Learning Issues Week 2 Part 2

Question 1

Dog arterial circle via vertebral artery

Answer 1

Aorta -> B. cephalic trunk -> Right subclavian -> vertebral artery -> transverse vertebral foramina -> vertebral canal (via foramen in atlas) -> join basilar artery -> arterial circle

Question 2

Dog arterial circle via int carotid

Answer 2

aorta -> B cephalic trunk -> common carotid -> int carotid -> TOF -> carotid canal (v to petrous temporal bone at junction tympanic and basioccipital bones -> foramen lacerum-> middle cr fossa ( near rostral tip petrous temporal bone) -> cavernous sinus -> penetrate meningeal dura and arachnoid and feed arterial circle in subarachnoid space on V aspect diencephalon

Question 3

cat blood supply to arterial circle via maxillary artery

Answer 3

aorta -> B cephalic trunk -> common carotid artery -> ext carotid -> maxillary artery -> round foramen -> alar canal -> rostral alar foramen -> arterial rete (maxillary rete) -> arterial circle

Question 4

cat blood supply to arterial circle via vertebral artery

Answer 4

aorta -> b. cephalic trunk -> subclavian artery - vertebral artery -> transverse vertebral foramina -> vertebral canal (via foramen in atlas) -> basilar artery -> arterial circle

Question 5

cat blood supply to arterial circle via maxillary artery

Answer 5

aorta -> B cephalic trunk -> common carotid artery -> external carotid artery -> maxillary artery -> orbital fissure -> arterial rete -> arterial circle

Question 6

vertebral artery and cats

Answer 6

blood supply from the vertebral artery doesn’t contribute significantly to cerebral hemisphere circulation in sheep and cats and blood often flows arterial circle to basilar artery

Question 7

rostral cerebral artery

Answer 7

bilateral; runs rostrally than dorsally into the longitudinal fissure to supply medial aspect of rostral telencephalon

Question 8

middle cerebral artery

Answer 8

bilateral; runs laterally then dorsally to supply lateral hemisphere. Proximal branches supply basal nuclei, internal capsule, and choroid plexus of lateral ventricle

Question 9

caudal cerebral artery

Answer 9

bilateral; runs dorsally between diencephalon and hemisphere into longitudinal fissure to supply the thalamus, and medial aspect cd telencephalon

Question 10

rostral cerebral, middle cerebral, and caudal cerebral arteries

Answer 10

branches of these arteries anastomose dorsally but these anastomoses are not adequate to supplyy brain if one of these major arteries becomes occluded

Question 11

rostral cerebellar arteries

Answer 11

bilateral; arise from arterial circle; supply midbrain and rostral cerebellum

Question 12

caudal cerebellar arteries

Answer 12

bilateral; arise from basilar artery, supply cd cerebellum

Question 13

pontine and medullary branches

Answer 13

bilateral; branches of basilar artery that supply pons and medulla

Question 14

veins draining blood from brain parenchyma

Answer 14

converge on venous sinuses

Question 15

venus sinuses

Answer 15

endothelial lined channels continuous with venous system located within bony canals and within dural reflections between periosteal and meningeal layers of dura

Question 16

venous sinuses of skull convey blood to

Answer 16

maxillary, internal jug, vertebral veins, and internal vertebral venous plexsus

Question 17

dorsal system

Answer 17

dorsal sagittal sinus, starlight sinus, transverse sinus, sigmoid sinus, temporal sinus

Question 18

dorsal sagittal sinus

Answer 18

located in dorsal aspect of falx cerebra, drains cerebral hemispheres drain to transverse sinus

Question 19

straight sinus

Answer 19

at junction of falx ceribri and tentorium cerebelli; drains deeper parts of the brain; drains to transverse sinus

Question 20

transverse sinus

Answer 20

located within the occipital bone and tentorium cerebelli adjacent to the occipital bone; it divides at the caudal aspect of the petrosal crest into 2 branches

Question 21

sigmoid sinus

Answer 21

runs medial to the PTB splits and exits skull via jugular foramen to join the internal jugular vein and vertebral vein or joins internal vertebral venous plexus

Question 22

temporal sinus

Answer 22

runs caudolateral to PTB (b/w petrous and squamous parts of temporal bone); exists skull via retroarticular foramen, joins maxillary vein

Question 23

ventral sinus systems

Answer 23

cavernous sinus

Question 24

cavernous sinus location

Answer 24

bilateral; one on either side of hypophyseal fossa

Question 25

what runs through cavernous sinus

Answer 25

internal carotid arteries; CNs III, IV, V1, V2, VI and sympathetic postganglionic fibers traveling to the face (including the eye) run through/ adjacent sinus

Question 26

where do structures running through cavernous sinus lie

Answer 26

these structures are not actually within the sinus, bathed in blood, a layer of endothelium encloses the blood in the sinus and these structures run adjacent to the venous vascular channels

Question 27

what drains to cavernous sinus

Answer 27

receives blood daring from ventral brain and skull, face, orbit, and nasal cavity

Question 28

ruminants branches of maxillary artery

Answer 28

on either side form a rete mirabile within the cavernous sinus. May protect the brain from overheating when body temp rises during flight from predator

Question 29

blood in cavernous sinus can drain by flowing caudally

Answer 29

ventral to PTB -> basilar sinus within the occipital bone -> internal vertebral venous plexsus

Question 30

blood in cavernous sinus can drain into venous branches

Answer 30

which exit skull via multiple foramina to join the maxillary vein

Question 31

venous system drainage flow follows path of

Answer 31

lowest pressure since sinuses do not have valves. The majority of blood leaving skull flows to the internal vertebral venous plexus and the maxillary veins

Question 32

which sinuses are not bilateral

Answer 32

dorsal sagital and straight sinuses (midline structures)

Question 33

blood flow direction transverse and temporal sinuses

Answer 33

medial to lateral

Question 34

blood flow direction sigmoid sinus

Answer 34

medially

Question 35

vertebral venous plexus

Answer 35

paired interconnected veins on floor of vertebral canal in epidural space;

Question 36

how does blood leave vertebral venous plexus

Answer 36

via segmental intervertebral veins at the intervertebral foramina which drains into vertebral vein, azygous vein, cd vena cava

Question 37

vertebral venous plexus anastamoses

Answer 37

inconsistent dorsal and ventral segmental anastomoses occur between veins on either side

Question 38

vertebral venous plexus reservoir

Answer 38

provides low pressure reservoir for blood if other vessels are congested

Question 39

what enlarges vertebral venous plexus

Answer 39

is often enlarged in situations of increased abdominal pressure such as pregnancy and abdominal tumors

Question 40

stagnant blood in vertebral venous plexsus

Answer 40

can facilitate the seeding of tumors or infectious agents within the vertebral column

Question 41

vertebral venous plexus in case high pressure

Answer 41

blood may move in retrograde direction into the venous sinus of cranial cavity

Question 42

vertebra venous plexus clinical significance

Answer 42

can be quite large, may be punctured during attempts at epidural or intrathecal injection

Question 43

blood CNS barrier overview

Answer 43

prevents bad things from exiting capillaries in the brain; CNS requires stable and specific chemical environment; many chemicals, proteins, drugs are excluded from CNS; barriers can be compromised under various circumstances

Question 44

what would happen if extracellular fluid of CNS had sam chemical composition of blood

Answer 44

neurons would be exposed to constantly changing chemical environment that would cause erratic activity in neuron circuits and failure of the system; fx neurons in CNS highly sensitive to alterations in pH and ionic composition of CNS interstitial fluid that neuromodulators or toxins

Question 45

systems to ensure proper conditions maintained in interstitial compartment of CNS

Answer 45

relay of fact that lipid bilayer of cell membranes and tight junctions btwn cells are relatively impermeable to diffusion of large/ and or charged molecules

Question 46

lipid membranes ineffective at

Answer 46

excluding small lipophilic molecules and gases such as CO2 and O2; barrier cells in these system scan transport specific large or charged molecules across their cell membranes into CNS and can exclude certain lipophilic molecules by active efflux pumps

Question 47

3 major components CNS barrier system

Answer 47

arachnoid cellular layer, blood- CNS barrier, Blood-CSF barrier

Question 48

arachnoid cellular layer

Answer 48

cells in this layer have tight junctions between them; barrier layer prevents substances from leaky vessels and interstitial fluid within and external to dura from contaminating CSF in the underlying subarachnoid space

Question 49

substances in subarachnoid space

Answer 49

can easily penetrate the pia matter and enter the brain or spinal cord

Question 50

Blood-CNS barrier

Answer 50

endothelium lining blood vessels within subarachnoid space and brain/ spinal cord tissue is specialized; tight junctions between non-fenestrated endothelial cells exclude many molecules from diffusing into molecuels

Question 51

astrocyte foot processes

Answer 51

play a role in barrier by modifying permeability of endothelial cells and controlling active transport mechanisms across endothelial barrier; cover most of basement membrane off capillary endothelial cells

Question 52

blood brain barrier inaccurate name

Answer 52

because same system in spinal cord; desired substances can cross capillary endothelium via facilitated diffusion or active transport

Question 53

Blood-CSF barrier

Answer 53

apical tight junctions btwn choroid epithelial cells in choroid plexus prevent free diffusion of substances from leaky choroidal capillaries into CSF; composition CSF dictated by these cells via numerous transport mechanisms; critical bc ependymal lining of ventricles is permeable and any substances in CSF will end up in brain/ spinal cord extracellular space as well

Question 54

intercerebrayl blood vessels

Answer 54

have tight junctions between non-fenestrated endothelial cells

Question 55

blood vessels in choroid plexsus

Answer 55

are leaky; choroid epithelium has tight junctions allowing CSF composition to be tightly regulated

Question 56

arachnoid cellular layers

Answer 56

has tight junctions allowing this barrier to exclude substances originating external to mingles from CSF and subarachnoid space

Question 57

fluid within SAS and ventricles

Answer 57

in free communication with interstitial compartment of brain and spinal cord tissue and plays an important tole in delivering substances and removing waste from NT

Question 58

clinical relevance CNS barrier system

Answer 58

- CNS barrier system excludes many proteins, drugs, and other molecules from CNS; large ionized and/ or non-lipid soluble drugs may not achieve therapeutic levels in CNS; lipid soluble drugs may be excluded due to efflux pumps - can take advantage of this when trying to keep drug like Claritin from causing drowsiness bc keep it from crossing CNS barrier

Question 59

disruption barrier system

Answer 59

may occur during dx; fever, inflammation, elevated bilirubin can compromise brain barrier system -> CNS dysfunction because alteration in CNS chemical microenvionrment

Question 60

Circumventricular organs

Answer 60

play role in monitoring composition plasma and require access to components normally excluded by blood brain barrier; these regions of brain lack blood brain barrier to perform their fx; ex leaky capillary beds in hypothalamus and pituitary gland