The Respiratory System I: Anatomy Functions of the Respiratory System The Nasal Cavity and Sinuses...

The Respiratory System I: Anatomy Functions of the Respiratory

System

The Nasal Cavity and Sinuses

Pharynx, Larynx, & Trachea

Respiratory Mucosa

Lungs: Lobes, Bronchioles, & Alveoli

Mechanics of Breathing

• Pressure Relationships

• Inspiration and Expiration

• Lung Compliance

Respiration Pulmonary ventilation (breathing):

movement of air into and outof the lungs

External respiration: O2 and CO2

exchange between the lungsand the blood

Transport: O2 and CO2

in the blood

Internal respiration: O2 and CO2

exchange between systemic bloodvessels and tissues

Respiratorysystem

Circulatorysystem

Organs of the Respiratory systemKey Functions

Pulmonary ventilation

External respiration

Respiratory gas transport

Internal respiration

External intercostals

Functional Anatomy Respiratory zone: site of gas exchange

• Microscopic structures: respiratory bronchioles, alveolar ducts, and alveoli

Conducting zone: conduits to gas exchange sites

• Includes all other respiratory structures

Respiratory muscles: diaphragm and other muscles that promote ventilation

The Respiratory System I: Anatomy Functions of the Respiratory System



Respiratory Mucosa





• Lung Compliance

Figure 22.3c

Sphenoid sinus Frontal sinus

Nasal meatuses(superior, middle,and inferior)

Nasopharynx

Uvula

Palatine tonsilIsthmus of thefauces

Posterior nasalaperture

Opening ofpharyngotympanictube

Pharyngeal tonsil

Oropharynx

Laryngopharynx

Vocal fold

Esophagus

(c) Illustration

Nasal conchae(superior, middle and inferior)

Nasal vestibuleNostril

Nasal cavity

Hard palate

Soft palate

Tongue

Lingual tonsil

Epiglottis

Hyoid boneLarynx

Thyroid cartilageVestibular fold

Cricoid cartilage

Thyroid glandTrachea

Cribriform plateof ethmoid bone

Upper Respiratory Tract

Anatomy of the Nasal Cavity

hard palate soft palate

Function of conchae (projections from lateral walls)

• Increase surface area

• Increases air turbulence within the nasal cavity

Nasal cavity is separated from the oral cavity by the palate

• Anterior hard palate (bone) and posterior soft palate (muscle)

Function of the sinuses

• Lighten the skull

• Act as resonance chambers for speech

• Produce mucus that drains into the nasal cavity

• Cavities within bones surrounding the nasal cavity: frontal, sphenoid, ethmoid, maxillary bones

Function of respiratory mucosa in nasal cavity

• Moistens and heats air so lungs are not dehydrated nor cool the body’s core; cools it on way out

• Traps incoming foreign particles




Respiratory Mucosa





• Lung Compliance

Pharynx (Throat) Muscular passage from nasal cavity to larynx

Three regions of the pharynx

• Nasopharynx – superior region behind nasal cavity- pseudostratified col. epith.

• Oropharynx – middle region behind mouth, stratified squamous epithelium

• Laryngopharynx – inferior region attached to larynx

The oropharynx and laryngopharynx are common passageways for air and food

Auditory tubes enter the nasopharynx

Tonsils of the pharynx

• Pharyngeal tonsil (adenoids) in the nasopharynx

• Palatine tonsils in the oropharynx

• Lingual tonsils at the base of the tongue

Figure 22.3b

Larynx (Voice Box) Function: Routes air and food into

proper channels

Plays a role in speech

Made of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage (epiglottis)

Structures of the Larynx

• Thyroid cartilage

o Largest hyaline cartilage

o Protrudes anteriorly (Adam’s apple)

• Epiglottis

o Superior opening of the larynx

o Routes food to the esophagus and air toward the trachea

o Vocal cords (vocal folds)

o Glottis – opening between vocal cords

Respiratory Mucosa or Epithelium Nasal Cavity and Pharynx

• Pseudostratified ciliated columnar epithelium

• Superficial to the lamina propria of connective tissue

• Mucous secretions from goblet cells contain lysozyme and defensins

• Cilia in the nasal cavity move contaminated mucus posteriorly to throat; tracheal cilia move mucus upward into pharynx

• Bronchi have cartilaginous reinforcement

Trachea & Bronchi


• Cartilaginous support of hyaline cartilage deep to the lamina propria

Bronchioles

• Simple cuboidal epithelium and cartilage

Alveoli

• Simple squamous epithelium

Trachea (Windpipe) Connects larynx with

bronchi

Lined with ciliated mucosa

• Beat continuously in the opposite direction of incoming air

• Expel mucus loaded with dust and other debris away from lungs

Walls are reinforced with C-shaped hyaline cartilage

Figure 22.6b

(b) Photomicrograph of the tracheal wall (320x)

Hyaline cartilage

• Lamina propria (connective tissue)Submucosa

Mucosa

Seromucous glandin submucosa





Respiratory Mucosa





• Lung Compliance

Lungs Occupy most of the thoracic

cavity

• Apex is near the clavicle (superior portion)

o Base rests on the diaphragm (inferior portion)

• Each lung is divided into lobes by fissures

o Left lung – two lobes

o Right lung – three lobes

Diaphragm

Lungs: Primary Bronchi Formed by division of the trachea

Enters the lung at the hilus (medial depression)

Right bronchus is wider, shorter, and straighter than left

More likely to get infections in right lung than left

Bronchi subdivide into smaller and smaller branches (with rings)

Lungs: Linings (Pleura)

• Thin, double-layered serosa

• Pleural fluid provides lubrication and surface tension

Respiratory Tree Divisions Primary bronchi

Secondary bronchi

Tertiary bronchi

Bronchioles

Bronchioles

Bronchioles end in terminal bronchioli

• All but the smallest branches have reinforcing cartilage

• Lined with simple cuboidal epithelium

Terminal bronchioles end in alveoli

Figure 22.9a

Elasticfibers

Smoothmuscle

Alveolus

Capillaries

Terminal bronchiole

Respiratory bronchiole

Capillaries Surround Alveoli to Pick Up O2 and Deliver CO2

Figure 22.8b

(b)

Alveolarpores

Alveolarduct

Respiratorybronchiole

Alveoli

Alveolarsac

Figure 22.9c

Capillary

Type II (surfactant-secreting) cell

Type I cellof alveolar wall

Endothelial cell nucleusMacrophage

Alveoli (gas-filledair spaces)

Red blood cellin capillary

Alveolar pore

Capillary endothelium

Fused basement membranes of the alveolar epitheliumand the capillary endothelium

Alveolar epithelium

Respiratorymembrane

Red blood cell

O2

AlveolusCO2

Capillary

Alveolus

Type II cells also secrete antimicrobial proteins

Alveolar Structure and Cellular Composition(The Respiratory Membrane)

Nucleus of type I(squamousepithelial) cell

External respiration: O2 and CO2 flow easily down their concentration gradients, into and out of alveoli across thin, simple squamous epithelium




Respiratory Mucosa





• Lung Compliance

Pressure Relationships in the Thoracic Cavity

Respiratory pressures are described relative to Patm

• A negative respiratory pressure is less than Patm

• A positive respiratory pressure is greater than Patm

• Zero respiratory pressure = Patm = 760 Hg at sea level

Intrapulmonary and Intrapleural Pressures Intrapulmonary (intra-alveolar) pressure (Ppul)

• Pressure in the alveoli

• Fluctuates with breathing

• Always eventually equalizes with Patm

Intrapleural pressure (Pip):

• Pressure in the pleural cavity that fluctuates with breathing

• Expressed as a negative pressure (less than Patm and Ppul), caused by opposing forces:

• Elastic lung recoil and alveolar surface tension are forces that promote lung collapse (when Pip = Ppul, lungs collapse)

• Elasticity of the chest wall pulls the thorax outward; promotes lung expansion

Figure 22.12

Atmospheric pressure

Intrapleuralpressure756 mm Hg(–4 mm Hg)

Transpulmonarypressure760 mm Hg –756 mm Hg= 4 mm Hg

Thoracic wall

DiaphragmLung

Intrapulmonarypressure 760 mm Hg(Relative to Patm= 0 mm Hg)

Parietal pleura

Pleural cavityVisceral pleura

756

760

Lungs are Inflated if Transpulmonary Pressure > 0




Respiratory Mucosa





• Lung Compliance

Pulmonary Ventilation: Expanding and Contracting the Lungs

Subdivided into inspiration and expiration

• Mechanical processes that depend on volume changes in the thoracic cavity

• Can use Boyle’s Law to understand

• P1V1 = P2V2

• Volume changes cause pressure changes

• If the volume of the lungs increases, the air pressure within them decreases

• Pressure changes cause gases flow to equalize pressure

Figure 22.13 (1 of 2)

Sequence of events

Changes in anterior-posterior and superior-

inferior dimensions

Changes in lateraldimensions

(superior view)

Ribs are elevatedand sternum flares

as externalintercostals

contract.

Diaphragmmoves inferiorly

during contraction.

Externalintercostalscontract.

Inspiratory muscles contract (diaphragm descends; rib cage rises).

2

1

Thoracic cavity volume increases.

3 Lungs are stretched; intrapulmonary volume increases.

4 Intrapulmonary pressure drops below Patm (–1 mm Hg).

5 Air (gases) flows into lungs down its pressure gradient until intrapulmonary pressure is 0 (equal to atmospheric pressure).

Inspiration: An Active Process

Figure 22.13 (2 of 2)

Sequenceof events

Changes in anterior-posterior and superior-

inferior dimensions

Changes inlateral dimensions

(superior view)

Ribs and sternumare depressed

as externalintercostals

relax.

Externalintercostalsrelax.

Diaphragmmovessuperiorlyas it relaxes.

1 Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages).

2 Thoracic cavity volume decreases.

3 Elastic lungs recoil passively; intrapulmonary volume decreases.

4 Intrapulmonary pressurerises above Patm (+1 mm Hg).

5 Air (gases) flows out of lungs down its pressure gradient until intra-pulmonary pressure is 0.

Expiration: Normally a Passive Process

Forced expiration is an active process: it uses abdominal and internal intercostal muscles

Pressure anim. I online

Pressure anim II online

http://msjensen.cehd.umn.edu/1135/Links/Animations/Flash/0034-swf_alveolar_press.swf

http://bcs.whfreeman.com/thelifewire/content/chp48/4802s.swf

Atelectasis

Atelectasis (lung collapse)

• Plugged bronchioles collapse of alveoli

• Wound that admits air into pleural cavity (pneumothorax)




Respiratory Mucosa





• Lung Compliance

Physical Factors Influencing Pulmonary Ventilation Three factors that must be overcome by inspiratory

muscles

2. Alveolar surface tension (alleviated by Type II alveolar cell surfactant)

3. Lung compliance: the change in lung volume that occurs with a given change in transpulmonary pressure (lung “stretchiness”)

1. Airway resistance (friction, usually insignificant if bronchioles wide open, increasing with smaller diameters)

Lung Compliance: Ease of Lung Expansion

Compliance is normally high (easily inflated) due to

• Lung tissue is readily distensible (stretched outwards)

• Surfactant alleviates alveolar surface tension

Compliance is reduced (as in “stiff lungs”) by

• Nonelastic scar tissue (fibrosis)

• Reduced production of surfactant (e.g. death of Type II cells)

• Decreased flexibility of the thoracic cage

Homeostatic imbalances that reduce compliance

• Paralysis of intercostal muscles

Emphysema

Features of Emphysema

Chronic inflammation promotes lung fibrosis (tends to decrease lung compliance)

Airways collapse during expiration

Type II surfactant cells die, reducing surfactant production and decreasing compliance

Alveoli enlarge as adjacent chambers break through, increasing lung compliance somewhat (easier to inflate)

Patients use a large amount of energy to exhale, normally a passive process

Overinflation of the lungs leads to a permanently expanded barrel chest

Cyanosis appears late in the disease




Respiratory Mucosa





• Lung Compliance

The Respiratory System I: Anatomy Functions of the Respiratory System The Nasal Cavity and Sinuses...

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