The Sternum Anatomy

Question 1

What are the functions of the rib cage ?

Answer 1

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

Question 2

What is a true rib ? How many do we have ?

Answer 2

Cartilage is attached to sternum/ articulate directly with sternum
7 on each side (14)

Question 3

What is a false rib ? How many do we have ?

Answer 3

It’s not directly attached to sternum/ articulate with the cartilage of the rib above
3 on each side (6)

Question 4

What is a floating rib ? How many do we have ?

Answer 4

Not attached to sternum nor cartilage

2 on each side (4)

Question 5

Name the layers of intercostal muscles

Answer 5

• innermost intercostal
• internal intercostal
• external intercostal

Question 6

Which articulation guarantees that the rib move up during ventilation ?

Answer 6

• the costovertbral joint

- the costotransverse joint

Question 7

What are the movements made by the sternum and shaft of the ribs during ventilation ?

Answer 7

Sternum moves like a pump handle while shafts of the ribs move lie a bucket handle

Question 8

Regarding the thorax anatomy, which characteristic is shared by all mammals

Answer 8

The presence of a diaphragm

Question 9

What are the origins and insertions of the diaphragm ?

Answer 9

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

Question 10

Describe the motion of diaphragm during inspiration ?

Answer 10

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

Question 11

Describe the activity of lungs during ventilation

Answer 11

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

Question 12

Describe the phases of the ventilator cycle ? What happens during the “pause”

Answer 12

Inspiration
Pause
Expiration
Pause

During the pause the diaphragm is not moving, the pressure variation is equal to 0

Question 13

Describe the communication system between upper and lower abdominal cavities

Answer 13

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

Question 14

Which nerves control the movements of the diaphragm ?

Answer 14

The phrenic nerves arising from C3 to C5

Question 15

Do diaphragmatic nerves exist ?

Answer 15

No, they don’t. The phrenic nerves are the ones controlling the diaphragm.

Question 16

List the accessory muscles for inhalation

Answer 16

• scalene
• sternocleiomastoid
• upper trapezius
• pectoralis major and minor
• inferior fibers of serratus anterior and latissimus dorsi
• outer intercostal muscles

Question 17

What is the fraction of 02 in the room air?

Answer 17

21 %

Question 18

What are the accessory muscles of expiration ?

Answer 18

• transverse abdominis
• internal oblique
• external oblique
• rectus abdominis
• inner intercostal muscles

Question 19

Which muscles are involved in quiet expiration ?

Answer 19

None it’s a passive process resulting from the recoil of lungs, rib cage and diaphragm

Question 20

What are the 2 layers forming the pleura ?

Answer 20

• parietal pleura which contacts the rib cage

- visceral pleur which contacts the lungs

Question 21

How much parietal liquid is there in the visceral pleura ?

Answer 21

8 to 10mL

Question 22

Is there a junction between the left and right side of the visceral pleura ?

Answer 22

No

Question 23

What are the functions of the pleura

Answer 23

• reducing friction between structures implied in the ventilation
• responsible for the movement of the lungs

Question 24

What is the blood supply of the pleura ?

Answer 24

• visceral part : bronchial circulation

- parietal part : intercostal arteries

Question 25

What is the nerve supply of the pleura ?

Answer 25

• parietal pleura : intercostal and phrenic nerves

- visceral pleura : intercostal nerve with no sensory innervation

Question 26

What is the pressure in the pleura compared to the pressure at the see level ?

Answer 26

See level : 760 mmHg
In the pleural cavity : 757 mmHg
It is lower in the pleural cavity

Question 27

Which type of force does the rib cage exert ?

Answer 27

Eccentric forces

Question 28

Which type of force does the lung tissue exert ?

Answer 28

Concentric forces

Question 29

In the pleural cavity is the pressure positive or negative ?

Answer 29

Negative

Question 30

Which structure lies between the left and right lungs ?

Answer 30

The mediastinum

Question 31

Where is located the mediastinum ?

Answer 31

Superior boundaries
Between sternal angle and lower border of T4

Inferior boundaries
Middle of xiphoïde process to T9

Question 32

Give two structures located in the superior mediastinum

Answer 32

• aortic arch

- trachea

Question 33

What is the pericardium

Answer 33

Where pleura and mediastinum overlap