Anatomy of Breathing

Sternocostal joints

connects sternum to costal cartilage, all synovial except for 1st which is cartilaginous

Costochondral

connects costal cartilage to ribs, all cartilaginous

Interchondral joints

connects costal cartilage, all synovial

anterior joints of thoracic cavity

sternocostal, costochondral, interchondral

posterior joints of thoracic cavity

costotransverse, costovertebral

costotransverse joints

Ribs attach to the transverse process of the thoracic vertebrae

costovertebral joints

Ribs attach to the body of the vertebrae

diaphragm

sheet of skeletal (voluntary) muscle that contracts to expand thoracic cavity and push on abdominopelvic cavity

intercostal muscles (location)

attach diagonally between neighbouring ribs
(external and internal muscles run in opposite directions)

external intercostal muscles (function)

contract to lift ribcage/expand thoracic cavity - normal and forced inspiration

internal intercostal muscles (function)

contract to pull ribcage down - only forced expiration

what is inside thoracic cavity

mediastinum (heart, vessels, pericardium), pleural cavities

body cavities (and lining)

thoracic and abdominopelvic both lined with double-layered secretory tissues called serous membranes that secrete serous fluid.

which wall of pleura secretes serous fluid?

parietal

structures passing through diaphragm

aorta, inferior vena cava, esophagus, sternum, 12th rib

accessory muscles

only activated for forced inspiration/expiration (further inc/dec the volume of thoracic cavity)

how do lungs expand as cavity does?

elastic lung tissue trying to recoil - must pull against
parietal pleura moves with (directly attached to) ribcage, serous fluid bond in pleural cavity pulling visceral pleura, pulling lungs

walls of the thoracic cavity 

ribs, vertebrae, sternum, diaphragm, base of neck

contracted diaphragm shape

flat

relaxed diaphragm shape

dome

what sort of cartilage is costal cartilage?

hyaline

muscles involved in (and what they do) normal inspiration

diaphragm and external intercostals contract

muscles involved in (and what they do) forced inspiration

diaphragm, external intercostals, accessory muscles contract 

muscles involved in (and what they do) normal expiration

diaphragm and external intercostal relax

why is normal expiration considered a passive process?

because no new work is being done, only relaxation

muscles involved in (and what they do) forced expiration

internal intercostal muscles and accessory muscles contract

how do muscles cause forced inspiration/expiration

further increase/decrease volume of thoracic cavity within shorter period, causing greater pressure gradient and causing more air to go in/out quicker