The Scalp, Brain and Cranial Nerves Flashcards
What are the scalp layers?
SCALP mnemoic
skin
(dense) connective tissue
(epicranial) aponeurosis
loose connective tissue
pericranium
What does the skin contain?
where is it thickest?
Contains hair follicles, sweat & sebaceous glands;
Thickest over the occipital bone
What does the dense connective tissue contain?
Subcutaneous layer richly vascularised & with cutaneous nerves
What does the epicranial aponeurosis contain?
why is this layer important and what happens when it is compromised?
Tendon & muscle of occipitofrontalis; this layer prevents superficial wounds from gaping open;
when this layer is compromised (e.g. laceration), gaping wounds result that require sutures to close
What does the loose connective tissue contain and what does this allow
why may this be disadvantageous?
Loose areolar tissue (‘loose packing material’) that allows free movement of outer layers over underlying calvaria;
contains spaces susceptible to distension with fluid or infection spread (e.g. eyelids & root of nose)
What does the pericranium contain?
External periosteum of skull
What is important to regard between the aponeurosis and pericranium?
there are potential spaces for accumulation of fluid (e.g. blood) or spread of infection
▪ Fluid/infection can spread to the eyelids or root of nose
Why does the fluid/infection spread to eyelids or root of nose?
Frontal belly of occipitofrontalis inserts into skin & subcutaneous tissue not bone
posterior and lateral spread is limited due to the firm attachments of the occipital belly and temporal fascia.
How can scalp infections spread to intracranial structures?
via emissary veins
What is cutaneous/sensory innervation of scalp and face supplied by?
CN V (V1, V2, V3) & cervical nerves from C2 & C3
What branches of V1 provide cutaneous/sensory innervation?
Supraorbital
Supratrochlear
What branches of V2 provide cutaneous/sensory innervation?
zygomaticotemporal
What branches of V3 provide cutaneous/sensory innervation?
auriculotemporal
What is skin over angle of mandible supplied by?
not supplied by CN V, but by the cervical plexus with the great auricular nerve (C2 & C3)
What are the cervical nerves called that provide custaneous/sensory innervation to head?
C2 - Greater, Lesser Occipital
C3 - Third Occipital
C2,C3 - Great Auricular
What is the majority of the blood supply for the face and scalp from?
external carotid artery with some from the internal carotid artery
What are the main arteries of face and scalp?
internal carotid artery
- zygomaticofacial
- zygomaticotemporal
external carotid artery
- facial
- buccal (maxillary branch)
- mental (maxillary branch)
- infraorbital (maxillary branch)
- transverse facial (branch of superficial temporal)
Why is it easier to memorise branches of the internal carotid artery?
same name as nerves
Where can the pulse be taken?
from the facial artery at inferior border of mandible
or
from the transverse facial artery just anterior to the auricle
What is the venous drainage of the face?
- Facial vein drains most of the face to internal jugular vein
- Transverse facial vein drains some of the upper face
What is the danger triangle of the face?
no valves in external facial veins therefore blood flows in both directions
veins deep to danger triangle drain to cavernous sinus and skin infections in this area may spread an intracranial infections
What are the 3 means of lymphatic drainage of the face?
Where are they each?
Pre-auricular & Parotid: Near ear, from eyelids, lateral cheek, external nose
Submandibular: Follows facial artery, from medial orbit, external nose, medial cheek, upper lip, lateral lower lip
Submental: Inferior chin, from medial lower lip & chin
What are the lobes of the brain?
Frontal Lobe
Parietal Lobe
Temporal Lobe
Occipital Lobe
Insular Lobe
Limbic Lobe
What seperates the right and left lobes?
longitudina cerebral fissure
What seperates the frontal lobe from the parietal?
central sulcus
(fissure of rolando)
What seperates the frontal and parietal lobes from the temporal lobes?
lateral sulcus
What is the circle of willis?
circular anastomotic artery loop
Why is the circle of willis so important?
ensures that the brain has a consistent blood flow, even if one part of the arterial system is blocked or narrowed. It serves as a safety mechanism by allowing blood to flow from different arteries if one pathway is compromised.
Where do the vertebral arteries come from?
where do they enter the brain?
Right Subclavian Artery: Arises from the brachiocephalic trunk, which branches from the aorta.
Left Subclavian Artery: Directly branches off the aorta.
at the foramen magnum
What is the pathway of the circle of willis from the brainstem?
Vertebral Arteries → Basilar Artery → Posterior Cerebral Arteries (PCA) → Posterior Communicating Arteries → Internal Carotid Arteries →
Anterior Cerebral Artery (ACA) and Middle Cerebral Artery (MCA) → Anterior Communicating Artery (AComA).
What does the internal carotid bifurcate into?
middle cerebral
anterior cerebral
Where does each cranial nerve leave the base of the skull?
CN I Cribriform plate foramina
CN II Optic canal
CN III Superior orbital fissure
CN IV Superior orbital fissure
CN V1 Superior orbital fissure
CN V2 Foramen rotundum
CN V3 Foramen ovale
CN VI Superior orbital fissure
CN VII Internal acoustic meatus
CN VIII Internal acoustic meatus
CN IX Jugular foramen
CN X Jugular foramen
CN XI Jugular foramen
CN XII Hypoglossal canal
What nerves are purely sensory?
CN I (Olfactory): Smell (sensory).
CN II (Optic): Vision (sensory).
CN VIII (Vestibulocochlear): Hearing and balance (sensory).
What senses are purely motor?
CN III (Oculomotor): Eye movements, pupil constriction (motor).
CN IV (Trochlear): Eye movement (motor).
CN VI (Abducens): Eye movement (motor).
CN XI (Accessory): Head and shoulder movement (motor).
CN XII (Hypoglossal): Tongue movement (motor).
What is the role of CNI?
Sense of Smell/Olfaction (special visceral afferent)
olfactory
What is the role of CNII?
Sense of Sight/Vision (special somatic afferent)
What is the role of CNIII?
Motor: Eye Movements (general somatic efferent)
Parasympathetic (general visceral efferent)
What is the role of CNIV?
Motor: Eye Movements (general somatic efferent)
What is the role of CNV?
Sensation: Head & Cavities (general somatic afferent)
Motor: Muscles of Mastication (special visceral efferent)
Carrier of autonomic fibres
What is the role of CNVI?
Motor: Eye Movements (general somatic efferent)
What is the role of CNVII?
Motor: Muscles of Facial Expression (special visceral efferent)
Parasympathetic (general visceral efferent)
Anterior 2/3 Taste/Gustation (special visceral afferent) (chorda typani)
What is the role of CNVIII?
Hearing & Balance (special somatic afferent)
What is the role of CNIX?
General Sensation: (Posterior 1/3) Tongue & Oropharynx (general somatic afferent)
Parasympathetic (general visceral efferent)
Posterior 1/3 Taste/Gustation (special visceral afferent)
What is the role of CNX?
General Sensation: Pharynx & Larynx (general somatic afferent)
Parasympathetic Heart, Lungs, GI Tract (general visceral efferent)
Motor to Pharynx & Larynx (special visceral efferent)
What is role of CNXI?
Motor: Sternocleidomastoid & Trapezius
What is the role of CNXII?
Motor: Tongue (general somatic efferent)
What is subarachnoid space?
fluid filled space contains cerebrospinal fluid (CSF)
& blood vessels
What are the layers of meninges?
Dura, Arachnoid & Pia
What are granular foveolae found in the calvaria?
What is their role?
arachnoid granulations that return CSF back to venous circulation
What does the cavernous sinus drain into?
inferior petrosal > IJV
What sinuses drain into IJV?
- sigmoid sinus
- inferior petrosal sinus
- transverse sinus (drains into sigmoid)
