Occiput (Quiz 2/ Test 2) Flashcards
Is the occiput a vertebra?
No
The occiput is an attachment for…
Spinal muscles and ligaments
The occiput is an articulation point between ________ and ________
Skull, spine
When does the occiput form?
In embryo
Where is the ring around the foreman magnum derived from?
Top of cranial primary sclerotome
What is the occiput homologous to?
C1 embedded into the base of the skull
What forms the posterior base of the skull?
Occiput
What bone is large, cupped, externally convex, internally concave, and is a trapezoidal bone?
Occiput
What hole is in the occiput?
Foreman magnum
What are the 4 descriptive regions of the occiput?
1) basi-occiput
2) L lateral portion
3) R lateral portion
4) squamous portion
The basilar portion of the occiput, also known as the basi-occiput is everything anterior to the…
Foreman magnum
What does the basi occiput articulate with?
Sphenoid bones and L/R temporal bones
What is the X-ray landmark on the basi occiput?
Distinct trapezoid outline
What tubercle is found on the basi occiput? Where is it located?
-pharyngeal tubercle (small bump)
-located in mid-external basion
Where on the basi occiput is there an attachment for the longus capitus muscle?
Test q
Pharyngeal tubercle
What part of the basi occiput is smooth, featureless, and deeply concave?
Internal surface
What part of the basi occiput supports the anterior medulla oblongata?
Internal surface
What part of the basi occiput is penetrated by several small foramina that transmit cranial nerves?
Internal surface
The lateral/condylar portions of the occiput is everything lateral to the….
Foramen magnum
What does the lateral/condylar portion of the occiput articulate with?
L/R temporal bones and C1 below
What part of the occiput are the occipital condyles (knuckles)? Where are they found?
Lateral/condylar portions L/R (2 oval bony projections found on the lateral to anterior 1/2 of foramen magnum, long axes converge to the anterior)
What part of the lateral/ condylar portions of the occiput forms L/R angles of condylar convergence with the midline?
Occipital condyles
Are the occipital condyles symmetrical?
Sometimes, can be asymmetrical
What part of lateral/condylar portions of the occiput has a point of articulation with C1?
Condylar articulate surfaces
What part of the lateral/condylar portions of the occiput is smooth, clearly marginated surface, and covers the entire bottom of the condyle?
Condylar articular surfaces
What part of the lateral/condylar portions of the occiput is kidney shaped and convex along both long and short axes?
Condylar articular surfaces
What direction do the condylar articular surfaces face?
Test q
Inferolaterally
Are the condylar articular surfaces symmetrical?
Sometimes (both slope and convexity are highly variable)
What tubercles are found on the lateral/condylar portions of the occiput? Where are they located?
-Condylar tubercles (very indistinct)
-located on medial condylar surface
-projects into foramen magnum
What part of the lateral/condylar portions of the occiput has an attachment for the alar ligaments?
Test q
Condylar tubercles
What fossae is found in the lateral/condylar portions of the occiput?
Condyloid fossae
What are the condyloid fossae of the lateral/condylar portions of the occiput?
-shallow depressions posterior to the condyles
-receives posterior lips of the lateral masses
-prevents bony “kissing” in hyperextension
What processes are found on the lateral/ condylar portions of the occiput?
Jugular processes
What are the jugular processes of the lateral/condylar portions of the occiput?
-tabs of bone lateral to the condyles
-named for jugular notch/foramen/vein
What is homologous/equivalent to the jugular processes of the lateral/condylar portions of the occiput?
Test q
C1 TPs
What part of the lateral/condylar portions of the occiput is penetrated by several small foramina that transmits cranial nerves?
Jugular processes
What shape is the squamous portion of the occiput?
Scale shaped
The squamous portion of the occiput is everything posterior to the…
Foramen magnum
What does the squamous portion of the occiput articulate with?
L/R parietal bones
What protuberance is found on the external surface of the squamous portion of the occiput?
EOP (also known as external occipital protuberance, point inion, or knowledge bump)
Its a large tubercle in the middle of the external squamous occiput, easily palpated on the posterior skull
What part of the squamous portion of the occiput is an attachment for the nuchal ligament?
EOP and median nuchal line/occipital crest
Which nuchal lines are faint/indistinct bony ridges?
highest nuchal lines
Where do the highest nuchal lines project?
superolaterally from EOP
What part of the squamous portion of the occiput is the attachment for the occipitalis muscles?
test q
highest nuchal lines
Where do the superior nuchal lines project?
laterally from the EOP
What part of the squamous portion of the occiput is the attachment site for the trapezius and splenius capitis muscles?
test q
superior nuchal lines
Which nuchal lines are hard to palpate?
highest nuchal lines are very faint
inferior nuchal lines are under the “occipital shelf”
Where do the inferior nuchal lines project?
laterally from the median nuchal line (cross median nuchal line halfway between EOP and foramen magnum)
What part of the squamous portion of the occiput is the attachment site for the rectus capitis posterior major and superior oblique muscles?
test q
inferior nuchal lines
What are the 3 occipital plana?
1) planum occipital
2) L/R superior nuchal plana
3) L/R inferior nuchal plana
Where is the planum occipital found?
-on squamous portion of occiput
-above the highest nuchal lines
-smooth and featureless
-underlies scalp
Where is the L/R superior nuchal plana found?
-on squamous portion of occiput
-between the superior and inferior nuchal lines
Which plana is an attachment for the semispinalis capitis muscle?
L/R superior nuchal plana
Where is the L/R inferior nuchal plana found?
-on squamous portion of occiput
-between the inferior nuchal lines and the foramen magnum
Which plana is an attachment for the rectus capitis posterior minor muscle?
L/R inferior nuchal plana
The internal surface of the occiput is deeply concave. What is its function?
cradles posterior lobes of brain
What eminence is found in the internal surface of the occiput?
cruciate eminence
What is the cruciate eminence of the internal surface of the occiput?
-2 prominent perpendicular ridges
-divides internal surface into 4 fossae
»L/R superior fossae cradles the occipital lobes of the cerebrum (quiz 2 q)
»L/R inferior fossae cradles the L/R lobes of the cerebellum
also note, the cruciate eminence has attachments for internal membranes
Where is the IOP found?
-internal surface of occiput
-at the intersection of the cruciate eminence
-directly internal to the EOP
-smooth, featureless (cradles and supports brain tissue)
What is the largest bony foramen in the skull?
foramen magnum
What is the 3rd largest foramen in the skeleton?
foramen magnum (obturators L/R are larger)
What is the foramen magnum? What are its 2 divisions?
-passes the spinal cord from the skull to the spine
-shaped like a “pinched oval”
-divided into 2 regions (posterior and anterior portion)
What is the posterior portion of the foramen magnum? What does it accommodate?
-larger, round portion
-accommodates the spinal cord
What is the anterior portion of the foramen magnum? What does it accommodate?
-smaller, square portion
-accommodates the odontoid ligaments
What is the boundary between the anterior and posterior portions of the foramen magnum?
condylar tubercle
