Muscles Acting on the Hip and Lower Limb

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Objectives

When you have completed this section, you should be able to

• name and locate the muscles that act on the hip, knee, ankle, and toe joints;

• relate the actions of these muscles to the joint movements described in chapter 9; and

• describe the origin, insertion, and innervation of each muscle.

The deep lateral rotators of the pelvic region (table 10.17; fig. 10.31) rotate the femur laterally, as when you cross your legs to rest an ankle on your knee. Thus, they oppose medial rotation by the gluteus medius and minimus. Most of them also abduct or adduct the femur. The abductors are important in walking because, when we lift one foot from the ground, they shift the body weight to the other leg and prevent us from falling over.

The fascia lata49 is a fibrous sheath that encircles the thigh and tightly binds its muscles. On the lateral surface,

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

10. The Muscular System

Text

© The McGraw-H Companies, 2003

370 Part Two Support and Movement

Palmar aspect, superficial

Palmar aspect, deep

Tendon sheath

Tendon of flexor digitorum profundus

Tendon of flexor digitorum superficialis

Lumbricals

Opponens digiti minimi

Flexor digiti minimi brevis

Abductor digiti minimi

Flexor retinaculum

Tendons of:

Flexor carpi ulnaris

Flexor digitorum superficialis

Palmaris longus (a)

Adductor Pollicis Longus

First dorsal interosseous

Tendon of flexor pollicis longus

First dorsal interosseous

Tendon of flexor pollicis longus

Adductor pollicis Flexor pollicis brevis

Abductor pollicis brevis

Opponens pollicis

Tendons of: Abductor pollicis longus Flexor carpi radialis Flexor pollicis longus

Palmar interosseous

Opponens digit minimi n

Opponens digit minimi

Abd Pollicis Longus

Flexor retinaculum (cut)

Carpal tunnel rm

Opponens pollicis

Tendons of: Abductor pollicis longus

Flexor carpi radialis

Flexor carpi ulnaris

Dorsal aspect

Abductor pollicis brevis

Common tendon sheath of extensor digitorum and extensor indicis

Tendons of extensor pollicis brevis and abductor pollicis longus

Abductor pollicis brevis

Flexor Carpi Superficialis Brevis

Tendons of extensor digitorum (cut)

Dorsal interosseous Abductor digiti minimi

Extensor pollicis longus superficialis

Tendons of extensor digitorum (cut)

Dorsal interosseous Abductor digiti minimi

Extensor retinaculum Tendons of:

Extensor digiti minimi Extensor carpi ulnaris

Tendon of flexor digitorum superficialis Lumbrical

Opponens digiti minimi Flexor digiti minimi brevis Abductor digiti minimi

Pisiform bone Flexor digitorum

Extensor pollicis longus superficialis

Extensor Pollicis Brevis

Tendon of extensor pollicis brevis

Tendon of flexor carpi radialis

Adductor pollicis

Flexor pollicis brevis

Abductor pollicis brevis

Tendon of extensor pollicis brevis

Tendon of flexor carpi radialis

Figure 10.29 Intrinsic Muscles of the Hand. Boldface labels indicate: (a) superficial muscles, anterior (palmar) view; (b) deep muscles, anterior view; (c) superficial muscles, posterior (dorsal) view; (d) anterior (palmar) view of cadaver hand.

Saladin: Anatomy & I 10. The Muscular System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 10 The Muscular System 371

Table 10.16 Intrinsic Muscles of the Hand (see fig. 10.29)

O = origin, I = insertion, N = innervation (n. = nerve, nn. = nerves)

Table 10.16 Intrinsic Muscles of the Hand (see fig. 10.29)

O = origin, I = insertion, N = innervation (n. = nerve, nn. = nerves)

Thenar Group

Abductor Pollicis (PAHL-ih-sis) Brevis

Abducts thumb

O: scaphoid, trapezium, flexor retinaculum

I: lateral aspect of proximal phalanx I

N: median n.

Adductor Pollicis

Adducts thumb and opposes it to the fingers O: trapezium, trapezoid, capitate, metacarpals II—IV

I: medial aspect of proximal phalanx I

N: ulnarn.

Flexor Pollicis Brevis

Flexes thumb at metacarpophalangeal joint O: trapezium, flexor retinaculum

I: proximal phalanx I

N: median and ulnar nn.

Opponens (op-OH-nens) Pollicis

Opposes thumb to fingers O: trapezium, flexor retinaculum

I: metacarpal I

N: median n.

Hypothenar Group

Abductor Digiti Minimi

Abducts little finger

O: pisiform, tendon of flexor carpi ulnaris

I: medial aspect of proximal phalanx V

N: ulnar n.

Flexor Digiti Minimi Brevis

Flexes little finger at metacarpophalangeal joint O: hamulus of hamate, flexor retinaculum

I: medial aspect of proximal phalanx V

N: ulnar n.

Opponens Digiti Minimi

Opposes little finger to thumb; deepens pit of palm O: hamulus of hamate, flexor retinaculum

I: medial aspect of metacarpal V

N: ulnar n.

Midpalmar Group

Dorsal Interosseous (IN-tur-OSS-ee-us) Muscles (four muscles)

Abduct digits II-IV

O: two heads on facing sides of adjacent metacarpals

I: proximal phalanges II-IV

N: ulnar n.

Palmar Interosseous Muscles (three muscles)

Adduct digits II, IV, and V O: metacarpals II, IV, and V

I: proximal phalanges II, IV, and V

N: ulnar n.

Lumbricals (four muscles)

Flex metacarpophalangeal joints; extend interphalangeal joints O: tendons of flexor digitorum profundus

I: proximal phalanges II-V

N: median and ulnar nn.

1 Saladin: Anatomy & 1 10. The Muscular System 1 Text 1 1 Physiology: The Unity of Form and Function, Third Edition

© The McGraw-Hill Companies, 2003

Table 10.17 Muscles Acting on the Hip and Femur (see figs. 10.30-10.34)

O = origin, I = insertion, N = innervation (n. = nerve, nn. = nerves)

Anterior Muscles of the Hip (Iliopsoas)

Iliacus (ih-LY-uh-cus)

Flexes hip joint; medially rotates femur

O: iliac fossa I: lesser trochanter of femur, capsule of coxal joint

N: femoral n.

Psoas (SO-ass) Major

Flexes hip joint; medially rotates femur

O: vertebral bodies T12-L5 I: lesser trochanter of femur

N: lumbar plexus

Lateral and Posterior Muscles of the Hip

Tensor Fasciae Latae (TEN-sor FASH-ee-ee LAY-tee)

Flexes hip joint; abducts and medially rotates femur, tenses fascia lata and braces knee when opposite foot is lifted from ground

O: iliac crest near anterior superior spine I: lateral condyle of tibia N: superior gluteal n.

Gluteus Maximus

Extends hip joint; abducts and laterally rotates femur; important in the backswing of the stride O: ilium and sacrum I: gluteal tuberosity of femur, fascia lata

N: inferior gluteal n.

Gluteus Medius and Gluteus Minimus

Abduct and medially rotate femur; maintain balance by shifting body weight during walking O: ilium I: greater trochanter of femur

N: superior gluteal n.

Lateral Rotators

Gemellus (jeh-MEL-us) Superior and Gemellus Inferior

Laterally rotate femur

O: body of ischium I: obturator internus tendon

N: sacral plexus

Obturator (OB-too-RAY-tur) Externus

Laterally rotates femur

O: anterior margin of obturator foramen I: greater trochanter of femur

N: obturator n.

Obturator Internus

Abducts and laterally rotates femur

O: posterior margin of obturator foramen I: greater trochanter of femur

N: sacral plexus

Piriformis (PIR-ih-FOR-miss)

Abducts and laterally rotates femur

O: anterolateral aspect of sacroiliac region I: greater trochanter of femur

N: ventral rami of S1-S2

Quadratus Femoris (quad-RAY-tus FEM-oh-riss)

Adducts and laterally rotates femur

O: ischial tuberosity I: intertrochanteric ridge of femur

N: sacral plexus

Medial (Adductor) Compartment of the Thigh

Adductor Longus and Adductor Brevis

Adduct and laterally rotate femur; flex hip joint

O: pubis I: posterior shaft of femur

N: obturator n.

Saladin: Anatomy & I 10. The Muscular System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 10 The Muscular System 373

Table 10.17 Muscles Acting on the Hip and Femur (see figs. 10.30-10.34) (continued)

Adductor Magnus

Anterior part adducts and laterally rotates femur and flexes hip joint; posterior part extends hip joint O: ischium I: posterior shaft of femur

N: obturator and tibial nn.

Gracilis (GRASS-ih-lis)

Adducts femur; flexes knee; medially rotates tibia

O: pubis I: medial aspect of proximal tibia

N: obturator n.

Pectineus (pec-TIN-ee-us)

Adducts and laterally rotates femur; flexes hip

O: pubis I: posterior aspect of proximal femur

N: femoral n.

Iliopsoas

Iliacus

Psoas major

Pectineus

Adductor magnus

Adductor brevis

Adductor longus

Gracilis-

Iliopsoas

Iliacus

Psoas major

Pectineus

Adductor magnus

Adductor brevis

Adductor longus

Gracilis-

Tendons The Gluteus

Piriformis

Obturator externus

Insertion of-^-

gracilis on tibia

Figure 10.30 Muscles Acting on the Hip and Femur. 50graeil = slender

Anterior view. 51pectin = comb

Piriformis

Insertion of-^-

gracilis on tibia

Obturator externus it combines with the tendons of the gluteus maximus and tensor fasciae latae to form the iliotibial band, which extends from the iliac crest to the lateral condyle of the tibia (fig. 10.32). The tensor fasciae latae tautens the ili-otibial band and braces the knee, especially when we raise the opposite foot.

The fascia lata divides the thigh muscles into three compartments, each with its own nerve and blood supply: the anterior (extensor) compartment, medial (adductor) compartment, and posterior (flexor) compartment. Muscles of the anterior compartment function mainly as extensors of the knee, those of the medial compartment as adductors of the femur, and those of the posterior compartment as extensors of the hip and flexors of the knee.

In the medial compartment are five muscles that act on the hip joint—the adductor longus, adductor brevis, adductor magnus, gracilis,50 and pectineus51 (see fig. 10.30). All of them adduct the thigh, but some cross both the hip and knee joints and have additional actions noted in table 10.17.

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