Anatomy And Physiology Of The Airway (1).ppt

ANATOMY AND PHYSIOLOGY OF THE AIRWAY

CONTINUING PROFESSIONAL DEVELOPMENT ANESTHESIOLOGY AND REANIMATION

INTRODUCTION ● A person can live for weeks without food and a few days without water but only a few minutes without oxygen.

● Every cell in the body needs a constant supply of oxygen to produce energy to grow, repair or replace itself, and maintain vital functions.

● The oxygen must be provided to the cells in a way that they can use.

● It must be brought into the body as air that is cleaned, cooled or heated, humidified, and delivered in the right amounts.

THE BODY’S NEED FOR OXYGEN

• Living tissue must have oxygen to survive. • Brain death in humans occurs within 6 to 10 minutes of tissue anoxia. • Rapid and safe airway control is paramount to the successful management of critically ill and injured patients.

AIRWAY ANATOMY Upper airway structures include the: ● Mouth ● Nose ● Pharynx (throat) - Oropharynx - Nasopharynx - Laryngopharynx ● Larynx (voice box)

Vocal cords The lower airway structures include the: ● Trachea (windpipe) ● Bronchi (airways) ● Bronchioles ● Terminal bronchioles ● Alveoli

The upper airway functions to warm, filter, and humidify the air before it enters the lower airway The functions of the lower airway include air conduction, filtration,

warming, humidification, and removal of foreign particles. Respiration occurs in the respiratory bronchioles of the lower airway

RESPIRATORY TRACTS AND STRUCTURE ● Mouth ● Nose ● Pharynx - Oropharynx - Nasopharynx - Laryngopharynx ● Larynx ● Trachea ● Bronchi ● Bronchioles ● Terminal bronchioles ● Respiratory bronchioles ● Alveolar ducts ● Alveolar sacs ● Alveoli

conducting zone - cavities and tubes - anatomic dead space

respiratory zone

EXTERNAL NASAL STRUCTURES BONY FRAMEWORK frontal bone nasal bone maxilla CARTILAGINEUS FRAMEWORK lateral nasal cartilages septal catrilages alar cartilages external nares (nostril) fibrous connective and adipose tissue

NOSE AND NASAL CAVITIES ● Olfactory epithelium for sense of smell

● Pseudostratified ciliated columnar with goblet cells lines nasal cavity ● Nose hairs at the entrance to the nose trap large inhaled particles.

frontal sinus

superior concha sphenoid sinus

middle concha internal nares inferior concha

external nares

● Nasal concha provide air turbulence and promotes filtration and extra time for warming and humidifying air

PARANASAL SINUSES ● to reduce the weight of the skull, ● to produce mucus ● to influence voice quality by acting as resonating chambers.

frontal sinus

sphenoid sinus

hard palate

PHARYNX (THROAT) external nares

● connects nasal cavity with larynx (± 5 inch) ● extends from the base of the skull to 6th cervical vertebrae

nasal cavity

internal nares

Soft palate

uvula

pharynx

● serves both the respiratory and digestive systems epiglottis

● three regions according to location:

glottis

- nasopharynx

- oropharynx - laryngopharynx (hypopharynx).

trachea

hard palate

NASO-PHARYNX nasal cavity

● from choanae to soft palate ● openings of auditory (Eustachian) tubes from middle ear cavity

Soft palate

naso pharynx uvula

● adenoids or pharyngeal tonsil in roof epiglottis

● area above where food enters thus towards the nasal cavity ● during swallowing, uvula projects upwards closing off passage to the nasal cavity

glottis

trachea

hard palate

OROPHARYNX

nasal cavity

Soft palate uvula

● the portion of the pharynx that is posterior to the oral cavity.

oro pharynx

● extends from soft palate to the epiglottis epiglottis

● area where both food and air passes

glottis

trachea

hard palate

LARYNGO-PHARYNX nasal cavity

● posterior to the epiglottis and extends to the larynx

Soft palate uvula

● at larynx, food and air take different passageways laryngo pharynx epiglottis glottis

Histology of the pharynx changes from pseudostratified epithelium to stratified squamous epithelium when going from naso-to oro-to laryngopharynx

trachea

LARYNX (VOICE BOX) Epiglottis Hyoid bone Thyrohyoid membrane

Corniculate cartilage Thyroid cartilage (Adam’s apple) Arytenoid cartilage Crycothyroid ligament Cricoid cartilage Cricotracheal ligament

Thyroid gland Parathyroid gland Tracheal cartilage

BRONCHIALE TREE The trachea and bronchi have supporting cartilage to keep airways open Bronchiole walls contain more smooth muscle, a feature used in airflow regulation

THE RESPIRATORY ZONE

● contains alveoli, tiny walled sacs where gas exchange occurs ● alveolar ducts end in cluster of alveoli called alveolar sacs

photomicrograph

ALVEOLI AND PULMONARY CAPILLARIES ● The pulmonary artery carry blood which is low in oxygen from the heart to the lungs ● These blood vessel branch repeatedly, forming dense network of capillaries that completely surround each alveolus ● O2 and CO2 are exchanged between the aveoli and pulmonary capillaries. ● Blood leaves the capillaries via the pulmonary vein which transport oxygenated blood back to the heart

alveolar macrophage simple squamous epithelium (type 1 cell) surfactan secreting cell (type 2 cell) capillary

STRUCTURE OF THE RESPIRATORY MEMBRANE

O2 CO2 O2 O2 CO2

VENTILATION AND RESPIRATION

IMPORTANT DEFINITIONS Ventilation the process of moving a volume of gas in and out of the lungs

Respiration ● gas exchange (O2/CO2) across the alveolar - capillary membrane (external) ● or at the tissue/cellular level (internal)

BOYLE’S LAW relationship between pressure and volume

volume

pressure

volume

pressure pressure

volume

pressure

volume

INSPIRATION muscle contraction

EXPIRATION Muscle relaxation

INTRAPULMONARY (INTRAALVEOLAR) PRESSURE CHANGES Intrapulmonary (intraalveolar) pressure is the pressure within the alveoli. Between breaths, it equals atmospheric pressure (760 mmHg)

INTRAPULMONARY (INTRAALVEOLAR) PRESSURE CHANGES

INTRAPLEURAL PRESSURE the pressure within the pleural cavity, always negatiive, and acts like a suction to keep the lungs inflated

the negative intrapleural pressure is due to: • Surface tension of alveolar fluid • Elasticity of lungs • Elasticity of thoracic wall

the negative intrapleural pressure is due to….

SURFACE TENSION OF ALVEOLAR FLUID

The surface tension of the alveolar fluid tends to pull each of the alveoli

inward and therefore pulls the entire lung inward. Surfactan reduce this force

the negative intrapleural pressure is due to:

ELASTICITY OF LUNGS

the elastic tissue in the lungs tends to recoil and pull the lungs inward. As the lung moves away from the thoracic wall, the cavity becomes slightly larger, decreasing pressure

the negative intrapleural pressure is due to:

ELASTICITY OF THORACIC WALL The elastic thoracic wall tends to pull away from the lung, further enlarging the pleural cavity and creating this negative pressure

The surface tension of pleural fluid resist the actual separation of

the lung and thoracic wall

INTRAPLEURAL PRESSURE CHANGES

INTRAPLEURAL PRESSURE CHANGES

FACTORS AFFECTING VENTILATION: ● resistance within the airways

● lung compliance

● thoracic wall compliance

RESISTANCE WITHIN THE AIRWAY as air flow into the lungs, the gas molecules encounter resistance when they strike the walls of the airway. Therefore the diameter of the airway affects resistance

smooth muscle

elastic fibres

parasympatic neuron

histamin

epinephrine

LUNG COMPLIANCE The ease with which the lung expand is called lung compliance. It is primary determined by two factors: • The stretchability of elastic fibres within the lungs • The surface tension within the alveoli • Comp : Δ V / Δ P

the stretchability of elastic fibres within the lungs

the surface tension within the alveoli

THORACIC WALL COMPLIANCE

● obesity

● intraabdominal distension

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