Do Now 4/14

1. Do Now 4/14 PSYCHE (SYE kee) n. • the human soul; the mind • The study of poetry often helps students to examine their own PSYCHE. • Because the inmate was so hardened in crime, it was difficult to imagine that he possessed a PSYCHE. • A true appreciation for classical literature engages one’s PSYCHE.

2. Chapter 10: Gas Exchange

3. Gas exchange • Human gas exchange system links circulatory system w/ atmosphere • Clean and warm entering air • Maximize surface area for diffusion of oxygen and carbon dioxide • Minimize distance for diffusion • Maintain adequate gradients for diffusion

4. Gas exchange • Need oxygen for respiration • Multicellular organisms have gas exchange surface where external oxygen can diffuse into body, and carbon dioxide can diffuse out • In humans: alveoli (found in lungs, total surface area over 70m sq)

5. Lungs • Found in thoracic (chest) cavity surrounded by pleural membranes, which enclose an airtight pleural space (aka pleural cavity) • pleural space contains small amount of fluid to reduce friction during ventilation

6. Trachea, bronchi, bronchioles • Leading from the throat to the lungs is the trachea, and at the base are two bronchi (singular: bronchus) which then subdivide several times into even smaller bronchioles

7. Trachea, bronchi, bronchioles • Cartilage in the trachea and bronchi keep airways open and air resistance low, and prevents them from collapsing or bursting as air pressure changes during breathing • Trachea: regular C-shaped cartilage rings • Bronchi: irregular blocks of cartilage

8. Bronchioles • Surrounded by smooth muscle which contract/relax to adjust diameter of airways • Relax= greater diameter, more air • Possible b/c no cartilage

9. Warming and cleaning the air • As air flows through nose and trachea, it is warmed and moistened by evaporation from the lining to protect lungs from drying out (desiccation) • Small hairs inside nose and mucosal membranes trap suspended particles (dust, pollen, bacteria, viruses)

10. mucus • In trachea and bronchi, goblet cells of the ciliated epithelium produce mucus, a slimy solution of mucin, which is composed of glycoproteins with many carbohydrate chains that make them sticky

11. mucus • Also made by mucous glands beneath the epithelium • Some chemical pollutants, like sulfur dioxide and nitrogen dioxide, can dissolve into mucus and irritate the airways

12. mucus • Beneath goblet cells are ciliated cells that carry mucus upwards towards the larynx, where it is (usually) swallowed so pathogens can be destroyed by the acid in our stomachs

13. macrophages • Phagocytic white blood cells patrol the surfaces of the airways scavenging small particles like bacteria and fine dust

14. alveoli • Terminal end of bronchioles. Have very thin lining of epithelial tissues (single cell thick) and are surrounded by capillaries carrying deoxygenated blood • Thinness of barriers ensures fast diffusion • Walls contains elastic fibers which can stretch and recoil during breathing

15. alveoli • Oxygen moves into bloods via partial pressure differences between alveoli (high) and capillaries (low) • Carbon dioxide moves from high in capillaries to low in alveoli • Blood is constantly moving so pressure gradient is maintained