Download BIOL 4260 Human Evolutionary Anatomy Lecture 16: Cranial

BIOL 4260
Human Evolutionary Anatomy
Lecture 16: Cranial Development and Anatomy
Lecture 2: Fossil Record
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3/30/16
The Adult Skull
Conserved Development
later
early
Similar Composition
Dermal bone, cartilaginous bone, branchial arch cartilage
Segmentation
Segmentation clock for somite production
Final #s
4 occipital
8 cervical
12 thoracic
5 lumbar
5 sacral
4 (10)
coccygeal
Also 7 somitomeres (rudimentary
cranial somites)
Skeletal Formation
•  Skull bones formed
through endochondral
and intramembranous processes
•  Embryonic sources: occipital somites
(paraxial
mesoderm), pharyngeal arches & neural crest
cells
•  Membrane or dermal bone forms cranial
vault, most of face, and jaws
•  Chondrocranium – cartilaginous precursor
forms cranial base, protects brain & sensory
organs (nose, ear)
Cranial and Facial Subdivisions of the Skull
SKULL
FACE
14
CRANIUM
8
Maxillae
2
Occipital bone
1
Palatine bones
2
Parietal bones
2
Nasal bones
2
Frontal bone
1
Inferior nasal
conchae
2
Temporal bones
2
Sphenoid
1
Ethmoid
1
Zygomatic bones
2
Lacrimal bones
2
Vomer
1
Mandible
1
ASSOCIATED BONES 7
Auditory ossicles
enclosed in
temporal bones
(detailed in
Chapter 18)
Or . . . . .
Hyoid bone
6
1
Divisions
Vault:
neurocranium
} Face, mandible:
Base:
basicranium or
chondrocranium
viscerocranium
Intramembranous
@ ~ 8 wks, mesenchymal cells migrate and clump
Within the membrane, osteoblasts secrete osteoid – (collagen
fibers and other proteins) that mineralizes into spicules
Enlarges by addition of new outer layers and resorption of inner
surfaces
Chondrocranium/
Basicranium
Endochondral ossification
}
Sclerotomes
from occipital
somites
Cartilage
Bone
medial
lateral
Rapid increase in cranial size
during second trimester
Cranial capacity at birth approx. 360-400 cc
45 bones, approx. 110 ossification centers
Skull @
52 Weeks
Developmental Defects
Premature closure of
sagittal suture
More Segmentation: 5
Pharyngeal Arches
Gill (Branchial) Arches
Arches, Clefts & Pouches
Mesoderm
& neural
crest cell
core
Arch
1
Skeleton
Zygomatic, part of
Temporal,Malleus,Incus,
Mandible
2
Stapes, Styloid process,part of
hyoid
3
Muscles
Rest of hyoid
Nerve
CN V-Trigeminal
Mastication (4),Mylohyoid,
Anterior Digastric, Tensors (2)
Facial Expression (7),Posterior
(Max & Mand
Divisions)
CNVII - Facial
Digastric, Stylohyoid,Stapedius
Stylopharyngeus
CN IX Glossopharyngeal
4
Laryngeal cartilages
Pharyngeal
constrictors,
cricothyroid, Levator v.p.
6
CN X - Vagus
(Superior laryngeal
branch)
CN X - Vagus
Laryngeal cartilages
Intrinsic Laryngeal ms.
(Recurrent laryngeal
branch)
Fate of Spaces
• 5 pharyngeal pouches and 4
clefts
• First pouch meets first cleft
to form ear spaces:
cleft- external auditory meatus,
pouch- tympanic cavity and
eustachian tube
Facial Development
Pharyngeal arches form:
5 prominences
(processes) form (mostly
neural crest)
Nasal pit & palate form
Processes & palate fuse
4-10 wks,prominences/processes
enlarge, form nasal pit, eventually
fuse
Tongue Development
Tongue buds from arches 1,
3, 4 - form mucosa; muscles
from somites and mesoderm
Putting it all together: The Adult Skull
The Skull and Associated Bones
The skull consists of 22 bones
•  Cranium (aka braincase: neuro-+
basicranium)
–  8 individual cranial bones
•  Face (viscerocranium)
–  14 individual facial bones
Skull Associated bones:
•  7 individual bones (ossicles,
hyoid bones)
Cranial Bones
Facial Bones
Nasal bone
Lacrimal
bone
Frontal
bone
Zygomatic
bone
Maxilla
Vomer
Sphenoid
Parietal bone
Temporal
bone
Ethmoid
Mandible
Occipital
bone
Functions of The Cranial Bones
•  Overall Functions
–  Surround and protect brain
–  Blood vessels, nerves and connective tissue attached
to its inner surface
–  Outer surface provides extensive area for attachment
of muscles that move eyes, jaws and head
Functions of the Facial Bones
Overall Functions
–  Protect and support entrances to the digestive and
respiratory tracts
–  Actively Involved in respiration and mastication
–  Superficial facial bones provide areas for attachment
of muscles that control facial expression
Sutures of the skull
•  Flat bones of the skull connected by special immovable
joints named called sutures
•  Five major ones are:
– 
– 
– 
– 
– 
Lambdoid suture (λ)
Sagittal suture
Coronal suture
Squamous suture
Frontonasal suture
Figure 6.3b The Adult Skull
Occipital
bone
Occipital
bone
Lambdoid
suture
Right
parietal
bone
Left
parietal
bone
Sagittal
suture
Right
parietal
bone
Left
parietal
bone
Coronal
suture
Frontal
bone
Zygomatic
bone
Nasal bones
Superior view of the bones
of the adult skull
Frontal
bone
Figure 6.3c The Adult Skull (Part 1 of 2)
Coronal suture
Parietal bone
Superior temporal line
Frontal bone
Inferior temporal line
Sphenoid
Supra-orbital foramen
Squamous suture
Frontonasal suture
Nasal bone
Temporal
bone
Lambdoid suture
Lacrimal groove of lacrimal bone
Ethmoid
Infra-orbital foramen
External acoustic
meatus
Occipital bone
Maxilla
Zygomatic bone
Mastoid process
Styloid process
Zygomatic
arch
Mandible
Zygomatic process of temporal bone
Temporal process of zygomatic bone
Lateral view of the bones of the adult skull
Mental foramen
Mental protuberance
Occipital Bone
•  Foramen magnum
•  Occipital condyles
•  Site of attachment
for neck muscles
and nuchal
ligament
Frontal Bone
•  Forms
–  Forehead
–  Roof of orbit
–  Frontal sinuses
Temporal Bone
•  Contribute to zygomatic
arches
•  Form the only
articulation with the
mandible
•  Protect the sense
organs of inner ear
•  Divisions:
–  squamous
–  tympanic
–  petrosal parts
The facial bones (viscerocranium)
SKULL
FACE
14
CRANIUM
8
Maxillae
2
Occipital bone
1
Palatine bones
2
Parietal bones
2
Nasal bones
2
Frontal bone
1
Inferior nasal
conchae
2
Temporal bones
2
Sphenoid
1
Ethmoid
1
Zygomatic bones
2
Lacrimal bones
2
Vomer
1
Mandible
1
ASSOCIATED BONES 7
Auditory ossicles
enclosed in
temporal bones
(detailed in
Chapter 18)
Hyoid bone
6
1
The Maxillae
–  Make up the upper jaw
–  Upper teeth anchored to
maxilla
–  Articulate with all other
facial bones except the
mandible
–  Maxillary sinuses
•  Largest sinuses in head
–  Palatine process of maxilla
forms most of hard palate
•  This is the anterior part
of hard palate
Figure 6.12ac The Maxillae
Maxillary sinuses
Alveolar
process
Frontal process
Zygomatic
process
Lacrimal groove
Orbital surface
Infra-orbital foramen
Palatine bone
(horizontal
plate)
Incisive
canals
Anterior nasal spine
Body
Palatal process
of right maxilla
Alveolar
process
Right maxilla, anterior
and lateral surfaces
Superior view of a horizontal section
through both maxillae and palatine
bones
Palatine Bones
•  Form posterior part of
hard palate
The mandible
The mandible
•  Form the entire lower jaw
•  Head articulates with mandibular fossa of temporal
bone to form the temporal mandibular joint (TMJ)
•  Roots of lower teeth present in alveolar part
The Hyoid Bone
•  Does not articulate with any other bone
•  The inferior portion is connected to the
thyrohyoid ligament
•  The superior portion is suspended from the
mandible via muscles
– Stylohyoid muscle
– Digastric muscle
Styloid process
(temporal bone)
Masatoid process
(temporal bone)
Mandible
Digastric muscle (anterior belly)
Stylohyoid ligament
Greater horn
Stylohyoid muscle
Lesser horn
Thyrohyoid ligament
Thyroid
cartilage
Digastric muscle
(posterior belly)
Anterior view showing the relationship of the hyoid bone
to the skull, the larynx, and selected skeletal muscles
The Hyoid Bone
•  Bony projections of the hyoid bone
– Greater horn
– Lesser horn
– Body
Frontal belly of
occipitofrontalis
Epicranial
aponeurosis
Corrugator
supercilii
Temporoparietalis
(cut and reflected)
Temporalis
(temporoparietalis
removed)
Temporalis
Orbicularis oculi
Procerus
Nasalis
Zygomaticus
minor
Levator labii
superioris
Zygomaticus
major
Masseter
Orbicularis oris
Buccinator
Risorius
Platysma
Depressor anguli oris
Depressor labii inferioris
Mentalis (cut)
Sternal head of
sternocleidomastoid
Thyroid cartilage
of the larynx
Clavicular head of
sternocleidomastoid
Trapezius
Clavicle
Platysma
(cut and reflected)
Anterior view
Muscles of facial expression
–  Lie in the face and scalp
–  Thin and variable in shape
–  Often insert on the skin—not on bones
–  Innervated by cranial nerve VII—the facial
nerve
Figure 10.4a Muscles of the Head and Neck, Part II
Epicranial
aponeurosis
Temporoparietalis
(cut and reflected)
Frontal belly of
occipitofrontalis
Temporalis
Procerus
Orbicularis
oculi
Nasalis
Occipital belly of
occipitofrontalis
Levator labii
superioris
Zygomaticus
minor
Masseter
Levator anguli
oris
Buccinator
Zygomaticus
major
Sternocleidomastoid
Orbicularis
oris
Mentalis (cut)
Depressor
labii inferioris
Omohyoid
Depressor
anguli oris
Platysma (cut
and reflected)
A diagrammatic lateral view
Muscles of Mastication
•  Four main pairs of muscles involved in mastication
–  Innervated by mandibular division of the trigeminal
nerve (cranial nerve V)
–  Prime movers of jaw closure
•  Masseter and temporalis
–  Side-to-side movement
•  Pterygoid muscles
–  Compression of cheeks
•  Buccinator muscles
Superior
temporal line
Temporalis
Zygomatic
arch
Capsule of
temporomandibular
joint
Masseter
The temporalis and masseter are prominent muscles on the lateral surface
of the skull. The temporalis passes medial to the zygomatic arch to
insert on the coronoid process of the mandible.The masseter inserts on the
angle and lateral surface of the mandible.