Chapter 12: Scalp and Cranial Cavity

how many layers of soft tissue does the scalp consist of?

five layers

what do the layers of the scalp cover?

the calvaria

what are the layers of the scalp?

-skin

-close subcutaneous tissue

-aponeurosis of two muscles

-loose subaponeurotic tissues

-pericranium

what are the first three layers of the scalp called?

scalp proper

what is the first three layers of the scalp clinically regarded as? why?

a SINGLE layer--> bc they remain together when cut during surgery or torn off during an accident

what is the first layer of the scalp?

the skin

what is the skin composed of?

hair and sebaceous glands

what is the second layer of the scalp?

close subcutaneous tissue (connective tissue)

what is the close subcutaneous tissue composed of?

richly vascularized and well supplied with nerves

what is the third layer of the scalp?

aponeurosis of two muscles

what is aponeurosis?

a flattened tendon

aponeurosis is named ____

galea aponeurotica

from Latin, galea means what?

helmet

the aponeurosis is found between what?

the frontalis muscle anteriorly and the occipitalis muscle posteriorly

aponeurosis is also referred to as the ____

epicranium

what is the fourth layer of the scalp?

loose subaponeurotic tissue

what is the function of the loose subaponeurotic tissue?

allows free movement of the scalp proper (layers 1-3)

what does loose connective tissue contain?

many potential spaces that are capable of filling fluid and allowing pus or blood to spread easily through here

what do the veins (emissary veins) connect the LOOSE SUBAPONEUROTIC TISSUE layer with?

dural sinuses--> which can lead to the spread of infection from this layer to the cranial cavity

what is this layer (4) also called?

danger layer

what is the fifth layer of the scalp?

pericranium (aka periosteum)

where is the pericranium?

anchored to the skull (external surface of the skull)

pericranium is the (most superficial/deepest) layer of the scalp?

DEEPEST

how many layers is the cranial bone made up of (when looking at the skull)?

3

what is on the external surface of the outer table (of the cranial bone)?

pericranium or periosteum (5th layer of the scalp)

what is the external layer of the cranial bone?

outer table

what is the outer table made of?

compact bone

what is the middle layer of the cranial bone?

diploë

what is the middle layer made of?

spongy bone

what is the internal layer of the cranial bone?

inner table

what is the inner table made up of?

compact bone

what do the cranial bones vary in?

thickness

what regions of the cranium are the thickest?

occipital and frontal

what regions of the cranium are thinner?

temporal

what is the inner table lined with?

endocranium or endosteum

what is another name for the endocranium?

endosteal dura

what is the endocranium/endosteum?

outer layer of dura

where does the blood supply for the scalp come from?

the vessels below--> specifically branches of the external and internal carotid arteries

where do many of these vessels (supplying the scalp) anastomose or come together?

freely in the second layer of the scalp (close subcutaneous tissue)

branches of the internal carotid arteries supply what region?

FRONTAL region

branches of the external carotid arteries supply what region?

OCCIPITAL and TEMPORAL regions

how are the veins and arteries arranged?

VENAE COMITANTES - where the veins accompany the arteries (2 veins lying on either side of the artery)

how are the veins named in venae comitantes?

same name as the artery it accompanies

how is the scalp innervated ANTERIOR to the external ears?

the branches of the 3 divisions of CN V (trigeminal nerve)

what are the 3 divisions of the trigeminal nerve (CN V)?

ophthalmic, maxillary, mandibular

how is the scalp innervated POSTERIOR to the external ears?

cervical spinal nerves

like the spinal cord, what surrounds the brain?

meninges

how many layers of meninges in the brain? what are they?

3 layers - dura mater, arachnoid mater, pia mater

how many layers does the dura mater consist of? what are they?

2:

-endosteal dura (aka endosteum or endocranium)

-meningeal dura

what is the outer layer of the dura mater?

endosteal dura (aka endosteum aka endocranium)

what is the endosteal dura/endosteum/endocranium?

outer layer of the dura that fuses with the skull

what is the inner layer of the dura mater?

meningeal dura

what do the inner and outer dural layers do?

adhere to each other

where do the inner and outer dural layers separate?

dural sinuses

what are the dural sinus spaces?

spaces that contain blood and absorbed cerebrospinal fluid (CSF)

what does the inner layer of the dura (MENINGEAL DURA) do and form?

folds internally at four locations--> forming dural folds

what are the 4 dural folds?

-falx cerebri

-falx cerebelli

-tentorium cerebelli

-diaphragma sellae

what is the falx cerebri?

dural fold that separates the superior portion of the right and left sides of the cerebrum

where does the falx cerebri attach:

anteriorly?

posteriorly?

anteriorly: crista galli

posteriorly: tentorium cerebelli (at the level of the internal occipital protuberance)

from Latin, falx means what?

sickle

what is the shape of falx cerebri fold?

sickle-shaped

what is the tentorium cerebelli?

tent over cerebellum

from latin, tentorium means what?

tent

what is the shape of the falx cerebelli?

sickle-shaped dural fold

where is falx cerebelli located?

INFERIOR to the surface of the tentorium cerebelli

what does the falx cerebelli separate?

right and left cerebellar hemispheres

what is the diaphragma sellae?

small, circular, horizontal sheet of dura

where is the diaphragma sellae located?

sella turcica--> forming a roof over the hypophyseal fossa

what is the diaphragma sellae pierced by?

hypophyseal stalk (infundibulum)

do the same arteries that supply scalp supply the dura?

NO

what is the dura supplied by?

meningeal arteries, including the middle meningeal artery

what is the middle meningeal artery?

a branch off of the maxillary artery

where does the maxillary artery come from?

comes off the external carotid and courses external to the dura mater

where can indentations from these vessels be found?

inner surface of calvaria

what happens when the 2 layers of dura mater separate?

form a sinus

what is a sinus?

a vein lined with endothelium that is NOT collapsible

what do the sinuses drain?

blood and absorbed CSF from the brain

where do all the sinuses flow toward?

internal jugular vein

what are the dural sinuses?

1. superior sagittal sinus

2. inferior sagittal sinus

3. straight sinus

4. transverse sinus

5. sigmoid sinus

6. cavernous sinus (2 of them)

where is the superior sagittal sinus?

the sinus that lies in the median plane on the superior portion of the falx cerebri

what are the lateral expansions of the superior sagittal sinus?

lateral lacunae

what does the superior sagittal sinus connect with?

diploic veins, cerebral veins, and the lateral lacunae

where does the superior sagittal sinus drain?

posteriorly into the confluence of sinuses (CONFLUENCE)

where is the inferior sagittal sinus?

lies in the median plane but on the INFERIOR portion of the falx cerebri

where does the inferior sagittal sinus drain?

posteriorly into the straight sinus

where is the straight sinus?

found between the junction of the falx cerebri and tentorium cerebelli

where does the straight sinus receive blood from?

inferior sagittal sinus and cerebral veins

where does the straight sinus drain?

posteriorly into the confluence of sinuses

where is the transverse sinus found?

within the external border of the tentorium cerebelli

where does the transverse sinus begin and what does it course?

begins at the confluence and courses laterally

where does the transverse sinus pass?

passes anteriorly TOWARD the petrous portion of the temporal bone to the sigmoid sinus

where is the sigmoid sinus?

extends from the transverse sinus and courses along the petrous portion of the jugular foramen, where it continues into the neck as the internal jugular vein

what shape does the sigmoid sinus course along the petrous portion of the jugular foramen in?

S shape

what is the Greek letter sigma?

S

how many cavernous sinuses are there?

2

where are the cavernous sinuses found?

lateral to the sella turcica on each side

why are they named cavernous?

they have a cave-like appearance

what is the Circle of Willis?

a polygonal anastomosis between the Right and Left internal carotid arteries and the Right and Left vertebral arteries

what is another name for the Circle of Willis?

cerebral arterial circle

after entering the cranial cavity, what does the internal carotid artery divide into?

2 cerebral arteries: anterior cerebral artery and middle cerebral artery