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Flashcards in 1 - Anatomy & Embryology Deck (11)
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1
Q

Orbital Landmarks

Whitnall’s Tubercle

Distances of optic canal and ethmoid foramen

A

Whitnall’s Tubercle

  • 1cm inferior and 0.5cm deep from ZF suture
  • Lockwood suspensory ligament
  • Lateral check ligament
  • Lateral canthal ligament
  • Lateral limb of Levator palpebrae superioris

Distances

  • From anterior lacrimal crest
    • 24mm - Anterior ethmoidal foramen
    • 36mm - 12mm from Ant eth f. - Posterior ethmoidal foramen
    • 42mm - 6mm from Post eth f. - Optic canal
2
Q

Orbital Anatomy

Orbital volume
Globe volume
Anterior chamber volume
Age which orbit stop growing

A

Clinical head and neck anatomy for surgeons

  • Orbital volume - 30cm2
  • Globe volume - 6-7cm2
  • Inferior orbital foramen - 5-10mm below inferior rim
    • T.Turvey - 5mm
    • B.Evans - 7-10mm
      *
3
Q

Marginal Mandibular Nerve Anatomy

A
  • Dingman and Grabb
    • 100 facial halves
    • Relationship with inferior border of mandible
      • 81% above
      • 19% below - 1cm lowest point
    • Relationship to:
      • Facial artery
        • 0% below lower border anterior to Artery
        • Can deep or superficial to the Facial Artery
      • Facial vein
        • 98% Superficial to Posterior facial vein (Anterior limb of Retromandibular vein)
        • 100% Superficial to Anterior facial vein (Facial vein)
    • Branches
      • 21% - Single
      • 67% - 2 Branches
      • 9% - 3 Branches
    • Anastomoses
      • 5% - with Buccal branches
  • Ziarah and Atkinson
    • 110 facial halves
    • Relationship to lower border of mandible
      • 0.6cm to 1.2cm below
    • Relationship to:
      • Facial Vein
        • 100% superficial to Facial vein
      • Facial Artery
        • 53% below the lower border of mandible
        • 6% continued up to 1.5cm anterior to Facial Artery
    • Branches
      • 35% - Single
      • 53% - 2 Branches
      • 11% - 3 Branches
    • Anastomoses
      • 8% - with Buccal branches
4
Q

Facial Nerve Localisation

A

Facial Nerve Localisation

  • Advantages vs Disadvantages
    • Anterograde
      • Methodical
      • Trunk identified and protected
      • All peripheral branches are identified
    • Retrograde
      • Small peripheral lesion in parotid gland
      • Limited dissection
        • Lower drain output -> shorter inpatient stay
        • Less chance of Facial nerve trunk injury
      • Useful in patients who have already had a superficial parotidectomy
  • Antegrade
    • Tragal Pointer
      • 1cm inferior and 1cm deep
      • Soft tissue landmark - less reliable
    • Typanomastoid suture
      • 2-5mm inferior to the suture
      • The suture will lead to the Stylomastoid Foramen
      • Palpate the suture - finger will point towards the nerve trunk
    • Posterior belly of Digastric
      • Facial nerve exits just deep and medial to the PBD
        Classically lies in the same plane
  • Retrograde
    • Posterior auricular branch - Keefe 2009
      • Overlies the mastoid process, deep to fat
      • Relatively large nerve and easy to identify
    • Buccal Branch
      • Runs parallel to and 1cm below the zygomatic arch diverging distally towards the corner of the mouth
      • Parotid duct runs just inferior to the buccal branch
    • Marginal mandibular
      • Lies within 1cm of the angle of the mandible as it exits the parotid gland
      • Lies within a few mm of the anterior communicating vein of the retromandibular as it exits the tail of the parotid
5
Q

Orbital Complication

A

Blindness

  • Ord 1981
    • 3:1000
    • Retinal artery spasm or ischaemia from compression from oedema
6
Q

Orbital bony anatomy

Bones
Fissures
Fissure Contents

A

Bones of the orbit

  • Lacrimal
  • Sphenoid
  • Ethmoid
  • Frontal
  • Maxilla
  • Zygoma
  • Palatine

Superior orbital fissure

  • Bones
    • Greater and Lesser wings of the sphenoid
    • Maxilla
  • Contents
    • Within the Common tendinous ring
      • Nerve
        • III
          • Superior branch of Oculomotor
          • Inferior branch of Oculomotor
        • V1
          • Nasociliary
        • VI
    • Outside the Common tendinous ring
      • Nerve
        • III
        • IV
        • V1
          • Lacrimal nerve
          • Frontal nerve
      • Vein
        • Superior ophthalmic vein

Inferior orbital fissure

  • Bones
    • Zygoma
    • Maxilla
    • Palatine
    • Ethmoid
  • Bisected by the infra-orbital nerve fissure
    • Laterally the IOF communicates with the Infra-temporal fossa
    • Medially the IOF communicates with the Pterygopalatine fossa
  • Contents
    • Nerve
      • Zygomatic nerve
    • Vein
      • Inferior ophthalmic vein
7
Q

Orbital Anatomy - Eyelid & Canthal attachment

Eyelid anatomy

Whitnall’s ligament

Medial Canthal Attachment

Lateral Canthal Attachment

A

Upper eyelid

Lower eyelid

Tasal plates

  • Upper tarsal plate - 10mm
  • Lower tarsal plate - 5mm
8
Q

Lingual Nerve Position at 3rd Molar Region

A
9
Q

Sinus Embryology

A
  • Development
    • Maxillary, Ethmoid and Frontal sinus develops from invaginations of the nasal cavity
    • Spenoid sinus froms from the closure of the spheno-ethmoidal recess
  • Pneumatization
    • Primary pneumatization
      • Initial invagination of the sinus by mucosal cells
    • Secondary pneumatization
      • Expansion and growth of the sinus
      • NB: Some sources say sinuses are not present until an air filled cavity occurs (secondary pneumatization)
        Does not mean primary pneumatization has not occured
  • Maxillary Sinus
    • Primary pneumatization
      • 3rd month in utero
      • Invagination of the ethmoid infundibulum into the lateral walls of the middle meatus
    • Secondary pneumatization
      • Grows to maximum size until mid teens
  • Frontal Sinus
    • Primary pneumatization
      • 4th month in utero
      • Develops from two independent spaces
        • Expansion of the ethmoid sinus into the Frontal bone
        • Invagination of the middle meatus of the nasal passage
    • Secondary pneumatization
      • Grows to maximum size until mid teens
  • Ethmoid Sinus
    • Primary pneumatization
      • 4th month in utero
    • Secondary pneumatization
      • Grows to maximum size until mid teens
  • Sphenoid Sinus
    • Primary pneumatization
      • No primary pneumatization
      • Forms by constricting the posterosuperior portion of the spheno-ethmoidal recess
    • Secondary pneumatization
      • 2 - 3 yrs of age until mid teens
10
Q

Skin Layers

A
  • Epidermis
    • Stratum basale
      • Contains the only keratinocytes capable of dividing
    • Stratum spinosum
      • Keratinocytes become spiny shaped
      • Langerhans cells and immune active cells are located in this layer
    • Stratum granulosum
      • Keratinocytes loose their nucleus and cytoplasm and appear granular
    • Stratum lucidum
      • Typically only found in the thicker parts of skin - palms & soles
    • Stratum corneum
      • Anucleated cells filled with keratin
      • Barrier function of the epidermis
  • Dermis
    • Papillary Dermis
      • Provides nutrients to the epidermis
      • Contains rich plexus of vessels
    • Reticular Dermis
      • Serves to strengthen the skin and provide it with elasticity
      • Exocrine glands, Sebaceous glands and nerve endings are found within this layer
11
Q

Salivary Gland Anatomy and Physiology

A
  • Anatomy
    Three subunits of a salivary gland
    • Acinus
      • Serous - Parotid mostly serous
      • Mucous - Sublingual and Minor salivary glands
        • von Ebner Glands - Serous (Amylase)
      • Mixed - Submandibular gland
    • Secretory duct
      • Intercalated ducts - Leading from the acini to the striated duct
      • Striated ducts -
    • Collecting duct
  • Salivary Production
    • Electrolytes are actively transported under neuronal and hormonal control
      Fluid is osmotic
    • Hypotonic
    • Salivary flow
      • Unstimulated: 0.1-0.3mL/min
        Forms 10-20% of daily saliva production
        • Submandibular gland accounts for 70% of unstimulated production
      • Stimulated: 0.2 - 7mL/min
        ​Forms 80-90% of daily saliva production
        • Parotid gland accounts for 2/3rd of stimulated saliva production
      • Sublingual and Minor salivary glands are both spontaneous secretors
        Produces a continuous flow of mucus in the absence of neural stimuli