Anatomy 337 Modules 3-6

The spinal cord ends inferiorly at the ______.

conus medularis

gray commissure

a bundle of nerve fibers that surrounds the central canal of the spinal cord and connects the anterior and dorsal horns of gray matter in each half of the cord.

Central canal

a fluid-filled channel in the center of the spinal cord

Anterior spinal artery

supplies anterior 2/3 of spinal cord

Columns of spinal cord

white matter separated into columns that extend along entire length of spinal cord

Descending Pathways

Corticospinal Tract - axons are largely contralateral - cross the midline of the brain stem or spinal cord and synapse on opposite side of body (decussates in brain stem) - right motor cortex control left side of muscles - descends from cortex via deep white matter of brain - passes through brain stem - fibers decussate - descend spinal cord via lateral column - synapse w/ lower motor neuron in ventral horn at level necessary - the axon projects from ventral root to the skeletal muscle the upper motor neuron cell body in in the primary motor cortex of the frontal lobe lower motor neuron is in the ventral horn

Once the first blood vessels grow into the shaft of the cartilage in a developing bone, which of the following occurs first?

Osteoblasts migrate into the cartilage with the capillaries and begin to lay down bone.

perforating canals

Perpendicular to the central canal Carry blood vessels into bone and marrow structures through which blood vessels enter and exit the compact bone shaft at right angle

Which of the following is produced in the red bone marrow?

blood cells

Which sensory receptors respond to continuous deep pressure and skin distortion?

bulbous (Ruffini) corpuscles

filum terminale

fibrous extension of the pia mater; anchors the spinal cord to the coccyx

interstitial lamellae

fill spaces between osteons remains of old osteons that broke down as bone grew and remodeled itself

bursae

flattened fibrous sacs lined w/synovial membrane, contains synovial fluid; common where things rub together fluid filled pockets in connective tissue

CSF drip

spinal cord ends around L1, so you should insert needle between L3/4 or L4/5 because it is unlikely you would hit the spinal cord - the spinal nerves in the cauda equina move of the way of the needle

osteogenic cells

stem cells that differentiate into osteoblasts which differentiate into osteocytes

hinge synovial joint

Uniaxial Convex cylindar in one bone applied to corresponding concavity in other EX - elbow, ankle, knee

pivot synovial joint

Uniaxial; Rotation around single axis Cylinderical bony process rotating within circle of bone and ligament

intramembranous ossification

bone develops from a fibrous membrane process by which bone forms directly from mesenchymal tissue Produces flat bones of skull and clavicle Development of ossification center - ossification - development of trabeculae - development of periosteum

central canal (haversian canal)

canal that houses blood vessels located at the center of the osteon contains blood vessels and nerves Contains one or more blood vessels that carry blood to and from the osteon; run parallel to the surface of bone.

Medullary cavity

cavity within the shaft of the long bones filled with bone marrow

Horns of Spinal cord

dorsal horn: - responsible for sensory processing ventral horn: - send out motor signals to skeletal muscles - contain cell bodies of outgoing somatic lower motor neurons Lateral horn: - ONLY IN THORACIC REGION - central component of the sympathetic division of the autonomic nervous system

The cell bodies of sensory neurons traveling from the periphery to the spinal cord are located in the

dorsal root ganglion

Diarthrosis

freely movable joint

Ampiarthrosis

slightly movable joint

posterior spinal artery

-two arteries -supplies posterior 1/3 of cord -located in the postero-lateral fissure

31 spinal nerves

8 cervical (C1-C8) - C1-C7 emerge superior to the vertebra of the same # - C8 emerges betw C7 and T1 12 thoracic (T1-T12) - emerge inferior to corresponding vertebra 5 lumbar (L1-L5) - emerge inferior to corresponding vertebra 5 sacral (S1-S5) 1 coccygeal

periosteum

A dense fibrous membrane covering the surface of bones (except at their extremities) and serving as an attachment for tendons and muscles.

Spinal Cord Pathways

Ascending Pathways - cary sensory info up to brain - dorsal columns utilize this pathways Descending Pathways - carry motor commands from brain Anterior and lateral columns are composed of different groups of axons of both pathways Pathways decussate - cross to the contralateral side - right side of brain processes incoming/outgoing info from left side of body and vice versus All pathways are composed of paired tracts - one on left and one on right - mirror images of each other

condylar synovial joint

Biaxial Modified ball-socket Articular surfaces are ellipsoid instead of spherical range of motion limited almost to hinge and restricts rotation EX - atlantooccipital, radiocarpal (wrist), TMJ (multiaxial)

saddle synovial joint

Biaxial 2 saddle-shaped articulating surfaces oriented at right angles to eachother EX - thumb (carpometacarpal pollicis), intercarpal, sternoclavicular

Lamellated (Pacinian) corpuscles

Common in deeper subcutaneous tissues, tendons and ligaments Detect heavy/deep pressure and vibrations

Ascending Sensory Pathways

Dorsal Column Medial Lemniscus (DCML) Pathway - fine, discriminative touch and light pressure - periphery receptor - spinal nerve - dorsal root- dorsal root ganglion (cell body)- dorsal column - ascend to brainstem - synapse - decussate Anterolateral System (ALS) - 2 tracts - carries sensory info about pain, temperature, crude touch - spinal nerve - dorsal root - dorsal root ganglion (cell body) - dorsal horn - synapse - decussates in spinal cord at level they entered - axons ascend - travels up anteriolateral column of spinal cord Spinocerebellar - proprioception - divided into dorsal (info about individual muscles) and ventral (position of limbs) portions - axons enter spinal nerve and dorsal root - cell body in dorsal root ganglion - enters dorsal horn - synapses - 1 portion decussates and the other stays ipsolateral - ascends to brainstem - decussated path crosses back over - ALL INFORMATION IS PROCESSED IN THE IPSOLATERAL CEREBELLUM

endochondral ossification

Formation of bone collar around hyaline cartilage model Formation of the primary ossification center in the diaphysis Invasion of internal cavities by periosteal bud and spongy bone formation Formation of medullary cavity and appearance of secondary ossification centers Ossification of epiphyses; hyaline cartilage remains at epiphyseal plates and articular cartilages

Internal Anatomy of Spinal Cord

Gray matter: dendrites - Horns (dorsal/posterior, lateral, ventral/anterior) White matter: myelinated axons - Columns (posterior/dorsal, lateral, anterior/ventral) Central canal

Canaliculi

Hairlike canals that connect lacunae to each other and the central canal

compact bone

Hard, dense bone tissue that is beneath the outer membrane of a bone the surface of all bones are covered by a layer of this

hyaline cartilage

Most common type of cartilage; it is found on the ends of long bones, ribs, and nose

ball and socket synovial joint

Multiaxial; allows wide range of motion in all directions EX - shoulder and hip joints

Nerves of the spinal cord

Nerves enter and exit the spinal cord Ventral roots - contain axons of EFFERENT MOTOR neurons - extend from ventral horns - carry info from spinal cord to muscles Dorsal roots - contain axons of AFFERENT SENSORY neurons - carry info from periphery to the CNS - extend from dorsal horns Dorsal Root Ganglion - enlargement of the dorsal root near the spinal nerve - cell bodies for pseudounipolar sensory neurons Rootlets -emerge from spine bilaterally - merge to form ventral and dorsal roots at each spinal cord segment Spinal nerve - merge point of ventral and dorsal roots - carry sensory AND motor axons - branches into dorsal and ventral ramus Dorsal ramus: carries sensory AND motor info to the posterior trunk Ventral Ramus: carries sensory and motor info to extremities and anterior trunk

Spinal cord meninges

Protects and encapsulates the spinal cord innermost layer = pia matter Pia matter forms: - denticulate ligaments anchor spinal cord left and right - filum terminally anchors spinal cord to coccyx Arachnoid matter = middle layer - CSF between arachnoid and pia lumbar punctures remove CSF in this space Dura mater - outer most layer - tough and thick continuous - cover brain stem and spinal cord to protect and support them

Proprioceptors

Special receptors in skeletal muscles (spindles), tendons (golgi tendon organs) and joints (free nerve endings) monitor tension, pressure, movement of joint/muscle and send input on body movement to the CNS travels via spinocerebellar tract - ipsilateral processing

Spinal cord length

Spinal cord stops growing around age 4 but skeleton keeps growing for a while, so they spinal cord does not fill the full space of the vertebral column cauda equina: spinal nerves that grow with vertebral column - long bundles of nerve that resemble horse tail conus medularis: most inferior portion of the spinal cord - falls around L1

If you break your leg and wear a cast for two months, what changes will you expect to observe in the leg when the cast is removed?

The healed bone will have lost bone mass because it will not have been stressed.

Which of the following statements describes the relationship between an articulation's range of motion and inherent stability?

The shoulder permits a wide range of motion, but it is the most likely to become dislocated.

Appositional bone growth increases the dimensions of cartilage and bone by:

adding cells to the surface

Synchondrosis

an almost immovable joint between bones bound by a layer of cartilage, as in the vertebrae.

Arterial supply to spinal cord

anterior spinal artery - supplies 2/3 of the spinal cord - located in antero-median fissure 2 smaller posterior spinal arteries - each one supplies one section of the remaining 1/3 of the posterior spinal cord - (1/6 each) Dorsal horn and dorsal column are covered by 2 posterior spinal arteries SUPPLIES BOTH THE ANTERIOLATERAL SYSTEM AND THE CORTICAL TRACT - a stroke in the artery would cause bilateral paralysis and loss of pain/temp/crude touch because neuron would not get blood supply

central canal of spinal cord

center of spinal cord which contains cerebrospinal fluid

Spongy bone

composed of small needlelike pieces of bone and lots of open space Layer of bone tissue having many small spaces and found just inside the layer of compact bone.

Which of the following cells play a role in initiating immune responses to pathogens that invade the skin?

dendritic (Langerhans) cells

osteoblasts

deposit matrix into the bones - bone building cells

Tactile (messiner's) corpuscles

detects FINE touch and textures

osteoclasts

dissolve bone matrix

unencapsulated tactile receptors

free nerve ending, tactile disc, root hair plexus

Which sensory receptor is responsible for providing information about pain and temperature?

free nerve endings

plane synovial joint

gliding joint in which the mating surfaces of the bones are more or less flat

Lumbar enlargement

houses neurons that innervate lower extremity muscles not as large - less fine motor control

Endochondral ossification begins with:

hyaline cartilage

endochondrial ossification steps

hyaline cartilage model of development Growth of the cartilage model Primary ossification center develops Medullary cavity development Secondary ossification center develops Articular cartilage and epiphyseal line form

Synarthrosis

immovable joint

Bulbous (Ruffini) corpuscles

in dermis and subcutaneous layer continuous deep pressure, force/motion and skin distortion

subcortical spinal pathways

involuntary pathways that help regulate our patterns of movement can excite/inhibit lower motor neuron may modulate spinal reflexes, regulate muscle tone and posture, or control orienting reflexes to audio and visual stimuli ex pathway: Raphespinal tract - helps modulate pain sensation at spinal cord level

concentric lamellae

layers of bony matrix around a central canal

Tactile (Meissner's) corpuscles provide sensory information about:

light touch

Fat pads

localized masses of adipose tissue covered by a layer of synovial membrane superficial to the joint capsule, protect articular cartilages

Vertebral Column

made up of 26 bones - 5 regions 24 individual vertebrae - 7 cervical - 12 thoracic - 5 lumbar - sacrum (made up of 5 fused vertebrae) - coccyx (3-5 fused vertebrae) (attachment site for pelvic floor)

amyotrophic lateral sclerosis (ALS)

motor neuron disease - 10% are hereditary more common in males involves slow progression of weakness and muscle atrophy beginning with hands and forearms eventuallu involves diaphragm and muscles involvied in breathing and swallowing does NOT affect sensory neurons, so sensation remains upper and lower neurons involved diagnosed via EMGs

Polysynaptic withdrawal reflex

multiple synapse - interneuron facilitates sensory and motor communication sensory receptors in skin sense extreme temp or pain which is an early sign of tissue damage signal travels from skin sensory fiber to dorsal root to dorsal horn to synapse on interneuron to ventral horn to nerve to muscle withdraws muscles but also inhibits muscles that oppose withdrawal movement and activate muscles involved in balancing posture

is the hypodermis a layer of the skin?

no -it resides just below the skin; it is superficial to the the tough connective tissue wrapping of the skeletal muscles

Monosynaptic reflex

one synapse - direct communication between sensory and motor neuron when a skeletal muscle is stretched, a muscle spindle receptor is activated receptor axons causes direct contraction of the muscle - ex: knee jer exam

intervertebral foramen

opening located between adjacent vertebrae for exit of a spinal nerve

Lower motor neurons

originate in anterior ventral horn of spinal cord axon travels to ventral root and joins the spinal nerve to the skeletal muscle long axons reach to periphery muscles axons branch to innervate multiple muscle fibers - motor unit If a lower motor neuron is excited by an upper motor neuron, the muscle will contract

Upper motor neurons

originate in brain descend spinal cord until they reach the level of exit enter the anterior ventral horn synapse with lower motor neuron can excite or inhibit lower motor neuron - can cause it to send signal to muscle to contract or can prevent it from sending signal

Which of the following is a function of synovial fluid?

provides lubrication to reduce friction between the bones of the joint

reflex arc

rapid, automatic, involuntary reaction of muscles to a stimulus includes a receptor, sensory neuron, integration area in spinal cord, a motor neuron and a muscle sensory cell body in dorsal root ganglia info goes to dorsal horn travels to ventral horn to ventral root to motor neuron can be ipsolateral (sensation and reaction on same side) or contralateral (sensation on one side and reaction on the other - crosses over through spinal cord)

Golgi Tendon Reflex

receptor = golgi tendon organ (nerve endings located in the tendon near a muscle) lower motor neuron are inhibited in response to too much tension of a muscle as sense by a golgi tendon organ prevents excessive tension to protect muscle and tendon - Ex: excessive weight lifting reflex can be overridden by huge adrenaline rush - this will lead to injury

Synostosis

site at which adjacent bones or bony components have fused together -fused bones, immovable -metopic suture of skull -epiphyseal lines of long bones

Lacuna

small cavities in bone that contain osteocytes

Tactile (Merkel) discs

stratum basale of epidermis; light touch

Layers of skin

stratum corneum stratum lucidum (thick skin only) stratum granulosum stratum spinosum stratum basale

The cervical enlargement:

supplies innervation to the upper extremity.

Cervical enlargement

supplies nerves to the shoulder and upper limbs particularly large - greater control of fine musculature

These unencapsulated tactile receptors are specialized epithelial cells in the stratum basale which release chemicals to stimulate sensory nerve endings:

tactile (Merkel) cells

encapsulated tactile receptors

tactile corpuscle, Ruffini corpuscle, and lamellated corpuscle

trabeculae

the irregular latticework of thin bony plates in spongy bone tissue supporting bundles of bony fibers in cancellous (spongy) bone

During endochondral ossification:

the matrix of the cartilage model becomes calcified. osteoclasts erode the center of the new bone to form a marrow cavity. capillaries and osteoblasts migrate into the heart of the cartilage. cells of the perichondrium differentiate into osteoblasts.

Spinal cord

transmits information between brain and body located in, surrounded by, and protected by the vertebral foramen (bone) at the center of the vertebral column surrounded by CSF for protection and nourishment meninges: connects tissue

The spinal cord sits within the _________ foramen while each spinal nerve travels through a(n) ______________ foramen.

vertebral intervertebral

Reflexes

we become consciously aware that a reflex occurs but we do not need our higher centers to cause it involve a receptor in the periphery - sensory neuron carries info to spinal cord - integration occurs in spinal cord (sometimes in interneuron) - motor neuron carries response to effector muscle

vertebral formen

where spinal cord is located - posterior of body