Lecture 15: Back Musculature

Question 1

What are the 4 curvatures of the spine and how does it change from embryo to adult

Answer 1

Cervical, Thoracic, Lumbar, Sacral coccygeal curvature. In an embryo you mostly have anteriorly concave cervical and sacral curvature but as you lift your head and start to be bipedal there is added weight that is counteracted by the other 2 anteriorly convex curvatures.

Question 2

What are 3 abnormal curvatures

Answer 2

Scoliosis : lateral curvature towards the stronger dominant muscle side

Kyphosis: forward curve of cervical and upper thoracic region due to osteoporosis and back muscle distrophy

Lordosis: Pronounced curve in the lumbar region due to increased frontal load during pregnancy

Question 3

Compare the size of the vertebrae of cervical, thoracic and lumbar region

Answer 3

In cervical it takes up the posterior 3rd to counterbalance the increased weight on the front of the skull

In the thoracic its in the posterior 1/4 to make room for lungs and heart

In the lumbar it is bearing most of the weight takes up posterior 1/2 -> more central

Question 4

Describe the structure of a typical vertebra-> how do the vertebral body and arch relate and what are the things sticking out

Answer 4

The main vertebral body is kind of semicircle with the flat surface facing posteriorly. Attached over this is the verterbal arch, creating the vertebral foramen - a space for the spinal cord.
This arch has a spinous process pointing at the peak of the arch with two transverse processes towards the left and right directions.
There are two arches going straight through the legs of the arch, forming the superior and inferior articular processes

Question 5

What are the pedicles and the laminae on the typical vertebra

Answer 5

The posterior half of the arch (separated by the articulate processes) on the side of the spinous process are the laminae
whereas the anterior half is the pedicles

Question 6

What is the function of the transverse processes on the spinal cord

Answer 6

Like spars on a yacht mast they allow space for muscle and ligament attachment

Question 7

What is the function of the articular processes

Answer 7

The inferior Apro of one fits with superior Apro of the vertebra below it. Where the articular facets join, a pivot point is created where the muscle attached to the spinous process can generate a force up to help lessen the downward compressive force on the spinal column.

They are also notched to create gaps for nerves to leave the spinal column

Question 8

How does the spine stay flexible but stable

Answer 8

More stable at the bottom than the top. The segment create a flexible column that with the help of muscles and ligaments able to change lengths can redistribute the weight with changes to the position of the leg so as to keep the centre of gravity more central

Question 9

What is a linkage between vertebra and what is its components

Answer 9

Intervertebral disc made of anulus fibrosis around a nucleus pulposus

Question 10

Describe the structure and function of anulus fibrosis

Answer 10

A layered rings of fibrous connective tissue. Between each layer the elastic collagen fibres are orientated at different angles. Outer layers vertical to stop flexion and extensionn and inner layers to stop rotation

Question 11

Describe the structure and function of nucleus pulposus

Answer 11

It is a ball made of hydrophilic matrix (water, proteoglycans and type 2 collagen) which acts as a pivot point between 2 vertebrae and resists compressive force, evenly distributing it to the anulus fibrosis

Question 12

What happens in a herniated disc

Answer 12

This is where the anulus fibrosis can get distorted/ teared and the nucleus pulposus is pushed to the weaker point of the vertebra (not supported by the ligament) and this can put pressure on the spinal nerves causing severe back pain/ numbness

Question 13

What are the 5 ligaments we need to learn in order from ventral to dorsal

Answer 13

Anterior longitud, posterior longitud, Ligamentum flavum, Interspinous and supraspinous ligament

Question 14

Where is the anterior longitudinal ligament and what does it do

Answer 14

On the front of the vertebral bodies it stops over extension

Question 15

Where is the posterior longitudinal ligament and what does it do

Answer 15

It is on the back of vertebral body (floor of the house) and helps to stop over extension

Question 16

Where is the supraspinous ligament and what does it do

Answer 16

It is from the tip of each spinous process to each other which prevents overflexion

Question 17

Where is the ligamentum flavum ligament and what does it do

Answer 17

It is lining the inside of the lamina and between lamina it protects spinal cord and nerves while containing elastic fibres for pivotting of that joint

Question 18

Where is the interspinous ligament and what does it do

Answer 18

It connects the medial and lateral surfaces of the spinous process together .

Question 19

What are the 4 superficial back muscles

Answer 19

Latissimus dorsi, Trapezius, Rhomboids major and minor and

Levator Scapulae

Question 20

What are the 2 intermediate back muscles . Are they extrinsic or intrinsic?

Answer 20

Serratus posterior superior and Serratus posterior inferior. The are extinsic- belonging to respiratory

Question 21

What are the shape and functions of the 2 intermediate back muscles

Answer 21

Serratus posterior superior is near the neck area and it goes from higher on the spine to lower near the shoulder. Its function is to elevate the ribs for inspiration

Serratus posterior inferior goes from halfway of the torso back up to the ribs so its function is to depress the ribs for expiration

Question 22

What are the 4 deep muscles from medial to lateral. Extrinsic or Intrinsic

Answer 22

Spinalis, Multifidus, Longissimus, Iliocostalis. Intrinsic which position the spine.

Question 23

Where does the spinalis attach to

Answer 23

Spinalis attaches to the spinous processes

Question 24

Where does the iliocostalis go between

Answer 24

From Iliac crest and sacrum to the angles of the ribs

Question 25

Where does the longissimus go

Answer 25

Along the transverse processes

Question 26

Where does the multifidis go

Answer 26

It goes from the transverse processes of lower vertebra to those of higher vertebra.

Question 27

How flexion and extension, lateral flexion and rotation change over Cervical, Thoracic and Lumbar regions

Answer 27

Degree of flexion and extension doesn’t change over the 3 types (40’)
However lateral flexion is most in cervical (40) and decreases in the thoracic region, maintained in the lumbar region. Rotation decreases per segment across region but overall it is maintained from 40’ until lumbar which has less than 5’.

Question 28

What causes the difference of rotation between thoracic and lumbar vertebra- centre of pivot

Answer 28

The flat articular facets of superior thoracic vertebrae face directly osteriorly with the inferior vertebrae anteriorly. This places the centre of pivot in the vertebral body. Whereas for lumbar the larger superior articular processes face inwards towards the midline of the spinous process, with the inferior articulate processes facing laterally and this shifts the centre of pivot onto the spinous process

Question 29

What are the 3 branches of neural supply coming off the spinal cord and what do they innervate

Answer 29

From the spinal cord are the ventral and dorsal rami.
Ventral rami- going to periphery carrying nerves from the root ganglions
Dorsal rami-innervating the muscle and skin of the back

Gray ramus communicans going back to innervate the spinal cord itself (joints, meningeal tissue, periosteum..) and to the sympathetic chain (non segmental nerves) which go to innervate a thin layer of anulus fibrosis

Question 30

Where is there no innervation on the spinal cord

Answer 30

The nucleus pulposus and much of the deeper layers of the anulus fibrosis

Question 31

Why is it hard to localise back pain

Answer 31

As one of the 3 branches of one spinal nerve can enter the sympathetic chain which goes to different segments there can overlap between the info its receiving therefore hard to pinpoint where exactly the pain is

Question 32

What is the blood supply of the segments of the spinal cord

Answer 32

Segmental spinal vessels from the aorta
Vertebral = cervical
Posterior intercostal artery= thoracic region
Lumbar vessels= Lumbar

Question 33

Describe the 5 branches of the aorta artery that bring blood supply to the back/spinal cord

Answer 33

The main branch supplies periphery,
The posterior branch supplies the back muscles and skin and
There is a small branch that goes back into the intevertebral foramen and supplies everything in the vertebral canal.
There are also para and pre-vertebral anastomoses that link up the vessels like the sympathetic chain

Question 34

Compare the vascular supply of the vertebral body to the intervertebral disc

Answer 34

Good supply for the vertebral body as it is bone but only thin peripheral supply to the anulus fibrosis. All the central structure of the intervertebral disc rely on diffusion but its ok because they aren’t too metabolically active.

Question 35

Compare the level of metabolites and nutrients from the centre of intevertebral disc to periphery

Answer 35

Centre: High metabolites, low nutrients
Periphery: Low metabolites, high nutrients