Copyright © 2010 Pearson Education, Inc. Chapter 10 The Muscular System Part B Shilla Chakrabarty,...

Copyright © 2010 Pearson Education, Inc.

Chapter 10

The Muscular System

Part B

Shilla Chakrabarty, Ph.D.


Muscles of the Thorax

• Muscles of respiration

• External intercostals—more superficial muscles that elevate ribs for inspiration

• Internal intercostals—deeper muscles that aid forced expiration

• Diaphragm

• Partition between thoracic and abdominal cavities

• Most important muscle in inspiration

• Innervated by phrenic nerves

Copyright © 2010 Pearson Education, Inc. Figure 10.10a

Externalintercostal

(a) Internalintercostal

Copyright © 2010 Pearson Education, Inc. Figure 10.10b

Foramen foresophagusCostal cartilage

Lumbarvertebra

Xiphoid process of sternum

Diaphragm

Quadratuslumborum Psoas major

Foramen for inferiorvena cava

Centraltendon ofdiaphragm

Foramenfor aorta

12th rib

(b)


Muscles of the Abdominal Wall

• Four paired muscles; their fasciae and aponeuroses form the lateral and anterior abdominal wall

• Muscles that flex vertebral column and compress abdominal wall are:

• Internal obliques

• External obliques

• Transversus abdominis

• Rectus abdominis

• Origin Pubic crest and symphysis

• Insertion Xiphoid process and costal cartilage of ribs 5-7

• Function Flex and rotate lumbar region of vertebral column

Copyright © 2010 Pearson Education, Inc. Figure 10.11a

Transversus abdominis

Internal oblique

External oblique

Aponeurosis of theexternal oblique

(a)

Pectoralis major

Linea alba

Tendinousintersection

Rectusabdominis

Inguinal ligament(formed by free inferior border of the external oblique aponeurosis)

Serratus anterior


Muscles of the Abdominal Wall

• Fascicles of these muscles run at angles to one another, providing added strength

• All are innervated by intercostal nerves

• Actions of these muscles

• Lateral flexion and rotation of the trunk

• Help promote urination, defecation, childbirth, vomiting, coughing, and screaming

Copyright © 2010 Pearson Education, Inc. Figure 10.11b

Transversusabdominis

Inguinalligament

Lumbarfascia

Lumbarfascia

Internaloblique

Pubictubercle

Rectusabdominis

Externaloblique

(b)

IIiac crest


Muscles of the Pelvic Floor • Pelvic floor (pelvic diaphragm) is composed of two paired muscles

• Levator ani

• Coccygeus

• Both are innervated by sacral nerves

• Functions of the pelvic diaphragm

Seals the inferior outlet of the pelvis

Supports pelvic organs

Lifts pelvic floor to help release feces

Resists increased intra-abdominal pressure

Pelvicdiaphragm

Symphysis pubis

(a)

Levator aniPiriformis

Posterior

Anterior

Coccyx

Coccygeus

Obturatorinternus

IIiococcygeusLevatorani

PubococcygeusUrogenital diaphragm

UrethraVagina

Anal canal


Superficial Muscles of the Thorax

• Most are extrinsic shoulder muscles

Act in combination to fix the shoulder girdle (mostly the scapula) and move it to increase range of arm movements

Actions include elevation, depression, rotation, lateral and medial movements, protraction, and retraction

• Two groups of muscles: anterior and posterior


Superficial Muscles of the Thorax

• Anterior extrinsic shoulder muscles

• Pectoralis minor

• Serratus anterior

• Subclavius

SubclaviusClavicle

SubscapularisPectoralis minor

Coracobrachialis

Serratus anterior

Humerus

Sternocleido-mastoid

DeltoidPectoralismajor Sternum

Biceps brachii

(a)


Superficial Muscles of the Posterior Thorax

• Posterior extrinsic shoulder muscles

Trapezius

Levator scapulae

Rhomboids (major and minor)

Trapezius

(c)

Levatorscapulae

Supraspinatus

Clavicle

Spine ofscapula

InfraspinatusTeres minor

Humerus

Deltoid

Teres major

Latissimusdorsi

RhomboidminorRhomboidmajor


Muscles Crossing the Shoulder Joint

• Nine muscles cross the shoulder joint to insert on and move the humerus

• Some originate off the scapula; others originate off the axial skeleton

• Three are prime movers of the arm

• Pectoralis major

• Latissimus dorsi

• Deltoid

• Actions include flexion, extension, adduction, abduction, and rotation of humerus



• Four muscles are rotator cuff muscles

• Supraspinatus

• Infraspinatus

• Teres minor

• Subscapularis

• Reinforce the capsule of the shoulder

• Act as synergists and fixators

• Two additional muscles are synergists: coracobrachialis and teres major

Muscles Crossing the Elbow Joint

• Posterior extensor muscles

• Triceps brachii—prime mover of forearm extension

• Anconeus—weak synergist


Supraspinatus*Spine of scapula

(b) Posterior view

Deltoid (cut)Greater tubercleof humerusInfraspinatus*

Teres minor*

Teres major

Triceps brachii:

Latissimus dorsi

Humerus

Olecranon processof ulna

Lateral head Long head

Anconeus

* Rotator cuff muscles

Clavicle

Deltoid

Sternum

Pectoralis major

Lateral headLong headMedial head

Coracobrachialis

Triceps brachii:

Biceps brachii

BrachialisBrachioradialis

(a) Anterior view



Muscles of the Forearm

• Actions: movements of the wrist, hand, and fingers

• Most anterior muscles are flexors

• Some forearm muscles act to produce pronation and supination of the forearm

Biceps brachii

Tendon of biceps brachii

Pronator teres

Brachioradialis

Extensor carpi radialis longus

Flexor pollicis longus

Pronator quadratus

Flexor retinaculum

Medial head oftriceps brachii

Medial epicondyleof humerus

Flexor carpi radialis

Palmar aponeurosis

Superficial transverseligament of palm

Palmaris longus

Flexor carpi ulnaris

Flexor digitorumsuperficialis

(a)


Insertion oftriceps brachii

Anconeus

Flexor carpiulnaris

Extensor carpiulnaris

Extensor digitiminimi

Extensor indicis

Tendons of extensor carpiradialis brevis and longus

Extensorexpansion

(a)

Extensor pollicislongus

Extensor pollicisbrevis

Abductorpollicis longus

Extensor digitorum

Extensor carpiradialis brevis

Extensor carpiradialis longus

Brachioradialis

Tendons ofextensordigitorum• Most posterior muscles

are extensors

Muscles of the Forearm

Antero-medial Postero-lateral


Intrinsic Muscles of the Hand

• Small weak muscles

• Lie entirely within the palm of the hand

• Control precise movements of metacarpals and fingers (e.g., threading a needle)

• Abductors and adductors of the fingers

• Produce opposition—move the thumb toward the little finger


Muscles Crossing Hip and Knee Joints

• Most anterior muscles flex the femur at the hip and extend the leg at the knee (fore swing of walking)

• Most posterior muscles extend the thigh and flex the leg (backswing of walking)

• Medial muscles all adduct the thigh

• All three groups are enclosed by the fascia lata


Movements of the Thigh

• Include flexion, extension, abduction, adduction, circumduction, and rotation

• Thigh flexors pass in front of the hip joint

• Iliopsoas (iliacus and psoas major): prime mover of flexion

• Tensor fasciae latae

• Rectus femoris

• Assisted by medial adductors and sartorius

Psoas minor

Iliac crestPsoas major

Iliopsoas

12th rib

Quadratus lumborum

Iliacus

Anterior superior iliac spine

Tensor fasciae latae

Pectineus

Sartorius

Quadriceps femoris

• Rectus femoris

• Vastus lateralis

• Vastus medialis

(a)

Adductor magnus

PatellaPatellar ligament

Tendon of quadriceps femoris

12th thoracic vertebra

5th lumbar vertebra

Adductor longus

Gracilis


Movements of the Thigh

• Thigh extensors

• Hamstring muscles (prime movers of extension)

• Biceps femoris

• Semitendinosus

• Semimembranosus

• Gluteus maximus (prime mover during forceful extension)


Muscles of the Thigh that Move the Knee Joint

• Quadriceps femoris—sole extensor of the knee

• Hamstring muscles—flex the knee, and are antagonists to the quadriceps femoris

Psoas minor

Iliac crestPsoas major

Iliopsoas

12th rib

Quadratus lumborum

Iliacus

Anterior superior iliac spine

Tensor fasciae latae

Pectineus

Sartorius

Quadriceps femoris

• Rectus femoris

• Vastus lateralis

• Vastus medialis

(a)

Adductor magnus

PatellaPatellar ligament

Tendon of quadriceps femoris

12th thoracic vertebra

5th lumbar vertebra

Adductor longus

Gracilis


Muscles of the Anterior Compartment of the Leg

Fibularis longus

Gastrocnemius

Tibia

Tibialis anterior

Extensor digitorum longus

Soleus

Extensor hallucis longus

Fibularis tertius

Extensor hallucis brevis

Extensor digitorum brevis

Superior and inferiorextensor retinacula

(a)

• Primary toe extensors and ankle dorsiflexors

• Tibialis anterior

• Extensor digitorum longus

• Extensor hallucis longus

• Fibularis tertius (not always present)


Muscles of the Posterior Compartment of the Leg

Gastrocnemius

Plantaris

Medial headLateral head

Tendon ofgastrocnemius

Calcaneal tendon

Medial malleolus Lateral malleolus

Calcaneus

(a) Superficial view of the posterior leg.

• Flexors of the foot and the toes

• Gastrocnemius

• Soleus

• Plantaris

• Popliteus

• Tibialis posterior

• Flexor digitorum longus

• Flexor hallucis longus


Anterior Posterior

Muscles Origin Insertion Function

Ilipsoas Transverse processes ofT12-L5; iliac fossa

Lesser trochanter of femur

Major flexion of thigh

Sartorius Anterior superior iliac spine Proximal tibia Flexes and laterally rotates thigh


Lateral Medial

Copyright © 2010 Pearson Education, Inc. Chapter 10 The Muscular System Part B Shilla Chakrabarty,...

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