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MA 116 – Clinical Pathology II
Respiratory System – Study Guide
Spring 2008
1) 3 functions of nasal mucosa
a) Warm inhaled air
b) Humidify inhaled air
c) Trap dust and microorganisms on mucus & sweep to pharynx by cilia
2) Pleural membranes & serous fluid
a) Parietal pleura
i. Lines chest wall of thoracic cavity
b) Visceral pleura
i. Covers lungs
c) Serous fluid
i. Both parietal & visceral pleura are serous membranes
ii. Serous fluid prevents friction between the membranes
iii. Keep membranes together during breathing (intrapleural pressure)
3) Alveoli & pulmonary capillaries
a) Made of simple squamous epithelium (alveolar type I cells)
i. Thin single layer of cells permits diffusion of gases
b) Pulmonary surfactant
i. Produced by alveolar type II cells
ii. Surfactant mixes w/ tissue fluid in alveoli —› decreases surface
tension —› permits inflation of alveoli
4) Respiratory muscles and pressures
a) Diaphragm
i. Inhalation = dome-shaped; when contracts, flattens and
pulls/expands chest cavity downward
ii. Exhalation = relaxes upward, making chest cavity smaller
b) External intercostal muscles
i. Inhalation = contract to pull ribs upward & outward/expands chest
cavity
ii. Exhalation = relax making chest cavity smaller
c) Internal intercostal & abdominal muscles
i. Contract when forceful/active exhalation is needed
ii. Normal exhalation is a passive process/inhalation is active
d) Atmospheric pressure
i. The pressure of the air around us (760 mmHg @ sea level)
e) Intrapulmonic pressure
i. Pressure w/in bronchial tree & alveoli
ii. Fluctuates above & below atmospheric pressure during breathing
5) Partial pressure (P) of O2 & CO2 in external respiration
a) O2 diffuses from air in alveoli (high PO2) to blood in pulmonary
capillaries (low PO2)
b) CO2 diffuses from blood in pulmonary capillaries (high PCO2) to air in
alveoli (low PCO 2)
6) Partial pressure (P) of O2 & CO2 in internal respiration
a) O2 diffuses from blood in systemic capillaries (high PO2) to body cells &
tissue fluids (low PO2)
b) CO2 diffuses from body cells & tissue fluids (high PCO2) to blood in
systemic capillaries (low PCO 2)
7) Oxygen transport in blood
a) Red blood cells – transport O2
b) Hemoglobin – protein in RBCs/erythrocytes that carry O2
c) Iron (Fe) – mineral that carries O2 in hemoglobin
d) 3 factors that increase O2 release in tissues
i. Low O2 concentration
ii. High PCO2 (lower pH)
iii. High temperature
8) Carbon dioxide transport in blood
a) Most transported in plasma in form of bicarbonate ions
b) Hemoglobin acts as buffer to keep RBCs from becoming to acidic as
bicarbonate ions diffuse out of cell leaving hydrogen ions (H+)
9) Nervous regulation of respiration
a) Medulla contains breathing centers (inspiration & expiration centers)
b) Impulses from inspiration center cause respiratory muscle contraction
c) Baroreceptors detect stretching in lung tissue send impulses to medulla;
Hering-Breur inflation reflex = prevents over inflation of lungs
d) Expiration center stimulated when forceful exhalation needed
e) Pons works with the medulla to produce normal breathing rhythm, both
are located in brain stem. Pons helps with prolonged inhalations and
exhalation
f) Hypothalamus influences breathing in emotional situations; cerebral
cortex permits voluntary control of breathing
g) Coughing & sneezing reflexes located in medulla; these reflexes remove
irritants from upper respiratory tract
10) Lung Capacity
a) Tidal volume = amount of air in one normal inhalation & exhalation
b) Minute respiratory volume = amount of air inhaled & exhaled in 1 min.
c) Inspiratory reserve = amount of air that can be taken in w/ the deepest
possible breath
d) Expiratory reserve = amount of air that can be expelled w/ the most
forceful expiration
e) Vital capacity = sum of tidal volume, inspiratory reserve, and expiratory
reserve
f) Residual air = amount of air that remain in the lungs at all time