Anatomy: Back, Vertebral Column, and Spinal Cord

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Anatomy (DONE)

Three roles of the vertebral column

Protects the spinal cord
Supports the skull and upper limbs
Transmits weight to the lower limbs through the pelvis

Vertebral column at birth and through development

Starts with 33 vertebrae
5 sacral and 4 coccygeal fuse

Number of adult vertebrae and divisions

26 total- 7 cervical, 12 thoracic, 5 lumbar, 1 sacrum, 1 coccyx

Intervertebral discs

Discs of fibrocartilage between vertebrae. Divided into inner nucleus pulposus and a tough outer annulus fibrosis.

Vertebral foramina

collectively form vertebral canal for spinal cord

Cerebrospinal fluid

bathes the brain and spinal cord and acts as a shock absorber that protects the central nervous system

Intervertebral foramina

openings found between adjacent vertebrae where spinal nerves pass through and connect to the spinal cord

How many pairs of spinal nerves are there passing through the intervertebral foramina

31 pairs

Primary curvatures of the spine

Thoracic and sacral

Develop during fetal period and are anteriorly concave.

Secondary curvatures of the spine

Cervical and lumbar

Anteriorly convex

Kyphosis

- "Hunchback"- Abnormal increase in the posterior curvature of the spine.
- Most common is postural kyphosis
- May be caused by resorption of the anterior parts of the thoracic vertebral bodies from osteoporosis- increases anterior concavity

Lordosis

An abnormal increase in the anterior curvature of the spine
- May be caused by the weakening of the anterior abdominal wall musculature as a result of weight gain or pregnancy.
- May result in lower back pain.

Scoliosis

- An abnormal increase in lateral curvature that may be caused by an absent half of a vertebra or a wedge shaped vertebra, or by asymmetric weakness in the back musculature.

Anterior Longitudinal Ligament location

-runs superior to inferior in front of the vertebral bodies connecting adjacent vertebrae.
-runs from the occipital bone of the skull to the sacrum.

Anterior Longitudinal Ligament role

-helps to secure intervertabal disks and prevents hyperextension of the vertebral column (whiplash is cervical hyperextension of the anterior longitudinal ligament)

Posterior Longitudinal Ligament location

- on the posterior aspect of vertebral bodies (inside the vertebral canal)
- runs from the axis (C2) to the sacrum, but is continuous with the tectorial membrane which is attached to the occipital bone superiorly

Posterior Longitudinal Ligament role

- helps prevent the hyper-flexion of the vertebral column and posterior protrusion (herniation) of the discs

Supraspinous Ligaments

attach the tips of adjacent vertebral spines
in the cervical region, the supraspinous and interspinous ligaments are greatly thickened to form the ligamentum nuchae

ligamentum flavum

yellow in color and connects the lamina of adjacent vertebrae

Interspinous ligaments

connect adjacent vertebral spines

How are the vertebral column, nerve cords, and spinal cord supplied with blood?

Spinal arteries that take origin from various arteries in the cervical region, thoracic region, lumbar region, and sacral region

Clinically, what may occur when blood supply to the spinal cord is disrupted?

Paresis (weakness) and paralysis

The veins form complicated _______ that extend along the vertebral column from the skull to the coccyx.

plexuses

Names of the external and internal vein congregations around the vertebral column

External vertebral venous plexus
Internal vertebral venous plexus

Vertebral venous plexuses communicate superiorly through the _____ with ______ and drain into _______.

foramen magnum
venous sinuses in the cranial cavity
vertebral, intercostal, lumbar, and lateral sacral veins

Three muscle layers of the back

Superficial (extrinsic)
Intermediate (extrinsic)
Deep (intrinsic)

Superficial muscles of the back

Trapezius
Latissimus dorsi
Levator scapulae
Rhomboids major and minor

Connections made by the superficial back muscles

All connected to the shoulder girdle and thereby attach the appendicular and axial skeletons

Intermediate muscles of the back

Serratus posterior superior
Serratus posterior inferior

The intermediate back muscles are innervated by ____ ____ ____ and are used during ______.

ventral primary rami
respiration

Prominent deep muscles of the back

Erector spinae group:
- spinalis (medially)
- longissimus (intermediately)
- iliocostalis (laterally)

Common origin of the erector spinae group (deep back muscles)

broad tendon attached inferiorly to the posterior aspect of the iliac crest, the posterior sacrum, sacroiliac ligaments, and the lumbar and sacral spinous processes

Role of the erector spinae group and results of injury to group

- they are the chief extenders of the vertebral column
- injury is the cause of "back strain" due to excessive extension or lateral rotation of the ertebral column

What provides motor innervation to all deep back muscles?

Dorsal rami of spinal nerves

Deep muscles apart from the erector spinae group

splenious- cervicus and capitus grouped
semispinalis- capitus, cervicis, and thoracis grouped
multifidus
rotatores

Auscultory triangle
- what it is
- boundaries
- floor

- site on the back where breath sounds may be most easily heard with a stethoscope
- boundaries are the latissimus dorsi, the trapizius, and the medial border of the scapula
- the rhomboid major forms the floor

Lumbar triangle (of petit)
- what it is
- boundaries

- the site where pus may emerge from the abdominal wall
- boundaries are the latissimus dorsi, the posterior border of the external oblique muscle of the abdomen, and the iliac crest

The spinal cord begins superiorly at the _____ ______ where it is continuous with the ____ _____ of the brain

foramen magnum
medula oblangata

In adults, the spinal cord terminates inferiorly at the level of the __ or __ vertebra

L1 or L2, thus occupying the upper two thirds of the vertebral canal

The spinal cord is surrounded by three meninges:

the dura mater
the anachnoid mater
pia mater

Enlargements of the spinal column

cervical and lumbar enlargements
this is where it gives origin to the brachial and lumbar plexuses, respectively

Conus medullaris

where the spinal cord tapers to a conical tip, which is at or inferior to the level of the first lumbar vertebrae (L1)

Filum terminale

an extension of the pia mater that anchors the spinal cord to the coccyx by connecting the conus medullaris to the posterior surface of the coccyx.

__ pairs of spinal nerves are attached to the spinal cord by ____ and ____ roots

31
ventral
dorsal

Ventral roots are ____ while dorsal roots are _____
Each dorsal root possesses a dorsal root _____

motor
sensory
ganglion

Cauda equina

collection of spinal nerves below the end of the spinal cord, around the filium terminale

As spinal nerve roots pass through the intervertebral foramina, the unite to form the _____ _____

spinal nerves

After emerging form the intervertebral foramen, each spinal nerve divides into a large _____ _____ and a smaller ____ _____

ventral ramus
dorsal ramus

Both the ventral ramus and the dorsal ramus contain ____ and ____ fibers

motor and sensory

Dura mater
- what it is
- superior and inferior sections

external membrane of dense fibrous tissue that encloses the spinal cord and cauda equina
- superiorly continuous with the meningeal layer of dura covering the brain
- inferiorly, the dura ends on the filum terminale at the level of the lower border of the second sacral vertebra

Arachnoid mater

delicate, impermeable membrane that lies within the dura and outside the pia

How is the arachnoid mater sepereated from the pia mater?

a wide space called the subarachnoid space that is filled with CSF

What is the arachnoid mater continuous with superiorly?

continuous through the foramen magnum with the arachnoid covering the brain

Where does the arachnoid mater end inferiorly?

Ends on the filum terminale at the level of the lower border of the second sacral vertebra. Continues along the spinal nerve roots, forming small, lateral extensions of the subarachnoid space

What is the pia mater?

a vascular membrane that closely covers the spinal cord and extends along each nerve root as far as the spinal nerve

What are the denticulate ligaments?

Thickenings of the pia mater, 21 attachments per side, that attach it to the arachnoid and dura

Spina bifida

(bifidus-cleft in two parts) Congenital defect that leads to vertebral laminae failing to fuse. Presents as lack of spinous process and is commonly seen at the lower L or sacral vertebral levels.

Spina bifida occulta

(bifidus-cleft in two, cultus-to cover/hide) Most common and least severe form of spina bifida without protrusion of the spinal cord or meninges. Asymptomatic, may be marked by a tuft of hair over defect.

Spina bifida cystica

(bifidus-cleft in two, kystis-bladder) Congenital defect in which the back portion of one or more vertebrae is not closed normally and a cyst protrudes through the opening in the back. May result in hydrocephalus and neurological defects

How is spina bifida cystica diagnosed?

In utero on the basis of elevated levels of alpha-fetoprotein after aminocentesis, and by ultrasound imaging.

Spina bifida cystica with meningocele

(menix-membrane, kele-tumor) Congenital defect in which the back portion of one or more vertebrae is not closed normally and a cyst protrudes that is lined with the meninges and contains CSF.

Spina bifida cystica with meningomyecele

(myelos-marrow) Congenital defect in which the back portion of one or more vertebrae is not closed normally and the membranes and spinal cord protrude though the defect.

What effect of spina bifida cystica with meningomyelocele have on the lumbrosacral spinal nerves?

Displacement of the spinal cord stretches the lumbrosacral spinal nerves and results in bladdar, bowel, or lower limb weakness.

Where is the needle passed in a spinal tap, and how is this area identified?

The fourth lumbar spine is identified by passing an imaginary line between the highest points on the iliac crests
Needle passes through the skin, fascia, interspinous ligament, ligamentum flavum, fatty tissue and the internal vertebral venous plexus, dura mater, and arachnoid mater. Ends in the subarachnoid space.

What is herniation of the Nucleus Pulposus?

Sudden increase in compression leads to rupture of the annulus fibrosus. Nucleus herniates posteriorly where it presses on the spinal nerve roots, spinal nerve, or spinal cord.

What is the clinical significance of the vertebral venous plexus?

provides a pathway for the spread of malignant disease from the pelvis to the skull

Spinal cord ischemia

Minor damage to the arterial blood supply to the spine can lead to ischemia because the anterior and posterior spinal arteries have small diameters, and reinforcing segmental arteries vary in number and size

Spondylitis

Inflammation of one or more of the veterbrae
Can result in additional bone growth
Patients exhibit ankylosis (joint stiffening)

Spondylolysis

loosening of the firm attachment of contiguous vertebrae

Spondylolisthesis

forward movement of the body of the lower vertebrae
Oblique xray shows decapitated dog

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