Exam II

Cranium

skeleton of the head

How many named bones does the cranium have?

22

How is the cranium divided?

Into two parts: the neurocranium and viscerocranium

Neurocranium

Bony case of the brain and its membranous coverings (meninges)

Neurocraniums is formed by:

8 bones: 4 singular frontal, ethmoidal, sphenoidal, occipital, 2 pairs temporal, and parietal 

Consequences of a blow to the superciliary arch?

laceration and black eye

Sinuses are what type of cells

Pneumatic cells

Sinuses-function

decrease weight of skull and allow air through nose to be clean

Viscerocranium

Forms the anterior part of the cranium (face)

Viscerocranium consists of:

15 irregular bones: 3 singular mandible, ethmoid, vomer, 6 pairs maxillae, inferior nasal conchae, zygomatic, palatine, nasal, lacrimal

Malar flush

redness of the skin over the zygomatic prominence. Associated with Fever, tuberculosis, and Lupus

Maxillae

Pair of bones fused together that holds your upper teeth, shapes your cheek area, and forms the floor of your eye sockets and the roof of your mouth.

Foramen magnum

large opening at the base of the skull that allows the spinal cord to connect with the brain.

Le Fort I fracture

horizontal fractures passing superior to the maxillary alveolar process (sockets contain upper teeth)

Le Fort II fracture

passes the posterolateral parts of the maxillary sinuses to the bridge of the nose

Le Fort III fracture

horizontal fracture passing through the superior orbital fissures and other bones

All Le Fort Fractures are

horizontal

What type of fracture?

Le Fort I

What type of fracture?

Le Fort II

What type of fracture?

Le Fort III

Mandible

houses the lower teeth, forms the chin, and is the only freely movable bone in the face

Mandible function

chewing, shape, and speech

Fractures of the ____ usually occur in pairs, frequently on opposite sides.

mandible

Extraction of the teeth causes

reabsorption of the alveolar bone

Fractures of the coronoid process happens usually

simultaneously on both sides

Fractures of the coronoid process or neck of the mandible occur by:

Fall on chin, punch, trauma, or vehicular trauma

What happens when the mandible shrinks?

It leaves the mental foramen open and the nerves exposed to pain

How does mandible shrinkage occur?

Dentures or crystal meth

Dura

• Firmly attached to the bone in the cranial base

• Outer layer of meninges (periosteal layer)

Dura- function

Protects brain, stabilizes position, supports blood circulation

How can the dura detach from the head?

blow to the head or fracture of the skull

In a blow to the head the periosteal layer of the dura matter detaches from the

clavaria

A fracture that tears the dura results in

leakage of CSF - will come out from nostrils (rhinorrhea)

The skin of the scalp is normally ____ bearing

hair

What type of tissue is the scalp and what does it cover?

Subcutaneous tissue that covers the neurocranium from the superior nuchal lines on the occipital bone to the supra-orbital margins of the frontal bone

Scalp-function

Laterally, the scalp extends over the temporal fossa to the zygomatic arches

How many layers does the scalp have?

5

Describe first three layers of scalp

First three are connected intimately and move as a unit - skin, connective tissue, aponeurosis (SCA)

List the layers of the scalp from outermost

1. Skin

2. Connective tissue (dense)

3. Aponeurosis

4. Loose connective tissue

5. Pericranium

Superficial scalp wound do not gape open due to

the strength of the epicranial aponeurosis

Aponeurosis wounds

Gape widely (lacerate epicranial aponeurosis)  - blood or pus spreads easily in the loose areolar layer of the scalp (4th & 5th layers), and may pass anteriorly into the eyelids → black (racoon) eyes 

What are meninges?

Membranous coverings of the brain that lie immediately internal to the cranial 

Epidural space

space between bone and top of the dura

What are the layers of the meninges?

• Dura matter

• Subdural space

• Arachnoid

• Sub arachnoid space

Subarachnoid space

contains CSF

Meninges- function

• Protect the brain 

• Form the supporting framework for arteries, veins, and venous sinuses (vasculature for brain that take blood out)

What is cerebral-spinal fluid (CSF)

clear, colorless liquid that circulates through the brain's ventricles and around the spinal cord

Extradural or epidural hemorrhage originates

in an artery, typically the middle meningeal artery

How does an extradural or epidural hemorrhage occur

blow to the head

What happens when an extra dural or epidural hemorrhages occurs

The patient feels very sleepy, blood accumulates in the extradural hematoma, forces the brain through the foramen magnum (herniation) of midbrain sections → death

Dura matter

tough, thick external fibrous layer

Dura matter innervation

CN V (trigeminal) in the anterior and middle cranial fossae and by the CN X (vagus) in the posterior cranial fossa

Dura matter- function

anchors the brain to the skull and compartmentalizes it to stop the brain from moving too much when you move

May headaches originate in the ____, which is sensitive to pain caused by stretching of the meninges

dura mater

Dural border hematoma (subdural hematoma)- caused by

Caused by extravasated blood between the dura and arachnoid, typically from tearing of a cerebral vein

Arachnoid matter

• thin intermediate layer

• looks like a spider web

Arachnoid matter- function

acts as a bridge for the layer underneath it. It creates the subarachnoid space which is filled with cerebrospinal fluid (CSF)

Inflammation of the Leptomeninges results from

pathogenic organisms

Subdural hematoma- treatment

burr holes, done to drain blood from the space between the dura mater and the arachnoid mater.

A subarachnoid hemorrhage usually occurs from

an aneurysm or HTN

Pia matter

delicate internal vasculated layer

Pia matter- function

blood vessels to the brain to supply it with oxygen and nutrients. It also helps seal the brain to contain cerebrospinal fluid

What are the leptomeninges

pia matter and arachnoid matter

Dural venous sinuses

Endothelium-lined spaces between the periosteal and meningeal layers of the dura.

Dural venous sinuses- location

From where the dura septa attach along the free edge of the falx cerebri and in relation to formations of the cranial floor

Dural venous sinuses- function

Large veins from the surface of the brain empty into these sinuses and most of the blood from the brain usually drains through them into the internal jugular veins 

Examples of dural venous sinuses

Cavernous sinus and Sigmoid Sinus

Infections may pass from the facial veins into the ____ ___ via the superior ophthalmic veins or the vertebral venous plexus into the dural sinuses

cavernous sinus

Triangle of death (or danger triangle)

An area of the face where infection may produce inflammation of the facial vein which can spread to the cavernous sinus, causing infected brain tissue

Fractures of the cranial base could case what artery to tear

internal carotid artery (circle of Willis)

What does a tear of the internal carotid artery through the cavernous sinus cause?

compression of CN VI (abducens: look to the side) and/or structure in the wall of the of the sinus, which includes CNs III, IV, V1 and V2 which affect eye movement and extra ocular muscles

Tentorial notch

Concave gap in the free anteromedial border of the tentorium cerebelli which the brainstem extends from the posterior into the middle cranial fossa

Tentorial notch- function

opening before the cerebellum that allows brain to continue as the spinal cord

An inflamed cerebellum can cause

Parts of the temporal lobe to herniate through the tentorial notch

What happens if the tentorium lacerates the temporal lobe

Damage to the oculomotor nerve causing paralysis of extraocular muscles

Pituitary (master gland)  tumors or enlargement may extend superiorly through

sellar diaphragm

Pituitary (master gland)  tumors or enlargement can cause _____ disturbance

endocrine

Brain

Delicate structure enclosed in a rigid cranium, surrounded by meninges

List 4 structures of brain

• Cerebrum

• Cerebellum

• Brain stem

• Diencephalon

List ways brain can be damaged

• blow to the head

• compressed by a tumor (benign or malignant)

• deprived of oxygen (by leak or clot of blood in one of the cerebral arteries - thrombosis or embolism)

Cerebral concussion

Loss of consciousness after a head injury

Cerebral contusion

Results when the pia is stripped from the surface of the brain (bruising brain tissue), allowing blood to enter the subarachnoid space (blow to head: sports → concussion)

Cerebral lacerations result in

bleeding into the brain, causing compression → herniation

Cerebrum composed of:

• Two hemispheres with 4 lobes each

  • Gyri and sulci

_____ has more neurons than any other part of brain

The cerebellum

Cerebrum- function

memory, reasoning

Cerebellum-function

coordination, balance

Brain stem

• contains autonomic centers

  • Midbrain, pons, medulla obloganta

Brainstem- function

regulates involuntary, life-sustaining functions like breathing, heart rate, and blood pressure

Diencephalon

midbrain

Corpus Collosum

connects right and left hemispheres

Diencephalon-function

brain's primary relay, processing, and integration center. It bridges the nervous and endocrine systems, controlling sensory perception, motor functions, autonomic regulation, circadian rhythms, and homeostasis

Where can CSF be obtained

 from the posterior cerebellomedullary cistern through a cisternal puncture

CSF creation pathway

Ependymal cells →  lateral ventricles → CSF

CSF is produced initially in the

lateral ventricles

CSF function

acts as a shock-absorbing cushion to protect the central nervous system, delivers vital nutrients, and removes cellular waste

Hydrocephalus

excessive CSF dilates the ventricles, thins cerebral cortex, and separates the bones of the calvaria in infants

Treatments for hydrocephalus

1. Cisternal Puncture

2. shunt/valve take fluid from affected ventricle subdermally into abdominal cavity

How to diagnose hydrocephalus

transillumination or MRI

Brain accounts for ____ of body weight but receives about ___ of the cardiac output and ___ of the oxygen consumed by the body at rest

2.5%, 1/6, 1/5