FUNCTION OF THE RESPIRATORY SYSTEM (ANH văn CHUYÊN NGÀNH y)

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FUNCTION OF THE

RESPIRATORY SYSTEM

1 Pulmonary ventilation: air moves into and out of the lungs

2 External respiration: gas exchange in the

THE CONDUCTING ZONE

Moistens and warms entering air

1 Respiratory mucosa -> mucous glands ->

watery mucus -> moistened fluid

2 Rich plexus of capillaries & thin walled

veins: warms the air

CLEAN INSPIRED AIR

1 Nasal hair

• Anterior nasal passage

• Filtered dust, large practicles

2 Mucus

• Lysozymes: anti-bacterial enzymes

• Defensisns: Natural antibiotic

• Sticky fluids: Physically trap dust, debris…

3 Current of Cilia

• Movements of ciliated cells -> move the sheet of

mucous toward the throat -> swallow and digest

4 Mucosa

• Sensory nerve endings -> sneeze reflex

as the nose

Waldeyer's tonsillar ring

1 Lipoprotein

2 Made by pneumocytes type II

3 Produced in 38-42 weeks gestation -> infant

respiratory distress syndrome

4 Functions:

• Reduction in collapse of underinflated alveoli

(atelectasis)

• Distribution of ventilation among alveolus

• Help inflate the alveoli

• Prevent fluid from entering the alveoli

MACHENICS OF BREATHING

Inhalation Exhalation

Initiator Diaphragm Alveolar recoil

Associated muscles External Intercostal

muscles Intrapleural pressure -6mmHg

Forced: -30 mmHg

-2,5 mmHg Forced: -0,5 – 0 mmHg Lung volume Increase Decrease

Associated muscle in

forced action

Sternocleidomastoid

muscle Scalene muscle Pectoralis muscle

Oblique muscle Rectus muscle Internal Intercostal

muscle

LUNG VOLUME AND CAPACITIES Lung volume: Amounts of air that can be

measured

Lung capacity: Summing of many lung volumes

MINUTE VENTILATION and ALVEOLAR VENTILATION

V/Q MISMATCH

Have you ever

our lungs?

GAS EXCHANGE IN THE

LUNGS

• In the lungs, oxygen and carbon dioxide (a waste product of body processes) are exchanged in the tiny air sacs (alveoli) at the end

of the bronchial tubes The

alveoli are surrounded by

capillaries When a person

inhales, oxygen moves from the alveoli to the surrounding

capillaries and into the

bloodstream At the same time, carbon dioxide moves from the bloodstream to the capillaries and into the alveoli The carbon dioxide is removed from the

lungs when a person exhales.

Gases are exchanged between the alveolar air and the blood by diffusion, the movement of molecules from an area of higher concentration to an area of lower concentration, where concentration refers to how much of one substance is present in a mixture of substances The rate of diffusion

is influenced by a variety of factors, including atmospheric pressure and the magnitude of the concentration gradient of the diffusing substance

In the lung:

• à  PO2 in the alveolar air  is higher than  blood

• à O2 diffuse rapidly from alveolus

• à  to blood plasma.

In the peripheral tissues:

• à  PO2 is lower than  blood

• à  O2 diffuses out from blood

• à  to tissues

In the lungs.

• à  PCO2 is lower than in the  blood.

• à CO2 diffuses out

• à  into alveoli.

Blood carries CO2 in 3 forms:

•   dissolved gas (8%)

•    HCO 3 - ion in the plasma (73%)

•   carbamino haemoglobin in the red blood cells (19%)

A large amount of CO2

•    combines with H 2 O  in the red blood

cells (RBC)

•   to form carbonic acid (H 2 CO 3 )

•    then ionizes to form H ++ HCO 3

HCO 3 - from the red blood cell:

•   diffuse out into the plasma.

•   loss of negatively charge

HCO3-  from the red blood cell

•    balanced by the inward diffusion of -ve chloride ions (Cl- ) =  chloride shift.

• O2  = transported by the haemoglobin molecule in the red blood cells.

•   Each haemoglobin molecule à carries 4 mol of O2. Each polypeptide chain contains: 2 subunits of alpha polypeptides chains and 2 subunits

of beta polypeptides chains.

•  When one mol of O 2  binds to one of the  haem group in the haemoglobin

à  produces a conformational change in that subunit

à concerted conformational change of the subunits

à  resulting in sigmoid shape for the O2 dissociation curve of the haemoglobin.

 The cooperative effect is reversible

à when one subunit of oxyhaemoglobin unloads its O2,

à other three quickly follow suit

à conformational change

à lowers its affinity for O2

The O2 dissociation curve shows:

- when haemoglobin is exposed to a gradual increase of PO2,

- it absorbs O2 rapidly at first

- but more slowly as the PO2 continues to rise.

The % of O2 saturation of haemoglobin = 95%

- when blood flows through the lungs (PO2 = 105 mmHg).

The % of O2 saturation of haemoglobin = 70%

- when blood flows through a moderately active/resting muscle

(PO2=40 mmHg).

As the blood from the lungs reaches the muscle at rest:

- 25% of the O2 carried in the heamoglobin is unloaded to the

surrounding tissues

- for cellular respiration.

- 70% of the oxygen is still retained by the haemoglobin.

REGULATION OF RESPIRATION

• Breathing is controlled by the central neuronal

network to meet the metabolic demands of the

body

• A collection of funtionally similar neurons that help

to regulate the respiratory movement are present

in the medulla region of the brain They are called the Respiratory center

• Dorsal respiratory group (medulla) – mainly causes inspiration.

• Ventral respiratory group (mesulla) – causes either expiration or inspiration

• Pneumotaxic center ( upper pons) inhibits apneustic center & inhibits inspiration, helps control the rate and pattern of

breathing

• Apneustic center (lower pons ) – to

promote inspiration