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Chapter 24

BISC 3221 Chapter Notes - Chapter 24: Mechanoreceptor, Phospholipid, Submucosa

Biological Sciences
Course Code
BISC 3221
Craig Frank

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Chapter 24: The Respiratory System
24.1 An Overview of the Respiratory System and Respiratory Tract
Respiratory system: nose + nasal cavity + sinuses + pharynx + larynx + trachea + smaller
conducting passageways
o Includes respiratory tract and associated tissues/organs/support structures
Upper respiratory system: nose + nasal cavity + paranasal sinuses + pharynx
o Condition air (warm, filter, humidify) to protect more delicate portion of tract
Lower respiratory system: larynx + trachea + bronchi + lungs
Functions of the Respiratory System
Provide area for gas exchange between air and circulating blood
Move air to/from exchange surfaces of lungs
Protect respiratory surfaces from dehydration, temp changes, environmental varation
Defend respiratory system + other tissues from pathogen invasion
Produce sounds for speaking/singing/nonverbal communication
Regulate blood volume, blood pressure, body fluid pH
Respiratory tract: airways that carry air to/from gas exchange surfaces
o Conducting portion: from entrance to smallest bronchioles
o Respiratory portion: respiratory bronchioles + alveoli
The Respiratory Epithelium
Pseudostratified ciliated columnar epithelium with many mucous cells
Lines the entire respiratory tract EXCEPT FOR parts of pharynx, smallest conducting passages,
o Parts of pharynx are lined by stratified squamous epithelium to protect it from
abrasion/chemical attack
Cilia in nasal cavity sweep microorganisms/debris trapped in mucous towards pharynx for
In lower portions of respiratory tract, cilia beat towards pharynx
Respiratory defense system = respiratory filtration mechanisms
o All particles larger than 10 micrometers are removed in nasal cavity by vibrissae
o Small particles are trapped by mucous or pharynx secretions
o Exposure to unpleasant stimuli increases mucous production
Filtration, warming, humidification of inhaled air occur throughout conducting portion of
respiratory system but biggest changes occur in nasal cavity; breathing through mouth doesn’t
have this
24.2 The Upper Respiratory System
The Nose and Nasal Cavity
Nose is primary passageway for entering air
Air enters though external nares which open into nasal cavity
Nasal vestibule: portion of cavity enclosed by flexible tissues of nose, supported by thin
cartilages, contain coarse hairs to trap large particles

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Nasal septum: separates right and left portions of nasal cavity; hyaline cartilage, supports dorsum
(bridge) and apex (tip) of nose
Mucous produced in paranasal sinuses
Olfactory region contains areas lined by olfactory epithelium: interior surface of cribriform plate,
superior nasal conchae of ethmoid, superior portion of nasal septum
Air flows between adjacent conchae through superior middle or inferior meatuses to reach
internal nares
o Meatuses are narrow grooves, creates air turbulence to trap particles
Hard palate: formed by maxillary and palatine bones, base of nasal cavity
Soft palate: marks boundary between superior nasopharynx and rest of pharynx
The Pharynx
Shared by respiratory and digestive tracts
Extends between internal nares and entrances to trachea/esophagus
3 regions; nasopharynx, oropharynx, laryngopharynx
The Nasopharynx
o Superior portion of pharynx, connected to nasal cavity by internal nares
o Separated from oral cavity by soft palate
o Lined by respiratory epithelium, lateral walls contain auditory tube openings
The Oropharynx
o Between soft palate and base of tongue at level of hyoid bone
o Connected to posterior of oral cavity, posterior and inferior portions of nasopharynx
o Epithelium changes to nonkeratinized stratified squamous epithelium
o Posterior margin of soft palate supports uvula and pharyngeal arches
o Palatine tonsil on either side between anterior palatoglossal arch and posterior
palatopharyngeal arch
o Fauces: passageway between oral cavity and oropharynx
The Laryngopharynx
o Region of pharynx between hyoid bone and entrance to esophagus
o Lined by nonkeratinized stratified squamous epithelium
24.3 The Lower Respiratory System
The Larynx
Glottis: narrow opening between pharynx and larynx
Larynx: begins at vertebra C3 or C4 and ends at C7
Cartilages of the Larynx
o 3 unpaired cartilages: thyroid, cricoid, epiglottis
o Thyroid and cricoid cartilages are hylaline; epiglottis is elastic
The Thyroid Cartilage
o Largest laryngeal cartilage AKA Adam’s apple
o Incomplete posteriorly
o Laryngeal prominence: thick ridge on anterior surface
o Inferior surface articulates with cricoid; superior surface has ligaments to epiglottis
The Cricoid Cartilage
o Inferior to thyroid cartilage
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