Anterior Thoracic Wall - Ach Flashcards
How many total ribs are in an anatomically normal human being?
12 x 2 = 24
How many true ribs are in an anatomically correct human?
True Ribs: 1-7
7 x 2 = 14
How many false ribs are in an anatomically correct human?
False Ribs: 8-12
5 x 2 = 10
How many floating ribs are in an anatomically correct human?
Floating Ribs: 11-12
2 x 2 = 4
How many vertebrae are in the bony thorax?
T1-T12 = 12
Which vertebral facet articulates with the tubercle of a rib?
Transverse process
Which vertebral facets articulate with the head of a rib?
Vertebral Body:
Inferior Costal Facet of vertebra above
+
Superior Costal Facet of corresponding vertebra
(ex. Rib 7 attaches to ICF of 6 and SCF of 7)
What are the three layers of muscles that form the thoracic wall?
- External Intercostal Muscles
- Internal Intercostal Muscles
- Innermost Intercostal Muscles
What is the weakest part of the rib?
Anterior to its angle
Which direction do the External Intercostal Muscles run?
Fibers run downward and forward
(“hands in pocket”)
What direction do the External Intercostal Muscles move the thoracic wall?
Elevation
(forced inspiration)
What direction do the Internal Intercostal Muscles run?
Fibers run at right angles to the external intercostals
(“cross arms on shoulders”)
What direction do the Internal Intercostal Muscles move the thoracic wall?
Depress ribs
(forced expiration)
Where are the External Intercostal muscles replaced by a membrane?
Anteriorly
(along costal cartilage)
Where are the Internal Intercostal Muscles replaced by membrane?
Posteriorly
Where are the Innermost Intercostal Muscles located?
Part of internal layer.
Mainly along the lateral aspect of the throacic wall.
What direction do the Innermost Intercostal Muscles run?
Same direction as Internal Intercostal Muscles.
(“cross arms on shoulders”)
Where are the Innermost Intercostal Muscles replaced by membranes?
Anteriorly & Posteriorly
What is the function of the Intercostal Muscle layers?
- Keep intercostal spaces rigid
- Elevate or depress the ribs
Where is the Thoracic Inlet?
Boundary between neck and thorax.
AKA: Superior Thoracic Aperture
(manubrium + 1st ribs + body of T1 vertebra)
Where is the Thoracic Outlet?
Boundary between thorax and abdomen.
AKA: InferiorThoracic Aperture
Origin of respiratory diaphragm.
(costal margins of 12th ribs + costal cartilages of ribs 7-11)
What are the three directions the chest can expand in? What causes each?
- Vertical diameter
- contraction of diaphragm
- Transverse diameter
- ribs elevated and swing outward (“bucket handle”)
- Anteroposterior diameter
- sternum movement (“pump handle”)
Where are the Neurovascular components of the intercostal spaces located?
- Between the Inner and Innermost Intercostal Muscles
- Lie in the Subcostal groove under the lower border of the upper rib
What are the Posterior Intercostal Arteries branches of?
Aorta
