<< Chapter < Page Chapter >> Page >

External and internal views of base of skull

This image shows the superior and inferior view of the skull base. In the top panel, the inferior view is shown. A small image of the skull shows the viewing direction on the left. In the inferior view, the maxilla and the associated bones are shown. In the bottom panel, the superior view shows the ethmoid and sphenoid bones and their subparts.
(a) The hard palate is formed anteriorly by the palatine processes of the maxilla bones and posteriorly by the horizontal plate of the palatine bones. (b) The complex floor of the cranial cavity is formed by the frontal, ethmoid, sphenoid, temporal, and occipital bones. The lesser wing of the sphenoid bone separates the anterior and middle cranial fossae. The petrous ridge (petrous portion of temporal bone) separates the middle and posterior cranial fossae.

Frontal bone

The frontal bone    is the single bone that forms the forehead. At its anterior midline, between the eyebrows, there is a slight depression called the glabella    (see [link] ). The frontal bone also forms the supraorbital margin of the orbit. Near the middle of this margin, is the supraorbital foramen, the opening that provides passage for a sensory nerve to the forehead. The frontal bone is thickened just above each supraorbital margin, forming rounded brow ridges. These are located just behind your eyebrows and vary in size among individuals, although they are generally larger in males. Inside the cranial cavity, the frontal bone extends posteriorly. This flattened region forms both the roof of the orbit below and the floor of the anterior cranial cavity above (see [link] b ).

Occipital bone

The occipital bone    is the single bone that forms the posterior skull and posterior base of the cranial cavity ( [link] ; see also [link] ). On its outside surface, at the posterior midline, is a small protrusion called the external occipital protuberance    , which serves as an attachment site for a ligament of the posterior neck. Lateral to either side of this bump is a superior nuchal line    (nuchal = “nape” or “posterior neck”). The nuchal lines represent the most superior point at which muscles of the neck attach to the skull, with only the scalp covering the skull above these lines. On the base of the skull, the occipital bone contains the large opening of the foramen magnum    , which allows for passage of the spinal cord as it exits the skull. On either side of the foramen magnum is an oval-shaped occipital condyle    . These condyles form joints with the first cervical vertebra and thus support the skull on top of the vertebral column.

Posterior view of skull

This figure shows the posterior view of the skull and the major parts are labeled.
This view of the posterior skull shows attachment sites for muscles and joints that support the skull.

Sphenoid bone

The sphenoid bone    is a single, complex bone of the central skull ( [link] ). It serves as a “keystone” bone, because it joins with almost every other bone of the skull. The sphenoid forms much of the base of the central skull (see [link] ) and also extends laterally to contribute to the sides of the skull (see [link] ). Inside the cranial cavity, the right and left lesser wings of the sphenoid bone    , which resemble the wings of a flying bird, form the lip of a prominent ridge that marks the boundary between the anterior and middle cranial fossae. The sella turcica    (“Turkish saddle”) is located at the midline of the middle cranial fossa. This bony region of the sphenoid bone is named for its resemblance to the horse saddles used by the Ottoman Turks, with a high back and a tall front. The rounded depression in the floor of the sella turcica is the hypophyseal (pituitary) fossa    , which houses the pea-sized pituitary (hypophyseal) gland. The greater wings of the sphenoid bone extend laterally to either side away from the sella turcica, where they form the anterior floor of the middle cranial fossa. The greater wing is best seen on the outside of the lateral skull, where it forms a rectangular area immediately anterior to the squamous portion of the temporal bone.

Questions & Answers

mention two processes of bone formation
Ngopiro Reply
what is the process for the bone formation
Ngopiro
what are the importance of studying anatomy and physiology?
Justine Reply
what are the importance of studying anatomy and physiology?
Justine Reply
bones and structures
Nkechi Reply
good morning
Cb
I wand anatomy notes 1st year
Cb
it's called going to class and taking notes
fyn sir
patrick
lmfao slay thank you for making my day lol
Bianca
heloo
King
I felt sleepy when I go for study immediately, how can I change
Abdi
what are the Hodgkin's disease
Mwasiti Reply
what are the components of cardiovascular system
Mwasiti Reply
Heart Blood Blood Vessel
Md
what are the components of the bone
Ngopiro
what is Hodgkin's disease
Mwasiti Reply
What is anatomy
Munira Reply
anatomy is a study of physical and structural functions of human body parts
Mohd
is the study of structure of the body and physical relationship involve between the body system
Mwasiti
is the study of structure of the body and physical relationship involve between the body system
Mwasiti
why simple columnar support peristalisis
Camilius Reply
why when sex of an individual is determined by y chromosome found in male therefore why there is many women than male
pamfili Reply
I'm not sure if I fully understand your question.
are you sure it is more
samir
i don't remember what I said.
I'm not sure if I fully understand your question.
roughly taking a lead.
samir
Muscle of mastication
JIMOH Reply
what is anatomy
Akanle
Sorry....it's the study of human body and it's functions.
Irene
Anatomy is the study of human organs
Kity
what is serum protein?
Salum
what is anatomy
Akanle
Anatomy is the study of human organs
Kity
Who is a bovin
Kity
Who is a bovin
Kity
Why do you ask tough questions I'm in JHS 3
Kity
pls does broken bones get healed
Desmond
yes
Belinda
how
Desmond
by surgery or medication
Desmond
Medication
Irene
why do a bovin not menstruate unlike women?
patrick
Why do you ask tough questions I'm in JHS 3
Kity
Anatomy is the study of structure of the human body
Belinda
yes
Belinda
medication
Belinda
yes
Belinda
animals within that group include cows as well as others.
ihope that was helpful
aaa,kity.bovin is a terminology used by veteranians to refer a cow.for dogs its carnine,cats it's ferline...etc
patrick
i believe if you look up the classification of Bovin , it tell clarify more for you.
ihope that was helpful
i don't think my first message about taxonomy sent
i don't think my first message about taxonomy sent
difference between seminiferous tubules and ejaculatory duct
Muhammad Reply
tell me the answer boss
Musibi
wats dis group
Kity
hhhhhhhxhxhmxkoshzhdvxznbxhhsklskhdhdh
Agemo Reply
what is azygous vein
Karan Reply
Sir muscle contraction ka topic kis part m milega
sonugora Reply

Get the best Anatomy & Physiology course in your pocket!





Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask