Muscles

Question 1

Pectoralis Major

Answer 1

Innervation: Medial and Lateral pectoral nerves
Origin: Clavicular head – anterior surface of medial clavicle, Sternocostal head – anterior surface of sternum, costal cartilages of ribs 1-6, external oblique aponeurosis
Insertion: Lateral lip of intertubercular sulcus of humerus
Actions:
1) Flexes, adducts and medially rotates the upper arm
2) Clavicular head – flexes the extended limb
3) Sternocostal head – extends the flexed limb

Question 2

Pectoralis Minor

Answer 2

Innervation: Medial pectoral nerve
Origin: Costal cartilages of ribs 3-5
Insertion: Coracoid process of scapula 
Actions:
1) Depression and protraction of scapula
2) Pulls the shoulder inferiorly

Question 3

Subclavius

Answer 3

Innervation: Nerve to subclavius
Origin: Costochondral junction of 1st rib
Insertion: Inferior surface of middle third of clavicle
Actions:
1) Depresses and anchors the clavicle
2) Protect underlying subclavian vessels and brachial plexus from a fractured clavicle

Question 4

Serratus Anterior

Answer 4

Innervation: Long thoracic Nerve
Origin: Lateral surface of ribs 1-8
Insertion: Costal surface of medial border of scapula 
Actions:
1) Protracts of scapula
2) Abduction of upper limb
3) Holds scapula against ribcage

Question 5

Quadratum Lumborum Muscle

Answer 5

Innervation: Anterior rami of L1-L4
Origin: Iliolumbar fascia, iliac crest
Insertion: Transverse processes of L1-L4, inferior border of 12th rib
Actions:
1) Lateral flexion and extension of vertebral column
2) Fixes the 12th rib during inspiration

Question 6

Psoas Major muscle

Answer 6

Innervation: Anterior rami of L1-L3
Origin: Transverse processes of T12-L4, Vertebral bodies and intervertebral disks of L1-L5
Insertion: Lesser trochanter of femur (as iliopsoas)
Actions:
1) Flexion of thigh at hip joint
2) Lateral flexion of vertebral column

Question 7

Psoas Minor Muscle (only present in 50% of population)

Answer 7

Innervation: Anterior rami of L1
Origin: Vertebral bodies and intervertebral disks of T12-L1
Insertion: Pubic bone (pectineal line)
Actions:
1) Flexion of vertebral column

Question 8

Iliacus

Answer 8

Innervation: Femoral nerve (L2-L4)
Origin: Iliac fossa and AIIS
Insertion: Lesser trochanter of femur (as iliopsoas)
Actions:
1) Flexion of thigh at hip joint
2) Lateral rotation of thigh at hip joint

Question 9

External oblique muscle

Answer 9

Innervation: Thoracoabdominal nerves (T7-T11), Subcostal nerve (T12)
Origin: External surfaces of ribs 5-12
Insertion: Iliac crest (anterior half), pubic tubercle, linea alba
Actions:
1) Compresses and support abdominal viscera
2) Contralateral (opposite) rotation of trunk

Question 10

Internal oblique muscle

Answer 10

Innervation: Thoracoabdominal nerves (T7-T11), Subcostal nerve (T12), Iliohypogastric (L1), Ilioinguinal nerve (L1)
Origin: Iliac crest (anterior 2/3rds), Thoracolumbar fascia, connective tissue deep to the inguinal ligament
Insertion: Pubis via conjoint tendon, linea alba, inferior border of 12th rib
Actions:
1) Compresses and support abdominal viscera
2) Flexion and unilateral rotation of trunk

Question 11

Transversus Abdominis

Answer 11

Innervation: Thoracoabdominal nerves (T7-T11), Subcostal nerve (T12), Iliohypogastric (L1), Ilioinguinal nerve (L1)
Origin: Thoracolumbar fascia, connective tissue lateral to 1/3 of inguinal ligament, Costal Cartilages of ribs 7-12, iliac crest
Insertion: Pectin pubis via conjoint tendon, pubic crest, linea alba
Actions:
1) Compresses and support abdominal viscera
2) Antagonistic to diaphragm

Question 12

Rectus Abdominis

Answer 12

Innervation: Thoracoabdominal nerves (T7-T11), Subcostal nerve (T12)
Origin: Pubic crest, Pubic symphysis
Insertion: Xiphoid (sternum), Costal cartilages of ribs 5-7
Actions:
1) Compresses and support abdominal viscera
2) Flexion of trunk
3) Controls pelvis tilt whilst walking
4) Depression of ribs

Question 13

Pyramidalis (20% absent in population)

Answer 13

Innervation: Subcostal nerve (T12)
Origin: Pubic crest, Pubic symphysis
Insertion: Linea alba
Actions:
1) Tenses the linea alba

Question 14

External intercostal muscle

Answer 14

Innervation: Intercostal nerves (T1-T11)
Origin: Inferior border of rib
Insertion: Superior border of rib below
Actions:
1) Elevates sternum and ribs
2) Increase anteroposterior dimension of thoracic cavity during inspiration

continues anteriorly as anterior intercostal muscle

Question 15

Internal Intercostal muscle

Answer 15

Innervation: Intercostal nerves (T1-T11)
Origin: Costal groove of rib
Insertion: Superior border of rib below
Actions:
1) Interchondral portion – increases anteroposterior dimension of thoracic cavity during inspiration (via elevation and outward movement of ribs and sternum)
2) Interosseous portion – depression of ribs and sternum during forced expiration

continues posteriorly as posterior intercostal muscle

Question 16

Innermost intercostal muscle

Answer 16

Innervation: Intercostal nerves (T1-T11)
Origin: Costal groove of rub
Insertion: Superior border of rib below
Actions:
1) Depression of ribs and sternum during expiration

continues anteriorly as transversus thoracis (extends from xiphoid (sternum) to costal cartilages of ribs 2-6)
continues posteriorly as subcostalis muscle (extends from internal surfaces of one rib to the next)