9 - Perineum Flashcards
1
Q
Pelvic Girdle
A
- R and L coxal bones
- coxal bones articulate with each other at the ant midline (pubic symphysis) and posteriorly with the sacrum at the sacro-iliac joints
- encloses the lower part of the abdominal cavity, entire pelvic cavity, and superior perineum
2
Q
coxal bones
A
-fusion of ilium, ischium, and pubis
3
Q
pubic symphysis
A
- where the two os coxae articulate with each other anteriorly
- secondary cartilaginous joint
- contains the fibrocartilaginous articular disc (interpubic disc)
4
Q
interpubic disc
A
fibrocartilaginous disc in the pubic symphysis (secondary cartilaginous joint)
5
Q
sacro-iliac joint
A
- where the coxal bones articulate with the sacrum anteriorly
- where the pelvic girdle connect the ‘free portion’ of the lower limbs to the axial skeleton
6
Q
sacrospinous and sacrotuberous ligaments
A
- convert the greater and lesser sciatic notches into the greater and lesser sciatic foramina which act as passageways between the gluteal region and the pelvis or perineum (respectively)
- When exceptional force is applied at the lumbosacral joint, these ligaments serve to prevent the anterior rotation of the proximal sacrum at the sacroiliac joint (i.e., they anchor the inferior end of the sacrum to the ischium)
7
Q
greater/false pelvis
A
- superior to pelvic inlet (from iliac crest to pelvic inlet)
- contributes to the wall of the abdominal cavity and offers protection to lower abdominal viscera (superior portions of pelvic viscera may project into it)
8
Q
lesser/true pelvis
A
- inferior to the pelvic brim (from pelvic inlet to pelvic outlet)
- offers protection to pelvic viscera in the superior portion of the perineum (structures in the deep perineal pouch)
9
Q
pelvic cavity
A
- inferoposterior portion of the abdominopelvic cavity
- bounded superiorly by the pelvic inlet (brim) and inferiorly by the pelvic diaphragm
- contains pelvic viscera and inferiorly projecting portions of abdominal viscera, it is completely protected by the bones of the lesser pelvis
10
Q
perineum
A
- region between the thighs inferior to the pelvic diaphragm (between the pelvic diaphragm and the skin)
- partially protected by the bones of the lesser pelvis (the pelvic outlet forms part of its outer boundary)
- includes all of the structures in the anal and urogenital triangles including external genitalia and anus
11
Q
piriformis m.
A
- forms posterior wall/roof of pelvis.
- Passes through greater sciatic foramen.
- Acts on the hip joint
12
Q
obturator internus m.
A
- Forms lateral wall of pelvis & perineum
- Passes through lesser sciatic foramen
- Acts on the hip joint
13
Q
pelvic diaphragm
A
- funnel-shaped muscle that forms the floor of the pelvic cavity.
- separates the pelvic cavity from the perineum
- functions to support the pelvic viscera, maintain intra-abdominal pressure and facilitates childbirth
- Composed of two muscles on each side:
1. Coccygeus m.
2. Levator Ani m.
14
Q
levator ani m.
A
- Surrounds the urogenital hiatus (for urethra and, in females, also vagina)
- Puborectal sling: specialised fibres of the levator ani that surround the anorectal junction. It is important for fecal continence
15
Q
blood supply to the pelvis
A
-comes primarily from branches of the internal iliac artery
16
Q
somatic innervation of pelvic and perineal structures
A
-comes primarily from branches off the lumbosacral plexus (ventral rami of L1-S4)
17
Q
perineum
A
- diamond shaped region inferior to the pelvic diaphragm -Divided into two subregions by a line connecting the ischial tuberosities
- –Posteriorly:Anal triangle
- –Anteriorly: Urogenital triangle
18
Q
anal canal
A
- inferior continuation of the rectum
- begins at the superior edge of the levator ani (and superior limit of anal columns)
19
Q
ischioanal fossae
A
- surround the wall of the anal canal
- wedge-shaped, fat-filled regions that lie between the skin of the anal region and the pelvic diaphragm
- allow for expansion of the anal canal
20
Q
superior 2/3 of anal canal
A
- derived from hindgut (endodermal lining creating mucosa)
- viscerally innervated (GVA, GVE)
- has anal columns
21
Q
anal columns
A
- vertical folds created by tributaries to the superior rectal v.
- These columns are joined together by semilunar folds called anal valves
22
Q
pectinate line
A
- approximately at the junction between the superior 2/3’s and inferior 1/3 of the anal canal (demarcated anatomically by the anal valves and the inferior limit of the anal columns)
- represents the termination of the gut-derived viscera
23
Q
inferior 1/3 of the anal canal
A
- Ectodermal lining (creating skin)
- somatically innervated (GSA, GSE)
24
Q
internal anal sphincter
A
-Involuntary
-Formed by a thickening of the inner circular layer
of smooth muscle
25
external anal sphincter
-Voluntary
-Skeletal muscle that encloses the distal anal
canal
-Some of it’s deeper fibers merge with those of the puborectalis portion of the levator ani.
26
perineal membrane
- thin sheet of deep fascia, stretching between the ischiopubic rami forming the ‘skeleton’ of the urogenital triangle.
- --It contains passageways for the urethra and, in females, the vagina.
- --It divides the UG triangle into superficial and deep perineal pouches
- --It’s posterior edge is thickened centrally to form the perineal body.
27
Perineal body
-serves as an attachment site for many of the muscles of both the superficial and deep perineal pouches, the anal triangle and also the levator ani
28
superficial perineal pouch
- Between the membranous layer of the subcutaneous tissue and the perineal membrane (i.e.,superficial to perineal membrane)
- Lateral boundaries are formed by the ischiopubic rami
29
contents of the superficial perineal pouch in men
- Bulb of the penis and bulbospongiosus m.
- Crura of the penis and ischiocavernosus m.
- Proximal part of the spongy urethra
- perineal branches of the internal pudendal vessels and pudendal nerves
30
contents of the superficial perineal pouch in women
- Bulbs of the vestibule and bulbospongiosus m.
- Crura of the clitoris and ischiocavernosus m.
- Greater vestibular glands
- perineal branches of the internal pudendal vessels and pudendal nerves
31
deep perineal pouch
-Between inferior fascia of pelvic diaphragm (levator ani + coccygeus) and the perineal membrane (i.e., deep to perineal membrane)
-Lateral boundaries are formed by the lower portion of the obturator internus mm. (and the obturator fascia).
- Contains part of the urethra (in males the intermediate urethra) and several skeletal muscles including the external
urethral sphincter.
32
tissues of the superficial perineal pouch in females
- 2 Corpora cavernosa (form the crura, body & glans of the clitoris). The crura are covered by ischiocavernosus mm.
- 2 bulbs of the vestibule (composed of corpus spongiosum) are located on either side of the vaginal orifice along with the greater vestibular glands. The bulbs and glands are covered by bulbospongiosus m.
33
tissues of the superficial perineal pouch in males
Spongy tissues:
- Corpus spongiosum: forms bulb of penis and continues through the shaft/body of the penis taking the urethra to the end. Distally it forms the glans penis, where the urethra terminates (external urethral orifice). The bulb is covered with bulbospongiosus muscle.
- Paired Corpora Cavernosa form the crura of the penis and continue into the shaft/body. The crura are covered with ischiocavernosus muscle.
34
3 parts of the penis
- The root of the penis is fixed to the inferior surface of the perineal membrane. It is composed of the crura and bulb and their overlying striated muscles
- The body of the penis is suspended from the pubic symphysis by the suspensory ligament of the penis
- The glans of the penis is the distal expansion of the corpus spongiosum
35
neurovasculature of the perineum
- PUDENDAL NERVE (s2-s4)
- give off inferior rectal nerves
- motor (GSE) to all skeletal muscles of the perineum,
- sensory (GSA) from the skin of the perineum, the distal vagina and the inferior one-third of the anal canal.
36
inferior rectal nerve and vessels
-travel across the ischioanal fossa (in the anal triangle) toward the anal canal and external anal sphincter
37
Superior rectal a./v. - from/to IMA/IMV (portal)
-terminate inside the anal columns, supplies region above pectinate line
38
Middle rectal a./v. - from/to Internal iliac a./v. (caval)
-anastomose with both superior and inferior rectal vessels
39
Inferior rectal a./v. - from/to Internal pudendal a./v. (caval)
-supplies region below pectinate line
40
blood supply of anal canal
- superior rectal a/v
- middle rectal a/v
- inferior rectal a/v
41
Internal hemorrhoids
- Prolapsed rectal mucosa containing tributaries of the superior rectal vein .
- Occur above the pectinate line, so are painless.
42
external hemorrhoids
- Varicosities of the inferior rectal veins.
- Often blood will clot under the skin in the external rectal venous plexus (branches of inferior rectal).
- occur below the pectinate line, receive somatic innervation, so are painful.
43
extravasation of urine
- The most proximal portion of the spongy urethra is the most commonly ruptured portion of the male urethra.
- The extravasated urine will lie in the space between the fascial layers that are continuous with the superficial (scarpa’s) and deep fasciae of the anterior abdominal wall.
