Week 3: Gross Anatomy of the Skull and Orbit Flashcards
What is a bone?
- Hard connective tissue
- Consists mainly of the skeleton of most vertebrates
- Organic component: cell and matrix
- Inorganic: minerals (e.g. calcium phosphate, calcium carbonate)
Function of bones?
- Support & protect the body
- Provide points of attachment & levers for muscles
- Reservoir for several minerals of the body
- Contains bone marrow
What are the two bone structures and explain their characteristics?
- Compact/Cortical (dense bone)
- Outer shell & surrounds spongy bone
- Softer in children - Spongy/Trabecular (cancellous)
- Inner part
- Consists of bone spicules and haemopoietic cells
What are the types of marrow and what do they contain?
- Red marrow
Contains: RBCs, platelets and most WBCs - Yellow marrow
Contains: some WBCs, fat cells, newborns do not contain these until 6-7 months
List the types of bones
- Long bones
- Short bones
- Flat bones
- Irregular bones
- Sesamoid bones
What is the shape of long bones and an example?
- Shape: tubular, have shaft between two heads
- E.g: femur (upper bone of leg)
What is the shape of short bones and an example?
- Shape: cuboidal (similar width & length)
- E.g: bones of wrist
What is the shape of flat bones and an example?
- Shape: flat & thin with two compact bone plates separated by spongy bone
- E.g: skull
What is the shape of irregular bones and an example?
- Shape: bones of various shapes
- E.g: facial bones
What is the shape of sesamoid bones and an example?
- Shape: round oval bones that develop within tendons
- E.g: patella (front of knee joint)
What are the two surrounding bones and describe their characteristics
- Periosteum
- External surface of the bone is covered with periosteum
- Outer layer consists of dense vascular connective tissue - Articular Cartilage
- white, smooth tissue that covers the surfaces of bones in joints
- allows joints to easily glide over each other
What is the blood supply process to the bone and its innervation?
Blood supply process:
- Adjacent arteries branches a nutrient artery that enters internal cavity of bone, suppling to marrow, spongy bone & inner layers of compact bone
- Periosteum receives blood from vessels that supply outer layers of compact bone
Name the cranium bones and how many there are
- Frontal x1
- Parietal x2
- Occipital x1
- Temporal x2
- Sphenoid x1
- Ethmoid x1
What does the cranium contain? (hint: 4)
- Brain
- Meninges (dura mater, pia mater & arachnoid)
- Blood vessels
- Nerves
- 12 cranial
- Sympathetic & parasympathetic nerves
- Vessels & nerves pass through foramina
Define sutures?
- Immovable joints found between bones in people aged around > 14 months
- Narrow seams of fibrous connective tissue
Name all the sutures
- Coronal suture
- Sagittal suture
- Lambdoid suture
Name CNI, the location, type (sensory/motor nerve) and function
- Name: Olfactory
- Location: travels through cribriform plate of the ethmoid bone
- Type: sensory
- Function: sense of smell
Name CNII, the location, type (sensory/motor nerve) and function
- Name: optic
- Location: travels through the optic foramen
- Type: sensory
- Function: sense of vision
Name CNIII, the location, type (sensory/motor nerve) and function
- Name: oculomotor
- Location: travels through the superior orbital fissure
- Type: motor
- Function: eye movement
Name CNIV, the location, type (sensory/motor nerve) and function
- Name: trochlear
- Location: travels through the superior orbital fissure
- Type: motor
- Function: eye movement - intorsion, depression & abduction
Name CNV, the location, type (sensory/motor nerve) and function
- Name: trigeminal
- Location: travels through the superior orbital fissure - 3 branches: ophthalmic division (v1), maxillary (v2), mandibular (v3)
- Type: both
- Function: facial motor & sensory
Name CNVI, the location, type (sensory/motor nerve) and function
- Name: abducens
- Location: travels through the superior orbital fissure
- Type: motor
- Function: eye movement
Name CNVII, the location, type (sensory/motor nerve) and function
- Name: facial
- Location: travels through internal auditory canal
- Type: both
- Function: facial & motor sensory
Name CNVIII, the location, type (sensory/motor nerve) and function
- Name: vestibulocochlear
- Location: travels through internal auditory canal
- Type: sensory
- Function: audiotory & balance
Name CNIX, the location, type (sensory/motor nerve) and function
- Name: glossopharyngeal
- Location: travels through jugular foramen
- Type: both
- Function: oral sensation & taste
Name CNX, the location, type (sensory/motor nerve) and function
- Name: vagus
- Location: travels through jugular foramen
- Type: both
- Function: sensory, motor & parasympathetic
Name CNXI, the location, type (sensory/motor nerve) and function
- Name: accessory
- Location: travels through jugular foramen
- Type: motor
- Function: neck & head turning
Name CNXII, the location, type (sensory/motor nerve) and function
- Name: hypoglossal
- Location: travels through hypoglossal canal
- Type: motor
- Function: moving tongue
Name the floors of the cranium
- Anterior cranial fossa
- Middle cranial fossa
- Posterior cranial fossa
What are the borders and important landmarks for anterior cranial fossa?
- Borders: frontal bone, lesser & greater wing of sphenoid, ethmoid bone
- Important landmarks: contains frontal lobes of cerebral hemispheres
What are the borders and important landmarks for middle cranial fossa?
- Border: lesser & greater sphenoid, temporal bones, parietal bones
- Important landmarks:
pre-chiasmatic sulcus, sella turcica: pituitary gland located in it, cavernous sinus
What are the borders, contents and important landmarks for posterior cranial fossa?
- Borders: dorsum sellae of sphenoid, occipital bone, temporal bone
- Important landmarks: foramina magnum, jugular foramen, hypoglossal canal, internal audiotory canal
- Contents: cerebellum, pons, medulla oblongata
Name the fourteen facial bones and how many
- Zygomatic x2
- Maxilla x2
- Nasal x2
- Lacrimal x2
- Vomer x1
- Palatine x2
- Inferior conchae x2
- Mandible x1
Name the orbital margins and what they are formed by
- Supra-orbital margin: frontal bone
- Infra-orbital margin: zygomatic bone (laterally), maxilla (medially)
- Lateral margin: frontal process of zygomatic, zygomatic process of frontal
- Medial margin: maxillary process of frontal bone, lacrimal process of frontal bone
Name the bones consisting of the roof of orbit and its strength
- Consisting of: lesser wing of sphenoid & frontal bone
- Strength: thin & fragile
Name the bones consisting of the floor of orbit and its strength
- Consisting of: zygomatic bone, maxilla, palatine bone
- Strength: weakest wall
Name the bones consisting of the medial wall of orbit and its strength
- Consisting of: lesser wing of sphenoid, ethmoid bone, maxilla
- Strength: very thin
Name the bones consisting of the lateral wall of orbit and its strength
- Consisting of: greater wing of sphenoid, frontal bone, zygomatic bone
- Strength: thickest wall
List what paranasal sinuses is lined with, filled with and its functions
- Lined with mucoperiosteum
- Filled with air: lightens the skull
- Functions: crumple zone to protect vital structures & increases speech resonance
What are the three opening into the orbital cavity and describe what it transmits and supplies
- Infraorbital groove
- Contains infraorbital nerve
- Becomes infraorbital canal as it passes through maxilla
- Infraorbital nerve emerges from infraorbital foramen - Anterior ethmoidal foramen
- Transmits: anterior ethmoidal nerve, vein & artery
- Supplies: anterior & middle ethmoidal sinuses, frontal sinuses, lateral nasal wall & nasal septum - Posterior ethmoidal foramen
- Transmits: posterior ethmoidal nerve, vein & artery
- Supplies: posterior ethmoidal & sphenoid sinuses
What causes blow out fracture of the orbit, its symptoms and results
- Cause: blunt trauma to or around the eye, coughing or sneezing (rare)
- Symptoms: diplopia, gaze restrictions
- Result: can lead to extraocular muscle entrapment resulting in restriction on upgaze or downgaze
What are the structures surrounding the orbit?
- Superior: frontal sinus, anterior cranial fossa
- Medial: ethmoidal sinus
- Inferior: maxillary sinus
Describe periorbital and its function?
- Layer of thick connective tissue lining the orbit
- Loosely attached to the underlying bone except at the orbital margin, edges of fissures and foramina
- Functions: serves as attachment sites for muscles, tendons and ligaments to the orbital bone
support structure for blood supply
Describe orbital septum and its function?
- Continuous at orbital margin with periorbita
- Circular sheet from rim of orbit to tarsal plate
- Functions: prevent facial infection from entering the orbit
keeps orbital fat tissue in place
