Purposes of respiration
#1 reason is for gas exchange, secondary reason includes receptors for smell, speech production and filters, warms and moistens incoming air
Respiration
two exchanges of gas; between atmosphere and blood, between blood and body tissues
4 processes of respiration
pulmonary ventilation, external respiration, transport of respiratory gases, internal respiration (ALL supply body with o2 and get rid of co2)
pulmonary ventilation
moving air into and out of the lungs
external respiration
exchange of oxygen and co2 between pulmonary blood and lungs
transport of respiratory gases
transport of o2 and co2 in blood
internal respiration
exchange of o2 and co2 between blood and body tissues
upper region respiratory organs
nose, nasal cavity, pharynx
lower region respiratory organs
larynx, trachea, bronchial tree, lungs, alveoli
two functional zones
respiratory and conducting zones
respiratory zone
actual site of gas exchange; microscopic structures respiratory bronchioles, alveolar ducts, and alveoli
conducting zone
travel for air to reach sites of gas exchange, clean, filter, warm, moisten incoming air; includes all other non-microscopic respiratory structures
functions of the nose
-filters, warms, moistens incoming air -provides an airway for respiration -resonating chamber for speech -olfactory receptors (SMELLL)
2 regions of the nose
external nose & nasal cavity
What filters coarse particles from inspired air?
the vibrissae in the vestibule
Olfactory Mucosa
a small patch lines the superior nasal cavity and contains olfactory receptors
Respiratory Mucosa
filter air (lysozyme and defensin secretion), cilia move mucus posteriorly to throat, high water content moistens air, capillary plexuses warm incoming air, lots of sensory nerves
structure of respiratory mucosa
pseudostratified ciliated columnar epithelial tissue goblet cells
pharynx
muscular tubes that connect, 3 regions
3 regions of pharynx
nasopharynx, oropharynx, laryngopharynx
nasopharynx
purely air passage; lined with pseudostratified columnar epithelium; contain pharyngeal tonsils;
oropharynx
passage for food & air; lining stratified squamous epithelium; contains palatine tonsils in lat. walls; lingual tonsils on posterior surface
isthmus of fauces
opening to the oral cavity
laryngopharynx
passageway for food & air; lining stratified squamous epithelium; posterior to epiglottis :) extends to larynx, and continuous with esophagus
larynx
airway! opens into laryngopharynx; connects pharynx to trachea!, air passageway that prevents food from getting into the respiratory tract; voice production
trachea
air passageway; warms, moistens air; flexible tube running down and branches into bronchial tree
9 cartilages of the larynx
all hyaline cartilage except epiglottis; epiglottis is elastic cartilage; review slide 26 of ppt
adam's apple
thyroid cartilage with laryngeal protrusion
epiglottis
covers the laryngeal cartilage during swallowing
Tracheal Wall
mucosa (pseudostratified ciliated columnar epithelium with goblet cells) --> submucosa --> hyaline cartilage --> adventitia
Trachea Structures continued...
c-ring cartilages --> reinforce trachea; prevent it from collapsing despite pressure changes during breathing
Why is the trachea incomplete on the posterior end?
allows esophagus to bulge anteriorly when swallowed food goes down it
What does the trachealis muscle do?
connects posterior parts of the cartilage rings; contracts during coughing to expel mucus
Bronchial tree
primary right & left bronchi --> secondary/lobar bronchi --> tertiary/ segmental bronchi --> segmental repeatedly divide till you have bronchioles --> terminal bronchioles (smallest, less than 0.5 mm)
Lobes of the Lungs
Left Lung: two lobes Right Lung: three lobes
Which bronchus is most likely to get objects stuck?
right because it is more vertical, wider, shorter
Structure of Bronchial Tree
as it progresses, cartilage decreases and smooth muscle increases; epithelium decreases in thickness, goblet and cilia cells decrease
alveoli
around 300 million alveoli; account for most of lung volume; main site for gas exchange; lots of surface area
alveoli walls
simple squamous epithelium
respiratory membrane
.5 micrometer thick air-blood barrier; alveolar and pulmonary capillary walls (+ their fused basement membranes)
Which of the 4 respiratory processes occurs across the respiratory membrane?
external respiration
what happens during external respiration?
exchange of respiratory gases between the lungs and pulmonary blood takes place by diffusion across the respiratory membrane
Walls of alveoli & pulmonary capillaries
both composed of simple squamous epithelium
alveolar walls
simple squamous epithelium (type 1 cells), type 2 alveolar cells --> secrete surfactant and antimicrobial proteins
3 significant features of alveoli
surrounded by elastic fibers, open pores that allow air pressure to be equalized, house macrophages that keep alveoli sterile
lung features
occupy all of the thoracic cavity except the mediastinum; apex, base, costal surface, root, hilum
left lung
2 lobes; oblique fissure; cardiac notch to accommodate the heart
right lung
three lobes; oblique and horizontal fissures
parietal pleura
lines thoracic wall and superior face of diaphragm
visceral pleura
covers external lung surface
pleural cavity
filled with pleural fluid that provides lubrication to reduce friction when breathing, provides tension so layers dont seperate
relationship between pleura
relationship between parietal and visceral pleura is vital to breathing; keeps the lungs inflated and allows them to expand; The strong adhesive force between the visceral and parietal pleura; fluid secures them together. the lungs cling tightly to thorax wall which keeps them inflated
pulmonary circulation
low pressure, high volume; pulmonary arteries contain deoxygenated blood that goes into pulmonary capillary networks surrounding alveoli; then pulmonary veins contain oxygenated blood and carry towards heart to be distributed
bronchial arteries
arise from aorta and deliver blood to lungs via hilum; supply all lung tissues except the alveoli; bronchial veins anastomose with pulmonary veins that carry most venous blood back to the heart
innervation of the lungs (parasympathetic and sympathetic)
parasympathetic: bronchioles constrict (bronchoconstriction) sympathetic: bronchioles dilate (bronchodilation)
Ventilation
inspiration and expiration
inspiration
active process that moves air into the lungs from atmosphere; thoracic volume expands & diaphragm flatttens and contracts; volume increases, pressure decreases
expiration
moves air out of the lungs from atmosphere; chests contracts & diaphragm relaxes and rises; volume decreases, pressure increases
Atmospheric Pressure
P(atm); pressure surrounding the body due to external air; 760 mmHg at sea level; respiratory pressures described relative to this
Intrapulmonary Pressure
P(pul); intrapulmonary or intraalveolar pressure; pressure in the alveoli that fluctuates with breathing; eventually equalizes with P(atm)
Intrapleural Pressure
P(ip); pressure in pleural cavity that fluctuates with breathing; always negative!! so that means its less than P(atm) and P(ip)
What causes negative P(ip)?
caused by opposing forces! 2 inward forces promote lung collapse, 1 outward force promotes lung enlargement; however, neither force wins bc of pleural relationship
two inward forces acting to create P(ip)
act to pull lungs away from thorax wall; elastic recoil of lungs act to decrease the size of the lungs & surface tension of alveolar fluid reduce alveolar size
one outward force acting to create P(ip)
elasticity of chest wall pulls thorax outward
Transpulmonary Pressure
P(pul)-P(ip); keeps lungs from collapsing; the greater, the larger the lungs; if P(pul)=P(ip), lungs will collapse
Atelectasis
Lung Collapse due to pneumothorax
pneumothorax
abnormal presence of air in the pleural cavity resulting in the collapse of the lung; when P(ip) = P(pul) or P(atm)
Pressure Gradient
gases flow down a pressure gradient to equalize the pressure
Boyle's Law
pressure varies inversely with volume; as volume increases, pressure decreases and vice versa
inspiration & pressure
P(pul) pressure decreases due to increase in the intrapulmonary volume; results in airflow into lungs
what is the most important muscle in breathing?
diaphragm! producing the volume changes and is stimulated by phrenic nerve; when it contracts it moves inferiorly and flattens out which increases superior-inferior dimensions of cavity
External Intercostals
lift rib cage and pull sternum superiorly! increases lateral and anterior-posterior dimensions of cavity
what are the inspiratory muscle?
resting inspiration--> external intercostals (11 pairs) & diaphragm forced inspiration--> resting muscles + scalenes and sternocleidomastoid inspiration involves phrenic & intercostal nerves
expiration
quick passive process; inspiratory muscles relax and thoracic volume decreases, increasing p(pul), causing air to flow out of the lungs down the pressure gradient FORCED expiration uses abdominal and internal intercostal muscles
expiration is a passive process at rest
during expiration, the elastic recoil of the lungs and the surface tension decreased the volume and increased the pressure causing air to flow out
physical factors influencing pulmonary ventilation
airway resistance, alveolar surface tension and lung compliance; affect the amount of energy required for ventilation and the ease of air passage
airway resistance
friction is a major non-elastic source of resistance to gas flow; encountered in respiratory passages; flow = pressure/resistance **usually insignificant because as alveoli branch, the surface area gets larger and accounts for the decrease in resistance
alveolar surface tension
surface tension: attract liquid molecules together @ gas-liquid interface due to water having a high surface tension and water being present on alveoli, it causes them to be reduced to their smallest size
alveolar film is not pure water! it contains _____.
surfactant; a detergent like lipid-protein complex produced by type 2 cells that decreases surface tension, allowing for less energy to overcome forces needed to expand the lungs (discouraging alveolar collapse)
Insufficent Respiratory Distress Syndrome
IRDS is common in infants; Fetal lungs do not produce adequate amounts until the last 2 months of development
What is lung compliance?
"stretchiness" or the ease that the lungs/thoracic cavity can be expanded higher=easier to expand; low=harder to expand and more energy is needed normally high due to 1. elasticity of lung tissue 2. surfactant
conditions that decrease lung compliance
•Leads to formation on non-elastic scar tissue (fibrosis) •Produces surfactant deficiency (premature birth, near-drowning) •Decreases flexibility of thoracic wall/cage •Destroys lung tissue (emphysema) •Fills lungs with fluid (pneumonia) •Interferes with lung expansion (pneumothorax)
What controls breathing?
higher brain centers, chemoreceptors, other reflexes
neural controls of breathing
neurons of pons and medulla; medulla is more important because it sets the rhythm because ventral and dorsal respiratory group!
Ventral Respiratory Group (medulla resp. center)
rhythm generating and integrative center more important than Dorsal Respiratory Group (DRG) Sets eupnea --> normal resp. rate & rhythm = 12-16 breaths per min inspiratory neurons --> excite phrenic nerve and ic muscles expiratory neurons --> inhibit these inspiratory neurons
Dorsal Respiratory Group (medulla resp. center)
integrates input from peripheral stretch and chemoreceptors *sends this information to VRG
Potine Respiratory Centers
influence/modify VRG smooth transition between inspiration and expiration transmit impulses to VRG-->modify and fine-tune breathing rhythms during vocalization, sleep, exercise
depth and rate of breathing
depth=how actively the respiratory center stimulates the respiratory muscles rate= how long the inspiratory center is active
factors that affect the depth and rate of breathing
changing levels of CO2, O2, and H+ (chemicals)!!! -->sensed by central and peripheral chemoreceptors Excitatory or increase frequency of impulses to respiratory muscles = deeper, faster breathing Inhibitory, decrease frequency of impulses = shallow & slower breathing
Chemical factors regarding breathiner
if blood Pco2 levels increase, co2 accumulates in brain which produces carbonic acid which releases hydrogen ions in the brain causing the pH to drop! Hydrogen ions stimulate chemoreceptors which increase the rate and depth of breathing which results in less co2 in the blood and ph rises
Major chemical stimulus effecting respiratory rate
CO2
While it is rising blood CO2levels that act as the initial stimulus, ________________________!!!
it is rising H+ levels generated within the brain that stimulate the central chemoreceptors
hyperventilation
increased rate and depth of breathing that exceeds the body's need to remove co2 leads to hypocapnia (Decreased co2 lvls) can lead to cerebral vasoconstriction and cerebral ischemia which leads to dizziness and fainting
influence of P(o2)
Arterial Po2 must drop substantially (to 60 mm Hg) to stimulate increased ventilation because a lot of oxygen can bind to hemoglobin
influence of arterial pH
mediated by peripheral chemoreceptors bc H+ cannot cross blood-brain barrier decreased pH due to increased co2 retention metabolic causes resp. controls attempt to influence rate by enacting an increased depth and rate of breathing
Hypothalamic Controls
Limbic system can affect the rate/depth of breathing ex: breathing when scared or angry
cortical controls
direct signals from cerebral motor cortex that bypass medullary controls...conscious (voluntary) control over rate/depth of breathing
Dalton's Law of Partial Pressures
Total pressure exerted by mixture of gases = sum of pressures exerted by each gas Each gas in a mixture of gases exerts its own pressure as if the other gases were not present.
Henry's Law
-each gas dissolves in proportion to its partial pressure -amount of gas that will dissolve depends on solubility and temperature
relationship between temp and solubility
as temp rises, solubility decreases