Week 9 The pelvis and perineum Flashcards
What is the perinium?
Refers to an external surface area as well as a compartment of the body
The region is that which overlies the inferior pelvic outlet
How is the perineum separated from the pelvic cavity?
By the pelvic diaphragm
What is the perineal region?
The narrow area between the thighs when standing in the anatomical position
Is diamond shaped when the leg are abducted
What sits in the perineal region?
Mons pubis anteriorly
Medial aspect of the thighs laterally
Gluteal folds and upper end of intergluteal cleft posteriorly
What is the mons pubis?
A mound of fatty tissue overlying the pubic symphysis
What is the:
Perineum
Peritoneum
Peroneal
Perenium:
Area between the thighs
Peritoneum:
serous membrane lining the abdominal cavity
Peroneal:
Relating to the fibula or surrounding area
What are the Ossifiborous structures surrounding the perineum?
Pubic Symphysis anteriorly
Inferior Pubic Rami, Ischial Rami anteriolaterally
Ischial Tuberosities laterally
Sacrotuberous Ligaments posteriolaterally
Inferior aspect of the Sacrum and Coccyx posteriorly
What are the names of the two triangular regions of the perineum?
Posteriorly is the Anal triangle
Anteriorly is the urogenital region or urogenital triangle
What is the Perineal Body?
The midpoint of the line joining the ishial tuberosities (muscle)
It is an irregular fibromuscular mass
contains collagenous and elastic fibres
Where is the Perineal body located?
Posterior to the bulb of the penis or vestibule of the vagina
Anterior to the anus and anal canal
It is attached to the posterior border of the perineal membrane, which is the attachment for the perineal muscles
What muscles attach to the perineal body?
Bulbospongiosus
External Anal Sphincter
Superficial and Deep transverse perineal muscles
What is the perineal membrane?
A sheet of deep fascia which stretched from the pubic arch and covers the anterior aspect of the pelvic outlet
What is the anal canal?
The terminal part of the bowel, begins where the pubo rectalis muscle forms sling around the anorectal junction.
Where does the anococcygeal ligament run?
Between the anococcygeal ligament and the perineal body
What is the External anal sphincter?
Large voluntray band of muscle
Large voluntary band of muscle
Found either side of the inferior 2/3rds of the anal canal. Blends superiorly with the puborectalis muscle
What supplies the external anal sphincter
S4 inferior rectal nerve
What is the internal anal sphincter?
Involuntary muscle band
Surrounds the superior 2/3 rds of the anal canal
It is a thickening of the muscle (circular layer) within the bowel
What is the internal anal sphincter supplied by?
Parasympathetic fibres from the pelvic splanchnic nerves
Why is the internal anal sphincter always contracted? When does it relax?
To prevent leakage
To release pressure from faeces and gas
what does the superior part of the mucous membrane of the internal anal sphincter contain? What are these?
Ridges called anal colums
These are layers of mucous membrane which contain the terminal branches of the superior rectal artery and vein
At the inferior end the columns are joined by anal valves
What are superior to the anal valves?
Sinuses which when compressed release mucous to aid in defication
What is the line produced by the anal valves called?
The pectinate line
What does the pectinate line do?
Divides the anus into superior and inferior regions
What is the arterial supply to the rectum?
Inferior rectal arteries
Internal pudendal arteries
What is the venous drainage of the anus?
The internal venous plexus
Superior rectal vein
Inferior rectal vein
Middle rectal vein
What innervates the rectum?
Sympathetic and parasympathetic fibres from the inferior hypogastric plexus (superior to the pectinate line)
Branches from the pudendal nerve (inferior to the pectinate line)
What are the muscles of the perineum?
Levator ani
Coccygeus
These make the pelvic diaphragm
What is the origin Insertion and nerve supply of levator ani? What muscles make up this muscle?
Origin- body of the pubis, obturator fascia, ischial spine
Insertion - perineal body, coccyx, anococcygeal ligament, walls of the prostate / vagina, rectum and anal canal
Nerve supply - S4 nerve to Lev Ani
Made up of:
Puborectalis
Pubococcygeus
Iliococcygeus
What is the origin, insertion and nerve supply of coccygeus?
Origin - ischial spine
Insertion - inferior end of the sacrum, coccyx
Nerve supply S4,5
What are the sex differences in the pelvis?
Male pelvis
generally heavy and thick
has more prominent bone markings
Female pelvis:
wider, shallower
larger superior and inferior pelvic apertures
broader sacrum, thus hips bones are wider apart
the ischial tuberosities are farther apart
sacrum less curved
