1. Muscles of Respiration
Kingdom of Bahrain
Arabian Gulf University
College of Medicine and Medical Sciences
Muscles of Respiration
Slides originally prepared by: Dr. Kumar
Notes added by: Ali Alhashli

2. Functions What are the functions of the thoracic cage?
Protects organs and structures of the thorax.
Provides stable support of upper extremity and head.
Flexible and can change dimensions during ventilation.
What are the functions of thoracic vertebrae?
Protects organs and structure of the thorax.
Protects and houses spinal cord.
Support structures of the thorax and articulate with ribs.
Flexible.

3. BONES OF THE THORACIC WALL: STERNUM
Articulation with clavicle
Manubrium
Sternal angle (manubriosteral joint) → primary
Rib 2
Body of sternum
Xiphosternal joint → secondary
Xiphoid process
Intercostal space
Intervertebral discs
(Secondary joints)
vertebra
Costal cartilage

4. Sternum

5. INTERCOSTAL SPACES 1
1st intercostal space: the space between the first and the second ribs 2
We have 12 pairs of ribs
First seven ribs are true ribs.
Ribs 8-10 are false ribs (they don’t attach directly to the sternum.
Ribs 11 & 12 are floating ribs. 3 4
Transverse ridges 5 6
Interchondral joints (synovial) 11 7 8 12 9 10

6. Articulation with transverse process of the vertebra

7. INTERCOSTAL SPACE: CONTENTS
Skin
Intercostal “VAN”
in costal groove: Vein, Artery & nerve
Superfacial fascia
External intercostal muscles
Then endothoracic fascia separating the thoracic wall from the parietal pleura of the lung
Internal intercostal muscle
Deep internal intercostal muscle

8. EXTERNAL INTERCOSTAL MUSCLES
Muscles: they run anteroinferiorly and they aid in the process of inspiration
External intercostal
membrane

9. INTERCOSTAL MUSCLES EXTERNAL INTERCOSTAL MUSCLES
membrane
External intercostal muscles
They run downward and obliquely

11. INTERNAL INTERCOSTAL MUSCLE S
Internal intercostal muscles: they run opposite to External intercostal muscles (postero-inferiorly)

12. INNERMOST INTERCOSTAL MUSCLES
Innermost intercostal muscles: in the same direction of internal intercostal muscles (posterio-inferiorly) and they act with them to aid in the process of expiration

13. SUBCOSTALES & TRANSVERSUS THORACIS
INTERCOSTAL MUSCLES
SUBCOSTALES & TRANSVERSUS THORACIS
Originating from the inferior body of the sternum and xiphoid process to insert in the costal cartilages of ribs 3-6
Subcostales
Transversus Thoracis

15. RESPIRATORY DIAPHRAGM
Main muscle of inspiration (increasing the vertical volume).
Dome-shaped structure.
Peripheral muscular portion.
Centrally placed tendon of insertion.
Right and Left domes reach as high as the 5th rib (presence of liver and heart).
Right dome  slightly higher due to large size of the right lobe of liver.

16. Parts:
1- Sternal part: from xiphoid process
2-Costal part: from lower 6 ribs and their costal cartilages.
3-Vertebral part: from the bodies and discs of lumbar vertebra by means of vertical columns or crura and from the arcuate ligaments.

17. MUSCLES OF THE THORACIC WALL RESPIRATORY DIAPHRAGM
CENTRAL TENDON
RIGHT DOME
Slightly higher
LEFT DOME

18. RESPIRATORY DIAPHRAGM: Thoracic Surface
AORTIC
T.V. 12
Right dome
VENACAVAL
T.V. 8
Left dome
VOICE OF ARABIC
8, 10, 12
OESOPHAGEAL
T.V. 10
Central tendon

19. RESPIRATORY DIAPHRAGM
(FUNCTIONS)
Functions of the diaphragm:
Muscle of inspiration: Contraction pulls down the central tendon  increased vertical diameter of the thorax  decreased intrathoracic pressure  expansion of the lungs.
Muscle of abdominal straining: by taking a deep breath, closing the glottis, and fixing the diaphragm  assists the muscles of the anterior abdominal wall in raising intra-abdominal pressure to evacuate pelvic contents  urination, defecation and parturition
Weightlifting muscle: assists in supporting the vertebral column and postvertebral muscles in the lifting of heavy weights.
Thoracoabdominal pump: decreased intrathoracic pressure and increased intraabdominal pressure  compression of blood in the inferior vena cava forcing it upward into the heart and also the lymph in the abdominal lymph vessels forcing it upward into the thoracic duct.

20. Nerve supply of the diaphragm:
Motor: phrenic nerve (which is originating from C3, C4 and C5).
Sensory
Phrenic nerve  central portion including parietal pleura and parietal peritoneal covering it.
Lower 6 intercostal nerves  peripheral portion

21. RESPIRATORY DIAPHRAGM: NERVE SUPPLY PHRENIC NERVE (from C3, C4, C5)

22. PARALYSIS OF THE DIAPHRAGM
UNILATERAL PARALYSIS
may be due to trauma or surgical division 
involved half (dome) of diaphragm ascends on inspiration 

23. ACCESSORY MUSCLES OF RESPIRATION Sternocleidomastoid muscle
Posterior scalene
Middle scalene
Anterior scalene

24. ACCESSORY MUSCLES OF RESPIRATION
Pectoralis major
Serratus anterior

25. ACCESSORY MUSCLES OF RESPIRATION ANTERIOR ABDOMINAL WALL MUSCLES
Rectus abdominis
Internal oblique

26. Respiratory Movements
During inspiration, all 3 diameters increase:
1. Increase in antero-posterior diameter: pump-handle movement of ribs.
2. Increase in transverse diameter: lateral spreading of ribs + bucket-handle movement of ribs.
3. Increase in cranio-caudal diameter: diaphragm

27. THORACIC CAGE: BOUNDARIES Suprapleural membrane
SUPERIOR and INFERIOR
Suprapleural membrane
(Sibson’s fascia)
Diaphragm