Respiratory System

Course: B.Sc.(Biotech/Micro.) sem II

Subject: Animal & Plant Physiology

Unit 2.1

Respiratory system

Respiratory system is the organs in your body that helps your body that helps you breath. so you can deliver oxygen and take away carbondioxide.

Respiratory system is the organs in your body that helps your body that helps you breath. so you can deliver oxygen and take away carbondioxide.

Parts of respiratory system

1

Parts and functionsThe respiratory system extends from the nostrils to

the lungs.Nostrils- The opening through which air enters the

body.There are minute hairs and mucosa in the nostrils.They prevent the entry of dust and harmful germs into the lungs.

Nasal cavity-the chamber following the nostrils.It opens into the pharynx.

Epiglottis-The oesophagus and trachea start at the pharynx ,a common passage for food and air.So there is a chance for food to enter the trachea.it is the epiglottis that prevent this.

Trachea-Starts at the pharynx .It is made up of incomplete rings of cartilage.There are cilia and mucus in this.

Bronchi-Two branches of the trachea.Each open into a lung on each side.

Lungs-Two lungs found on either side of the heart in the the thoracic cavity.These are soft ,spongy,and elastic air bag.Lungs are lobular organs.The right lung has three lobes,the left has two lobes.

The branching network of bronchi,bronchioles, and alveoli constitute the lung.

Pleura-Double membrane covering the lung.There is a fluid between these membranes.The fluid reduces friction when the lungs contract and relax.

Bronchioles-Branches of the bronchi.carry air into the alveoli.

Alveoli-Each bronchiole ends in a group of alveoli.The lung is

made up of alveoli.There are blood capillaries covering the alveoli.Exchange of gases takesplace at the alveoli.The alveoli increase the surface area of the lungs,thus making exchange of gases efficient.

Diaphragm-It is the largest muscle of the body.

Respiratory system consists of

Nostrils Nasal cavity Pharynx

Trachea Bronchi Bronchioles

Alveoli 

The pathway of inspiration

Atmospheric air External nostrils Nasal cavity

Nasopharynx Larynx Trachea Bronchi Bronchioles Alveolar duct Alveoli.

The pathway of Expiration.Alveoli Alveolar ducts Broncioles Bronchi Trachea Larynx Nasopharynx

Nasal cavity External nostrils Atmospere.

The inflow and out flow of air between atmosphere and te alveoli of the lungs is called breathing

It is effected by the expansion and contraction of lungs.

During inspiration (inhalation), the diaphragm and intercostal muscles contract.

During exhalation, these muscles relax. The diaphragm domes upwards.

This results the pulling of the ribs upwards and outwards.

The inflow and out flow of air between atmosphere and te alveoli of the lungs is called breathing

It is effected by the expansion and contraction of lungs.

During inspiration (inhalation), the diaphragm and intercostal muscles contract.

During exhalation, these muscles relax. The diaphragm domes upwards.

This results the pulling of the ribs upwards and outwards.

Respiration: The Exchange of Gases

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MECHANISMS OF GAS EXCHANGE

• Gas exchange is the interchange of O2 and CO2 between an organism and its environment– It is also called respiration

Overview: Gas exchange involves breathing, the transport of gases, and the servicing of

tissue cells

• Gas exchange is essential because energy metabolism requires O2 and produces CO2

Animals exchange O2 and CO2 through moist body surfaces

• O2 enters an animal and CO2 leaves by diffusion through a respiratory surface – Respiratory surfaces are made up of living cells

The human respiratory system

• In humans and other mammals, air enters through the nasal cavity – It passes through the

pharynx and larynx into the trachea

– The trachea forks to form two bronchi

– Each bronchus branches into numerous bronchioles

The human respiratory system

• The bronchioles end in clusters of tiny sacs called alveoli

• Alveoli form the respiratory surface of the lungs– Oxygen diffuses

through the thin walls of the alveoli into the blood

Connection: Smoking is one of the deadliest assaults on our respiratory system

• Mucus and cilia in the respiratory passages protect the lungs– Pollutants, including

tobacco smoke, can destroy these protections

• Smoking kills about 430,000 Americans each year

Connection: Smoking is one of the deadliest assaults on our respiratory system

• Smoking causes lung cancer and contributes to heart disease

• Smoking also causes emphysema– Cigarette smoke

makes alveoli brittle, causing them to rupture

– This reduces thelungs’ capacity for gas exchange

Negative pressure breathing• Diaphragm moves down & expands chest cavity

pulls air into lungs

inhale exhale

3

Automatic Brain Control• You don’t have to think to breathe!– medulla & pons– measure blood pH• ↑CO2 = ↓pH (acid)

– coordinate breathing, heart rate & body’s need for energy

– Medulla oblongata will stimulate diaphragm to contract. 4

TRANSPORT OF GASES IN THE BODY

• Blood transports the respiratory gases, with hemoglobin carrying the oxygen

• The heart pumps oxygen-poor blood to the lungs– In the lungs it picks up O2 and drops off CO2(external respiration)

– In the tissues, cells pick up CO2 and drop off O2-(Internal respiration)

– Gases diffuse down pressure gradients in the lungs and the tissues

Gas exchange: Diffusion of gases• Gases move by diffusion

from high to low concentration– capillaries are thin-walled

tubes of circulatory system

– alveoli are thin-walled sacs of respiratory system

CO2

O2

CO2

O2

Gas exchange in the body

O2 Picked up by blood at the lungs must be transported to the tissues for cellular use

CO2 produced at tissues must be transported to the lungs for removal from the body

Pulmonarycirculation

Systemiccirculation

Alveoli

Atmospheric air

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Oxygen Transport in the Blood

Most O2 in the blood is transported bound to haemoglobin in the red blood cells

Normal O2 concentration in the arterial blood is about 20 ml/100 ml (200 ml per litre) at a normal arterial PO2 of 13.3 kPa and a normal haemoglobin concentration of 15 grams/100 ml

Percentage of O2 carried bound to haemoglobin = 98.5%

Percentage of O2 carried in the dissolved form = 1.5% (Plasma)

(3 ml per litre at a PO2 of 13.3 kPa )

O2 is present in the blood in two forms: (1) bound to haemoglobin (2) physically dissolved (very little O2)

Oxygen binding to haemoglobin

Haemoglobin can form a reversible combination with O2

Each Hb molecule contains 4 haem groups

Each haem group reversibly binds to one O2 molecule

Haemoglobin is considered fully saturated when all the Hb present is carrying its maximum O2 load

The PO2 is the primary factor which determine the percent saturation of haemoglobin with O2

Oxygen Haemoglobin Dissociation Curve

O2 c

on

cen

trat

ion

ml/

100

ml

5.3 13.3

Blood PO2 (kPa)

% H

aem

og

lob

in S

atu

rati

on

8.0

% H

b sa

tura

tion

0

100

O2 c

once

ntra

tion

(ml/1

00 m

l)

0

20

PO2 (kPa)

Total O2

O2 combined with Hb

Dissolved O 2

0 13

Oxygen Haemoglobin Dissociation Curve

Oxygen binding of haemoglobin

Binding of one O2 to Hb increases the affinity of Hb for O2

– co-operativity– Sigmoid

Flattens where all sites are becoming occupied

Factor effecting hemoglobin affinity

• pH• Partial pressure of co2• BPG: decreases the affinity of o2-hb

Bohr Effect

% H

b sa

tura

tion

PO2

PCO2

[H+]

Temperature2,3-Biphosphoglycerate

0

100

A shift of the curve to the right:- The Bohr Effect

Increased release of O2 by condit ions at the t issues

Means of CO2 Transport in the Blood

Solution (10%)

As Bicarbonate (60%)

As Carbamino compounds (30%)

(2) Bicarbonate: Most CO2 is transported in the blood as bicarbonate

Bicarbonate is formed in the blood by:-

CO2 + H2O H2CO3 H+ + HCO-3

CA

Carbonic AnhydraseOccurs in red-blood cells

(3) Carbamino Compounds

Carbamino compounds formed by combination of CO2 with terminal amine groups in blood proteins.

Especially globin of haemoglobin to give carbamino-haemoglobin

Rapid even without enzyme

Reduced Hb can bind more CO2 than HbO2

Summary of CO2 Transport in the Blood

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Hemoglobin helps transport CO2 and buffer the blood

• Hemoglobin helps buffer the pH of blood and carries some CO2

• Most CO2 in the blood combines with water to form carbonic acid– The carbonic acid breaks down

to form H+ ions and bicarbonate ions

– These help buffer the blood

Transport of CO2

• Most CO2 is transported to the lungs in the form of bicarbonate ions

Cell

carbondioxide formed by cellular respiration

To the tissue fluid

To the blood

By dissolving in the water of plasma

As bicarbonate by dissolvinginto the water of the red blood cells

As carbaminohaemoglobin by combining with haemoglobin

To the alveoli in the lungs To the outside through the nostrils

Breathing and Homeostasis• Homeostasis– keeping the internal environment of the

body balanced– need to balance O2 in and CO2 out

– need to balance energy (ATP) production

• Exercise– breathe faster

• need more ATP• bring in more O2 & remove more CO2

• Disease– poor lung or heart function = breathe faster

• need to work harder to bring in O2 & remove CO2

Disorders of the Respiratory system

• Asthma: a severe allergic reaction in which contraction of the bronchioles makes breathing difficult

• Bronchitis: an inflammation of the lining of the bronchial tubes. The passageways to the alveoli become swollen and clogged with mucus

• Emphysema: lungs lose their elasticity, deterioration of the lung structure

• Pneumonia: alveoli become filled with fluid. Caused by bacterial or viral infection

• Lung Cancer: a disease in which tumors form in the lungs as a result of irregular and uncontrolled cell growth

References:Image 1:

http://www.biologydiscussion.com/essay/human-respiratory-system-and-its-mechanism-with-diagram/1548

Image 2: http://kvhs.nbed.nb.ca/gallant/biology/mammalian_respiratory_system.html

Image 3: http://biology.stackexchange.com/questions/5466/what-is-the-inlet-outlet-speed-of-air-going-in-out-of-our-mouth-during-inhalatio

Image 4: http://postimg.org/image/ovtgngff7/

Image 5 & 6: Human Physiology(From cells to systems) by Lauralee Sherwood)

Book:

1. Human Physiology 4th edition by Lauralee Sherwood