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RESPIRATORY SYSTEM

External Respiration:

The process involved with the absorption of O 2 & removal

of CO2 from the body as a whole.

Internal Respiration:

The process involved with the uti li zation of O2 &

removal of CO2 by cells & the gaseous exchange between the cells

and their fluid medium.

(Whi le studying Resp iratory System we are Concerned ma in ly w ith the

Externa l Respi rati on . General ly when we say Respi rati on we m ean Externa l

Respiration.)

RESPIRATORY SYSTEM CONSISTS OF:

Oral and Nasal Cavities

Pharynx

Larynx

Trachea

Bronchi

Lung Tissues

Thoracic Structures responsible for moving air in and out of

lungs. (Muscles of Respiration, Ribs & other bones etc.)

Major Functional Events of Respiration:

Pulmonary Ventilation

Diffusion of O2 & CO2 between Alveoli & Blood

Transport of O2 & CO2.

Regulation of Ventilation

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FUNCTIONS OF RESPIRATORY SYSTEM:

Respiratory Functions:

Provides O2

Eliminates CO2

Non Respiratory Functions:

Phonation

Regulation of Acid-Base Balance

Defense against Microbes

Activation of Angiotensin-I

Synthesis of Hormonal substances:

Prostaglandins

Acetylcholine

Bradykinin

Serotonin

Maintenance of water balance

Temperature Regulation

Anticoagulant function

Smell sensation

Pulmonary circulation acts as a reservoir, filters blood

and absorption of drugs

Functions of conducting zone of airways:

Provides low resistance pathway for airflow; Resistance is

physiologically regulated.

Defends aga inst microbes, tox ic chemicals, and other

foreign Matters.

Warms and moistens the air.

Helps in Phonation.

FUNCTION OF NOSE:

Warming, Moistening & Filtering of incoming air

Olfactory sensation

Helps in sound production.

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PHARYNX:

o Funnel shaped tube, 13 cm Long, Consisting of outer circular

and inner longi tudina l muscle layer , extends between

Internal nares and Cricoid cartilage.

o Consists of : Nasopharynx

Oropharynx

Laryngopharynx

o Functions: Passage of air and food

Provides resonating chamber for sounds

Houses tonsils

PLEURAL SAC:

o Each lung is surrounded by completely c losed sac called

pleural sac

o Has two layers

Visceral pleura

Parietal pleura

o The two layers are completely separate from each other

except at hilum

o The space between the two layers is cal led the Pleural

space, it is a Potential space. It has Pleural fluid approx.

2-3 ml.

o Pleural f luid helps in sliding of the two pleura but resists

their separation.

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