Chapter 23 The Respiratory System. Copyright © John Wiley & Sons, Inc. All rights reserved. Upper...

Chapter 23

The Respiratory

System

Copyright © John Wiley & Sons, Inc. All rights reserved.

Upper respiratory tract

Lower respiratory tract

Respiratory System Anatomy

Structurally, the respiratory system is

divided into upper and lower divisions or

tracts.

The upper respiratory tract

consists of the nose, pharynx

and associated structures.

The lower respiratory tract

consists of the larynx,

trachea, bronchi and

lungs.



Functionally, the respiratory system is

divided into the conducting zone and the

respiratory zone.

The conducting zone is involved with

bringing air to the site of external

respiration and consists of the nose,

pharynx, larynx, trachea, bronchi,

bronchioles and terminal

bronchioles.

The respiratory zone is the main site of

gas exchange and consists of the

respiratory bronchioles, alveolar

ducts, alveolar sacs, and alveoli.


Air passing through the respiratory

tract traverses the:

Nasal cavity

Pharynx

Larynx

Trachea

Primary (1o) bronchi

Secondary (2o) bronchi

Tertiary (3o) bronchi

Bronchioles

Alveoli (150 million/lung)



The external nose is

visible on the face.

It consists of:

a supporting bony

framework (frontal

bone, nasal bones,

and maxillae) and a

cartilaginous

framework of hyaline

cartilage

The Nose


The Nasal cavity

Lies in and posterior to the

external nose

Is divided by a midline

nasal septum

Formed by the

perpedicular plate of

ethmoid, & the vomer

posteriorly and the septal

cartilage anteriorly

It opens posteriorly into the

nasopharynx

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Three nasal conchae (or

turbinates) protrude medially

from each lateral wall of nasal

cavity

Superior concha

Middle concha

Inferior concha

Increase mucosal surface area & air

turbulence- ensures air contacts

mucosa

Under each nasal concha is an

opening, or meatus, for a duct that

drains secretions of the sinuses and

tears into the nose.

Nasal Cavity- lateral wall


The Nose

Functions:

Providing an airway for respiration

Moistening and warming & filtering inspired

air

Resonation of sound

Olfaction


The Paranasal Sinuses• Mucosa-lined, air-filled spaces found in

five skull bones – the frontal, sphenoid, ethmoid, and paired maxillary bones • Sinuses lighten the skull and help to

warm and moisten the air


The Paranasal Sinuses

Mucosal secretions flows from the sinuses into nasal cavity


The Phrynx

The pharynx is a hollow tube that starts

posterior to the internal nares and descends

to the opening of the larynx in the neck.

It is formed by a complex arrangement of

skeletal muscles that assist in deglutition.

It functions as:

o a passageway for air and food

o a resonating chamber

o a housing for the tonsils


The Pharynx

Nasopharynx

Oropharynx

Laryngopharynx

The pharynx has 3 regions The nasopharynx is separated

from the oropharynx by the hard and soft palate


Lies posterior to the nasal cavity and superior to the level of the soft palateStrictly an air passageLined with psuedostratified columnar epitheliumCloses during swallowing to prevent food from entering the nasal cavityThe pharyngeal tonsil ( adenoids) lies high on the posterior wall Auditory tubes from middle ears open into the lateral walls

The Nasopharynx


Cilia in the upper respiratory tract move

mucous and trapped particles down toward the

pharynx.

(Cilia in the lower respiratory tract move them

up toward the larynx.)

Respiratory Lining


The PharynxThe oropharynx & laryngopharynx are both

common passages for food and air & are lined by

stratified squamous epithelium

The oropharynx lies posterior to the oral cavity

&

opens into the oral cavity via the fauces

The palatine tonsils lie in the lateral walls of the

fauces (those usually taken in a tonsillectomy)

and small lingual tonsil at the base of the

tongue

The laryngopharynx lies posterior to the upright

epiglottis

Leads into the larynx & the esophagus


The Pharynx


The Larynx

The larynx, composed of 9 pieces of cartilage,

forms a short passageway connecting the

laryngopharynx with the trachea (the

“windpipe”).

The thyroid cartilage (the large

“Adam’s apple”) and the one below

it (the cricoid cartilage) are

landmarks for making an

emergency airway (called a

cricothyrotomy).Anterior view of the larynx


The Larynx

9 Cartilages of the larynx

Epiglottis – elastic cartilage that covers the

glottis during swallowing

Thyroid cartilage- hyaline cartilage with a

midline laryngeal prominence (Adam’s apple)

Cricoid cartilage - hyaline cartilage

Three pairs of small arytenoid, corniculate, &

cuneiform cartilages


The epiglottis is a flap of elastic cartilage

covered with a mucus membrane, attached to

the root of the tongue.

The epiglottis guards the entrance of the

glottis, the opening between the vocal folds.

o For breathing, it is held

anteriorly, then pulled back-

ward to close off the glottic

opening during

swallowing.

The Larynx


The Larynx

The mucous membrane of the larynx forms two

pairs of folds:

The superior pair are the Ventricular folds ( false

vocal cords) -also called vestibular folds

The space between the ventricular folds is the

rima vestibuli

The inferior pair are the vocal folds ( true vocal

cords)

The space between the vocal folds ( true vocal

cords) is the rima glottidis

True vocal cords & the opening between them form the

glottis


The Larynx

The functions of the larynx are:

To provide an airway

To route air and food into the proper channels

To function in voice production- True vocal cords

vibrate to produce sound as air passes

False vocal cords have no part in sound production;

help close glottis during swallowing

Valsalva’s maneuver- by closing the glottis the

larynx is closed during certain abdominal

straining conditions to prevent exhalation


Upper respiratory tract

Lower respiratory tract

Lower Respiratory Tract

As air passes from the laryngopharynx into the

larynx, it leaves the upper respiratory tract

and enters the lower respiratory tract.

Air passing through the

respiratory tract

Nasal cavity

Pharynx

Larynx

Trachea

Primary bronchi

Secondary bronchi

Tertiary bronchi

Bronchioles

Alveoli (150

million/lung)


The Trachea

The trachea is a semi-rigid pipe made of semi-

circular cartilaginous rings, and located

anterior to the esophagus.

It is about 12 cm long and extends inferior to

larynx into the mediastinum

At the level of carina ( an internal ridge of last

tracheal cartiage) it divides into right and left

primary (1o, “mainstem”) bronchi.

It is composed of 4 layers: the mucosa ( lined

by ciliated respiratory epithelium),

submucosa, hyaline cartilage, and

adventitia


The tracheal cartilage rings are incomplete

posteriorly, facing the esophagus.

Esophageal masses can press into this soft

part of the trachea and make it difficult

to breath, or even

totally obstruct

the airway.

The Trachea


The Bronchi

The right and left primary (1o or “mainstem”)

bronchi emerge from the inferior trachea to go

to the lungs

Right primary bronchus is more vertical

compared to left primary bronchus


The BronchiPrimary bronchi- subdivide into:Secondary bronchi (lobar bronchi), each supplying a lobe of the lungs –two on the left side and three on the right

Subdivide into tertiary bronchi (segmental bronchi)- each supplies one bronchopulmonary segmentThere are upto 10 bronchopulmonary segments in each lung

http://pblnotes.wordpress.com/2011/

http://pblnotes.wordpress.com/2011/


Air passages undergo 23 orders of branchingsBronchioles- smaller than 1mm in diameter- lack cartilageBronchioles divide into terminal bronchioles

A branch of the terminal bronchioles supplies air to a lobule

Terminal bronchioles branch into respiratory bronchioles which now have alveoliRespiratory bronchioles lead to the alveolar ducts which have alveoli

The respiratory bronchioles, alveolar ducts and alveoli form the 'respiratory zone'

Bronchioles


Pulmonary

lobule:

Wrapped in

elastic

C.T., each

pulmonary

lobule contains a

lymphatic vessel,

an

arteriole, a

venule

and a branch of

terminal

bronchiole.

Lung lobule


The bronchi and bronchioles go through

structural changes as they branch and become

smaller.

The mucous membrane changes

The cartilaginous rings become more sparse,

and eventually disappear altogether.

As cartilage decreases, smooth muscle

(under the control of the Autonomic Nervous

System) increases.

o Sympathetic stimulation causes airway

dilation, while parasympathetic

stimulation causes airway constriction.


All the branches from the trachea to the

terminal bronchioles are conducting

airways – they do not

participate in gas

exchange.


Alveoli

Alveoli are the cup-

shaped outpouchings

which participate in gas

exchange

Alveoli make up a large

surface area (750

ft2).

They are lined chiefly by

type I alveolar cells,

simple squamous

epithelium)which allow

for exchange of gases with

the pulmonary capillaries.


Alveoli

Type II cells in the alveoli

secrete a

substance called surfactant

that prevents collapse of the

alveoli

Alveoli macrophages (also

called “dust cells”) engulf and

remove pathogens & debris


Respiratory MembraneThe Respiratory membrane across which diffusion of gases occurs is composed of:

Alveolar lining epitheliumCapillary endotheliumTheir fused basement membranes


Blood Supply to the Lungs

The lungs receive blood via two sets of

arteries

Pulmonary arteries carry deoxygenated

blood from the right heart to the lungs for

oxygenation

Bronchial arteries branch from the aorta

and deliver oxygenated blood to the lungs

primarily perfusing the muscular walls of

the bronchi and bronchioles ( not the

alveoli)


The lungs are divided into lobes by fissures.

The right lung is divided by the oblique

fissure and the horizontal fissure into 3

lobes .

The left lung is divided into

2 lobes by the oblique fissure.

Each lobe receives it own 2o

bronchus that branches into

3o segmental bronchi (which

continue to further divide).

The Lungs


The apex of the lung is superior, and extends

slightly above the clavicles. The base of the

lungs rests on the diaphragm.

The cardiac notch –

in the left lung (the

indentation for the

heart)

• The medial mediastinal surface

has the hilus –

an indentation



The lungs are separated from each other by

the heart and other structures in the

mediastinum.

Each lung is enclosed by a double-layered

pleural membrane.

The parietal pleura line the

walls of the thoracic cavity.

The visceral pleura adhere

tightly to the surface of

the lungs themselves.




On each side of the thorax, a pleural cavity is

formed.

The pleural cavity contains pleural fluid -

reduces friction

The pleura, adherent to the chest wall and to

the lung, produces a mechanical coupling for

the two layers to move together.

Chapter 23 The Respiratory System. Copyright © John Wiley & Sons, Inc. All rights reserved. Upper...

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