[PH131 LEC] 04_Respiratory System

Processes of respiration

Ventilation/breathing, gas exchange, gas transportation, regulation

Inflow or outflow of air between the atmosphere and and the lungs

Ventilation/breathing

Exchange/diffusion of oxygen and carbon dioxide between the lungs and the blood (external respiration)

Gas exchange

Transport of oxygen and carbon dioxide between the lungs and the blood and body fluids to and from the tissue cells

Gas transportation

Gas exchange between the blood and the tissues (internal respiration); regulation of ventilation and other facets

Regulation

Functions of respiratory system

Regulation of blood pH, voice production, olfaction, innate immunity

Alter blood pH by changing blood CO2 levels

Regulation of blood pH

Air movement past vocal chords makes sound and speech possible

Voice production

The sensation of smell occurs when airborne molecules are drawn into the nasal cavity

Olfaction

Protects against some microorganisms and other pathogens, such as viruses, by preventing them to enter the body and by removing them from respiratory surfaces

Innate immunity

Upper respiratory tract

External nose, nasal cavity, pharynx and associated structures, larynx

Lower respiratory tract

Trachea, bronchi, lungs

Conducting zone

External zone, nasal cavity, pharynx, trachea, bronchi

Respiratory zone

Respiratory bronchioles, alveolar ducts, alveoli

Composed of hyaline cartilage (with collagen for elasticity), bone, skin

External nose

Present on the lateral walls on each side of the nasal cavity, made of pseudostratified ciliated columnar respiratory epithelium, causes the air to churn inside the nasal cavity

Conchae

Functions of the nasal cavity

Passageway for air, cleans the air, humidifies the air, contains olfactory epithelium

Stratified squamous epithelium with coarse hairs

Lining of the nasal cavity

Pseudostratified ciliated columnar epithelium with cilia and goblet cells

Rest of the nasal cavity

Common opening of both the digestive and respiratory systems

Pharynx

Connected to the nasal cavity, composed of pseudostratified ciliated columnar epithelium, the soft palate is elevated during swallowing to close the nasopharynx and prevent food from passing into the nasopharynx, contains the pharyngeal tonsil, which defends body against infections, also called the adenoid

Nasopharynx

The oral cavity opens into the oropharynx, food, drink, and air all pass through the oropharynx, the palatine and lingual tonsils are located near the opening between the mouth and oropharynx, lined with stratified squamous epithelium, which protects against abrasion

Oropharynx

Passes posterior to the larynx and extends from the tip of the epiglottis to the esophagus, food and drink and small amount of air pass through the laryngopharynx to the esophagus, lined with stratified squamous epithelium and ciliated columnar epithelium

Laryngopharynx

Outercasing of 9 cartilages (3 unpaired and 3 pairs)

Larynx

Unpaired cartilages

Thyroid cartilage or Adam’s apple, cricoid cartilage, epiglottis

Largest cartilage in the larynx

Thyroid cartilage or Adam’s apple

Most inferior

Cricoid cartilage

Made up of 16-20 C-shaped hyaline cartilage, 1.4-1.6 cm in diameter, 10-11 cm long, pseudostratified columnar epithelium with cilia and goblet cells

Trachea

Two large tubes that connect to the trachea and direct the inhaled air to the lungs

Bronchi

More horizontal

Left main bronchus

Wider, shorter, and more vertical, Foreign bodies tend to get lodged into due to its shape

Right bronchus

Cone-shaped, spongey, pinkish-gray in color

Lungs

Three lobes of the right lung

Superior, middle, inferior

Two lobes of the left lung (which is smaller in size)

Superior, inferior

Lung anatomy

Secondary bronchi, tertiary bronchi, terminal bronchioles, respiratory bronchioles, alveolar ducts

Layers of the respiratory membrane

Alveolar fluid (with surfactant), alveolar epithelium, basement membrane of alveolar epithelium, interstitial space, basement membrane of the capillary epithelium, pulmonary capillary endothelium

Also known as breathing, is the process of moving air into and out of the lungs

Ventilation

Movement of air into the lungs

Inspiration

Movement of air out of the lungs

Expiration

Muscles of inspiration

Diaphragm (a large dome of skeletal muscle that separates the thoracic cavity from the abdominal cavity). external intercostal muscles (muscles that elevate the ribs and sternum)

Muscles of expiration

Internal intercostals, depress the ribs and sternum

Contraction of the diaphragm causes the top of the dome to move inferiorly, which increases the volume of the thoracic cavity

Quiet inspiration

Elevates the ribs and sternum, which increases thoracic volume by increasing the diameter of the thoracic cage

Contraction of the external intercostals

Occurs when the diaphragm and external intercostals relax

Expiration during quiet breathing

Perform “work” to cause inspiration but not to cause expiration

Respiratory muscles

Two physical principles govern the flow of air into and

out of the lungs

Changes in volume result in changes in pressure and air flows from an area of higher pressure to an area of lower pressure

Relationship between volume of the thorax and pressure within the thoracic cavity

Inverse

Relationship between pressure difference and rate of airflow

Direct

The process of measuring volumes of air that move into and out of the respiratory system

Spirometry

Device that measures these respiratory volumes

Spirometer

Measure of the amount of air movement during different portions of ventilation

Respiratory volumes

Types of respiratory volumes

Tidal volume, inspiratory reserve volume, expiratory reserve volume, residual volume

The volume of air inspired or expired with each breath, at rest, quiet breathing results in a tidal volume of about 500 milliliters (mL)

Tidal volume

The amount of air that can be inspired forcefully beyond the resting tidal volume, averages about 3000 mL

Inspiratory reserve volume

The amount of air that can be expired forcefully beyond the resting tidal volume, averages about 1100 mL

Expiratory reserve volume

The volume of air still remaining in the and lungs after the most forceful expiration, averages about 1200 mL

Residual volume

Sums of two or more respiratory volumes

Respiratory capacities

This is the amount of air a person can inspire maximally after a normal expiration (about 3500 mL at rest), (TV + IRV = 500 mL + 3000 mL)

Inspiratory capacity

This is the amount of air remaining in the lungs at the end of a normal expiration (about 2300 mL at rest), (ERV + RV = 1100 mL + 1200 mL)

Functional residual capacity

It is the maximum volume of air that a person can expel from the respiratory tract after a maximum inspiration and expiration (about 4600 mL), (IRV + TV + ERV)

Vital capacity

It is the sum of the inspiratory and expiratory reserves and the tidal and residual volumes (about 5800 mL), (IRV + ERV + TV + RV), (VC + RV), women < men = 20%-25%, large, athletic > small, asthenic

Total lung capacity

Air that can be forcibly exhaled from your lungs after taking the deepest breath possible, used to evaluate lung function, cannot identify which specific lung disease

Forced vital capacity

Contraction of the smooth muscle in the bronchioles = ↑ resistance

Asthma

Changes in the lung tissue; destruction of the alveolar walls; collapse of the bronchioles; decreased elasticity of the lung tissue = ↑ resistance

Emphysema

Inflamed air passages; ↑ mucus secretion; loss of cilia; narrowed bronchioles = ↑ resistance

Chronic bronchitis

Occurs in the respiratory membrane of the lungs

Gas exchange between air and blood

Supplies atmospheric air to alveoli

Ventilation

Major area of gas exchange (some takes place in respiratory bronchioles and alveolar ducts)

Alveoli

Gas exchange do not occur in other areas of respiratory passageways

Bronchioles, bronchi, and trachea

Volume in bronchioles, bronchi, and trachea

Anatomical dead space

Factors of gas exchange

Respiratory membrane thickness, surface area, partial pressure

Use O2 and produce CO2 thus, blood returning from tissues and entering the lungs has decreased PO2 and increased PCO2 compared to alveolar air

Cells

Diffuses from alveoli into the pulmonary capillaries

O2

Diffuses from capillaries into alveoli

CO2

Flows from lungs through the left side of the heart to the tissue capillaries

Blood

Diffuses from capillary into the interstitial fluid

O2

Diffuses from interstitial fluid into cells

O2

Hemoglobin with O2 bound to its heme groups

Oxyhemoglobin

Hemoglobin binds to O2

High PO2

Hemoglobin releases O2

Low PO2

Factors influencing the amount of O2 released from hemoglobin

PO2 levels - low PO2 → more O2 released

PCO2 levels - high PCO2 → more O2 released

pH - low pH → more O2 released

Temperature - high temperature → more O2 released

Increased muscular activity results in

Decreased PO2

Increased PCO2

Reduced pH

Increased temperature

Diffuses from cells (its production site) into the tissue capillaries

Carbon dioxide

After CO2 enters the blood, it is transported in three ways

7% Transported as dissolved CO2 in plasma

23% Transported in combination with blood proteins (primarily hemoglobin)

70% Transported in the form of bicarbonate ions (HCO3-)

Enzyme located inside red blood cells and on the surface of capillary epithelial cells, increases the rate at which CO2 reacts with water to form H+ and HCO3- in the tissue capillaries, promotes the uptake of CO2 by red blood cells

Carbonic anhydrase

In lung capillaries

HCO3- and H+ combine to produce H2CO3 which then forms CO2 and H2O

CO2 diffuses into the alveoli and is expired

Increase in CO2 levels

Blood pH decreases

General manifestations

Sneezing, wheezing, coughing, stridor, sputum/mucoid discharge, breathing patterns and characteristics, Kussmaul respirations, labored respirations/prolonged inspirations or expirations due to obstruction of airways

Clear, thin, colorless/cream colored

Normal secretion

Yellowish-green, cloudy, thick

Bacterial infection

Rusty/dark colored (indication of bleeding)

Pneumococcal pneumonia

Purulent (contains pus), foul odor

Bronchiectasis

Normal rate and pattern

10-18 inspirations/min; effortless

Viral infection which may affect upper and lower respiratory tracts, different from common cold, may cause viral pneumonia (affecting lower respiratory), may cause secondary problems like bacterial pneumonia

Influenza

Primary sites of influenza viral replication

Trachea, bronchi, pulmonary alveoli

Desquamation of pseudostratified columnar epithelium happens → cilia and goblet cells affected

Acute stage of influenza viral replication

Major source of pro-inflammatory cytokines

Endothelial cells

Chronic restrictive diseases resulting from long-term exposure to irritating particles

Pneumoconiosis

Coal dust

Coal-worker's disease or anthracosis

Silica

Silicosis