Ischioanal Fossa and Pelvic Diaphragm Flashcards
What are the borders of the perineum?
Anteriorly- Pubic symphysis
Posteriorly- Coccyx
Laterally- Ischial tuberosity
The diamond shape of the perineum is best appreciated when the patient is in the _________ position.
Lithotomy
What two structures separate the pelvic cavity from the perineum?
-
Urogenital diaphragm
- Found in the urogenital triangle
-
Pelvic diaphragm
- Found in the anal triangle
NOTE: These two diaphragms are muscles and henceforth can be exercised and strengthened.
Between the 2 diaphragms is a fibrous block of tissue that serves as an attachment of the muscle found in the urogenital and pelvic diaphragm called the __________.
Perineal body
NOTE: In females it can be palpated between the vaginal orifice and the anus.
Function of the thoracoabdominal diaphragm
- Support pelvic organs
- Increase intra-abdominal/pelvic pressures upon contraction.
NOTE: The volume will decrease but the pressure will increase.
What are the two muscles of the pelvic diaphragm?
-
Levator ani
- Pubococcygeus
- Iliococcygeus
- Puborectalis.
- Coccygeus
What are the origins of the iliococcygeus muscle?
- Tendinous arch of the obturator internus muscle
- Inner part of the ischium
What two muscles originate from the tendinous arch?
Iliococcygeus
Ishiococcygeus
The anorectal junction is kinked 80 degrees by the ________.
Puborectal sling
NOTE: The puborectal ring has a certain muscle tone and pulls the rectal-anal junction anteriorly producing a kink which helps to control defecation
Which two muscles make up the puborectal ring?
Puborectalis
External anal sphincter
NOTE: Relaxation of the puborectal sling allows the rectum to straighten and the feces to drop down for defecation
Which muscle is most often town during childbirth?
Pubococcygeus
NOTE: Tearing of the pubococcygeus results in fecal incontinence
What are the two types of episiotomy?
-
Median episiotomy
- Take a scapel and run it from the vagina to about halfway to the anus.
-
Mediolateral episotomy
- Run the scapel posteriorly and then move laterally to avoid the perineal body
NOTE: The purpose of an episiotomy is to make the opening of the birth canal larger. If this procedure is performed it is important to avoid cutting the levator ani. Cutting the levator ani will weaken the pelvic floor and make the woman more prone to fecal incontinence.
What is the function of the broad ligament?
Serves as mesentery for the uterus, ovaries, and uterine tube
The ________ is subserous connective tissue that becomes thickened as the blood vessels come into the uterus and vagina. As it develops, it forms the cardinal ligament.
Endopelvic fascia
NOTE: The endopelvic fascia provides passive support but if this connective tissue becomes stretched becuase of childbith or lack of well developed pelvic muscles then you can’t restore it.
What is the most important ligament of the uterus?
Transverse cervical fascia (cardinal ligament)
NOTE: This ligament comes infrom laterally around the blood vessels going to the uterus and vagina and it provides passive support that can be surgically tightened to raise the contents of the pelvic cavity.
The sigmoid colon enters the pelvic cavity and terminates as the _________.
Rectum
NOTE: The rectum passes through the pelvic diaphragm and becomes the anal canal.
In a digital examination of the rectum of a male, doctor can palpate which three structures?
- Prostate
- Seminal vesicle
- Bladder
NOTE: The prostate is exam is to assess whether the prostate is hard or soft. It should be soft and smooth; if it is hard or lumpy that can be an indication of a tumor.
Only the (lower/upper) part of the rectum is covered by peritoneum.
Upper
NOTE: This part of the rectum is consider intraperitoneal. The terminal part of the rectum is extra-peritoneal and has no peritoneum and is beyond the serous membrane.
The ____________ is the lowest spot in the female’s body where seroud fluid may be drained.
The space between cervix and the posterior wall of the vagina is the _____________.
Posterior fornix
NOTE: The space betweeen the fornix and the pouch of Douglas is very thin. It is only peritoneum and the vaginal wall separating these two spaces so this a way a surgeon can gain access to the pelvic cavity either to drain fluid from ascites or infection or to inspect the ovaries.
What is one major physical differences between the sigmoid colon and rectum?
- Teniae coli terminate at the rectum
- The rectum has a complete outer coat of longitudinal muscle.
Culdoscope
Tool used to inspect the pelvic cavity. The vaginal opening has to be widened and the scope goes through the posterior fornix so that the clinician can examine the ovaries and oviduct.
Which structure is most at risk for divertuclosis?
Sigmoid colon
NOTE: Diverticula do not form in the rectum. this is because the outer layer of the rectum is completely smooth muscle.
Where is the most common place for diverticula in the sigmoid colon?
Near the tenae coli, at locations where blood vessels enter the wall of the gut.
NOTE: One of the main reasons for divrticula is because as food passes through the large bowel, water is extracted and the feces become progressively harder. There are ridges in the feces that can punch holes into the mucosa
Label
NOTE: The purpose of the semicircular folds is during the final stages of digestion the shelf-like folds help support the feces in the rectum and prevent them from falling out until the appropriate time.
The ______ is very sensitive to stretch, so when feces enters, it initiates the feelings of defecation.
Ampulla
What are the boundaries of the ischioanal fossa?
- Superiorly: Levator ani
- Inferiorly: Skin
- Laterally: Obturator internus and its fascia and the ischial tuberosity
NOTE: The center part of the ischioanal fossa is the rectum and anal canal
What are the contents of the ischioanal fossa?
- Anus
- Pudenal canal
- Pudendal nerve
- Internal pudenal artery and vein
- Fat
- Supports anus and allows the canal to expand during defecation
- Iliococcygeus muscle
NOTE: The pudendal nerve has a branch coming off called the inferior rectal nerve that is going to go through the fat and innervate the external anal sphincter
How do the two anal sphincters differ?
-
Internal anal sphincter
- Smooth muscle
- Innervation: Pelvic splanchnic nerves
-
External anal spincter
- Skeletal muscle
- Innervation: Inferior rectal nerve of the pudendal nerve
NOTE: The function of the spinal cord in an unconscious person can be assessed by inserting a finger into the anus and testing the muscle tone of the sphincters
The pelvic splanchic nerves come off the sacral plexus at S2,3,4 because that is where the parasympathetic nervous system originates. These nerves join the ____________ and form the rectal plexus.
Inferior hypogastric plexus
The pudendal nerve arises from which spinal cord levels?
S2,3,4
The specific part of the hindgut that givers rise to the rectum is the _________.
Cloaca
The hindgut has a large expansion called the cloaca. The large expansion starts to be separated by a proliferation of cells called the _______.
Urorectal septum
NOTE: These cells grow faster than other cells around it and form a partition across the cloaca, dividing it into the anorectal canal and urinary bladder.
The anal membrane is lined with:
- Endoderm
- Ectoderm
NOTE: Optimally, when the child is born the anal membrane gets perforated and allows access of the hindgut to the outside world.
Label
The remnants of the panal membrane is the ________.
Pectinate line
NOTE: Everything above the line is part of the cloaca/derived from hindgut (endoderm) and everything below the line is from ectoderm.
If you dissect through the anal columns, you will find the _______ veins.
Superior rectal veins
Label
NOTE: There are glands that secrete a mucus like secretion into the anal sinus so that when a person defecates it compresses the anal sinus and all the mucus like liquids will leak out and help lubricate the lower part of the anal canal to facilitate defecation and prevent damage to the anal canal.
Distinguish the cells and innervation above and below the pectinate line.
Above the pectinate line
- Simple columnar epithelium
- GVA innervation (inferior hypogastric plexus)
Below the pectinate line
- Stratified squamous epithelium
- GSA innervation (pudendal nerve)
NOTE: GVA fibers are not really sensitive to pain but are sensitive to stretch. GSA fibers are very sensitive to ALL sensory modalities.
Distinguish between the lymph drainage above and below the pectinate line.
Above
- Internal iliac lymph nodes
Below
- Superficial inguinal lymph nodes
Distinguish between the blood supply above and below the pectinate line.
Above
- Superior rectal artery and vein
Below
- Inferior rectal artery and vein
NOTE: Dilation of the superior rectal vein can result in internal hemorrhoids and dilation of the inferior rectal vein can result in external hemmorhoids.
The middle rectal vein drains the ___ and ____.
Rectum; anal canal
Where does the superior rectal vein drain into?
The superior rectal vein drains into the inferior mesenteric vein, which drains into the splenic vein, which drains into the portal vein
NOTE: The inferior rectal vein drains in the internal pudenal vein
What are possible causes of internal hemorrhoids?
- Portal hypertension
- Constipation
- Genetic predisposition
NOTE: Internal hemorrhoids aren’t usually painful, people don’t know they have them because the sensory innervation above the pectinate line
____________ hemorrhoids are painful.
External
NOTE: External hemorrhoids are not related to portal hypertension because the inferior rectal vein drains into the systemic system.
What are the different types of anal abscesses?
-
Supralevator
- Retrorectal
- Pelvirectal
- Submucous
-
Infralevator
- Ischiorectal
- Intermuscular
- Subcutaneous
- Cutaneous
NOTE: The pelvirectal is the most serous because at some point the pocket of infection is going to spread. If it spreads to the ischioanal fossa it isn’t so serious but if it goes up and erodes away the peritoneal membrane then the infection can get into the pelvic cavity and produce pelvic inflammatory disease (PID) and other conditions and can be life threatening.
A all the pus drains out the abscess resolves but the canal through which it drains will heal and produce a _________.
Fistula
The pudendal nerve and internal pudendal artery and vein run in a canal in the fascia of the ____________ muscle.
Obturator internus muscle
When performing a pudendal nerve block what is the landmark and what structures are anesthesized?
Landmark: Ischial spine
Structures:
- Most of perineum
- Lower vagina
NOTE: Woman can still feel uterine contractions.
Which structures are anesthesized with an ilioinguinal nerve block?
Anterior perineum
What is the course of the pudendal nerve?
- Greater sciatic foramen
- Lesser sciatic formamen
- Pudendal canal
- Urogenital triangle
