Ventilatory system Flashcards
structure
- nose
- mouth
- pharynx
- larynx: voice box
- trachea
- bronchi
- bronchioles
- lungs
- alveoli
anatomy of the trachea
Thin walled tube composed by a connective tissue & incomplete rings of cartilage
Smooth muscles
upper respiratory tract
nose, sinuses, pharynx & larynx
nose
hairs filter air, mucous and catches small particles
pharynx
pathway of air and food
larynx
voice box contains the epiglottis which keeps put food out of trachea
vocal chords
fibrous elastic bands that tuned with vocal muscles
lower respiratory tract
trachea & bronchial tree, lungs & diaphragm
trachea & bronchial tree
rigid tubing embedded with cartilaginous rings. smooth muscles can constrict these
lungs
bronchial tree ends in bundles of microscopic airsacs called alveoli (300 million of them)
alveoli
surrounded by blood capillaries where gas exchange occurs. (oxygen IN & carbon dioxide OUT)
nostrils
fringed with coarse hair which stains large particles out of the airstream and may also serve to protect the nasal cavity against chemicals and other harmful substances that are inhaled
functions of the conducting airways
- gas exchange
- filter, warm, humidify air
- low resistance pathway for
airflow - regulate pH in the body
- sounds & speech
- defense against chemicals & other harmful substances that are inhaled
interior of nasal cavity
contains projections of considerable surface area. These projections, nasal conchae, make the airstream turbulent and subsequently warm and hydrate it
air entering the trachea
thanks to the structure of nose, air is 100% humidified.
air passes through 3 portions of pharynx, which provides a low resistance path for airflow
function of larynx / voice box
larynx protects the trachea from invasion by foods and fluids
lungs
elastic spongy organs
they develop themselves at the end of bronchi
gas exchange
carried out by a complex of structures at the end of each terminal bronchioles
alveoli
simple thin walled structures which also have numerous thin walled outpocketings called alveoli
specialized for the function of gaseous exchange
respiratory terms
only contraction of diaphragm is needed but chest elevating muscles may aid during heavy breathing
only requires relaxation of inspiratory muscles but contraction of abdominals may force expiration
contraction
INSPIRATION / INHALATION
- muscle contractions increase volume of thorax
- greater volume of thoracic cavity lowers air pressure
- air moves in form atmosphere due to pressure difference
relaxation
EXPIRATION / EXHALATION
- volume of thorax decreases and air pressure in lungs increases
- air moves out to atmosphere due to pressure gradient
pulmonary respiration
- commonly referred to as breathing
- process of air flowing into lungs during inspiration & out of lung during expiration
- air flows because pressure differences between the atmosphere & gases inside the lungs
- air, like other gases, flows from a region with higher pressure to a region with lower pressure
- muscular breathing movements and recoil of elastic tissues create the changes in pressure that result in ventilation
3 pressures
- atmospheric pressure: pressure of air outside the body (760 mmHg)
- intrapulmonary pressure: pressure inside the alveoli of lungs (inspiration: 759 mmHg O2, expiration: 761 mmHg CO2)
- internal pressure: pressure within the pleural cavity
lung volumes & capacities
- tidal volume
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
- vital capacity
- minute ventilation
- total lung capacity
tidal volume
Volume of air breathed in or out per breath
inspiratory reserve volume
Volume of air that can be forcibly inspired after a normal breath
expiratory reserve volume
Volume of air that can be forcibly expired after a normal breath
residual volume
Volume of air that remains in the lungs after maximum expiration
vital capacity
Volume of air forcibly expired after maximum inspiration in one breath
minute ventilation
Volume of air breathed in or out per minute
total lung capacity
Vital capacity + residual volume
VO2
rate at which oxygen is taken into the body and used
VO2 max
excellent indicator of fitness. must be measured with special equipment
mechanics of ventilation
Need to know that a substance called pleural fluid lies between the lungs and the chest wall
When chest expands during breathing, the film of pleural fluid causes the membranous walls of lungs to be pulled outward along with chest walls.
This means the space within the lungs increases
Air molecules in the lungs now move momentarily farther apart, so that pressure of air in lungs falls below the pressure of atmosphere outside the body
Air from outside riches down the trachea and into lungs until two pressures are equal again
pleural fluid (definition)
fills the space between the two layers of pleural tissue
enlarges the cavity twofold
Observation of the skeleton reveals that each rib pivots about a vertebral joint.
If it is lifted upward it also swings outward, with thoracic cavity being enlarged anteriorly & superiorly.
This is the task in quiet breathing of the external intercostal muscles.
At the same time ribs are lifted, the diaphragm (the muscular floor of thoracic cavity) contracts downward, enlarging thoracic cavity inferiorly.
description for quiet breathing
Expiration is almost entirely a passive process that depends on elasticity of lungs & chest structures, as well as fluid film surface tensions within the lungs.
When inspiratory muscles are relaxed, air simply leaves the lung, much as it would leave an untied balloon.
active breathing
when one speaks or runs, abdominal muscles press upon abdominal contents, squeezing them upwards against diaphragm.
internal intercostal muscles oppose external intercostals & pull ribcage downward, helping decrease the thoracic cavity volume & forcibly empty lungs. diaphragm may also function in forcible expiration.
in laboured inspiration many muscles of upper trunk are also recruited.
indirect respiratory muscles
- pectoralis major and minor
- trapezius
- rhomboideus
regulation of breathing
involuntary breathing controlled in the primitive part of brainstem (medulla).
may also be controlled voluntary (cerebrum) but eventually involuntary control takes over.
chemoreceptors
send signals about blood pH, CO2 and O2 concentration to medulla.
regulations of pH, CO2, O2
- if pH goes down, or CO2 goes up, breathing increases.
- if pH goes up, or CO2 goes down, breathing decreases.
- O2 receptors = less impact on breathing rate vs. CO2.
- stretch receptors in lungs tell medulla when lungs are expanded during normal breathing & stop inhalation.
why do ventilation rates increase?
- breathing rate increases during exercise as expiratory center sends impulses to expiratory muscles (internal intercostals) which speeds up expiratory process;
- increase CO2 causes the acidity of blood to increase (decrease blood pH).
- change in acidity of blood is detected by chemoreceptors which send nerve impulses to respiratory muscles which increase rate of ventilation (faster / deeper).
2 ways exercise will influence
increase ventilation rate: greater frequency of breaths allows a more continuous exchange of gasses).
increase tidal volume (increasing volume of air taken in & out per breath allows more air in lungs be exchanged).
hemoglobin
Oxygen molecules bind to Iron containing a portion of hemoglobin and some Carbon Dioxide binds with certain amino acids in hemoglobin.
hemoglobin & oxygen
- about 98% of oxygen in blood is transported by hemoglobin as oxyhemoglobin, within red blood cells.
- protein that allows oxygen to bind to a red blood cell.
- contains a central iron ion which hold up 4 oxygen atoms.
- these oxygen atoms are diffused into tissues once they reach their target.
- while they are diffusing they are picking CO2 & returning it to lungs so you can exhale it.
- only 20% of hemoglobin carries CO2.
- most CO2 is carried in plasma and forms carbonic acid with water.
- excess CO2 in blood will cause blood pH to drop.
structure of alveoli
- walls are very thin (1 cell)
- huge surface area so allows for greater uptake of oxygen
- supplied by a dense capillary network
process of gaseous exchange at alveoli
- carried out by a complex of structures at end of each bronchioles.
- oxygen exchange occurs
- these alveoli inflate and deflate with inhalation & exhalation.
- elastic recoil helps in exhalation.
- gasses move by diffusion from where they have a high concentration to where they have a low concentration.
- alveoli create a pressure gradient
- once alveoli fill up with air during inhalation oxygen diffuses from air in alveoli and into blood.
- CO2 diffuses from the arriving venous blood and into air which exits the body during exhalation.
importance of surfactants
- alveolar lining is moist (H2O)
- because H2O is a polar liquid it has high surface tension (like magnets).
- surface tension of H2O resists expansion of alveoli and can cause them to collapse.
