BIOLOGY OF HUMAN AGING

1. BIOLOGY OF HUMAN AGING CHAPTER 11 The Respiratory System

2. 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.

3. 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.

4. Human Respiratory System

5. Pressure Relationships Figure 22.12

6. Blood Transports Gases Between Lungs and Tissues

7. Human Respiratory System 1. 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).

8. 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.

9. 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.

10. Exchange of Gases Occurs in Alveoli

11. Human Breathing: Inhalation and Exhalation

12. Lung volume and using spirometer

13. Lung volume and using spirometer

14. 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

15. 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

16. 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 chemoreceptors that monitor oxygen and CO2 levels in the blood.

17. Human Breathing is Automatically Controlled

18. 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

19. Age-related Dysfunctions • Chronic Obstructive Pulmonary Disease (COPD) • Emphysema • Chronic bronchitis • Pneumonia • Tuberculosis • Pulmonary Embolism