Ch.1 - Anatomy Flashcards
Surgical anal canal
- what are the borders?
- who has longer anal canal? Male or female?
- what is the tube within a tube model of the muscular anal canal?
- borders: anal verge (internal/external sphincters) to anorectal ring (puborectalis)
- males have longer anal canal
- two tubes. Outer tube: somatic muscles. Puborectalis and external sphincter
Inner tube: visceral smooth muscle. Internal sphincter and the longitudinal layer innervates by autonomic nervous system
What is ATZ? Where does it begin?
Dentate line marks the true division between what two embryologic layers?
How are the blood vessel/nerve supply/drainage different for parts proximal to the dentate vs. Distal to dentate?
Anal transition zone. 6-12mm proximal to the dentate line.
Dentate line: division between endoderm and ectoderm
Proximal to the dentate: hypogastric (internal iliac). Parasympathetic
Distal to the dentate: inferior henorrhoidal. Somatic nerves
How long and thick is the internal sphincter?
2mm in thickness
35mm in length
What are the three compartments of external anal sphincter. Even though really it’s one continuous muscle
The superficial EAS attached to what bone via what ligament?
Deep: most superior part of the EAS. Continuous with puborectalis and levator ani
Superficial: middle
Subcu: distal
Middle attached to the coccyx via the anococcygeal ligament
Subcu
What innervates the external anal sphincter?
Inferior rectal branch of the pudendal nerve (S2-S3) and by the perineal branch of S4
The perineal body represents the intersection of what muscles?
External anal sphincter
Superficial and deep transverse perinei
Bulbospongiosus
What are the three subdivisions of levator Ani from proximal to distal?
Ileococcygeus
Punococcygeus
Puborectalis
What innervates the levator Ani?
Pudendal nerve branches. S3-S4
Anorectal ring is composed of what things?
Upper border of the internal anal sphincter + puborectalis muscle
What is the most important factor for gross fecal continence?
Contraction of the puborectalis muscle causes a horizontal force that closes the pelvic diaphragm
Which muscle of the levator is usually injured during traumatic vaginal delivery?
Pubococcygeus muscle
From the anal verge, how many cm are lower, middle, and upper rectum?
Lower: 0-7cm
Middle 7-12cm
Upper: 12-15cm
How do you distinguish sigmoid colon vs upper rectum?
Absence of taenia coli and epiploic appendages
Supralevator or retrorectal space refers to space posterior to what structure.
Posterior to retrosacral fascia
Where is denonvillier’s fascia in men and women?
Men: fascia between rectum and seminal vesicles
Women: rectovaginal septum, or rectovaginal fascia
Rectocele represents a defect in [this layer] which allows rectum to bulge anteriorly
Rectocele: defect in rectovaginal septum/fascia or denonvillier’s fascia.
Which anorectal space is the largest?
Ischioanal/ischiorectal space
What are the borders of the ischioanal/ischiorectal space?
Lateral: obturator internus muscle/obturator fascia
Medial: levator Ani muscle
Posterior: lower border of the gluteus maximus and the sacrotuberous ligament
Anterior: deep and superficial transverse perinei
Caudal boundary: skin of the perineum
What are the contents of ischioanal/ischiorectal space?
Pudendal nerve branches
Superficial branches of the internal pudendal vessels
The left and the right ischiorectal space communicate through what space?
Through the deep postanal soace
Which anorectal space is intraperitoneal?
Supralevator space
What are the boundaries of the supralevator space?
Medial: rectum
Lateral: pelvic wall
Inferior: levator
Which anorectal space allows for horseshoe abscess?
Deep postanal space
Deep vs. superficial postanal space
- what separates these two?
Both are below levator Ani and posterior to anus
Deep postanal space: above the anococcygeal ligament
Superficial postanal space: below the anococcygeal ligament
At what point does IMA become superior rectal artery?
Middle rectal artery originates from what?
Inferior rectal artery originates from what?
As the IMA crosses the left common iliac artery
Middle rectal from internal iliac
Inferior rectal from internal pudendal
What innervates the internal anal sphincters?
Sympathetic L5
Parasympathetic S2-S4
Superior rectal artery is a continuation of what artery?
After what anatomic landmark does this artery become superior rectal?
continuation of IMA.
After crossing the left iliac vessels
What is the whole “lateral ligament debate?”
The debate is:
1) does it actually exist? Well yes
2) what do they contain?
Initially middle rectal artery was thought to be in this. But it actually runs posterior to the lateral ligament and the nervi recti fibers (which originate from the inferior hypogastric plexus) course transversely under the lateral ligament to the rectal wall
What is the venous drainage of the rectum?
Superior rectal vein -> drains the rectum + upper anal canal into the portal system
Middle and inferior rectal vein -> systemic via internal iliac vein
What is the lymphatic drainage of the rectum?
What about anal canal?
Upper 2/3 -> inferior mesenteric nodes -> para-aortic lymph nodes
Lower 1/3 -> along the superior rectal artery and laterally along the middle rectal -> internal iliac lymph nodes
Anal canal above the dentate -> inferior mesenteric and internal iliac
Anal canal below the dentate -> along the inferior rectal lymphatics -> superficial inguinal nodes
Sympathetic fibers from what nerve roots innervate the rectum?
Parasympathetic fibers from what nerve roots innervate the rectum and anal canal?
Sympathetic: L1, L2, L3
Parasympathetic: S2-S4
What innervates the external anal sphincters?
Inferior rectal branch of the internal pudendal nerve (S2, S3)
And by the perineal branch of S4
Which nerve mediates the anal sensation?
Inferior rectal branch of the pudendal nerve
What is the generally accepted overall length of the colon?
150cm
Which part of the colon is generally the longest?
Transverse. 45-50cm
Which part of the colon is the narrowest?
Rectosigmoid junction. 2-2.5cm in diameter
Which area represents the border of embryonic midgut and hindgut?
Splenic flexure.
Does middle colic branch early or late?
What does it supply?
What does middle colic originate from?
Branches early
Transverse colon
Middle colic originates from the SMA
The true right colic artery is present in what % of the time?
When present typically arises from what? But can rise from what?
Middle colic arises where?
80%. Absent up to 20% of the time
From SMA typically but alternatively from ileocolic or middle colicmiddle colic rises from the SMA near the inferior border of the pancreas
Marginal artery of drummond can be absent at the splenic flexure in what % of the time?
Up to 50% of the time. Griffith’s point
Foregut and midgut separate at what anatomic structure?
Pancreatic papilla
Embryologic guy development. Explain the three stages and time course
Stage I: physiologic herniation. Between 6-8 wks
Stage II: return to the abdomen during 10th wk. Guts move back in, counterclock fashion 180 degrees
Stage III: Fixation of midgut 12-13wks. Results in duodenum, right and left colon sticking to retroperitoneum
What is Littre’s hernia?
Indirect hernia containing meckel’s
Hirschsprung disease is more common in males or females?
Does it involve the anal sphincters?
Males.
Internal sphincter is always involved
How common is anal stenosis?
What % of children with anal stenosis are symptomatic?
When to do treatment?
25-40% of all infants
Only 25% of them are symptomatic
Dilation in the first 3-6mo of life
