Chapter 22: The Respiratory System

respiratory system

the system that helps to produce sound, with intonation, with eating, and with breathing but its major function is to maintain cellular respiration (O2 delivery and CO2 disposal)

pulmonary ventilation

the movement of air into and out of the lungs (breathing)

external respiration

the exchange of oxygen and carbon dioxide between the lungs and blood

circulatory system

the system that moves blood and nutrients throughout the body

transport

the movement of oxygen and carbon dioxide in the blood from the lungs to the tissues (O2) or from the tissues to the lungs (CO2)

internal respiration

the movement of oxygen into the tissues and carbon dioxide into the blood

upper respiratory system

made up of the nose and nasal cavity, the paranasal sinuses, and the pharynx

lower respiratory system

made up of the larynx, trachea, the bronchi and bronchiole branches, and the lungs and alveoli

nose

divided into 2 regions: the external nose and the nasal cavity; provides airway for respiration, humidifies entering air, filters inspired air, serves as a resonance chamber for speech, and houses the olfactory receptors

paranasal sinuses

provides an airway for respiration, moistens and warms entering air, filters and cleans inspired air, serves as a resonance chamber for speech, and houses the olfactory receptors

nasal vestibule

divided in two by the septum, consists of the vibrissae, nasal meati, olfactory mucosa, and respiratory mucosa

septum

divides the nasal vestibule into 2

vibrissae

hairs in the nose/nasal cavity that are covered in mucus to filter and trap pathogens and bacteria

nasal meatuses

ridges that increase the surface area for more mucus coverage; produce lysosomes and defensins for fighting off bacteria

olfactory mucosa

olfactory receptors for smell

respiratory mucosa

has cilia, goblet cells, and seromucus nasal glands

goblet cells

produce mucus in the respiratory mucosa

seromucus nasal glands

glandular or clustered goblet cells

nasal conchae

the groove between the 3 nasal meati which increases the surface area and mucus production; during inhalation: filters, warms, and moistens the air; during exhalation: reclaims heat and moisture

paranasal sinuses

surround the nasal cavity and create hollow spaces within the skull to lighten it; secrete mucus and warm/moisten air

pharynx

funnel-shaped muscular tube that connects the nasal cavity and the mouth to the larynx and the esophagus; has three regions: nasopharynx, oropharynx, and laryngopharynx

nasopharynx

the superior region of the pharynx that is an air passage in normal conditions; is closed during swallowing; pharyngeal tonsils and the pharyngotympanic tubes are here as well

pharyngeal tonsils

adenoids; trap bacteria in “tonsilar crypts”

pharyngotympanic tubes

drain fluid from the ear to the esophagus

oropharynx

middle region of the pharynx that acts as a passage for food and air; includes the isthmus of fauces and the palatine and linguil tonsils

laryngopharynx

inferior region of the pharynx that acts as a passage for food and air and connects the larynx to the esophagus

larynx

a patent (open) airway that routes air to the trachea and food to the esophagus; also plays part in voice production

epiglottis

cartilage flap that covers the laryngeal inlet during swallowing to prevent food from entering the trachea (which leads to choking)

vocal folds

cartilage folds that vibrate to produce sound/noises as air rushes up from the lungs

speech production

the intermittent release of expired air

pitch

is determined by the length and tension of the vocal cords

volume

amount of air

laryngitis

inflammation of the vocal folds that interferes with vibration, changes the vocal tone (“hoarseness”) and is most often caused by viral infections, overuse of the voice, very dry air, bacterial infections, or inhalation of irritants

trachea

“straw” with cartilage ridges that can dilate and constrict due to some smooth muscle composition; comprised of mucosa, submucosa, the adventitia, the trachealis, and the carina

mucosa

seudostratified and ciliated epithelial layer that moves things up the trachea to the epiglottis

submucosa

layer that helps produce mucus in the trachea

trachealis

smooth muscle fibers in the trachea that help to expel mucus when coughing

carina

cartilage branchings in the trachea with submucosa and adventitia that are highly sensitive to anything other than air

Heimlich maneuver

used to decrease the volume of the thoracic cavity to increase the pressure in the cavity to expel a tracheal obstruction

bronchi

“conducting zone” where the trachea splits into the brachial tree and conducts air; get smaller and smaller but smooth muscle composition increases for more resistance; NO GAS EXCHANGE

tertiary bronchi

branch into bronchioles and terminal bronchioles; NO GAS EXCHANGE

terminal bronchioles

“respiratory zone” feed into respiratory bronchioles with alveoli and capillaries for gas exchange

alveoli

grape-like cell clusters where gas exchange occurs

alveolar ducts

feed into individual alveoli sacs that are surrounded by capillaries for gas exchange

respiratory membrane

“blood-air barrier”; extremely thin alveolar wall for rapid and efficient gas exchange through simple diffusion

type 1 cells

alveolar cells; 1 layer of simple squamous epithelium

type 2 cells

surfactant cells; secrete surfactant

surfactant

detergent-like complex produced by type II alveolar cells that helps to coat the alveoli and prevent them from sticking together, maintaining their shape/preventing alveolar collapse

alveolar pores

holes in alveolar walls that connect adjacent alveoli and help equalize pressure in the lungs

alveolar macrophages

resident (fixed) or migratory (wandering)

pulmonary arteries

deliver deoxygenated blood from the right ventricle

pulmonary veins

return oxygenated blood to the left atria; low pressure and high volume; have ACEs

ACEs

enzymes in the pulmonary veins that act on different things in the blood

pleura

double-layered serous membranes that line the lungs

parietal pleura

the layer of the pleura that is open to the cavity

visceral pleura

the layer of the pleura that is continuous with the lungs

pleural fluid

in between the parietal and visceral pleura to prevent friction

pleurisy

inflammation of the pleura (often from pneumonia) that leads to roughness and friction, which causes pain; may produce excess fluid, leading to excess pressure and trouble breathing

pleural effusion

the accumulation of fluid in the pleural cavity

atmospheric pressure

Patm; the pressure exerted by the atmosphere on the body; 760 mmHg at sea level = 1 atm

altitude

elevation; pressure decreases as this increases to varying degrees

depth

depression; for every 33 ft below sea level, pressure increases by 1 atm or 760 mmHg

intrapulmonary pressure

Ppul; the pressure within the alveoli that changes with breathing (briefly levels with atmospheric pressure)

intrapleural pressure

Pip; the pressure in the pleural cavity that fluctuates with breathing but is always negative

transpulmonary pressure

prevent collapse and keep the lungs ever-open; Ppul - Pip

pneumothorax

a collapsed or punctured lung from external means (punctured parietal pleura)

respiratory pressure

negative respiratory pressure means that it is less than atmospheric; positive respiratory pressure means that it is greater than atmospheric; the lungs will probably collapse if Pip = Ppul or if Pip = Patm

inspiration

an active process that follows the inspiratory muscles to facilitate air flow into the lungs; “breathing in”

inspiratory muscles

the diaphragm and external intercostal muscles which contract to allow the lungs to stretch, causing an overall drop in intrapulmonary pressure that allows air to flow in

expiration

a mechanical process that occurs when the pressure in the lungs is greater than the atmosphere’s; “breathing out”

Boyle’s Law

the relationship between pressure and volume of gases: pressure varies inversely with volume: P1V1 = P2V2

quiet expiration

normal, passive exhalation

forced expiration

when the obliques, transverse abdominal, and intercostal muscles are voluntarily contracted to exhale

non-respiratory air movements

processes that move air in or out of the lungs and may modify the normal respiratory rhythm; reflexes for the most part but some voluntary (coughing, sneezing, crying, yawns, laughing, and hiccups)

airway resistance

F = ΔP/R ; where ΔP is the pressure gradient between the atmosphere and alveoli (usually 2 mmHg or less)

epinephrine

dilates the bronchioles to reduce airway resistance

alveolar surface tension

the concept that alveoli generally resist sticking to each other thanks to surfactant

lung compliance

CL; the measure of changes in volume of the lungs with relation to transpulmonary pressure; measure of “stretch” of the lungs

tidal volume

TV; about 500 mL; the amount of air moved in and out of the lungs with each breath

inspiratory reserve volume

IRV; about 2100-3200 mL; the amount of air that can be inspired forcefully beyond tidal volume

expiratory reserve volume

ERV; about 1000-1200 mL; the amount of air that can be forcibly expelled from the lungs

residual volume

RV; the amount of air that always remains in the lungs, which is necessary to keep the alveoli open and prevent the lungs from collapsing

respiratory capacity

combinations of 2 or more respiratory volumes

inspiratory capacity

IC; the sum of TV + IRV which equals the total amount of air that can be inspired after normal tidal expiration

functional residual capacity

FRC; the sum of RV + ERV which equals the amount of air remaining in the lungs after normal tidal expiration

vital capacity

VC; the sum of TV + IRV + ERV which equals the total amount of exchangeable air

total lung capacity

TLC; TV + IRV + ERV + RV which is the sum of all lung volumes

external respiration

the diffusion of gases between the blood and the lungs which is influenced by partial pressure gradients and gas solubility, the thickness and surface area of the respiratory membrane, and by ventilation-perfusion coupling

internal respiration

the diffusion of gasses between the blood and body tissues

Dalton’s Law of partial pressures

the total pressure exerted by a mixture of gases is equal to the sum of its partial pressures

partial pressure

Pp; the pressure exerted by each gas in a mixture which is directly proportional to its percentage in the mixture

gas concentrations

measured in ppm (parts per million) or percent concentration

Henry’s Law

states that each gas will dissolve in a liquid in proportion to its partial pressure

alveolar gas composition

has more CO2 and water vapor than atmospheric air (mix with each breath); gas exchange occurs in lungs; humidification of air occurs by conducting passages

ventilation-perfusion coupling

process that matches alveolar ventilation to pulmonary blood perfusion

O2 pressure gradient

steep (in blood and lungs); venous blood Po2 = 40 mmHg and alveolar Po2 = 104 mmHg; this difference drives O2 flow into the blood, and pressures equal equilibrium in 0.25 seconds, which ensures adequate oxygenation even if blood flow increased 3x

CO2 pressure gradient

is less steep than O2; venous blood Pco2 = 45 mmHg and alveolar Pco2 = 40 mmHg; despite the gradient difference, CO2 still diffuses in equal amounts with O2 because CO2 is 20x more soluble

emphysema

when the walls of adjacent alveoli break down, enlarging the alveolar chambers, causing a drastic reduction in alveolar surface area; the 0.75 seconds for RBC diffusion through capillaries may not be enough for adequate gas exchange so the body tissues may suffer from oxygen deprivation

perfusion

the amount of blood flow reaching the alveoli; Po2 controls this by changing arteriolar diameter where necessary (high Po2 causes the arterioles to dilate which increases blood flow and low Po2 causes the arterioles to constrict which decreases blood flow)

ventilation

the amount of gas reaching the alveoli; Pco2 controls this by changing bronchiolar diameter where necessary (high Pco2 causes the bronchioles to dilate and the lungs to expel CO2 more rapidly and low Pco2 causes the bronchioles to constrict and the lungs hold on to CO2)