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Functions of the respiratory system

-Allows for the exchange of gases (especially O2 and CO2) between the atmosphere and the blood.

Functions of the respiratory system

-Immune functions

Functions of the respiratory system

-Sound production (speech, singing, etc)

Functions of the respiratory system

-Sensation of olfactory stimuli (smell)

Upper respiratory tract epithelia

Mostly lined by pseudostratified, columnar, ciliated epithelia

Upper respiratory tract structures

Nasal cavity

Lower respiratory tract epithelia

-Lined by various kinds of epithelia.
-The trachea, bronchi, and larger bronchioles contain mucus-producing goblet cells.

Lower respiratory tract structures



-Structurally supported by nasal bones and cartilage
-Two nostrils are the entrances to the nasal cavity

Nasal cavity

Lateral walls
Nasal septum

Lateral walls of nasal cavity

-superior, middle, and inferior nasal conchae
-walls beneath each concha is a meatus, or air passageway. (Superior, middle, and inferior meatus).

Roof of nasal cavity

Cribriform plate of ethmoid bone

Nasal septum

-separates the two portions of the nasal cavity

Nasal septum

-Ethmoid and vomer form the posterior part of the septum

Nasal septum

-Septal cartilage forms the anterior part

Floor of nasal cavity

hard palate


-Continuous with the nasal cavity, via ducts.


-Help condition (warm and humidify) inhaled air.


-Give resonance to voice.

Sinuses epithelia

-Lined with pseudostratified, columnar, ciliated epithelia.


-Includes the common passageway for food, drinks and air (what we call the throat).


Tonsils are found in several parts of the pharynx


-Soft palate normally elevates during swallowing, to ensure substances enter pharynx, and prevent substances
from entering nasal cavity.


Pharyngeal wall contains pharyngeal constrictors, the skeletal muscles involved in swallowing


large clusters of lymphatic cells (including lymphocytes).


trap invading organisms, and lymphocytes coordinate immune responses.


therefore help fight upper respiratory infections

Lower respiratory tract structures

Bronchial tree


Cylindrical airway (for air only)

Thyroid cartilage

Largest of nine pieces
V-shaped notch (easily palpated) is above the laryngeal prominence (or adam's apple) of the thyroid cartilage.


Elastic cartilage flap
Moves inferiorly and posteriorly, to block entrance to trachea, during swallowing


aka- voice box

voice box

Vibration of vocal folds produces sound

vocal cords

two ligaments, covered with epithelial tissue, that stretch from anterior to posterior across the

vocal cords

They are at the level of the thyroid cartilage.

vocal cords

They are open during breathing, closed when holding one's
breath, and they vibrate during speech.


Also called windpipe (air only)


Anterior to esophagus


Extends from larynx (superiorly) to the bronchial branch point (inferiorly, at the level of the sternal angle).


Contains 15-20 C-shaped tracheal cartilages

Trachea epithelia

Lining of pseudostratified, columnar, ciliated epithelium, like upper respiratory tract

Tracheal cartilages

connected to each other by annular ligaments

Bronchial tree

Branch about 9 to 12 times in tota linto smaller bronchi
All bronchi have smooth muscle in walls, and cartilage to prevent collapse when pressure is low.

Primary bronchi

1 on left, and 1 on right

secondary bronchi

3 on right, 2 on left

tertiary bronchi

10 on right, 8 to 10 on left


smallest bronchi
less than 1mm in diameter
Bronchioles are small enough that they don't need cartilage to prevent collapse. They have smooth muscle for
regulation of the amount of airflow.

respiratory portion of the respiratory tract

Where gas exchange actually occurs
Respiratory bronchioles and alveoli


Small air-filled structures (about 0.3 mm in diameter)


surrounded by capillaries of the pulmonary circuit


350 million/person


serous membranes of the lungs

Visceral pleura

The inner layer of the serous membrane
Tightly lines the outer surface of the lungs

Parietal pleura

The outer layer of the serous membrane
Lines the inside of the thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the

Pleura Reflection

The two layers of the serous membrane reflect on each other at the hilum (see below).
This arrangement is similar to the serous pericardium of the heart.

pleural cavity

the serous fluid-filled potential space between the two serous layers




Muscles of inhalation enlarge the thoracic cavity.
Because the thoracic cavity is airtight, the lungs also are enlarged. This decreases the pressure inside the lungs,
especially in the alveoli.
This draws air into the alveoli, where gas exchange occurs.


When the muscles relax, the thoracic cavity returns to its resting size, and air is expelled.
In forced exhalation, muscle contraction (including the internal intercostal muscles) leads to a more forceful
decrease in lung volume.

right lung

has 3 lobes

left lung

has 2 lobes


are separted by fissures

Bronchopulmonary segments

10 in right lung
8-10 in left lung

Bronchopulmonary segments

Separate regions of a lung

Bronchopulmonary segments

Each has its own air supply (separate tertiary bronchi)
Each has its own blood supply

Left and right lungs

Left lung smaller, to accommodate larger left ventricle of heart
Note cardiac impression and notch


Medial entrance point for bronchi, blood vessels, nerves, and lymph vessels

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