Lecture 16: ANATOMY OF THE THORAX AND BREATHING Flashcards
What are our body cavities lined with?
Serous membranes
Where is the visceral layer of a serous membrane found?
On the organ
Where is the parietal layer of the serous membrane found?
On the body wall
What are the serous membranes in the thoracic cavity?
Pericardium (surrounds heart) and pleura (surrounds lungs)
What is the serous membrane in the abdominopelvic cavity?
Peritoneum
What does the thoracic cavity contain?
Mediastinum in the middle and pleural cavities either side
What is in the mediastinum?
Heart, vessels and pericardium
What is in the pleural cavities?
Lungs
What is the anterior boundary of the thoracic cavity?
Sternum
What is the posterior boundary of the thoracic cavity?
Thoracic vertebrae
What is the lateral boundary of the thoracic cavity?
Ribs
What is the superior boundary of the thoracic cavity?
Base of neck
What is the inferior boundary of the thoracic cavity?
Diaphragm
What is the relationship between pressure and volume?
Pressure is inversely proportional to volume
What happens if we change the volume of the thorax?
We change the pressure
What happens to volume and pressure during inspiration?
volume increases and pressure decreases
What happens to volume and pressure during expiration?
volume decreases and pressure increases
What is Boyles law?
P=1/V
What is pressure measured by?
Collisions
What does a smaller space mean?
More collisions and increased pressure
What does a bigger space mean?
Less collisions and decreased pressure
Where will air move?
To a lower pressure space
What needs to be established to breathe?
A pressure gradient so air can move
What is the pressure between breaths?
Pressure inside cavity is equal to pressure outside cavity so there is no gradient
What is the pressure during inspiration/inhalation?
Increased volume of thorax, therefore decrease pressure so pressure outside is greater than pressure inside and air flows in
What is the pressure during expiration/exhalation?
Decreased volume of thorax, therefore increased pressure so pressure outside is less than pressure inside and air flows out
How does the sternum connect to ribs?
Via costal cartilage (hyaline)
How many synovial joints on each side of the sternum?
6
How many cartilaginous joints on each side of the sternum?
1
What is the joint between the costal cartilage and sternum?
Sternocostal
What type of joint is the sternocostal?
Synovial, except the first one is cartilaginous
What is the joint between the cartilage and ribs?
Chostochondral
What type of joint is the chostochondral?
Cartilaginous
What are the joints between cartilage of ribs which don’t connect directly to the sternum?
Interchondral
What type of joints are the interchondral?
Synovial
What are the posterior thoracic joints articulations between?
Thoracic vertebrae and ribs
What type of joints are the posterior thoracic joints?
Synovial
What is the joint between the rib and transverse process of vertebrae?
Costotransverse
What is the joint between the rib and body of the vertebrae?
Costovertebral
what do respiratory muscles do?
Move the rib cage to allow us to breathe
What are the primary inspiratory muscles?
Diaphragm (needed to survive) and intercostals (not needed to survive)
When are the accessory muscles active?
Only when needed
What is the diaphragm?
A sheet of skeletal muscle which separates the thorax from the abdomen
What is the shape of the diaphragm when relaxed?
Dome shaped
What is the shape of the diaphragm when contracted?
Flattened
What does contraction of the diaphragm do?
Expands the thoracic cavity and compresses abdominopelvic cavity
What travels through the diaphragm?
Inferior vena cava, esophagus and aorta
Where do intercostal muscles attach?
Diagonally between neighbouring ribs
Where do the external intercostals run?
from up and out to down and in so when they contract they lift the ribcage and expand the cavity
What are the external intercostals involved in?
Inspiration - quiet and forced
Where do the internal intercostals run?
From up and in to down and out so when they contract they depress the ribcage and decrease the cavity
What are the internal intercostals involved in?
Expiration - forced only
What are the accessory muscles?
Several muscles that attach to the thoracic cage
What are the functions of accessory muscles?
Some increase cavity volume for forced inspiration and some decreased cavity volume for forced expiration
How are the muscles of respiration during normal ‘quiet’ inspiration?
The diaphragm contracts and flattens and external intercostals contract and lift the ribs
How are the muscles of respiration during active ‘forced’ breathing?
The diaphragm contracts, flattens and external intercostals contract and lift the ribs and accessory muscles contract to further expand the thoracic cavity
What type of process is normal ‘quiet’ expiration?
Passive
How are the muscles of respiration during normal ‘quiet’ expiration?
The diaphragm relaxes and becomes dome shaped and the external intercostals relax so the ribs are no longer lifted
How are the muscles of respiration during active ‘forced’ expiration?
The diaphragm relaxes and becomes dome shaped, the external intercostals relax so the ribs are no longer lifted, internal intercostals contract and depress ribs and accessory muscles contract to further decrease cavity volume
What is lung tissue?
Elastic and always trying to recoil
What does the pleura do?
Make the lungs stick to the thoracic wall
What do lungs do during inspiration?
Expand
What do lungs do during expiration?
Decrease
Where is the visceral pleura?
On the lungs
Where is the parietal pleura?
On the thoracic wall
What is in between the visceral and parietal pleura?
Pleural fluid
What does the pleural fluid do?
Make a slippery surface for frictionless movement against other structures and fluid bond causes lungs to stick to thoracic wall
What does thoracic wall movement result in?
Lung movement
What happens when there is an increased volume of the thorax?
Increased volume of the lungs, decreased pressure in the lungs and so air flows in
What happens when there is a decreased volume of the thorax?
Decreased volume of the lungs, increased pressure in the lungs and so air flows out
What level is the diaphragm found at?
The 12th rib
