Ch 9 Muscles Part 2

Question 1

Deep Muscles of the Thorax: Breathing

Answer 1

External intercostals—more superficial muscles; elevate ribs for inspiration

Internal intercostals—deeper muscles; aid forced expiration

Diaphragm
Partition between thoracic and abdominal cavities
Most important muscle in inspiration
Innervated by phrenic nerves

serratus anterior:
Originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula.

Question 2

Muscles of the Abdominal Wall

Answer 2

Four paired muscles, their fasciae and aponeuroses form lateral and anterior abdominal wall:

Rectus abdominis
External obliques
Internal obliques
Transversus abdominis

Question 3

Muscles of the Pelvic Floor

Answer 3

Pelvic floor (pelvic diaphragm) composed of two paired muscles

Levator ani
Coccygeus
Both innervated by sacral nerves

Question 4

Muscles of the Perineum

Answer 4

Urogenital diaphragm:

• Anterior half of perineum, inferior to pelvic floor
• Deep transverse perineal muscle
• Contains external urethral sphincter (voluntary control of urination)

Question 5

Muscles of the Pelvic Floor and Perineum

Answer 5

Muscles of superficial perineal space
Ischiocavernosus
Bulbospongiosus
Superficial transverse perineal muscles

External anal sphincter in posterior half of perineum

Question 6

Superficial Muscles of the Thorax

Answer 6

Most - extrinsic shoulder muscles
Act in combination to fix shoulder girdle (mostly scapula); move it to increase range of arm movements
Actions - elevation, depression, rotation, lateral and medial movements, protraction, and retraction

Two groups of muscles: anterior and posterior

Muscles of anterior thorax:

Pectoralis minor
Serratus anterior
Subclavius

Question 7

Superficial Muscles of the Posterior Thorax

Answer 7

Posterior extrinsic shoulder muscles:

Trapezius
Levator scapulae
Rhomboids (major and minor)