Respiratory System

Learning Objectives To identify and describe 5 structures of the

respiratory system.

To describe the process of inspiration

To describe the process of expiration

Starter ActivityWrite a list of as many structures of the

respiratory system as you can.

IntroductionThe purpose of the respiratory system is to…

“bring the air we breathe into close contact with the blood so that oxygen can be absorbed and carbon dioxide

removed.” Basically it consists of: A pair of lungs

connected to the mouth via the trachea and bronchi.

The ribs and intercostal muscles of the chest which protect the lungs, trachea

and bronchi.

Respiratory SystemThe lungs are in the thoracic cavity and are also protected by 12 pairs of ribs that articulate with the vertebrae towards the back of the body. The sternum breastbone) is at the front of the rib cage.

Sternum

Cartilage

The portions of the ribs that articulate with the breastbone are made of cartilage rather than bone.

Cartilage is softer and more pliable than bone and this helps the movement of the rib cage during breathing.

Sets of antagonistic muscles are found between the ribs - the intercostal muscles.

This chest X-ray shows the organs within the thoracic cavity.

Air-filledlung

Ribs

Position of the diaphragm

Positionof

the heart

The Thoracic Cavity

Trachea(wind pipe)

Bronchus

Bronchioles

Alveoli

LungIntercostalmuscles

Ribs

Diaphragm

The Respiratory System

The trachea or windpipe is about 10 cm long and issupported by C-shaped rings of cartilage toprevent the tube from collapsing during breathing.The trachea

subdivides into the left and right bronchus.The bronchi arealso strengthenedby cartilage.The two bronchisubdivide to forman extensivenetwork ofBronchioles thatdeliver air to thegas exchangesurfaces – the alveoli.

Air enters the body through the nasal passages and

mouth, and passes via thepharynx and larynx

to the trachea.

Air is delivered tothe alveoli as thetrachea branchesinto bronchi and

bronchioles.

The respiratory system

The respiratory system

Worksheet – Identify and describe the different structures of the lungs

Functions of the respiratory system

1. Mechanism of breathing (inspiration and expiration)

2. Gaseous exchange

The Mechanism of Breathing

Lungs are NOT muscle

Lungs cannot move of

the own accord

They are

not co

ntrolle

d

by the

centr

al nerv

ous

system

So, how do they move when we

breath in and out?

The Key to Breathing is the Diaphragm and the intercostal

muscles between the Ribs

The Mechanism of Breathing

The nasal passages and lungsAir is drawn into the body via the nose or mouth. There are advantages to breathing through your nose:

Air then travels through the larynx, trachea (windpipe), bronchi (one bronchus to each lung) and bronchioles to the alveoli, where oxygen passes into the bloodstream.

the air is warmed so that it is closer to body temperaturetiny hairs and mucus in the nose filter the air, preventing larger dust and pollen particles reaching the alveolimucus moistens the air, making it easier for the alveoli to absorb.

When you breathe in:intercostal muscles between the ribs contract, pulling the chest walls up and outthe diaphragm muscle below the lungs contracts and flattens, increasing the size of the chestthe lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth.

Inspiration

Diaphragm contracts and moves down

Intercostal muscles pull ribs

up and out

ExpirationWhen you breathe out:

Intercostal muscles between the ribs relax so that the chest walls move in and down.The diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest. The lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth.

Diaphragm relaxes and bulges up

Ribs move in and down

Summary of respiratory system Air passes through the nose or mouth and then on to

the larynx. It carries on through the trachea. The trachea splits into tubes called bronchi (each

one is a bronchus) – one each going to the lungs. The bronchi split into progressively smaller tubes

called bronchioles. The bronchioles finally end at small bags called

alveoli (each one is an alveolus) where the gas exchange takes place.

Summary Task 1

List the following five words in the order that

breathed in air would go

through them

bronchi

larynx alveoli

trachea

bronchioles

Summary Question Time During exercise why is it

better to breath in through our nose rather than our mouths????

When air is breathed in through the nose, it is:1. Filtered by the hairs at the entrance to the nose and by mucus

which is a sticky substance.2. Warmed by blood vessels passing to the lining of the nose.3. Moistened by water vapour.The trachea and the bronchi also help get the air ready – they have tiny hairs and are covered in mucus helping to clean the air.