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Anatomy > Rectum And Anal Canal > Flashcards

Rectum And Anal Canal Flashcards

1
Q

Rectum

A

. 5 inches long
. Continuous proximally w/ the sigmoid colon rectosigmoid junction at S3) and distally w/ anal canal (at puborectalis m.)
. Retroperitoneal: sup. 1/3 has peritoneum on ant. And lat. surface, middle 1/3 has it on ant. Surface, inf. 1/3 has no peritoneal covering
. 2 flexures laerally, 3 anteriorly

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2
Q

What is found posterior to rectum?

A

. Last 3 sacral vertebrae and coccyx
. Anococcygeal ligament and piriformis mm.
. Sacral vessels and nerves
. Sympathetic trunks

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3
Q

What structures are directly anterior to rectum?

A

. Males: bladder, ureters, prostate, ductus deferens, seminal vesicles, rectovesical pouch, rectovesical septum
. Females: vagina and uterus, rectouterine pouch, rectouterine (vaginal) septum

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4
Q

What structures are lateral to rectum

A

. Pelvic colon
. Ileum
. Coccygeus
. Levator ani m.

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5
Q

Lateral flexures of rectum

A

. Sacral flexure: rectum following curve of sacrum and coccyx
. Anorectal flexure: rectum ends anteroinferior to tip of coccyx by turning sharply posteroinferiorly as it goes through pelvic diaphragm (angle caused by encircling fibers of puborectalis)

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6
Q

Rectum curvatures

A

. Superior, middle, and inferior curvatures
. Due to 3 internal infoldings of mucous and submucous coats overlying part of circular muscle layer of rectal wall (transverse rectal folds)
. Olds help support rectal contents
. Sup. And inf. Curves are concave to the left
. Middle curve is concave to the right

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7
Q

Anal canal

A

. Inf. 1.5 inches of GI tract
. Continuous w/ rectum at anorectal junction (marked by anorectal flexure)
. Inf. Opening of anal canal: anal orifice/anus

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8
Q

Anatomical relations of the anal canal

A

. Post.: coccyx and anococcygeal ligament
. Ant.: perineal body (central tendon of perineum)
. Lat.: external anal sphincter, ischioanal fossa

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9
Q

Muscular layer of anal canal wall

A

. Internal anal sphincter: thickening of circular smooth muscle layer of rectum under ANS control
. External anal sphincter: voluntary skeletal muscle, subcutaneous portion (directly under skin forming complete ring), superficial portion (elliptical, tip of coccyx/anococcygeal ligament to perineal body)m and deep portion (completely encircles anus)
. Innervated by inf. Rectal n. From pudendal n.

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10
Q

Anal columns

A

. Series of 5-10 longitudinal ridges in anal canal
. Contain terminal branches of sup. Rectal a. And v.
. Anorectal junction indicated by superior ends of anal columns

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11
Q

Anal sinuses

A

. Depressions btw adjacent columns, sup. To anal valves

. When compressed by poo, anal sinuses exude mucus that aids in evacuation of feces

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12
Q

Anal valves

A

. Horizontal folds of tissue, joins inf. Ends of adjacent anal columns

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13
Q

Anal crypt

A

. Inf. Portion of anal sinus
. Deep to anal valve
. Fecal matter can become trapped here causing infection

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14
Q

Pectinate line

A

. Irregular comb-shaped line drawn around circumference of anal canal
. Connects all anal valves
. Sup. To line: from endoderm
. Inf. To line: from ectoderm
. Areas sup, and inf. To line have different blood supply, innervation, and lymph drainage

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15
Q

Sup. Rectal a.

A

. Unpaired
. Terminal branch of inf. Mesenteric a.
. Supplies rectum and sup. Part of anal canal to level of anal columns

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16
Q

Middle rectal a.

A

. Paired
. From internal iliac aa.
. Supplies inf. 1/3 of rectum and anal canal
. Supplies muscular layer of anal canal

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17
Q

Inferior rectal a.

A

. Paired
. From internal pudendal aa.
. Supplies inf. Part of anal canal
. Anastomoses w/ sup. Rectal a. At level of anal columns

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18
Q

Superior rectal v.

A

. Sup. Tp pectinate line
. Drains into portal system via inf. Mesenteric v.
. Inc. portal pressure (portal hypertension) can cause internal hemorrhoids

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19
Q

Middle rectal v.

A

. Drains muscular layer
. Forms anastomoses w/sup. And inf. Rectal vv.
. Drains into internal iliac v.

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20
Q

Inf. Rectal vv.

A

. Inf. To pectinate line

. Drains into internal iliac vv. Via internal pudendal v.

21
Q

Sympathetic innervation of rectum and anal canal

A

. From upper lumbar levels via inf. Mesenteric plexus

. Dec. peristalsis, maintains tone of internal anal sphincter

22
Q

Parasympathetic innervation of rectum and anal canal

A

. From pelvic splanchnics (S2-4) via inf. Hypogastric plexus
. Inc. peristalsis, relaxes internal anal sphincter

23
Q

Sensory innervation sup. To pectinate line

A

. Visceral afferents
. Primarily sensitive to stretching
. Pathology: silent, not painful

24
Q

Sensory innervation inf. To pectinate line

A

. Somatic afferents

. Pathology: painful

25
Q

Lymph drainage sup. To pectinate line compared with inf. To pectinate line

A

. Sup: internal iliac nodes

. Inf: inguinal nodes

26
Q

Difference btw hemorrhoids above and below pectinate line

A

Above: internal hemorrhoids converged w/ mucosa

. Below: external hemorrhoids covered w/ skin

27
Q

Sacral plexus roots

A

. Ventral rami L4-S4
. Comprised fo lumbosacral trunk (L4-55, S1-3, part of S4)
. Ventral rami of S2-3 emerge btw digitations of piriformis m.
. Ventral rami divide into ant. And post. Divisions

28
Q

Sacral plexus muscular branches

A 
. Sciatic n. 
. Pudendal n. 
. Sup. Gluteal n. 
. Inf. Gluteal n. 
. N. To piriformis (S1-2)
. N. To quadratus femoris and inf. Gemellus (L4-5, S1)
. N. To obturator internus and sup. Gemellus (L5, S1-2)
. N. To levator ani and coccygeus (S3-4)
29
Q

Sciatic n.

A

. L4-S3
. Largest branch of sacral plexus
. To lower extremity
. Tibia and common fibular (peroneal) divisions
. Exits greater sciatic foramen to gluteal region inf. To piriformis

30
Q

Pudendal n. (S2-4)

A

. Goes to perineum
. Exits greater sciatic foramen inf. To piriformis
. Courses around sacrospinous ligament, through lesser sciatic foramen, and enters pudendal canal

31
Q

Sup. Gluteal n.

A

. L4-S1
. To gluteal region
. Sup. To piriformis, exits greater sciatic foramen

32
Q

Inferior gluteal n.

A

. To gluteal region

. Inf. To piriformis, exits greater sciatic foramen

33
Q

Cutaneous branch of sacral plexus

A

. Posterior femoral cutaneous n.

. S2-3

34
Q

Sacral sympathetic trunks

A

. Descend on pelvic surface of sacrum med. to ventral sacral foramina
. Preganglionic sympathetic fibers synapse
in sacral sympathetic chain ganglia and Postganglionic fibers travel via gray communicantes to sacral and coccygeal nn. That distribute to body wall
. Preganglionic fibers come off of sympathetic trunk as sacral splanchnics that synapse in inf. Hypogastric plexus and go to viscera

35
Q

Ganglion impar

A

. Midline structure formed by convergence of sacral sympathetic trunks
. Lies in front of coccyx

36
Q

Lumbar sympathetic trunks

A

. Preganglionic sympathetic fibers leave trunk as lumbar splanchnic n.
. Splanchnic nn. Synapse in inf. Mesenteric ganglia and plexus
. Postganglionic sympathetic fibers travel through sup. Hypogastric plexus, inf. Hypogastric plexus, and smaller visceral plexuses and then to viscera

37
Q

Sacral plexus parasympathetic nn.

A

. S2-4
. Pelvic splanchnic nn. (Preganglionic) leave ventral rami
. Joins inf. Hypogastric plexus

38
Q

Superior hypogastric plexus

A

. Formed by inf. Prolongation of aortic plexus
. Divides into R/L hypogastric nn.
. Enter pelvis on either side of pelvis
. Hypogastric nn. Join w. Pelvic splanchnics to form inf. Hypogastric plexus

39
Q

Inferior hypogastric plexus

A

. Gives rise to smaller, specific visceral plexuses

40
Q

Posterior division of iliac a.

A

. 3 parietal branches
. Iliolumbar a.: upward btw obturator n. And lumbosacral trunk
. Lat. sacral a.: descends along ventral sacral foramina, sends spinal branches through foramina to sacral canal, skin, and muscle over sacrum
. Sup. Gluteal a.: btw lumbosacral trunk and S1, exits pelvic cavity through greater sciatic foramen (sup. to piriformis m.)tp gluteal region

41
Q

Anterior division of iliac a.

A 
. 6 branches, parietal and visceral 
. Umbilical a. 
. Inf. Vesical a. 
. Middle rectal a. 
. Obturator a. 
. Internal pudendal a. 
. Inf. Gluteal a.
42
Q

Umbilical a.

A

. Along side wall of pelvis
. Gives off sup. Vesical aa. To bladder
. Becomes medial umbilical ligaments on internal surface of anterolateral abdominal wall after last sup. Vesical branch

43
Q

Inf. Vesical a.

A

. To bladder, ureter (M: seminal vesicles and prostate)

. Gives off a. To vas deferens in male

44
Q

Middle rectal a.

A

. To rectum

. Prostate and seminal vesicles in males too

45
Q

Obturator a.

A

. To med. thigh
. Rounds alongside pelvic wall w/ obturator n.
. Exits pelvis through obturator foramen
. Variation: arises from inf. Epigastric a. In 40% people

46
Q

Inferior gluteal a.

A

. To gluteal region
. Exits pelvis btw S2-3
. Inf. To piriformis m.

47
Q

Male/female differences in branches of internal iliac a.

A

. Females: uterine a. Replaces inf. Vesical a.

. Females have separate vaginal a. That may give off inf. Vesical a.

48
Q

Uterine a.

A

. Courses in base of broad ligament to uterus

. Has ascending and descending branches

49
Q

Pelvic venous drainage

A

. Internal iliac vv and tributaries
. Vv correspond to aa except that iliolumbar vv. Don’t drain into internal iliac vv., but into common iliac vv.
. Anastomoses w/ portal venous system in area of rectum/anal canal

Anatomy (49 decks)

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