David Shier Hole's Human Anatomy and Physiology 2010, page 354 read online

323

CHAPTER NINE

Muscular System

walks, runs, or climbs. It is also used to raise the body from a

sitting position (see F

g. 9.38).

The

gluteus medius

(gloo

′

te-us me

′

de-us) is partly cov-

ered by the gluteus maximus. Its F bers extend from the ilium

to the femur, and they abduct the thigh and rotate it medially

(see F

g. 9.38).

The

gluteus minimus

(gloo

′

te-us min

′

˘-mus) lies beneath

the gluteus medius and is its companion in attachments and

functions (see F

g. 9.38).

The

piriformis

(pir-ı˘-for

′

mis) is shaped like a pyramid

and located inferior to the gluteus minimus. It abducts and

laterally rotates the thigh and is part of the posterior group of

muscles that stabilizes the hip.

The

tensor fasciae latae

(ten

′

sor fash

′

e-e lah-te

¯) connects

the ilium to the iliotibial tract (fascia of the thigh), which con-

tinues downward to the tibia. This muscle abducts and ﬂ

exes

the thigh and rotates it medially (see F

g. 9.38).

The gluteus medius and gluteus minimus help support and maintain

the normal position of the pelvis. If these muscles are paralyzed as a

result of injury or disease, the pelvis tends to drop to one side when-

ever the foot on that side is raised. Consequently, the person walks

with a waddling limp called the

gluteal gait

Thigh Adductors

The

pectineus

(pek-tin

′

e-us) muscle runs from the spine of the

pubis to the femur. It ﬂ exes and adducts the thigh (see F g. 9.37).

The

adductor brevis

(ah-duk

′

tor brev

′

ı˘s) is a short, tri-

angular muscle that runs from the pubic bone to the femur.

It adducts the thigh and assists in ﬂ

exing and rotating it later-

ally (see F

g. 9.37).

The

adductor longus

(ah-duk

′

tor long

′

gus) is a long, tri-

angular muscle that runs from the pubic bone to the femur. It

adducts the thigh and assists in ﬂ

exing and rotating it later-

ally (see F

g. 9.37).

The

adductor magnus

(ah-duk

′

tor mag

′

nus) is the largest

adductor of the thigh. It is a triangular muscle that connects

Muscles That Move the Thigh

The muscles that move the thigh are attached to the femur

and to some part of the pelvic girdle. (An important exception

is the sartorius, described later.) They can be separated into

anterior and posterior groups. The muscles of the anterior

group primarily ﬂ

ex the thigh; those of the posterior group

extend, abduct, or rotate it. The muscles in these groups are

shown in

figures 9.37, 9.38, 9.39

, and

9.40

, in reference

plates 71 and 72, and are listed in

table 9.12

. Muscles that

move the thigh include the following:

Anterior Group

Posterior Group

Psoas major

Gluteus maximus

Iliacus

Gluteus medius

Gluteus minimus

Piriformis

Tensor fasciae latae

Another group of muscles, attached to the femur and pelvic

girdle, adducts the thigh. This group includes the following:

Pectineus

Adductor magnus

Adductor brevis

Gracilis

Adductor longus

Anterior Group

The

psoas

(so

′

as)

major

is a long, thick muscle that con-

nects the lumbar vertebrae to the femur. It ﬂ

exes the thigh

(see F g. 9.37).

The

iliacus

(il

′

e-ak-us), a large, fan-shaped muscle, lies

along the lateral side of the psoas major. The iliacus and the

psoas major are the primary flexors of the thigh, and they

advance the lower limb in walking movements (see F g. 9.37).

Posterior Group

The

gluteus maximus

(gloo

′

te-us mak

′

si-mus) is the largest

muscle in the body and covers a large part of each buttock. It

connects the ilium, sacrum, and coccyx to the femur by fas-

cia of the thigh and extends the thigh. The gluteus maximus

helps to straighten the lower limb at the hip when a person

TABLE

9.11

Muscles of the Pelvic Outlet

Muscle

Origin

Insertion

Action

Nerve Supply

Levator ani

Pubic bone and

ischial spine

Coccyx

Supports pelvic viscera and provides

sphincterlike action in anal canal and vagina

Pudendal n.

Coccygeus

Ischial spine

Sacrum and coccyx

Same as above

S4 and S5 nerves

SuperF

cial transversus perinei

Ischial tuberosity

Central tendon

Supports pelvic viscera

Pudendal n.

Bulbospongiosus

Central tendon

Males: Urogenital diaphragm and

fascia of penis

±emales: Pubic arch and root of clitoris

Males:

Assists emptying of urethra and assists

in erection of penis

±emales:

Constricts vagina and assists in

erection of cltoris

Pudendal n.

Ischiocavernosus

Ischial tuberosity

Pubic arch

Males: Erects penis

±emales: Erects clitoris

Pudendal n.

Sphincter urethrae

Margins of pubis

and ischium

±ibers of each unite with those from

other side

Opens and closes urethra

Pudendal n.