Respiratory System:Basic Anatomy
! Air movement from environment to lungs ! in external nares of
nose ! moves past nasal
conchae − warms air because of
many capillaries − sense of smell from
olfactory epithelium
Respiratory Basic Anatomy! pharynx
! nasopharynx − lined by ciliated pseudo-
stratified epithelium with Goblet Cells (mucus pushed down to mix with food)
− opening of Eustachian tube ! oropharynx: stratified non-
ciliated squamous epithelium because food mixed in with air here
! laryngopharynx
Respiratory Basic Anatomy
! larynx (voice box) ! voice produced as air passes
around vocal folds (true vocal cords) through glottis, pitch varies as tension on cords varies
! epiglottis: flap that covers larynx when swallowing, so that food doesn't pass into lungs but is diverted down esophagus
Larynx
Respiratory Basic Anatomy
! trachea ! has “C” shaped ring
of hyaline cartilage for strength
! inner layer (mucosa) consists of ciliated pseudostratified epithelium with Goblet Cells (mucus moved up to mix with food)
Respiratory Basic Anatomy
! trachea ! has “C” shaped ring
of hyaline cartilage for strength
! inner layer (mucosa) consists of ciliated pseudostratified epithelium with Goblet Cells (mucus moved up to mix with food)
Respiratory Basic Anatomy! bronchi
! left and right primary bronchi ! secondary bronchi (total of
5, one enters each lung lobe)
! tertiary bronchi (10/lung): supplies a bronchopulmonary segment, which is made up of lobules
! bronchioles (cartilage ends, smooth muscle starts to appear (spasm of this muscle can cause asthma)
! terminal bronchioles
Respiratory Basic Anatomy! lungs: from just above
clavicle to diaphragm ! apex (top) ! base (bottom) ! hilus: area where bronchi,
blood vessels, etc. enter lung
Respiratory Basic Anatomy! lungs
! terminal bronchioles give rise to respiratory bronchioles, then alveolar ducts, then alveolar sacs, then alveoli
Respiratory Basic Anatomy! alveoli: structure in which gases are exchanged ! alveolar structure: endothelial tissue with basement
membrane, lots of elastic fibers, some macrophages present
Respiratory Basic Anatomy! 300 million alveoli make up a
total of 70 m2 of surface area ! alveolar-capillary membrane is
only 0.5 µ thick ! allows for diffusion of CO2 and O2
Neural Control of Breathing! brain respiratory centers:
! dorsal respiratory group (DRG) in medulla
! causes inspiration ! ventral respiratory group (VRG) in
medulla ! important during heavy breathing ! both inspiratory and expiratory
! pneumotaxic center in pons ! inhibits DRG to end inspiration ! when active, short, faster breaths ! when less active, deep, slower breaths
Neural Control of Breathing! input to the respiratory centers:
! central chemoreceptors in medulla ! peripheral chemoreceptors in
carotid bodies and arch of aorta ! stretch receptors in bronchi and
bronchioles ! Hering-Breuer Reflex prevents
excessive inspiration ! not usually very important in adults,
but may be in infants ! irritant receptors in airway epitelium
cause bronchorestriction and coughing
! smoke, allergens, cold air, etc.
Pulmonary Ventilation (Breathing)! inspiration at rest is due mostly to
contraction of diaphragm ! deep inspiration (as when
exercising) also uses accessory muscles like external intercostals and sternocleidomastoid
! expiration at rest is passive ! no energy required ! just relax diaphragm
! expiration during exercise uses accessory muscles like internal intercostals
Pulmonary Ventilation: Breathing! Universal Gas Law:
! PV = nRT ! at a constant temperature, pressure and volume
are inversely related ! as volume of a chamber goes up, pressure within
that chamber goes down ! as volume of a chamber goes down, pressure
within that chamber goes up
Pulmonary Ventilation: Breathing! Air movement occurs due to
pressure gradients!
! two gradients we must consider: ! Alveolar pressure (Palv)
and atmospheric pressure (Patm)
! (pleural pressure + elastic recoil pressure) and alveolar pressure gradient
Pulmonary Ventilation: Breathing! Alveolar pressure and
atmospheric pressure gradient
! if atmospheric pressure > alveolar pressure, air will flow into the alveolus (inspiration)
! if atmospheric pressure < alveolar pressure, air will flow out of the alveolus (expiration)
Pulmonary Ventilation: Breathing! (pleural pressure + elastic
recoil pressure) and alveolar pressure
! if (pp + erp) > alveolar pressure, the alveolus will be squeezed smaller, resulting in an increase in alveolar pressure until it equals (pp + erp)
! if alveolar pressure > (pp + erp), the alveolus will expand, resulting in a decrease in alveolar pressure
Pulmonary Ventilation: Breathing! at rest:
! atmospheric pressure = 760 mmHg
! alveolar pressure = 760 ! pleural pressure = 756 ! elastic recoil pressure = 4
! pp + erp = 760 ! both pressure gradients are at
net 0 pressure, so no air moves
Pulmonary Ventilation: Breathing!to inspire at rest, contract the diaphragm:
! when diaphragm contracts, pleural volume goes up
! pleural pressure goes from 756 to 750
! pp + erp = 750 + 4 =754 ! alveolar pressure still
equals 760, so ! Palv > (pp + erp) ! alveolus expands due
to pressure gradient
Pulmonary Ventilation: Breathing!as the alveolus expands, Palv drops
! from 760 to 754
! this creates a second pressure gradient:
! Patm > Palv
! air now flows in from the atmosphere to the alveolus
!expiration is essentially the reverse of this process
! as the diaphragm relaxes, pleural volume decreases, increasing Ppl
!inspiration during exercise uses accessory muscles to create a greater increase in pleural volume during inspiration, and a greater decrease during expiration
Restrictive vs. Obstructive Disorders! restrictive disorders
! alveoli are restricted from inflating ! pneumonia ! lung scarring
! obstructive disorders ! airway is obstructed
! asthma ! chronic bronchitis ! emphysema
! really both restrictive and obstructive ! lungs become fibrotic and lose
elastic fibers ! air passages collapse at end of
inspiration
Lung Volumes and Capacities! tidal volume
! inspiratory and expiratory reserve
! residual volume
! total lung capacity
! vital capacity
! reduced in restrictive disorders
! inspiratory capacity
! FEV1
! reduced in obstructive disorders
Gas Exchange: Movement of O2 and CO2! external respiration: exchange between
alveolus and capillaries of lung
! internal respiration: exchange between capillaries at tissues throughout body and extracellular fluid
! gases (O2 and CO2) move due to concentration gradients
! fluids (like water) move due to pressure gradients
! whenever a concentration gradient exists, O2 and CO2 will move until the gradient is wiped out
! alveolar air and alveolar capillaries
! tissue capillaries and tissue extracellular fluid
! “deoxygenated” blood isn’t!!!
! still has PO2 = 40 mmHg
Gas Exchange: Movement of O2 and CO2! bigger concentration gradients cause
gases to diffuse faster
! hyperbaric chambers
! smaller concentration gradients cause gases to diffuse more slowly
! high altitude
Systemic Gas Exchange• oxygen transport: nearly 100%
on hemoglobin
• CO2 transport more complex:
– 7% as CO2 dissolved in plasma
– 23% on hemoglobin (globin part)
– 70% as HCO3- – Haldane Effect: in
presence of O2, less CO2 binds to hemoglobin
Alveolar Gas Exchange
• reverse of systemic gas exchange
Oxyhemoglobin Dissociation Curves• oxyhemoglobin dissociation curve
predicts when hemoglobin will release oxygen
– intrinsic property of hemoglobin molecule
– at normal temp and pH: – 98.5 % saturation at arterial blood
(PO2 = 95 mmHg) – 75 % saturation at venous blood
(PO2 = 40 mmHg) • shifts to right with increases in:
– body temp – CO2 – acidity (pH drop)
– called the Bohr Effect
Oxyhemoglobin Dissociation Curves
• Comparison of resting conditions to exercise