Trunk Outline

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Trunk – Outline – spring 2022

Introduction

Anterior vs. Posterior muscles – Which are more superficial and which are deeper?

Anterior Muscles:

Rectus abdominis – two parts are separated by the linea alba -

External Oblique(V-shaped) -

Internal Oblique (ᶺ-shaped) -

Transverse abdominis –

Posterior Muscles:

Erector spinae:

Three portions:

Iliocostalis portion

Longissimus portion

Spinalis portion

Transversospinalis

Interspinalis

Intertransversarii

Quadratus lumborum

Some posterior muscles extend to the head/neck:

Innervations

Spinal nerves

T12-L1

intercostal

iliohypogastric

ilioinguinal

Osteology

Xyphoid process on sternum

Vertebral bodies

Ribs

Pelvic bone

Actions – list all actions of the trunk

Extension

Lateral bending

Rotation to same side

Rotation to opposite side

Soft tissue structures

Anterior

Linea alba – narrow, thick band of connective tissue –

Abdominal aponeurosis – ant. flat band of connective tissue –

Inguinal ligament - landmark that separates the anterior abdominal wall from the thigh –

Postero-lateral

Thoracolumbar aponeurosis – broad, flat band – attachment site for latissimus dorsi and erector spinae

Muscles – add the actions

ANTERIOR

Muscles

Actions

Innervations

Rectus abdominis

Origin: Pubic Crest

Insertion: Xiphoid Process of costal cartilages 5-7 ribs

Trunk flexion

Compression of abdomen

7th-12th intercostal nerves

External Oblique

(V-shaped)

Origin: Iliac crest, pubic tubercle, and linea alba

Insertion: Lower 8 ribs laterally

Bilateral:

Trunk Flexion

Compression of abdomen

Unilateral:

Lateral bending to same side

Rotation to opposite side

8th-12th intercostal; iliohypogastric and ilioinguinal

Internal Oblique

(ᶺ-shaped)

Origin: Inguinal ligament, iliac crest, thoracolumbar fascia

Insertion: 8-12th ribs, linae alba

Bilateral:

Trunk flexion

Compression of abdomen.

Unilateral:

Lateral bending

Rotation to same side

8th-12th intercostal; iliohypogastric and ilioinguinal

Transverse abdominis

Origin: Inguinal ligament, iliac crest, thoracolumbar fascia, and costal cartilages of the last seven ribs.

Insertion: pubic crest, abdominal aponeurosis, and linea alba

Compression of abdomen

7th-12th intercostal; iliohypogastric and ilioinguinal

POSTERIOR

Muscles

Actions

Innervations

Erector spinae

Has 3 portions with it:

Iliocostalis portion

Origin: iliac crest, lower ribs

Insertion: angles of ribs, upper ribs and transverse processes of cervical vertebrae

Longissimus portion

Origin: Transverse process at lower levels

Insertion: Transverse processes at upper levels, mastoid process

Spinalis portion

Origin: Spinous processes below

Insertion: Spinous processes above

Bilateral:

Extend neck and trunk

Unilateral:

Rotate head

laterally bend neck

trunk to the same side

spinal nerves

Transversospinalis

Origin: Transverse processes

Insertion: Spinous processes of vertebrae above

Bilateral:

Extend neck and trunk

Unilateral:

Rotate head, neck and trunk to opposite side

spinal nerves

Interspinalis

Origin: spinous process below

Insertion: Spinous Process above

Neck and trunk extension

spinal nerves

Intertransversarii

Origin: spinous process below

Insertion: Spinous Process above

Neck and trunk lateral bending to the same side.

spinal nerves

Quadratus lumborum

Origin: iliac crest

Insertion: 12th rib, transverse process of all 5 lumbar vertebrae

Trunk lateral bending

T12-L1

Prime movers of the Neck and Trunk:

Actions

muscles

Head (occiput on C1)

Flexion

Prevertebral group

Extension

Suboccipital group

Neck

Flexion

Sternocleidomastoid

Extension

Splenius capitis

Splenius cervicis

Erector spinae

Transversospinalis

Interspinales

Lateral bending (R/L)

Sternocleidomastoid

Splenius capitis

Splenius cervicis

Scalenes

Erector spinae

Intertransversarii

Rotation (same side)

Splenius capitis

Splenius cervicis

Rotation (opposite side)

Sternocleidomastoid

Transversospinalis

Trunk

Flexion

Rectus abdominis

External oblique

Internal oblique

Extension

Erector spinae

Transversospinalis

Interspinales

Lateral bending

Quadratus lumborum

Erector spinae

Internal oblique

External oblique

Intertransversarii

Rotation same side

Internal oblique

Rotation opposite side

External oblique

Transversospinalis

Compression of abdomen

Rectus abdominis

External oblique

Internal oblique

Transverse abdominis

Points to remember: (from textbook)

When a muscle contracts, it knows no direction it simply shortens

When a muscle contract it usually moves it insertion (more moveable end) toward its origin (more stable end).

A muscle insertion is usually the distal end and the more movable end.

A muscle origin is usually the proximal end and the more stable end

Reversal of muscle action occurs when the origin becomes more moveable and moves towards the insertion which has become more stable

Concentric contractions occur when the body part is moving against gravity

Eccentric contractions occurs when the body part is moving in the same direction as the pull of gravity

Isometric contractions occur when a muscle contracts, but no significant joint motion occurs

The muscle group contracting isometrically is the same group as if the joint were contracting concentrically.