaces. 2. Pharynx (Throat): Intersection where pathway for air and food cross. Most of the time, the pathway for air is open, except when we swallow. 3. Larynx (Voice Box): Reinforced with cartilage. Contains vocal cords, which allow us to make sounds by voluntarily tensing muscles. More prominent in males (Adam’s apple).

9. Human Respiratory System 4. Trachea (Windpipe): Rings of cartilage maintain shape of trachea, to prevent it from closing. Forks into two bronchi. 5. Bronchi (sing. Bronchus): Each bronchus leads into a lung and branches into smaller and smaller bronchioles, resembling an inverted tree. 6. Bronchioles: Fine tubes that allow passage of air. Muscle layer constricts bronchioles. Epithelium of bronchioles is covered with cilia and mucus. Mucus traps dust and other particles.

10. Human Respiratory System Alveoli (Sing. Alveolus): Grapelike clusters of tiny air sacs with very thin elastic walls through which gas exchange occurs. Oxygen in air enters blood in capillaries. Carbon dioxide in blood enters air in alveoli. There are several million alveoli in the human lungs, with a total surface roughly equivalent to a tennis court. The walls of the alveoli are very delicate. Alveolar macrophages are phagocytic cells that swallow inhaled particles (dust, bacteria, etc.) and digest them.

13. Lung volume and using spirometer

14. Lung volume and using spirometer

15. Age-related changes Trachea and Bronchi Progressive calcification Smooth-muscle replaced by fibrous connective tissue Reduced elasticity of the lungs VC begin to decrease ~ 40 years of age Mucous membrane lining the trachea and bronchi show degenerative changes Decrease activity of cilia and phagocytic activity of the macrophages

16. Age-related changes Alveoli Gradual deterioration of the walls of alveoli The size increases but less surface area for the gas exchange Cross-linkage More collagen fibers and less elastic fibers Declining oxygen levels in the blood

17. Age-related changes Lungs Lose their elastic recoiling capabilities and offer less resistance to expansion Insufficient ventilation? contributing to an overall reduction in oxygen saturation of arterial blood. Surface area Diminished sensitivity of chemo-receptors that monitor oxygen and CO2 levels in the blood.

19. Age-related changes Structural changes Kyphosis and the hunching over reduces the volume of the thoracic cavity and make it more difficult to expand the lungs Loss of Ca and weakening of muscles Diminished elasticity and increases fibrosis of the lungs Stiffness of the rib cage Older individual rely more on the diaphragm

20. Age-related dysfunctions Dysfunctions of respiratory system are more common in older individuals These are not merely a result of aging, rather due to constant exposure to environmental stimuli (air pollution & smoking) Air pollutants damage trachea, bronchi, alveoli Most frequently occurring pulmonary disorders: Restrictive (hinder lung expansion) Obstructive (involve respiratory airways ? increased resistance to air flow

22. Chronic Obstructive Pulmonary Disease (COPD) Characterized by chronic air flow obstruction in lungs Reduction in the ratio of forced expiratory volume in the first second to forced vital capacity (FEV1/FVC) Symptoms: Difficulty breathing, wheezing, cough, etc… Increase rapidly in >50 years of age, frequent in men Cause: Environmental factors and age (also genetic predisposition) 80% of cases is due to cigarette smoking Two most common types: Emphysema & Chronic bronchitis

23. Emphysema Excessive air accumulates in lungs as they lose their ability to ventilate properly More prevalent in older people Gradual development in response to smoking, bronchitis, pulmonary irritants Mechanism Chronic irritation, smoking, infections ? paralyze & deteriorate mucus membrane cilia ? excessive mucus production w/in airways to the lungs ? persistent cough ? collapse of airways ? hinders air flow through lungs ? air becomes trapped in alveoli Trapped air ? alveoli remain inflated ? expiration (normally passive action) requires muscular resistance ? significant energy needed to exhale ? development of Barrel Chest

24. Over-inflated alveoli destroy alveoli’s wall ? replaced by fibrous tissue ? hinder gaseous exchange Early stages: gaseous exchange fairly adequate ? no cyanosis Later stages: great reduction in area where gas exchange occurs ? cyanosis even w/ mild physical effort Patients often have low maximum breathing capacity and high residual air volume The disease can not be reversed and gradually worsens Therapy: positive-pressure oxygen therapy to force O2 into alveoli Emphysema puts extra load on heart (attempts to pump more blood into lungs to compensate for O2 deficiency) Patients suffering from emphysema die from heart failure

26. Dirty lung of an Emphysema (smoking) patient

27. Bronchitis Acute or chronic inflammation of the bronchial tree Caused by bacterial infection or by irritants (smoke in inhaled air) Chronic bronchitis is due to long-term exposure to environmental insults ? more common in elderly Similar to emphysema airway irritation responds by mucus production In severe cases, mucus membrane becomes swollen and partially obstruct airway ? severe hindrance of gas exchange ? cyanosis Excess mucus buildup is removed by persistent coughing

28. Pneumonia Inflammation of the lower airways of the lungs Symptoms: Fever, cough, sputum production (not restricted to older individuals) Classification (due to variability in causative agents): Community acquired: viruses (influenza) or pneumococcus Hospital acquired: gram negative bacilli (E. Coli) or Enterobacter Aspiration pneumonia: inhalation of foods or foreign bodies that obstruct bronchus causes lung collapse, fluid accumulation, infection More common in older (bedridden) individuals

31. Tuberculosis Caused by mycobacterium tuberculosis ; enters body with inspired air ? lung tuberculosis is the most common form Symptoms: early (subtle) weight loss, fever, cough Diagnosis: skin test, chest x-ray, sputum culture Lung phagocytes ? destroy the bug ? alive bacteria are walled off in small or calcified nodules (Tubercle) Evading bacteria ? spread ? lung tissue replaced by fibrous tissue ? reduced vital capacity and difficulty breathing Antibiotics harnessed TB till mid-80s ? resurgence due to AIDS Role of immune system in controlling outward signs of the disease Dormancy ? impaired immune system ? Reactivation tuberculosis

33. Pulmonary Embolism Ambolus: blood clot or foreign objects that flows freely w/in blood vessels Can reach vessels with small diameter, can not pass through them ? partial or complete block ? reduced blood flow to the tissue ? tissue dies Pulmonary embolism: a clot that blocks a branch of pulmonary artery Symptoms: shortness of breath, chest pain, spitting blood, accelerated heart beat and breathing rate, anxiety Can occur at any age, more common in bedridden older individuals Immobile patients tend to develop clots in leg veins (low blood flow) Treatment: Anticoagulant drugs (streptokinase)