Respiratory system.
Anatomical & Functional subdivisions.
By
Dr. Suhail Ahmad.
The Respiratory System
Organization and Functions of the
Respiratory System
Structural classifications:
– upper respiratory tract
– lower respiratory tract.
Upper Respiratory Tract
• Composed of
– the nose
– the nasal cavity
– the paranasal sinuses
– the pharynx (throat)
– and associated structures.
• All part of the conducting portion of the
respiratory system.
Lower Respiratory Tract
• Conducting portion
– Larynx
– Trachea
– Bronchi
– bronchioles and their associated structures
• Respiratory portion of the respiratory
system
– respiratory bronchioles
– alveolar ducts
– alveoli
Organization of the Respiratory System
• Functional classifications:
–Conducting portion: transports air.
• Nose
• nasal cavity
• Pharynx
• Larynx
• Trachea
• progressively smaller airways, from the
primary bronchi to the bronchioles
Organization of the Respiratory System
• Functional classifications: continued
– Conducting portion: transports air.
– Respiratory portion: carries out gas exchange.
• respiratory bronchioles
• alveolar ducts
• air sacs called alveoli
• Upper respiratory tract is all conducting
• Lower respiratory tract has both conducting
and respiratory portions
The Respiratory Organs
Conducting zone
– Respiratory passages
that carry air to the
site of gas exchange
– Filters, humidifies
and warms air
Respiratory zone
– Site of gas exchange
– Composed of
• Respiratory
bronchioles
• Alveolar ducts
• Alveolar sacs
Conducting zone labeled
Respiratory System Functions
• Breathing (pulmonary ventilation):
– consists of two cyclic phases:
• inhalation, also called inspiration
• exhalation, also called expiration
– Inhalation draws gases into the lungs.
– Exhalation forces gases out of the lungs.
• Gas exchange: O2 and CO2
– External respiration
• External environment and blood
– Internal respiration
• Blood and cells
Respiratory System Functions
• Gas conditioning:
– Warmed
– Humidified
– Cleaned of particulates
• Sound production:
– Movement of air over true vocal cords
– Also involves nose, paranasal sinuses, teeth, lips
and tongue
• Olfaction:
– Olfactory epithelium over superior nasal conchae
• Defense:
– Course hairs, mucus, lymphoid tissue
Nose
•
•
•
•
Provides airway
Moistens and warms air
Filters air
Resonating chamber for
speech
• Olfactory receptors
External nose
Skeletal framework
Bones that contribute to
the skeletal framework of
the nasal cavities include:
• The unpaired
– Ethmoid
– Sphenoid,
– Frontal bone
– Vomer
• The paired
– Nasal
– Maxillary
– Palatine
– Lacrimal Bones
– Inferior Conchae
Regions
• Each nasal cavity consists of three general regions.
• The nasal vestibule is a small dilated space just internal
to the naris that is lined by skin and contains hair
follicles;
• The respiratory region is the largest part of the nasal
cavity, has a rich neurovascular supply, and is lined by
respiratory epithelium composed mainly of ciliated and
mucous cells;
• The olfactory region is small, is at the apex of each
nasal cavity, is lined by olfactory epithelium, and
contains the olfactory receptors
Lateral wall
• The lateral wall is characterized by three
curved shelves of bone (conchae)
– which are one above the other and
– project medially and inferiorly across the nasal
cavity.
• The medial, anterior and posterior margins of
the conchae are free.
The conchae divide each nasal cavity into four air
channels:
• an inferior nasal meatus between the inferior
concha and the nasal floor;
• a middle nasal meatus between the inferior and
middle concha;
• a superior nasal meatus between the middle and
superior concha; and
• a spheno-ethmoidal recess between the superior
concha and the nasal roof.
• These conchae increase the surface area of
the lateral wall.
• The openings of the paranasal sinuses are on
the lateral wall and roof of the nasal cavities.
• The lateral wall also contains the opening of
the nasolacrimal duct, which drains tears from
the eye into the nasal cavity.
Medial wall
• The medial wall of each nasal cavity is the
mucosa-covered surface of the thin nasal
septum
• Oriented vertically in the median sagittal
plane
• Separates the right and left nasal cavities from
each other.
Medial wall
• The nasal septum consists of:
– the septal nasal cartilage anteriorly
– posteriorly, mainly the vomer and the
perpendicular plate of the ethmoid bone
Nasal septum(medial wall).
Blood supply
The nasal cavities have a rich vascular supply for
altering the humidity and temperature of respired
air.
• vessels that originate from branches of the
external carotid artery include:
–
–
–
–
sphenopalatine
greater palatine
superior labial
lateral nasal arteries
• vessels that originate from branches of the
internal carotid artery are:
– anterior ethmoidal
– posterior ethmoidal
Blood supply
Innervation
• Innervation of the nasal cavities is by three
cranial nerves. olfaction is carried by the
olfactory nerve [I];
• General sensation is carried by the trigeminal
nerve [V], the anterior region by the
ophthalmic nerve [V1], and the posterior
region by the maxillary nerve [V2];
• All glands are innervated by parasympathetic
fibers in the facial nerve [VII] (greater petrosal
nerve), which joins branches of the maxillary
nerve [V2] in the pterygopalatine ganglion.
Innervation
Lymphatic drainage.
Paranasal Sinuses
• Paranasal sinuses:
– In four skull bones
– paired air spaces
– decrease skull bone weight
• Named for the bones in which they are housed.
–
–
–
–
frontal
ethmoidal
sphenoidal
maxillary
• Communicate with the nasal cavity by ducts.
• Covered with the same pseudostratified ciliated
columnar epithelium as the nasal cavity.
Paranasal Sinuses
Paranasal sinuses
– Can get infected: sinusitis
Paranasal Sinuses
PHARYNX
• The pharynx is a musculo-fascial tube behind
the nasal and oral cavities.
• Funnel-shaped
– slightly wider superiorly and narrower inferiorly.
• Its anterior wall is largely deficient and
through this defect it communicates with the:
– Nasal cavities
– Oral cavity
– Larynx
• The pharyngeal cavity is a common pathway
for air and 'food'.
PHARYNX
• The pharynx is attached above to the base of
the skull.
• It is continuous below with esophagus in the
neck.
PHARYNX
• Based on the anterior relationships the pharynx is
subdivided into three regions:
– nasopharynx
– oropharynx
– laryngopharynx
• The posterior apertures (choanae) of the nasal
cavities open into the nasopharynx;
• The posterior opening of the oral cavity
(oropharyngeal isthmus) opens into the
oropharynx;
• The superior aperture of the larynx (laryngeal
inlet) opens into the laryngopharynx.
Pharynx
• Walls:
– lined by a mucosa
– contain skeletal muscles primarily used for
swallowing.
• Flexible lateral walls
– distensible
– to force swallowed food into the esophagus.
Larynx
• Short, somewhat cylindrical airway
• Location:
– bounded posteriorly by the laryngopharynx,
– inferiorly by the trachea.
• Prevents swallowed materials from entering
the lower respiratory tract.
• Conducts air into the lower respiratory tract.
• Produces sounds.
Larynx
• Nine pieces of cartilage
– three individual pieces
• Thyroid cartilage
• Cricoid cartilage
• Epiglottis
– three cartilage pairs
• Arytenoids: on cricoid
• Corniculates: attach to arytenoids
• Cuniforms:in aryepiglottic fold
Nine pieces of cartilage
– held in place by ligaments and muscles.
• Intrinsic muscles: regulate tension on
true vocal cords
• Extrinsic muscles: stabilize the larynx
• Framework of the larynx
– 9 cartilages connected by membranes and ligaments
– Thyroid cartilage with laryngeal prominence (Adam’s
apple) anteriorly
– Cricoid cartilage inferior to thyroid cartilage: the only
complete ring of cartilage: signet shaped and wide
posteriorly
– Behind thyroid cartilage and above cricoid: 3 pairs
of small cartilages
1. Arytenoid: anchor the vocal cords
2. Corniculate
3. Cuneiform
– 9th cartilage: epiglottis
Trachea
• A flexible, slightly rigid tubular organ
– often referred to as the “windpipe.”
• Extends through the mediastinum
– immediately anterior to the esophagus
– inferior to the larynx
– superior to the primary bronchi of the
lungs.
Trachea
• Anterior and lateral walls of the trachea
are supported by 15 to 20 C-shaped
tracheal cartilages.
– cartilage rings reinforce and provide some
rigidity to the tracheal wall to ensure that
the trachea remains open (patent) at all
times
– cartilage rings are connected by elastic
sheets called anular ligaments
Trachea
• At the level of the sternal angle(T-4), the
trachea bifurcates into two smaller tubes,
called the right and left primary bronchi.
• Each primary bronchus projects laterally
toward each lung.
• The most inferior tracheal cartilage separates
the primary bronchi at their origin and forms
an internal ridge called the carina.
• Ridge on
internal aspect
of last tracheal
cartilage
• Point where
trachea
branches
(when alive and
standing is at
T7)
• Mucosa highly
sensitive to
irritants: cough
reflex
Carina*
*
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Bronchial Tree
• A highly branched system
– air-conducting passages
– originate from the left and right primary
bronchi.
• Progressively branch into narrower tubes
as they diverge throughout the lungs
before terminating in terminal
bronchioles.
• Primary bronchi
–Incomplete rings of hyaline cartilage
ensure that they remain open.
–Right primary bronchus
• shorter, wider, and more vertically
oriented than the left primary bronchus.
–Foreign particles are more likely to
lodge in the right primary bronchus.
Bronchial Tree
• Primary bronchi
– enter the hilum of each lung
• Secondary bronchi (or lobar bronchi)
– Branch of primary bronchus
– left lung:
• two lobes
• two secondary bronchi
– right lung
• three lobes
• three secondary bronchi.
• Tertiary bronchi (or segmental bronchi)
– Branch of secondary bronchi
– left lung is supplied by 8 to 10 tertiary
bronchi.
– right lung is supplied by 10 tertiary bronchi
– supply a part of the lung called a
bronchopulmonary segment.
Respiratory Bronchioles, Alveolar
Ducts, and Alveoli
• Contain small saccular outpocketings called
alveoli.
• An alveolus is about 0.25 to 0.5 millimeter in
diameter.
• Its thin wall is specialized to promote diffusion
of gases between the alveolus and the blood
in the pulmonary capillaries.
• The spongy nature of the lung is due to the
packing of millions of alveoli together.
Respiratory Bronchioles, Alveolar
Ducts, and Alveoli
• Gas exchange can take place in the respiratory
bronchioles and alveolar ducts as well as in
the lungs, which contain approximately 300–
400 million alveoli.
Pleura and Pleural Cavities
• The outer surface of each lung is tightly
covered by the visceral pleura
• Internal thoracic walls, the lateral surfaces of
the mediastinum, and the superior surface of
the diaphragm are lined by the parietal pleura.
• The parietal and visceral pleural layers are
continuous at the hilum of each lung.
Pleura and Pleural Cavities
• The potential space between these serous
membrane layers is a pleural cavity.
• The pleural membranes produce a thin, serous
fluid that circulates in the pleural cavity and
acts as a lubricant, ensuring minimal friction
during breathing.
67
CXR
(chest x-ray)
68
Chest x rays
Normal female
Lateral (male)
Pneumothorax
• There are many diseases of the respiratory system, including
asthma, cystic fibrosis, COPD (chronic obstructive pulmonary
disease – with chronic bronchitis and/or emphysema) and
epiglottitis
example:
normal
emphysema
you might want to think twice about smoking….
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