Head and Neck: SCALP, MENINGES, SKULL

Which layers make up the acronym SCALP?

S = Skin, C = Dense Connective tissue, A = Aponeurosis, L = Loose areolar connective tissue, P = Periosteum / Pericranium

What are the main characteristics of the Skin layer of the scalp?

Thick, contains many sweat and sebaceous glands, and hair follicles

Where do the scalp muscles insert?

Directly into the Skin layer

What is the key vascular feature of the Dense Connective Tissue layer of the scalp?

It is a very vascular subcutaneous layer

What is the alternative name for the Aponeurosis layer of the scalp?

Galea Aponeurotica

What is the structure and location of the Epicranial Aponeurosis?

Central portion; a tendinous sheet covering the calvaria

Where does the Occipitalis muscle insert?

Onto the superior nuchal line

Which nerve supplies motor innervation to the Occipitalis muscle?

Posterior auricular branch of CN VII (Facial nerve)

Where does the Frontalis muscle insert?

Into the skin of the eyebrow and orbicularis oculi

Which nerve supplies motor innervation to the Frontalis muscle?

Temporal and zygomatic branches of CN VII (Facial nerve)

What is the function of the Loose Areolar Connective Tissue layer?

Allows free movement of the Scalp Proper

In which layer of the scalp are Emissary Veins located?

Loose (areolar) connective tissue layer

What do the Emissary Veins connect?

Cranial venous sinuses to extracranial veins

What role do Emissary Veins play in cerebral circulation?

Their communications help keep the pressure of blood in the venous sinuses constant

Which layer is known as the "Danger Area" of the scalp?

Loose (areolar) connective tissue layer

Why is the loose areolar connective tissue layer considered the danger area of the scalp?

It presents a potential path for the vascular spread of infection

What is the structure and attachment of the Pericranium / Periosteum?

Periosteum that is loosely attached to the bone

How are hematomas beneath the pericranium limited?

Subperiosteal hematomas are limited to each individual bone because the periosteum is attached at suture lines

What is the nature of the blood supply to the scalp?

Profuse blood supply

Why is it difficult to stop bleeding from a scalp wound?

Arterial walls are attached to fibrous septa in the subcutaneous connective tissue layer and are unable to contract or retract to allow blood clotting

Why is the tension of the epicranial aponeurosis important in scalp wounds?

If the aponeurosis is divided, tension causes the wound to gape open

What are the Meninges?

Three protective membranes that surround the brain and spinal cord

What are the three meningeal layers from outer to inner?

1. Dura Mater, 2. Arachnoid Mater, 3. Pia Mater

Where is the Extradural / Epidural space located?

Potential space between the inner aspect of the skull bone and the endosteal layer of the dura mater

Where is the Subdural space located?

Potential space between the dura mater and arachnoid mater

Where is the Subarachnoid space located, and what type of space is it?

ACTUAL space between the arachnoid mater and pia mater

What does the Subarachnoid space contain?

Cerebrospinal Fluid (CSF) and blood vessels supplying the brain

How many layers does the Dura Mater have?

Two layers: Endosteal layer and Meningeal layer

What is the Endosteal layer of the Dura Mater?

Periosteum covering the inner surface of skull bones

Does the Endosteal layer of Dura Mater extend into the spinal cord?

No, it does NOT extend through the foramen magnum to become continuous with the spinal cord dura mater

What is the Meningeal layer of the Dura Mater?

Dura mater proper; dense, strong fibrous membrane covering the brain

Does the Meningeal layer of Dura Mater extend into the spinal cord?

Yes, it is continuous through the foramen magnum with the dura mater of the spinal cord

How many septa does the meningeal layer send inward, and what is their function?

Sends inward 4 septa to divide the cranial cavity into spaces and restrict displacement of the brain during acceleration/deceleration

What is the shape and location of the Falx Cerebri?

Sickle-shaped fold of Dura mater in the midline between the two cerebral hemispheres

Where does the anterior end of the Falx Cerebri attach?

Attaches to the Frontal crest and Crista Galli

What is the shape and location of the Tentorium Cerebelli?

Crescent-shaped fold of Dura mater that roofs over the posterior cranial fossa and covers the upper surface of the Cerebellum

Which cerebral lobes are supported by the Tentorium Cerebelli?

Supports the Occipital lobes of the cerebral hemispheres

What is the shape and location of the Falx Cerebelli?

Small, sickle-shaped fold of Dura mater projecting forward between the two cerebellar hemispheres

Where does the Falx Cerebelli attach?

Attaches to the internal occipital crest

What is the shape and function of the Diaphragma Sella?

Small, circular fold of Dura mater that forms the roof for the Sella turcica

Which nerves provide general sensory supply to the Dura Mater?

Trigeminal nerve (CN V) and the first three Cervical nerves (C1-C3)

Which nerve innervates the Dura Mater ABOVE the tentorium cerebelli?

Trigeminal nerve (CN V)

Where is dural headache referred to when origin is ABOVE the tentorium?

Referred to the forehead and face

Which nerves innervate the Dura Mater BELOW the tentorium cerebelli?

Cervical nerves (C1-C3)

Where is dural headache referred to when origin is BELOW the tentorium?

Referred to the back of the head and neck

What is the arterial blood supply to the Dura Mater?

Middle Meningeal artery (branch of Maxillary artery)

What is the venous drainage of the Dura Mater?

Middle Meningeal vein into the Pterygoid plexus

What is the structure and position of the Arachnoid Mater?

Delicate, impermeable membrane lying between Pia mater (internally) and Dura mater (externally)

What space separates the Arachnoid Mater from the Dura Mater?

Subdural Space (potential space)

What space separates the Arachnoid Mater from the Pia Mater?

Subarachnoid Space (actual space filled with CSF)

What are Arachnoid Villi, and where are they most numerous?

Projections into venous sinuses; most numerous along the superior sagittal sinus

What are Arachnoid Granulations?

Aggregations of arachnoid villi

What is the structure and coverage of the Pia Mater?

Vascular membrane covered by flattened mesothelial cells; closely invests the brain covering Gyri and descending into Sulci

How does the Pia Mater relate to cranial nerves?

Extends over cranial nerves and fuses with the epineurium

How many total bones make up the human skull?

22 bones

How many bones make up the cranium?

8 bones

Which cranial bones are paired?

Parietal and Temporal

Which cranial bones are unpaired?

Frontal, Occipital, Sphenoid, and Ethmoid

How many bones make up the facial skeleton?

14 bones

Which facial bones are paired?

Palatine, Lacrimal, Maxilla, Nasal, Inferior nasal concha, and Zygomatic

Which facial bones are unpaired?

Vomer and Mandible

What is the definition of the Vertex on the skull?

Highest point on the cranium

What sutures intersect to form the Bregma?

Coronal suture and Sagittal suture

What sutures intersect to form the Lambda?

Lambdoid suture and Sagittal suture

Which bones meet at the Pterion?

Frontal bone, Temporal bone, Parietal bone, and Greater wing of sphenoid bone

Which sutures intersect to form the Asterion?

Parietomastoid suture, Occipitomastoid suture, and Lambdoid suture

What bones meet at the Nasion?

Frontal bone and Nasal bones

What is the future anatomical site of the Anterior Fontanelle?

Bregma

By what age does the Anterior Fontanelle typically close?

By 18 months old

What is the future anatomical site of the Posterior Fontanelle?

Lambda

When does the Posterior Fontanelle begin to close after birth?

Begins to close during the first few months after birth

What is a simple Filipino memory hook for Bregma vs. Lambda location?

Bregma for front (bandang harap), Lambda for back (likod)