Fundamentals of Anatomy and Physiology

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pol-ISS-is) muscles flex the thumb, pollicis coming from
the Latin for “thumb.” The two extensor pollicis
muscles extend the thumb. Refer to Table 9-6. The

• adductor pol-licis muscle adducts the thumb; the two
  abductor- pollicis muscles abduct the thumb. The
  unique opponens (oh-POH-nenz) pollicis flexes and
  opposes the thumb and is used when we write.

Muscles Moving the Fingers

The flexor digitorum (FLEKS-ohr dij-ih-TOHR-um)
muscles flex the fingers; the extensor digitorum muscle
extends the fingers. Refer to Table 9-6. The little finger and
the index finger have separate similar muscles. The
interossei (in-tehr-OSS-eye) muscles, found between the
metacarpals, cause abduction of the proximal phalanges of
the fingers. The tendons of the extensor digitorum are
visible on the surface of your hand. Extend your fingers to
view these tendons.

Muscles of the Abdominal Wall

Three layers of muscles along the side of the abdomen
constrict and hold the abdominal contents in place. They are
from outer to inner: the external oblique, the internal
oblique, and the transversus abdominis. In the front over

Chapter 9

your belly is the rectus abdominis. This is the muscle

that we develop when we do sit-ups and try to get that

“wash-board” look. Table 9-7 lists the muscles of the

abdominal wall and respiration. See Figure- 9-10.

Muscles of Respiration or Breathing

The main muscle used in breathing is the diaphragm

(DYE-ah-fram). Its contracting causes air to enter the

lungs. When it relaxes, air is expelled from the lungs. To

expand the ribs while the lungs fill with air, the external

and internal intercostal muscles come into play. The ex-

ternal intercostals elevate the ribs when we breathe in or

inspire, and the internal intercostals depress the ribs when

we breathe out or expire. Refer to Table 9-7.

Muscles Moving the Femur

Refer to Table 9-8 for the list of muscles involved in mov-ing

the thigh or femur. The psoas (SO-us) muscles and the

iliacus (ill-ee-ACK-us) muscle flex the thigh. Three gluteal

muscles form the buttocks: the gluteus (GLOO-tee-us)

maximus forms most of the buttocks; the gluteus medius,

where injections are administered, is above and lateral to the

maximus; and the gluteus minimus. The glu-teus maximus

extends the thigh. There are two adductor muscles and one

abductor. The tensor fascia lata (TIN-sir

Table 9- 7 Muscles of the Abdominal Wall and Respiration

Muscles of the Abdominal Wall^
Muscle Origin Insertion Function
External oblique Lower eight ribs Iliac crest Anterior rectus Compresses abdominal
sheath contents
Internal oblique Iliac crest Costal cartilage lower Compresses abdominal

(^) three or four ribs contents
Transversus abdominis Iliac crest cartilage of Xiphoid cartilage Compresses abdominal
(^) lower six ribs linea alba contents
Rectus abdominis Crest of pubis, Cartilage of 5th, 6th, Flexes vertebral column, assists-
pubic symphysis 7th rib in compressing abdominal- wall
Muscles of Respiration^
Muscle Origin Insertion Function
Diaphragm Xiphoid process, costal Central tendon Increases vertical diameter of
cartilages, lumbar thorax
(^) vertebrae
External intercostals Lower border of rib Upper border of rib below Draws adjacent ribs together
Internal intercostals Ridge on inner surface Upper border of rib below Draws adjacent ribs together
of rib
Quadratus lumborum Iliac crest Last rib and upper four Flexes trunk laterally
lumbar vertebrae
(^) ®
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