1. Gas Exchange and Smoking
Part 1

2. Gas Exchange Unicellular Multicellular
O2 diffuses across cell membrane from fluid around cell into cytoplasm
CO2 diffuses out of cytoplasm, across cell membrane, out of organism
Plants & Animals respire
Specialized gas exchange surface in Humans
Alveoli in the lungs

4. Adaptations of Human Respiratory System
Clean, warm air enters during breathing
Increase surface area for diffusion of O2 and CO2 b/t blood and atmosphere
Minimize distance for this diffusion
Maintains diffusion gradients

5. 1. Clean, warm air enters during breathing
Air warmed to body temp
Moistened by evaporation from lining
Protects lung tissue from desiccation (drying out)
Hair and mucus provide protection
Catch particles larger than 5-10 um
Goblet cells
Produce mucus in trachea and bronchi (more about this in a bit…)

6. Alveoli tiny but numerous
2. Increase surface area for diffusion of O2 and CO2 b/t blood and atmosphere
Alveoli tiny but numerous
Collectively large surface area for gas exchange (70 m2)
Increases # of O2 and CO2 molecules that diffuse across surface at any moment
Speed up rate of gas exchange

7. 3. Minimize distance for this diffusion
Capillaries surround each individual alveoli
Enables RBC carrying CO2 to get very close to gas exchange surface (alveoli)
Enables oxygen in alveoli to diffuse across capillaries to haemoglobin in RBC
Diffusion across alveoli wall and across the capillary epithelium is NOT the same as considering diffusion across membranes of individual epithelial cells

8. 4. Maintains diffusion gradients by:
Breathing movements draws air in from outside of the body into lungs and then push it out again
Maintains a relatively high concentration of O2 and low concentration of CO2
Blood flow past alveolus
Deoxy blood brought TO alveoli
Oxy blood carried AWAY from lungs

10. DIAPHRAGM muscle that contracts and relaxes during respiratory cycle

11. Terms and Structures to Know
Cartilage
Ciliated epithelium
Goblet cells
Smooth muscle cells
Elastic fibers
Ciliated Epithelial cell
Cilia
Goblet cell
Basement membrane
Mucus
Lungs
Trachea
Bronchus
Rib
External intercostal muscle
Internal intercostal muscle
Bronchiole
Alveolus

13. pseudostratified ciliated columnar epithelium
relatively avascular and almost wholly cellular (i.e., having little or no connective tissue associated with it) aggregation of cells which are in apposition over a large part of their surfaces, and which are specialized for absorptive, secretory, protective, or sensory activities.
PCCE =
pseudostratified ciliated columnar epithelium

15. Lungs Thoracic cavity Surrounded by pleural membranes (air tight)
small amount of fluid
Prevents friction between lungs, ribs, and diaphragm
Air enters lungs through airways

16. Airways (from largest to smallest)
Trachea
Regular C-shaped rings of cartilage
2 Bronchi (bronchus)
Irregular blocks of cartilage
Bronchioles (many small branches)
Smooth muscle contract/relax to adjust diameter of airways
No cartilage = allow muscles to relax during exercise to allow more O2 in
Terminal bronchioles
Respiratory bronchioles (smaller branches of terminals, hold bunches of grapes/alveoli
Alveoli

20. Overview Cartilage Ciliated epithelium Goblet cells
Trachea and Bronchi
support
Ciliated epithelium
Trachea, bronchi, some bronchioles
Move mucus
Goblet cells
In ciliated epithelium
Produce mucus
Smooth muscle cells
Trachea, bronchi, bronchioles
Widen or narrow tubes
Elastic Fibres
Trachea, bronchi, bronchioles, alveoli
Elasticity

21. Cartilage Found in trachea and bronchi Provide support
Prevents collapse of airway tubes when air pressure is low
C-shaped in trachea
Irregular in bronchi

22. Smooth Muscle Cells Found in walls of
Trachea
Bronchi
Bronchioles
Contracts slowly, over long periods of time, does NOT tire
Contraction reduces diameter of tubes
During exercise, it relaxes, widening tubes, move Oxygen into lungs

23. Elastic Fibers Found in walls of ALL tubes AND between alveoli
Breathing in  fibers stretch to allow alveoli and airways to expand
Breathing out  fibers recoil to help reduce volume of alveoli and expand air out of lungs

24. Goblet cells On ciliated epithelium of trachea and bronchi
Very FEW goblet cells in bronchioles. Why?
Mucus would hinder gas exchange in the alveoli
Upper portion of cell swollen with MUCIN droplets
Mucin (glycoproteins) makes up mucus
Slimy solution (water, proteins, lipids)
Traps inhaled particles
Made also made by mucus glands beneath epithelium

25. Ciliated epithelium Structure Function Sneezing and coughing
Single layer of cells
Outer surface covered with many thin extensions (cilia) that move
Function
Move mucus upwards towards mouth to prevent dust and particles from reaching lungs
Carry mucus upward toward larynx and pharynx (1 cm/min)
Nasal cavity
Move mucus in down respiratory tract, into throat so it can be broken down by enzymes in the stomach and pathogens destroyed by acid in stomach
Trachea and Bronchi
Move mucus up to pharynx to be swallowed
Sneezing and coughing
When large particles are caught in mucus OR build up of mucus in bronchi and trachea

26. Trachea
Lining made of ciliated epithelium resting on basement membrane (basal cells) of protein fibers
Goblet cells in between ciliated cells
Loose tissue and glands beneath epithelium

27. Bronchus Fewer Goblet cells per cm2 than trachea
Epithelial cells not as tall as epithelial cells in trachea
Elastic fibers beneath epithelium
Irregular blocks of cartilage

28. Bronchiole No cartilage Terminal bronchiole Respiratory bronchiole
No Smooth muscle surrounding epithelium of
Connect to alveoli

29. Alveoli Thin epithelial lining
squamous epithelial cells
0.5 um thick
Surrounded by many blood capillaries carrying deoxy. Blood
Oxygen& Carbon dioxide diffuse down their concentration gradients
Walls contain elastic fibers

30. Gas Exchange at Alveolar Surface
Air in alveoli = high Oxygen concentration, low concentration of Carbon Dioxide
High partial pressure of oxygen
Low partial pressure of carbon dioxide
Blood brought to lungs by pulmonary artery = low concentration of oxygen, high concentration of carbon dioxide
Oxygen diffuses through the thin walls of the alveoli and into the capillary
Carbon dioxide diffuses from capillary into alveoli and is breathed out of body

32. Volume of Lungs Tidal Volume (normal) Vital Capacity (max)
Volume of air moved into and out of lungs in one breath
About 0.5 dm3
Vital Capacity (max)
Maximum amount of air that can move in/out of lungs during deepest breath
3-5 dm3

33. Inhale/Exhale Inhalation Exhalation
Contraction of external intercostals and diaphragm
Increases volume of thoracic cavity
Draw in air through trachea through bronchi into bronchioles
Exhalation
Relaxation of external intercostals and diaphragm
Air flows out, down pressure gradient