Download The Skeletal System

The Skeletal System
Skull Anatomy
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Overview
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Braincase: 8 bones
Face: 14 bones
Auditory ossicles: 6 bones
1 hyoid bone
Braincase: frontal bone, occipital bone, sphenoid bone, ethmoid bone, left and
right parietal bones and left and right temporal bones.
Facial bones: mandible, vomer, left and right maxilla, left and right zygomatic
bones, left and right palatine bones, left and right nasal bones, left and right
lacrimal bones, left and right nasal conchae.
Auditory ossicles: three bones in each middle ear (left and right) that amplify sound.
The malleus, the incus and the stapes. We’ll study these when we look at sensory
systems.
The hyoid bone: The one bone in the body that is “floating” – that does not articulate
with any other bones. The base of the tongue is attached to the hyoid. The hyoid
bone is useful in forensic science because it shows sexual dimorphism (it is shaped
differently in males and females) and because a hyoid fracture is often evidence of
strangulation.
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The Braincase
Parietal bone (L&R)
Frontal bone
Occipital bone
Sphenoid bone
Temporal bone (L&R)
(Ethmoid bone not visible in lateral view)
The frontal bone covers the frontal (forehead) region and is attached to two
parietal bones (left and right). The occipital bone makes up the posterior part of
the skull. The left and right temporal bones are found around the region of the
ears. The sphenoid bone is a single bone that extends all the way across the skull
from left to right and protects the lower anterior portion of the brain. The ethmoid
bone is not visible in the lateral view, but it is just inferior to the sphenoid bone.
(Most of this lecture is visual in nature and involves labelling)
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The Braincase
Ethmoid bone
The ethmoid bone is inside the skull and not easily seen from the outside, but
parts of it can be seen within the nasal cavity and the orbits. Most notable, it makes
up the top part of the nasal septum.
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The Braincase
Squamous suture
Sagittal suture
Coronal suture
Lamboid suture
Sutures are immovable joints where the bones of the skull have fused permanently
together during development. They are easily visible in the adult skull. The coronal
suture separates the frontal bone and the parietal bones. The lamboid suture joins
the parietal bones to the occipital bone. The squamous suture joins the parietal
bones to the temporal bones on each side of the skull. The sagittal suture runs
along the top of the skull and separates the left and right parietal bones.
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The Braincase
Zygomatic arch
Mastoid process
External auditory meatus
The external auditory meatus is a tunnel through each temporal bone that
channels sound towards the eardrum, which is located deep within the skull. The
mastoid process is an attachment point for muscles that rotate the head. The
zygomatic arch is an attachment point for muscles that move the jaw.
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The Braincase
In this picture, try to identify the frontal bone, left parietal bone, occiptal bone, left
temporal bone, sphenoid bone, lamboid suture, squamous suture, coronal suture,
zygomatic process, mastoid process and external auditory meatus.
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The Braincase
In this picture, try to identify the frontal bone, left parietal bone, occiptal bone, left
temporal bone, sphenoid bone, lamboid suture, squamous suture, coronal suture,
zygomatic process, mastoid process and external auditory meatus.
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The Braincase
In this picture, try to identify the frontal bone, parietal bones, sphenoid bone
(including inside the orbit), ethmoid bone, and zygomatic process.
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The Face
Orbit
Nasal cavity
The facial bones do not directly contact the brain. They surround the major cavities
of the skull: the nasal cavity and the orbit. The nasal cavity is divided into right and
left sides by the nasal septum, which is made up of the ethmoid bone and the
vomer. The orbit is a cone-shaped fossa that holds the eyeball.
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The Face
Lacrimal bone (L&R)
Nasal bone (L&R)
Nasal Concha (L&R)
Zygomatic bone (L&R)
Vomer
Maxilla (L&R)
Mandible
The maxilla and mandible make up the upper and lower jaw and hold the teeth.
The zygomatic bones are the cheekbones. The nasal bones make up the bony
upper part of the nasal cavity. The vomer is the lower part of the nasal septum. The
nasal conchae are conch shell-shaped bones that increase surface area inside the
nasal cavity. The lacrimal bones are small bones on the medial wall of the orbits.
They have openings for the nasolacrimal ducts, which drain tears from the orbit to
the nasal cavity.
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The Face
Optic foramen
Intraorbital foramen
Mental foramen
The optic foramen is a circular opening in the back of the orbit. The optic nerve
carries visual information from the retina of the eyeball to the brain through this
hole. The intraorbital foramina and mental foramina are openings that nerves
pass through between the skin of the face and the brain.
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The Face
Identify each facial bone and foramen in this picture.
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Other Skull Features
Mandibular fossa
Styloid process
The mandibular fossae are indentations in the temporal bone where the
mandibular condyle (on the condolyoid process of the mandible itself) articulates.
The joint itself is called the temporomandibular joint (TMJ). At the base of the skull
on each side, a styloid process sticks out. Muscles that control the tongue and
larynx attach to the styloid processes.
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Other Skull Features
Foramen magnum
Occipital condyles
Palatine bone (L&R)
The foramen magnum is a large opening at the base of the skull where the
brainstem and spinal cord exit the skull. The occipital condyles are smooth areas
that articulate with the vertebral column. The palatine bones make up the roof of
the mouth and separate the oral cavity from the nasal cavity.
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Other Skull Features
Identify the skull features visible from the base of the skull.
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The Skull
Review: Try to identify all visible braincase bones, facial bones and bone features.
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The Skull
Review: Try to identify all visible braincase bones, facial bones and bone features.
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The Skull
Review: Try to identify all visible braincase bones, facial bones and bone features.
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