lecture 16 - thorax anatomy & breathing Flashcards
What are the 3 key compartments of the thoracic cavity?
The mediastinum and 2 pleural cavities
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 mediastinum?
A region lying between the lungs in the thoracic cavity that contains the oesophagus, trachea and heart
What does the mediastinum contain?
Heart, vessels, pericardium, trachea, oesophagus
What do the pleural cavities contain?
Each has a lung
Why are the 2 pleural cavities seperate?
So that if one lung stops the functioning, the other can act separately
What is the pleural cavity lined with?
The parietal (against cavity) and visceral (against lungs) pleura
What fundamentally drives ventilation?
Pressure changes in the thoracic cavity
What is the relationship between pressure and volume in the thoracic cavity?
Pressure is inversely proportional to volume (P=1/V)
What happens to the volume in the thorax during inspiration?
It increases (as pressure decreases)
What happens to the volume in the thorax during expiration?
It decreases (as pressure increases)
What happens to the pressure in the thorax during inspiration?
It decreases (as volume increases)
What happens to the pressure in the thorax during expiration?
It increases (as volume decreases)
Why does a smaller volume create higher pressure?
A smaller space for the same amount of gas leads to more collisions and therefore increased pressure
What is Boyle’s Law?
P=1/V - pressure is inversely proportional to volume
How does air move between areas of varying pressure?
Moves from high to low pressure
What is the relative pressure inside and outside the thoracic cavity during inspiration?
Pressure inside < Pressure outside
What is the relative pressure inside and outside the thoracic cavity during expiration?
Pressure outside < Pressure inside
What is the relative pressure inside and outside the thoracic cavity between breaths?
Pressure outside = Pressure inside
What joins the sternum to the ribs?
Costal cartilage
What type of cartilage is costal cartilage?
Hyaline
What joints connect the costal cartilage of the ribs to the sternum?
Sternocostal joints
What type of joint in the sternocostal joint?
Synovial, except the 1st, which is cartilaginous
What do the sternocostal joints connect?
The ribs and sternum
What joints connect the ribs to the costal cartilage?
Costochondral joints
What type of joint are costochondral joints?
Cartilaginous joints
What do costochondral joints connect?
Ribs and costal cartialge
What joints connect costal cartilage in the lower ribs?
Interchondral joints
What type of joint are interchondral joints?
Synovial joints
What is the name for the joints between costal cartilage in the lower ribs?
Interchondral joints
What are the posterior thoracic joints?
Joints that articulate the thoracic vertebrae and ribs
What are the 2 types of posterior thoracic joints?
Costotransvere and costovertebral joints
What do costotransverse joints connect?
The rib and the transverse process of vertebrae
What do costovertebral joints connect?
The rib and the body of vertebrae
What are the primary respiratory muscles?
Diaphragm & intercostal muscles
What is the structure of the diaphragm?
It is a sheet of skeletal muscle
What does the diaphragm seperate?
The thorax and the abdomen
How does the volume of the thoracic cavity change when the diaphragm contracts?
cavity expands - increased volume
How does the volume of the thoracic cavity change when the diaphragm relaxes?
Cavity shrinks - decreased volume
What is the shape of the diaphragm when contracted?
Flattened
What is the shape of the diaphragm when relaxed?
Dome shaped
What does contraction of the diaphragm do to the abdominopelvic cavity?
compresses it
How do the intercostal muscles attach to the ribs?
Attach diagonally between neighbouring ribs
What movement do the external intercostal muscles create?
They lift the rib cage and expand cavity
What movement do the internal intercostal muscles create?
Depress rib cage and decrease cavity volume
Which intercostal muscles expand the thoracic cavity?
External intercostals
Which intercostal muscles decrease the volume of the thoracic cavity?
Internal intercostal muscles
What is the collective function of the accessory muscles of the thoracic cavity?
To increase or decrease cavity volume for forced inspiration or expiration
What muscles are involved in normal, quiet inspiration?
Diaphragm contracts, external intercostals contract
What muscles are involved in normal, quiet expiration?
Diaphragm relaxes, external intercostals relax
What additional muscles are involved in active/forced inspiration?
Accessory muscles
What additional muscles are involved in active/forced expiration?
Accessory muscles, internal intercostals
What is the function of the pleura?
Lines the pleural cavity and makes the lungs stick to the thoracic wall as they expand during inspiration and decrease during expiration
What part of the pleura is in contact with the lungs?
Visceral pleura
What part of the pleura is in contact with the thoracic wall?
The parietal pleura
Where does pleural fluid sit?
between the parietal and visceral pleura
What is the function of pleural fluid?
Provides a slipper surface for frictionless movement against other structures. Fluid bond causes lungs to stick to the thoracic wall
