Anatomy & Physiology of

Respiratory systemAnita. F. Lopes

Principal, Uday Ger School of Nursing,CGMH

The respiratory tract is the path of air from the nose to the lungs

The organs of the respiratory system make ensure that oxygen enters our bodies and carbon dioxide leaves our bodies.

During inhalation or exhalation air is pulled towards or away from the lungs, by several cavities, tubes, and openings.

To sustain respiration the anatomical structures, neuromuscular system and the cardiovascular system should be normal.

Introduction

BREATHING or ventilation EXTERNAL RESPIRATION, which is the

exchange of gases (oxygen and carbon dioxide) between inhaled air and the blood.

INTERNAL RESPIRATION, which is the exchange of gases between the blood and tissue fluids.

CELLULAR RESPIRATION

Process of Respiration

In addition to these main processes, the respiratory system serves for:

REGULATION OF BLOOD pH, which occurs in coordination with the kidneys, and as a

'DEFENSE AGAINST MICROBES Control of body temperature due to loss

of evaporate during expiration

Parts of Respiratory Tract Upper Respiratory Tract : Nostrils,  Nasal Cavities( Sinuses)  Pharynx, 

Lower respiratory tract: Larynx Trachea Main stem bronchi Segmental bronchi Subsegmental bronchi Bronchioles Terminal bronchioles Respiratory bronchioles Alveolar ducts Alveolar sacs Alveoli

Rigid structure composed of cartilage and bone Septal cartilage divides nasal cavity into two

nasal fossae Palate divides nasal cavity and oral cavity Nose divided into 3 regions Nares or nostrils serve as opening for the nasal

fossae—two cavities in middle of the face Vestibule/vestibular region

◦ Lined with stratified squamous epithelium◦ Contain vibrissae-nasal hair, first line of

defense, function to filter inspired air

The Nose

Filter the air Humidify the air Warm the air Site for sense of small To generate resonance in speech

The Functions of the Nose

Air-filled cavities within the skull (cranium) Paranasal sinuses (four pairs) Function not clear, lighten head and provide

voice resonance Lined with pseudo stratified ciliated

columnar epithelium and goblet cells

Sinuses

Alternate respiratory passage Anterior 2/3 of tongue located in oral cavity Another “respiratory” muscle Lined with stratified squamous epithelium

Oral Cavity

(Throat), hollow, upper portion of the airway and the digestive tract

Subdivided into: nasopharynx, oropharynx, laryngopharynx A flap-like epiglottis closes the opening to the

larynx during swallowing to prevent swallowed matter from entering the trachea.

Pharynx

STRUCTURE:• Enlargement in the airway at the top of

trachea and below pharynx• Framework of cartilage and dense

connective tissue• Glottis (triangular opening between vocal

cords)• Can be closed by Epiglottis or vocal folds• Houses true vocal cords• Connecting zone between upper

and lower airway (vocal cords and below)

Laryngopharynx

FUNCTION:• Passageway for air• Prevents foreign objects from entering trachea• Epiglottis allows air to enter the larynx and

partially covers larynx during swallowing the keep food out of air passages• Voice production

Laryngopharynx

Placement of E.T tube

Epiglottis

Trachea  The trachea, or windpipe, is a

tube that connects the pharynx and larynx to the lungs, allowing the passage of air.

It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus.

This mucus lines the cells of the trachea to trap inhaled foreign

The trachea has an inner diameter of about 25 millimetres (1 in) and a length of about 9 to 15 centimeters (4 to 6 in).

It commences at the lower border of the larynx, level with the sixth cervical vertebra, and bifurcates into the primary bronchi at the vertebral level of thoracic vertebra T5, or up to two vertebrae lower or higher, depending on breathing.

There are about fifteen to twenty incomplete C-shaped cartilaginous rings that reinforce the anterior and lateral sides of the trachea to protect and maintain the airway, leaving a membranous wall (pars membranacea) dorsally without cartilage.

The cartilaginous rings are incomplete to allow the trachea to collapse slightly so that food can pass down the esophagus.

Trachea

Series of branching airways commonly referred to a “generations” or “orders”

The first generation or order is zero (0), the trachea itself.

Bifurcates at the carina

Tracheobronchial Tree

Dichotomous branching (daughter branches)

Airways become progressively narrower, shorter, and more numerous

Cross-sectional area enlarges Common histology (at the nose) and

throughout until the bronchiole generation

Tracheobronchial Tree

Right bronchus◦ Wider◦ More vertical◦ 5 cm shorter◦ Supported by C

shaped cartilages◦ 20-30 degree angle◦ First generation

Left bronchus◦ Narrower◦ More angular◦ Longer◦ Supported by C

shaped cartilages◦ 40-60 degree angle◦ First generation

Main Stem Bronchi

R main stem divides into:◦ Upper lobar

bronchus◦ Middle lobar

bronchus◦ Lower lobar

bronchus

L main stem divides into:◦ Upper lobar

bronchus

◦ Lower lobar bronchus

Lobar Bronchi

R lobar divides into◦ Segmental bronchi◦ 10 segments on right

L lobar divides into◦ Segmental bronchi◦ 8 segments on left

Segmental Bronchi : 3rd generation

Subsegmental Bronchi: Progressively smaller airways1-4 mm diameterAt 1 mm diameter connective tissue sheath disappears

4th to 9th generations

16th to 19th generation Average diameter is 0.5 mm Cilia and mucous glands begin to disappear

totally End of the conducting airway Canals of Lambert-interconnect this

generation,provide collateral ventilation

Terminal Bronchioles

Bronchioles◦ 10-th to 15th generation◦ Cartilage is absent◦ Lamina propria is directly

connected with lung parenchyma

◦ Surrounded by spiral muscle fibers

◦ Epithelial cells are cuboidal◦ Less goblet cells and cilia◦ With no cartilage, airway

remains open due to pressure gradients

Noncartilagenous Airways

Respiratory bronchioles Acinus (aka primary acinus; aka primary

lobule)—respiratory bronchioles to the alveoli

Ducts, sacs, alveolar◦ Squamous epithelium

Gas exchange zone

Ca. 300 million alveoli Between 75 µ to 300 µ in diameter Most gas exchange takes place at

alveolar-capillary membrane

Alveoli

STRUCTURE:• soft spongy, cone-shaped

paired composite organs located within the pleural cavities of thorax

• composed primarily of alveoli and respiratory passage ways

• Stroma is fibrous elastic connective tissue allowing the lungs to recoil passively during expiration

FUNCTION:• Houses respiratory passages

smaller than the primary bronchi

LUNGS

STRUCTURE:•Serous membranes•Parietal pleura lines the thoracic cavity•Visceral pleura covers external lung surfacesFUNCTION:•Produce lubricating fluids •Compartmentalize the lungs

PLEURAE

Two Systems: Bronchial & Pulmonary

Bronchial arteries◦ Arises from aorta till

terminal bronchioles◦ Merge with pulmonary

arteries and capillaries◦ 1% of total cardiac output

(left ventricle) Also nourish

◦ Mediastinal lymph nodes◦ Pulmonary nerves◦ Some muscular pulmonary

arteries and veins◦ Portions of the esophagus◦ Visceral pleura

Blood Supply to the Pulmonary System

1/3 blood returns to right heart◦ Azygous vein◦ Hemiazygous veins◦ Intercostal veins◦ This blood comes form the first two or three

generations of bronchi.

2/3 of blood flowing to terminal bronchioles drains into pulmonary circulation via “bronchopulmonary anastomoses”

Bronchial venous system

The second source of blood to the lungs Primary purpose is to deliver blood to lungs

for gas exchange Also delivers nutrients to cells distal to

terminal bronchioles Composed of arteries, arterioles, capllaries,

venules, and veins

Pulmonary Vascular System

Lymphatic vessels remove fluids and protein molecules that leak out of the pulmonary capillaries

Transfer fluids back into the circulatory system

Lymphatic System

Lungs are innervated by parasympathetic and sympathetic motor fibers and visceral sensory fibers

These nerve fibers enter each lung through the pulmonary plexus on the lung root and run along the bronchial tubes and blood vessels in the lungs

Parasympathetic fibers constrict the air tubes and sympathetic fibers dilate them

Nerve supply of the lungs

Mechanics of breathing

Normal breathing is involuntary,

but the respiratory muscles are

voluntarily

Respiratory Center:

◦ composed of groups of neurons

in the brainstem that control

both inspiration and expiration.

◦ It has 2 areas of special

interest: Medullary rythmicity area

Pneumotaxic area

Control of breathing

Located in the medulla oblongata Includes:

The dorsal respiratory group controls the basic rhythm of inspiration through

bursting impulses that signal contraction of inspiratory muscles. These muscles steadily increase the volume of air entering the lungs

The ventral respiratory group during forceful breathing some neurons increase

inspiratory movements and others activate muscles associated with forceful expiration

MEDULLARY RHYTHMICITY AREA

located in the pons Continuously sends impulses that cause inspiratory bursts from the

dorsal respiratory group. Therefore the pneumotaxic neurons control the breathing rate. When pneumotaxic inhibition is strong, inspiratory bursts are shorter,

increasing the breathing rate. When they are weak, inspiratory bursts are longer, therefore the

breathing rate decreases.

PNEUMOTAXIC AREA

Factors Influencing Breathing Rate and Depth Peripheral chemoreceptors:

◦ found in structures called carotid bodies and aortic bodies sense changes in blood oxygen concentration.

◦ Also found in the walls of certain large arteries in the neck and thorax.

◦ When stimulated, peripheral chemoreceptors transmit impulses to respiratory center and the breathing rate increases.

Inflation reflex: Regulates the depth of breathing Occurs when lung tissues are stretched and

stimulate stretch receptors in the visceral pleura, bronchioles, and the alveoli.

Sensory impulses travel on the vagus nerves to the pneumotaxic area of the respiratory center and shorten the duration of inspiratory movements.

Prevents inflation of lungs during forceful breathing

Emotional upset such as fear and pain can alter the breathing pattern

Factors Influencing Breathing Rate and Depth

AIRWAY ASSESSMENTS 1) Condition that associated with

difficult intubation Congenital anomalies ---> Pierre

Robin syndrome , Down’s syndrome : Infection in airway-->

Retropharyngeal abscess, Epiglottitis : Tumor in oral cavity or larynx

2) Condition that associated with difficult intubation (con’t)

: Enlarge thyroid gland

trachea shift to lateral or compressed tracheal lumen

AIRWAY ASSESSMENTS

Condition that associated with difficult intubation (con’t)

: Maxillofacial ,cervical or laryngeal trauma

: Temperomandibular joint dysfunction

: Burn scar at face and neck

Morbidly obese or pregnancy

AIRWAY ASSESSMENTS

2) Interincisor gap : normal -> more than 3 cms

AIRWAY ASSESSMENT

3) Mallampati classification: Class 3,4 -> may be difficult intubation

AIRWAY ASSESSMENT

Soft palate

Uvula

AIRWAY ASSESSMENT Laryngoscopic

view

Grade 3,4 -> risk for difficult intubation

4) Thyromental distance : more than 6 cms

AIRWAY ASSESSMENT

5) Flexion and extension of neck

AIRWAY ASSESSMENT

AIRWAY ASSESSMENT6) Movement of temperomandibular joint

(TMJ)

Grinding

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