29. Bony Pelvis and Pelvic Wall Flashcards
The _____ and _____ lines delineate the pelvic brim
Pectineal; arcuate
Which ligaments of the pelvic girdle are strong and extensive, supporting the sacrum as it acts as a wedge separating the hip bones?
Sacroiliac ligaments
What 2 ligaments prevent rotation of the sacrum/coccyx and together with the hip bone create the greater and lesser sciatic foramen?
Sacrotuberous ligament
Sacrospinous ligament
AP compression produces fractures of what part of the hip bones?
Pubic rami
Lateral forces on the pelvis squeeze the ____ and ____ together, breaking both
Acetabulum; ilia
What are the weak areas of the pelvis subject to injury?
Pubic rami
Acetabulum
SI joints
Ala
What are the borders of the lesser or “true” pelvis?
Superior: pelvic brim (pelvic inlet)
Inferior: muscular pelvic diaphragm
Lateral and anterior: lower 1/2 of hip bones
Posterior: sacrum + coccyx
What region is considered the greater or “false” pelvis?
Superior to pelvic brim; occupied by abdominal viscera
What bone associated with the pelvis provides predominant support for abdominal weight?
Pubic bone
______ pelvis = normal male type
______ pelvis = normal female type
Android
Gynecoid
Compare the greater sciatic notch in males vs. females
Males: narrow (~70 degrees); inverted V
Females: almost 90 degrees
Compres the obturator foramen in males vs. females
Males: round
Females: oval
Compare the pubic arch and subpubic angle in males vs. females
Males: narrow (~70 degrees)
Females: wide (greater than 80 degrees)
Compare the pelvic outlet in males vs. females
Males: comparatively small
Females: comparatively large
Origin/insertion/innervation of obturator internus
Origin: ilium/ischium surface; obturator membrane
Insertion: greater trochanter
Innervation: obturator n.
Origin/insertion/innervation of piriformis m.
Origin: S2-4 surface, superior margin of greater sciatic notch; sacrotuberous ligament
Insertion: greater trochanter
Innervation: S1-S2
Origin/insertion/innervation of coccygeus m.
Origin: ischial spine
Insertion: inferior end of sacrum and coccyx
Innervation: S4-5
Actions of coccygeus m.
Support pelvic viscera; flex coccyx
In addition to being part of the pelvic wall, the ________ and ________ mm rotate the thigh laterally (both attach to the greater trochanter of femur)
Piriformis; obturator internus
The pelvic diaphragm is made up of 4 mm. named for their ____
Origin
What are the 4 muscles that make up the pelvic diaphragm (and their origins)?
(Ischio) coccygeus m. — ischial spine
Iliococcygeus m. — tendinous arch
Pubococcygeus m. — pubis
Puborectalis m. — pubis
Of the 4 muscles that make up the pelvic diaphragm, the iliococcygeus, pubococcygeus, and puborectalis mm. elevate the anal canal and together are called the ____ _____
Levator ani
The tendinous arch of the levator ani is a thickening of the ______ fascia between the ischial spine and body of pubis
Obturator
What muscle helps maintain fecal continence, relaxing during both urination and defecation, and is distinct from the external and internal anal sphincters?
Puborectalis m.
The ________ is the passageway for the rectum, urethra, and in females the vagina. it is formed by the anterior gap between the levator ani muscles
Urogenital (levator) hiatus
What muscles associated with the urogenital hiatus are the most susceptible to tearing during birth being most medial and large parts of the levator ani?
Pubococcygeus m.
Puborectalis m.
The _____ _____ sits inferior to the pelvic floor, is diamond-shaped, and is filled primarily with fat
Ischiorectal fossae
The ischiorectal fossae can be divided into 2 triangles: the _____ triangle and _____ triangle
Anal
Urogenital
The _____ membrane spans between rami in the ischiorectal fossae
Perineal
The ischiorectal fossae allows movement of the ____ _____ and expansion of the _____ canal. It contains ________ to the anal canal and some to the perineum
Pelvic diaphragm; anal; neurovasculature
The anal canal begins at the level when the rectum ‘perforates’ the ______ ____.
The ____ _____ are the associated longitudinal ridges
The ____ _____ are the associated folds at the base of the above structures
The ____ _____ are small recesses adjacent to the above structures, and function to exude mucus facilitating defecation
Levator ani
Anal columns
Anal valves
Anal sinuses
The internal anal sphincter is made up of inner circular _____ muscle, which is involuntary. It is kept in _____ contraction except when feces fill the rectum
It is responsible for ______% of resting anal tone
Smooth; tonic
55-85%
The external anal sphincter is made up of ______ muscle, which is voluntary. It is responsible for _____% of resting anal tone
Skeletal; 15-30
What are the 3 parts of the external anal sphincter?
Subcutaneous
Superficial
Deep (puborectalis)
______ are essentially enlarged and collapsed varicosities of normal venous anatomy that may be a major clinical consequence of portal hypertension
Hemorrhoids
_________ ________ = prolapse of rectal mucosa; due to weakened muscularis mucosa (bleeding often bright red due to abundant arteriovenous anastomoses within internal rectal venous plexus)
Internal hemorrhoids
Describe external hemorrhoids
External venous plexus covered with epidermis
What anatomical landmark is used to classify type of hemorrhoids as external vs. internal?
Pectinate line
How is the pectinate line used to classify whether hemorrhoid is external or internal? Which type is painful vs. not painful?
Internal hemorrhoids are above the pectinate line and are NOT painful
External hemorrhoids are below the pectinate line and are painful
How does rectal innervation differ above vs. below the pectinate line?
Above: inferior hypogastric plexus (visceral)
Below: inferior rectal nn (somatic)
How does venous drainage differ in the rectum above vs. below the pectinate line?
Above: primarily to superior rectal vein (portal)
Below: primarily to inferior rectal veins (systemic)
How does destination of lymph drainage differ above vs. below the pectinate line?
Above: internal iliac LNs, inferior mesenteric
Below: superficial inguinal LNs
How does embryological epithelial origin differ in the rectum above vs. below the pectinate line?
Above: endoderm
Below: ectoderm
