Anatomy of the Thorax and Breathing Flashcards
Describe the body cavities
Our body cavities are lined with serous membranes
- double later of secretory tissue with fluid between the layers
- visceral layer on the organ (visceral serous pleura)
- parietal layer on the body wall (parietal serous pleura)
- thoracic cavity
- pericardium
- pleura x2
- abdominopelvic cavity
- peritoneum
Describe the anatomy of the thoracic cavity from the anterior view
Contains:
- mediastinum: heart, vessels, pericardium
- pleural cavities: lungs
Boundaries:
- anterior: sternum
- posterior: thoracic vertebrae
- lateral: ribs
- superior: base of neck
- inferior: diaphragm
Describe the anatomy of the thoracic cavity from the transverse view
Mediastinum - heart, vessels, pericardium
Pleural cavities - lungs are separate so if one stops functioning you have another
- visceral pleura
- pleural cavity
- parietal pleura
Describe the pressure changes in the thoracic cavity that drive ventilation
- Pressure is inversely proportional to volume
- So if we change the volume of the thorax, we change the pressure
What is Boyle’s Law?
P = 1/V (pressure is inversely proportional to volume)
Pressure measured by collisions:
- smaller space = more collisions = increased pressure
- larger space = less collisions = decreased pressure
- air will move to lower pressure space
Describe how Boyle’s Law works
- to breathe we need to establish a pressure gradient to make air move
- between breaths - pressure inside cavity = pressure outside (so no gradient)
- increased volume (therefore decreased pressure) - air flows in
- decrease volume (therefore increase pressure) - air flows out
Describe the anterior thoracic joints
Sternum to ribs
- via costal cartilage (hyaline)
- synovial joints
- cartilaginous joints
Sternocostal: between sternum and cartilage
- synovial
- EXCEPT 1st (which is cartilaginous)
Costochondral: (between cartilage and rib bones)
- cartilaginous
Interchondral: (between two bits of cartilage)
- synovial
Describe the posterior thoracic joints
They produce articulation between thoracic vertebrae and ribs
They are synovial joints
- Costotransverse (between rib and transverse process of vertebrae)
- Costovertebral (between rib and body of vertebrae)
Describe the muscles of respiration
- Respiratory muscle move the rib cage to allow us to breathe
- Primary muscles of respiration
- diaphragm
- intercostals
- accessory muscles
- active only when needed
Describe the diaphragm
- Sheet of skeletal muscle
- Separates the thorax from the abdomen
- Dome-shaped when relaxed
- Flattens when contracted
- Contraction expands the thoracic cavity, and compresses abdominopelvic cavity
- Has openings in it for the inferior vena cava, esophagus and aorta to go through
Describe the intercostal muscles
- Attach diagonally between neighbouring ribs
External intercostals: - lift ribcage and expand cavity
- inspiration - quiet and forced
Internal intercostals: - depress ribcage and decrease cavity
- expiration - forced only
Describe the accessory muscles
- Several muscles that attach to the thoracic cage
- just know its a group called the accessory muscles (don’t need to know all of their names)
Need to know their collective functions: - some accessory muscles increase cavity volume for forced inspiration
- other accessory cycles decrease cavity volume for forced expiration
Describe how the muscles of respiration move for inspiration
During normal ‘quiet’ inspiration:
- diaphragm contracts = flattens
- external intercostals contract = lifts ribs
During active ‘forced’ inspiration:
- as above, plus accessory muscles contract to further expand thoracic cavity
Describe how the muscles of respiration move for expiration
During normal ‘quiet’ expiration:
- passive process
- diaphragm relaxes = dome shaped
- external intercostals relax = ribs no longer lifted
During active ‘forced’ expiration:
- as above plus:
- internal intercostals contract = depress ribs
- 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
- The pleura make the lungs ‘stick’ to the thoracic wall (the fluid isn’t technically a glue but it helps form a fluid seal and results in sticking)
- Lungs expand during inspiration
- Lungs contract during expiration
