HUBS192 Lecture 16 - Respiratory System III: Anatomy of the Thorax & Breathing (Ventilation) Flashcards
what are the 2 body cavities of the trunk?
1) thoracic cavity
2) abdominopelvic cavity
where is the thoracic cavity located?
part above the diaphragm that sits at the base of the ribcage
what are all body cavities lined with?
lined with a serous membrane (a double layer of secretory tissue with fluid between layers)
what is a serous membrane?
a double layer of secretory tissue with fluid between layers that provides frictionless movement
what are the 2 layers of the serous membrane?
1) visceral layer on the organ
2) parietal layer on the body wall
what are the 2 membranes found within the thoracic cavity that provide frictionless movement other than the serous membranes?
1) pericardium
2) pleura
what is the pleura?
the membrane that surrounds the lungs to allow the lungs to move frictionlessly when they expand
what is the membrane found in the abdominopelvic cavity that provides frictionless movement other than the serous membranes?
1) peritoneum
why is there 2 pleural cavities?
1 for each of the lungs
what are the bony structures that form the thoracic cavity?
- mediastinum (where the heart, vessels and pericardium are found)
- pleural cavities
what is found within the mediastinum?
where the heart, vessels and pericardium are found
what is the function of the thoracic cage?
bony structures that provide protection but also have the ability to move
what are the 5 boundaries of the sternum?
1) anterior: sternum
2) posterior: thoracic vertebrae (12 thoracic vertebrae)
3) lateral: ribs (links the sternum and the thoracic vertebrae)
4) superior: base of the neck
5) inferior: diaphragm
what is the majority of the thoracic cavity taken up by?
taken up by the lungs
what is the hilum of the lung?
where blood vessels, nerves and lymphatics go out
- but more importantly where the primary bronchi vessels enter
what 3 layers compose the pleural cavities (from superficial to deep)?
1) pleural cavity
2) parietal pleura (sits against the thoracic wall= frictionless movement)
3) visceral pleura (sits against the lungs)
what is the advantage of having 2 pleural cavities?
lungs are seperate so if one stops functioning, you have another
what is ventilation driven by?
ventilation is driven by pressure changes in the thoracic cavity
what is the relationship between pressure and volume?
pressure is inversely proportional to volume so if we change the volume of the thorax, we can change the pressure
what occurs to lungs in terms of volume during inhalation and expiration?
1) inhalation = volume increases
2) expiration = volume decreases
what is equation for Boyles law?
P = 1/V
what is pressure measured by?
collisions
what happens to pressure in a smaller space?
smaller space = more collisions = increased pressure
what happens to pressure in a larger space?
larger space = less collisions = decreased pressure
what is the relationship between the place where air will always move and pressure?
air will always move to the place with lower pressure
what is the pressure gradient established by breathing to make air move: between breaths, increasing volume and decreasing volume?
1) between breaths the pressure inside cavity is equal to the pressure outside the cavity, no gradient
2) increased volume (therefore a decrease in pressure), air will flow in
3) decreased volume (therefore an increase in pressure), air will flow out
what is costal (hyaline) cartilage?
extensions of cartilage from the ribs as the bony structures do not fully attach
-links the ribs to the sternum
how are the ribs attached to the costal cartilage?
by costochondral cartilage joints (between the rib and the cartilage)
- provides very little movement
what are the sternocostal joints (anterior thoracic cavity)?
joint between the sternum and the ribs
- there are 7 sternocostal joints on each side and
- numbers 2-7 are synovial joints (allow a lot of movement)
- number 1 is a cartilaginous joint
what are interchondral joints (anterior thoracic cavity)?
the joints between the ribs at the bottom of the ribcage that attach to the cartilage of neighbouring ribs
- joints between the cartilage
- synovial joints (very moveable)
what is the main joint type on the anterior and posterior side of the ribcage?
synovial joints
what is the relationship between thoracic vertebrae and ribs on the posterior side of the thoracic cavity?
the thoracic vertebrae and ribs both articulate though synovial joints
- each rib has 2 articulation points with the vertebrae
what is the first articulation between the ribs and the vertebrae?
the costotransverse joint that is between the rib and the transverse process of vertebrae
what is the costovertebral joint?
joint between the rib and the body of the vertebrae
why are most of the joints in the thoracic cavity synovial?
so that the ribcage can be lifted up to allow an increase in volume
what is the name of the law that describes the relationship between pressure and volume of a gas?
Boyle’s law
which of the thoracic joints are not synovial joints?
costochondral and first sternocostal joint
what is the function of the muscles of respiration?
respiratory muscles move the rib cage to allow us to breathe (increase in volume)
what are the primary inhalation muscles?
1) diaphragm
2) intercostals (2 layers)
what are 2 the functions of accessory muscles?
1) increase cavity volume for forced inspiration (inhalation) by contraction
2) decrease cavity volume for forced expiration
what is the diaphragm?
a sheet of skeletal muscle that separates the thoracic cavity (thorax) from the abdominal cavity (abdomen)
how does the shape of the diaphragm change from relaxation to contraction?
- dome-shaped when relaxed
- flattens when contracted
what is the effect of contracting the diaphragm?
contraction expands the thoracic cavity and compresses the abdominopelvic cavity
where do the intercostal muscles attach?
attach diagonally between neighbouring ribs (sit between the ribs)
what are the 2 functions of the external intercostal muscles?
1) the external intercostals run diagonal therefore during contraction they lift the ribcage upwards expanding the cavity
2) inspiration (inhalation): quiet and forced breathing
what are the 2 functions of the internal intercostal muscles?
1) run the opposite direction from the external intercostals therefore during contraction they pull the ribs closer together and downwards, bring the ribcage inwards
2) expiration: forced breathing only
what is quiet breathing?
breathing under unconscious thought
what is forced breathing?
breathing under physical activity that requires more air than quiet breathing therefore forcing the use of more air
what are the accessory muscles? (not their names)
several muscles that attach to the thoracic cage that are only activated when required
what happens during normal or ‘quiet’ inhalation (inspiration)?
- diaphragm contracts = flattened shape
- external intercostals contract = lifts the ribs
what happens during active or ‘forced’ inhalation (inspiration)?
- diaphragm contracts = flattened shape
- external intercostals contract = lifts the ribs
- accessory muscles contract to further expand the thoracic cavity
what happens during normal or ‘quiet’ expiration?
- passive process
- diaphragm relaxes = dome shaped
- external intercostals relax = ribs no longer lifted
what happens during active or ‘forced’ expiration?
- passive process
- diaphragm relaxes = dome shaped
- external intercostals relax = ribs no longer lifted
- internal intercostals contract = depress ribs (pull in closer)
- accessory muscles contract to further decrease cavity volume
how do the lungs expand as the cavity does?
lung tissue is elastic and always trying to recoil (become as small as possible) therefore the pleura make the lungs ‘stick’ to the thoracic wall
when do the lungs expand?
expand during inspiration (inhalation)
when do the lungs become smaller?
decrease during expiration
what are the 2 functions of pleural fluid?
1) provides a slippery surface for frictionless movement against other structures
2) fluid bond causes lungs to ‘stick’ to thoracic wall
how does thoracic wall movement result in lung movement?
increase in volume of the thorax –> increase volume of the lung –> decrease pressure in the lung –> air flows in
what are the muscles involved in needing to take an active or ‘forced’ breath in?
diaphragm, external intercostals and accessory muscles contract to increase thoracic cavity volume as much as possible
what are the muscles involved in needing to take an active or ‘forced’ breath out?
internal intercostals and accessory muscles contact (and the diaphragm relaxes) decrease thoracic cavity volume as much as possible to force air out
