HFA 213 week 12 cranial cavity 1 2 HUMAN FUNCTIONAL ANATOMY 213 THE CRANIAL CAVITY THE CRANIAL CAVITY Enclosed by bones of the cranium THIS WEEKS LAB: Top and sides: Frontal, parietal, temporal (squamous) & occipital Eye, orbit and cranial cavity. Base: Ethmoid, Sphenoid, Temporal (petrous) Occipital
READINGS Three Cranial Fossae Faiz and Moffat: cranial cavity, 68 & 69 1. Anterior Stern: sections 57 & 58 plus 60, 61 & 62 2. Middle Grant's Method:- interior of cranium and eye and orbit 3. Posterior 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 The flat bones of the skull have three layers: Internal carotid artery 1. Outer table of compact bone Emissary veins 2. Diploe - Spongy bone in the middle - Lacrimal apparatus 3. Inner table of compact bones. The Diploe is highly vascular and contains Next Week many veins that drain into the dural No lecture planned but...... venous sinuses (and also to veins outside The lab class will be a MOCK LAB TEST and revision the cranial cavity)
HFA 213 week 12 cranial cavity 3 4 DURAL FOLDS DURAL VENOUS SINUSES
The inside of the cranial cavity is lined with endosteum and the dura. Where the dural folds are attached to the inside of the cranial cavity, there are The dura is raised into folds that partition the cranial cavity: triangular gaps formed between the 1. Falx cerebri: Lies in the sagittal plane and separates the cerebral endosteum and the dura. hemispheres 2. Tentorium cerebelli: forms a roof over the cerebellum in the Falx cerebri has the superior sagittal sinus posterior cranial fossa and separates it from the occipital lobes of the in its attached margin, and the cerebrum. inferior sagittal sinus in its free The tentorial notch is a small opening in the tentorium. Below it is the margin. medulla pons and cerebellum, above it is the cerebrum
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
The cavernous sinus lies below the
diaphragma sellae on either Two other smaller dural folds are present: side of the 1. Falx cerebelli partially separates the cerebellar hemispheres pituitary gland 2. Diaphragma sellae separates the pituitary gland from the hypothalamus. It has a small hole for the pituitary stalk. HFA 213 week 12 cranial cavity 5 6 DURAL VENOUS SINUSES EMISSARY VEINS
Emissary veins connect the dural venous sinuses (sometimes via diploic Two other sinuses lie in grooves in the bone: veins) to veins outside the cranial cavity. 1. The sigmoid sinus lies in an “S- shaped” groove at the sides of the Some foraminae that transmit these veins are: posterior cranial fossa (it joins the 1. Parietal (superior sagittal) transverse sinus to the jugular foramen) 2. Mastoid (sigmoid) 2. The inferior petrosal sinus lies in a 3. Posterior condylar (sigmoid) groove on the back of the petrous 4. “Vesalian” foramen (Cavernous) temporal bone (it joins the cavernous sinus to the jugular foramen) In addition some veins of the orbit (ophthalmic veins) connect the face The internal jugular vein is formed at the junction of the sigmoid and veins to the cavernous sinus. inferior petrosal sinuses Blood can travel in either direction through the diploic and emissary Venous blood from the brain and diploe drains towards the internal veins and this means that they can a pathway for infection travelling jugular vein: from the face or scalp to the brain.
It is not uncommon for a facial infection (such as from a pimple on the Sup sag sinus to the forehead or nose) to be transmitted to the cavernous sinus and cause transverse sinus. a fatal brain infection. YOU SHOULDN’T PICK PIMPLES – Inf sag sinus to the straight ESPECIALLY ON THE FOREHEAD OR NOSE 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 7 8 THE INTERNAL CAROTID ARTERY AND THE SUPPLY AND DRAINAGE OF TEARS CAVERNOUS SINUS Tears are produced by the lachrymal gland which lies in the upper lateral corner of the orbit. Tears are The internal carotid artery travels through released into the conjunctival sac in the upper the carotid canal which goes upwards lateral quadrant of the eye. and then medially through the petrous temporal bone. The lacrimal gland is controlled by parasympathetic It emerges in the upper part of the foramen nerves (CN VII greater petrosal – pterygopalatine lacerum and then enters the cranial ganglion – zygomatic and lacrimal branches of the cavity inside the cavernous sinus trigeminal). Stimuli that trigger tears are chemical or mechanical irritation of the eye (reflex involving It runs forwards and in the cavernous the nasociliary branch of the trigeminal), but also sinus, then turns upwards and then emotional factors can trigger the flow of tears back to enter the subarachnoid space near the optic nerves. The movements of the eyelids when you blink gradually move tears (and In the cavernous sinus the carotid artery is any foreign particles) towards the medial corner of the eye. accompanied by the nerves that goes Tears drain out of the eye through two tiny holes (lacrimal puncta) through the superior orbital fissure. above and below the lacrimal caruncle. The lacrimal puncta are 1. Oculomotor (CN III) connected to lacrimal canaliculi and empty into the lacrimal sac. 2. Trochlea (CN IV) The lacrimal sac drains via the nasolacrimal duct into the inferior meatus 3. Ophthalmic (CN V1) of the nose 4. Abducens (CN VI)