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All educational material published, presented and distributed through all my Patient Centered Healthcare Success Online Courses, including this course Chronic Non Specific Lower Back Pain and Related Pathologies, Copyright © 2019, is not to be used or reproduced in any manner without written permission. Enquiries concerning reproduction will be sent directly to: [email protected]. I have specifically designed all curriculum course content to provide all participants with current scientific evidence based knowledge, to improve your medical knowledge base, and improve clinical outcomes. It is not to be used to replace any current recommendations from medical doctors, and/or specialists clinical treatment plan guidelines for participants respective medical conditions.

• Maria Angela Therese Bewcyk, MPT BAppSci

Basic Anatomy of the Lumbar Spine & Core Musculature

**Background Information**

Basic Anatomy of the Lumbar Spine and Associated Structures

Origin 

• The point at which a muscle attaches to a bone
• Often, the more proximal attachment of a muscle
• The structure that the origin is attached to, is not moved by the contraction of the muscle

Insertion 

• The point at which a muscle attaches to a bone
• The insertion attaches to the structure that will be moved by the contraction of the muscle
• Insertions are usually the more distal connection of a muscle via tendon to bone

Action

• A muscle can act in two ways to effect a joint
• The action at a joint often occurs as a result of concentric action
• May also refer to the Reverse Action; an action at a joint due to eccentric action

Specific Muscle Function(s)

Prime mover/agonist:  a muscle whose action is chiefly responsible for producing a particular movement

Spurt:  occurs during rapid movements and along the long axis of the moving bone

• Generally, larger moment arms, for the production of force

Shunt: small moment arm for movement production, acts to stabilize the joint

Assistant mover: this action helps to produce the desired movement, but the muscle is not entirely responsible for producing the movement

Antagonists: actions oppose the agonist

Synergists: upon contraction, synergists assist the prime mover in performing actions 

• Stabilize the joint during a contraction

Neutralizers: help cancel out, or neutralize, additional motion from the agonists, to ensure the force generated works within the desired plane of motion

Co-Synergists

Stabilizers: act to stabilize the joint during movement

"Force Couple": Two equal, but oppositely directed forces, acting simultaneously on opposite sides of an axis of rotation. Since the translatory forces (forces that produce linear motion) cancel out each other, a force couple, produces torque (rotatory forces) only

• The magnitude of the force couple is the sum of the products of each force and its moment arm.

Tendon Sheath: a layer of membrane around a tendon, permitting the tendon to move

**From a functional anatomy standpoint, simple motion analysis looks at which joints are moving, the direction and range of these joint movements in relation to anatomical planes and axes, the forces acting on the joints to resist or assist motion, which muscles and/or muscle groups are the principal muscles contracting and how these muscles are working/interacting to produce the desired movement.**

Key Features & Functions of the Adult Spinal Cord

Structure & Components of the Spinal Cord.

Dorsal roots 

• One of the two roots of a spinal nerve that passes dorsally to the spinal cord
• A collection of afferent nerves (fibres) from the periphery which transmits sensory information into the spinal cord

Dorsal root (spinal) ganglia (DRG)

• a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves
• These cells transmit afferent sensory information from the periphery to the CNS

Ventral roots

• one of two the two roots of a spinal nerve that passes ventrally to the spinal cord
• A collection of efferent nerve fibres that exit the spinal cord and transmit motor information to muscles of the periphery.

Cross-Sectional View of the Lumbar Spinal Cord.

Spinal nerves

• There are 31 pairs of nerves, formed by the dorsal and ventral roots of the spinal cord, which arise from its corresponding levels.
• They connect and transmit motor and sensation information between the body and the Central Nervous System.

Dorsal Rami

• The posterior branches (or divisions) of the spinal nerves.
• Smaller than the anterior divisions.

Ventral Rami

• Anterior branch, anterior divisions of the spinal nerves.

Lumbosacral Enlargement

• A thickening of the spinal cord from T9-12
• Gives rise to nerves supplying the lower limbs
• It reaches its maximum circumference, of about 33 mm, opposite to the last thoracic vertebra, below which it tapers rapidly into the conus medullaris
• Main Function: Increases neural input and output to the upper extremities

Spinal Nerves L1-4: Forming the Lumbar Plexus

• the lumbar plexus in the lumbar region of the body, forms part of the lumbosacral plexus
• the nerves which encompass the lumbar plexus, pass in front of the hip joint and mainly support the anterior part of the thigh
• this plexus is formed lateral to the intervertebral foramina and passes through psoas major
• its smaller motor branches are distributed directly to psoas major, while the larger branches leave the muscle at various sites, to run obliquely downward through the pelvic area, to leave the pelvis under the inguinal ligament, with the exception of the obturator nerve, which exits the pelvis through the obturator foramen

Spinal Nerves L4&5,S1-3 Forming the Lumbosacral Plexus

• the anterior divisions of the lumbar nerves, sacral nerves, and coccygeal nerves form the lumbosacral plexus
• the first lumbar spinal nerve is frequently joined by a branch from the twelfth thoracic spinal nerve
• for descriptive purposes, this plexus is usually divided into three parts:
• lumbar plexus
• sacral plexus
• pudendal plexus

*conus medullaris* - the terminal end of the spinal cord, near lumbar vertebral levels L1 and L2 . After the spinal cord tapers out, the spinal nerves continue as dangling nerve roots known as the cauda equina

The Dorsal Horn

• posterior grey region of the spinal cord
• contains cell bodies of sensory/afferent neurons

The Ventral Horn

• anterior grey matter section of the spinal cord, contains cell bodies of motor/efferent neurons

The Intermediolateral Horn

• present in the thoracic region of the spinal cord, mediates the entire sympathetic innervation of the body

Sympathetic Trunk, aka, the sympathetic chain

• Paired bundle of nerve fibers that run from the base of the skull to the coccyx.
• It interacts with the ventral rami of spinal nerves via grey and white communicating rami which transmit information to and from the lateral horn of the spinal cord.
• The sympathetic trunk is a fundamental part of the sympathetic division of the autonomic nervous system. It allows nerve fibers to travel to spinal nerves that are superior and inferior to the one in which they originated. 

Grey and White Rami Communicans (connecting the sympathetic trunk to spinal nerves)

• Each spinal nerve receives a branch, gray ramus communicans, from the adjacent ganglion of the sympathetic trunk. They contain unmyelinated postganglionic sympathetic fibers.
• The thoracic, and the first and second lumbar nerves each contribute a branch, white ramus communicans, to the adjoining sympathetic ganglion. They contain myelinated preganglionic sympathetic fibers. Unlike the gray rami, white rami communicans, do not extend below L2.

Spinal Segment

• a functional spinal unit (FSU) is the smallest physiological motion unit of the spine to exhibit biomechanical characteristics similar to those of the entire spine. 
• Consists of two adjacent vertebrae, the intervertebral disc and nerve exiting/entering that level of the cord and all adjoining ligaments between them and excludes other connecting tissues such as muscles. 

Segmental Innervation

• Segmental innervation refers to the distribution (innervation) of nerves within an organ or muscle. These nerves are attached to a segment of the spine.

Dermatome

• A dermatome is one pair of spinal nerves and the area of skin they innervate
• There is an overlap of dermatomes with three dermatomes supplying an area of skin
• Lack of sensation in one area can be used to diagnose injury to nerves or the spinal cord

Myotome

• a myotome is one pair of spinal nerves and the muscle or group of muscles they innervate
• Muscle weakness or paralysis can be used to diagnose nerve or spinal cord injury

Segmental Innervations of Muscles (Myotomes) of the Lower Limb  

L2: Bends (flexes) the hip

L3: Straightens (extends) the knee

L4: Dorsiflexes the foot

L5: Moves toes

S1: Plantarflexes the foot

S3-5: Innervates the bladder, bowel and sex organs, anal and other pelvic floor muscle

Myelinated Nerve Fibers

The Motor Neuron, is highlighted in "green".

**Each individual myelinated nerve fiber, is composed of intricate layers of connective tissue, the: endoneurium, perineurium and epineurium.**

Endoneurium: a layer of delicate connective tissue that encloses the myelin sheath of a nerve fiber within a fasciculus.

• Fibers are bundled together into groups known as fascicle
• It serves to support capillary vessels, arranged so as to form a net-work with elongated meshes.
• It contains fine bundles of fibrous connective tissue, primarily collagen, embedded in a matrix of ground substance.

Perineurium: connective tissue covering of fascicles making up nerves of the nervous system. 

• A smooth, transparent tubular membrane, "protective sheath", which may be easily separated from the fibers it encloses.
• It is composed of perineurial cells, which are epithelioid myofibroblasts, with myofibroblast properties: tight junctions, gap junctions, external laminae and contractility.

Epineurium: the outermost layer of dense, irregular connective tissue surrounding a peripheral nerve. 

• Encloses bundles of nerve fascicles making up a nerve, as well as the blood vessels supplying the nerve. 
• Lymphocytes and fibroblasts are also present, contributing to the production of collagen fibers, forming the backbone of the epineurium.

** When the spinal nerve exits the vertebral canal via the intervertebral foramen, two layers of the spinal meninges, the arachnoid and the dura invaginate the nerve to form a dural sleeve of connective tissue, which is the epineurium. The outer portion of the sleeve comprises the external epineurium which permits longitudinal nerve excursion and absorption of longitudinal stress. The epineurium is usually most abundant around joints, as its function is to protect the nerves from stretching, and subsequent injury. **

The Reflex Arc:

A reflex arc is the neural pathway that mediates a reflex action. Most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. 

This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs. 

There are two types of reflex arcs - autonomic reflex arc (affecting inner organs) and somatic reflex arc (affecting muscles).

• eg. Patellar Reflex: when the patellar tendon is tapped just below the knee.

The tap initiates an action potential in a specialized structure known as a muscle spindle located within the quadriceps.This action potential travels to the spinal cord, via a sensory axon which chemically communicates by releasing glutamate onto a motor nerve.The result of this motor nerve activity is contraction of the quadriceps muscle, leading to extension of the lower leg at the knee. The sensory input from the quadriceps also activates local interneurons that release the inhibitory neurotransmitter glycine onto motor neurons, blocking the innervation of the antagonistic (hamstring) muscle. The relaxation of the opposing muscle facilitates extension of the lower leg.

The Meninges

The meninges are a series of membranes which envelops the central nervous system. 

• The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system
• The meninges consist of three layers: 

Dura Mater 

• Thick, durable membrane, closest to the skull. 
• Consists of two layers, the outer periosteal layer and the inner meningeal layer. 
• Contains larger blood vessels which split into the capillaries in the pia mater. 
• Composed of dense fibrous tissue, and its inner surface is covered by flattened cells like those present on the surfaces of the pia mater and arachnoid. 
• Surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart.

Arachnoid Mater

• The middle element of the meninges
• A thin, transparent membrane, providing a cushioning effect for the central nervous system
• Composed of fibrous tissue; covered by flat cells also thought to be impermeable to fluid
• The arachnoid mater does not follow the convolutions of the surface of the brain; resembling a loosely fitting sac

Pia Mater

• Meningeal envelope which firmly adheres to the surface of the brain and spinal cord
• Follows all the minor contours of the brain (gyri and sulci)
• Very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid
• Pierced by blood vessels, which travel to the brain and spinal cord, and its capillaries are responsible for nourishing the brain

The Function(s) of the Epidural and Subarachnoid Spaces Surrounding the Spinal Cord

Subarachnoid Space

• In the central nervous system, the subarachnoid cavity (subarachnoid space) is the interval below the arachnoid membrane and above the pia mater.
• Present as an actual space in the brain and spinal cord which is filled with CSF.
• It is occupied by a spongy tissue consisting of trabeculæ (delicate connective tissue filaments that extend from the arachnoid mater and blend into the pia mater) and intercommunicating channels in which the cerebrospinal fluid is contained.

Epidural Space

• In the spine, the epidural space (extradural space/peridural space) is the outermost part of the spinal canal. 
• It is the space within the canal (formed by the surrounding vertebrae) lying outside the dura mater (which encloses the arachnoid mater, subarachnoid space, the cerebrospinal fluid, and the spinal cord). 
• The epidural space contains lymphatics, spinal nerve roots, loose fatty tissue, small arteries, and a network of large, thin-walled blood vessels called the epidural venous plexus.
• The upper limit of the epidural space is the foramen magnum, which is the point where the spine meets the base of the skull. 
• The lower limit is at the tip of the sacrum, at the sacrococcygeal membrane.
• In the head, the dura is continuous with the periosteum, the tough fibrous lining of the inside of the skull.

The Regional Vertebrae of the Lumbar Spine

**Lumbar (5), Sacral (5 fused), Coccygeal (4-5 fused; vestigial)**

Identify and Classify the Joints between Adjacent Vertebral Bodies – the Intervertebral Discs (IVDs)

• Fibrocartilaginous joints
• Vertebral bodies are separated and interconnected by IVD’s
• Classified as “amphiarthroses” (slightly movable) joints
• Consist of: an outer fibrous ring, the anulus fibrosus which surrounds an inner gel-like center, the nucleus pulposus.
• Role: shock absorbers in the spine

Structure and Function(s) of the Intervertebral Disc and its Components

 Annulus Fibrosus

• Consist of several layers (laminae) of fibrocartilage
• The collagen (type I & II) of the annulus fibrosus, attaches the disc to the bodies of adjacent vertebrae
• Type I is located towards the edge of the ring, providing greater strength; stiff laminae withstand compressive forces.

 Nucleus Pulposus

• Contains loose fibers suspended in a mucoprotein gel
• Annulus fibrosus surrounds the soft, elastic and gelatinous core (nucleus pulposus) 
• Movements of the vertebral column compress the disc by way of the nucleus pulposus and displace it in the opposite direction, allowing smooth gliding movements to occur over each vertebrae 
• Resists compression, absorbs shock and prevents friction and contact between bones

 Cartilage End-Plate

• A disc which covers the superior and inferior aspects of the vertebral body. 
• It is about 1mm thick at the periphery, and becomes thinner towards the centre. 
• Seals off the spongy, cancellous bone of the vertebral bodies, which do not have compact bone at the ends

The IVD - annulus fibrosus is highlighted "green"

The intervertebral foramen is highlighted "green"

Compare the Structure and Functions of Thoracic and Lumbar Intervertebral Discs

• Thoracic spine predominates during rotation
• Lumbar spine predominates during flexion/extension/side flexion
• Disc compressive stresses were greatest in the mid-thoracic region of the spine
• Shear stresses were highest at L5-S1

Identify the Primary (kyphotic) and Secondary (lordotic) Curvatures of the Articulated Vertebral Column and Explain their Significance

4 spinal curves; 2 primary curves: Thoracic & Sacral

**Occur late in fetal development, thus the vertebral column in a newborn is" C shaped" as only primary curves are present; accommodating for thoracic and abdominopelvic viscera**

2 secondary curves: Cervical & Lumbar 

**Do not appear until several months after birth**

aka, compensation curves, which facilitate proper alignment of the body weight through the body’s axis, shift body weight over the legs, decrease the loading on the spine.

Attenuated as infants progress through their respective stages of development, especially as they learn to walk and run; all curves are fully developed by 10yrs!! 

Identify and Classify the Zygapophyseal Joints: the Articular Surfaces, aka Facet Joints

A synovial joint between the superior articular process of one vertebra (2 facets) and the inferior articular process of the vertebra directly above it (2 facets). 

There are two facet joints in each spinal motion segment.

Concave superior facet & convex inferior facet of adjacent vertebrae forming 2 joints on either side of the vertebrae.

Joint Capsule and Synovial Membrane

• Surrounding the facet joint is a watertight sack made of soft tissue and ligaments. 
• This sack creates what is called the "joint capsule". 
• The ligaments around the facet joint combine with the synovium to form the joint capsule that is filled with fluid (synovial fluid). 

 Functions

• The biomechanical function of each pair of facet joints is to guide and limit movement of the spinal motion segment. 
• The facet joints are key players involved with spinal stabilization; as one unit with many interlocking pieces.
• Facet joints help the spine to bend, twist, and extend in different directions. Although these joints enable movement, they also restrict excessive movement such as hyperextension and hyperflexion.

Structure and Functions of the Zygapophyseal Joints in Thoracic and Lumbar Regions of the Vertebral Column

Lumbar

Zygapophysial joints prevent rotation in the transverse plane, whilst allowing sagittal rotation (flexion and extension) and a small amount of frontal rotation (lateral bending).

Thoracic

Facets are directed forward and a little medial and downward

The alignment of the facet joints of the thoracic spine allows freedom of movement during rotation and twisting.

The zygapophyseal joint, highlighted in "green".

On an Articulated Vertebral Column, Identify the Contents of the Vertebral Canal and the Intervertebral Foramen in the Thoracic and Lumbar Regions of the Vertebral Column

Vertebral Canal

• Thoracic – protects the spinal cord
• Lumbar – protects extensions of the spinal cord; the conus medullaris and cauda equina

Intervertebral Foramina

• Allows for the passage of the spinal nerve root, dorsal root ganglion, the spinal artery of the segmental artery, communicating veins between the internal and external plexuses, recurrent meningeal (sinu-vertebral) nerves, and transforaminal ligaments.

Movements (in terms of anatomical planes and axes) of the Thoracic and Lumbar Regions of the Vertebral Column

Flexion and Extension

• Lumbar spine predominates, in the frontal plane of motion, about a sagittal axis.

Lateral or side flexion to the left and right

• Lumbar spine predominates, in the frontal plane of motion, about a sagittal axis.

Rotation to the left and right (thoracic only)

• Thoracic spine predominates, in the transverse plane of motion, about the vertical axis.

Relate Thoracolumbar Movements to Pelvic Movements   

Thoracolumbar Movements: Flexion, Extension, Side Flexion, Rotation.

Pelvis Movements: Anterior tilt, posterior tilt, ipsilateral pelvic lift, contralateral pelvic drop, contralateral rotation.

**See Attached YouTubeVideo to this Lecture for Further Information on Thoracolumbar & Pelvis Movements**

Muscular Anatomy

Anatomists specifically name the skeletal muscles according to a number of criteria, based on: shape, size, location, its attachments to the skeleton (origin and insertion), and its corresponding action/function. For example for the gluteals, the size of the muscles influence their name eg. gluteus maximus (largest), gluteus minimus (smallest). Names are given to indicate length, eg brevis (short) and longus (long), and to identify the position relative to the mid-line, eg. lateralis (to the outside, away from the midline) and medialis (toward the midline). The direction of the muscle fibers and fascicles describe muscles relative to the midline, eg. rectus (straight) abdominis, or the oblique (at an angle) muscles of the abdomen. Some muscle names indicate the number of muscles in a group, eg. the quadricep group, a group of four muscles which compose the anterior thigh. Other indicate the number of origins, eg. biceps brachii (bi=indicates two origins), and triceps surae (tri=three origins). The location of a muscle's attachment, also appears in the name, the origin is always named first eg. the sternocleidomastoid (dual origin=sternum (sterno) and clavicle (cleido), and it inserts on the mastoid process of the temporal bone. When muscles are named for the movement they produce, you will find the action in the name, eg. flexor (decreases the angle at the joint), extensor (increases the angle at the joint), abductor (moves the bone away from the midline) or adductor (moves the bone towards the midline).

Muscles of the Back

**The back muscles stabilize and move the vertebral column, and are grouped according to the lengths and direction of the fascicles.**

Extrinsic Muscles (Superficial Layer)

Muscles: trapezius, latissimus dorsi, rhomboid (major and minor), and levator scapulae muscles

Innervation:  ventral rami of cervical nerves (except trapezius - accessor nerve)

Functions: moving the scapula in several directions and holding it in place 

Extrinsic Muscles (Intermediate Layer)

Muscles: serratus posterior superior and inferior muscles

Innervation: intercostal nerves

Functions: movement and stabilization of the vertebral column and thorax, help with respiration

Intrinsic Muscles (Superficial Layer)

Muscles: splenius (capitis and cervicis), spinalis, longissimus, iliocostalis muscles

Innervation: dorsal rami of spinal nerves

Functions: maintain posture and move the vertebral column

Intrinsic Muscles (Deep Layer)

Muscles: semispinalis (capitis, cervicis, thoracis), multifidus, rotatores muscles

Innervation: dorsal rami of spinal nerves

Functions: extend the vertebral column, maintain posture, help with trunk movements

Intrinsic Muscles (Deepest Layer)

Muscles: interspinales and intertransverse muscles

Innervation: dorsal rami of spinal nerves

Functions: maintain posture

Extrinsic Muscles (Superficial Layer)

Intrinsic Muscles of the Lower back (Superficial)

Important Ligaments of the Lumbar Spine

Anterior Longitudinal Ligament

• Connects the anterior surfaces of each adjacent vertebral body. Traverses all vertebral bodies and IVDs.
• Very dense, powerful ligament, limiting hyperextension of the spine.
• Restrains forward movement of one vertebrae over another.

 Posterior Longitudinal Ligament

• Parallel to anterior longitudinal
• Connects the posterior surfaces of each adjacent vertebral body
• Resists flexion of the spine

Ligamentum Flava

• Connects the laminae of each adjacent vertebrae; Runs the entire length of the spine connecting adjacent vertebral arches longitudinally.
• Attaching laminae to laminae
• Elongates with flexion
• Contracts with extension In neutral position; under constant tension, imposing a continual tension on the disc.

 Supraspinous Ligament

• Interconnects the tips of the spinous processes from C7 to the sacrum
• It is thicker and broader in the lumbar than in the thoracic region
• Resists flexion of the spine, especially when approaching end-range movements

 Interspinous Ligament

• Connects the spinous processes of adjacent vertebrae; Runs the entire length of the vertebral column
• Resists shear & forward bending of the spine
• Prevents excessive rotation

 intertransverse ligament

• Connects the transverse processes of adjacent vertebrae. runs entire length of the vertebral column
• resists lateral bending of the spine & slight rotation 

Musculature of the Thoracolumbar Spine 

Individual Muscles in the Erector Spinae Group

• iliocostalis (lumborum and thoracis)
• longissimus (thoracis)
• spinalis (thoracis)

Individual Muscles in the Transversospinalis Group

3 groups of muscles: semispinalis, multifidus, rotators. Act as assistant movers for movement of the trunk. Most important role: to stabilize the spine and help to maintain good posture.

• semispinalis: named for the areas of the body with which they are associated.
• multifidus: helps extend and laterally flex the vertebral column.
• the Erector Spinae Group:
• are the primary extensors of the vertebral column
• control: flexion, lateral flexion (side-bending), and rotation of the vertebral column, and helps maintain the lumbar curve
• composed of: iliocostalis group (laterally placed), longissimus group (intermediately placed) and the spinalis group (medially placed).
• the segmental muscle group: including interspinales and intertransversarii muscles, connect the spinous and transverse processes of each consecutive vertebra.

The Muscles of the Abdominal Wall

It is a complex job, to balance the body on two feet and walk upright. The muscles of the vertebral column, thorax, and abdominal wall extend, flex and stabilize different parts of the body's trunk. The deep muscles of the core of the body help maintain posture as well as carry out other functional, specific tasks. The brain sends out various electrical impulses to various muscle groups to control posture by alternate contraction and relaxation. This is crucial in order to prevent one muscle group from becoming fatigued too quickly. If any one muscle group fails to function optimally, body posture and functional performance will be compromised.

There are four pairs of abdominal muscles, covering the anterior and lateral abdominal region, and meet centrally, at the anterior midline. The anterolateral abdominal wall is divided into four groups: the external obliques, internal obliques, transverse abdominis and rectus abdominis.

The external oblique, closest the the surface, extends inferiorly and medially, in the direction of sliding one's fingers into pants of pockets. Perpendicular, is the intermediate internal oblique, extending superiorly and medially. The deepest muscle, transverse abdominis is arranged transversely around the abdomen, a corset. The specific arrangement in different orientations allows for various movements and rotations of the trunk. The linea alba, a white fibrous band that is made of the bilateral rectus sheaths that join at the anterior midline of the body. These enclose the rectus abdominis muscles originating at the pubic crest and symphysis, and extend the length of the body's trunk. Each muscle is segmented by three transverse bands of collagen fibers known as tendinous intersections.

The posterior abdominal wall, is formed by the lumbar vertebrae, the ilia of the hip bones, psoas major, iliacus and quadratus lumborum muscles. Central players in core stabilization and maintenance of functional performance.

Aponeuroses of the external obliques.

Aponeuroses of the external obliques.

Contents of the Abdominal Wall.

Rectus Abdominis: a paired, long flat muscle extending along the whole length of the front of the abdomen, with fibers running vertically on each side of the anterior wall; these two parallel muscles are separated by a midline band of connective tissue, the linea alba. It extends from the pubic symphysis, pubic crest and pubic tubercle inferiorly to the xiphoid process and costal cartilages of the ribs 5-7 superiorly. The rectus abdominis is contained in the rectus sheath, consisting of the aponeuroses of the lateral abdominal muscles. Tendinous intersections traverse the rectus abdominis, separating the parallel muscle into distinct muscle bellies. It is typically 10mm thick; typical volume is around 300 cubic centimetres in non-athletic individuals, or 500 cubic centimetres in athletes (eg. tennis players).

Origin: crest of the pubis

Insertion: costal cartilages of ribs 5-7, xiphoid process of the sternum.

Action: flexion of the lumbar spine; assists with respiration (forceful expiration), helps keep internal organs intact and creates intra-abdominal pressure (eg. when exercising).

External Oblique: the largest, outermost of the three flat muscles of the lateral anterior abdomen. It is a broad, thin, and irregularly quadrilateral shaped with its muscular portion occupying the side, its aponeurosis, the anterior wall. The aponeurosis forms the inguinal ligament; also contributes to the inguinal canal.

Origin: ribs 5-12

Insertion: xiphoid process, outer lip of the iliac crest, pubic crest, pubic tubercle, linea alba, inguinal ligament, anterior superior iliac spine.

Action: flexion and contralateral rotation of the torso, ipsilateral side bending; compresses the abdominal cavity, increase abdominal pressure

Internal Oblique - a muscle of the posterolateral abdominal wall, situated below the external oblique, and just above the TVA. Fibers run perpendicular to the external oblique muscle; pointing towards the midline (superiomedially).

Origin: inguinal ligament, iliac crest, lumbodorsal fascia

Insertion: linea alba, pectineal line of the pubis (via conjoint tendon) ribs 10-12.

Action: bilateral - compresses the abdomen. unilateral - ipsilateral trunk rotation; accessory muscle of respiration acting as an antagonist to the diaphragm, reducing the volume of the chest cavity during exhalation.

Transverse Abdominis: the innermost abdominal musculature, beneath the internal obliques; specifically, its upper 3/4 is positioned behind the rectus abdominis, blending with the aponeurosis of the internal oblique, the lower 1/4 is positioned infront of the rectus abdominis.

Quadratus Lumborum – a muscle of the posterior abdominal wall; depresses rib 12 (also, "fixes" rib 12 during inspiration). *Anterior to the QL are the colon, kidney, psoas minor and diaphragm; between the fascia and the muscle are the 12th thoracic, ilioinguinal and iliohypogastric nerves. The QL is a continuation of the TVA muscle.*

Psoas Major - a long fusiform muscle located on the posterior abdominal wall. It joins the iliacus to form the iliopsoas. It is divided into two segments - superficial and deep. It joins the upper body and the lower body, the axial to the appendicular skeleton, the inside to outside and back to front.

Origin: superficial - TP of T12, L1-5 & lateral aspects of the discs between these vertebral segments deep - TP of L1-L5,

Insertion: the lesser trochanter of the femur

Action: as part of the iliopsoas - flexion of the hip joint; on the lumbar spine - bends the trunk laterally, while bilateral contraction raises the trunk from its supine position. Also causes lateral rotation and weak adduction of the hip.

*tightness of the psoas major can result in spasms or lower back pain by compressing the lumbar discs. Chronic hypertonic or inflamed psoas can lead to irritation and entrapment of the ilioinguinal and iliohypogastric nerves resulting in sensation of "heat". Care should be taken when palpating or with myofascial release "foam-rolling or tennis ball releases" around the abdominal organs, especially the colon.*

Psoas Minor - **in less than 50% of individuals, the psoas major is accompanied with the psoas minor** anterior to psoas major, located in the posterior abdominal wall.

Iliacus: a flat triangular shaped muscle filling the iliac fossa. Forms the lateral portion of the iliopsoas.

Origin: upper 2/3 of the iliac fossa, anterior inferior iliac spine.

Insertion: base of the lesser trochanter of the femur

Action: flexion of the thigh and lower limb at the acetabulofemoral joint, medial rotation of the thigh.

Linea Alba 

• the midline of the abdomen; extending from the xiphoid process of the sternum to the pubic symphysis, located in the centre of the abdominal wall
• It is formed by the fusion of the aponeuroses of the abdominal muscles, separating the left and right rectus abdominis muscles.

 Inguinal Ligament

• A band running from the pubic tubercle to the anterior superior iliac spine. 
• Formed by the external abdominal oblique aponeurosis, continuous with the tensor fasciae latae (TFL) of the thigh.
• Demarcates the superior border of the femoral triangle 

 Inguinal Canal

• A passage in the anterior (toward the front of the body) abdominal wall; Larger and more prominent in men; Situated just above the medial half of the inguinal ligament.
• In males : it contains the spermatic cord and its coverings 
• In females : it contains the round ligament of the uterus and the ilioinguinal nerve
• The classic description of the contents of inguinal canal in the male are: 
• artery to vas, testicular artery, cremasteric artery, pampiniform plexus, vas deferens, genital branch of the genitofemoral nerve (L1/2)

Thoracolumbar Fascia (TLF)

• A deep investing membrane which covers the deep muscles of the back of the trunk. 
• Composed of three layers, anterior, middle, and posterior; the anterior layer is the thinnest and the posterior layer is the thickest. Two spaces are formed between these three layers of the fascia; between the anterior and middle layer lies the quadratus lumborum muscle. The erector spinae muscle is enclosed between the middle and posterior layers.

Extrinsic Muscles of the Pelvis

• Over 30 muscles in the lumbopelvic region are extrinsic to the pelvis eg. they have one of their attachments on the pelvis and the other attachment(s) on a rib and/or a thoracic or lumbar vertebrae and/or the humerus and/or the femur.
• If the pelvis is stable (fixed), then the back or upper limb or lower limb will move when a particular extrinsic muscle of the pelvis contracts. If, however, the back and/or the limbs are stable (fixed), then it is the pelvis instead that will move. This means the muscle will have reversed its action.

Specific Muscle Groups Produce or Accelerate Patterns of Movement

Anterior pelvic tilt – Rectus Abdominis, IO/EO

Posterior pelvic tilt - Erector Spinae

Pelvic lift/hitch – Ipsilateral QL, IO/EO

Pelvic drop – contralateral QL, IO/EO

Ipsilateral pelvic rotation – IO/EO

Contralateral pelvic rotation – IO/EO

*IO: internal oblique, EO: external oblique**

**The Intrinsic Muscles of the Pelvis**

Intrinsic muscles of the pelvis, are responsible for controlling the position of the organs in the pelvis, the openings of these organs to the exterior and intra-abdominal pressure.

Identify the Location of and Understand the Functions of: the Perineal Body, the Pelvic Floor Muscle Group, the Perineal Muscle Group, and the External Anal Sphincter

Perineal Body - Central tendon of perineum; a pyramidal fibromuscular mass in the middle line of the perineum at the junction between the urogenital triangle and the anal triangle . In males, it is found between the bulb of penis and the anus; in females, is found between the vagina and anus. The perineal body is essential for the integrity of the pelvic floor, particularly in females.

Pelvic Floor Muscle Group - Pelvic diaphragm; composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic floor separates the pelvic cavity above from the perineal region (including perineum) below. The right and left levator ani lie almost horizontally in the floor of the pelvis, separated by a narrow gap that transmits the urethra, vagina, and anal canal. The levator ani is usually considered in three parts: pubococcygeus, puborectalis, and iliococcygeus. The coccygeus, situated behind the levator ani and frequently tendinous as much as muscular, extends from the ischial spine to the lateral margin of the sacrum and coccyx. It is important in providing support for pelvic viscera (organs), e.g. the bladder, intestines, the uterus (in females), and in maintenance of continence as part of the urinary and anal sphincters.

The Pelvic Floor Muscle Group.

The Female Pelvic Floor, Viscera & Perineum.

The Male Pelvic Floor, Viscera & Perineum.

Perineal muscle group - Perineum is generally defined as the surface region in both males and females between the pubic symphysis and the coccyx. The perineum is the region of the body inferior to the pelvic diaphragm and between the legs. It is a diamond-shaped area on the inferior surface of the trunk which includes the anus and, in females, the vagina.

External Anal Sphincter - a flat plane of muscular fibers, elliptical in shape and intimately adherent to the integument surrounding the margin of the anus. It is, like other muscles, always in a state of tonic contraction, and having no antagonistic muscle it keeps the anal canal and orifice closed.Taking its fixed point at the coccyx, it helps to fix the central point of the perineum, so that the Bulbocavernosus may act from this fixed point. 

The Muscles of Ventilation: Identify the attachments and Deduce the Action(s) on the Thoracic Cage, and the Muscles of Inspiration

**The roles of the "respiratory" muscles, involve multiple interactions, that change rapidly. Including intricate coordination of the respiratory system (inspiratory and expiratory), corresponding postural adaptations, changes to intrathoracic cavity pressure, and orchestration of the "prime movers" (neck, upper limbs, pelvis).

Consider the effect of gravity on the thoracic cage motion (concentric, eccentric & isometric muscle activity), and the effects of elastic recoil of the lungs, and thoracic cage**

Identify the attachments and understand the action(s) on the thoracic cage, of the muscles of Inspiration

Diaphragm: is a domed shaped skeletal muscle located in the trunk, separating the thoracic and abdominal cavities; 2/3 of the tidal volume in sitting/standing postures, 3/4 of tidal volume when lying supine.

Origin: sternal-xiphoid process, costal-costal cartilages of ribs 6-10 anteriorly, ribs 11-12 laterally, lumbar-upper lumbar vertebrae & IV discs (L1-L3).

Insertion: central aponeurotic tendon

Action: contraction facilitates expansion of the thoracic cavity, increasing the volume of the cavity, decreasing the intrathoracic pressure, which allows the lungs to expand and inspiration to occur; the diaphragm descends during inspiration (12.5cm-30cm on the right side & 12cm-28cm on the left side in standing).

External, Internal and Innermost Intercostals

*the intercostals are a group of intrinsic chest wall muscles, occupying the intercostal spaces. They are active throughout respiration, maintaining the integrity of the intercostal spaces & rib cage rigidity, as well as increase the effectiveness of other muscles involved in the process.*

External Intercostals: extend from the tubercles of the ribs behind, to the cartilages of the ribs infront, where they end in thin membranes, which are continued forward towards the sternum. Fibers are directed obliquely downward and laterally on the back of the thorax, and downward, forward and medially on the front.

Origin: the lower border of ribs

Insertion: the upper border of ribs

Action: elevates the ribs, and stabilizes the chest wall during inspiration.

Internal Intercostals: are a group of skeletal muscles located between the ribs. They commence anteriorly at the sternum, i the intercostal spaces between the cartilages of the "true ribs; 1-7" and at the anterior extremities of the cartilages of the "false ribs; *8-12". They extend backwards as far as the angles of the ribs, continued to the vertebral column by thin aponeuroses (the posterior intercostal membrane). Fibers are directed obliquely, passing in the opposite direction of the external intercostal muscles. During exhalation, the interosseus portions of the internal intercostals depress and retract the ribs, compressing the thoracic cavity, expelling air. The external intercostals and the intercartilaginous sections of the internal intercostal muscles, are active during inspiration, elevating the ribs and expanding the thoracic cavity.

Origin: the superior border of ribs

Insertion: the inferior border of ribs

Action: stabilize the ribs during inspiration; forceful expiration.

Scalenes: the anterior and middle scalene lifts the first rib and bend the neck to the same side (ipsilateral lateral flexion); the posterior scalene lifts the second rib and tilt the neck on the same side. As they elevate the upper ribs, they act as accessory muscles of respiration, along with the SCMs.

Origin: cervical vertebrae (C2-7)

Insertion: 1st and 2nd ribs

Action: elevate the first and second ribs.

Serratus Posterior Superior: a thin quadrilateral muscle, positioned in the upper, posterior thorax, deep to the rhomboids. Inclining downward and lateral, inserted by four fleshy digitations into the upper borders of the 2-5th ribs.

Origin: nuchal ligament and spinous process of C7 through to T3.

Insertion: upper borders of the 2-5th ribs

Action: elevates ribs 2-5, aiding in deep inspiration.

*muscles involved in deep, forceful inspiration: sternocleidomastoid, pectoralis major, latissimus dorsi, & serratus anterior*

Identify the attachments and understand the action(s) on the thoracic cage, of the muscles of Expiration

Transversus Abdominis: the innermost abdominal musculature, beneath the internal obliques; specifically, its upper 3/4 is positioned behind the rectus abdominis, blending with the aponeurosis of the internal oblique, the lower 1/4 is positioned infront of the rectus abdominis

Origin: iliac crest, inguinal ligament, thoracolumbar fascia, costal cartilages 7-12.

Insertion: xiphoid process, linea alba, pubic crest and conjoint tendon.

Action: compressing the ribs and viscera, providing thoracic and pelvic stability. Works in tandem with the multifidus "segmental spinal stabilizer". Contractions of the TVA and other related musculature reduces vertical pressure on the IVDs by up to 40%

External and Internal Obliques of the abdomen

External Oblique: the largest and outermost of the three flat muscles of the lateral abdomen, situated on the lateral and anterior portions of the abdomen A broad thin, irregularly quadrilateral shape, with its muscular portion occupying the side, its aponeurosis the anterior wall of the abdomen

Origin: ribs 5-12

Insertion: xiphoid process, outer lip of iliac crest, pubic crest, pubic tubercle, linea alba, inguinal ligament, anterior superior iliac spine

Action: flexion, ipsilateral side-bending and contralateral rotation of the torso; pulls the chest downward, and compresses the abdominal cavity, increasing intra-abdominal pressure.

Quadratus Lumborum: a muscle of the posterior abdominal wall; depresses rib 12 (also, "fixes" rib 12 during inspiration). *Anterior to the QL are the colon, kidney, psoas minor and diaphragm; between the fascia and the muscle are the 12th thoracic, ilioinguinal and iliohypogastric nerves. The QL is a continuation of the TVA muscle.*

Origin: posterior border of the iliac crest

Insertion: inferior border of the 12th rib and L1-L4

Action: lateral flexion of the vertebral column; bilaterally - depression of the thoracic rib cage.

**the QL is a common source of lower back pain. As the QL connects the pelvis to the spine, it is capable of extending the lower back when contracting bilaterally, "picking up the slack", when the lower fibers of the erector spinae are weak or inhibited. Constant contraction while seated leads to overuse, resulting in muscular fatigue. Adhesions develop within the muscle and fascia, leading to muscle spasms. Also, when the hip abductors are weak, or inhibited (glute med/min), the TFL or QL compensate becoming the prime movers. QL will start to initiate hip abduction resulting in hip hiking during the swing phase of gait. When hip adductors are tight or hypertonic their antagonist (glute medius) may experience reciprocal inhibition, becoming weak and inhibited, causing hypertonicity of the ipsilateral QL.**

Serratus Posterior Inferior: situated at the junction of the thoracic and lumbar regions; it is an irregularly quadrilateral shape, broader than serratus posterior superior. It arises from the aponeurosis from the spinous processes of the lower two thoracic and upper two or three lumbar vertebrae, and from the supraspinal ligament. It is intimately blended with the lumbodorsal fascia and the aponeurosis of the latissimus dorsi.

Origin: spinous processes of T11-L2

Insertion: inferior borders of 9th-12th ribs.

Action: depresses the lower ribs 9-12, aiding in expiration; specifically drawing the lower ribs backward and downward assisting in rotation and extension of the trunk, as well as forced expiration.

Subcostals: located in the inferior portion of the thoracic wall; comprised of thin slips of muscle, running from the internal surface of one rib, to the second and third ribs below. Fibres run in parallel with the innermost intercostal.

Origin: inferior surface of the lower ribs, near the angle of the rib.

Insertion: Superior border of the rib 2 or 3 below.

Action: depresses the lower ribs posteriorly.

Transversus Thoracis: this group of muscles is continuous with the transversus abdominis inferiorly.

Origin: run from the posterior surface of the inferior sternum

Insertion: the internal surface of the costal cartilages 2-6.

Action: depresses costocartilages 2-6 anteriorly