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