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The Respiratory System I. (Chapter 22). Lecture # 8 Anatomy of the Respiratory System and Pulmonary Ventilation. Objectives. 1- State the functions of the respiratory system. 2- Name and describe the organs of this system. 3- Trace the flow of air from the nose to the pulmonary alveoli.

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slide1

The Respiratory System I

(Chapter 22)

Lecture # 8

Anatomy of the Respiratory System and Pulmonary Ventilation

Objectives

1- State the functions of the respiratory system.

2- Name and describe the organs of this system.

3- Trace the flow of air from the nose to the pulmonary alveoli.

4- Relate the function of any portion of the respiratory tract to its gross and microscopic anatomy.

5-Describe the brainstem centers that control breathing.

6- Explain how pressure gradients account for the flow of air in and out of the lungs, and how those gradients are produced.

7- Explain the significance of anatomical dead space to alveolar ventilation.

8- Define the clinical measurement of pulmonary volume and capacity.

slide2

Breathing represents life. The first breath of a newborn baby and the last gasp of a dying person are two of the most dramatic moments of human experience

Why do we breathe?

  • All our body processes directly or indirectly require ATP and ATP synthesis requires oxygen and produces carbon dioxide

O2

+

Food

CO2

+

H2O

+

We need to breathe to take in oxygen, and eliminate carbon dioxide

slide3

O2

CO2

  • The respiratory and cardiovascular systems work together to deliver oxygen to the tissues and remove carbon dioxide

Alveoli in lung

O2

CO2

  • They are often considered jointly as cardiopulmonary system. Disorders of lungs directly effect the heart and vise versa
  • The respiratory system and the urinary system collaborate to regulate the body’s acid base balance

Tissue cells

Excess of CO2 reacts with water and releases H+

-

+

H2O

H2CO3

HCO3

+

H+

CO2

O2

Food

CO2

H2O

slide4

Functions of Respiratory System

  • 1- O2 and CO2 exchange between blood and air

2- Speech and other vocalizations (laughing, crying)

3- It provides the sense of smell

4- It helps to control the pH of body fluids by eliminating CO2

  • 5- It helps to regulate blood pressure by synthesis of a vaso-constrictor called angiotensin II
  • 6- Breathing creates pressure gradients between thorax and abdomen that promote the flow of lymph and venous blood

7- Breath-holding helps expel abdominal contents during urination, defecation, and childbirth

slide5

Principal Organs of the Respiratory System

Nose

Pharynx

Larynx

Trachea

Lungs

Bronchi

slide6

The Nose

Anatomy of the Nasal Region

(a) External anatomy. (b) Connective tissues that shape the nose

slide7

The Nasal Cavity:

It is the internal chamber of the nose

The nasal cavity is divided into right and left halves (nasal fossae) by the nasal septum

NASAL SEPTUM

Perpendicular plate of ethmoid

Septal cartilage

Vomer

Middle nasal concha

Inferior nasal concha

slide8

The Nasal Cavity

Meatuses:

Functions of the nose

  • 1- It warms, cleanses, and humidifies inhaled air.

Superior

Nasal conchae:

Middle

  • 2- It detects odors in the airstream.

Inferior

  • 3- It serves as a resonating chamber that amplifies the voice.

Superior

Posterior nasal

aperture

Middle

Inferior

Vestibule

The respiratory epithelium lines the rest of nasal cavity except vestibule. It is a ciliated pseudostratified columnar epithelium with goblet cells.

slide9

The Pharynx

Posterior nasal

aperture

Pharynx:

Nasopharynx

It is a passageway for air

It is lined by a pseudostratified columnar epithelium

Oropharynx

Laryngopharynx

It is a passageway for air, food and drink

It is lined by a stratified squamous epithelium

It is a passageway for air, food and drink

Esophagus

It is lined by a stratified squamous epithelium

Larynx

Trachea

slide10

The Pharynx

Nasopharynx

  • (posterior to nasal apertures and above soft palate)

Pharyngeal tonsil

Auditory tube

Oropharynx

(space between soft palate and epiglottis)

Palatine tonsil

Laryngopharynx

  • (from the epiglottis to the cricoid cartilage)
slide11

The Larynx

It is a cartilaginous chamber about 4 cm (1.5 in.)

1- To keep food and drink out of the airway

Functions:

  • 2- Production of sound (phonation)

Epiglottis

Epiglottis

It closes the airway during swallowing

Hyoid bone

Epiglottic cartilage

Hyoid bone

Thyroid cartilage

Thyroid cartilage

Arytenoid cartilage

Corniculate cartilage

Vestibular fold

Vocal cord

Cricoid cartilage

Arytenoid cartilage

Cricoid cartilage

Trachea

Tracheal cartilage

(a) Anterior

(b) Posterior

(c) Median

slide12

The Larynx

Vestibular fold

They play no role in speech but close the larynx during swallowing

Vocal cord

(from the thyroid cartilage to the arytenoid cartilage)

They produce sound when air passes between them

Median

slide14

The Trachea

The trachea (windpipe) is a rigid tube about 12 cm (4.5 in.) long and 2.5 cm (1 in.) in diameter.

  • It is found anterior to the esophagus and it is supported by 16 to 20 C-shaped rings of hyaline cartilage, which reinforces the trachea and keeps it from collapsing when you inhale.

Trachea

Ciliated pseudostratified columnar epithelium with goblets cells

slide15

Mucociliary escalator

It is a mechanism that moves debris-laden mucus to the pharynx to be swallowed.

Epithelium:

Goblet cell

Ciliated cell

Mucus

Mucous gland

slide16

The Lungs

They are conical organs with a broad, concave base, resting on the diaphragm, and a blunt peak called the apex projecting slightly above the clavicle.

Apex of lung

Superior lobe

Costal surface

Superior lobe

Horizontal fissure

Middle lobe

Mediastinal surface

Oblique fissure

Oblique fissure

Inferior lobe

Inferior lobe

Diaphragmatic surface

Base of lung

slide17

Bronchial Tree

Thyroid

cartilage

All bronchi are lined with ciliated pseudostratified columnar epithelium.

Larynx

Cricoid

cartilage

  • The lamina propria has an abundance of mucous glands and lymphocyte nodules (bronchus-associated lymphoid tissue, BALT) positioned to intercept inhaled pathogens.

Trachea

Carina

Main bronchi

Superior lobar

bronchus

Superior lobar

bronchus

Middle lobar

bronchus

Inferior lobar

bronchus

Inferior lobar

bronchus

Segmental bronchi

Segmental bronchi

(8 on left)

(10 on right)

Bronchopulmonary segment:

It is a functionally independent unit of the lung tissue.

slide18

Conducting Division of Respiratory System

Main bronchus

(lung)

It consists of those passages that serve only for airflow:

1- Nostrils

2- Nasal cavity

3- Pharynx

4- Larynx

Lobar bronchus

5- Trachea

6- Main (primary) bronchi (lungs)

(lobe)

7- Lobar (secondary) bronchi (lobes)

8- Segmental (tertiary) bronchi (segments)

9- Bronchioles (lobules)

10- Terminal bronchioles (the final branches)

Bronchioles and terminal bronchioles lack of supportive cartilages)

Segmental bronchus

Respiratory Division of Respiratory System

(segment)

Bronchiole

(pulmonary lobule)

It consists of those structures that participate in gas exchange

Terminal bronchioles

1- Respiratory bronchioles

2- Alveolar duct

(final branches of conducting division)

3- Atrium

4- Alveoli

slide19

Pulmonary venule

Pulmonary arteriole

Openings of alveolar ducts

Bronchiole

Alveolar sac

Terminal bronchioles

Respiratory bronchioles

Every respiratory bronchiole divides into 2 to 10 alveolar ducts, which end in the alveolar sac

Alveoli

slide20

Pulmonary Alveoli

Fluid with surfactant

Squamous alveolar cell (type I)

Respiratory membrane

Great

alveolar

Cell (type II)

Capillary endothelial cell

  • They repair the alveolar epithelium when the squamous (type I) cells are damaged, and secrete pulmonary surfactant

Alveolar

macrophage

  • They are phagocytic cells that engulf invaders and activate the immune system
slide21

The Respiratory Membrane

Squamous alveolar cell

O2

O2

O2

Respiratory membrane

Shared basement membrane

Capillary endothelial cell

CO2

CO2

CO2

slide22

Epithelium Type Changes in the Respiratory System

Nasal cavity

Ciliated pseudostratified columnar epithelium

Nasopharynx

Ciliated pseudostratified columnar epithelium

Oropharynx

Stratified squamous epithelium

Laringopharynx

Stratified squamous epithelium

Larynx (superior part)

Stratified squamous epithelium

Larynx (inferior part)

Ciliated pseudostratified columnar epithelium

Trachea

Ciliated pseudostratified columnar epithelium

Bronchi

Ciliated pseudostratified columnar epithelium

Bronchioles

Ciliated simple columnar epithelium

Terminal bronchioles

Simple cuboidal epithelium

Alveoli

Simple squamous epithelium (with 5% of round or cuboidal cells (type II alveolar cells)

slide24

Neural Control of Breathing

No autorhythmic pacemaker cells for respiration, as in the heart, have been found.

The exact mechanism for setting the rhythm of respiration remains unknown, but we do know that breathing depends on repetitive stimuli of skeletal muscles from brain.

1- Neurons in medulla oblongata and pons control unconscious breathing, enabling us to breath without thinking about it.

Breathing is controlled at 2 levels of the brain.

2- The motor cortex provides voluntary control, enabling us to inhale or exhale at will.

Automatic, unconscious cycle of breathing is controlled by three pairs of respiratory centers in the reticular formation of the medulla oblongata and the pons.

  • 1- The ventral respiratory group (VRG)

Medulla oblongata

  • 2- The dorsal respiratory group (DRG)
  • 3- The pontine respiratory group (PRG)

Pons

slide25

Autonomic (Involuntary) Control of Breathing

Pontine respiratory group (PRG)

2

1

3

1

2

4

3

  • It modifies rhythm of the VRG by outputs to both the VRG and DRG.

It adapts breathing to special circumstances such as sleep, exercise, vocalization, and emotional responses

Ventral respiratory group (VRG)

  • It is the primary generator of the respiratory rhythm and produces a respiratory rhythm of 12 breath per minute.

Dorsal respiratory group (DRG)

  • It modifies the rate and depth of breathing. It receives influences from external sources:

They respond to the pH of the CSF, which reflex the CO2 level in the blood

A respiratory center on the pons

Chemosensitive center of the anterior medulla oblongata

They respond to the O2 and CO2 content and the pH of the blood

Chemoreceptors in the carotid and aortic bodies

Irritant receptors in the airway (they respond to smoke, dust, pollen, chemical fumes, cold air)

slide26

Voluntary Control of Breathing

The voluntary control over breathing originates in the motor cortex of frontal lobe of cerebrum. It sends impulses down corticospinal tracts to respiratory neurons in spinal cord, bypassing brainstem.

There are limits to voluntary control. A breaking point is reached when CO2 levels rise to a point when automatic controls override one’s will.

slide27

Pulmonary Ventilation

Pressure, Resistance, and Airflow

1- Pressure

The respiratory airflow is governed by the same principles of flow, pressure, and resistance as blood flow.

  • The flow of a fluid is directly proportional to the pressure difference between two points:

600 mm Hg

600 mm Hg

600 mm Hg

500 mm Hg

600 mm Hg

600 mm Hg

600 mm Hg

600 mm Hg

400 mm Hg

400 mm Hg

400 mm Hg

400 mm Hg

No flow

  • The flow of a fluid is inversely proportional to the resistance
slide28

Boyle’s Law:

At a constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume

757 mm Hg

760 mm Hg

763 mm Hg

  • If the lungs contain a quantity of a gas and the lung volume increases, their internal pressure (intrapulmonary pressure) falls
  • If the pressure falls below atmospheric pressure the air moves into the lungs

Inspiration

At rest

Expiration

Intra-pulmonary pressure

763 mm Hg

760 mm Hg

757 mm Hg

No flow

Atmospheric pressure

760 mm Hg

760 mm Hg

760 mm Hg

slide29

Pulmonary Ventilation:

It consists of the repetitive cycles of inspiration (inhaling) and expiration (exhaling).

Pressure-Volume Relationships in the Lungs

Volume

Volume

Pressure (757 mmHg)

Expiration

Inspiration

-3

+3

Air: 760 mmHg

Pressure (763 mmHg)

Intercostal muscles elevates the rib cage and diaphragm is contracted

Rib cage in normal position and diaphragm is relaxed

Boyle’s law: Pressure and volume are inversely proportional

slide30

Inspiration

Rib cage elevates and diaphragm contracts

Expiration

Rib cage returns to the normal position and diaphragm relaxes

slide32

2- Resistance

Pressure is one determinant of airflow and resistance is the other

  • The greater the resistance the slower the flow

Three factors influence the airway resistance:

  • 1- Diameter of the bronchioles
  • 2- Pulmonary compliance (the ease with which the lungs can expand)
  • 3- Surface tension of the alveoli and distal bronchioles
  • 1- Diameter of the bronchioles

Bronchodilation:

It is an increase in the diameter of a bronchus or bronchiole

  • Epinephrine and sympathetic stimulation stimulate bronchodilation and increase air flow

Bronchoconstriction:

It is a decrease in the diameter of a bronchus or bronchiole

  • Histamine, parasympathetic nerves, cold air, and chemical irritants stimulate bronchoconstriction
  • Suffocation from extreme bronchoconstriction brought about by anaphylactic shock and asthma
slide33

2- Pulmonary compliance (the ease with which the lungs can expand)

  • It determines the change in lung volume relative to a given pressure change. The thoracic cage expands normally but the lungs expand relatively little.
  • Pulmonary compliance reduced by degenerative lung diseases in which the lungs are stiffened by scar tissue (tuberculosis, black lung disease *).
  • 3- Surface tension of the alveoli and distal bronchioles

Water molecules in the alveolar epithelium are attracted to each other by hydrogen bonds, creating a surface tension.

Surface tension draws the walls of the alveoli inward toward the lumen and resisting the reinflation.

A surfactant is a substance produced by the great alveolar cells (type II cells) that disrupts the hydrogen bonds and allows the lungs to expand.

Premature infants often have a deficiency of pulmonary surfactant and experience great difficulty breathing.

The result is the “infant respiratory distress syndrome (IRDS), which is treated with artificial surfactant.

* Black lung disease is a chronic occupational lung disease contracted by the prolonged breathing of coal mine dust.

Black lung disease is also called anthracosis, black lung, black spittle, coal worker's pneumoconiosis, miner's asthma, pneumoconiosis, and silicosis.

slide34

Only air that enters the alveoli is available for gas exchange

But not all inhaled air gets there, about 150 mL fills the conducting division of the airway (anatomical dead space).

When a person inhales 500 mL of air, 150 mL stays in anatomical dead space, and 350 mL reaches alveoli.

In pulmonary diseases, some alveoli may be unable to exchange gases because they lack blood flow or there respiratory membrane has been thickened by edema or fibrosis.

Physiologic (total) dead space:

  • It is the sum of anatomic dead space and any pathological alveolar dead space.

Alveolar ventilation rate (AVR):

In a healthy person:

Anatomical dead space = Physiologic (total) dead space

  • It is the air that ventilates alveoli (350 mL) X respiratory rate (12 bpm) = 4200 mL/min.

The alveoli never completely empty during expiration.

Residual volume:

It is the air that cannot be exhaled with maximum effort (1300 mL).

slide35

Measurements of Ventilation

Spirometer

It is a device that recaptures expired breath and records such variables such as rate and depth of breathing, speed of expiration, and rate of oxygen consumption.

Respiratory Volumes

1- Tidal volume (TV):

It is volume of air inhaled and exhaled in one cycle during quiet breathing (500 mL).

2- Inspiratory reserve volume (IRV):

It is the air in excess of tidal volume that can be inhaled with maximum effort (3000 mL).

3- Expiratory reserve volume (ERV):

It is the air in excess of tidal volume that can be exhaled with maximum effort (1200 mL).

4- Residual volume (RV):

It is the air remaining in lungs after maximum expiration (1300 mL).

slide36

1- Tidal volume (TV):

It is volume of air inhaled and exhaled in one cycle during quiet breathing (500 mL)

2- Inspiratory reserve volume (IRV):

It is the air in excess of tidal volume that can be inhaled with maximum effort (3000 mL)

3- Expiratory reserve volume (ERV):

It is the air in excess of tidal volume that can be exhaled with maximum effort (1200 mL)

4- Residual volume (RV):

It is the air remaining in lungs after maximum expiration (1300 mL)

Maximum possible inspiration

2- Inspiratory reserve volume (IRV)

1- Tidal volume (TV)

3- Expiratory reserve volume (ERV)

Maximum voluntary

expiration

4- Residual volume (RV)

slide37

Pulmonary Capacities

1-Vital capacity (VT):

It is the total amount of air that can be inhaled and then exhaled with maximum effort (4700mL)

2-Inspiratory capacity (IC):

It is the maximum amount of air that can be inhaled after a normal tidal expiration (3500 mL)

3-Functional residual capacity (FRC):

It is the amount of air remaining in lungs after a normal tidal expiration (2500 mL)

4-Total lung capacity (TLC)

It is the maximum amount of air the lungs can contain

Maximum possible inspiration

2- Inspiratory reserve volume (IRV)

Inspiratory

capacity

Vital capacity

1- Tidal volume (TV)

Total lung capacity

3- Expiratory reserve volume (ERV)

Maximum voluntary

expiration

Functional residual

capacity

4- Residual volume (RV)