Structures
Function of the Respiratory System
 Filters, warms, and humidifies the air we breathe
 Ensures that oxygen is supplied TO…
…and carbon dioxide is removed FROM…
the body’s cells
 Influences speech production
 Makes olfaction possible
Structures
Divided into Upper & Lower
Respiratory Tracts
Contains Respiratory mucosa:
 Specialized mucous membrane
that lines the respiratory tract
 Secretes MUCUS
 air purification mechanism.
 traps irritants such as dust and pollen
 Cilia on mucosal cells beat upward,
moving mucus to pharynx for
removal.
Histology: Pseudostratified Ciliated Columnar Epithelium
with Goblet Cells (secrete mucus)
UPPER RESPIRATORY TRACT
 Nose
 Nasal cavity
 Pharynx
 Naso Oro Laryngo Larynx
 Mouth
 Eustachian tubes
Nose
 Air enters through external nares (nostrils)
 Nasal septum separates interior of nose into two
cavities (composed of ethmoid, quadrangular cartilage,
vomer bone)
 Nose warms and moistens inhaled air, contains organs
of smell
Nasal Cavity
 Lined by bone, mucous membrane
 Ethmoid
 Maxilla
 Nasal bones
 Warms, moistens, cleans air
 Cilia trap microorganisms, materials  digestive
system
 Turbinates/conchae direct air to olfactory gland
Sinuses
 Frontal, maxillary, sphenoidal, ethmoidal sinuses
drain into the nose
 Provide resonance for speech
 Can become inflamed (sinusitis)
CT Scans
Normal vs. Chronic Sinusitis
Pharynx
1. Nasopharynx
- Mucous-secreting
- Eustachian tubes
- Adenoids
2. Oropharynx
- Digestive component
- Tonsils
3. Laryngopharynx 
larynx
Laryngopharynx
Larynx (voice box)
 Composed mainly of cartilage
 Bound by ligaments and muscles
 Contains vocal cords that stretch across from arytenoid
to cricoid cartilages
 Changes in tension changes pitch
 Superior/anterior to larynx= epiglottis (closes off larynx
during swallowing)
 Anterior larynx=thyroid cartilage

(largest, contains Adam’s apple)
 Inferior larynx=cricoid cartilage
 Hyoid bone located here
Pathology of the Larynx
Vascular polyp w/ varices
Laryngocele
Leukoplakia &
underlying
carcinoma
LOWER RESPIRATORY TRACT
 Located within the thoracic cavity
 Includes the
 Trachea
 Bronchi
 Lungs




Bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
Trachea
 4 ½ inches long, from larynx
to bronchi
 Held open by 15-20 Cshaped cartilaginous rings
 Posterior muscle
 Obstruction can cause death
w/in minutes
 Ciliated to move
mucus out
- Smoking affects these
1 - Vocal cords
2 - Thyroid cartilage
3 - Cricoid cartilage
4 - Tracheal cartileges
5 - Balloon cuff
Remainder of Lower Respiratory Tract
 R & L bronchi 
 Contain cartilage, smooth
muscle
 R is wider, shorter, more
vertical
 Divide into secondary and
tertiary bronchi 
 Bronchioles (terminal and
respiratory) 
 Lungs (alveolar ducts and
sacs)
Bronchi  Bronchioles  Lungs
 Terminal bronchioles can dilate, constrict
 Respiratory bronchioles split into
 2-11 alveolar ducts each 
 5-6 alveolar sacs each (look like bunches of grapes)
Alveolar Ducts  Alveolar Sacs  Alveoli
 Alveolar sacs are microscopic and come in clusters
 Made up of alveoli:
 site of gas exchange b/w air and blood
 Coated with surfactant (reduces surface tension,
prevents them from collapsing)
General Structure/Location of the Lungs
 Lungs: R—3 lobes, L—2 lobes (divide into lobules)
 Apex: under clavicle
 Base: above diaphragm
 Heart in cardiac notch
Lobes and Lobules
 Functional and structural:
 Conducting portion


Terminal bronchioles
Clara cells – remove toxins
 Type 1 alveolar cells – gas exchange
 Type II alveolar cells – secrete surfactant
 Surfactant – reduces surface tension of lungs, allows easier
expansion; prevents collapse of alveoli
 Respiratory portion

Gas exchange occurs here
X-Ray: Right apex tumor
More on Lung Structure
 Pleura: thin, moist, slippery
(serous) membrane
 Visceral pleura: covers the outer
surface of the lungs
 Parietal pleura: lines the inner
surface of the rib cage
 Produces pleural fluid-intrapleural
space must remain moist
Pathology: Pleurisy (pleuritis) –
painful inflammation of the pleura
Collapsed Lung
 A.k.a. = pneumothorax
 Caused when atmospheric
pressure enters the thoracic
cavity
 Normally a partial vacuum
between ribcage and lungs
 Trauma introduces air, which
removes “suction” that keeps
lungs inflated
Repaired by: chest tube