BAI GIANG HE HO HAP (respiratory system)

External and internal respiration • Properties of respiratory gases related to the diversity in structures of respiratory systems in animals • Physical basis of the transport of respirat

Respiratory system

Purves et al., Life: The Science of Biology

Respiratory system Key processes and concepts

• Function of the respiratory system The role of O2 in cellular respiration External and internal respiration

• Properties of respiratory gases related to the diversity in structures of respiratory systems in animals

• Physical basis of the transport of respiratory gases and lung ventilation: diffusion , bulk flow and related equations; ideal gas law, poiseuille's law, surface tension, partial pressure

• Structures of respiratory system in human: conducting zone, respiratory zone, alveolus, respiratory

membrane, pleural sac

• Lung ventilation and bulk flow: atmospheric pressure (Patm), alveoli pressure (Palv), negative intrapleural pressure (Pip)

– Respiratory muscles

– Lung compliance, pulmonary surfactant

• Gas exchange at the lungs and at the tissues –diffusion and partial pressure

• The transport of oxygen in the circulation , oxygen saturation of Hemoglobin, PO250

• Cacbonic anhydrase and the transport of CO2 in the circulation

• Control of respiration

Biochemical or Internal Respiration ( Hô hấp trong) versus

1 Internal respiration deals with converting food

energy to ATP.

2 External respiration deals with the mechanics

of moving oxygen from the atmosphere into the

lungs and to the tissues and with moving carbon

dioxide from the tissues and the lungs to the

atmosphere.

THE BIG PICTURE IN RESPIRATION

• Function is to maintain levels of CO2 and O2 in body tissues

• Homeostatic Systems help maintain ideal levels of O2 and CO2

Why living organism need Oxygen?

Why we need to breath constantly?

ATP

— each cell must make its own ATP

—ATP is not stored by cells

to any substantial extent

Nguồn: C.L Standfield 2011

ATP production

•aerobic catabolism:

1 Glucose + O2 -> 38 ATP + CO2 +H2O

•anaerobic glycolysis:

1 Glucose-> 2 ATP + lactic acid

The amount of ATP produced is nearly 20 times higher when O2 is present

http://www.windows2universe.org/physical_science/chemistry/oxygen_molecular.html

Properties of respiratory gases related to the diversity

in structures of respiratory systems in animals

• Percentages of CO2 and O2 in atmosphere

• Solubility of CO2 and O2 in fresh and in salt

water

• Concentration of CO2 and O2 in air and water

• Density of gases and water

Gases in Atmosphere:

–Nitrogen= 78%

–Oxygen= 21%

–Carbon Dioxide = 0.03%

Partial pressure

• Partial Pressure Definition and Units

• At sea level atmospheric pressure Patm= 760 mm Hg

Patm = PO2 + PN2 + PCO2

– PO2 = 760 mm Hg X 21% = 160 mm Hg.

– PN2= 760 x 78% =593 mm Hg

– PCO2= 760 x 0.03% = 0.23 mm Hg

Henry’s Law (calculating how much gas

can dissolve in a solution)

C = k x P

C= molar concentration of dissolved gas (moles/liter or mM/L)

P= partial pressure of gas (mm Hg)

k = solubility constant of gas in solvent (moles/liter mm Hg or mM/L mm Hg)

k = C/P

(solubility (k) = C (molar concentration of the gas) divided by P (partial pressure of the gas)

Oxygen Solubility: Air vs Water

Carbon Dioxide Solubility: Air vs Water

kair / kwater = 1.7

Solubility CO2 in Water / Solubility O2 in Water

0.03 / 0.0015 mM/LmmHg = 20

Air versus Water

1 Air has 209 ml oxygen/liter

2 Water has 6.6 ml oxygen/liter

3 Water is 1000 times more dense than air

Purves et al., Life: The Science of Biology

Bulk flow/convection and diffusion

0.5m

0.6m

0.0001m

0.0000 2m

Modified Fig 21.6 Hill at el, 2008

Diffusion- relies on thermal energy; efficient over short distances:

Bulk Flow (Q)/convection relies

on fluid pressure gradient;

Uses ATP to generate pressure gradient;

Works well over long distances

Purves et al., Life: The Science of Biology

Bulk flow and diffusion are both used in respiratory systems of all animals

to transport respiratory gases

• Secondary bronchi

• Tertiary bronchi

– respiratory zone

Trachea (Khí quản)

• 10-11 cm long, 2-2.5 cm in diameter, run parallel wit h and anterior to the esophagus

• 15-20 C-shaped bands of cartilage

•In the epithelium lining the conducting zone ( the larynx and the trachea, also bronchi but lesser extent):

− Goblet cells secret mucus trapping foreign particles in inhaled air

− Ciliated cells -> muscus escalator : cilia (hair

like projections of ciliated cells) vibrate to propel mucus containing trapped particles

−->glottis-> pharynx-> swallowed into esophagus

•Branches in to left and right bronchi surrounded

by cartilage rings

Conducting zone: conducts air from the larynx to the lungs

Respiratory zone: sites of gas exchange within the lungs

• 300 million alveoli in two lungs -> total surface of 100m2

• Alveolar pores allow equilibration of

pressure within the lung

Cross section of an alveolus

• Type I alveolar cells: epithelial cells making

up alveolar wall

• Type II alveolar cells produce pulmonary surfactant

• Respiratory membrane: site across which gas exchange occurs

(a) resin cast of pulmonary arteries and bronchi

(b) Scanning electro micrograph of capillaries around alveoli

Components of external respiration

1 Pulmonary/Lung ventilation (by bulk flow)

2 Respiratory gas exchange between lung air spaces and blood (by diffusion)

3 Respiratory gas transport between the lungs and the tissues (bulk flow)

4 Respiratory gas exchange between the blood and tissues (diffusion)

Lung ventilation

Pleura and intrapleural sac

/sac

Áp suất khoang màng phổi

Cơ hoành

Áp suất trong phổi/phế nang

túi màng phổi

lá thành

lá tạng

thành lồng ngực

Lung ventilation is driven by bulk flow

• Air (containing O2 and CO2) moves into and out of the lungs by bulk flow driven by pressure gradients

( P avl)

R

-ΔP: Patm-Pavl

-R: the resistance to the flow

Patm: atmospheric pressure

Pavl: intra-alveolar pressure

the ideal gas law

P = n RT

V

P : gas pressure (atm or mmHg )

n : the quantity of gas

R : universal gas constant

T : absolute temperature

V : the volume of gas (L)

When n, T are constant -> the pressure is inversely proportional to the volume of gas

to change Palv -> the volume of alveoli must

be changed

How to create the change in alveoli volume?

• Lungs are elastic and the changes in the volume

of the lungs/alveoli are generated by the changes

in the thoracic cavity

• The changes in the volume of the thoracic cavity

is created by respiratory muscles

• Respiratory muscles:

– Inspiratory muscles : Diaphragm (Cơ hoành), external intercostals (cơ liên sườn ngoài)

- Expiratory muscles : Internal intercostals (Cơ liên sườn

trong), abdominal muscles:

Actions of respiratory muscles generate changes in the volume of the lungs

Cơ hoành giãn

a loss of negative intrapleural pressure caused

collapsed lung

•Pneumothorax (Tràn khí màng phổi )

•Pleural effusion ( Tràn dịch màng phổi)

The change of alveolar pressure during a normal breath

Factors affect lung ventilation

Surface tension and the role of pulmonary surfactant in ventilation

• Thin film of water covers the alveoli make them like “ water bubbles” that are affected by surface tension

• Surface tension decreases the lungs’ compliance and pull the wall

of alveolus inward making it collapse

• Pulmonary Surfactant help maintain lungs’ tissue, keep them from collapsing during breathing, especially after exhalation

http://webcache.googleusercontent.com/search?q=cache:http://fusedglass.org/learn/project _tutorials/kiln_pressed_glass_surface_tension

Surface tension

Structure of Pulmonary Surfactant

ΔP: the pressure gradient between two

ends of the flowR: the total resistance to the flow

Airway resistance

• Airway radius (r)

– Sympathetic stimulation, adrenaline: bronchioles dilate (bronchodilation) – parasympathetic stimulation:

bronchoconstriction

– High CO2: bronchodilation, low CO2: bronchoconstriction

– Histamin: bronchoconstriction, mucus secretion

-> increases resistance

– Smoking – asthma (Hen): spastic contraction of bronchioles, increased mucus

secretion -acute/temporary

– COPD (Chronic Obstructive Pulmonary Disease) -Chronic-long lasting.

Measures lung volumes and air flow rates

pulmonary function

Nguồn: C.L Standfield 2011

Lung volumes

http://members.aol.com/Bio50/LecNotes/lecnot18.html

-TV (tidal volume (V T): the volume of air that moves into and out of the lungs during a single, unforced breath 500ml

-IRV (inspiratory reserve volume)- the maximum of air that can be inspired from the end of a normal inspiration -3000ml

-ERV (exspiratory reserve volume)- the maximum of air that can be expired from the end of a normal exspiration- 1000ml

-Residual volume (RV)- the volume of air remaining in the lungs after a maximum expiration- 1200ml

Lung capacities

• vital capacity – VC (Dung tích sống)

VC = TV + IRV + ERV thể tích khí thở ra hết sức sau khi đã hít vàohết sức: -> 4500 ml

• Total lung capacity-TLC (Tổng dung lượng phổi)

TLC = VC + RV -> 5700 ml

• Inspiratory capacity – IC (Dung lượng hít vào)

IC = TV + IRV –> 3500 ml

Lung volumes and capacities vary individually,

depending on age, sex, height of individual

• Minute ventilation-MV (Thể tích thông khí phút):

MV= RR x TV (12 x 500 = 6L/min) (RR: respiration rate: the number of breaths in a minute)

• Aveolar ventilation – AV (Thể tích thông khí phế nang- V A):

AV = RR x (TV- ADS) AV= 12 x (500 – 150) = 4.2 L

(ADS (Anatomical Dead Space -thể tích khí chết ) : volume of air contained

in the conducting zone – 150ml)

Aveolar ventilation (VE )

Pulmonary function tests

of a maximum exhalation after a maximum

inhalation

of the FVC that can be exhaled within a certain length of time (1 second-> FVC1)

if FVC1 < 80% -> a sign of obstructive pulmonary disease

Exchange of respiratory gases between lung air spaces and blood:

diffusion of O2 and CO2 across respiratory membranes

partial pressure gradients of O2 and CO2

PO2= 104 mmHg PO2 = 40 mmHg

Nguồn: cải biên từ C.L Standfield 2011

Gas moves down its partial pressure (PP) gradient from areas of

higher PP to areas of lower PP

• at the lungs:

P O2 alv (100 mmHg) > PO2 capillary (40 mmHg)  O2 moves into the blood

P CO2 alv (40 mmHg) < P CO2 capillary (46mmHg)  CO2 moves into the alveoli

• at the tissues:

PO2capillary (100 mmHg) < P O2 interstitialfluid (40mmHg)  O2moves into interstitial fluid

P CO2 capillary (40 mmHg)< P CO2 interstitialfluid(46 mmHg)  CO2moves into the capillary

 Exchange of respiratory gases occurs in the respiratory bronchioles and in the alveoli

respiratory membrane

J = rate of diffusion in ml or cm3/sec:

J = K x A(P2 - P1)/D

•K = diffusion constant or cm2/sec-mm Hg

•A = area over which diffusion occurs (cm2)

•P2 - P1 = partial pressure gradient (mm Hg or KPa)

•D= distance over which diffusion occurs (cm)

PO2= 104 mmHg PO2 = 40 mmHg

Nguồn: cải biên từ C.L

Standfield 2011

PO2 = 100 mmHg

-Smoking -Pulmonary Edema

Determinants for the rate of diffusion of respiratory gases

Gas transport by the circulation

The transport of Oxygen- Role of Hemoglobin

Increases solubility of oxygen (1 gram Hb holds 1.3 ml of oxygen)

 Without Hemoglobin: 3 ml of oxygen/ liter of blood (if PO2 = 100 mmHg)

– If metabolic rate = 250 ml O2/min at rest, then you would need a cardiac output of

80 L/min to satisfy O2 demands of the body

– Hemoglobin increases solubility of oxygen since 1 gram of

hemoglobin holds 1.3 ml of oxygen

– In blood there is an average of 150 g of hemoglobin/liter of blood and therefore 1liter of blood can hold 200 ml of oxygen

 With Hemoglobin: 200 ml of oxygen/ liter of blood

Hemoglobin-oxygen dissociation curve

http://quizlet.com/13880525/familiarize/embedv2?&m

Definition of PO2 50

• This is the partial pressure of oxygen at which

O2

– The higher the PO2 50 the lower the affinity of

hemoglobin for oxygen.

– The lower the PO2 50 the higher the affinity of

hemoglobin for oxygen.

- at tissues: creased metabolic activity -> ↑ CO2 -> ↓pH -> ↑ PO2

50 -> affinity of Hb for O2 ↓ -> O2 is released

- at the lungs: pH ↑ ->

↓ PO2 50 -> affinity of

Hb for O2 ↑ -> O2 binds to Hb easily

Effects of temperature and pH on hemoglobin

association curve

Bohr effect

CARBON DIOXIDE TRANSPORT

• Dissolved CO2: 4 – 7%

• Bound to Hemoglobin (carbaminohaemoglobin) : 23%

• BICARBONATE IONS (HCO3- ) in red blood cells: 70%

-Cacbonic anhydrase

• Haldane effect: Po2 rises -> increased CO2 unloading

Cacbonic anhydarse (CA)

CO2 + H2O < > H2CO3 < > H+ +

HCO3-• CO2 is converted to other form ->maintain pCO2

gradient -> increase CO2 solubility

•Maintain plasma pH

CA

At the tissues

At the lungs

Control of Respiration

Chemoreceptors

•peripheral chemoreceptor:

PO2<60mmHg, PCO2, H+

End-of- chapter questions

1.What is the major function of the respiratory system?

Why living organisms need Oxygen?

Why do we need to breath constantly?

Briefly describe the respiratory system and its integration with other organs/systems to function as

a homeostasis system for plasma O2 and CO2 concentrations

2 Physical basis of the transport of respiratory gases in the respiratory system?

How does the pulmonary/lung ventilation in human body occur ?

3.What are the main factors that maintain lung ventilation or keep the lungs from collapsing during

breathing?

4 Respiratory gases and their properties related to the diversity in form of respiratory systems in

animals How is O2 transported in the blood, why do we need hemoglobin?

5 List some common causes (at least 5) of abnormal lung ventilation/breathing discuss and explain

how this abnormality occurs using physical rules or/and control mechanisms applied to respiratory system.

6 How does gas exchange occur in the lungs and in the tissues?

What are the main factors that affect this gas exchange?

7 How is CO2 transported in the blood? What are the advantages when CO2 is “indirectly”

transported by Hemoglobin?

8 What is main factor that determine airway resistance? How airway resistance would affect lung

ventilation?