Muscles

Question 1

Intercostal (external)

Answer 1

attachments - from rib to rib oriented from superior-lateral to inferior-medial

actions - elevation of ribs

innervation - intercostal nerve

Question 2

Intercostal (internal & innermost)

Answer 2

attachments - from rib to rib oriented superior-medial to inferior-lateral

actions - depression of ribs

innervation - intercostal nerve

Question 3

transversus thoracis

Answer 3

attachments - from posterior sternum to costal cartilages

actions - depress ribs

innervation - intercostal nerves

Question 4

cremaster

Answer 4

attachments - from the medial edge of the internal oblique to spermatic cord

actions - elevation of testis

innervation - genitofemoral nerve

Question 5

diaphragm

Answer 5

attachments - from xiphoid process, inner surface of the lower ribs & costal cartilages, medial & lateral arcuate ligaments & lumbar vertebrae via the crura to the central tendon

actions - inspiration (negative thoracic pressure by inferior displacement)

innervation - phrenic nerve

Question 6

external oblique

Answer 6

attachments - from lower 8 ribs to iliac crest & rectus sheath

actions - flexion & rotation of the trunk, & compression of the abdominal cavity

innervation - ventral rami T7-12

Question 7

internal oblique

Answer 7

attachments - from thoracolumbar fascia to inguinal ligament, iliac crest & rectus sheath

actions - flexion & rotation of the trunk, &
compression of the abdominal cavity

innervation - lower thoracic & L1 ventral rami

Question 8

quadratus lumborum

Answer 8

attachments - from 12th rib to iliolumbar ligament & iliac crest

actions - extension & lateral flexion of the trunk, and fixes 12th rib during respiration

innervation - ventral rami T12-L3

Question 9

rectus abdominis

Answer 9

attachments - from xiphoid process & adjacent costal cartilages to pubic crest & tubercle

actions - flexion of trunk & compression of abdominal cavity

innervation - lower thoracic ventral rami

Question 10

transversus abdominis

Answer 10

attachments - from lower six costal cartilages & thoracolumbar fascia to inguinal ligament, iliac crest & rectus sheath

actions - compression of the abdominal cavity

innervation - lower thoracic & L1 ventral rami

Question 11

coccygeus

Answer 11

attachments - from ischial spine & sacrospinous ligament to coccyx

actions - supports & compresses posterior pelvic floor

innervation - ventral rami S4-5

Question 12

levator ani

Answer 12

attachments - from pubic symphysis, obturator fascia & ischial spine to midline raphe & anococcygeal ligament

actions - supports pelvic viscera, & compresses rectum & vagina

innervation - pudendal nerve (inferior rectal branches) & S4

Question 13

bulbospongiousus

Answer 13

attachments - in male from median raphe & perineal body (central tendon) to surround bulb of penis; in female from the perineal body to surround vestibular bulb, vaginal orifice & clitoris

actions - in male empties urethra, maintains erection & contracts during ejaculation; in female constricts vaginal orifice & contributes to erection of clitoris

innervation - perineal branch of pudendal nerve

Question 14

ischiocavernosus

Answer 14

attachments - from ischial tuberosity & ramus to aponeurosis surrounding crus of penis or clitoris

actions - compresses crus during erection

innervation - perineal branch of pudendal nerve

Question 15

sphincter ani externus

Answer 15

attachments - from perineal body (central tendon) to anococcygeal raphe

actions - closes anal canal & fixes perineal body

innervation - inferior rectal branch of pudendal nerve

Question 16

sphincter urethrae

Answer 16

attachments - surrounds urethra

actions - compresses urethra

innervation - perineal branch of pudendal nerve

Question 17

compressor urethrae

Answer 17

attachments - in the female from the ischiopubic ramus to midline passing ventral to the urethra and inferior to the sphinchter urethrae with a variable number of fibers fanning out medially to reach the vagina (thus replacing the deep transverse perineus)

actions - compresses urethra

innervation - perineal branch of the pudendal nerve

Question 18

Sphincter urethrovaginalis

Answer 18

attachments - from perineal body, surrounds vagina & urethra to meet contralateral muscle inferior to compressor urethrea

actions - compresses urethra & vagina

innervation - perineal branch of the pudendal nerve

Question 19

Deep transverse perineus

Answer 19

attachments - from ischial tuberosity to perineal body (central tendon)

actions - fixes perineal body

innervation - perineal branch of pudendal nerve

Question 20

superficial transverse perineus

Answer 20

attachments - from ischial tuberosity to perineal body (central tendon)

actions - fixes perineal body

innervation - perineal branch of the pudendal nerve

Question 21

iliacus

Answer 21

attachments - from iliac fossa, iliac crest & sacrum to the lesser trochanter of the femur

actions - flexes thigh and stabilizes hip joint

innervation - femoral nerve & lumbar plexus branches

Question 22

psoas

Answer 22

attachments - from anterior lumbar transverse processes vertebral bodies & discs to the lesser trochanter of the femur

actions - flexes thigh and stabilizes hip joint

innervation - ventral rami L1-3

Question 23

piriformis

Answer 23

attachments - from the anterolateral sacrum & posterior inferior iliac spine to the upper border of the greater trochanter

actions - abducts & laterally rotates thigh

innervation - branches of the lumbosacral plexus

Question 24

obturator internus

Answer 24

attachments - from the anterolateral wall of the pelvis & obturator membrane to the medial surface of the greater trochanter

actions - laterally rotates thigh

innervation - nerve to the obturator internus