Download HUMAN FUNCTIONAL ANATOMY 213 THE CRANIAL CAVITY THE

HFA 213 week 12 cranial cavity
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HUMAN FUNCTIONAL ANATOMY 213
THE CRANIAL CAVITY
Enclosed by bones of the cranium
Top and sides: Frontal, parietal, temporal (squamous) & occipital
Base: Ethmoid, Sphenoid, Temporal (petrous) Occipital
THIS WEEKS LAB:
Eye, orbit and cranial cavity.
Three Cranial Fossae
1. Anterior
2. Middle
3. Posterior
READINGS
Faiz and Moffat: cranial cavity, 68 & 69
Stern: sections 57 & 58 plus 60, 61 & 62
Grant's Method:- interior of cranium and eye and orbit
Or any other regional textbook, similar sections
(Make sure you read the parts about muscle actions)
IN THIS LECTURE I WILL COVER:
The cranial cavity
The three cranial fossae
The dural folds
Dural venous sinuses
Cavernous sinus
Internal carotid artery
Emissary veins
Lacrimal apparatus
The flat bones of the skull have three layers:
1. Outer table of compact bone
2. Diploe - Spongy bone in the middle 3. Inner table of compact bones.
The Diploe is highly vascular and contains
many veins that drain into the dural
venous sinuses (and also to veins outside
the cranial cavity)
Next Week
No lecture planned but.......
The lab class will be a MOCK LAB TEST and revision
HFA 213 week 12 cranial cavity
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THE CRANIAL CAVITY
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DURAL FOLDS
The inside of the cranial cavity is lined with endosteum and the dura.
The dura is raised into folds that partition the cranial cavity:
1. Falx cerebri: Lies in the sagittal plane and separates the cerebral
hemispheres
2. Tentorium cerebelli: forms a roof over the cerebellum in the
posterior cranial fossa and separates it from the occipital lobes of the
cerebrum.
The tentorial notch is a small opening in the tentorium. Below it is the
medulla pons and cerebellum, above it is the cerebrum
DURAL VENOUS SINUSES
Where the dural folds are attached to the
inside of the cranial cavity, there are
triangular gaps formed between the
endosteum and the dura.
Falx cerebri has the superior sagittal sinus
in its attached margin, and the
inferior sagittal sinus in its free
margin.
The tentorium cerebelli has the transverse sinus in the margin that
attaches to the occipital bone, and the superior petrosal sinus in the
margin that attaches to the petrous temporal bone.
The straight sinus runs in the intersection of the falx and tentorium
The occipital sinus runs in the attached margin of the falx cerebelli
Two other smaller dural folds are present:
1. Falx cerebelli partially separates the cerebellar hemispheres
2. Diaphragma sellae separates the pituitary gland from the
hypothalamus. It has a small hole for the pituitary stalk.
The cavernous
sinus lies
below the
diaphragma
sellae on either
side of the
pituitary gland
HFA 213 week 12 cranial cavity
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Emissary veins connect the dural venous sinuses (sometimes via diploic
veins) to veins outside the cranial cavity.
Two other sinuses lie in grooves in the bone:
1. The sigmoid sinus lies in an “Sshaped” groove at the sides of the
posterior cranial fossa (it joins the
transverse sinus to the jugular foramen)
2. The inferior petrosal sinus lies in a
groove on the back of the petrous
temporal bone (it joins the cavernous
sinus to the jugular foramen)
Some foraminae that transmit these veins are:
1. Parietal (superior sagittal)
2. Mastoid (sigmoid)
3. Posterior condylar (sigmoid)
4. “Vesalian” foramen (Cavernous)
In addition some veins of the orbit
(ophthalmic veins) connect the face
veins to the cavernous sinus.
The internal jugular vein is formed at the junction of the sigmoid and
inferior petrosal sinuses
Blood can travel in either direction through the diploic and emissary
veins and this means that they can a pathway for infection travelling
from the face or scalp to the brain.
Venous blood from the brain and diploe drains towards the internal
jugular vein:
It is not uncommon for a facial infection (such as from a pimple on the
forehead or nose) to be transmitted to the cavernous sinus and cause
a fatal brain infection. YOU SHOULDN’T PICK PIMPLES –
ESPECIALLY ON THE FOREHEAD OR NOSE
Sup sag sinus to the
transverse sinus.
Inf sag sinus to the straight
sinus to the transverse
sinus
The transverse sinus drains
to the sigmoid sinus
Cavernous sinus through the
sup petrosal sinus to the sigmoid
or through the inferior petrosal sinus to the jugular vein.
HFA 213 week 12 cranial cavity
THE INTERNAL CAROTID ARTERY AND
CAVERNOUS SINUS
The internal carotid artery travels through
the carotid canal which goes upwards
and then medially through the
petrous temporal bone.
It emerges in the upper part of the foramen
lacerum and then enters the cranial
cavity inside the cavernous sinus
It runs forwards and in the cavernous
sinus, then turns upwards and then
back to enter the subarachnoid space near the optic nerves.
In the cavernous sinus the carotid artery is
accompanied by the nerves that goes
through the superior orbital fissure.
1. Oculomotor (CN III)
2. Trochlea (CN IV)
3. Ophthalmic (CN V1)
4. Abducens (CN VI)
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EMISSARY VEINS
DURAL VENOUS SINUSES
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THE SUPPLY AND DRAINAGE OF TEARS
Tears are produced by the lachrymal gland which lies in
the upper lateral corner of the orbit. Tears are
released into the conjunctival sac in the upper
lateral quadrant of the eye.
The lacrimal gland is controlled by parasympathetic
nerves (CN VII greater petrosal – pterygopalatine
ganglion – zygomatic and lacrimal branches of the
trigeminal). Stimuli that trigger tears are chemical
or mechanical irritation of the eye (reflex involving
the nasociliary branch of the trigeminal), but also
emotional factors can trigger the flow of tears
The movements of the eyelids when you blink gradually move tears (and
any foreign particles) towards the medial corner of the eye.
Tears drain out of the eye through two tiny holes (lacrimal puncta)
above and below the lacrimal caruncle. The lacrimal puncta are
connected to lacrimal canaliculi and empty into the lacrimal sac.
The lacrimal sac drains via the nasolacrimal duct into the inferior meatus
of the nose