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Respiratory systemL1

Faisal I. Mohammed, MD, PhD

University of Jordan

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Recognize the Functions of the respiratory system.

Understand Mechanism of Inspiration and Expiration.

Recognize Surface tension and role of Surfactant.

Understand Pressure and Volume Changes During Breathing.

I. Pulmonary ventilation *1.Mechanisms of pulmonary ventilation2.Indexes of pulmonary ventilation function

II. Pulmonary gas exchange and Tissue gas exchange1. Principles of gas exchange *2. Pulmonary gas exchange *3. Tissue gas exchange

III. Gas transport in the Blood1. Transport forms of oxygen and carbon dioxide in the blood2. Oxygen transport *3. Carbon dioxide transport *

IV. Respiratory Regulation1. Respiratory centers and formation of respiratory rhythm 2. Reflex regulation of respiration *

V. Role of the lungs in regulation of acid-base balance

The objectives will be met through The objectives will be met through

Overview of lung function Overview of lung function and structureand structure

Lung Functions Lungs are a site for gas exchange with the

external environment. Regulate acid-base balance. Lungs have a defense mechanism. Lungs are a blood reservoir. Serve a biosynthetic function (Angiotensin II,

surfactant)

Respiratory component element Respiration is the exchange of gas between the body and the Respiration is the exchange of gas between the body and the

environment.environment. External respiration : the exchange of gases between pulmonary blood External respiration : the exchange of gases between pulmonary blood

and the external environment, which involves not only diffusion and the external environment, which involves not only diffusion across the lung capillaries across the lung capillaries （（ pulmonary gas exchange, but also the pulmonary gas exchange, but also the bulk movement of gases in and out of the lungs (pulmonary bulk movement of gases in and out of the lungs (pulmonary ventilation). ventilation).

Internal respiration : the exchange of gases between the tissue cells Internal respiration : the exchange of gases between the tissue cells and the systemic capillaries. The diffusion of gases between the and the systemic capillaries. The diffusion of gases between the interstitial fluid and the cytoplasm.interstitial fluid and the cytoplasm.

Gas transport in the blood : physical solvation and chemical Gas transport in the blood : physical solvation and chemical constitution. constitution.

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Structures of the Respiratory System

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Respiratory Zone

Region of gas exchange between air and blood.

Includes respiratory bronchioles and alveolar sacs.

Must contain alveoli.

Conducting Zone All the structures air

passes through before reaching the respiratory zone.

Warms and humidifies inspired air.

Filters and cleans: Mucus secreted to trap

particles in the inspired air.

Mucus moved by cilia to be expectorated.

Insert fig. 16.5

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Microscopic Anatomy of Lobule of Lungs

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Alveoli

Cup-shaped outpouching Alveolar sac – 2 or more alveoli sharing a common

opening 2 types of alveolar epithelial cells

Type I alveolar cells – form nearly continuous lining, more numerous than type II, main site of gas exchange

Type II alveolar cells (septal cells) – free surfaces contain microvilli, secrete alveolar fluid (surfactant reduces tendency to collapse)

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Components of Alveolus

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Pneumocytes I and pneumocytes II

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Pulmonary ventilation

Respiration (gas exchange) steps1. Pulmonary ventilation/ breathing

Inhalation and exhalation Exchange of air between atmosphere and alveoli

2. External (pulmonary) respiration Exchange of gases between alveoli and blood

3. Internal (tissue) respiration Exchange of gases between systemic capillaries and tissue

cells Supplies cellular respiration (makes ATP)

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Inhalation/ inspiration

Pressure inside alveoli lust become lower than atmospheric pressure for air to flow into lungs 760 millimeters of mercury (mmHg) or 1

atmosphere (1 atm) Achieved by increasing size of lungs

Boyle’s Law – pressure of a gas in a closed container is inversely proportional to the volume of the container

Inhalation – lungs must expand, increasing lung volume, decreasing pressure below atmospheric pressure

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Boyle’s Law

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Inhalation Inhalation is active – Contraction of

Diaphragm – most important muscle of inhalation Flattens, lowering dome when contracted Responsible for 75% of air entering lungs during normal quiet

breathing External intercostals

Contraction elevates ribs 25% of air entering lungs during normal quiet breathing

Accessory muscles for deep, forceful inhalation When thorax expands, parietal and visceral pleurae adhere tightly due to

subatmospheric pressure and surface tension – pulled along with expanding thorax

As lung volume increases, alveolar (intrapulmonic) pressure drops

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Exhalation/ expiration

Pressure in lungs greater than atmospheric pressure Normally passive – muscle relax instead of contract

Based on elastic recoil of chest wall and lungs from elastic fibers and surface tension of alveolar fluid

Diaphragm relaxes and become dome shaped External intercostals relax and ribs drop down

Exhalation only active during forceful breathing

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Diaphragm is the main muscle of Diaphragm is the main muscle of inspirationinspiration

Dome-shaped

InspirationInspiration

ExpirationExpiration

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Thank YouThank You

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