respiratory system

functions of respiratory system

- gas exchange (O2, CO2)
- protect respiratory surfaces from dehydration, temp changes, pathogens
- produce sounds
- detect odors

respiratory system

oxygen diffuses along surface of lungs → blood carries oxygen (O2 from lungs to peripheral tissues OR CO2 from peripheral tissues to lungs)

organization of respiratory system

divided into upper respiratory system and lower respiratory system

lower respiratory system

starts at larynx → trachea → bronchi → bronchioles → alveoli

respiratory tract

divided into conducting portion and respiratory portion

conducting portion

no exchange of gases, from nasal cavity to larger bronchioles

respiratory portion

exchange of gases, smallest respiratory bronchioles and alveoli

respiratory mucosa

lines conducting portion of respiratory system; consists of epithelium and connective tissue

\
forms part of respiratory defense system → removes particles and pathogens from inhaled air

connective tissue

exist as mucous glands in upper respiratory system, trachea, bronchi

\
exist as smooth muscle cells around bronchioles in conducting portion of lower respiratory system

mucous glands

trap particles from air breathed in → cilia, hair like structures, in trachea brush up the mucous up → either coughed out or swallowed down esophagus

smooth muscle around bronchioles

when contracted = decreased air to lungs

\
when relaxed = increased air to lungs

alveolar epithelium

lines exchange surfaces of alveoli

\
made of very delicate, simple squamous epithelium (1 layer thick for easier gas exchange + fried egg shape)

respiratory defense system

composed of

- filtration in nasal cavity (removes large particles)
- mucous cells and mucous glands
- cilia
- alveolar macrophages (phagocytose pathogens)

nose

air enters through nostrils or nares → passes into nasal vestibule

\
presence of nasal hairs to trap large particles in air

nasal cavity

consists of nasal septum, olfactory region, mucus

olfactory region

towards top of nasal cavity, provides sense of smell

mucus

cleans and moistens nasal cavity

meatuses

narrow passageways between nasal conchae that produce air turbulence to

- trap particles in mucus
- warm/humidify incoming air
- bring olfactory stimuli to olfactory receptors

nasal conchae

bony ridges that project into the nasal cavity

nasal mucosa

warms/humidifies inhaled air, breathing through the mouth bypasses this important step

pharynx

a chamber shared by digestive and respiratory systems, either the digestive tract or respiratory tract

glottis

slit-like opening between vocal cords

thyroid cartilage

a firm prominence of cartilage that forms the upper part of the larynx; the Adam's apple

epiglottis

covers the glottis when swallowing; prevents foods and liquids from entering respiratory tract while swallowing

sound production

air passing through the glottis vibrates vocal cords → produces sound waves

phonation

sound production at larynx

articulation

sound modification with lips, tongue, teeth

trachea

(windpipe), tough flexible tube that extends from cricoid cartilage to mediastinum → branches into right/left main bronchi

\
contains 15-20 C-shaped tracheal cartilages

tracheal cartilage

stiffen tracheal walls and protect airway by keeping it open

bronchial tree

right main bronchus and left main bronchus

terminal bronchiole

second to last bronchiole, end of conducting portion

\
smooth muscle surrounding it allows bronchodilation and bronchoconstriction

capillaries and alveoli

capillaries bring deoxygenated blood to alveoli and reload on O2 before leaving

\
air from alveolar sac → should never have fluid

bronchioles

have no cartilage, dominated by smooth muscle

autonomic nervous system

controls luminal diameter of bronchioles by regulating smooth muscle → controls airflow in lungs

bronchodilation

caused by sympathetic activation → enlarges luminal diameter of airway + reduces resistance to air flow

\
more O2, produce more ATP, offload more CO2

bronchoconstriction

caused by parasympathetic activation or histamine release to allergic reaction → reduces luminal diameter of airway

respiratory bronchioles

branches of the terminal bronchioles that subdivide into several alveoli

alveolar cell layer

consists mainly of simple squamous epithelium formed by pneumocystis type I

\
site of gas exchange and patrolled by alveolar macrophages

surfactant

oily secretion that coats alveolar surface and reduces surface tension so that the lungs can easily expand/contract

\
produced by large, scatter pneumocytes type II

blood air barrier

alveolar cell layer, capillary endothelial layer, fused basement membrane between them

\
if thickness is increased, ability to exchange gases is compromised

gas exchange

across the blood air barrier, quick and efficient

\
distance for diffusion is short + O2/CO2 are small and lipid soluble

left and right lungs

in left and right pleural cavities

\
inferior portion rests on diaphragm

lobes

subdivisions of the lung separated by deep fissures, with 2 on the left and 3 on the right

pulmonary embolism

a blocked branch of pulmonary artery that stops blood flow to alveoli

pulmonary circuit BP

lower than systemic circuit since it's smaller in size and less force is needed to push blood out

\
pulmonary vessels are easily blocked by blood clots, fat or air bubbles

pleural cavities

separated by mediastinum, each one contains a lung

\
lined with serous membrane called pleura (any damage to membrane causes intense pain)

pleura

serous membrane lining the pleural cavities and consists of 2 layers
- parietal
- visceral

parietal pleura

membrane that lines inner surface of thoracic wall

visceral pleura

membrane that covers outer surfaces of lungs

pleural fluid

lubricates space between the parietal pleura and visceral pleura, stops layers from sticking together

respiration

2 integrated processes: external and internal

external respiration

body breathing (between alveoli and blood)

\
all process involved in exchange of O2 and CO2 with external environment

internal respiration

cell breathing; uptake of O2 and release of CO2 by cells

\
result of cellular respiration

external respiration steps

1. pulmonary ventilation (breathing)
2. gas diffusion (across blood air barriers in lungs, across capillary walls in other tissues
3. transport of O2 and CO2 (between alveolar capillaries, between capillary beds in other tissues)

hypoxia

low tissue oxygen levels

anoxia

complete lack of oxygen in tissues

pulmonary ventilation

(breathing) physical movement of air into and out of respiratory tract

\
provides alveolar atm

atmospheric pressure

weight of earth's atmosphere, has several important physiological effects (air pushing down on nose, lungs, alveoli)

Boyle's law

defines the relationship between gas pressure and volume (inversely related)

\
P = 1/V

\
drives pulmonary ventilation

air flow

flows from an area of higher pressure to an area of lower pressure

respiratory cycle

consists of an inspiration (inhalation) and expiration (exhalation)

what affects pulmonary ventilation?

- volume (increased lung space → low pressure → pulls air into lungs
- pressure
- thoracic cavity (muscles expand/contract the lungs)
- diaphragm/rib cage (contracts/pushes up → pushes on lungs → pushes air oout → expiation)

primary respiratory muscles

diaphragm and external intercostals

diaphragm

upward movement by this muscle → decreased lung volume

accessory respiratory muscles

more muscles recruited to expand/contract thoracic cavity

\
activated when respiration increases significantly

mechanics of breathing

- inhalation is always active, uses energy
- exhalation can be active/passive

normal atmosphere pressure

1 atm \= 760mm Hg

intrapulmonary pressure

or intra-alveolar pressure, difference from atmospheric pressure (outside body and inside alveoli) determines direction of airflow

intrapleural pressure

pressure in space between parietal and visceral pleurae, averages -4mm Hg

\
when parietal pleura is pulled, a negative pressure is created → pulls air into lungs

\
remains below atmospheric pressure throughout respiratory cycle

respiratory pump

created by cyclical changes in intrapleural pressure, assists in venous return to heart

pneumothorax

air enters pleural cavity inside of lungs due to injury to chest wall/ruptured alveoli

\
results in atelectasis

atelectasis

collapsed lung

\
\-4mm Hg no longer there to put tension on lungs to stay open → air enters interpleural space → layers start sticking to each other

resistance

force against which the lungs have to push to get air in/out

\
adjusted with bronchodilation and bronchoconstriction

compliance

a measure of expandability

\
if lowered, greater force required to fill lungs since they can't ventilate

compliance factors

- connective tissue of lungs
- level of surfactant production
- mobility of thoracic cage

respiratory rate

number of breaths per minute

tidal volume

amount of air moved per breath

respiratory minute volume

amount of air moved per minute, measures pulmonary ventilation

\
calculated as respiratory rate x tidal volume

COPD

common disease in smokers, consists of bronchitis and emphysema (elastic tissues start to be destroyed)

lung assessment

done through
- x-rays (consolidation of pneumonia, etc.)
- auscultation
- lung histology

anatomic dead space

volume of air remaining in conducting passages, doesn't exchange air

\
mouth, trachea, bronchi

aleveolar ventilation

amount of air reaching alveoli each minute

\
calculated as respiratory rate x (tidal volume - anatomic dead space)

for a given respiratory rate

increasing tidal volume increases alveolar ventilation rate

for a given tidal volume

increase respiratory rate increases alveolar ventilation rate

pulmonary function tests

measure rates and volumes of air movements

\
total lung volume is divided into a series of volumes and capacities

spirometer

instrument used to measure breathing and various volumes of lungs

\
nonemergent way of assessing lungs

gas exchange factors

depends on partial pressures of gases involved + diffusion of molecules between gas and liquid

expiratory reserve volume

additional amount of air capable of being exhaled

residual volume

amount of air in lungs after maximal exhalation, minimal volume in a collapsed lung

\
(never pushed out or leaves the lung)

inspiratory reserve volume

additional amount of air that can be inhaled

inspiratory capacity

tidal volume + inspiratory reserve volume

functional residual capacity

expiratory reserve volume + residual volume

vital capacity

expiratory reserve volume + tidal volume + inspiratory reserve volume

total lung capacity

vital capacity + residual volume

diffusion of gases

occurs in response to concentration gradients

\
rate depends on physical principles, or gas laws like Boyle's

\
direction (air into blood vs. blood into air) also determined by partial pressures and solubilities

Dalton's law

each gas contributes to total pressure in proportion to its relative abundance

partial pressure

pressure contributed by a single gas in a mixture, determines how much of that gas is going to be pushed in/out the alveoli

\
% of gas in air determines its partial pressure

* ex: O2 is 20.9% of air = 159 mm Hg

solubility of gases

CO2 is highly soluble, O2 is somewhat soluble, N2 has limited solubility

efficiency of gas exchange

- differences in partial pressure across blood air barrier are substantial
- distances involved in gas exchange are short
- O2 and CO2 are lipid soluble
- total surface area is large (more gas exchange)
- blood flow and airflow are coordinated

differences in partial pressure

acts like a concentration gradient; high partial pressure of O2 in alveoli, low partial pressure of O2 in blood arriving to lungs

\
O2 moves to oxygenate blood