Upper Respiratory System
-nose and throat (pharynx)

Lower Respiratory System
-larynx, trachea, bronchi and lungs

Respiration
-exchange of gases between the atmosphere, blood and cells


3 processes involved in respiration

1. Pulmonary ventilation
-inspiration and expiration of air between lungs and atmosphere
-”breathing”

2. External respiration
-exchange of gases between the lungs and the blood

3. Internal respiration
-exchange of gases between the blood and cells
-cardiovascular system

**failure of respiratory system or cardiovascular system leads to cell
death due to oxygen starvation and metabolic waste build

Nose
-contains external and internal portion
-external is composed of cartilage covered by skin
-internal (nasal cavity) large cavity in the skull inferior to the cranium and superior to the
mouth

Nasal septum
-vertical partition that divides the nasal cavity
-anterior part made of cartilage
-posterior part made of the vomer bone and the perpendicular plate of the ethmoid bone


Clinical Application

Rhinoplasty
-”Nose Job” surgical procedure in which the external structures are altered
-usually done for cosmetic reasons
-sometimes done to repair fractures or deviated septum

Nose Physiology

Interior specialized for 3 functions

1. air is warmed, moistened and filtered
2. olfactory stimuli received-only direct stimulus to the brain
3. large, hollow resonating chamber helps produce speech sounds

Pharynx (Throat)

-funnel shaped tube about 13 cm long that starts at the back of the nasal cavity and extends to the cricoid cartilage
-composed of skeletal muscles and lined with mucous membranes

-2 functions
1. passage for food and air
2. resonating chamber for speech sounds-made of three parts

1. Nasopharynx
-lies posterior to internal nasal cavity and extends to the plane of the soft palate
-exchanges small amounts of air with the auditory (Eustachian) tubes so that the air pressure equalized between the atmospheric air and the air pressure in the middle ear

2. Oropharynx
-posterior to the oral cavity and extends from the soft palate to the level of the hyoid bone
-contains opening from the mouth
-common passageway for air, food and drink

3. Laryngopharynx
-extends from the hyoid bone level and becomes continuous with the esophagus

Larynx
-short passageway that connects the pharynx with the trachea
-midline of the neck between the C4 and C6 vertebrae

Thyroid Cartilage
-2 plates of cartilage that form the anterior wall of the larynx
-larger in males (Adam’s Apple)

Epiglottis
-large, leaf-shaped piece of cartilage lying on the top of the larynx
-”stem” attached to the thyroid cartilage
-”leaf” moves up and down like a trap door

**swallowing causes the larynx to move up, which causes the epiglottis to cover the glottis

Glottis
-vocal folds and the space between the folds

Cricoid Cartilage
-forms inferior wall of the larynx
-attached to the first ring of cartilage of the trachea

Voice Production
-muscles contract, pull on the elastic ligaments which stretch the vocal folds out into the air passage (narrows the glottis)
-air pushed through and vibrates, this sends sound waves into the pharynx, nose and mouth (higher the pressure the louder the sound)
-pitch is controlled by the tension of the vocal folds (tight = high)
-male folds are thicker, produces lower sounds


Trachea
-passageway for air about 12 cm in length and 2.5 cm in diameter
-anterior to the esophagus and extends from the larynx to the 5th thoracic vertebrae
-16 - 20 incomplete rings of hyaline cartilage which allows for protection anteriorly and flexibility posteriorly for swallowing

Clinical Application: Tracheotomy and Intubation
Tracheotomy
-skin incision made followed by a small longitudinal incision into the trachea
-patient inspires through a tube placed in the incision

Intubation
-tube placed into the mouth or nose and forced through the larynx and
trachea

-tube wall pushes back any obstruction
-mucous blockage sucked out through the tube

Bronchi
-trachea divides at the sternal angle
-right and left primary bronchus
-right primary bronchus is more vertical, shorter and wider than the left
-made of incomplete rings of cartilage and lined by pseudo stratified ciliated epithelium

Secondary (lobar) bronchi
-primary split after entering each lung
-secondary bronchi go to each lobe of each lung

-secondary split into tertiary (segmental) bronchi

-which divide into bronchioles

-which split into terminal bronchioles

As branching is more extensive several structural changes occur

1st - rings of cartilage replaced by plated that disappear in the bronchioles

2nd - as cartilage amount decreased, smooth muscle increases

3rd - epithelium changes from pseudo stratified ciliated to simple cuboidal in the terminal bronchioles

Clinical Application: Asthma
-smooth muscle of bronchioles contract, reducing the diameter of the airway
-inhalators (bronchiole dilators) relax the muscle and open the airways

Lungs
-2 layers of membrane (pleural membrane) enclose and protect each lung

Visceral Pleura- -covers lungs

Parietal Pleura- -attached to the wall of the thoracic cavity

Pleura Cavity- -filled with fluid

Gross Anatomy of the Lungs

base- -broad inferior portion that is concave and fits over the diaphragm
apex--narrow superior portion
costal surface--touch the ribs
hilus--area in which bronchi, blood vessels, lymphatic vessels and nervous tissue enter and leave the lungs
cardiac notch--ONLY on the left lung

*Right lung is thicker, broader and shorter than the left

Lobes and Fissures

oblique fissure--extends downward and forward

horizontal fissure- -only in the right lung

superior lobe- -above oblique fissure

inferior lobe- -below oblique fissure

middle lobe
-only in the right lung
-subdivision of right superior lobe

**each lobe receives its own secondary (lobar) bronchus
**each secondary bronchus named after the lobe it serves

Bronchopulmonary Segment
-section of lung that surrounds a tertiary bronchus
-may be removed if affected with tumors

Lobules
-small compartments of a bronchopulmonary segment
-wrapped in elastic connective tissue
-contain lymphatic vessel, arteriole, venule and branch from a terminal bronchiole

terminal bronchiole splits into respiratory bronchioles which split into alveolar ducts

**alveolar ducts lead to alveolar sacs

Alveolar Sacs
-important in gas exchange
-surrounded by capillaries

3 specialized cells found in the sac

1. Squamous pulmonary epithelial cells--allow for diffusion of oxygen and carbon dioxide from the surrounding vascular cells

2. Septal cells
-cuboidal cells that produce surfactant--phospholipid substance that lowers surface tension

3. Alveolar macrophages (dust cells)- -phagocytic cells

Clinical Application: Nebulization
-administering medication in the form of droplets that are suspended in air
-patients inhales the medication as a fine mist

3 processes of Respiration

1. Pulmonary ventilation (Breathing)
-air in, air out
-exchange of air between atmosphere and alveoli
-air moves into the lungs when the pressure inside is less than the pressure of atmospheric air (out for opposite reasons)

Boyle’s law--pressure of a gas in a closed container is inversely proportional to the volume of the container

Inspiration (inhalation)
-breathing in
-increase the volume of the lungs by two ways

Diaphragm
-main inspiratory muscle
-contraction causes it to flatten and increase the vertical dimension of the thoracic cavity
-may increase by 1cm to 10 cm
-accounts for movement of 75% of the air that enters the lungs

External intercostals
-contractions pull ribs up which pushes the sternum forward
-increases the diameter of the thoracic cavity


Expiration
-breathing out
-NORMAL expiration is a passive process
-during high levels of ventilation it becomes active
-abdominal muscles contract and force the diaphragm up
-internal intercostals contract and pull ribs down

One ventilation (respiration) = one inspiration + one expiration
-normal adults ventilate about 12 times per minute

Pulmonary Volumes
Tidal volume--normal amount of air that moves in with each inspiration and out with each expiration

Inspiratory Reserve volume
-inhaling deeply
-3100 ml above the tidal volume

Expiratory Reserve volume
-forcibly exhaling
-1200ml above the tidal volume

Residual volume
-amount left AFTER expiratory reserve volume is expelled
-because some air remains in airways inside the lungs
-1200ml

Minimal volume
-lungs with only minimal volume will not float
-legal tool to determine still birth
-fetal lungs contain no air, so lung of stillborn will not float

2. External Respiration
-exchange of oxygen and carbon dioxide between the alveoli of lungs and the pulmonary blood capillaries
-alveolar air has a partial pressure of oxygen of 105 mmHg pO₂

Dalton’s Law
-each gas in a mixture exerts its own pressure as if all the other gases were not present
-partial pressure = p
-the pO₂ of deoxygenated blood in the alveolar capillaries is only 40 mmHg
-oxygen diffuses from alveoli into the deoxygenated blood until an equilibrium is reached
-this gives oxygenated blood a pO₂ of 105 mmHg (equal to atmospheric air)
-CO₂ diffuses in the opposite direction
-pCO₂ in deoxygenated blood is 45 mmHg - alveolar air is 40 mmHg

Adaptations That Increase External Respiration Effectiveness
1. Thickness--alveolar sac- capillary complex only 2 cells layers thick

2. Surface area
-more surface area the more diffusion possible
-surface area of alveoli in the lungs is about 70 m²

3. Large number of capillaries--allow 100 ml of blood to participate in gas exchange at one time

4. Narrow Capillaries
-allow RBCs to flow through in a single file
-provides maximum exposure

Factors Effecting Efficiency
1. Altitude--atmospheric pO2 decreases as altitude increases

2. Surface area- -damaged surface area (smoke, cancer, etc.)

3. Small volumes- -certain drugs slow respiration rate