the Respiratory System 1

(Chapter 22)

Lecture # 8 Anatomy of the Respiratory System

and Pulmonary Ventilation

The Respiratory System I

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.

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

FoodO2+

CO2 H2O ++

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

Alveoli in lung

Tissue cells

O2

O2

FoodCO2

H2O

CO2

CO2

O2

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

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

Excess of CO2 reacts with water and releases H+

CO2 H2O + + H+HCO3

-H2CO3

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

Principal Organs of the Respiratory System

Trachea

Nose

Pharynx

Larynx

Lungs

Bronchi

The NoseAnatomy of the Nasal Region

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

NASAL SEPTUM

It is the internal chamber of the nose

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

Middle nasal concha

Inferior nasal concha

Vomer Perpendicular plate of ethmoid

The Nasal Cavity:

Septal cartilage

The Nasal Cavity

Nasal conchae:

Meatuses:

Superior

Middle

Inferior

Superior

Middle

Inferior

Vestibule

Functions of the nose

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

2- It detects odors in the airstream.

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

Posterior nasal

aperture

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

The Pharynx

EsophagusTrachea

Larynx

Posterior nasal

aperture

Nasopharynx

Oropharynx

Laryngopharynx

Pharynx:

It is a passageway for air

It is a passageway for air, food and drink

It is a passageway for air, food and drink

It is lined by a pseudostratified columnar epithelium

It is lined by a stratified squamous epithelium

It is lined by a stratified squamous epithelium

Nasopharynx

Oropharynx

Laryngopharynx

Pharyngeal tonsil

Auditory tube

Palatine tonsil

(posterior to nasal apertures and above soft palate)

(space between soft palate and epiglottis)

(from the epiglottis to the cricoid cartilage)

The Pharynx

The Larynx

(a) Anterior (b) Posterior (c) Median

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

Functions:1- To keep food and drink out of the airway

2- Production of sound (phonation)

Hyoid bone

Thyroid cartilage

Arytenoid cartilage

Cricoid cartilage

EpiglottisEpiglottis

Hyoid bone

Thyroid cartilage

Vestibular fold

Vocal cord

Arytenoid cartilage

Cricoid cartilage

Tracheal cartilage

Corniculate cartilage

It closes the airway during swallowing

Trachea

Epiglottic cartilage

Median

Vestibular foldThey play no role in speech but close the larynx during swallowing

Vocal cord

They produce sound when air passes between them

(from the thyroid cartilage to the arytenoid cartilage)

The Larynx

The TracheaThe 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

Mucociliary escalator

Epithelium:

Mucous gland

Ciliated cell

Goblet cell

Mucus

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

The LungsThey 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

Base of lung

Oblique fissure

Horizontal fissure

Oblique fissure

Superior lobe

Middle lobe

Inferior lobe

Superior lobe

Inferior lobe

Costal surface

Mediastinal surface

Diaphragmatic surface

Larynx

Trachea

Carina

Thyroidcartilage

Cricoidcartilage

Main bronchi

Superior lobarbronchus

Middle lobarbronchus

Inferior lobarbronchus

Superior lobarbronchus

Inferior lobarbronchus

Segmental bronchi(10 on right)

Segmental bronchi(8 on left)

Bronchopulmonary segment: It is a functionally independent unit of the lung tissue.

Bronchial TreeAll bronchi are lined with ciliated pseudostratified columnar epithelium.

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

Main bronchus

Lobar bronchus

Segmental bronchus

Bronchiole

(lung)

(lobe)

(segment)

(pulmonary lobule)

(final branches of conducting division)

Terminal bronchioles

Conducting Division of Respiratory System

1- Nostrils

It consists of those passages that serve only for airflow:

2- Nasal cavity3- Pharynx4- Larynx5- Trachea6- Main (primary) bronchi (lungs)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)

Respiratory Division of Respiratory System

1- Respiratory bronchioles 2- Alveolar duct

It consists of those structures that participate in gas exchange

3- Atrium4- Alveoli

Bronchiole


Respiratory bronchioles

Openings of alveolar ducts

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

Alveolar sac

Alveoli

Pulmonary arteriole

Pulmonary venule

Pulmonary Alveoli

Squamous alveolar cell

(type I)

Capillary endothelial

cell

Respiratory membrane

Fluid with surfactant

Alveolarmacrophage

Greatalveolar

Cell (type II)

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

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

The Respiratory Membrane

Squamous alveolar cell

Capillary endothelial

cell

Respiratory membrane

Shared basement membraneCO2 CO2 CO2

O2 O2 O2

Nasal cavity

Nasopharynx

Trachea

Bronchi

Bronchioles


Alveoli

Oropharynx

Laringopharynx

Ciliated pseudostratified columnar epithelium

Stratified squamous epithelium

Stratified squamous epithelium

Larynx (superior part) Stratified squamous epithelium

Larynx (inferior part)





Ciliated simple columnar epithelium

Simple cuboidal epithelium

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

Epithelium Type Changes in the Respiratory System

The Respiratory Muscles

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.

Breathing is controlled at 2 levels of the brain.

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

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)

2- The dorsal respiratory group (DRG)

3- The pontine respiratory group (PRG)

Medulla oblongata

Pons

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

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

Dorsal respiratory group (DRG)

2

1

3 A respiratory center on the pons

1

Chemosensitive center of the anterior medulla oblongata

2

Chemoreceptors in the carotid and aortic bodies

3

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

4

Pontine respiratory group (PRG)

Ventral respiratory group (VRG)

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

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

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

Autonomic (Involuntary) 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.

Voluntary Control of Breathing

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.

Pressure, Resistance, and Airflow

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

400 mm Hg

No flow

The flow of a fluid is inversely proportional to the resistance

600 mm Hg

400 mm Hg

600 mm Hg

400 mm Hg

600 mm Hg

400 mm Hg

1- Pressure

Pulmonary Ventilation

Expiration

Inspiration

Boyle’s Law:

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

763 mm Hg

760 mm Hg

757 mm Hg

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

760 mm Hg Atmospheric pressure

Intra-pulmonary pressure

No flow

At rest

760 mm Hg

757 mm Hg

760 mm Hg

763 mm Hg

760 mm Hg

Intercostal muscles elevates the rib cage and diaphragm

is contracted

Rib cage in normal position and diaphragm is relaxed

Volume Volume

Boyle’s law: Pressure and volume are inversely proportional

Pressure (757 mmHg)

Pressure (763 mmHg)

Air: 760 mmHg

Expiration Inspiration

Pressure-Volume Relationships in the Lungs

+3 -3

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

Inspiration

Expiration

Rib cage elevates and diaphragm contracts

Rib cage returns to the normal position and diaphragm relaxes

2- ResistancePressure is one determinant of airflow and resistance is the other

The greater the resistance the slower the flow

3- Surface tension of the alveoli and distal bronchioles

1- Diameter of the bronchioles

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

Three factors influence the airway resistance:

1- Diameter of the bronchioles

Bronchodilation:

Bronchoconstriction:

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

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

Histamine, parasympathetic nerves, cold air, and chemical irritants stimulate bronchoconstriction

Epinephrine and sympathetic stimulation stimulate bronchodilation and increase air flow

Suffocation from extreme bronchoconstriction brought about by anaphylactic shock and asthma

It determines the change in lung volume relative to a given pressure change. The thoracic cage expands normally but the lungs expand relatively little.

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

Pulmonary compliance reduced by degenerative lung diseases in which the lungs are stiffened by scar tissue (tuberculosis, black lung disease *).

* 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.

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.

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).

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:

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

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

In a healthy person: Anatomical dead space = Physiologic (total) dead space

Alveolar ventilation rate (AVR):

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).

Measurements of Ventilation

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.

Spirometer

Respiratory Volumes

1- Tidal volume (TV):

2- Inspiratory reserve volume (IRV):

3- Expiratory reserve volume (ERV):

4- Residual volume (RV):

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

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

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

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

1- Tidal volume (TV):

2- Inspiratory reserve volume (IRV):

3- Expiratory reserve volume (ERV):

4- Residual volume (RV):

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

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

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

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

1- Tidal volume (TV)

Maximum possible inspiration

2- Inspiratory reserve volume (IRV)

Maximum voluntaryexpiration

3- Expiratory reserve volume (ERV)

4- Residual volume (RV)

1-Vital capacity (VT):

2-Inspiratory capacity (IC):

3-Functional residual capacity (FRC):

4-Total lung capacity (TLC)

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

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

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

It is the maximum amount of air the lungs can contain

1- Tidal volume (TV)

Maximum possible inspiration

2- Inspiratory reserve volume (IRV)

Maximum voluntaryexpiration

3- Expiratory reserve volume (ERV)

4- Residual volume (RV)

Total lung capacity

Vital capacityInspiratorycapacity

Functional residualcapacity

Pulmonary Capacities

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the Respiratory System 1