The Respiratory System

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O2 enters body and CO2 is eliminated pulmonary ventilation

gas exchange in lungs

blood transport

gas exchange in tissues

control of ventilation

The conducting always = gas exchange does not occur

carrys air to and from area involved in gas exchange

moistening and cleaning inhaled air

2 parts

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Upper Respiratory tract

Nasal cavity - divided by nasal septum

air enters respiratory tract via nose

lined by skin with sebaceous and sweat glands Hair act as fillers

each lateral wall has bony elevations

superior/middle/inferior nasal conchae

air steam passes ove conchae

small dust particles precipate out

all but vestibules lined by mucous

covered by columner epithelium (goblet cells)

mucous and serous glands, secret1L of fluid per day

serous glands - lysosome

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tube of skeletal muscle

3 regions - nasopharynx, oropharynx, larynopharynx

air passes with nasopharynx from cavity

via 2 internal nares or chronae

nasopharynx lies above palate- closed off during swallowing

posterior wall - pharyngeal tonsils

oral cavity connects with oropharynx

Laryngopharynx - lies behind eplglottis

connects orophaynx with oesophagus

pathway for air and food

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Lower Respiratory tract

comprises of larynx, bronchi, bronchioles

Larynx - upper frontal region of neck

betwen root of tongue

suspended from hyoid bone

aryteriod corniculates cunei forms

onicois epiglottis thyroid(adams Apple)

cartillages connected by intrinsic muscle

principles muscles used in phonation

transverve arteroid

lateral oncoarteroid, posterior oncaaryteroid, lined with mucous membrane with pharynx and trachea

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glottis - the gap between vocal cords

V-shaped during quiet breathing

becomes rounded with inspiration

spiglottis - leaf shaped cartilage

reflected during swallowing

Tracheabronchial tree - trachea - divides and gives 2 bronchi

Posterior wall - trachealis muscle

contaction narrows airways

lined with goblet cells and mucosa

2 principles bronchus - wider, shirter and more vertically

right lungs gets infections

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Respiratory part of lungs

Terminal bronchioles - alveoli

divides into two branches

Alveolar wall forms major part

thin and contains 2 types of cells

type 1 pheumocytes - gas exchange

type 2 - synthesize surfactant

elastic fibres surround alveoli

help tissue recoil during respiration

respiratory bronchiole and structures

functional unit of lung - pulmonary

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Blood supply

lungs have a double circulation

pulmonary circulation

enables bloods o2 supply and CO2 supply to be eliminated

nourishes alveoli

bronchial circulation

blood flow through 2 lungs 5L/min

1L of blood within vessels

100 ml within capillary beds in gas exchange

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Nerve Supply of the lungs

autonomic pathways to

bronchial smooth muscle

bronchial glands

sympathetic stimulation


Na acts of beta2 adrenceptors


mild vasoconstriction of smooth muscle

stimulate increased secretion of glands

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Pulmonary ventilation

lungs are passive

chest wall and diaphragm move

Inspiration - contraction of inspiratory muscle, volume of thorax increases

lungs stretch, intrathoracic pressure drops

lungs recoil, pressure rises

Muscles of respiration are skeletal

controlled by somatic and autonomic motor neurones

involuntary but controlled

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2 serous membrane

parietal pleaura- outer membrane to part of chest wall and diaphragm

visceral pleaura, inner membrane covers wing

surfaces are smooth and covered in fluid

2 membranes separated by fluid film

pressure in cavity is subatomospheric


if chest wall is punched, air enters cavity

pleaurae separate

lung collapses chest wall expands

traumatic phenomothorax

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diaphragm and external interocstal muscles

Diaphragm- striated muscles

connected to central tendon

flattens due to stimulation

thoracic cavity height

irritation of phrenic nerve - hiccups

external interocstal muscles

connected adjacent rivs

bow shaped lower ribs up and down

AP and lat diameters of thorax increased

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Quiet expiration -  passive process

diaphragm moves up

pressure in Aveoli rise

air pushed out

Forced Expiration - abdominal muscles contract 

intra abdominal pressure increased

diaphragm forced up 

air expelled actively from lungs

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Lung Volumes

Tidal volumes (TV) - air that enters or leaves at each breath

Inspiratory reserve volumes (IRV)

air taken in by maximum respiratory effort over and above a resting expiration

expiratory (ERV)

extra vol of air expired

residual volume (RV)

air left in lungs after deep expiration

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Lung Capacity Formulas

Lung capacity Formulas

Inspiratory Capacity (IC) max volume of air inhaled


Functional residual capacity (FRC)

volume of air left in lungs at the end of expiration FRC=RV + ERC

Vital Capacity (VC) - gas expelled by deepest expiration


Total lung capacity (YLC)

Vol of air held in system TLC=VC and RV

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Other Respiratory Function valves

Minute volume - air breathed per min

Fioced expiratory volume - gas expelled over time

Airway resistance - flow of air through a tube is raised by and increase in length

Peak expiratory flow rate maximal flow

Lung compliance

Inspired air - O2,N2,CO2,H2O - trace gases

Alveolar gases recieves CO2 from bloo

gives up to O2 to blood

Expired gas - same as atmospheric air

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Control of Ventilation

metabolic (automatic) - basic pattern

can be overidden (holding breath)

controller in brain stem

behavioural (voluntary)

Respiratory centre

medulla and pans contain groups of neurones

medulla- inspiratory centre (dorsal)

expiratory centre (ventra) - only included in forced expiration

Pneumatic centre

located in upper pans

controls breathing rate

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