Chapter 13, Respiratory System, Part A

Chapter 13
The Respiratory System
1. Organs of the system
a. Nose
b. Pharynx
c. Larynx
d. Trachea
e. Bronchi
f. Lungs/alveoli(us)
2. Functions of the system
a. Gas exchange between blood and external environment
- Occurs in the alveoli of the lungs
- Passageways to the lungs purify, humidify, and warm the incoming air
b. Specific functions in parts of the system:
3. Nose
a. External: only externally visible part of the respiratory system
b. Nares: air enters the nose through the external nostrils (nares)
- Interior of the nose consists of a nasal cavity divided by a nasal septum
c. Nasal cavity
i. Olfactory receptors are located in the mucosa on the superior surface
ii. Respiratory mucosa lines the rest of the cavity:
• Moisten air
• Trap incoming foreign particles
iii. Conchae: projections in the lateral wall
1. Increase surface area and air turbulence within the nasal cavity
iv. Palate: Anterior hard palate (bone); Posterior soft palate (muscle)
v. Paranasal Sinuses
1. Cavities within bones surrounding the nasal cavity are called sinuses
2. Functions
• Lighten the skull
• Act as resonance chambers for speech
• Produce mucus that drains into the nasal cavity
3. Sinuses are located in the following bones:
• Frontal bone
• Sphenoid bone
• Ethmoid bone
• Maxillary bone

4. Pharynx (Throat) muscular passage from nasal cavity to larynx
a. Nasopharynx- superior region behind nasal cavity
b. Oropharynx- middle region behind the mouth (passageway for air and food)
c. Laryngopharynx- inferior region attached to larynx (passageway for air and food)
d. Eustacean = auditory=pharyngotympanic tubes
e. Tonsils
i. Pharyngeal
ii. Palatine
iii. Lingual

5. Larynx (voice box)
a. Routes air and food into proper channels
b. Plays a role in speech
c. Made of eight rigid hyaline cartilage (epiglottis)
d. Cartilage
i. Thyroid: largest of the hyaline cartilages; protrudes anteriorly (Adam’s apple)
ii. Epiglottis – protects the superior opening of the larynx
• Routes food to the esophagus and air toward the trachea
• When swallowing, the epiglottis rises and forms a lid over the opening of the larynx
e. Vocal folds (true vocal cords)
i. Vibrate with expelled air to create sound (speech)
ii. Glottis- opening between vocal cords
6. Trachea
a. Four inches long tube connects larynx with bronchi
b. Walls are reinforced with c-shaped hyaline cartilage
c. Ciliated mucosa lines the trachea
i. Beat continuously in the opposite direction of incoming air
ii. Expel mucus loaded with dust and other debris away from lungs
7. Main bronchi(us)
a. Formed by division of the trachea
b. Enters the lung at the hilum (medial depression)
c. Right bronchus is wider, shorter and straighter than left
d. Bronchi subdivide into smaller and smaller branches
8. Lungs
a. Anatomy
i. Location: occupies most of the thoracic cavity
ii. The heart occupies central portion (middle wall) called mediastinum
iii. Apex is near the clavicle (superior portion)
iv. Base rests on the diaphragm (inferior portion)
v. Lobes: each lung is divided into lobes by fissures:
1. Right- three lobes
2. Left- two lobes
b. Coverings
i. Serosa covers the outer surface of the lungs:
ii. Pulmonary (visceral) pleura covers the lung surface
iii. Parietal pleura lines the walls of the thoracic cavity
iv. Pleural fluid fills the area between layers of pleura to allow gliding
v. These two pleural layers resist being pulled apart
c. Bronchial tree: all but the smallest of these passageways have reinforcing cartilage in their walls
i. Bronchi divisions
1. Primary bronchi
2. Secondary bronchi
3. Tertiary bronchi
4. Bronchioles
5. Terminal bronchioles
ii. Respiratory zone
1. Respiratory bronchioles
2. Alveolar ducts
3. Alveolar sacs
4. Alveoli(us) (airs sacs)
• Site of gas exchange= alveoli only
i. Respiratory membrane = air/blood barrier
i. Alveolar pores connect neighboring air sacs
ii. Epithelium: thin squamous epithelial layer lines alveolar walls
iii. Blood capillaries: pulmonary capillaries cover external surfaces of alveoli
iv. On one side of the membrane is air and on the other side is blood flowing past
ii. Gas exchange – the ultimate goal
9. Gas exchange via diffusion only
a. Oxygen
b. Carbon dioxide
c. Macrophages
d. Surfactant
10. Events of respiration
a. Breathing
b. External respiration
i. Oxygen
ii. Carbon dioxide
c. Respiratory gas transport
d. Internal respiration