Rib Cage Wall Muscles

Question 1

Sternocleidomastoid

Answer 1

Origin: Sternum and Clavicle
Insertion: Skull behind ear
Function: Elevates sternum and clavicle and ribs

Question 2

Scalenus Anterior

Answer 2

Origin: C3-C6
Insertion: inner border of top of first rib
Function: Elevates first rib

Question 3

Scalenus Medius

Answer 3

Origin: C2-C7
Insertion: First Rib
Function: Elevates first rib

Question 4

Scalenus posterior

Answer 4

Origin: C5-C7
Insertion: Outer surface of the second rib
Function: Elevates second rib

Question 5

Pectoralis Major

Answer 5

Origin: front surface of upper costal cartilages, sternum, and inner half of clavicle
Insertion: Humerus
Function: Elevates the sternum and ribs

Question 6

Pectoralis minor

Answer 6

Origin: Second through fifth ribs near their cartilages
Insertion: front surface of the scapula
Function: Elevates the second through fifth ribs

Question 7

Subclavius

Answer 7

Origin: Undersurface of the clavicle
Insertion: On the first rib near its cartilage
Function: Elevates the first rib

Question 8

Serratus Anterior

Answer 8

Origin: Outer surfaces of the upper eight or nine ribs
Insertion: front of the scapula
Function: Elevates the upper ribs

Question 9

External Intercostals

Answer 9

Origin: Form a sheet of muscle from the first rib, cervical vertebrae, and the base of the skull
Insertion: Each rib to the adjacent rib
Function: Elevates the ribs and stiffens their interspaces
-Eleven connected muscles
-Fill outer portions of the rib interspaces

Question 10

Internal Intercostals

Answer 10

Origin: Eleven connected muscles fill the inner portions of the rib interspaces
–Except at back of the rib cage
Function: Primarily depress ribs and stiffen their interspaces
–Intercartilaginous internal intercostal muscles elevate the ribs

Question 11

Transversus Thoracis

Answer 11

Origin: Inner surface of the lower sternum and fourth or fifth costal cartilages
Insertion: Second through sixth ribs
Function: Depresses the second through sixth ribs

Question 12

Latissimus dorsi

Answer 12

Origin: The thoracic (lower six), lumbar, and sacral vertebrae and back surfaces of lower three to four ribs
Insertion: Humerus
Function: Whole muscles depress rib cage wall; fibers that insert into lower ribs can elevate them

Question 13

Serratus posterior inferior

Answer 13

Origin: Lower thoracic and upper lumbar vertebrae
Insertion: Lower border of lower four ribs
Function: Depresses lower four ribs

Question 14

Lateral iliocostalis cervicis

Answer 14

Origin: Surfaces of third through sixth ribs
Insertion: Fourth through sixth cervical vertebrae
Function: Elevates third through sixth ribs

Question 15

Lateral iliocostalis lumborum

Answer 15

Origin: Lumbodorsal fascia, lumbar vertebrae, and back surface of coxal bone
Insertion: Lower edges of lower six ribs
Function: Depresses the lower six ribs

Question 16

Lateral iliocostalis thoracis

Answer 16

Origin: Upper edges of lower six ribs
Insertion: Lower edges of upper six ribs
Function: Stabilizes the back of the rib cage wall
–Moves in concert with the cervicis and/or lumborum parts of the muscle group

Question 17

Levatores Costarum

Answer 17

Origin: 12 small muscles; C7 through T11 vertebrae
Insertion: Back surface of the rib below the vertebra of origin
Function: Elevate the ribs

Question 18

Quadratus Lumborum

Answer 18

Origin: Top of the coxal bone
Insertion: First four lumbar vertebrae and lowest rib
Function: Depresses the lowest rib

Question 19

Subcostals

Answer 19

Origin: Near the lower portion of the vertebral column on inner surfaces of the ribs
Insertion: Inner surfaces of ribs above
Function: Depress the ribs

Question 20

Serratus posterior superior

Answer 20

Origin: Cervical (C7) and thoracic (T1-3 or 4) vertebrae
Insertion: Ribs 2-5
Function: Elevates ribs 2-5