D’YOUVILLE COLLEGE
BIOLOGY 108/508 - HUMAN ANATOMY & PHYSIOLOGY II
LECTURE # 9
RESPIRATORY SYSTEM I
INTRODUCTION & ANATOMY
1.
General Organization (fig. 22 - 1 & table 22 - 1):
a. Upper Respiratory Tract: parts outside thorax
b. Lower Respiratory Tract: intrathoracic, “bronchial tree”, mostly in lungs
c. Lungs: enclosed by pleura (parietal and visceral); expand and contract with
movements of diaphragm
2.
Anatomy:
a. Nose (fig. 22 - 3): right & left nasal cavities separated by median nasal
septum
- external nares open into vestibule (skin); olfactory cells at summit
- conchae of lateral wall (ciliated mucosa) define meatuses
internal nares (choanae) open into nasopharynx
- paranasal sinuses (from frontal, maxillary, ethmoid and sphenoid bones)
and the nasolacrimal duct empty into meatuses
-functions:
- air conditioning (warming, moisturizing, cleansing)
- smelling (olfactory apparatus)
- resonating chamber for vocalization
- drainage of sinus fluids and tears
b. Pharynx(fig. 22 - 3): (see digestive organs); pressure equalization for middle
ear; resonating chamber for vocalization; protected by ring of tonsils
c. Larynx (“voice box”) (fig. 22 - 4):
- 3 major cartilages (thyroid, cricoid, epiglottis); + arytenoids
- vocal folds: upper, vestibular folds (false vocal cords) and lower,
ventricular folds (true vocal cords)(fig. 22 - 5)
- true vocal cords = containing elastic connective tissue extending from
arytenoid cartilages posteriorly to thyroid cartilage anteriorly; control opening of
glottis and pitch of voice
d. Trachea (“windpipe”) (fig. 22 - 6):
- respiratory mucosa (sticky mucous blanket + ciliated epithelium =
“respiratory escalator”)
- collapse of trachea prevented by C-shaped rings of cartilage
- branches inferiorly to left and right primary bronchi
Bio 108/508
lec. 9- p. 2
e. Bronchial Tree and Lungs (figs. 22 - 7, 22 - 8, & 22 - 9):
- primary bronchi (one for each lung) branch to secondary bronchi (one for
each lobe of lung {three on right, two on left})
- bronchi possess reinforcing cartilage rings to prevent collapse
- bronchioles are smallest branches of bronchial tree; walls have smooth
muscle (no cartilage); terminal bronchioles represent final conducting passages;
respiratory bronchioles are part of respiratory unit
respiratory unit: alveoli (like a bunch of bubbles, surrounded by capillaries for
exchange with blood)
- tendency for collapse: elastic connective tissue within lungs
- internal film of fluid in respiratory units presents strong surface tension
(opposed by production of pulmonary surfactant) (pages 815 & 823)
- collapse tendency offset by pleural fluid in pleural cavities (lubricant and
adhesive properties) (fig. 22 - 10c)
3.
Physiology of Respiration: delivery of O2 to tissues (4 processes) (page 805):
1. Pulmonary Ventilation: breathing movements
2. External Respiration: alveolar diffusion exchanges gases with blood
3. Gas Transport: uptake and release of oxygen by the red cells
4. Cellular Respiration: uptake & utilization of oxygen by cells of the body,
e.g., in glycolysis, Krebs cycle, fatty acid cycle, etc. & discharge of carbon dioxide
4.
Pulmonary Ventilation (fig. 22 - 13):
- pressurization/depressurization cycle - bellows action of diaphragm:
- inspiration: diaphragm contracts, flattens to expand pleural cavities; lungs
expand and fill with air
- expiration: passive recoil of lungs and rib cage (for normal quiet breathing);
auxiliary muscles assist in forcible ventilation
- several pulmonary volumes associated with ventilation (fig. 22 - 16):
- tidal volume: quiet breathing (approx. 500 ml.)
- inspiratory reserve volume: forced inspiration (approx. 2500 ml.)
- expiratory reserve volume: forced expiration (approx. 1200 ml.)
- vital capacity: maximal exchange between lungs & outside air (4200 ml.)
- inspiratory capacity: inspiratory reserve volume + tidal volume
- residual volume: left in lungs after forcible expiration (approx. 1200 ml.)
- total lung capacity: vital capacity + residual volume
- minute respiratory volume: volume of air exchanged per minute;
respiratory frequency times tidal volume (approx. 6000 ml./min.)
- anatomic dead space: air not available for gas exchange with blood;
volume of conducting airways (approx. 150 ml.)