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