H12: Scalp and Cranial Cavity

Scalp

consists of 5 layers of soft tissue that cover the calvaria

Those layers include skin, close subcutaneous tissue, aponeurosis of 2 muscles, loose subaponeurotic tissue, and the pericranium

The first three layers are collectively called the ________ , why?

scalp proper

are clinically regarded as a single layer because they remain together when cut during surgery or torn off during an accident

Scalp layers

Skin

Close subcutaneous tissue

Aponeurosis

Loose subaponeurotic tissue

Pericranium

Layer 1 of scalp

LAYER 1- Skin makes up the first layer and is commonly found containing hair and sebaceous glands

Layer 2 of scalp

LAYER 2 - Close

subcutaneous tissue

(connective tissue) is richly vascularized and well supplied with nerves

Layer 3 of scalp

Aponeurosis is a flattened tendon

It is named galea aponeurotica (from Latin galea = "helmet")

The aponeurosis is found between the frontalis muscle anteriorly and the occipitalis muscle posteriorly

It is also referred to as the epicranium

Layer 3 of scalp is also referred to as

epicranium

or

aponeurosis

or

galea aponeurotica

Latin root for aponeurosis

galea aponeurotica (from Latin galea = "helmet")

the aponeurosis is found between

frontalis muscle anteriorly and the occipitalis muscle posteriorly

Layer 4 of the scalp

LAYER 4 - Loose

subaponeurotic tissue allows free movement of the scalp proper (Layers 1-3)

The loose connective tissue that allows free movement also contains many potential spaces that are capable of filling with fluid and allowing pus or blood to spread easily through here

[Emissary] veins connect this layer with the dural sinuses and can potentially lead to the spread of infection from this layer to the cranial cavity

Therefore, this is known as the DANGER LAYER

Layer 4 allows free movement of _____

scalp proper (layers 1 -3)

Layer 4 is also referred to as? Why?

DANGER LAYER

The loose connective tissue that allows free movement also contains many potential spaces that are capable of filling with fluid and allowing pus or blood to spread easily through here

[Emissary] veins connect this layer with the dural sinuses and can potentially lead to the spread of infection from this layer to the cranial cavity

Layer 5 of the scalp

(deepest) - Pericranium is firmly anchored to the skull and is also known as the PERIOSTEUM of the external surface of the skull

Layer 5 of the scalp is also referred to as

periosteum

or

pericranium

cranial bone

The cranial bone is made up of 3 layers that can be seen when looking at the skull

Outer table

DIPLOË

Inner table

Different cranial bones vary in thickness; the occipital and frontal regions are thick, and the temporal region is thinner

cranial bone is made up ___ layers

3

Outer table

DIPLOË

Inner table

outer table

On the external surface of the outer table is periosteum or pericranium, which is the 5th layer of the scalp

The external layer is called the OUTER TABLE and is made of compact bone

DIPLOË

The middle layer is made of spongy bone and is called the DIPLOË

inner table

The internal layer is called the INNER TABLE and is made of compact bone

Lining the inner table is ENDOCRANIUM or

ENDOSTEUM, which is the outer layer of dura

blood supply of the scalp SUMMARY

Blood supply comes from vessels below, specifically branches of the external carotid and the internal carotid arteries

Many of these vessels anastomose freely in the second layer of the scalp, close subcutaneous tissue

Branches of the internal carotid arteries supply the frontal region

Branches supplying the temporal and occipital regions come off of the external carotid artery

Veins accompany the arteries in the venae comitantes arrangement (in which 2 veins lie on either side of the artery) and have the same names as the arteries

blood supply of the scalp comes from vessels below, specifically the ______ &

_________

external and internal carotid arteries

many of the vessels of the scalp anastomose freely in the _____ layer of the scalp

second layer, close subcutaneous tissue

branches of the internal carotid arteries supply what region?

frontal region

branches of the external carotid arteries supply what region?

temporal and occipital regions

venae comitantes

Blood supply of the scalp:

Veins accompany the arteries in the venae comitantes arrangement (in which 2 veins lie on either side of the artery) and have the same names as the arteries

(means vein accompanying)

Innervation of the scalp anterior to the external ear

Innervation of the scalp anterior to the external ears is through branches of the 3 divisions of the trigeminal nerve, cranial nerve V: ophthalmic (V1), maxillary (V2), and mandibular (V3)

Innervation of the scalp posterior to the ear

Posterior to the ear, nerve supply to the scalp is from the cervical spinal nerves

meninges of the brain

Similar to the spinal cord, there are 3 layers of meninges surrounding the brain: dura mater, arachnoid mater, and pia mater

Dura mater of the brain: 2 layers

1. endosteal dura

2. meningeal dura

Both of these layers adhere to each other except at certain locations where they separate, called DURAL SINUSES (C)

Dura mater outer layer

ENDOSTEAL DURA (A)

You already know about the endocranium or endosteum, the outer layer that fuses to the skull; this is also called the ENDOSTEAL DURA (A)

Dura mater inner layer

MENINGEAL DURA (B)

folders internally at four locations called dural folds

Dural sinuses and dura mater

Both of these layers of dura mater adhere to each other except at certain locations where they separate, called DURAL SINUSES (C)

Dural sinuses are spaces that contain blood and absorbed cerebrospinal fluid (CSF)

dural folds

Folded inner layer of dura mater

4 locations

4 types of dural folds

falx cerebri

tentorium cerebelli

falx cerebelli

diaphragma sellae

falx cerebri

separates the superior portion of the right and left sides of the cerebrum

Where does the falx cerebri attach?

It attaches anteriorly to the crista galli and posterioly to the tentorium cerebelli at the level of the internal occipital protuberance

Latin root for falx

falx = sickle

the fold is sickle-shaped

Tentorium cerebelli

forms a tent over the cerebellum

Latin root for tentnorium cerebelli

Latin tentorium = "tent"

falx cerebelli

nother sickle-shaped dural fold inferior to the surface of the tentorium cerebelli

It separates the right and left cerebellar hemispheres

diaphragma sellae

a small, circular, horizontal sheet of dura that forms a roof over the hypophyseal fossa in the sella turcica

a. It is pierced by they hypophyseal stalk (or infundibulum)

arterial supply of the dura

not from the same vessels supplying the scalp

Dura is supplied by the meningeal arteries, including the MIDDLE MENINGEAL ARTERY

It branches off of the maxillary artery coming off of the external carotid and courses external to the dura mater

The inner surface of the calvaria contains indentations from these vessels

middle meningeal artery

supplies dura mater

it branches off the maxillary artery coming off of the external carotid and courses external to the dura mater

Extradural or Epidural Hemorrhage (extra)

when meningeal vessels are injured

ex. blow to the side of the head

pressure from ruptured vessel separates the periosteal and dura proper

raises intracranial pressure = herniation

shape of football

dural sinuses

When the 2 layers of the dura mater separate, this is called sinus

The sinus is actually a vein lined with endothelium that is not collapsible

They drain all blood and absorbed CSF from the brain; they all flow toward the internal jugular vein

6 dural sinuses

superior sagittal sinus

inferior sagittal sinus

straight sinus

transverse sinus

sigmoid sinus

cavernous sinuses

superior sagittal sinus

lies in

the median plane on the superior portion of the falx cerebri

It connects with the diploic veins, cerebral veins, and the lateral expansions of the superior sagittal sinus called the lateral lacunae

It drains posteriorly into the confluence of sinuses (or CONFLUENCE)

superior sagittal sinus drains into

confluence of sinuses

Confulence of sinuses

Joining together of sinuses

collects blood and CSF DIRECTLY from superior sagittal sinus, straight sinus (inferior sagittal sinus drains into straight sinus) , occiptal sinus

this drains into transverse sinuses

inferior sagittal sinus

also lies in the median

plane but on the inferior portion of the falx cerebri

It drains posteriorly into the straight sinus

inferior sagittal sinus drains into

straight sinus

straight sinus

is found between the junction of the falx cerebri and the tentorium cerebelli

It receives blood from the inferior sagittal sinus and cerebral veins

It drains posteriorly into the confluence of sinuses

straight sinus receives blood from ____ and drains into _____

from inferior sagittal sinus and cerebral veins

drains into confluence of sinuses

transverse sinus

begins at the

confluence and courses laterally

It is found within the external border of the tentorium cerebelli

It passes anteriorly toward the petrous portion of the temporal bone to the sigmoid sinus

transverse sinus receives blood from ______ and drains into ______

from confluence

drains into sigmoid sinus

sigmoid sinus

extends from the transverse sinus and courses in an S-shape (S for the Greek letter sigma) along the petrous portion of the temporal bone to the jugular foramen, where it continues in the neck as the internal jugular vein

sigmoid sinus receives blood from _____ and drains into ______

from transverse sinus , superior petrossal sinus, inferior petrossal sinus

drains into internal jugular vein

cavernous sinuses

are found lateral to the sella turcica on each side

They were named cavernous because they have a cave-like appearance

pathway of blood and CSF in dural sinuses

dural sinuses image - superior

dural sinuses image 2 - side view

circle of willis also known as

cerebral arterial circle

circle of willis

(cerebral arterial circle) is a polygonal anastomosis between the right and left internal carotid arteries and the right and left vertebral arteries

the _______, after entering the cranial cavity will divide into 2 cerebral arteries: ________ and _______

The internal carotid artery, after entering the cranial cavity, will divide into 2 cerebral arteries, the ANTERIOR CEREBRAL

ARTERY, (which courses within the longitudinal fissure of the cerebrum), and the MIDDLE CEREBRAL ARTERY, (which

courses in the lateral fissure of the cerebrum)

internal carotid artery

after entering cranial cavity it will divide into 2 cerebral arteries:

1. anterior cerebral artery

2. middle cerebral artery

anterior cerebral artery

branch off internal carotid artery

courses within the longitudinal fissure of the cerebrum

(extra: least affected by strokes, leg weakness)

middle cerebral artery

largest branch off internal carotid artery

courses in the lateral fissure of the cerebrum

(extra: most common stroke, paralysis of lower face, affects upper limbs and some vision)

longitudinal fissure

separates cerebral hemispheres

lateral fissure

separates temporal lobe from frontal and parietal lobes

Veretebral artery

branches off of the subclavian artery and travels upward through the foramina in the transverse processes of the cervical vertebrae CV6-CV1

It passes through the foramen magnum and joins the vertebral artery from the opposite side to form the BASILAR ARTERY (E)

Basilar Artery

(E)

Formed by two vertebral arteries coming together after passing through the foramen magnum

This vessel courses along a groove on the pons and divides into the two POSTERIOR CEREBRAL ARTERIES (F)

posterior cerebral arteries

(F)

branches off the basilar artery

(extra: strokes in this affect vision)

circle of willis is formed by

1 Basilar artery (E)

2 Posterior cerebral arteries (F)

2 Posterior communicating arteries (G)

2 Internal carotid arteries (A)

2 Anterior cerebral arteries (B)

1 Anterior communicating artery (D)

stroke

Damage to the brain from interruption of its blood supply.

circle of willis on brain