RESPIRATORY SYSTEM

I. Functions of the Respiratory System

A. Gas Exchange

B. Nonspecific Defense

C. Vocal Communication

D. Controls pH

II. Organization of the Respiratory System

A. Upper Respiratory Tract
1. Nose
2. Nasal cavity

a. Nasal septum
b. Nasal conchae
c. Mucous membrane
d. Internal Nares
e. Hard Palate
f. Soft Palate

3. Sinuses
    a. Bones:
    b. Lined with mucous membrane
    c. Functions

1.
2.
3.

4. Pharynx

a. Function:

b. Divisions:

5. Larynx

a. Thyroid cartilage
b. Cricoid cartilage
c. Arytenoid cartilage
d. Corniculate cartilage
e. Epiglottis

1. Glottis

2. Epiglottitis - epiglottis swells 10x its normal size

f. Vocal cords

1. False vocal cords (ventricular folds) - superior

2. True vocal cords (vocal folds) - inferior

6. Trachea

a. Tracheal cartilages

b. Splits at level of 5th thoracic vertebrae to form right and left primary bronchi

B. Lower Respiratory Tract

1. Primary bronchi

2. Secondary (lobar) bronchi

3. Tertiary (segmental) bronchi

4. Bronchioles

5. Terminal bronchioles

6. Respiratory bronchioles

7. Alveolar ducts

8. Alveolar sacs (made of individual "alveoli")

a. Type I alveolar cells

b. Type II alveolar cells ("Surfactant Cells")

1. Produce surfactant

2. Surfactant function:

c. Alveolar macrophages

d. Respiratory Distress Syndrome

C. Respiratory Membrane

1. Epithelial cells

2. Endothelial cells

3. Basement membrane

D. Lungs

1. Membranes

a. Parietal pleura -
b. Visceral pleura -
c. Pleural cavity -
d. Pleurisy

2. Lobes

a. Right lung
b. Left lung

E. Smoking and its Effects on the Respiratory System

1. Cilia paralyzed
2. Mucus production
3. Decreased oxygen-carrying capacity (CO in cigarettes)
4. Carbon particles in lungs (macrophages)
5. Emphysema
6. Lung cancer
7. Chronic Bronchitis

F. Respiratory Changes At Birth

1. Before birth, pulmonary vessels are collapsed, ribs and air passageways compressed

2. Small amounts of fluid inside respiratory passageways until first breath

3. After first breath, cartilages keep airway open, surfactant keeps alveoli open

III. Respiratory Physiology

A. Breathing (pulmonary ventilation)

B. External Respiration -

C. Internal Respiration -

D. Pulmonary Ventilation

1. Inspiration (inhaling)

a. Atmospheric pressure ~ 760 mm Hg

b. Boyle’s Law -

c. Diaphragm (phrenic nerves) and external intercostals

d. Intra-alveolar pressure - equalizes with atmospheric pressure

e. Parietal and visceral pleura

1. Serous fluid creates surface tension (~4 mm Hg)

2. Membranes are pulled outward during inspiration

3. Compliance -

4. Pneumothorax -

5. Atelectasis -

f. Inspiration creates a negative intra-alveolar pressure

g. Other muscles groups

1. Pectoralis minor

2. Sternocleidomastoid

2. Expiration (exhaling)

a. Factors involved in causing air to move out of the lungs

1. Elastic recoil of lungs

2. Abdominal organs

3. Intra-alveolar surface tension

b. Forcibly exhaling

1. Internal intercostals

2. Abdominal muscles

E. Respiratory Volumes and Rates (Spirometry Measurements)

1. Tidal volume (TV)

2. Inspiratory reserve volume (IRV)

3. Expiratory reserve volume (ERV)

4. Vital Capacity (VC) = TV + IRV + ERV

5. Residual volume (RV)

6. Minimal Volume

7. Total lung capacity (TLC) = VC + RV

8. Anatomic dead space

9. Minute ventilation = TV x breathing rate

F. Gas Exchange at the Respiratory Membrane

1. Mixed Gases and Partial Pressures

a. Dalton’s Law of partial pressures -

b. Henry’s Law -

1. Carbon dioxide is slightly soluble in solution

2. Oxygen is less soluble than carbon dioxide

3. Nitrogen is nearly insoluble

2. Gases diffuse from areas of higher concentration to areas of lower concentration

3. Oxygen diffuses from the alveoli to the pulmonary capillaries

4. Carbon dioxide diffuses from the pulmonary capillaries to the alveoli

5. Direction of diffusion is opposite in the tissues

G. Oxygen Transport

1. Hemoglobin + oxygen =

2. Small amount dissolved in plasma

3. Factors enhancing oxygen release/unloading from hemoglobin

a.

b.

c.

d.

4. Carbon monoxide (CO) binds more strongly to hemoglobin than does oxygen

H. Carbon Dioxide Transport

1. 7% is dissolved in the plasma

2. 23% is carried as carbaminohemoglobin

3. The majority (70%) is transported as bicarbonate ions

CO₂ + H₂O --> H₂CO₃ --> H⁺ + HCO₃^-(in the systemic capillaries)

This occurs readily within the RBC’s due to the enzyme carbonic anhydrase

4. Bicarbonate is an important blood buffer

5. Bohr effect -

6. Chloride shift -

IV. Control of Respiration

A. Respiratory Centers of the Brain

1. Respiratory Rhythmicity Center

a. Dorsal respiratory group (contains inspiratory center)

1. Responsible for rhythm of breathing

2. Diaphragm and other inspiratory muscles

b. Ventral respiratory group (contains expiratory center)

1. Neurons involved in more forceful breathing

2. Inactive during normal breathing

2. The Pons

a. Responsible for the rate of breathing

b. Regulate duration of inspiratory bursts

c. Increase in breathing rate

B. Reflex Control of Respiration

A. Chemoreceptor reflexes

a. Stimulus =

b. Result =

c. CO₂ levels increase

1. CO₂ + H₂O --> H₂CO₃

2. H₂CO₃ --> H⁺ + HCO₃^-

d. Respiration drive and PCO₂

2. Mechanoreceptor Reflexes

a. Hering-Breuer reflex (inflation reflex)

1. Stretch receptors of visceral pleura, bronchioles and alveoli

2. Impulse along vagus nerve to medulla oblongata

b. Deflation reflex

c. Carotid and Aortic Bodies

V. Homeostatic Imbalances of the Respiratory System

A. Chronic Obstructive Pulmonary Disease (COPD’s) - a group of lung disorders characterized by increased airway resistance due to narrowed lumens

B. Bronchiole Asthma - allergy-induced asthma

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Last Updated 03/04/08