Respiratory System

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 CO2
levels 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