1. Functions

• filters, warms air
• sound production
• oxygen/carbon dioxide exchange online example
• aids venous return

The Air Passageways

Respiratory tract anatomy online

2. Upper Respiratory Tract

• Nasal cavity anatomy
  - nostrils are external nares
  - communicate with paranasal sinuses in bones

1. frontal
2. maxillary
3. sphenoid
4. ethmoid
 online sinuses

- vestibule contains 3 conchae
- functions to warm air, trap dust, resonation
- surface is pseudostratified columnar epithelium

• Pharynx  regions
  - nasopharynx contains: adenoids and eustachian tubes
  - oropharynx contains

1. fauces to mouth
2. palatine and lingual tonsils

- laryngopharynx bifurcates into larynx and esophagus

3. Lower Respiratory Tract

• Larynx
  - cartilages

1. thyroid cartilage
2. epiglottis
3. cricoid
4. arytenoid

- contains vocal cords, these are elastic ligaments that vibrate to produce sound
- muscle stretches ligaments
- air is forced against cords

• Trachea
  - contains four layers of tissue

1. mucosa
2. submucosa
3. hyaline cartilage
4. serosa (not shown)

- windpipe with C rings of hyaline cartilage
- anterior to esophagus
- bifurcates into right/left primary bronchi
- bronchial tree online

• Bronchi
  - right is wider and more vertical
  - primary becomes secondary becomes tertiary

• Bronchioles
  - terminal bronchioles become respiratory bronchioles  
     become alveolar ducts
  - histological changes

  1. ciliated columnar cells change to cuboidal cells
  2. cartilage changes to smooth muscle

Lung Anatomy

4. Lungs

• pleural cavity between parietal and visceral pleura allows expansion
  note the position of the following
  

1. base
2. apex
3. costal surface
4. mediastinal surface
5. hilus
6. cardiac notch

• functional unit is cup-shaped squamous epithelium called an ALVEOLI which contains:

1. Type I cells- for gas exchange
2. Type II cells - secrete surfactant
3. Macrophages - phagocytes
                          - in emphysema these produce the enzyme
                            trypsin which destroy the alveolar walls
4. Fibroblasts - secrete elastic fibers

1. gas exchange through a .5 um thick wall
2. note: 2 cells and 2 basement membranes are involved
3. Type I cells, basement membrane, basement membrane, then
    capillary cells
4. action:  diffusion of gases

Inspiration/Expiration

5. Pulmonary Ventilation

• gas exchange due to pressure gradient
• gases cross the alveolar/capillary membrane by diffusion
• respiratory muscles and elastic tissue change pressure gradient follows
  Boyle’s Law : volume and pressure of a gas are inversely related
• eupnia: normal breathing involves 3 pressures
• the following pressure gradients move air in and out of the lungs

1. Atmospheric Pressure - air pressure

2. Intrapulmonic Pressure - pressure inside the alveoli - varies

3. Intrapleural Pressure -pressure in the pleural space - lower

• INSPIRATION

- Boyle's Law:  volume increases, pressure decreases
- diaphragm contracts, dome flattens, phrenic nerve causes this
- ribcage rises and thoracic cavity expands
- intrapulmonic pressure decreases
- air flows from 760 mmHg to 758 mmHg
- muscles of forced inspiration are sternocleidomastoid, pectoralis minor, and
  external intercostals

• EXPIRATION

- volume decreases, pressure increases
- diaphragm relaxes, dome shape returns
- rib cage lowers
- intrapulmonic pressure rises to 762 mmHg
- air flows out due to the elastic recoil of the lungs
- lung surfactant  reduces the surface tension and causes elastic recoil
- muscles of forced expiration are the abdominals and internal intercostals
 

6. Compliance - ease of breathing

• measures lung elasticity and surface tension
• high: lungs expand easily with pressure gradient
  NOTE: loss of elastic fibers in emphysema make inspirations easy and expirations difficult
• low: increased surface tension due to lack of surfactant or loss of elastic fibers
  NOTE: lung walls are rigid as in fibrosis, breathing requires more work
• emphysema histology online