BIO210 Weekly Guide #6
THE SKULL;
THE HEAD
After completing this laboratory you should be able to:
1) Identify the bones of the skull, as well as the major surface features (including fossae and foramina) of those bones
2) Characterize skull bones as contributing to the base of the skull, calvarium, face, jaws, and/or orbits
3) Identify the major muscles of the face, providing the origin, insertion, and actions of each
4) Characterize human dentition in gross and microscopic anatomy
5) Recognize and describe the brain ventricular structures and meninges
6) Recognize the major circulatory structures of the brain and external head
7) Describe the production, distribution, and reabsorption of cerebrospinal fluid.
Guide to Gross Anatomy Guide to Histology Guide to Physiology
Outline
I. The Skull {FAP 7-2 to 7-4}
A. Regions
cranium - floor and vault (calvarium)
face
jaws
B. Bones - review
C. Processes, Fossae, and Foramina
II. Dentition {FAP 24-2}
A. Dentition
incisors, canines, premolars, molars
deciduous vs. permanent teeeth
dental pattern
B. Tooth structure
dentary bones - maxillae and mandible
tooth development
III. Muscles of the Head {FAP 11-5 to 11-8, Tables 11-2 to 11-4}
A. Muscles of mastication
temporalis
masseter
pterygoids
B. Muscles of facial expression
occipitofrontalis
orbicularis oculi and levator palpebrae
orbicularis oris, zygomatics, bucinator, depressor anguli oris
platysma
C. Extrinsic muscles of the eye {FAP 11-6, Table 11-3}
4 rectus muscles
2 oblique muscles
IV. External Circulation of the Head {FAP 21-7}
A. External carotid arteries
occipital arteries
superficial temporal arteries
maxillary arteries
facial arteries
B. External jugular veins
occipital veins
temporal veins
maxillary arteries
facial arteries
V. Arterial Circulation of the Brain {FAP 21-21}
A. Internal carotid arteries
B. Vertebral arteries --> Basilar artery
C. Circle of Willis
anterior cerebral arteries
middle cerebral arteries
posterior cerebral arteries
anterior communicating artery
posterior communicating arteries
VI. Meninges and Venous Drainage of the Brain {FAP 21-21}
A. 3 Meninges - histology
dura mater
arachnoid and subarachnoid space
pia mater
B. Dural reflections
falx cerebri
falx cerebelli
tentorium cerebelli
C. Dural sinuses
superior sagittal sinus
inferior sagittal sinus
straight sinus
sigmoid sinus
sinus confluens
transverse sinuses
petrosal sinuses
cavernous sinuses
D. Internal jugular veins
VII. Cerebrospinal Fluid Circulation {FAP 14-1, 14-2}
A. Origin of CSF
choroid plexus
structure and locations
production of CSF
B. Flow of CSF
lateral ventricles-->foramina of Monro-->3rd ventricle-->cerebral aqueduct-->
4th ventricle-->spinal cord central canal (dead end)
\-->foramina of Luschka & Magendie -->subarachnoid space--> arachnoid granulations-->dural sinuses-->internal jugular veins
(venous drainage)
Gross Anatomy List
Skull:
cranial bones:
frontal (= "front")
occipital (= "back of head")
ethmoid (= "sieve-like")
sphenoid (= "wedge-shaped")
temporals (= "time"- where you first get gray hair)
parietals (= "wall")
facial bones:
mandible (= "lower jaw")
vomer (= "plow")
maxillae (= "upper jaw")
zygomatics (= "cheekbone")
nasals (= "nose")
lacrimals (= "tear")
palatines (= "roof of mouth")
inferior nasal conchae (= "shell")
Ossicles:
malleus (= "hammer")
incus (= "anvil")
stapes (= "stirrup")
Muscles of Mastication: Muscles of Facial Expression: Extrinsic Eye Muscles:
temporalis occipitofrontalis superior rectus
masseter orbicularis oculi inferior rectus
medial pterygoid orbicularis oris medial rectus
lateral pterygoid platysma lateral rectus
buccinator superior oblique
zygomaticus inferior oblique
levator palpebrae
depressor anguli oris
Arteries: Veins: Venous Sinuses:
external carotids external jugulars sup. & inf. sagittal sinuses
occipitals occipitals straight sinus
superficial temporals temporals sigmoid sinus
maxillaries maxillaries petrosal sinuses
facials facials sinus confluens
internal carotids internal jugulars transverse sinuses
vertebrals cavernous sinuses
basilar
circle of Willis
posterior cerebrals
middle cerebrals
anterior cerebrals
anterior communicating
Meninges of the Brain: Teeth:
Dura Mater Incisors
Arachnoid Mater Canines
Pia Mater Premolars
Molars
KEY: Know location & action (for muscles)
Know locations and major features (for bones)
Know locations and regions supplied/drained (for blood vessels)
Know locations and functions (for other structures)
Not responsible for
Guide to Gross Anatomy
Your texts do not treat the skull and head as a separate topic, so the background for the following will be distributed in several text locations. Use the index notes to find applicable figures and guides.
Skull {FAP 6-7, Figs. 7-2 to 7-15; APL 8.1, Figs 8.4, 8.12}
We have already introduced the bones of the skull in Week 4. This week you should review them with more attention to detail, specifically the bony surfaces, process, and foramina that relate to the brain, cranial nerves, and facial muscles.
a) Identify the following bones and their parts on the skull (the disarticulated skull will help):
Cranial bones:
frontal occipital
gabella sup. and inf. nuchal lines
supraorbital ridges occipital condyles
supraorbital margin ext. occipital protuberance
frontal sinuses
parietals
ethmoid superior temporal line
cribriform plate
crista galli temporals
perpendicular plate squamous portion
superior and middle conchae mastoid portion
ethmoidal sinuses mastoid process
petrous portion
sphenoid styloid process
body zygomatic process
greater and lesser wings
squamosal surface
pterygoid processes
sella turcica
sphenoidal sinuses
Facial bones:
maxillae mandible
alveolar margin alveolar margin
palatine process body
zygomatic process rami
maxillary sinus coronoid process
condyloid process
zygomatics mandibular notch
temporal process mandibular angle
orbital process
nasals
palatines
orbital process lacrimals
pyramidal process
nasal crest inferior nasal conchae
Ossicles (x2): {FAP Fig. 11-6}
malleus
incus
stapes
- Palpate the zygomatic arch. Which bones contribute to it?
- Palpate the nasion - the depression where the nasal bones meet the frontal bones. Palpate the inion - the depression immediately below the occipital protuberance. The nasion and the inion, together with the openings of the external auditory meatuses, are reference points used to clinically position EEG electrodes.
- What bone articulates with the vertebral column?
- Review the locations of the paranasal sinuses. Where does the connecting channel from each enter the nasal cavity?
- What bones and related structures contribute to the hard palate? To the nasal septum? To the nose?
- What is the collective function of the ossicles? Within which bone of the skull do they reside?
b) Identify the following sutures and associated fetal fontanels of the cranium on the adult and fetal skull models:
sutures:
midsagittal suture squamosal suture
coronal suture lambdoidal suture
frontal suture (fetal only)
fontanels (fontanelles):
anterior fontanel occipital fontanel
sphenoidal (ant. lateral) fontanel mastoid (post. lateral) fontanel
c) Identify the following fossae, foramina, and fissures of the skull:
Internal: External:
anterior fossa supraorbital foramina
olfactory fossae infratemporal fossa
olfactory foramina of the cribriform plate mandibular fossa
middle fossa orbital fossa
optic foramen optic foramen
superior orbital fissure superior orbital fissure
foramen lacerum (carotid canal) inferior orbital fissure
foramen rotundum nasolacrimal canal
foramen ovale infraorbital foramina
posterior fossa temporal fossa
internal auditory meatus external auditory meatus
jugular foramen mental foramina
hypoglossal canal internal nares (choanae)
foramen magnum
- What bones meet in the temporal fossae?
- What bones contribute to the orbital fossae?
- What bones articulate at the mandibular fossae?
d) For each of the fossae, try to identify what muscle(s) attach there or what brain structure rests there. For each of the foramina and fissures, identify what structures pass through.
Teeth {FAP Figs. 21-8, 21-9}
The teeth (dentition) are often studied with the digestive system, however, we will learn them as part of the head.
a) Identify and distinguish incisors, canines (cuspids), premolars (bicuspids), and molars (tricuspids) in the sample adult skulls and models.
- What are the distinguishing features of each? What role does each play in mastication (chewing)?
- What is the "dental formula" for an adult human? (#UI,#UC,#UP,#UM/#LI,#LC,#LP,#LM)
- What is the anatomical relationship between the upper teeth and the maxillary sinuses?
b) Study the emerged teeth and pre-emergent sockets in the infant skull model.
- What distinguishes deciduous (primary, baby) from permanent (secondary, adult) teeth?
- What is the dental formula for an infant human? (#UI,#UC,#UP,#UM/#LI,#LC,#LP,#LM)
Facial Muscles {FAP Figs.11-5 to 11-8; APL 10-1, Figs 10.2,10.3}
Facial muscles may be divided into muscles of mastication and the muscles of facial expression.
a) On the models and charts locate the following muscles of mastication and give their actions:
temporalis medial pterygoid
masseter lateral pterygoid
- Note that these muscles are innervated by the trigeminal nerve (NV), mandibular branch.
b) On the models and charts study the locate the following muscles of facial expression and give their actions:
occipitofrontalis orbicularis oris buccinator levator palpebrae
orbicularis oculi zygomaticus platysma depressor anguli oris
- Note that these muscles are innervated by the facial nerve (NVII).
- The levator palpebrae superioris raises the upper eyelid. This is also a muscle of facial expression, although it is innervated by the oculomotor nerve (NIII).
b) On the models and charts study the locate the following muscles of facial expression and give their actions:
occipitofrontalis orbicularis oris buccinator levator palpebrae
orbicularis oculi zygomaticus platysma depressor anguli oris
- Note that these muscles are innervated by the facial nerve (NVII).
- The levator palpebrae superioris raises the upper eyelid. This is also a muscle of facial expression, although it is innervated by the oculomotor nerve (NIII).
Meninges {FAP Figs. 14-2, 14-3; APL 13-1, Fig. 13.11, 13.12}
Within the skull and spinal column, the central nervous system is encased in three layers of connective tissue - the meninges. These serve the functions of protection, support, cushioning, and access for blood vessels.
a) Locate the outer dura mater on the prepared brains, models, and charts. Try to locate the following dural reflections:
falx cerebri falx cerebelli tentorium cerebelli
- What cortical structures does each of these dural reflections separate?
- Note that the cranial dura is two layers thick. The outer layer is continuous with the periosteum of the inner surface of the skull.
b) Locate the arachnoid membrane, the subarachnoid space, and the pia mater on the prepared brains (if possible).
- What fluid fills the subarachnoid space? Local enlargements of this space are called cisterns (see charts).
- Note that the dura and arachnoid only follow the major fissures of the brain, while the pia closely follows all of the surface convolutions. Blood vessels supplying and draining the brain travel in the pia.
Circulation of the Skull and Head
{FAP Figs. 12-21, 21-27; APL Figs. 13.11, 18.4, 18.5, 18.10, 18.11}
There are really two interconnected circulatory systems of the brain; one containing blood and the other containing cerebrospinal fluid (CSF).
a) Study the diagrams and (bad) model of the Circle of Willis {APL Fig 18.5}. Identify the following arteries in the prepared brains and models:
basilar posterior cerebrals posterior communicatings
vertebrals middle cerebrals anterior communicating
internal carotids anterior cerebrals
- What three arteries supply blood to the circle? Describe the course each takes through the neck and how it penetrates the skull.
- Branches of the basilar artery supply most of the lower brain structures. What regions are supplied by each of the cerebral arteries? How would you expect this anatomical specificity to manifest in behavioral and cognitive loss patterns seen following cerebrovascular accidents (CVAs), losses of blood supply (ischemias), and strokes?
- Note that the communicating arteries complete the circle. What advantage could this circular pattern convey for maintaining blood supply to all of the brain?
b) Small veins which run through the pia mater all terminate in a network of venous sinuses within the dural infoldings. Identify the following sinuses in the models and prepared brains (where possible):
superior sagittal sinus sigmoid sinus petrosal sinuses
inferior sagittal sinus sinus confluens cavernous sinuses
straight sinus transverse sinuses internal jugular veins
- Trace the sinus network to its common drainage into the internal jugular veins. By what route do these veins leave the skull?
c) From the diagrams in your text, locate the following external vessels on each side of the head and state which region each supplies of drains:
occipital artery and vein
(superficial) temporal artery and vein
maxillary artery and vein
facial artery and vein
external carotid artery
external jugular vein
d) The CSF {APL Fig, 13.6} is a blood plasma filtrate that is produced from arterial blood in the choroid plexus of the ventricles, circulates through the ventricular and subarachnoid spaces, and is reabsorbed through the arachnoid granulations into the venous blood of the sinuses. The known functions of the CSF include cushioning and nourishment. It also provides an indirect target for monitoring chemical makeup of the blood.
- We will be studying the ventricular system of the brain again with the rest of the central nervous system. For now, identify ventricles I & II (lateral ventricles), III, and IV, as well as the cerebral aqueduct on the ventricular system model. Identify the central canal on the spinal cord cross-section model.
- Trace the possible routes a tiny droplet of CSF might take on its journey from production in the choroid plexus of a lateral ventricle to reabsorption into the superior sagittal sinus. Note that some possible routes involve washing into and out of the "dead ends" of the central canal and subarachnoid space of the spinal cord.
- The CSF is circulated principally by the pressure difference between the capillaries of the choroid plexus and the venous sinuses , which are at subatmospheric pressure when you are standing. Yes, your brain really does suck. Sorry.
Guide to Histology
The only histology this week is the slide of an emerging tooth. {FAP Fig. 24-8}
On the emerging tooth slide, identify the following structures:
crown enamel organ (only in pre-emerged tooth)
neck enamel
root dentin
gingiva pulp cavity
periodontal ligament root canal
- What structures are found inside a healthy pulp cavity?
- What layer of the tooth is most similar to vascular, lamellar bone?
- What is the function of the "enamel organ"?
Guide to Physiology
There is no real physiological component to this week's lab.