Trunk/Spine

Question 1

How many vertebrae are in the vertebral column?

Answer 1

33

Question 2

Define the composition of the vertebral column

Answer 2

7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4
coccygeal vertebrae

Question 3

What does the primary curve of the spine consist of?

Answer 3

The thoracic and sacral regions

Question 4

What does the secondary curve of the spine consist of?

Answer 4

The cervical and lumbar regions

Question 5

Give the osteology of the lumbar spine

Answer 5

Anteriorly – vertebral body
* Cancellous bone
* Weightbearing
Posteriorly – neural arch
* Neural/vertebral canal/foramen
* Various bony processes for attachment/articular facets

Question 6

Describe the ‘intervertebral joint’

Answer 6

When any two vertebrae are articulated they form a triad of three joints, one is formed between the
vertebral bodies and is known as the intervertebral symphysis, the other two are the posterior
synovial joints, the zygoapophyseal (apophyseal or facet) joints. This is known as a Functional Spinal Unit.

Question 7

Describe the functions of the intervertebral discs

Answer 7

A joint could be formed simply by resting one vertebral body on another which would bear weight
and allow gliding movements. It would not however, allow the rocking movements which are
necessary for flexion, extension and side flexion of the spine to occur.
Rocking is made possible by either curving the surface of a body which would then compromise the
weight bearing stability of the joint, or by introducing a deformable tissue between the bodies, [the
intervertebral discs]. The disc not only separates the bodies therefore permitting the upper one to
tilt without coming into contact with the lower, it also transmits the weight from one vertebra to
another without collapsing.
* Enable movement while maintaining stability
* Transfer weight/absorb shock

Question 8

Describe the structure of IV discs

Answer 8

Each disc consists of a central nucleus pulposus and a peripheral annulus fibrosus. There is no clear distinction between the two parts but the peripheral part of the nucleus pulposus merges with the deeper part of the annulus fibrosus. A third component is two layers of cartilage – the vertebral end-plates, which cover the top and bottom aspects of the disc, separating and attaching the discs to the vertebral bodies.

Question 9

Describe the nucleus pulposus

Answer 9

The nucleus pulposus is a semi-fluid mass which consists of a few cartilage cells, some irregularly
arranged collagen fibres dispersed in a medium of semi-fluid ground substance. The fluid nature of
the NP allows it to be deformed under pressure, but as a fluid its volume cannot be compressed.
Therefore, if subjected to pressure from any direction, the NP will attempt to deform and transmit
this applied pressure in all directions. High levels of internal friction mean the disc excels at holding on to water. Deformable tissue able to absorb and transfer force.
With ageing, the NP is gradually invaded by fibrocytes from the annulus fibrosis, and it also loses its
water content. This results in the disc shrinking & losing height (degenerative disc disease).

Question 10

Describe the Annulus Fibrosis

Answer 10

The annulus fibrosis consists of layers of collagen fibres arranged in a highly organised manner. The
collagen fibres are located in 10-20 lamellae forming concentric rings around the NP.
The lamellae are thick in the anterior & lateral parts of the AF, but much thinner in the posterior part
(herniation of the NP is therefore more likely in the posterior part of the AF).
Within each lamellae, the collagen fibres lie parallel to each other and at approximately 65-70
degrees from the vertical. Adjacent layers lie at different inclinations to each other which greatly
improves its strength and resistance to deformation. Successive layers form an “X” arrangement which provides strength and resists rotational forces

Question 11

Describe the arrangement of collagen fibres in the annulus fibrosis

Answer 11

Collagen fibres arranged in 10-12 concentric circumferential lamellae. The orientation of fibres
alternates in successive lamellae, but their orientation with respect to the vertical is always the
same at about 65 degrees.

Question 12

Describe the structure of the vertebral end plates

Answer 12

Each end-plate is a layer of cartilage about 0.6-1mm thick, which covers the entire NP but not the entire AF. Each plate consists of a mixture of hyaline & fibrocartilage. The hyaline cartilage is most often found closest to the vertebral body and is most evident in young healthy discs, while the fibrocartilage is most often found closer to the disc itself. In older degenerate discs, the end-plates may be almost entirely fibrocartilage. The collagen fibres of the inner layers of the AF enter the end-plate and swing centrally within it forming the fibrocartilage. This arrangement means that the NP is therefore completely encased in a ‘sphere’ of collagen fibres (although superiorly and inferiorly, these collagen fibres are absorbed into the end-plates).
Where the end-plate is deficient over the peripheral part of the AF, these collagen fibres insert directly into the body of the vertebra. Because of the attachment of the AF to the end-plate, the end-plates are strongly attached to the discs. In contrast, the end-plates are only weakly attached to the vertebral bodies and can be torn from the vertebral bodies with trauma.

Question 13

Give the functions of the vertebreal end plates

Answer 13

• Resists compression from the NP during loading
• Enables transfer of nutrients from vertebral body to disc

Question 14

Describe the metabolism of the IV discs

Answer 14

Discs have a relatively low metabolic rate. They are supplied with blood vessels only in the peripheral parts and rely on diffusion from the blood vessels in the adjoining cancellous vertebral bodies for a large part of their nutrition.

Question 15

How are the IV discs adapted to weightbearing?

Answer 15

Both the AF and the NP are involved in weight bearing. The AF will resist ‘buckling’ and transmit weight because of the collagen fibres if the lamellae arrangement stays healthy (imagine a telephone directory wrapped into a cylinder shape). But it can’t transmit weight like this for long periods as the lamellae arrangement will eventually buckle under this strain. Some additional ‘bracing’ is therefore required by the NP.
As a ball of ‘fluid’, the NP reduces in height by expanding radially when weight is applied. This radial expansion exerts a pressure on the AF that stretches its collagen fibres outwards. This stretch is resisted by the tensile strength of the collagen. For any given load, an equilibrium is found where the radial pressure exerted by the NP will be exactly balanced by the tension developed within the AF.
The NP also exerts a pressure towards the end-plates but because these are firmly attached to the
vertebral bodies, they resist deformation. This pressure exerted on the end-plates acts to transmit
part of the applied load from one vertebra to the next, decreasing the load taken by the AF.
The disc acts as a ‘shock absorber’. It a force is rapidly applied, it will be diverted momentarily into
stretching the AF. This brief diversion protects the underlying vertebra by slowing the rate at which
it is transmitted.

Question 16

Describe the mechanism behind weightbearing

Answer 16

Compression raises the pressure in the NP. This is exerted radially onto the AF & tension in the AF
rises.
The tension in the collagenous fibres of the AF is exerted onto the NP preventing it from expanding radially. Pressure within the NP is then exerted onto the vertebral end-plates.
Weight is taken by the AF and NP. The radial pressure in the NP braces the AF, and the pressure on the end-plates transmits the load from one vertebra to the next.

Question 17

Describe how the IV discs are adapted to movement

Answer 17

If unrestricted by the posterior zygoapophyseal (facet) joints, any two vertebral bodies joined by an IV disc would move in any direction as the disc deforms under load.
Distraction (two vertebral bodies being pulled apart) will strain and therefore be resisted by the fibres of the AF. Anterior draw (one vertebral body sliding forward in relation to another) will be resisted by half of the fibres of the AF (those fibres in alternate lamellae layers that are orientated in the direction of the forward slide). The anterior & posterior fibres will be stretched slightly: only slightly because their orientation is not in the direction of the forward slide.
Flexion (bending forwards) will compress the anterior part of the AF and stretch the posterior part. The NP will be compressed anteriorly but still have the capacity to deform posteriorly.
Rotation (one vertebra rotates/twists on another) is resisted by half of the fibres of the AF (those fibres in alternate lamellae layers that are orientated in the direction of the rotation). As only half of the fibres are resisting the force of the movement, rotation movements are more likely to damage the AF.

Question 18

Describe the functional spinal unit

Answer 18

• Smallest individual unit of movement within the vertebral column
• Two vertebrae and intervening joints
• Anteriorly:
• 1 x secondary cartilaginous joint (symphysis)
• Posteriorly:
• 2 x simple, synovial, plane joints (Zygapophyseal/”Facet” joints)

Question 19

Describe the Zygoaphoseal (facet) joints of the spine

Answer 19

These joints are classified as synovial plane joints. The direction in which the facets face will determine the available movements in the various regions of the spine.
In the lumbar spine, the superior concave facets face medially & posteriorly, with their ‘partner’ inferior convex facets facing laterally & anteriorly.
Articular hyaline cartilage covers both the superior & inferior facets, and each facet joint is enclosed in its own capsule which is quite lax (particularly in the cervical region to allow for the gliding movements needed in this area). The capsule is obviously lined by a synovial membrane as with any other synovial joint.

Question 20

Describe the structure of the Intervertebral Foramen

Answer 20

The intervertebral foramen is bounded above and below by the pedicles of successive vertebrae, in
front by parts of the vertebral bodies of these vertebrae and the associated disc and, behind by the
articular processes and the joints between these processes.
Through the foramen passes the dorsal and ventral roots of the spinal nerves enclosed in a sleeve of
dura mater.
The foramen is oval in shape (long axis vertically disposed), with little room to spare around the
contents. Although movement changes the dimension of the foramen in the vertical plane, it is a
reduction in the transverse plane which is most likely to result in pressure effects. Therefore, any
abnormality of the zygoapophyseal joint behind, or the intervertebral joint in front, which causes a
reduction in the transverse dimension in the foramen, will result in compression effects upon the
contents.

Question 21

List the main ligaments of the lumbar spine

Answer 21

Anterior longitudinal ligament
Posterior longitudinal ligament
Ligamentum flavum
Interspinous ligament
Supraspinous ligament
Intertransverse ligament

Question 22

Describe the attachment of the Anterior longitudinal ligament

Answer 22

Attaches to the anterior part of bodies and discs from anterior tubercle of atlas to the pelvic surface of sacrum, widening as it descends. It’s between 1 and 2mm thick and consists of dense layers of collagen fibres.

Question 23

Describe the attachment of the posterior longitudinal ligament

Answer 23

Attaches to intervertebral discs and adjacent margins of vertebral bodies within the vertebral canal, extending from C2 to sacrum. It is between 1 and 1.4mm thick and consists of 2 dense layers of collagen fibres.

Question 24

Describe the attachment of the ligamentum flavum

Answer 24

Passes between both lamina of adjacent vertebrae from C1 to L5, attaching to front of lower border of the lamina above and back of the upper border of the lamina below: the medial borders meet at the root of the spine. Contains a large amount of elastic tissue.

Question 25

Describe the attachment of the interspinous ligament

Answer 25

Thin membranous bands between adjacent vertebral spines.

Question 26

Describe the attachment of the supraspinous ligament

Answer 26

Band of longitudinal fibres running over and connecting the tips of spinous processes from C7 to sacrum and is continuous with the posterior edge of the interspinous ligament.

Question 27

Describe the attachment of the intertransverse ligament

Answer 27

Pass between adjacent transverse processes, absent in the cervical region.

Question 28

Give the height of IV discs in the cervical region

Answer 28

3mm

Question 29

Give the height of IV discs in the thoracic region

Answer 29

5mm

Question 30

Give the height of IV discs in the lumbar region

Answer 30

9mm

Question 31

Describe flexion of the spine

Answer 31

Flexion occurs in all regions, most extensive in the cervical region due to the upward inclination of the superior articular facets.
The anterior part of the disc is compressed, the distance between the laminae is widened, and the inferior articular facets will glide upwards on the adjacent superior facets.
Tension increases in the posterior longitudinal ligament, ligamentum flavum, interspinous and supraspinous ligaments (ligamentum nuchae), posterior part of the intervertebral disc and the extensor muscles of the spine.

Question 32

Describe extension of the spine

Answer 32

Extension also occurs in all regions, most extensive in the cervical & lumbar regions but restricted in the thoracic region.
The posterior part of the disc is compressed with tension increasing in the anterior longitudinal ligament and approximation of the spines occurring especially in the thoracic region.

Question 33

Describe lateral flexion of the spine

Answer 33

Lateral flexion also occurs in all regions, most extensive in the cervical & lumbar regions and less so in the thoracic region. It is also accompanied by some degree of torsion.
The sides of the intervertebral discs are compressed with tension developing in the antagonistic muscles, the ligaments of the opposing side and the disc on the opposite side.

Question 34

Describe rotation of the spine

Answer 34

Rotation is restricted in the cervical region, much freer in the upper region of the thoracic spine and least in the lumbar region (the lumbar articular facets do not have a common centre of curvature to facilitate this movement).
A torsional deformity occurs in the disc with tension developing in the ligaments of both sides.

Question 35

Why is movement limited in the thoracic region of the spine?

Answer 35

Movements in the thoracic region are limited, especially in the upper part in order to minimise interference with respiratory function. The direction of the facets and thinness of the discs in the thoracic region restrict the movements possible.

Question 36

List the bones that comprise the pelvis

Answer 36

• 2 x Inominate bones (Ileum, Ischium, Pubis)
• Sacrum
• Coccyx

Question 37

List the joints of the pelvis

Answer 37

• 2 x Sacroiliac joints
• Pubic symphysis
• Lumbosacral joint (technically 3 joints – a secondary cartilaginous joint and 2x synovial plane joints…)

Question 38

Give functions of the pelvis

Answer 38

• Weightbearing: Standing - transmission of weight to the lower limbs
  Sitting – transmission of weight to the ischial tuberosities
• Extensive bony surface for muscle attachment
• Support and protection of viscera
• Bony canal for childbirth: Pelvis is one of the most sexually dimorphic parts of the human body

Question 39

Describe the superior pelvic appeture

Answer 39

• Otherwise known as pelvic brim or pelvic inlet
• Divides greater pelvis from the lesser pelvis

Question 40

Describe the inferior pelvic appeture

Answer 40

• Otherwise known as the pelvic outlet
• Provides the floor to the abdomen
• Covered by a sheet of muscles and fascia known as the pelvic floor
• Pelvic floor is a vital yet poorly understood anatomical feature

Question 41

Describe the greater pelvis

Answer 41

Otherwise known as the false pelvis
* Formed by superior aspects of the ilia and pubi above the pelvic brim and the anterior abdominal musculature

Question 42

Describe the lesser pelvis

Answer 42

Otherwise known as the true pelvis
* Pubis symphysis and superior pubis ramus anteriorly
* Sacrum and coccyx posteriorly
* Medial aspect of bodies and tuberosities of ischia and obturator fascia

Question 43

Classify the lumbosacral joint

Answer 43

• ANT: Secondary cartilaginous (between IV disc and vertebral body);
• POST: Synovial plane, simple/, multi-axial (between the articular facets).

Question 44

Describe the structure of IV discs located in the pelvis

Answer 44

Very thick, thicker anteriorly, thinner posteriorly.
Essentially a slightly modified spinal segment
Same ligamentous arrangement as a typical lumbar spinal segment

Question 45

List the ligaments found in the sacrum

Answer 45

• Anterior longitudinal ligament;
• Posterior longitudinal ligament;
• Ligamentum flavum;
• Interspinous ligament;
• Supraspinous ligament;

Question 46

List the ligaments found in the sacrum

Answer 46

• Anterior longitudinal ligament;
• Posterior longitudinal ligament;
• Ligamentum flavum;
• Interspinous ligament;
• Supraspinous ligament;

The lumbosacral joint has 2 additional supporting ligaments:
* Iliolumbar ligament:* Tip of TP L5 (L4) to inner lip iliac crest
* Lumbosacral ligament:* Lower border L5 TP to ala of sacrum

Question 47

Give functions of the iliolumbar and lumbosacral ligament

Answer 47

Both act to limit lateral flexion of the lower lumbar spine

Question 48

Classify the Sacrococcygeal Joint

Answer 48

Classification: Secondary cartilaginous. Fibrous in old age
Disc: Either fibrocartilage or ligamentous.
Ligaments: Longitudinal fibres completely surround and reinforce the joint. The sacrococcygeal joints frequently become either totally or partially obliterated with age.

Question 49

Classsify the iliosacral joint

Answer 49

Classification: Synovial, modified plane, multi-axial, simple (also considered a fibrous joint posteriorly)

Question 50

Give the articular surfaces of the iliosacral joint

Answer 50

Articular Surfaces: The auricular surface (shaped like an ear) of the sacrum is covered by hyaline cartilage, its central part being concave with raised crests peripherally. The corresponding auricular surface on the ilium is covered by fibrocartilage and its surface is raised centrally by a crest surrounded by two furrows. Both surfaces are L-shaped, being broader above and narrower below. They both show marked reciprocal irregularities (grooves so peaks and troughs correspond) which enable the bones to fit into each other thus restricting movement and contributing to the strength & stability of the joint
SIJ is capable of very slight gliding and rotation movements – typically anterior rotation (5°) and downwards glide (2mm) during weight bearing
Movement is more marked and complex during the late stages of pregnancy

Question 51

Why is the sacroiliac joint extremebly stable?

Answer 51

Form closure:
* Articular surface congruency
* “Keystone” shape of sacrum
* Self-locking joint on loading

Force closure:
* Ligaments and accessory ligaments
* Thoracolumbar fascia
* Muscle tissue crossing joint anteriorly and posteriorly

Capsule: Completely surrounds the joint.
Synovium: Lines the non-articular parts of the joint.
Ligaments: 3 important sacroiliac ligaments PLUS 2 important ‘accessory’ sacroiliac ligaments

Question 52

What are the 3 ligaments of the sacroiliac joint

Answer 52

Anterior sacroiliac ligament
Posterior sacroiliac ligament
Interosseous sacroiliac ligament

Question 53

Describe the anterior sacroiliac ligament

Answer 53

Principally resists posterior movement of the sacrum. Lies on the pelvic surface of the joint. Broad and flat, it consists of numerous thin bands stretching from the ala and pelvic surface of the sacrum to the adjoining margin of the auricular surface of the ileum. It is stronger in females.

Question 54

Describe the posterior sacroiliac ligament

Answer 54

Thicker and stronger than anterior, filling the space between the sacrum and the ileum. Several distinct bands can be identified:
* Short Posterior SIJ Ligament: Resists anterior movement of the sacrum
* Long Posterior SIJ Ligament: Principally resists downward gliding movement of the sacrum

Question 55

Describe the interosseous sacroiliac ligament

Answer 55

Principally resists separation of the sacrum and ilium. Deep, being short and thick.

Question 56

Describe the 2 accessory SI ligaments

Answer 56

a. Sacrotuberous ligament: Runs between the sacrum and ischial tuberosity
b. Sacrospinous ligament. Runs between the sacrum and spine

Question 57

Give the role of the accessory SI ligaments

Answer 57

They act to prevent forward tilting of the sacral promontory/resist anterior rotation of the sacrum

Question 58

Classify the symphsis pubis

Answer 58

Secondary cartilaginous joint

Question 59

Give the articulation of the symphsis pubis

Answer 59

Oval facets on the medial surfaces of the bodies of the pubic bones. These facets have corresponding irregularities which help the bones fit together snugly. Each surface is covered by a thin layer of hyaline cartilage. Articular surfaces are connected by a thick fibrocartilaginous interpubic disc.

Question 60

Describe the 2 ligaments of the symphsis pubis

Answer 60

There are 2 superior and inferior ligaments that strengthen the symphysis pubis, but the abdominal muscles also help to strengthen & support this joint:
a) Superior pubic ligament Strengthens the anterosuperior aspect of the joint
b) Inferior pubic ligament Passes between the inferior pubic rami rounding the subpubic angle and strengthening the joint inferiorly.

Question 61

Describe the mechanism behind weight transmission of the pelvis

Answer 61

1) The first component of force drives the sacrum downwards and backwards between the iliac bones. This force is resisted by the wedge shape of the sacrum, the sacroiliac & iliolumbar ligaments, and by the ligaments of the symphysis pubis (superior & inferior pubic ligaments). The SIJ is a ‘self-locking’ joint, so the more tightly it is held, the more weight it is able to bear.
2) The second component of force tends to push the upper end of the sacrum downwards and forwards towards the pelvic cavity. This is resisted by the interlocking nature of the middle segment of the SIJ. A rotatory movement results (the anterior segment rotating downwards while the posterior segment rotates upwards). The posterior and interosseous sacroiliac ligaments resist the anterior rotation, while the sacrotuberous and sacrospinous ligaments resist the posterior rotation

Question 62

What is the role of facet joints?

Answer 62

Facet joints prevent articular movement of L5 on S1, preventing damage to the nerve canal.

Question 63

Describe the mechanism behind stair descent
Stage 1: Right foot clear edge of step

Answer 63

Hip Flexion: Concentric hip flexor activity – iliopsoas prime mover.Abductors stabilise pelvis, reverse OI

Knee Extension-Flexion-Extension: Passive flexion initially following hip flexion followed by concentric action of quadriceps as prime mover

Foot and Ankle: toe extension; plantargrade followed by plantarflexion: Concentric followed by isometric toe extensor action (EHL/EDL as prime movers) – eccentric control of plantarflexion by dorsiflexors (tib ant as prime mover)

Question 64

Describe the mechanism behind stair descent
Stage 2: Foot in contact with floor

Answer 64

Hip: Flexion-Extension: Some eccentric control of hip flexion on impact (if step was larger) – otherwise small amount of concentric extensor activity in returning hip to neutral

Knee: Extension – Flexion - Extension: Eccentric control of knee flexion absorbing shock by knee extensors followed by concentric extension of knee by knee extensors

Foot and Ankle: Plantarflexion into plantargrade: Eccentric control of ankle movement with bodyweight by plantar flexors (gastroc/soleus as prime movers)

Question 65

Give the muscles that make up the Anterior Abdominal Wall

Answer 65

-External Oblique- strap
-Internal Oblique-strap
-Transversus Abdominis-strap
-Rectus Abdminis-saddle

Question 66

Fully classify the external oblique

Answer 66

• Name of muscle: External oblique
• Shape/Position/Special Features Outermost sheet with fibres running obliquely downwards and medially Situated on the anterolateral abdominal wall, Most superficial of the “sheet” abdominal muscles
• Origin: Outer borders lower 8 ribs and their costal cartilages
• Insertion: Outer lip anterior 2/3 ileac crest forming large aponeurosis joining that from other side at linear alba, a fibrous band running from the xiphoid process to pubic symphysis; the free lower border which forms the inguinal ligament which runs between ASIS and pubic tubercle.
• Nerve Supply and Root Value Lower 6th or 7th Thoracic and 1st Lubar Nerves
• Action(s) Controls external/lateral abdomen contraction

Question 67

Fully classify the internal oblique

Answer 67

• Name of muscle: Internal oblique
• Shape/Position/Special Features Middle layer with fibres running upwards and medially, Situated on the anterolateral abdominal wall, deep to external oblique, Middle layer of the “sheet” abdominal muscles
• Origin: Lateral 2/3 inguinal ligament, anterior 2/3 ileac crest and thoracolumbar fascia (formed by fascia covering the psoas major, quadratus lumborum and erector spinae)
• Insertion: Inferior border lower 4 ribs, forms aponeurosis, which joins its fellow at linea alba; the portion from the inguinal ligament which joins with that of the transversus abdominis forming a conjoint tendon attaching to pubic crest.
• Nerve Supply and Root Value Lower 6th or 7th Thoracic and 1st Lumbar Nerves
• Action(s) Controls internal abdomen contraction

Question 68

Fully classsify the transversus abdominis

Answer 68

• Name of muscle: Transversus abdominis
• Shape/Position/Special Features Deepest layer with fibres running transversely, Deepest of the “sheet” abdominal muscles, Fibres arranged transversely (across the abdomen)
• Origin: Lateral third iguinal ligament, anterior 2/3 inner lip iliac crest, thoracolumbar fascia, inner surface lower 6 ribs and their costal cartilages.
• Insertion: Form aponeurosis attaching to its fellow at linea alba; the portion from the inguinal ligament forms the conjoint tendon with internal oblique.
• Nerve Supply and Root Value Lower 6th or 7th Thoracic and 1st Lumbar Nerves
• Action(s) Controls deep internal abdomen contraction

Question 69

Fully classify the rectus abdominis

Answer 69

• Name of muscle: Rectus abdominis
• Shape/Position/Special Features Runs down front abdomen, enclosed in rectus sheath, 3 tendinous intersections cross muscle transversely to give the 6 pack appearance, Two, strap-like muscles on the front of the abdomen, Fibres run vertically and the muscle widens
• Origin Front of symphysis pubis and pubic crest
• Insertion Xiphoid process, costal cartilages of 5th, 6th, 7th ribs
• Nerve Supply and Root Value Lower 6th or 7th Thoracic Nerves

Question 70

Describe the action of the anterior abdominals

Answer 70

Bilaterally – Flexes the trunk and spine (posterior pelvic tilt ) produced by internal and external obliques and recti of both sides. In reversed action, i.e. e ribs fixed, the pelvis is lifted, ‘pelvic tilt’
Unilaterally – Lateral flexion to the same side. produced by external and internal obliques and rectus of the same side. In reversed action the pelvis on the same side is lifted (as in walking).
* Rotation of the trunk to the left is produced by left internal and right external obliques
* Internal Oblique and External Oblique provide pelvic stability in walking.
* Acting ‘Reverse Origin/Insertion’ they produce an upward force on the pelvis.
* This counteracts the force downwards produced by gravity and bodyweight, thereby ensuring a level pelvis

Question 71

Give functions of the abdominal muscles

Answer 71

• Assist in trunk stability and stabilise upper body on lower body
• Transmit force between upper body and lower body
• Contain and protect abdominal contents – viscera (organs)
• Raise intra-abdominal pressure (particularly Transversus due to the horizontal arrangement of the fibres)
• Forces diaphragm upwards – as in cough and sneezing
• If the diaphragm is fixed this force will result in expulsive acts of the body:
• Micturition
• Vomiting
• Defecation
• Parturition

Question 72

Give the boundaries of the abdmonen

Answer 72

• Superior: Diaphragm
• Inferior: Pelvis, Pelvic floor
• Anterolaterally: Rectus sheath, sheet musculature
• Posterior: Thoracolumbar fascia, posterior abdominal wall, spinal column

Question 73

How does pressure affect the abdomen?

Answer 73

Contraction of muscles increases force within a confined space

Question 74

Describe Aponeurosis

Answer 74

• A sheet of fibrous tissue –
• “pearly” white in colour due to dense collagen content
• Perform the same action as a tendon
• Enables a broad area of attachment between muscle and bone
• Flat – saves space and forms layers

Question 75

Describe the Linea Alba

Answer 75

• Meaning “white line”
• Fibrous structure (raphe) on the front of the body at midline between right and left
• Joins the xiphoid process to the pubic symphysis
• Acts as a point of attachment for abdominal musculature
• Transmits force across the body from one side of the abdominal musculature to the other

Question 76

Describe the strucrure of the rectus sheath

Answer 76

The rectus sheath is formed by the aponeuroses of the transverse abdominal and the external and
Muscles of the Abdominal Wall internal oblique muscles, which join centrally at the linea alba.
The arrangement of layers changes in the lower abdomen.
During late pregnancy the linea alba is stretched, if this fails to return back to original shape this is ‘diastasis recti’.

Question 77

Describe the function of the rectus sheath

Answer 77

Covers and invests rectus abdominis
Helps to transmit force from one side of the abdomen to the other
Strong, fibrous covering for rectus abdominis improves function and prevents “bowstringing” of the muscle during contraction

Question 78

Describe the arrangement of the abdominal sheath

Answer 78

Upper abdomen (Above Arcuate Line), and lower abdomen (Below Arcuate Line)
(please note that the arrangement of layers in the lower abdomen is different from the arrangement of layers in the upper abdomen).

Question 79

Describe the arcuate line of the rectus sheath

Answer 79

The arcuate line of the abdomen is a horizontal line that demarcates the lower limit of the posterior
layer of the rectus sheath. Superior to the arcuate line, the internal oblique aponeurosis splits to
envelop the rectus abdominis muscle. Inferior to the arcuate line, the internal oblique and
transversus abdominis aponeuroses merge and pass superficial (i.e. anteriorly) to the rectus muscle.

Question 80

Give the 4 muscles of the posteiror abdominal wall

Answer 80

• Psoas major;
• Psoas minor;
• Iliacus;
• Quadratus lumborum
  Positioned deep to the erector spinae (back extensor) muscles

Question 81

Fully classify the Quadratus lumborum

Answer 81

• Name of muscle: Quadratus lumborum
• Shape/Position/Special Features Large, flat, quadrilateral muscle, Fibres run upwards and medially
• Origin: Iliolumbar ligament, adjacent iliac crest
• Insertion: Medial half 12th rib, transverse processes lumbar vertebrae
• Nerve Supply and Root Value Anterior rami T12-L4
• Action(s) Both sides extend lumbar spine; one will laterally flex to same side or in reversed origin insertion.
  Unilateral – Side flexion to same side
• Unilateral (Reverse O/I) – prevention of pelvis dropping on non-standing leg
• Bilateral – Extension of lumbar spine
• Fixes origin of diaphragm during deep inspiration

Question 82

Fully classify the Psoas Minor

Answer 82

• Psoas Minor – weak muscle; often absent
• Originates from 12th Thoracic and 1st Lumbar vertebral bodies and IVD
• Forms a thin tendon to insert into the iliopubic eminence
• Anterior primary ramus L1
• Weak flexor of the Lumbar spine
  Function(s) Hold pelvis level when standing on one leg.

Question 83

Fully classify the Psoas Major

Answer 83

• Position/Shape/Special features-Anterior hip, Flattened thin ribbon
• Origin- Bodies of adjacent vertebrae and discs T12-L5; front of all lumbar transverse processes and tendinous arches over lumbar bodies.
• Insertion- With iliacus into lesser trochanter of femur.
• Nerve supply and root value- Anterior rami of L1,2,3,4
• Action(s)- Flexes hip and laterally flexes trunk
• Function(s) – Strong trunk flexer as in sitting up from lying. Action pulls lumbar spine forwards, increasing lordosis, psosas major working on one side can laterally flex the trunk to the same side.

Question 84

Fully classify the Iliacus

Answer 84

• Position/Shape/Special features- Anterior hip, triangle, flat and an exact fit of the iliac fossa
• Origin Upper and posterior two thirds of iliac fossa, ala of sacrum and anterior sacroiliac ligament
• Insertion Into lesser trochanter of femur with psosas major
• Nerve supply and root value Femoral nerve L2,3
• Action(s)- Flexes thigh at hip joint
• Function(s) Sitting up from lying

Question 85

Give the 3 muscle groups in the back

Answer 85

Superficial Group:
Muscles which attach the upper limb to the trunk (eg. trapezius and latissimus dorsi).
Intermediate Group:
Muscles such as the serratus posterior muscles [respiratory muscles which extend from the
vertebrae to the ribs].
Deep Group:
Muscles that provide stability, posture and movement to the vertebral column and head.
This deep group of muscles is also sub-divided into 3 separate layers

Question 86

Give the 3 layers of the deep group and their muscle composition

Answer 86

Superficial: Splenius & scaleni muscles

Intermediate: (very important) Erector spinae
[made up of several parts: Iliocostalis, Longissimus & Spinalis]

Deep: Semispinalis
Multifidus
Rotatores

Question 87

Which layer of the deep group is the most important?

Answer 87

The most important layer of the Deep Group is the Intermediate Layer, the erector spinae, which
consists of iliocostalis, longissimus, and spinalis. These muscles run the length of the vertebral column, It has a broad lumbosacral origin which divides into 3 columns as it extends upwards. Each of these muscles is also subdivided into 3 parts

Question 88

Describe the composition of the iliocostalis

Answer 88

(Most lateral group)
Iliocostalis lumborum: * Arises from common erector spinae origin (more lateral part)
* Fibres pass laterally and superiorly to insert, via 6 slips, into the lower 6 ribs near their angles

Iliocostalis thoracis: * Arises from the lower 6 ribs (medial to Lumborum)
* Inserts into the upper 6 ribs and C7 TP

Iliocostalis cervicis: * Arises from the upper 6 ribs (medial to Thoracis)
* Inserts into the posterior tubercles of TP’s C4-7

Question 89

Describe the composition of the longissimus

Answer 89

Longissimuss thoracis: * Arises from common erector spinae origin (more medial part) and the TP’s of L1-L5
* Fibres pass superiorly to insert via two sets of slips to the TP’s all 12 thoracic vertebrae and adjacent regions of the lower 10 ribs

Longissimus cervicis: * Arises from the TP’s T1-6 (medial to Thoracis)
* Inserts to the posterior tubercles of TP’s C2-6

Longissimus capitis: * Arises from the TP’s T1-5 (in common with Cervicis) and articular processes C4-7
* Inserts into posterior aspect of the mastoid process

Question 90

Describe the composition of the spinalis

Answer 90

(Most medial group)
Spinalis thoracis: * Arises from the spinous processes of T11-L2
* Fibres pass superiorly to insert into the spinous processes of T1-6

Spinalis cervicis: * Arises from the lower part of the nuchal ligament, spinous process C7(T1-2)
* Inserts into the spinous processes of C2(3-4)

Spinalis capitis: * Indistinct from semispinalis capitis

Question 91

Describe the origin of errector spinae

Answer 91

Spinous processes and supraspinous ligaments T11-L5, posterior and sacral crests, sacrotuberous ligament and posterior part ileac crest

Question 92

Give the nerve supply of the errector spinae

Answer 92

Adjacent posterior rami

Question 93

Give the action of the errector spinae

Answer 93

All 3 columns work together on both sides to extend the lumbar, thoracic, cervical spines and head on neck: working on one side only, they produce lateral flexion and rotation to same side.
* Bilateral: Extension of relevant Lumbar, Thoracic or Cervical spine
* Unilateral: Lateral Flexion of relevant Lumbar, Thoracic or Cervical Spine to the same side. Rotation of relevant Thoracic or Cervical Spine to the same side
* All movements depend upon the relevant muscle attachment and location

Question 94

Give the function of the errector spinae

Answer 94

Maintain upright human posture
Standing on one leg erector spinae on the non-weight-bearing side helps prevent the pelvis dropping.
Assists forced inspiration

Question 95

Describe the compostion of deep layer of back muscles

Answer 95

The deep layer of the deep group is made up of several short muscles (semispinalis, multifidus and rotatores) which are important in the segmental stability of the vertebral column. They attach between spinal levels, and across multiple spinal levels, they essentially act as “extensible ligaments” which control movement.

Question 96

Describe the role of deep layer back muscles

Answer 96

They also act to produce movement, particularly movement of rotation in the thoracic region

Question 97

Fully classify the multifidus

Answer 97

Origin: Posterior sacrum, mammillary processes lumbar vertebrae, trasmverse processes thoracic vertebrae, articular processes lower 5 cervical vertebrae.
Insertion: Muscle fibres arranged in 3 layers passing upwards/medially to attach to all spinous processes (L5-C1).
Nerve supply: Posterior rami adjacent spinal nerves
* Fibres pass upwards and medially* Muscle lies in a layered arrangement:
* Deep fibres (1 spinal level above)
* Intermediate fibres (2-3 spinal levels above)
* Superficial fibres (3-4 spinal levels above)
Action: Rotates, extends and laterally flexes spine
Function: Spinal stabiliser, atrophy can cause lower back pain.

Question 98

Give the 3 parts of the semispinallis

Answer 98

Thoracis:* Arises from TP’s T6-10
* Inserts into spinous processes C6-T2
Cervicis:* Arises from TP’s T1-6
* Inserts into spinous processes C2-6
Capitis:* Arises from TP’s C4-T6
*Attaches between the superior and inferior nuchal lines at the base of the skull
* Spinalis Capitis either blends with, or is distinct medially from, Semispinalis Capitis

Question 99

Give the action of the semispinallis

Answer 99

Action: * Bilateral – extension of the spine
* Unilateral – rotation of the spine to opposite side

Question 100

Fully classify the rotatores

Answer 100

: Rotate spine and are best developed in thoracic region;
Origin: Arise from the TP of one vertebrae
Insertion: into the lamina of the vertebrae above
* Some fibres cover 2 spinal levels
Actions:
* Multifidus: Rotation of the spine to opposite side, in addition to extension and lateral flexion
* Rotatores: Thoracic spine rotation to opposite side
* Both are best regarded as stabilising muscles – acting as extensile spinal ligaments to control movement

Question 101

Give the nerve origin of the multifidus, rotatores and semispinallis

Answer 101

All deep layer muscles are supplied by the adjacent posterior rami

Question 102

Describe the thoracolumbar fascia

Answer 102

• Dense, triple-layered sheet of fibrous, connective tissue
• Roughly diamond shaped
• Acts as a protective membrane between the 12th rib and pelvis (protecting contents of the posterior abdomen, such as the kidneys)
• Acts as a broad, communal tendon for muscle attachment
• Separates muscles into “compartments”, transmitting load and enhancing contraction
• Plays an important role in stabilisation and force transmission through the lower back