PBL Flashcards
What are the general functions of the vertebral column?
Support, movement and protection.
How many vertebrae does a typical human have?
33
How many cervical vertebrae are there?
7
How many thoracic vertebrae are there?
12
How many lumbar vertebrae are there?
5
How many sacral vertebrae are there?
5 (fused)
How many coccygeal vertebrae are there?
4 (fused)
List the components of a typical vertebra. (9)
- vertebral body (anterior)
- vertebral arch
- vertebral foramen
- pedicle
- lamina
- transverse processes
- spinous process
- superior/inferior articular processes
- superior/inferior vertebral notches
What is the purpose of the superior/inferior vertebral notches?
They form intervertebral foramen which spinal nerves can then pass through.
Why is the vertebral column longer than the spinal cord?
It grows faster than the spinal cord
At what level does the spinal cord typically end?
L1/L2
Why are there 8 cervical spinal nerves but only 7 cervical vertebrae?
C1 nerve exits above the C1 vertebra.
What is the cauda equina?
The spinal nerves that arise from the spinal cord bundled together.
What are the movements of the vertebral column?
- flexion
- extension
- lateral flexion
- rotation
Which section of the vertebral column is the most mobile?
Cervical
Which section of the vertebral column is least mobile for flexion/extension/lateral bending?
Thoracic
Which section of the vertebral column has the least rotation?
Lumbar
List the degrees of movement in the cervical region.
- flexion: 65
- extension: 40
- lateral flexion: 35
- rotation: 50
List the degrees of movement in the thoracic region.
- flexion: 35
- extension: 25
- lateral flexion: 20
- rotation: 35
List the degrees of movement in the lumbar region.
- flexion: 50
- extension: 35
- lateral flexion: 20
- rotation: 5
What are the two types of vertebral joints?
Zygapophyseal (facet) and symphysis (IV discs).
What type of joint are the Zygapophyseal joints and where are they found?
Synovial plane joints found between superior and inferior articular processes.
What type of joint are the symphysis joints of the vertebral column?
Secondary cartilaginous/fibrocartilaginous found as intervertebral discs between vertebral bodies.
How many joints does a typical vertebra have?
6 (4 zygapophyseal and 2 IVDs)
List the functions of the IV discs.
- provide stability and flexibility
- pressure regulation
- shock absorption
Describe the annulus fibrosus.
- high tensile strength
- fibrous sheath on outer surface (collagen layers in rings)
- fibrocartilage inner zone
Describe the nucleus pulposus.
- high resilience
- gelatinous structure
- 80-85% water
Why do humans lose about 1% of their height during the day?
When humans are upright there is more pressure on the IV discs than when lying down. This means that there is a slow release of water from the nucleus pulposus causing the IV disc to become thinner, hence some height is lost.
What is a ‘slipped disc’?
A prolapse or hernia of the IV disc.
- a tear in the annulus fibrosus can cause the nucleus pulposus to protrude and this can impinge on the spinal cord or nerves.
What is the atlanto-occipital joint?
The synovial joint between C1 and occipital bone - allows for nodding the heading
What is the atlanto-axial joint?
Synovial joint between C1 and C2 - allows for shaking the head ‘no’
How is C1 different from a typical vertebra?
No body, facet and ligament to for dens of C2
How is C2 different from a typical vertebra?
It has the den or odontoid process to articulate with C1 and allow for rotation of the head.
List the ligaments of the spine.
- anterior longitudinal ligament
- posterior longitudinal ligament
- Supraspinous ligament
- nuchal ligament
- ligamentum flavum
- interspinous/intertransverse ligaments
Describe the anterior longitudinal ligament of the spine.
- runs from base of skull to anterior surface of the sacrum
- attaches to anterior surface of vertebral bodies and IVDs
- prevents hyperextension
Describe the posterior longitudinal ligament of the spine.
- runs from C2 to posterior surface of sacrum
- attaches to posterior surface of vertebral bodies and IVDs
- lines the anterior surface of the vertebra canal
- weakly resists hyperflexion
Describe the Supraspinous ligament of the spine.
- runs from C7 to sacrum
- connects the tips of the spinous processes
- cord like
Describe the nuchal ligament of the spine.
- runs from base of the skull to C7
- strong fibroelastic tissue
- supports the head on the neck
- provides attachment for muscles e.g. trapezius
Describe the ligamentum flava of the spine.
- pass between laminae of vertebrae
- forms part of vertebral canal
- resists separation of verts during flexion
Describe the interspinous ligaments of the spine.
Attaches between spinous processes
Describe the intertransverse ligaments of the spine.
Attaches between transverse processes.
What are the superficial extrinsic back muscles?
- trapezius
- latissimus dorsi
- levator scapulae
- rhomboid major and minor
Describe the trapezius muscle of the back.
Origin: skull, nuchal ligament, spinous processes of C7-T12
Insertion: clavicle, acromion, scapula spine
Innervation: motor from accessory nerve and proprioception from spinal nerves C3/C4
Actions: upper fibres elevate scapula and rotate it during abduction of the arm; middle fibres retract the scapula and lower fibres pull scapula inferiorly.
Describe latissimus dorsi.
Origin: spinous processes of T6-T12, thoracolumbar fascia, iliac crest and inferior three ribs
Insertion: all fibres converge to a tendon that attaches to intertubercular sulcus of the humerus
Innervation: thoracodorsal nerve
Actions: extends, adducts and medially rotates the upper limb
Describe levator scapulae.
Origin: transverse processes of C1-C4
Insertion: medial border of scapula
Innervation: dorsal scapular nerve
Actions: elevates the scapula
Describe rhomboid major.
Origin: spinous processes of T2-T5
Insertion: medial border of scapula between scapula spine and inferior angle
Innervation: dorsal scapular nerve
Actions: retracts and rotates scapula
Describe rhomboid minor.
Origin: spinous processes of C7-T1
Insertion: medial border of scapula at level of scapula spine
Innervation: dorsal scapular nerve
Actions: retracts and rotates scapula
What are the common features of the intrinsic back muscles?
- all act directly on spine
- embryonically develop in the back
- all supplied by posterior rami of spinal nerves
- help to maintain posture and control movement of vertebrae
Describe the thoracolumbar fascia.
- covers deep muscles of the back
- critical to organisation and integrity of the region
- lat dorsi and trapezius attached to it
What muscles make up the superficial layer of intrinsic back muscles?
Splenius cervicis and splenius capitis
Describe splenius cervicis.
Origin: nuchal ligament and spinous processes of C7-T6
Insertion: tubercles of transverse processes of C1-C3/C4
Innervation: posterior rami of spinal nerves
Actions: unilaterally - flex the neck and rotate head to side of active muscles; bilaterally - extend the head and neck
Describe splenius capitis.
Origin: nuchal ligament and spinous processes of C7-T6
Insertion: mastoid process of temporal bone and superior nuchal line of occipital bone
Innervation: posterior rami of spinal nerves
Actions: unilaterally - flex the neck and rotate head to side of active muscles; bilaterally - extend the head and neck
Which muscles make up the intermediate layer of intrinsic back muscles?
The erector spinae muscles - iliocostalis, longissimus and spinalis.
Describe the iliocostalis erector spinae muscle.
Origin: broad tendon attached to sacrum, spinous processes of L and T lower verts and iliac crest
Insertion: angles of ribs and cervical transverse processes
Innervation: posterior rami of spinal nerves
Actions: bilaterally - extend vertebral column and head
Describe the longissimus erector spinae muscle.
Origin: broad tendon attached to sacrum, spinous processes of L and T lower verts and iliac crest
Insertion: T and C transverse processes and mastoid process
Innervation: posterior rami of spinal nerves
Actions: unilaterally - laterally flex vertebral column
Describe the spinalis erector spinae muscle.
Origin: broad tendon attached to sacrum, spinous processes of L and T lower verts and iliac crest
Insertion: thoracic spinous processes and skull
Innervation: posterior rami of spinal nerves
Actions: unilaterally - laterally flex vertebral column
Which muscles make up the deep layer of intrinsic back muscles?
- The transversospinalis muscles - semispinalis, multifidus and rotatores
- levatores costarum
- interspinales and intertransversarii
Describe the semispinalis transversospinalis muscle.
Origin: transverse processes of C4-T12
Insertion: occipital bone and spinous processes of T and C verts
Innervation: posterior rami of spinal nerves
Actions: extends head, C and T regions of vert column and rotates them contralaterally
Describe the multifidus transversospinalis muscle.
Origin: posterior sacrum, posterior iliac spine of ilium, aponeurosis of erector spinae, sacrilege-iliac ligaments, mamillary processes of L verts, transverse processes of T1-T3, articular processes of C4-C7
Insertion: spinous processes, thickest in lumbar region
Innervation: posterior rami of spinal nerves
Actions: stabilises vertebrae during local movements of vertebral column
Describe the rotatores transversospinalis muscle.
Origin: transverse processes, best developed in thoracic region
Insertion: junction of lamina and transverse process or spinous process of superior verts
Innervation: posterior rami of spinal nerves
Actions: stabilise vertebrae and assist with local extension and rotatory movements vert column
List some common cause of back pain.
- muscle spasms, strained muscles, poor posture
- sprained ligaments
- nerve pain (slipped disc or sciatica)
- arthritis
- kidney stones
What are the natural curvatures of the spine?
2 primary curvatures = kyphosis in thoracic and sacrococcygeal regions
2 secondary curvatures = lordosis in cervical and lumbar regions
List some abnormal curvatures of the spine.
- excessive kyphosis
- excessive lordosis
- scoliosis
What is the filum terminale?
Anchors the spinal cord to the bottom of the vertebral column
List some of the biological roles of calcium. (5)
- Muscle contraction
- Intracellular messenger
- Nerve excitability
- Blood coagulation
- Cofactor for enzymes of intermediary metabolism
List some dietary sources of calcium.
- Milk, cheese and other dairy foods
- Curly kale
- Soya drinks with added calcium
- Bread and anything made with fortified flour
- Fish where you eat the bones e.g. sardines/pilchards
List the main organs involved in calcium homeostasis.
- Kidney
- Gut
- Bone
- Parathyroid glands (calcium sensing receptors)
What are the two hormones involved in calcium homeostasis?
Parathyroid hormone and calcitriol
What is the daily dietary intake of calcium?
25 mmol per day
Where does calcium absorption mainly occur?
In the duodenum and jejunum
How is calcium absorbed in the duodenum and jejunum?
- Via a cell mediated active transport pathway which is controlled by 1.25 DHCC
- Via passive diffusion which depends on luminal Ca concentration and is unaffected by 1.25 DHCC
In which areas of the kidney does parathyroid hormone increase re-absorption of calcium?
Cortical thick ascending loop of Henle and distal convoluted tubule.
How is secretion of parathyroid hormone regulated?
By free calcium levels which are detected by the calcium sensing receptors in the parathyroid gland and renal tubules.
Summarise the actions of PTH in regards to calcium levels.
- Stimulates renal tubular calcium reabsorption
- Promotes bone resorption
- Stimulates formation of 1,25. DHCC in kidney which then enhances calcium absorption from the gut
How is calcium distributed throughout the body?
- 99% contained in mineral phase of bone as a component of hydroxyapatite
- Remaining 1% split between extracellular ionised Ca and intracellular cytosolic Ca
How is calcium distributed in serum?
- Approx 47% is free/unbound/ionised
- Approx 47% is bound to proteins, mainly albumin
- Approx 6% complexed to anion e.g. phosphate
List the steps involved in bone repair after a fracture.
- Fracture haematoma formation
- Fibrocartilaginous callous formation
- Bony callous formation
- Bone remodelling
Discuss the fracture haematoma formation of bone repair.
- When a bone breaks, nearby blood vessels are damaged
- Blood haemorrhages in to the surrounding area
- Within 6-8 hours, a pool of blood develops called a fracture haematoma
- Formation of the haematoma causes vessels to constrict and stop any further bleeding
- Blood cells degenerate and eventually die off leading to inflammation and swelling
Describe what happens during fibrocartilaginous callous formation.
- Fibroblasts invade the fracture site from the periosteum
- They replicate, producing collagen and forming granulation tissue
- Formation of granulation tissue leads to development of the fibrocartilaginous callous
- Callous is made up of collagen fibres and cartilage
- Callous does provide any structural rigidity but helps to bridge the two end of bone together
Describe what happens during bony callous formation.
- Osteogenic cells develop into osteoblasts and migrate towards the fibrocartilaginous callous
- Spongy bone is laid down along the marrow cavity on the inside of the bone and along the outside surfaces
- This joins the broken ends of bone together
- Over time the areas of fibrocartilage are converted in to spongy bone thus creating the bony callous
Briefly describe what happens during bone remodelling after a fracture.
- Osteoclast activity increases to remove any dead or damaged cells around the bony callous
- Spongy bone is replaced by compact bone along the outside surface
List the five stages of bone remodelling.
- Bone resting
- Bone resorption
- Bone reversal
- Bone formation
- Bone mineralisation
What happens during the bone resting phase of bone remodelling?
- Activation of quiescent or resting bone
- Inactive osteoblast cells (bone lining cells) cover all available surfaces of the resting bone
- They active to initiate the next step
What happens during the bone resorption phase of bone remodelling?
- Involves loss of minerals and collagen fibres by action of osteoclasts
- Osteoclast precursor cells are recruited to the activated surface and fuse to form mature, multinucleated osteoclasts
- Osteoclasts resorb a discrete amount of bone
- Ruffled border of osteoclasts secretes lysosomal enzymes and hydrochloric acid
- Lysosomal enzymes digest matrix
- HCl breaks down calcium salts into a soluble form
- Dissolved minerals and digested matrix move through osteoclast and in to blood via interstitial fluid
What happens during the bone reversal phase of bone remodelling?
- Mononuclear cells deposit a proteoglycan to form a cement line
- Mononuclear cells release growth factors that initiate bone formation phase
- Osteoprogenitor cells are recruited and differentiate/proliferate in to mature osteoblasts
What happens during the bone formation phase of bone remodelling?
- New bone formed in a process called bone deposition
- Osteoid is added to newly formed bone cavity by action of osteoblasts
- Osteoid laid down between unmineralised area of bone matrix and old mineralised bone
What happens during the bone mineralisation phase of bone remodelling?
- Osteoblasts embed in osteoid and become osteocytes
- Layers of osteoid build up and then mineralise
- Osteoblasts left lying on surface of bone become quiescent/resting until next bone remodelling
List some factors which may enhance bone healing after a fracture.
- Young age
- Growth hormone enhances healing
- Metaphysical fractures heal faster than diaphyseal
List some factors which may retard bone healing.
- Advancing age
- Poor nutrition/vitamin deficiency
- Chronic illness e.g. diabetes
- Atherosclerosis
- Corticosteroids
- NSAIDs
- Smoking
- Degree of bone loss
- Degree of immobilisation
- Disruption of vascular supply
Define osteoporosis.
‘A disease characterised by low bone mass and micro-architectural deterioration of bone tissue, leading to enhanced bone fragility and an increase in fracture risk.’
What type of scan is used to determine bone mineral density?
A dual X-ray (DXA)
What t-score would indicate osteoperosis?
Less than or equal to -2.5. If one or more fractures are also noted then it is ‘established’ osteoporosis.
Briefly describe the pathogenesis of osteoporosis.
Increased bone breakdown by osteoclasts and decreased bone formation by osteoblasts, leading to loss of bone mass.
List some causes of osteoporosis.
- Ageing
- Oestrogen deficiency
- Glucocorticoids
How can an oestrogen deficiency contribute to osteoporosis?
- increased number of remodelling units
- Premature arrest of osteoblastic synthetic activity
- Perforation of trabeculae
- Loss of resistance to fracture
How can glucocorticoids lead to osteoporosis?
- Induce a high turnover state initially
- Increased fracture risk evident within 3 months of starting therapy
- Prolonged use leads to reduced turnover state but with a net loss due to reduced synthesis
How does ageing contribute to osteoporosis?
- Increased turnover at bone/vascular interface within cortical bone
- Results in structural weakness
List some major risk factors for osteoporotic fractures.
- Age > 65
- Early menopause
- Glucocorticoid steroid use
- Family history
- Hypogonadism
List some minor risk factors for osteoporotic fractures.
- Smoking
- Long term heparin therapy
- Low dietary calcium intake
- Rheumatoid arthritis
- Excessive alcohol intake
What are the clinical features of osteoporosis?
- Vertebral fractures
- Colles’ fractures (wrist)
- Hip fractures (proximal femur)
Describe the investigations which would be used to diagnose osteoporosis.
- DXA scan to measure bone mineral density - usually of lumbar spine and proximal femur
- Look for any associated diseases and risk factors
- Vertebral fracture assessment (DXA scan that also looks for indications of fractures)
List some non-pharmacological approaches to preventing osteoporosis. (6)
- Adequate dietary calcium intake
- Stop smoking
- Reduce alcohol consumption
- Avoid/reduce dose of sedative drugs
- Ensure those at risk have suitable environment e.g. handrails, good lighting
- Hip protectors for those prone to falls
List some pharmacological approaches to preventing osteoporosis.
- Bisphosphonates
- Hormone replacement therapy
- Selective oestrogen receptor modulators
- Teriparatide
- Denusomab
How do bisphosphonates work?
They inhibit osteoclastic bone resorption by increasing osteoclast death and decreasing osteoclast precursors and activity.
List some examples of bisphosphonates.
- Alendronate
- Risedronate
- Zoledronate
How does hormone replacement therapy help to prevent osteoporosis?
It reduces the increased bone turnover that would be induced by oestrogen deficiency.
How do selective oestrogen receptor modulators prevent osteoporosis?
They decrease the activity of osteoblasts and so reduce bone resorption
What is an example of a SERM?
Raloxifene
How does Teriparatide prevent osteoporosis?
It mimics the action of PTH on calcium and phosphate homeostasis so helps to increased bone mineral density
How does Denosumab prevent osteoporosis?
It prevents RANKL from activating RANK on the surface of osteoclasts and their precursors so reduces bone resorption
How is osteoperosis treated?
Treatment is based on healing and preventing broken bones so fracture prevention and increasing bone strength.
