The Sternum Anatomy Flashcards
What are the functions of the rib cage ?
Protection for heart, lungs and large blood vessels
Support shoulder girdle and upper limbs
Provides origin and insertion points for muscle
Resist the negative pressure from lungs on expiration
What is a true rib ? How many do we have ?
Cartilage is attached to sternum/ articulate directly with sternum
7 on each side (14)
What is a false rib ? How many do we have ?
It’s not directly attached to sternum/ articulate with the cartilage of the rib above
3 on each side (6)
What is a floating rib ? How many do we have ?
Not attached to sternum nor cartilage
2 on each side (4)
Name the layers of intercostal muscles
- innermost intercostal
- internal intercostal
- external intercostal
Which articulation guarantees that the rib move up during ventilation ?
- the costovertbral joint
- the costotransverse joint
What are the movements made by the sternum and shaft of the ribs during ventilation ?
Sternum moves like a pump handle while shafts of the ribs move lie a bucket handle
Regarding the thorax anatomy, which characteristic is shared by all mammals
The presence of a diaphragm
What are the origins and insertions of the diaphragm ?
Origins :
Lumbar - Medial part : bodies of vertebra L1-L3, second and third intervertebral discs, anterior longitudinal ligament - Lateral part : 3 tendinous arches
Costal : inner aspect of the last 7 ribs
Sternal : posterior aspect of the xiphoïde process
Insertions :
Central tendon of the diaphragm
Describe the motion of diaphragm during inspiration ?
Diaphragm can only move down
It is mostly involved in inspiration
—> downward movement while inhaling
—> upward movement while exhaling
When the diaphragm contracts it moves down to become flat and cause an inspiration which is active
When the diaphragm relaxes it comes back to original state (dome shaped) accompanying expiration which is passive
Describe the activity of lungs during ventilation
Inspiration :
Diaphragm contracts, moves down to flatten
—> increases the volume of lung
—> reduces the pressure in the lungs
—> atmospheric pressure > lungs’ pressure
—> air enters the lungs from higher pressure to lower pressure
—> pressure becomes more negative in the lungs and creates a vacuum
Expiration :
Diaphragm relaxes and comes back to its dome shape
—> decreases volume of the lungs
—> increases the pressure in the lungs
—> atmospheric pressure < lungs’ pressure
—> air flow out of the lungs from higher pressure to lower pressure
—> pressure in the lungs becomes less negative coming back to zero
Describe the phases of the ventilator cycle ? What happens during the “pause”
Inspiration
Pause
Expiration
Pause
During the pause the diaphragm is not moving, the pressure variation is equal to 0
Describe the communication system between upper and lower abdominal cavities
Through diaphragm :
- caval hiatus (T8) : inferior vena cava, terminal branches of right phrenic nerve
- esophageal hiatus (T10) : esophagus, right and left vagus nerves, esophageal branches of the left gastric artery/ vein
- aortic hiatus (T12) : aorta, thoracic duct
Which nerves control the movements of the diaphragm ?
The phrenic nerves arising from C3 to C5
Do diaphragmatic nerves exist ?
No, they don’t. The phrenic nerves are the ones controlling the diaphragm.
List the accessory muscles for inhalation
- scalene
- sternocleiomastoid
- upper trapezius
- pectoralis major and minor
- inferior fibers of serratus anterior and latissimus dorsi
- outer intercostal muscles
What is the fraction of 02 in the room air?
21 %
What are the accessory muscles of expiration ?
- transverse abdominis
- internal oblique
- external oblique
- rectus abdominis
- inner intercostal muscles
Which muscles are involved in quiet expiration ?
None it’s a passive process resulting from the recoil of lungs, rib cage and diaphragm
What are the 2 layers forming the pleura ?
- parietal pleura which contacts the rib cage
- visceral pleur which contacts the lungs
How much parietal liquid is there in the visceral pleura ?
8 to 10mL
Is there a junction between the left and right side of the visceral pleura ?
No
What are the functions of the pleura
- reducing friction between structures implied in the ventilation
- responsible for the movement of the lungs
What is the blood supply of the pleura ?
- visceral part : bronchial circulation
- parietal part : intercostal arteries
What is the nerve supply of the pleura ?
- parietal pleura : intercostal and phrenic nerves
- visceral pleura : intercostal nerve with no sensory innervation
What is the pressure in the pleura compared to the pressure at the see level ?
See level : 760 mmHg
In the pleural cavity : 757 mmHg
It is lower in the pleural cavity
Which type of force does the rib cage exert ?
Eccentric forces
Which type of force does the lung tissue exert ?
Concentric forces
In the pleural cavity is the pressure positive or negative ?
Negative
Which structure lies between the left and right lungs ?
The mediastinum
Where is located the mediastinum ?
Superior boundaries
Between sternal angle and lower border of T4
Inferior boundaries
Middle of xiphoïde process to T9
Give two structures located in the superior mediastinum
- aortic arch
- trachea
What is the pericardium
Where pleura and mediastinum overlap
