Lecture 3 - Mechanics of respiration Flashcards
What membranes are the lungs covered by?
The visceral pleura (then beyond that is the parietal pleura)
Describe the development of the pleura
During fetal developing the lung grows and pushes into a sac-like structure called the pleural cavity, and takes a covering of part of this sac around itself (Visceral pleura) and the remaining part of the sace forms the parietal pleura
The lung surface is covered by a thin, serous membrane called the _____ ____, there is an outer membrane called the _______ ______
Visceral pleura
Parietal pleura
The parietal pleura lines and is attached to:
- the thoracic wall (costal pleura)
- the mediatstinum (mediastinal pleura)
- the diaphragm (diaphragmatic pleura)
- the capula (cervical pleura)
it moves with the thoracic wall, mediastiunum and diaphragm during respiration
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Describe the structure of the pleural cavity and how it’s formed by the visceral and parietal pleura
And how do the pleura membranes stay moistened, and what does this facilitate?
The visceral and parietal pleura are continuous with one another at the root of the lung.
The potential space between the visceral and parietal pleura is the pleural cavity.
the surfaces of the pleura are moistened by small amounts of fluid secreted by these membranes. The secreted fluid also reduces friction and facilitates inflation/deflation of lungs.
What is the inferior distance between the visceral and parietal pleura?
2 ribs difference
Anteriorly, what does the level of the 8th rib correspond to?
The lowest level of the parietal pleura
Anteriorly, what does the level of the 6th rib correspond to?
The inferior border for visceral pleura
In the mid axillary line, what level does the 8th rib correspond to?
Inferior border of visceral pleura
In the mid axillary line what does the level of the 10 rib correspond to ?
Inferior border of parietal pleura
Posteriorly, using the scapula line, what does the level of the 10 rib correspond to ?
inferior border of visceral pleura
Posteriorly in the scapula line what does the level of the 12 rib correspond to?
Inferior border of parietal pleura
What are the 2 pleural recesses?
And what do they allow for?
Costomediastinal recess: The part of the pleural cavity in the angle of reflection of costal pleura and mediastinal pleura at the anterior border of the pleura.
Costodiaphragmatic recess: the part of the pleural cavity in the angle of relfection of costal pleura and diaphragmatic pleura at the inferior border of the pleura
The lung expands into these recesses during forced inspiration.
Where does pus accumulate in the lungs?
In the cosodiaphragmatic recess - since pus and excess fluid an accumulate at the lowest level due to gravity - so any excess fluid will accumulate in the costodiaphragmatic recess
Should the areas labelled be black and clear?
Yes, if they aren’t clear then there may be an infection or excess fluid present
Where do you insert a needle to remove excess fluid/pus?
Between ribs 8 and 10 in the midaxillary line
Describe how pain is felt by the pleura, and which pleura is most sensitive?
Visceral pleura is insensitive to pain, as it recieves no nerves of general sensation.
Parietal pleura is extremely sensitive to pain as it is innervated by the nerves innervating the thoracic wall. (Intercostal nerves innervates the costal pleura and phrenic nerve innervates the rest of parietal pleura).
What bones make up the thoracic skeleton?
Sternum
Ribs and costal cartilages
Thoracic vertebrae
What are the 3 parts of the sternum?
Upper part = manubrium
Middle = body
Lower part = xiphoid process
Descibe the different groups of ribs, and what they articulate with anteriorly
- Ribs 1-7 are called true ribs - they articulate directy with the sternum
- Ribs 8, 9 and 10 are called false ribs - each articulate with the costal cartilage of the rib immediately above they form the costal margin
- Ribs 11 and 12 (free or floating ribs) do not reach the sternum
Describe the morphology of the typical rib
Is made up of: head, neck, tubercle, body (Shaft)
Describe the posterior joints between the rib and it’s respctive vertebrae
The head articulates with the body of its vertebra and that of the vertebra above - these are costovertebral joints = synovial
The tubercle articulates with the transverse process of its own vertebra - these are costotransverse joints = synovial
Describe how teh rib is joined to the sternum?
The unossified part of the rib (i,e costal cartilage) articulates with the sternum, ths is the Sternocostal (condrosternal) joint. Which is a synovial joint.
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What are the 3 diametes of the thoracic cavity?
- Anteroposterior
- transverse
- vertical
Elevation of the ribs by inspiration muscles causes an in increase in which diameters?
Increase in anteroposterior diameter
Increase in transverse diameter
Contraction of the diaphragm causes what?
An increase in vertical diameter
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Describe the “pump-handle” movements at the ribs
In the pump-handle movements the sternum and ribs act as a single structure.
The sternum is elevated and carried forwards and the ribs are also lifted and anteroposterior diameter of thorax is increased however, owing to shape of ribs, they also spread out laterally.
In the pump-handle movement “rotation” takes place about an axis passing through the costovertebral/ costotransverse joints (approximates to rotation about an axis through the head and tubercle of the rib).
Do the upper or lower ribs undergo the “pump-handle movement” more than one another or are they equal in their pump handle movement?
The upper ribs undergo “pump-handle” movement more than lower ribs because the articular surfaces of (transverse process/ tubercle) costatransverse joint are curved in the upper ribs and therefore allows more rotation in this joint
Describe the “bucket-handle” movement
And what muscle is largely responsible for this movement?
In ths movement, rotation occurs about an axis through costovertebral and stternocostal joints (approximates to rotation about an axis through the anterior and posterior ends of ribs)
there is no rotation in the costotransverse joints but a gliding movment occurs instead. This is due to the flat articular surface in this joint at lower vertebral levels. As a consequence, the bucket handle movement occurs mostly at lower ribs.
The lower ribs spread laterally and transverse diameter of the thorax increases.
Is produced mainly by the diaphragm
Compare and contrast the pump-handle and bucket-handle movements
- Contributing joints/movements
- Contributing vertebra
- Changing thoracic diameter
What are the two thoracic apertures (openings) ?
And what is each aperture bounded by
There is a superior and an inferior aperture of the thorax.
the superior thoracic aperture is bounded by:
- Anteriorly - upper border of manubrium
- Laterally - 1st rib
- Posteriorly - body of T1 vertebra
the inferior thoracic aperture is bounded by
- Anteriorly - xiphoid process of sternum
- Laterally - costal margin, 11th and 12th
- Posteriorly - T12 vertebrae
What are the contents of the thoracic apertures?
Superior thoracic apertures
- Provides a way for structures to run between the thorax and the neck (trachea, esophagus, brachiocephalic artery, left subclavian artery and vein, vagus and phrenic nerve)
Inferior thoracic aperture
- Provides a way for structures to run between the thorax and the abdomen (Aorta, esophagus, inferior vena cava - IVC) It is closed by a musculotendinous sheet, the DIAPHRAGM
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Whats the difference for the thoracic inlet for anatomists and clinicians ?
What happens in thoracic outlet syndrome
Scalene muscles compress the subclavian artery, and maybe some nerves
Describe how the diaphragm is divided up into parts, and the position of each part
Each half of the muscular part of the diaphragm is divided into 3 parts which are inserted into the central tendon.
3 parts
- Sternal: Narrow slips arise from the back of the xiphoid process
- Costal: Arises from the inner surfaces of the lower six costal cartilage and lower four ribs; forms the R or L dome of diaphragm
- Lumbar: The part of the diaphragm arising from the lumbar vertebrae forms two muscular crura that ascend to the central tendon. Right crus arises from upper three or four vertebrae, left crus from the upper two or three vertebrae.
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What are the three large structures that pass through the diaphragm, and what vertebra level does each one correspond to?
Contraction of the diaphragm increases the _____ diameter
Vertical
What is the function of the muscles of inspiration?
They cause an increase in the diameters of the thoracic cavity (=expanded)
- They cause an increase in volume of the thoracic cavity
- Intrathroracic pressure is decreased
- air is sucked in and the lungs become inflated
Describe the functions of the muscles of expiration
The muscles of expiration cause a decrease in the diameteres of the thoracic cavity (=contracted)
- They cause a decrease in volume of the thoracic cavity
- Intrathoracic pressure is increased
- air is forced out of the lungs which become delflated
Are primary or secondary muscles used in quite breathing?
Secondary muscles are active in forced expiration
What are the 3 planes that the intercostal muscles are arranged into?
- Superficial layer: exteranl intercostal muscles
- Intermediate layer: Internal intercostal muscles
- Deep layer:
- innermost intercostal muscles
- Subcostalis muscle
- Tranversus thoracis muscle
in an intercostal space, the muscle fibres are attached to the rib above and the rib below
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And describe the shape and structure of the external and internal intercostal muscles
The external intercostal M. becomes thinner at the anterior aspect to become a membrane.
The internal intercostal M does the same, but it thins and forms a membrane posteriorly.
The innermost layer is divided into three layers, subcostalis M., innermost intercostal M., and transversus thoracic M.
What are the actions of the intercostal musles?
And how can the muscles be distinguished from eachother?
Muscles can be distinguished by the direction of their fibres
- External intercostal muscles = downwards and forwards
- Internal intercostal muscls = upwards and forwards
- Innermost intercostal muscles = upwards and forwards
Their actions are consistent with the directions of their fibres
- External intercostal M acts to elevate the ribs (inspiraton)
- Internal intercostal M acts to depress the ribs (expiration)
- innmermost intercostal M acts to depress the ribs (expiration)
External intercostal muscles direction can be remembered as……
Hands in pocked,
whilst internal intercostal muscles is hand up and out in front (climbing)
Which muscles are the depressors and which are the elevators ?
Summer or muscles of respiration
how do people with COPD allow for more inspiration?
They need to use forced inspiration, and they achieve this by using their scalene muscles to lift the upper ribs as high as they in order to increase their lung capacity
Besides for scalene, what are two other muscles used in COPD to allow for forced inspiration, and forced inspiration in general?
Also use rhomboid and pectoralis minor muscles to shift the scapula meidally and to lift the upper ribs respsectively and increase their lung capacity
More 2ndary muscles: what are some more secondary muscles they can use (which are a bit lower) for forced inspiration?
Can also use their psoas major & quadratus lumborum muscles to stablilze and pull the floating ribs downwards during forced inspiration and icnrease their lung capacity.
2ndary muscles: how do the abdominal muscles assist in forced expiration?
Abdominal muscles like rectus abdominis is used to increase intraabdominal pressure and push the diaphragm up in forced expiration.
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