Human Anatomy Exam 1

purposes of the skin

-shield against heat, light, injury, infection

-regulates temperature

-stores water and fat (protection from cold)

-provides sensation (pain, temperature, touch)

layers of the epidermis

- stratum (mature keratinocytes, protective layer, layer of dead keratinocytes at very top)

- squamous cell layer (immature keratinocytes)

- basal layer (where cell division and replication occurs, keratinocytes start here and move upwards over ~1 month)

contents of the dermis

blood vessels, lymphatic structures, hair follicles, sweat glands, nerves, fibroblasts, pressure sensors

keratinocyte replication v. fibroblast replication

keratinocytes make up the epidermis, produced in the basal layer, move up through the squamous layer, end in the stratum before dying and flaking off the skin

fibroblasts make up the dermis, after one cell is produced, the original mother cell undergoes apoptosis and is reabsorbed into the bloodstream

subcutaneous layer

deepest skin layer - connection to fascial plane, network of collagen, fat layer aids in warmth and shock absorption

functions of the spine

- provides a point of attachment for muscles (produce movement) and ligaments (check movement)

- protect spinal cord and nerves (CNS cannot regenerate)

- support head and viscera (maintain even horizon for vestibular function and vision)

- act as linkage for upper and lower segments in functional activity (locomotion, posture)

primary curves (of the spine)

thoracic and sacral kyphosis - follows natural concavity of the fetal position in utero

secondary curves (of the spine)

cervical and lumbar lordosis - "acquired" convexity based on movement (baby looks up to feed, baby learns to roll and crawl)

segments of the spinal column

33 total - 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4 coccygeal

degrees of movement at the spine

extension/hyperextension - 25 degrees

flexion - 80 degrees

lateral flexion - 25 degrees

transverse foramina

found on cervical vertebrae only, vertebral artery exits through C2-C6

bifurcated spinous processes

landmark of only C2-C6, allows for attachment of nuchal ligament and increased blood flow

uncovertebral joint

space between the uncinate process and adjacent vertebral body, found between the lower 5 cervical vertebrae

uncus (uncinate process)

process on cervical vertebrae only - lip on either side of the vertebral body

functions of uncovertebral joints

- guides cervical flexion and extension

- reduce cervical lateral rotation

- prevent posterior translation of neighboring vertebra

- reinforce posterolateral aspect of IV disc (as they are small in this region)

costovertebral joint

superior and inferior costal facets of the body of thoracic vertebrae articulation with the head of the rib (A on image)

costotransverse joint

costal facet on transverse process of thoracic vertebrae articulation with the tubercle of the rib (B on image)

mamillary processes

processes specific to lumbar vertebrae, found on the posterior aspect of the superior articular process

accessory processes

processes specific to lumbar vertebrae, found in between transverse and spinous processes on the lamina

cervical superior facet orientation

Back, Up, Medial (45 degree angle)

small masses allow gliding between vertebrae - works with uncinate process to limit rotation and guide lateral flexion without injury

thoracic superior facet orientation

Back, Up, Lateral (60 degree angle)

allows significant rotation between vertebrae because ribs create a bony stop that limits rotation

lumbar superior facet orientation

Back, Medial (90 degree angle)

limited rotation between vertebrae - receives pressure from head/arms/trunk etc, maintain linkage to lower body (rotation while walking)

intervertebral joints

articulations between vertebral bodies - cartilaginous symphyses with a fibrocartilage intervertebral disc in between

zygapophyseal joints

articulations between superior and inferior articular facets - gliding type synovial joints, very small movement at each joint has cumulative effect

approximation

facets move closer together during extension/hyperextension (IV foramen decreases in size)

distraction

facets move farther apart during flexion (IV foramen increases in size)

spinal tropisms

57% of people have flat/normal facets, 31% have asymmetric (restricts movement on one side), 12% have half-moon shape (restricts some movement)

anterior longitudinal ligament

runs down anterior vertebral bodies, checks extension/hyperextension

posterior longitudinal ligament

runs down posterior vertebral bodies/anterior vertebral canal, checks flexion, becomes tectorial membrane superiorly

ligamentum flavum

connects lamina of adjacent vertebrae, protects spinal cord (primary action), also checks flexion and rotation (accessory)

interspinous ligaments

connects spinous processes, checks rotation (primary) and flexion (accessory)

intertransverse ligaments

connects transverse processes, checks rotation (primary) and flexion (accessory)

supraspinous ligaments

connects tips of spinous processes, checks flexion (primary ligament for this check), becomes nuchal ligament superiorly (A in image)

tectorial membrane

continuation of PLL, anchors to anterior rim of foramen magnum (A on image)

cruciform ligament

transverse portion anchors to lateral margins of the vertebral canal of C1, touching posterior dens of C2, superior and inferior portions anchor to the anterior rim of the foramen magnum and posterior rim of the dens of C2 - important in counteracting anterior translation of C1 relative to C2

apical ligament

ligament deep to tectorial membrane and superior portion of the cruciform ligament - anchors to the foramen magnum and dens of C2

alar ligament

ligament deep to tectorial membrane and cruciform ligament - anchors from the lateral margins of the dens to the foramen magnum - helps to guide cervical rotation

annulus fibrosis

outer layer of the intervertebral disc, composed of lamellae (thin fibrocartilage rings), has blood supply and is slightly neural

main functions: cushion shearing and torsional forces, will resist distraction of adjacent vertebral sections, keeps nucleus pulposus in place

nucleus pulposus

inner gelatinous part of the intervertebral disc, avascular and aneural

main functions: resist compressive forces, gives disc its height

(if decrease in fluid --> loss of column height --> facet approximation --> decrease in IV disc foramen size --> pathology (ex. osteoarthritis/pinched nerves) --> pain and limited function

if it leaks, it leaks in the posterolateral direction (least ligamentous support)

vertebral endplates

connecting mechanism of intervertebral disc to bone, interwoven into disc (part of disc, not subchondral bone) - contains hyaline and fibrocartilage covering the top and bottom aspects of the disc, central portion of the plate has a permeable membrane

functions: maintain connections of intervertebral joints, prevent nucleus pulposus from bulging, absorb pressure

cervical and lumbar enlargements

2 sites on the spinal cord where nerves serving the upper and lower limbs emerge

conus medullaris

tapering/end of the spinal cord at the level of L1

cauda equina

long roots through the vertebral canal starting at the level of L2 - develops throughout the lumbar and sacral spine, exits out their foramina to the pelvis, perineum, and LE (stays within the meninges)

meninges

three protective membranes (dura, arachnoid, pia) that surround the brain and spinal cord - protection of neural fluid, CSF flows within

dorsal root ganglion (DRG)

contains cell bodies of sensory neurons - where CNS starts and PNS ends, meninges stop there

denticulate ligaments

anchors within the spinal cord that connect pia/arachnoid mater - centers the spinal cord (side-to-side stability) om the vertebral canal and helps CSF flow

anchors of the spinal cord

brain (superior), filum terminale (inferior), denticulate ligaments (lateral)

filum terminale

fibrous, blue-white colored, extension of the conus medullaris that adheres to the 1st coccygeal segment - needed for orientation of the cauda equina (connective in nature, not neural)

L4

level of the iliac crest, useful for spinal tap (extracting CSF) or lumbar puncture (injection of local anesthetic to do a nerve block)

medial branch of posterior rami

innervates multifidus, zygapophyseal joints, and the periosteum of the vertebral arch

recurrent meningeal/sinuvertebral nerve

nerve with 2-4 filaments on each side of vertebra at all levels and ascending/descending branches - arises from ventral rami and sympathetic trunk (grey communicantes), starts right after meninges end - recurs and goes back into the vertebral column, collects data from the annulus fibrosus before going back in, important in referred pain and occipital headaches

ascending and descending branches of the recurrent meningeal nerve

innervates the posterior longitudinal ligament, posterior aspect of superior disk, anterior aspect of dura, spinal canal vessels

branches of posterior rami

lateral branch, intermediate branch, medial branch

branches of anterior ramus

recurrent meningeal/sinuvertebral nerve, skeletal branch, muscular branch

sensory information

travels through the dorsal root to the posterior spinal cord

motor information

travels from the anterior spinal cord through the ventral root

white matter v. grey matter

white matter "travels" (myelinated) and grey matter "thinks" (unmyelinated)

path of vertebral artery

paired arteries that arise from the subclavian artery, ascend through the transverse processes of C2-C6 (not C7 - transverse foramen not big enough), pass behind lateral mass of C1 and enters the dura behind the occipital condyle, ascend through the foramen magnum and join to form the basilar artery

portions of vertebral artery

proximal (initial branch off subclavian - prone to compression due to longus colli and scalene muscles), transverse (C2-C6 levels - prone to compression from osteophytes and subluxed facet joints), suboccipital (groove for vertebral artery of C1 - prone to compression from cervical rotation), intracranial (join to basilar artery - prone to plaque and stenosis)

arteries of the spinal cord

2 posterior spinal arteries, 1 anterior spinal artery, radicular artery, arterial vasocorona

arterial vasocorona

artery functioning as an anastomosis (interconnection of vessels), surrounding the whole spinal cord - fed by radicular artery, connects to anterior and posterior spinal arteries - allows for collateral circulation

radicular artery

spinal cord arteries that go interior - fed by various arteries in each region (cervical, thoracic, abdomen, pelvis)

batson venous complex

spinal veins - internal connects from cord and canal, also has an external segment

occipital triangle

boundaries: rectus capitis posterior major, obliquus capitis inferior, obliquus capitis superior

contents: vertebral artery (laying down in C1), suboccipital nerve

stages of development in utero

pre-embryonic (conception-week 2), embryonic (week 2-8), fetal (week 8-birth)

pre-embryonic stage

conception-week 2 - zygote (30 hours) --> moves from uterine tube to cavity, continued cell division to form blastomere --> morula phase (3 days) --> blastocyst (4 days) --> inner layer of blastocyst turns into bilaminar embryonic disk (day 6-14) --> embryonic disk forms ectoderm, endoderm, yolk sac, and amnion

bilaminar embryonic disk

stage at day 6-14, the blastocyst embeds into the uterine wall, ectoderm and endoderm form, yolk sac (that will provide nourishment) and amnion (where growth will occur) form, the disk is located between these two spaces

zygote

fertilized egg, forms 30 hours after fertilization

blastomere

a cell formed by cleavage of a fertilized ovum, made of 4 cells

morula

A solid ball of cells that makes up an embryo, made up of 12+ cells - forms 3 days after fertilization

blastocyst

stage 4 days after fertilization, outer layer will develop into the placenta, inner layer will develop into bilaminar embryonic disk

embryonic stage

week 2-8 - gastrulation (days 14-21), somite formation (day 18), neurulation (begins day 19), neural tube development, differentiation into mantle and marginal layer (day 26), neuropores close (day 28-30), mantle layer divides into association plate and motor place, neural crest divides into sensory and motor nerves, intervertebral disc development (around 4th week), formation of limb buds (high level of development weeks 5-8)

gastrulation

days 14-21 - blastocyst-->gastrula - mesoderm is formed

endoderm

innermost germ layer, develops day 6-14 - develops into liver, pancreas, respiratory system cells - much of the viscera

ectoderm

outermost germ layer - develops day 6-14 - develops into sensory organs, epidermis, nervous system

develops into the neural plate around day 16 --> neural groove around day 18

mesoderm

middle germ layer - develops day 14-21 - develops into dermis, muscle, skeleton, excretory organs, and eventually the circulatory system (including the heart)

neurulation

begins on day 19, formation of the CNS begins - neural groove--> neural tube

neural tube

forms when the folds of the neural groove touch, starts cervical and closes rostro-caudal to eventually become the spinal cord - adjacent somites on either side will eventually turn into vertebra and spinal segments

neural crest

remaining ectoderm cells adjacent to the neural tube --> divides and develops into the dorsal root ganglion + forms peripheral sensory nerves/forms motor connections

neuropores

spots where the neural tube does not close right away - superior closes on day 27 (or 28) and becomes the forebrain, inferior closes on day 30 and becomes the conus medullaris

neural tube differentiation

day 26 - two rings of cells form the mantle layer and marginal layer --> the mantle layer further divides into the association plate and motor plate

association plate

dorsal portion of the mantle layer of the neural tube - when neural crest divides, it projects cells through, they stretch out and become DRG/peripheral sensory nerves in the adult system

motor plate

ventral portion of the mantle layer of the neural tube - when neural crest divides, it projects cells through, they stretch and form motor connections

mantle layer

inner portion of the developing neural tube (day 26) --> develops into gray matter

marginal layer

outer portion of the developing neural tube (day 26) --> develops into white matter

somites

specialized portions of mesoderm that begin to form on day 18, line up against the neural tube, rostro-caudal development - include the sclerotome, myotome, and dermatome

sclerotome

anteromedial portion of the somite --> develops into skull and bones of the vertebral column

myotome

posteromedial portion of the somite --> develops into skeletal muscle

dermatome

lateral portion of the somite --> develops into the dermis

limb buds

Bumps of tissues developed from the mesoderm layer that will form into limbs - embryo resembles human form by week 8

intervertebral disc development

4th week (pre-cartilaginous or mesenchymal stage) - start seeing development of spinal segments - neural tube squeezed to form disc, neural tube surrounded by embryonic cartilage, collagen fibers form the annulus fibrosus (by 10th week - totally developed by 5-6 months)

spinal cord growth

during fetal stage (weeks 8-12) - vertebra and spinal cord grow together at first, but then the column begins to grow faster than the cord - at week 12, the cauda equina forms because the cord cannot keep up but nerves continue to grow

formation of the brain

begins on day 28 with the closure of the superior neuropore - three main vesicles become the forebrain, midbrain, and hindbrain

failure of rostral closure

when the superior neuropore does not close by day 28 - anencephaly can occur (skull not fully formed, no forebrain, no cortex --> stillborn)

failure of caudal closure

when the inferior neuropore does not close by day 30 - spina bifida

spina bifida

most common congenital spinal defect (1:2,500 live births), lack of development of neural arch/axis (severity ranges from occulta --> cystica (meningocele) --> cystica (menigomyelocele)

spina bifida occulta

most common and least severe form of spina bifida, usually at L5-S1, may be asymptomatic, tuft of hair, no functional issues

spina bifida cystica

severe spina bifida

meningocele - meningeal cyst, may be covered by skin or thin membrane, sac contains only meninges, normal physical life possible with treatment

meningomyelocele - contains meninges and spinal cord, spinal nerves in cyst, much more severe - loss of sensory and motor function, cannot maintain CSF pressure causing hydrocephalus, pt typically wheelchair bound

clinical significance of the multifidus

critical for long term stability of the spine - this muscle has highest % of type 1 fibers out of all back muscles (high aerobic capacity) - immobility --> atrophy --> inability to do long bouts of standing/walking/working --> low back pain

congenital malformations (of the back)

5% of the population has some sort of lumbar tropism/abnormality, can be an occult condition - examples include lumbarization and sacralization, where L5 or S1 migrates up or down (can be asymptomatic or cause pain, depending on the situation)