respiratory muscles

pleural effusion

fluid collection within the pleural cavity

intrapleural pressure

pleural cavity pressure becomes more negative as chest wall expands during inspiration. returns to initial value as chest wall recoils

forced expiration

rectus abdominis, internal intercostals, other lumbar, abdominal, and pelvic muscles -greatly increased abdominal pressure pushes viscera up against diaphragm increasing thoracic pressure, forcing air out

exhalation

-Pressure in lungs greater than atmospheric pressure -Normally passive - muscle relax instead of contract -Exhalation only active during forceful breathing

Conditions that decrease compliance

-Pulmonary fibrosis: deposition of inelastic fibers in lung (emphysema) -Pulmonary edema -Respiratory distress syndrome -Increased resistance to airflow caused by airway obstruction (asthma, bronchitis, lung cancer) -Deformities of the thoracic wall (kyphosis, scoliosis)

atelectasis

-collapse of part or all of a lung -can also result from an airway obstruction

3 factors influencing airway resistance

-diameter of the bronchioles - pulmonary compliance -surface tension

pneumothorax

-presence of air in pleural cavity -thoracic wall is punctured -inspiration sucks air through the wound into the pleural cavity -potential space becomes an air filled cavity -loss of negative intrapleural pressure allows lungs to recoil and collapse

Diaphragm

-prime mover of respiration -contraction flattens diaphragm and enlarging thoracic cavity and pulling air into lungs -relaxation allows diaphragm to bulge upward again, compressing the lungs and expelling air -accounts for two-thirds of airflow

internal and external intercostal muscles

-synergist to diaphragm -between ribs -stiffen the thoracic cage during respiration -prevents it from caving inward when diaphragm descends -contribute to enlargement and contraction of thoracic cage -adds about one-third of the air that ventilates the lungs

scalenes

-synergist to diaphragm -quiet respiration holds ribs 1 and 2 stationary

lung compliance

A measure of the ease with which lungs and thorax expand -The greater the compliance, the easier it is for a change in pressure to cause expansion -A lower-than-normal compliance means the lungs and thorax are harder to expand

Expiration

Air pressure within lungs greater than atmospheric

inspiration

Air pressure within lungs lower than atmospheric

accessory respiratory muscles

act mainly in forced respiration forced inspiration and expiration

inhalation

active-contraction of diaphragm , this is the most important muscle of inhalation. *external intercostals- contraction elevates ribs

factors that affect airflow

air pressure drives airflow ,resistance as well as surface tension, lung compliance , airway resistance ( bronchiole diameter)

respiratory distress syndrome ( hyaline membrane disease)

common in infants with gestation age of less than 7 months. not enough surfactant produced

Valsalva maneuver

consists of taking a deep breath, holding it by closing the glottis, and then contracting the abdominal muscles to raise abdominal pressure and pushing organ contents out -childbirth, urination, defecation, vomiting

bronchoconstriction

decrease in the diameter of a bronchus or bronchiole -histamine, parasympathetic nerves, cold air, and chemical irritants stimulate bronchoconstriction -suffocation from extreme bronchoconstriction brought about by anaphylactic shock and asthma

volume of breath

during each breath, the pressure gradients move 0.5 liter of air into and out of the lungs

forced inspiration

erector spinae, sternocleidomastoid, pectoralis major, pectoralis minor, and serratus anterior muscles and scalenes -greatly increase thoracic volume

lung collapse

if intrapleural and intrapulmonary pressures become equal, lung collapses, commonly caused by pneumonia, atelectases, pleural fluid build up

Bronchodilation

increase in the diameter of a bronchus or bronchiole epinephrine and sympathetic stimulation stimulate bronchodilation increase air flow

pleurisy/pleuritis

inflammation of the pleural, pleural excess fluid inhibits breathin

intrapulmonary pressure

pressure inside lung decreases as lung volume increases during inspiration;pressure increases during expiration

surfactant

reduces surface tension of water and reduces tendency for lungs to collapse