Respiratory System

Chapter 22Biology 2122

Respiratory System Functions

1. Pulmonary Ventilation 2. External Respiration 3. Respiratory Gas 4. Internal Respiration

Functional Zones

1. Respiratory

2. Conducting

Animation

Nose and Para-nasal Sinuses Functions:

Airway Warmth and moisture Filter and cleaning Resonation – speech Site of olfactory organs

External nose Internal nose

○ Lined with olfactory mucosa ○ Mucus contains lysozyme (antibacterial)○ Epithelial cells secrete defensins (natural antibiotic)

Nasal Cavity

Conchae

Paranasal sinuses Pharaynx

NasopharynxOropharynxLaryngopharynx

Larynx

From the 4th to the 6th vertebrae attached to hyoid bone (superiorly)

Functions: Opens airway

Route air and food into correct passageways Voice production

Structure9 cartilage (hyaline) rings

Thyroid cartilage fuses (two plates) and forms the laryngeal prominence (adam’s apple)

Arytenoid (anchors vocal cords), cuneiform and corniculate cartilages

Larynx

• Ninth cartilage - epiglottis (elastic cartilage)

• Vocal folds (true vocal cords) contain no BVs so appear white; vibrate and produce sound– vestibular folds (false vocal cords)– glottis

• Superior part of the larynx – stratified squamous: protection from food

Trachea

4 inches (10-12 cm) long and 1 inch (2.5 cm) in diameter

Contains: (1). Mucosa (goblet cells and P.S. epithelium) (2). Submucosa (CT) (3). Adventitia (CT reinforced by 16-20 Cartilage rings –hyaline cartilage)

Final cartilage is larger - Carina

Bronchi and Bronchial Tree

Trachea branches at the T-7 level

Right bronchi is wider, shorter and more vertical

Bronchi branch into secondary and tertiary bronchi

When the size becomes less than 1 mm in diameter - bronchiole

Terminal bronchioles - less than 0.5 mm in diameter

Respiratory Zone Structures

1.Terminal bronchioles ----- respiratory bronchioles ---- alveoli

2.Alveolar ducts lead into the alveolar sacs (terminal); gas exchange

3.300 million alveoli

Respiratory Membrane

Alveoli wall contain – Type-I cells (simple squamous) – Type-II-secrete fluid

The alveolar and capillary walls form the respiratory membrane (air-blood barrier)

Other features of the alveoli: – Pores between alveoli allow for

equalized air pressure

– Contain macrophages

Lungs Suspended in pleural cavity connected to mediastinum by vascular and bronchial attachments called roots. Costal surface of lungs lie in contact with ribs

Hilus

Left lung is smaller - the cardiac notch accommodates the heart

Fissures

Lung ‘odds and ends’

Each lobe of lung contains pyramid-shaped bronchopulmonary segments separated by CT septa

– Each is served by own artery and vein

Lobules are smallest segments of lungs – Each is served by a large bronchiole and branches

Lungs also contain elastic CT – spongy and elastic

Lung Circulation

Pulmonary and bronchial circulation

Pulmonary arteries •bring in blood to be oxygenated •feed into the pulmonary capillary networks surrounded by the alveoli

Fresh oxygenated blood - returned to the heart via the pulmonary veins

Innervation - Lungs

Parasympathetic, Sympathetic motor fibers and visceral sensory fibers enter the lungs via the pulmonary plexus on the lung root

Parasympathetic fibers constrict air tubes

Sympathetic fibers dilate air tubes

Mechanics of Breathing

VentilationInspiration (air into the

lungs)Expiration (out of the lungs)

Respiratory pressures - atm pressure

Atmospheric Pressure (Patm)760 mmHg sea level=1 atm Pressure exerted by gases

surrounding the body Any pressure less than 760

mmHg is less than atmospheric pressure

Thoracic Cavity Pressure Intrapulmonary Pressure (Ppul)

(a). Pressure in the alveoli(b). May rise or fall (short periods) but always equalizes out to equal Patm

Intrapleural Pressure (Pip)(a). Pressure in the pleural cavity fluctuates with breathing (b). 4 mmHg Less than Ppul and Patm (negative pressure)

How is the Intrapleural pressure established?

Forces that pull lungs away from wall (cause collapse)

Force 1: Lungs Recoil

Force 2: Surface Tension of Alevolar Fluid

What opposes these forces?

Thoracic Cavity Pressure

1. Which force will win? Neither! Due to the adhesive force between the parietal and visceral pleura

2. What is the significance?Pressure differences inside and out side the lungs allow

for breathing to take placeAir will move down the pressure concentration gradientPressure is greater outside so air will move into the lungs

3. Consequences of a collapsed lung!

The Breathing Process- Ventilation 1. Inspiration

Enlargement of the thorax increases volume Boyle’s LawGreater the volume - number of gas particles per

unit volume decrease Pressure is greater outside of the lungs!

2. ExpirationVolume of thorax decreases pressure increases1 mm Hg higher than outer pressureBreathe out

Changes in Thoracic Volume

Pressure Changes and Resistance

Factors that Influence Pulmonary Ventilation

(1). Airway Resistance (non elastic source of resistance)

Drag decreases gas flowUpper respiratory tract is larger; midsize bronchi offer most

resistance; terminal bronchioles air flow basically stops

(2). Aveolar Surface TensionLiquids drawn together create surface tensionWater: strong surface tensionIf left alone, water create ST on the alveoli and would collapse

the alveoli Production of surfactant Less force needed to overcome forces needed to expand lungs

Factors that Influence Pulmonary Ventilation3. Lungs stretch due to elastic fibers- Lung Compliance

– (a). Expansion of lungs increases compliance– (b). Determined by

• Distensibility of lung tissue• Alveolar surface tension (must be kept low)

4. Diminished by – (a). Fibrosis, scar tissue– (b). Blockages– (c). Reduced production of surfactants

– (d). Reduced flexibility of rib cage

Respiratory Volumes

Links for Ventilation

• Ventilation