THE RESPIRATORY SYSTEM
• The complex of organs and tissue which are necessary to exchange
blood carbon dioxide (CO2) with air oxygen (O2) is called the
respiratory system. It consists of
• Functional Division: Conductive & Respiratory portions.
• Anatomical Division: into Upper (Larynx) and Lower.
• Conductive Portion: Prepare the inspired Air (Pollutants,
Temperature and Humidity) Structures that perform these functions.
• Respiratory Portion: Has structures which form the process of Gases
Exchange (the exchange of CO2 and O2)
How the lungs work
• The lungs work after receiving air by:
• The air enters the nose or mouth where it is filtered, warmed, and moistened.
• The air then travels down the throat and enters the trachea.
• The air proceeds down the trachea, which branches into the left and right
bronchi.
• These two main stem bronchi continue to branch into smaller bronchi and
they eventually branch into bronchioles Broncho-Pulmonary Segments,
Alveoli.
How the lungs work continued
• After the air reaches the bronchioles:
• The bronchioles end in sacs known as alveoli. They act as balloons that inflate
when breathing in.
• Gas exchange occurs at the alveoli. The concentration of oxygen is greater in
the alveoli during inspiration then in the capillaries so the oxygen will diffuse
across the alveolar walls and enter the blood plasma and carbon dioxide
undergoes the opposite process.
NASAL CAVITY &
PARANASAL SINUSES
Nasal Cavity
The nasal cavity extends from the nostrils in front to
the posterior nasal apertures or choanae behind
This is where the nose opens into the nasopharynx
(Eustachian Tube)
The nasal vestibule is the area of the nasal cavity
lying just inside the nostril
Nasal Septum
The nasal cavity is divided into right and left halves by
The Nasal Septum
The septum is made up of the septal cartilage
(Hyaline), the vertical plate of the ethmoid, and the
vomer
Walls of the Nasal Cavity
 Each half of the nasal cavity has a Floor, A Roof, A
Lateral Wall, And A Medial Or Septal Wall
 The Floor is formed by palatine process of maxilla
and the horizontal plate of the Palatine Bone
 The Roof is narrow and is formed Anteriorly
beneath the bridge of the nose by The Nasal And
Frontal Bones
 In the Middle By The Cribriform Plate of the
Ethmoid, located beneath the anterior cranial fossa
Walls of the Nasal Cavity
Posteriorly by the downward sloping body of the
sphenoid
The Lateral Wall has three projections of bone called
the superior, middle, and inferior nasal conchae
The space below each concha is called a Meatus
Sphenoethmoidal Recess
The Sphenoethmoidal Recess is a small area above
the superior concha
It receives the opening of the sphenoid air sinus
The Superior Meatus lies below the superior concha
It receives the openings of the Posterior Ethmoid
Sinuses
Middle Meatus
 The middle meatus lies below the middle concha
 It has a rounded swelling called the bulla ethmoidalis that is
formed by the middle Ethmoidal Air Sinuses, which open on
its upper border
 A curved opening, the hiatus semilunaris, lies just below the
bulla
 The anterior end of the hiatus leads into a funnel-shaped
channel called the Infundibulum, which is continuous with
the frontal sinus
 The Maxillary Sinus opens into the middle meatus through
the hiatus semilunaris
Inferior Meatus
The Inferior Meatus lies below the inferior concha
It receives the opening of the lower end of the
Nasolacrimal Duct, which is guarded by a fold of
mucous membrane
Medial Wall (Nasal Septum)
 The medial wall is formed by the nasal septum
 The upper part is formed by the vertical Plate Of
The Ethmoid And The Vomer
 The anterior part is formed by the septal cartilage
 The septum rarely lies in the midline, thus
increasing the size of one half of the nasal cavity
and decreasing the size of the other
Mucous Membrane
 The vestibule is lined with modified skin and has coarse
hairs
 The area above the superior concha is lined with
olfactory mucous membrane and contains nerve
endings sensitive to the reception of smell
 The lower part of the nasal cavity is lined with
respiratory mucous membrane
 A large plexus of veins in the submucous connective
tissue is present in the respiratory region. Epitasis
Mucous Membrane
The presence of warm blood in the venous plexuses
serves to Heat Up The Inspired Air as it enters the
respiratory system
The presence of Mucus on the surfaces of the
conchae Traps Foreign Particles and organisms in the
inspired air
These particles are then swallowed and destroyed by
gastric acid
Nerve Supply
The Olfactory Nerves from the olfactory mucous
membrane ascend through the Cribriform Plate of
the ethmoid bone to the olfactory bulbs
The nerves of Ordinary Sensation are branches of the
Ophthalmic Division and the Maxillary Division of
the Trigeminal Nerve
Blood Supply
 The arterial supply to the nasal cavity is from branches
of the Maxillary Artery, one of the terminal branches of
the external carotid artery
 The most important branch is the Sphenopalatine
Artery
 The sphenopalatine artery anastomoses with the
septal branch of the superior labial branch of the facial
artery in the region of the vestibule
 The submucous venous plexus is drained by veins that
accompany the arteries
Lymph Drainage
The lymph vessels draining the vestibule end in the
Submandibular Nodes
The remainder of the nasal cavity is drained by
vessels that pass to the Upper Deep Cervical Nodes
Paranasal Sinuses
 The paranasal sinuses are cavities found in the interior
of the maxilla, frontal, sphenoid, and ethmoid bones
 They are lined with mucoperiosteum and filled with air
 They communicate with the nasal cavity through
relatively small apertures
 The maxillary and sphenoidal sinuses are present in a
rudimentary form at birth
 They enlarge appreciably after the eighth year and
become fully formed in adolescence
Drainage of Mucus
The mucus produced by the mucous membrane is
moved into the nose by Ciliary Action Of The
Columnar Cells
Drainage of the mucus is also achieved by the siphon
action created during the blowing of the nose
Function of Paranasal Sinuses
The function of the sinuses is to act as resonators to
the voice
They also reduce the weight of the skull
When the apertures of the sinuses are blocked or
they become filled with fluid, the quality of the voice
is markedly changed
Maxillary Sinus
The maxillary sinus is pyramidal in shape and located
within the body of the maxilla behind the skin of the
cheek
The roof is formed by the floor of the orbit, and the
floor is related to the roots of the premolars and
molar teeth
The maxillary sinus opens into the middle meatus of
the nose through the hiatus semilunaris
Frontal Sinuses
The two frontal sinuses are contained within the
frontal bone
They are separated from each other by a bony
septum
Each sinus is roughly triangular, extending upward
above the medial end of the eyebrow and backward
into the medial part of the roof of the orbit
Sphenoidal Sinuses
The two sphenoidal sinuses lie within the body of the
sphenoid bone
Each sinus opens into the sphenoethmoidal recess
above the superior concha
Ethmoid Sinuses
The ethmoidal sinuses are anterior, middle, and
posterior and they are contained within the ethmoid
bone between the nose and the orbit
They are separated from the latter by a thin plate of
bone so that infection can readily spread from the
sinuses into the orbit
Ethmoid Sinuses
The anterior sinuses open into the infundibulum
The middle sinuses open into the middle meatus, on
or above the bulla ethmoidalis
The posterior sinuses open into the superior meatus
Nasal Cavity
• The Nasal cavity is divided into three structurally and
functionally different parts.
• The Vestibules (the first ~1.5 cm of the conductive portion
following the nostrils) are lined with a keratinised
stratified squamous epithelium. Hairs, which filter large
particulate matter out of the airstream, and sebaceous
glands are also present.
•
At the transition from the vestibule to the respiratory
region of the nasal cavity the epithelium becomes first
stratified squamous and then pseudostratified columnar
and ciliated. Mucus producing goblet cells are present in
the epithelium.
The olfactory epithelium
• Formed by Olfactory Cells, Sustentacular Cells and basal
cells. Basal cells can be identified by their location.
Sustentacular cells are preferentially located in the
superficial cell.
• Cilia are not visible and goblet cells are absent from the
olfactory epithelium. Cilia do not move, because they
Lack Dynein Arms which are necessary for cilial motility.
The cell membrane covering the surface of the cilia
contains olfactory receptors which Lightly stained
rounded areas in the lamina propria represent bundles of
Olfactory Axons in the lamina propria. Small mucous
glands, Olfactory Glands Or Bowman's Glands,
Nasal Cavity, Olfactory Region, rat - Alcian blue & van Gieson
Respiratory region of the nasal cavity - H&E, van Gieson
Nasal Cavity
• The surface of the lateral parts of the nasal cavity is thrown into folds
by bony projections called Conchae. These folds increase the surface
area of the nasal cavity and create turbulence in the stream of
passing air, both of which facilitate the conditioning (warming,
cooling and filtration) of the air. Mucous and serous glands in the
connective tissue underlying the epithelium, the lamina propria,
supplement the secretion of the goblet cells. Superficial Blood
Vessels
Pharynx
• The pharynx connects the nasal cavity with the larynx.
• The pharynx is either lined with respiratory
epithelium (nasopharynx) or with a stratified
squamous epithelium (oropharynx), which also
covers the surfaces of the oral cavity and the
oesophagus. Lymphocytes frequently accumulate
beneath the epithelium of the pharynx.
• Accumulations of lymphoid tissues surrounding the
openings of the digestive and respiratory passages
form the Tonsils.
Pseudostratified Columnar Epithelium
• Composed of one Layer of Cells
• All cells of this type of epithelium are in contact with the
basement membrane, but not all of them reach the surface of
the epithelium.
• Nuclei of the epithelial cells are typically located in the widest
part of the cell. Consequently, the nuclei of cells which do or
do not reach the surface of the epithelium are often located at
different heights within the epithelium and give the
epithelium a stratified appearance.
• The epithelium will look stratified but it is not - hence its name
"pseudostratified".
• Pseudostratified columnar epithelia are found in the
Respiratory System
Pseudostratified columnar epithelium