this lecture describe the anatomy of respiratory system including upper and lower tracts and anatomical features of each organ such as nose, nasal cavity, larynx, pharynx, trachea, and lung.

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2. Chapter 3
anatomy of respiratory system
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Identify the structures of the respiratory system, and describe its
major anatomical features
Distinguish between upper and lower respiratory tract organs
anatomy
Distinguish between the conducting portion and respiratory
portion of the respiratory tract.

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Respiratory tract—Branching passageway, carries air to/from gas
exchange surfaces of the lungs.
2 divisions of respiratory tract:
1. Conducting portion—Nasal cavity to larger bronchioles
2. Respiratory portion—Smallest bronchioles to alveoli – Where
gas exchange occurs

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Upper respiratory system
Upper respiratory tract
• Filters, warms, and humidifies incoming air
• Protects delicate lower tract
• Reabsorbs heat and water in outgoing air

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Lower respiratory system
Lower respiratory tract
• Conducts air to and from gas exchange surfaces

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Anatomical components of the
respiratory system

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The upper respiratory system includes the
nose, nasal cavity, paranasal sinuses, and
pharynx
Nose is primary route for air entering
respiratory system:
Dorsum of nose (bridge) formed by two
nasal bones Supported by hyaline
cartilage.
Nasal cartilages—small, elastic cartilages
extending laterally from bridge; help keep
nostrils open.
Nostrils (external nares) are paired
openings into nasal cavity.

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Structures of the nasal cavity
Superior, middle, inferior nasal conchae (bones)
Superior, middle, and inferior nasal meatuses:
• Passages between nasal conchae
• Swirl incoming air to trap small particles
• Moves chemicals to olfactory receptors
• Warms/humidifies air

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Paranasal sinuses
Frontal sinus, ethmoidal air cells, maxillary sinus,
sphenoidal sinus
Mucus secreted by sinuses:
moistens/cleans nasal cavity surfaces;
drains (with tears) through
nasolacrimal duct.
Nasal septum—formed by:
• vomer
• Perpendicular plate of ethmoid

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Pharynx
shared by respiratory and digestive systems:
1. Nasopharynx—superior part; to soft palate
• Has pharyngeal opening of the auditory tube
2. Oropharynx—soft palate to base of tongue
• Stratified squamous epithelium
3. Laryngopharynx—hyoid to larynx

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Larynx
Cartilaginous tube; surrounds/protects glottis (“voice
box”)
Three large cartilages:
• epiglottis,
• thyroid cartilage,
• cricoid cartilage

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Larynx
Large laryngeal cartilages
1. Epiglottis:
• projects superior to glottis; forms lid over it.
• Swallowing—larynx elevates; epiglottis folds back
over glottis; blocks entry into respiratory tract

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Larynx
Large laryngeal cartilages
2. Thyroid cartilage (thyroid; shield shaped)
– Prominent anterior surface is laryngeal
prominence
(Adam’s apple)
– Thyrohyoid ligament attaches it to hyoid bone;
Other ligaments attach it to epiglottis and smaller
cartilages

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Larynx
Large laryngeal cartilages
3- Cricoid cartilage (ring shaped)
– Forms complete ring around larynx
– With thyroid cartilage,
protects glottis and larynx;
provides attachment for
laryngeal muscles/ligaments

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Larynx
Small paired laryngeal cartilages
1. Cuneiform cartilages
within folds of tissue between
each arytenoid cartilage and the epiglottis
2. Corniculate cartilages
articulate with arytenoid cartilages
Work with the arytenoid to open/close the glottis
3. Arytenoid (ladle–shaped) cartilages
articulate with superior surface of cricoid cartilage

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Anterior, sagittal, and posterior views of
the larynx

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Larynx
Glottis
where air passes through larynx
Made of vocal folds and rima glottidis
(opening between folds)
Vocal folds
• tissue folds that contain vocal
ligaments
• Vibrations produce sound waves
• Opened/closed by rotation of
arytenoid cartilages
• Also known as the vocal cords

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The trachea, bronchi, and
bronchial branches
Trachea (windpipe)
• Tough, flexible tube
• starts at C6 and ends at T5 by
branching into bronchi
• Has 15–20 C-shaped tracheal
cartilages
• Prevent collapse and overexpansion

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The trachea, bronchi, and
bronchial branches
Right and left main bronchi
• Go to lungs
• Right bronchus wider than left and
at a steeper angle— foreign objects
in trachea often go into it

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The trachea, bronchi, and
bronchial branches

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The trachea, bronchi, and
bronchial branches
Bronchioles
No cartilage; thick smooth muscle
Sympathetic nervous system causes
bronchodilation
• increases airflow
Parasympathetic nervous system
causes bronchoconstriction
• Decreases airflow

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The trachea, bronchi, and
bronchial branches
Bronchioles
Extreme bronchoconstriction can
occur during allergic reactions
such as asthma
Terminal bronchioles lead to
pulmonary lobules (gas exchange)
Respiratory bronchioles are
last division

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The lungs and
Bronchopulmonary segments
Each lung divided into lobes
• Right lung (3):
superior lobe, middle lobe, inferior lobe
• Left lung (2):
superior lobe and inferior lobe
Each lobe has multiple bronchopulmonary segments Bronchial tree
refers to all levels of bronchi through bronchioles
Each segmental bronchus ultimately supplies a bronchopulmonary
segment

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The lungs and
Bronchopulmonary segments

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Anterior view of human lungs

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The lungs and
Bronchopulmonary segments
Each lung is cone shaped and divided into lobes by deep fissures:
Right lung
• horizontal fissure
between superior/middle lobes;
• oblique fissure
between middle/inferior lobes
Left lung
• oblique fissure
between superior/inferior lobes

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The lungs and
Bronchopulmonary segments
• Apex (tip) extends to superior border of first rib
• Concave base rests on diaphragm
• Cardiac notch—left lung; accommodates pericardium/heart

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The lungs and
Bronchopulmonary segments
Root of the lung—dense connective tissue; fixes positions of
bronchi, major nerves, blood vessels, and lymphatics
Hilum is a medial depression on each lung
• Allows passage of main bronchus,
pulmonary vessels, nerves, lymphatics
Grooves on surface of lungs
mark positions of great vessels

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Pulmonary lobules contain
alveoli
Segmental bronchus
supplies a bronchopulmonary segment
Bronchioles
branch into terminal bronchioles
in each bronchopulmonary segment
Each terminal bronchiole
supplies a single pulmonary lobule
Terminal bronchioles
branch to respiratory bronchioles
Respiratory bronchioles
lead to alveolar ducts, which lead to alveolar sacs (alveolar saccules)

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Pulmonary lobules contain
alveoli
Pulmonary alveoli (singular, alveolus)
• ~150 million alveoli per lung;
give lungs an open, spongy appearance.
• Surrounded by extensive
capillary network for gas exchange

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Pulmonary lobules contain
alveoli
Pulmonary alveoli (singular, alveolus)
Surrounded by elastic fibers—
expansion/recoil aids air movement
Each alveolar duct ends in clusters of
alveoli (alveolar sacs, or alveolar
saccules)

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Divisions of the bronchial tree

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Pulmonary lobules and the
respiratory membrane
Pleurae
serous membrane sacs surrounding the
lungs
• Visceral pleura covers outer surfaces of
lungs
• Parietal pleura covers inner surface of
thoracic wall;
extends over diaphragm and mediastinum

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Pulmonary lobules and the
respiratory membrane
Pleurae
Pleural cavity
• potential space between visceral and
parietal layers of pleural sac
• Contains pleural fluid—reduces friction

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Pulmonary lobules and the
respiratory membrane
Pleurae
Pleural cavity
• potential space between visceral and
parietal layers of pleural sac
• Contains pleural fluid—reduces friction

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Respiratory muscles
May be involved with inhalation (inspiratory muscles) or exhalation
(expiratory muscles)
Quiet breathing:
• Active inhalation via inspiratory muscles
• Passive exhalation—done by elastic recoil of tissues and gravity, not
by muscle action
Expiratory muscles are used when needed to force exhalation
Primary respiratory muscles—involved in inhalation
Accessory respiratory muscles—assist primary inspiratory muscles or
provide active exhalation.

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Respiratory muscles
Inspiratory muscles
Primary inspiratory muscles—diaphragm, external
intercostals:
1- Diaphragm does ~75 percent of movement
– Flattens floor of thoracic cavity
2- External intercostals do ~25 percent of movement;
-elevate ribs

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Respiratory muscles
Inspiratory muscles
Accessory inspiratory muscles:
• Sternocleidomastoid
• Scalenes
• Pectoralis minor
• Serratus anterior
• Increase speed/amount of rib movement to move
more air when needed (tissue oxygen demands not
met by primary inspiratory muscles)

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Anterior view of primary and accessory
inspiratory muscles

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Lateral view of inspiratory muscles

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Respiratory muscles
Expiratory muscles
There are no primary expiratory muscles:
exhalation usually is passive process done by
elastic recoil and gravity

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Respiratory muscles
Accessory expiratory muscles
• Internal intercostals, transversus thoracis, external
• oblique, internal oblique, rectus abdominis
• Internal intercostals and transversus thoracis
depress ribs
• Abdominal muscles push diaphragm upward
• Decrease thoracic cavity volume quickly
• Allow greater pressure change and faster airflow out
• of lungs

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Anterior view of accessory
expiratory muscles

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Lateral view of accessory
expiratory muscles

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