1. The Respiratory System
Chapter 23
The Respiratory
System

2. 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.
Upper respiratory tract
Lower respiratory tract

3. Respiratory System Anatomy
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.

4. Respiratory System Anatomy
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)

5. The Nose The external nose is visible on the face. It consists of:
a supporting bony frame- work (frontal bone, nasal bones, and maxillae) and a
cartilaginous framework of hyaline cartilage

6. 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 naso- pharynx
 Wikimedia Commons

7. Nasal Cavity- lateral wall
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.

9. The Nose Functions: Providing an airway for respiration
Moistening and warming & filtering inspired air
Resonation of sound
Olfaction

10. 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

11. The Paranasal Sinuses
Mucosal secretions flows from the sinuses into nasal cavity

12. 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:
a passageway for air and food
a resonating chamber
a housing for the tonsils

13. The Pharynx The pharynx has 3 regions The nasopharynx is separated
from the oropharynx by the
hard and soft palate
Nasopharynx
Oropharynx
Laryngopharynx

14. The Nasopharynx
Lies posterior to the nasal cavity and superior to the level of the soft palate
Strictly an air passage
Lined with psuedostratified columnar epithelium
Closes during swallowing to prevent food from entering the nasal cavity
The pharyngeal tonsil ( adenoids) lies high on the posterior wall
Auditory tubes from middle ears open into the lateral walls

15. Respiratory Lining
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.)

16. The Pharynx
The 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

17. The Pharynx

18. 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
A “tracheostomy” is what the ENT surgeons do to make a permanent opening – carefully done in the inferior part of the trachea. A tracheostomy is seldom done as an emergency procedure whereas the cricothyrotomy is. A cricothyrotomy is done by piercing the cricothyroid membrane anteriorly between the thyroid cartilage and the cricoid cartilage. It is quick and “simple”, but doesn’t provide enough stability for a long term “airway”.

19. 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

22. The Larynx
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.
For breathing, it is held
anteriorly, then pulled back-
ward to close off the glottic
opening during
swallowing.

23. 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

25. 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

26. Lower Respiratory Tract
As air passes from the laryngopharynx into the larynx, it leaves the upper respiratory tract and enters the lower respiratory tract.
Upper respiratory tract
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)

27. 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

28. The Trachea
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.

29. 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

30. The Bronchi Primary 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 segment
There are upto 10 bronchopulmonary segments in each lung

31. Bronchioles Air passages undergo 23 orders of branchings
Bronchioles- smaller than 1mm in diameter- lack cartilage
Bronchioles divide into terminal bronchioles
A branch of the terminal bronchioles supplies air to a lobule
Terminal bronchioles branch into respiratory bronchioles which now have alveoli
Respiratory bronchioles lead to the alveolar ducts which have alveoli
The respiratory bronchioles, alveolar ducts and alveoli form the 'respiratory zone'

32. Lung lobule Pulmonary lobule: Wrapped in elastic C.T., each pulmonary
lobule contains a
lymphatic vessel, an
arteriole, a venule
and a branch of terminal
bronchiole.

33. 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.
Sympathetic stimulation causes airway dilation, while parasympathetic stimulation causes airway constriction.

34. All the branches from the trachea to the terminal bronchioles are conducting
airways – they do not
participate in gas
exchange.

35. 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.

36. 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
(750 ft2 - about the size of a tennis court)

37. Respiratory Membrane
The Respiratory membrane across which diffusion of gases occurs is composed of:
Alveolar lining epithelium
Capillary endothelium
Their fused basement membranes

38. 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)

39. The Lungs 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).

41. Respiratory System Anatomy
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

42. Respiratory System Anatomy
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.

43. Respiratory System Anatomy
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.