Chapter 22: The Respiratory System

Pulmonary ventilation

Movement of air in and out of the lungs

External respiration

Gas exchange between lungs and blood

Transport of gases

Cardiovascular system uses blood to transport gases

Internal respiration

Gas exchange between blood and tissues

Respiratory zone

Site of gas exchange

Conducting zone

Includes respiratory passageways; cleanses, humidifies and warms incoming air

Nose

Provides an airway for respiration; moistens, warms, and filters air

Trachea

Stretches during respiration and recoils during expiration

Bronchi

Direct air into the lungs

Bronchioles

Airways in the lungs that lead the bronchi to alveoli

Alveoli

Tiny sacs of lung tissue specialized for gas exchange between air and blood

Mucociliary escalator

Cilia that transport mucus and foreign material out of the respiratory tract

Respiratory membrane

Where gas exchange occurs between air on the alveolar side and blood on the capillary side; formed by alveolar and capillary walls

Type I alveolar cells

Simple squamous cells where gas exchange occurs

Type II alveolar cells

Secrete surfactant

Surfactant

Chemical that maintains surface tension of alveoli and keeps them from collapsing

Pleura

A thin, double layered membrane covering each lung

Pleural fluid

Allows lungs to glide over thorax wall during breathing movements

Pulmonary circulation

Blood flow from the heart to the lungs

Parietal pleura

Covers the thoracic wall and superior face of the diaphragm

Visceral pleura

Covers the external lung surface

Pleural cavity

Contains the lungs

Pleurisy

Inflammation of the pleura; sharp pain when breathing

Atmospheric pressure

Pressure exerted by air surrounding the body (760 mmHg)

Intrapulmonary pressure (Ppul)

Pressure in the alveoli; rises and falls with breathing phases

Intrapleural pressure (Pip)

Pressure in the pleural cavity; always 4 mm Hg less than Ppul

Pneumothorax

Air in the pleural cavity caused by a puncture of the lung or chest wall; collapsed lung

Expiration

Exhalation

Inspiration

Inhalation

Infant respiratory distress syndrome

Caused by immature lungs; too little surfactant in alveoli; lungs collapse with each breath

Spirometer

Instrument used to measure breathing

Tidal volume (TV)

Amount of air inhaled or exhaled with each breath under resting conditions (~500 mL)

Inspiratory reserve volume (IRV)

Amount of air that can be inspired forcibly beyond tidal volume (2100-3200 mL)

Expiratory reserve volume (ERV)

Amount of air that can be expelled from the lungs after a normal tidal volume expiration (~1000-1200 mL)

Residual volume (RV)

Amount of air that remains in the lungs after tidal volume expiration, helps keep alveoli open and prevent lung collapse (~1200 mL)

Total lung capacity (TLC)

TV + IRV + ERV + RV

Inspiratory capacity (IC)

TV + IRV

Expiratory capacity (EC)

TV + ERV

Vital capacity (VC)

TV + IRV + ERV

Hemoglobin

Composed of four polypeptide chains, each bound to an iron-containing heme group which binds four oxygen molecules

Oxyhemoglobin

Hemoglobin with oxygen

Partially saturated

Hemoglobin with 1-3 oxygen molecules

Fully saturated

Hemoglobin with 4 oxygen molecules

Affinity

Ability of oxygen to bind to hemoglobin

Oxygen-hemoglobin dissociation curve

Describes percentage of hemoglobin saturated with oxygen at any given PO2

Pneumonia

Inflammation of lung tissue where alveoli fill with fluid

Emphysema

Air sacs of lungs are damaged and enlarged, causing breathlessness.

Bohr effect

Declining blood pH and increasing Pco2 weakens the Hb-O2 bond

Carbon monoxide

Colorless, odorless gas that outcompetes oxygen for hemoglobin binding

Right shift

An increase in temperature, Pco2, or H+ that lowers Hb’s affinity for oxygen; increases oxygen unloading

Left shift

A decrease in temperature, Pco2, or H+ that increases Hb’s affinity for oxygen; decreases oxygen unloading

Medullary respiratory centers

Ventral respiratory group and dorsal respiratory group

Ventral respiratory group

Rhythm-generating and integrative center that contains groups of neurons that fire during inspiration and expiration

Dorsal respiratory group

Integrates input from peripheral stretch and chemoreceptors; relays this information to VRG

Pontine respiratory centers

Influence and modify activity of medullary neurons and transmit impulses to VRG

Eupnea

Normal breathing

Central chemoreceptors

Receptors in CNS that monitor pH of CSF to regulate ventilation rate

Peripheral chemoreceptors

Receptors in carotid arteries and aorta that monitor blood pH to regulate ventilation rate

Aortic bodies

Receptors located in the aortic arch capable of detecting changes in arterial PO2

Carotid bodies

Chemoreceptors located in internal carotid artery; respond to changes in arterial PO2, PCO2, and pH

Hypercapnia

Excessive CO2 in blood

Hypocapnia/hyperventilation

CO2 levels fall and pH rises

Apnea

Absence of breathing