Chapter 17- Mechanics of Breathing

exchange of gases

major function of the respiratory system

by altering circulating CO2 levels

how does the respirtory system regulate pH?

heat and water loss

challenges of the respirtory system

regulation of pH, protection from inhaled pathogens, vocalization

other respiratory system functions

muscular pump

generates pressure gradients in the respiratory system

muscles that move the thoracic cavity

what makes up the respiratory pump?

pressure gradients

what drives the flow of air into and out of the lungs?

diameter of airways

what determines the resistance in the respiratory system?

external respiration

exchange of gases between atmosphere (atm) and blood

ventilation

exchange b/w atmosphere and lungs

inspiration

drawing air into lungs

expiration

pushing air out of lungs

mouth, nasal cavity, pharynx, larynx

what makes up the upper respiratory tract?

trachea, primary bronchi, bronchial tree

what makes up the lower respiratory tract?

alveoli

functional units for gas exchange

musculoskeletal pump

bones and muscles of the thoracic cavity

airways

air conducting system

pulmonary and cardiovascular systems

what components are involved in respiration?

spine, ribcage, chest wall

bones that play a role in ventilation

move bones and alter thoracic volume

role of muscles in respiration

diaphragm

forms floor, dome shaped muscle in relaxed state

intercostal muscles

muscles located between ribs

internal

which intercostal muscles cause expiration

external

which intercostal muscles cause inspiration

scalenes

move the 1st rib

pleural membrane

double membrane that surrounds lungs

parietal pleura

portion of pleural membrane adherent to thoracic wall

pleural space

filled with small amount of pleural fluid; eases movement of pleural
membrane as lungs expand, recoil

visceral pleura

portion of pleural membrane adherent to lung

pharynx

common passage for food, air, and liquids

larynx

vocal cords

trachea

flexible tube, held open with cartilage rings, branches into brochi

conduct, warm, humidify and filter air into lungs

function of airways

greatest, slowest

Air flow is ________ at the beginning of the airways, __________ at the end

ciliated

what type of epithelium is found in the trachea and bronchi?

saline and mucous layer

what covers the lumen of respiratory epithelium?

beat in waves to move mucous up and away from lungs

function of cillia

alveoli

air filled structures suited for gas exchange

elastin and collagen for elastic recoil

located between epithelial cells in the alveoli

Type I pneumocytes

thin epithelial cells lining most of the alveoli surface area

type II pneumocytes

-large cells that have smaller surface area, secrete surfactant
-move fluid out of air space

high, low

Pulmonary circulation is a _________ volume, _________ pressure system

25/8 mm/Hg

approximate pressure for pulmonary circulation

gas laws

state that gas, pressure, and volume are related to ventilatory properties

boyles’s law

shows pressure-volume relationships

-P1V1 = P2V2

increase

according to boyle’s law, if volume is decreased, the pressure will ___________

high, low

air moves from _________ pressure to _________ pressure

Dalton’s Law

total pressure exerted by a mixture of gases is sum of pressures exerted by individual gases

partial pressure

pressure of a single gas in a mixture

760 mmHg

what is atmospheric pressure?

multiply atm pressure by .21

if oxygen ins 21% of the Atm, how do you calculate partial pressure?

160 mmHg, 150 mmHg

what is the partial pressure of oxygen? with 100% humidity?

Partial pressures drive the diffusion of gasses across membranes

what is the significance of dalton’s law?

Respiratory cycle

airflow due to pressure gradients generated by actions of musculoskeletal pump

quiet breathing

used in resting conditions; expiration is passive

contraction expands thoracic cavity

function of diaphragm during quiet breathing

lift and expand the ribcage

function of scalene/external intercostals during quiet breathing

pleura

allow for lungs to move as the thoracic cage moves

forces on 2 membranes pulling in opposite directions

what generates negative intrapleural pressure?

fluid bond is broken causing the lung to collapse due to elastic recoil

what happens to the lung due to a pneumothorax

elastic recoil of lung and thoracic cavity

what does negative intrapleural pressure cause?

atm pressure is greater than alveolar pressure

why does air flow in to the lungs during inspiration?

brain

what controls activation of inspiratory muscles?

increased, decreases

during inspiration….____________ alveolar volume, ___________ alveolar pressure

atm pressure is less than alveolar pressure

why does air flow out of the lungs during expiration?

active expiration

requires additional actions of abdominal and internal intercostal muscles

decreased, increases

in expiration….. ____________ alveolar volume, ___________ alveolar pressure

compliance and elastance

what determines stretchability

compliance

measurement of forces needed to stretch lung, force generated by thoracic cavity movement

easy

high compliance = __________ to stretch

fibrosis

condition where lungs that are stiff, require high pressure to expand

emphysema

Condition where alveolar walls lost, lungs are loose and floppy with high compliance

inversely

how is elastane related to compliance?

elastance

result of elastic properties connective tissue inside the lungs

high

lungs with _________ elastance return to original shape easily

high

Elastance in lungs with fibrosis is……

low

Elastance in lungs with emphysema is……

inhalation, exhalation

compliance is associated with _________ while elastance is associated with _________

H-bonding between water molecules in the thin water based fluid lining alveoli

what caused surface tension to develop in the lungs?

air/water interface

where is surface tension found?

surfactant

reduces cohesive forces b/w water molecules, reducing ST and work
needed to expand alveoli

type II phneumocytes

secrete surfactant

surfactant not produced yet in premature infants

what causes newborn respiratory distress syndrome?

length of system, viscosity, radius of system

what factors affect airway resistance?

paracrine and nervous systems

what controls the radius of airways

trachea and bronchi

what accounts for most resistance int he airways?

parasympathetic signaling for bronchoconstriction

what does histamine cause?

sympathetic signals for bronchodialation

what do increased CO2 levels and epinephrine cause?

constriction of smooth muscle

what increases resistance of bronchioles?

total pulmonary ventilation

refers to volume of air moved by lungs per unit time (typically minutes)

tidal volume

volume of air in or out per breath

anatomical dead space

volume where air is not completely eliminated from body: not all of this is available for gas exchange, some is stuck in conducting pathway

150 mL per breath

approx volume of anatomical dead space

alveolar ventilation

volume of air available for gas exchange

= Tidal Volume – Anatomical Dead space

ventilation-perfusion matching

airflow matching blood flow to ensure adequate oxygenation of blood

constriction of bronchioles and mucus

what causes asthma

bronchiole dialators

how is asthma treated?