Introduction to Sacrum

Question 1

lumbarization of the sacrum

Answer 1

when S1 and S2 do NOT fuse

Question 2

sacralization of the lumbar spine

Answer 2

when L5 fuses to S1

Question 3

superior aspect

Answer 3

base

Question 4

inferior aspect

Answer 4

apex

Question 5

anterior surface

Answer 5

concave

Question 6

posterior surface

Answer 6

convex

Question 7

medial row/crest

Answer 7

fusion of sacral articular processes

Question 8

lateral rows/crests

Answer 8

fusion of sacral transverse processes

Question 9

inferolateral angle (ILA)

Answer 9

curve at the end of the lateral rows

Question 10

sacral canal

Answer 10

contains the cauda equina and for bilateral sacral foramina for the ventral and dorsal rami of the sacral spinal nerves S1-S4

Question 11

sacral hiatus

Answer 11

defect near the apex, where the lamina failed to close

Question 12

coccyx

Answer 12

made up of 4 vertebrae
lowest part of the spinal column
coccyx attaches to the sacral apex via the sacrococcygeal joint
ganglion impair = where right and left sympathetic chains join rests on anterior aspect of the coccyx

Question 13

palpatory bony landmarks

Answer 13

sacral base
sacral sulci
ILA

Question 14

sacral sulci

Answer 14

to bilateral palpable grooves medial and slightly superior to the PSIS

Question 15

sacrotuberous ligament

Answer 15

attaches sacrum to ischial tuberosity

works w/ sacrospinous ligament stabilize anterior motion, preventing posterior superior rotation

Question 16

sacrospinous ligament

Answer 16

attaches sacrum to ischial spine

works w/ sacrotuberous ligament stabilize anterior motion, preventing posterior superior rotation

Question 17

iliolumbar ligament

Answer 17

attaches 4th and 5th lumbar vertebra to iliac crests
stabilizes posterior motion restricting anterior motion of of L4/L5
upper part blends in with the sacroiliac ligament

Question 18

primary - intrinsic m of the pelvic diaphragm

Answer 18

levator ani group 
pubococcygeus m 
puborectalis m
iliococcygeus m
cocygeus mm

Question 19

secondary - mm considered to have partial attachment to the true pelvis

Answer 19

rectus abdominis 
transverse abdominis 
internal and external oblique 
quadratus lumborum 
also m of the posterior anterior and medial compartments of the lower extremity

Question 20

dura mater

Answer 20

layers of fibrous CT
tension in this CT has a direct effect on the cranial and sacral bone motion which it attaches to
dural connections b/w cranium and sacrum (C1 and C2 to S2)

Question 21

force closure

Answer 21

holding an object by pressure on the sides

created by mm, lig, and fascia surrounding the SI joint

Question 22

form closure

Answer 22

stacking or the use of a roman arch as a self supporting structure
the sacrum acts as the keystone of the arch being wedged b/w iliums

Question 23

superior

Answer 23

respiratory - axis for respiratory motions as well as nutation and counternutation from SBS flexion/extension

Question 24

middle

Answer 24

postural or sacroiliac axis for flexion/extension in sitting and standing

Question 25

inferior

Answer 25

iliosacral axis for rotation of the iliums on the sacrum

at the level of the inferior pole of the lower sacral articulation

Question 26

oblique axes of motion

Answer 26

where dynamic/torsional motion occur

named for the cephalad side

Question 27

respiratory motion

Answer 27

around superior transverse axis
with inhalation sacral base moves posteriorly while sacral apex moves anteriorly
decreased lumbar lordosis
w/ exhalation sacral base moves anteriorly while sacral apex moves posteriorly (increased lumbar lordosis)

Question 28

postural motion

Answer 28

in standing and seated positions
around middle transverse axis
flexion and extension corresponding to anatomical nomenclature same terminology as used with the spine

Question 29

postural motion - flexion

Answer 29

forward bending

sacral base moves anterior sacral apex moves posterior

Question 30

postural motion - extension

Answer 30

backward bending

sacral base moves posterior, apex moves anterior

Question 31

craniosacral flexion (couternutation)

Answer 31

influenced by the dura the sacral base moves posteriorly and the apex moves anteriorly

Question 32

craniosacral extension (nutation)

Answer 32

sacral base moves anteriorly and the apex moves posteriorly

Question 33

dynamic motion

Answer 33

occurs when walking
occurs around oblique axes
sacral base moves forward on one side then the other side around the oblique axes
as this occurs the innominates are constantly rotation in opposite directions to one another (one rotates anteriorly, the other posteriorly)