chapter 1 scs f3

7/31/2019 Chapter 1 Scs f3

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1.1 HUMAN BREATHING

MECHANISM



Structure of The Respiratory System

NostrilsAir breathed in through the

nostrils passes into the lungs

through the trachea

TracheaIt is a strong tube with

incomplete rings of cartilage

to prevent it from collapsing

when it bends.

RibsEnclose and protect the

lungs and the heart

BronchiolesAre tiny air tubes which branch

from the bronchi. Each bronchioleands in air sacs called alveoli.

BronchiThese are branches of the trachea.

Each bronchus leads into one lung.

LungsEach lung is enclosed by two pleural

membranes. The right lung has three

lobes while the left lung has two.

DiaphragmA large sheet of muscle. Its

contraction and relaxation increases

and decreases the volume of the

thoracic cavity

Alveolus(S)

Alveoli (P)



Structure of The lung

Characteristics of Alveolus:

•Has a one cell thick wall.

•moisture

•They are surrounded by

blood capillaries.

•Exchange of oxygen and

carbon dioxide in the lungs

takes place here.



Mechanism of breathing

Breathing is a mechanical process which draws air into and out of the lungs.



The external intercostals muscles

contract.The ribs are raise.

The diaphragm muscles contract.

The sheet of diaphragm flattens.

The volume of the thoracic cavity

increases.

The air pressure in the thoracic cavity

decreases.

Air from outside the body moves into

the lungs.



The external intercostals muscles

relax.

The ribs are lowered.

The diaphragm muscles relax.

The sheet of diaphragm arches

upwards.

The volume of the thoracic cavity

decreases.

The air pressure in the thoracic cavity

increases.

Air is forced out of the lungs.



Models to show the breathing

mechanism

ExhalationInhalation



1.2 TRANSPORT OF

OXYGEN IN THE HUMAN BODY



Lungs Body cells Heart

Oxygen in the

lungs diffuses intothe blood and

combine with

haemoglobin in the

red blood cells to

form

oxyhaemoglobin.

The blood is now

called oxygenated

blood.

Oxygen +

haemoglobin

oxyhaemoglobin

The oxygenated

blood is transport tothe heart.

Then the heart

pumps the

oxygenated blood to

all parts of the body

except the lungs.

The oxygenated

blood carried in the

capillaries to the

body cells.

The oxygen in the

oxyhaemoglobin

diffuses into the

cells.

Oxyhaemoglobin

oxygen +haemoglobin

Carbon dioxide in

the cells diffuses

into capillaries

(because there ismore carbon dioxide

in the cells than in

the blood in the

capillaries)

The blood rich in

carbon dioxide is

The deoxygenated

blood is returned to

the heart by veins.

From the heart,the deoxygenated

blood pumps along

arteries to the lungs.

The deoxygenated

blood releases its

carbon dioxide intoalveoli by diffusion.

The blood absorbs

oxygen from the air

in the alveoli by

diffusion to form

oxyhaemoglobina ain.

Pulmonaryveins

Aorta

VenacavaPulmo

naryartery



1.3 THE IMPORTANCE

OF A HEALTHY RESPIRATORY SYSTEM

chapter 1 scs f3

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