Mechanics of Breathing

cellular respiration

refers to the intracellular reaction of oxygen with organic molecules to produce carbon dioxide, water, and energy in the form of ATP

external respiration

the movement of gases between the environment and the body’s cells

ventilation

the movement of air between the atmosphere and the lungs

inspiration

the movement of air into the lungs

expiration 

the movement of air out of the lungs

upper respiratory tract

Mouth, nasal cavity, pharynx, larynx

lower respiratory tract

trachea, 2 primary bronchi, their branches, and the lungs

alveoli

a series of interconnected sacs and their associated pulmonary capillaries

alveoli

— form the exchange surface

Diaphragm

The skeletal muscle that forms the floor of the thoracic cage

Intercostal muscles

Muscles associated with the rib cage; used for breathing

sternocleidomastoids

inspiratory muscles that help elevate the upper ribs

• run from the head and neck to the sternum and first two rib

scalenes

Respiratory muscle that lifts the upper rib cage

pleural fluid

— lowers friction between membranes and holds lungs tight against the thoracic wall

pleura

The membranes that line the chest cavity and cover the outer surface of the lungs and form the pleural sacs

Pleural fluid

— creates a moist, slippery surface so that the opposing membranes can slide across one another as the lungs move within the thorax

upper airways, terminal bronchioles

The velocity of air flow is greatest in the — and lowest in the —

bronchioles

the total cross sectional area is the largest in the —

pharynx

where air enters the upper respiratory tract

• a common passageway for food, liquids, and air

larynx

The “voice box” that contains vocal cords

trachea

Main airway of the respiratory system

• Aka windpipe

• a semi-flexible tube held open by 15 to 20 C-shaped cartilage rings

Primary bronchi

The first two airways created by branching of the trachea

bronchioles

Small collapsible airways with smooth muscle walls 

• branch off of bronchi

body temperature

air is warmed to — before it reaches the alveoli

100%

water vapor is added to the air before it reaches the alveoli so the air is at — humidity

mouth, nose

Breathing through the — is not as effective at warming and moistening air as breathing through the —

type I

— alveolar cells function in gas exchange

type II

— alveolar cells function in producing surfactant

type II, type I

— alveolar cells are smaller and thicker than — alveolar cells

75 mL

At any given moment, — of blood is flowing through the pulmonary capillaries where gas exchange is taking place

25/8

Pulmonary blood pressure is low, averaging — mm Hg

fluid, short

There is minimal — in the lung interstitium, so the distance between the alveoli and the capillary endothelium is —

efficient

the lymphatic system in the lung tissue is very —

dalton’s law

total pressure equals sum of all partial pressures

boyle’s law

P1V1=P2V2

ideal gas law

PV=nRT

moles of gas, temperature

in the human body, we assume that — and — are constant so they are eliminated from the ideal gas equation

water vapor pressure, total pressure

To calculate the partial pressure of a gas in humid air, you have to subtract the — from the —

(Patm - PH2O) x % of gas

P(gas in humid air) =

respiratory cycle

1 inspiration followed by 1 expiration

500 mL

Average tidal volume during quiet breathing is about —

tidal volume

volume that moves during a respiratory cycle

inspiratory reserve volume

additional volume above tidal volume

expiratory reserve volume

forcefully exhaled after the end of a normal expiration

residual volume

volume of air in the respiratory system after a maximal exhalation

vital capacity

The maximum amount of air a person can exhale after taking the deepest breath possible.

IRV, ERV, tidal volume

vital capacity = — + — + —

total lung capacity

The maximum amount of air the lungs can hold after a person takes the deepest possible breath.

vital capacity, residual volume

TLC = — + —

directly

Flow of air is — related to pressure gradient

inversely

flow of air is — proportional to resistance

decreases

inspiration occurs when alveolar pressure —

increases

exhalation occurs when alveolar pressure —

-3 mm Hg

typical intrapleural pressure

decreases

during inspiration, intrapleural pressure —

returns to normal

during expiration, intrapleural pressure —

pneumothorax

when an opening is made in the sealed pleural cavity

compliance

ability to stretch

high

— compliance = stretches easily

low

— compliance = requires more force to stretch

low

restrictive lung diseases have — compliance

elastance

ability to return to resting volume when stretching force is released

surfactant

surface active agents that disrupt the cohesive force of water, keeping the alveoli inflated

radius

— is the most important factor in determining resistance

increases

bronchoconstriction — resistance

decreases

bronchodilation — resistance

bronchoconstrictor

histamine is a —

sympathetic

— input causes bronchodilation

parasympathetic

— input causes bronchoconstriction

Anatomic dead space

— is the portion of the respiratory system where air is conducted but no gas exchange occurs.

150 mL

avg volume of anatomic dead space = 

obstructive

— lung disease results from an increase in airway resistance

restrictive

— lung disease results from reduced lung compliance

obstructive

asthma, obstructive sleep apnea, emphysema, and COPD are — lung diseases

restrictive

pulmonary fibrosis and scoliosis are — lung diseases

forced vital capacity

taking in as much air as possible and then breathing it out as quickly as possible

FEV1

the volume of air leaving the airway in the first second when taking in as much air as possible and then breathing it out as quickly as possible is called the —

FEV1/FVC

— ratio distinguished between obstructive and restrictive lung diseases

restrictive

FEV1/FVC ratio does not change in — lung diseases

obstructive

FEV1/FVC is <80% in — lung diseases

expiration

in obstructive lung diseases, — is difficult

inspiration

in restrictive lung diseases, — is difficult

restrictive

in — lung diseases, inspiration is difficult

obstructive

in — lung diseases, expiration is difficult

ventilation

The term that is simply defined as breathing is —

alveoli

Gas exchange between the lungs and the atmosphere occurs in the —

pleural fluid

The — functions to hold the lungs to the thoracic wall

cross sectional area

Which key property of the bronchi increases as the average diameter of the passageways decreases?

chloride

The CFTR channel is an anion channel that is dysfunctional in patients with cystic fibrosis. It is required for the proper production of mucus in the respiratory tract. Which anion moves through the CFTR channel?

higher, lower

In the lungs, the blood flow rate is — and the blood pressure is —, than the blood flow rate and the blood pressure in other tissues.

80-90

Blood vessels cover approximately ________% of the alveolar

surface.

type II

— alveolar cells secrete surfactant

lower

The — respiratory tract includes all of the bronchial branches, the lungs, and the trachea.

lower

the trachea is part of the — respiratory tract

type I

— alveolar cells allow rapid diffusion of gases through their thin membranes.

trachea

The airway between the larynx and the primary bronchi is the —

directly, decreases

Flow of air is — proportional to a pressure gradient, and flow — as the resistance of the system increases.

moles, ideal gas constant, temperature

Which factor(s) from the ideal gas equation can be ignored in the human body?

expiratory reserve volume

The additional air that you can exhale after a normal exhale is the

__________.

decrease, increase

Relaxation of the respiratory muscles results in a — in thoracic volume and — in pressure in the lungs