Sacrum/Coccyx Flashcards
Sacral promontory
A
Location: Anterior, superior margin of the first sacral vertebra (S1)
Function: Landmark in obstetrics; helps define the pelvic inlet
Articulations: Connects with the L5 vertebra at the lumbosacral joint
Pelvic sacral foramen
B
Location: Four pairs of openings on the anterior (pelvic) surface of the sacrum
Function: Transmit ventral rami of the sacral spinal nerves
Articulations: None directly, but linked to nerve exit pathways
Pedicle
C
Location: Short, thick part connecting the body of the sacrum to the sacral arch (S1 level)
Function: Forms part of the sacral vertebral arch, protecting the spinal cord
Articulations: Forms part of the posterior articulation with L5
Body of the fourth sacral segment
D
Location: Midline structure of the 4th sacral vertebra (anterior surface)
Function: Provides support and stability to the sacral structure
Articulations: Intervertebral articulation with S3 and S5 segments via intervertebral discs (although they are fused in adults)
Apex: facet for the coccyx
E
Location: Inferior tip of the sacrum
Function: Connects sacrum to coccyx
Articulations: Articulates with the base of the coccyx at the sacrococcygeal joint
Inferior lateral angle
F
Location: Lateral margins of the sacrum near its inferior end
Function: Provides attachment sites for ligaments; helps anchor the sacrum to the pelvis
Articulations: Joins with the coccyx and pelvic ligaments
Transverse ridge
G
Location: Horizontal ridges on the anterior surface of the sacrum between fused vertebral bodies
Function: Indicate the fusion lines between sacral vertebrae
Articulations: Not articulations themselves but represent former intervertebral joint sites
Ala
H
Location: Wing-like lateral projections from S1 on each side
Function: Serves as an attachment point for muscles and ligaments
Articulations: Articulates with the ilium of the hip bone at the sacroiliac (SI) joint
Superior articular facet
I
Location: Posterior, superior surface of S1
Function: Forms the zygapophyseal (facet) joint with the inferior articular process of L5
Articulations: Articulates with L5 vertebra above
Sacral promontory
1
Location: Anterior superior edge of the first sacral vertebra.
Function: Serves as a landmark in obstetrics for measuring pelvic inlet size.
Articulation: Joins the body of L5 vertebra at the lumbosacral joint.
Auricular facet
2
Location: Lateral aspects of the sacrum.
Function: Provides a large surface for weight transmission.
Articulation: Articulates with the iliac bones to form the sacroiliac joints.
Lateral border
3
Location: Side edges of the sacrum.
Function: Attachment site for ligaments and muscles; includes auricular surface and sacral tuberosity.
Articulation: Indirectly involved in the sacroiliac articulation via auricular surface.
Sacrococcygeal joint
4
Location: Between apex of sacrum and base of coccyx.
Function: Allows slight movement between sacrum and coccyx.
Articulation: Sacrum and coccyx.
Coccyx
5
Location: Inferior to sacrum; the tailbone.
Function: Provides attachment for pelvic floor muscles and ligaments.
Articulation: Articulates superiorly with sacrum at the sacrococcygeal joint.
Coccygeal cornu
6
Location: Posterior and superior aspect of the coccyx.
Function: Serves as a landmark and attachment point.
Articulation: Articulates with sacral cornu to help stabilize the sacrococcygeal joint.
Sacral hiatus
7
Location: Posterior inferior end of sacral canal.
Function: Exit point for the filum terminale and some sacral nerves.
Articulation: Not a direct articulation, but an opening in the vertebral arch.
Sacral cornu
8
Location: On each side of the sacral hiatus.
Function: Landmarks for locating sacral hiatus (useful in caudal anesthesia).
Articulation: Joins with coccygeal cornu.
Dorsal sacral foramen
9
Location: Posterior side of sacrum (4 pairs).
Function: Openings for the dorsal rami of sacral spinal nerves.
Articulation: No articulation; openings in bone.
Intermediate sacral crest
10
Location: Between dorsal and median sacral crests.
Function: Represents fused articular processes of sacral vertebrae.
Articulation: No articulation; remnant of vertebral joints.
Spinous tubercles
11
Location: Tips of the fused sacral spinous processes.
Function: Muscle and ligament attachment.
Articulation: No direct articulation; part of median sacral crest.
Median sacral crest
12
Location: Midline of the posterior sacrum.
Function: Represents the fused spinous processes.
Articulation: None; part of posterior sacral surface.
Superior articular process
13
Location: Posterior superior end of the sacrum.
Function: Connects sacrum to lumbar spine.
Articulation: Articulates with inferior articular processes of L5 to form a zygapophyseal joint.
Coccygeal cornu
A
Location: Posterior superior corners of the first coccygeal vertebra.
Function: Acts as a landmark; helps complete the sacral hiatus.
Articulation: Articulates with the sacral cornua to help form the sacrococcygeal joint.
Rudimentary transverse process
B
Location: Lateral projections on the coccygeal segments (especially the first coccygeal vertebra).
Function: Represents remnants of transverse processes; provides minor muscle attachment points.
Articulation: Does not articulate with other bones but may connect to ligaments and soft tissues (sometimes the first coccygeal transverse process fuses to the sacrum).
