Physiological anatomy of respiratory system

Physiological Anatomy of

Respiratory system

D.A. Asir John Samuel, BSc (Psy), MPT (Neuro Paed), MAc, DYScEd, C/BLS, FAGE

Lecturer, Alva’s college of Physiotherapy, Moodbidri

Dr.Asir John Samuel (PT)

Respiration

• Exchange of gases between an organism and

its environment

• Physiological processes that contribute to

uptake of oxygen and elimination of carbon

dioxide


Anatomical structures

• Respiratory passages

• Lungs

• Respiratory muscles operating on body

structures of thoracic cage


Respiratory passages

• Nasal cavity

• Pharynx

• Larynx

• Trachea

• Bronchi

• bronchioles


Nose (nasal cavity)

• Both olfactory and respiratory functions

• Inspired air is warmed or cooled

• Brought close to body temperature

• Also moistened by fluid derived from

transudation through epithelium and

secretions of glands and goblet cells Dr.Asir John Samuel (PT)

Nose (nasal cavity)

• Warming and humidification of inspired air

• Moist air is necessary for integrity and proper

functioning of ciliated epithelium

• Secretions have bactericidal actions

• Stiff hairs trap dust and foreign particles

• Resonator in voice and speech


Pharynx

• Nasal cavity opens posteriorly into

nasopharynx

• During swallowing, respiration is temporarily

inhibited permitting food to enter oropharynx

• Elevation of larynx and closure of vocal cords

prevents entry of food into larynx


Larynx

• Lower part of pharynx and at upper end of

trachea

• Cartilagenous, cartilages being held together

ligaments

• Production of voice

• Achieved by forcible expulsion of air from

lungs, causing production of sound

• Contraction of adductor muscles and glottis Dr.Asir John Samuel (PT)

Trachea and main bronchi

• Tubular structure about 10cm long and 1cm in

diameter

• Begins at lower end of larynx

• Lumen of trachea is kept patent by a number

of C-shaped fibro cartilaginous ring

• Divides into right and left bronchus Dr.Asir John Samuel (PT)

Lungs

• One on either side

• Large cone-shaped spongy structures which

occupy most of thoracic cavity

• Left lung is divided into 2 lobes and right into 3

• Lined by pleura (visceral and parietal)


Lung lobes


Bronchioles



Terminal branches

• Bronchioles branch further and the smallest

subdivisions being terminal bronchiole

• It is estimated, no. of divisions from tracheal

bifurcation to terminal bronchiole is 16

• Total no. of divisions till alveoli is 23




Dead space

• The bronchiole tree upto and including

terminal bronchiole is purely conducting

pathway for passage of air

• Respiratory gas exchange does not occur in

this region

• Referred to as anatomical dead space


Gas exchange apparatus

• Terminal bronchiole divides into respiratory

bronchioles

• Respiratory bronchioles give rise to a number of

short passages called alveolar ducts

• These open into wider alveolar sacs

• On the walls located pulmonary alveoli

• Some alveoli present in respiratory bronchioles Dr.Asir John Samuel (PT)


Alveolus


Pulmonary alveoli

• Alveoli are lined by a single layer of flat epithelial

cells

• Alveolar type I cells are principal lining

• Type II are cuboidal cells, secrete surfactant

• Average width is 0.3 mm

• 300 million alveoli in human lung



Surfactant

• Formed from fatty acids by alveolar type II cells

• Complex mixture of several phospholipids,

proteins and ions

• Most important components are phospholipid,

dipalmitoyl phosphatidyl choline (DDPC),

surfactant appoproteins and calcium ions


RD (Respiratory Distress)

• Deficiency of surfactant at birth causes a serious

pulmonary disease of new born called Neonatal

Respiratory Distress Syndrome (NRDS) or hyaline

membrane disease

• Lung shows several areas of collapse

• Reduced compliance

• Poor expansion

• Presence of fluid in alveoli Dr.Asir John Samuel (PT)

Muscles of respiration

• Downward and upward movement of

diaphragm

• Elevation and depression of ribs


Pleural pressure

• Pressure of fluid in the narrow space b/w

visceral pleura and parietal pleura

• Normally a slight suction, which means a slightly

negative pressure

• At beginning of inspiration is about -5 cm of H2O

• Required to hold lungs open to their resting level


Pleural pressure

• During normal inspiration, the expansion of

chest cage pulls outward on lungs with still

greater force

• Creates still more negative pressure to an

average of about -7.5 cm of H2O

• Increasing negativity of pleural pressure from -

5 to -7.5 cm of H2O

• During expiration, events are reversed Dr.Asir John Samuel (PT)

Alveolar pressure

• Pressure of air inside the lung alveoli

• Pressure in all parts of respiratory tree are

equal to atmospheric pressure

• 760 mm of Hg/0 cm of H2O

• During normal inspiration, alveolar pressure

decreases to about -1 cm of H2O Dr.Asir John Samuel (PT)

Alveolar pressure

• Slight negative pressure is enough to pull 0.5

liter of air into lungs in 2 seconds

• During expiration, opposite changes occur

• Alveolar pressure rises to about +1 cm of H2O

• This forces 0.5 liter of inspired air out of lungs

during 2-3 seconds of expiration


Transpulmonary pressure

• Pressure difference b/w alveolar pressure and

pleural pressure

• Pressure difference between that in alveoli

and that on outer surfaces of lungs

• Measure of elastic forces in lungs that tend to

collapse at each instant respiration

• Recoil pressure Dr.Asir John Samuel (PT)

Compliance of lungs

• Extent to which lungs expand for each unit

increase in transpulmonary pressure

• Total compliance of both lungs together in

normal human being averages about 200 ml

of air/1 cm of H2O

• Every time transpulmonary pressure increases

by 1 cm of H2O, lung volume expands 200 ml Dr.Asir John Samuel (PT)

Compliance diagram

• Inspiratory compliance curve and expiratory

compliance curve

• Determined by, elastic forces of lungs

- Elastic forces of lung tissue itself

- Elastic forces caused by surface tension of

fluid that lines inside walls of alveoli Dr.Asir John Samuel (PT)

Pressure-volume curve


Pressure-volume curve


Spirometry

• The process by which pulmonary ventilation is

recorded by the volume movement of air into

and out of lungs

• Consists of drum inverted over a chamber of

water, with drum counterbalanced by weight

• Drum rises and falls. Recorded on paper



Spirometry




Physiological anatomy of respiratory system

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