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Pelvic Floor Physical Therapy > Anorectal Anatomy > Flashcards

Anorectal Anatomy Flashcards

1
Q

Colon structure

A
  • roughly arches around the loops of the small intestine
  • length is variable: average 150 cm (about 1/4 the length of the small intestine)
  • diameter gradually decreases from 7.5cm at the cecum to 2.5cm at the sigmoid – diameter can be greatly augmented by distension
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2
Q

colon distinct characteristics (3)

A

Teniae Coli:

  • represent thicker bands of the outer longitudinal coat of the muscle that traverse the colon
  • anterior, posteromedial, and posterolateral

Haustra:

  • sacculations or outpouchings of bowel wall between the teniae
  • caused by the relative shortness of the teniae: approximately one-sixth shorter than the length of the bowel wall

Appendices epiploicae:
- small appendages of fat that protrude from the serosal aspect of the colon

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3
Q

Colon segments:

A
  • cecum
  • appendix
  • ascending colon
  • transverse colon
  • descending colon
  • sigmoid colon
  • rectosigmoid junction
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4
Q

Rectum

A
  • 12-15cm long: starts at level of S3, and ends 2-3 cm below the coccyx
  • no haustra located in rectum
  • superior, middle, and inferior rectal folds (valves of Houston) – support the weight of feval matter and prevent movement toward the anus
  • ampulla: storage vessel – bottom 2/3s of the rectum is most distensible
  • smooth muscle: muscularis mucosa, inner circular layer – forms rectal valves (valves of Huston) proximally – extends into anal canal becoming the internal anal spinchter (IAS, outer longitudinal layer – surrounds sigmoid colon forming thicker bands of taenia coli
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5
Q

Taenia Coli

A

extend from rectum into anal canal becoming the conjoined longitudinal muscle

  • combination of outer longitudinal layer and fibers of levator ani (LA) – smooth and striated muscle components
  • descends between the IAS and EAS – serves as a bridge muscle
  • with fibers ultimately traversing lowermost part of EAS to insert into perianal skin – muscle fibers referred to as “corrugator cutis ani muscle”
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6
Q

potential spaces associated with rectum:

A
  • Rectouterine pouch (Pouch of douglas) – between rectum and uterus –common site for endometrial implants
  • Rectovesical space: between rectum and the male bladder
  • presacral space: b/w the rectum and sacrum, cranial to LA; site of possible supralevato abscess
  • ischiorectal fossa: between obturator internus and LA at ischium, adjacent to pudendal canal, communication around anal sphincter, potential for abscesses and infections
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7
Q

Sensation:

A
  • rectal distension is sensed by the fascia surrounding rectum and receptors in rectal lining
  • sampling reflex: highly sensitive lining samples the material to differentiate b/w liquid, gas, and solid
  • < 15cm rectal distension or less sensed as flatus, while more than 15cm rectal distension causes abdominal discomfort
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8
Q

Arterial supply:

A
  • superior rectal artery – from mesenteric artery
  • medial rectal artery – branch of hypogastric artery
  • inferior rectal artery – branch of pudendal artery
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9
Q

Superior rectal artery supply

A

supplies superior aspect of anus to pectinate line

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10
Q

medial rectal artery supply

A

anastomosis superior to inferior rectal arteries

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11
Q

inferior rectal artery supply

A

anus below pectinate line.

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12
Q

Veins

A
  • similar to arteries
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13
Q

anal cushions (lohsiriwat, 2012)

A

Three major anal cushions of the anal canal (vairous minor cusions between major)

  • R anterior
  • R posterior
  • L lateral
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14
Q

Hemorrhoids

A
  • prolapsed blood vessels

- recognized as very common cause of rectal bleeding and anal discomfort

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15
Q

When do hemorrhoids develop?

A

when supporting tissue of anal cushions deteriorate

- abnormal downward displacement of anal cushions causes venous dilation

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16
Q

internal hemorrhoids origin, location, pain:

A
  • origin = from internal hemorrhoidal plexus
  • location = above dentate line
    = generally not painful (unless 4th degree that become strangulated)
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17
Q

external hemorrhoids origin, location, pain:

A
  • location = below gentate line

- generally painful with presence of thrombosis

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18
Q

Hemorrhoid color meaning:

A
  • red = active
  • blue = latent
  • skin tag = empty
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19
Q

mixed (internal/external) hemorrhoids:

A
  • below and above dentate line
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20
Q

Hemorrhoids epidemiology

A

true epidemiology unknown because of the tendency to self-medicate rather than seek medical attention
- constipation/prolonged straining contribute because of increased IAP – could cause obstruction of venous return, thus engorgement of hermorrhoidal plexus

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21
Q

Anus

A
  • 3-4cm long starting at levator ani muscles
    • 2.5cm below tip of coccyx flexing posterior from rectum
  • anal verge = caudal margin with corrugated folds of skin
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22
Q

Describe the boundaries of the anal triangle

A

anteriorly = superficial transverse perineal muscles adjoining at the perineal body

laterally = sacrotuberous ligaments

posteriorly = coccyx

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23
Q

Contents of the anal triangle:

A
  • anal canal (IAS, EAS)
  • anal orifice/opening
  • ischiorectal fossa
  • alcock’s canal
  • pelvic floor muscles
  • sabaceous glands
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24
Q

What is the anorectal ring?

A

muscular ring at the anorectal junction comprised of EAS, IAS, and puborectalis (PR)

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25
Q

Internal Anal Sphincter

A
  • inner circular smooth muscular layer of rectum

- continues into the EAS as a thickening of the circular muscle

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26
Q

IAS innervation:

A
  • sumpathetic = L1-2 via the hypogastric plexus
  • parasympathetic = through S1-3 via the pelvic plexus
  • contains interstitial cells of cajal that may serve as pacemaker cells
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27
Q

IAS function:

A
  • accounts for 50% to 85% of resting pressure in the anus
  • EAS accounts for 25-30%
  • remaining 15% accounted for by hemorrhoidal plexus
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28
Q

Longitudinal muscle

A
  • attachment = runs along the IAS and into the inferior EAS
  • function = contraction phase: lifts and elevates IAS; relaxation phase: LM lets down the subcutaneous part of the EAS and increases the tension of the anococcygeal ligament
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29
Q

Puboanalis of LA

A

attachments: pubis to anal skin between internal and external anal sphincters
- function: elevates anus and skin in regions

30
Q

intersphincteric fascial plane:

A

derived from longitudinal layer of the rectum

31
Q

EAS

A

attachments:
- anterior perineal body and supericial transverse perineal muscle
- posterior to anococcygeal raphe

function:

  • part of the voluntary sphincter of the anal canal
  • provides 25-30% resting tone of anus
32
Q

Levator Ani muscles

A
  • pubococcygeus/pubovisceral muscle
  • illiococcygeus
  • coccygeus
  • puborectalis
33
Q

pubococcygeus/pubovisceral muscle

A

origin = dorsal surface of pubic bone/fascia of obturator internus and

insertion = into annococcygeal raphe

located slightly lateral to puborectalis

function: supports the pelvic viscera

34
Q

illiococcygeus

A

origin = arcus tendinous levator ani

insertion = into annococcygeal raphe/coccyx

function: supports the pelvic viscera and coccyx

35
Q

coccygeus

A

origin = ischial spine

insertion = into anococcygeal body/coccyx/sacrum

function:

  • supports pelvic viscera/coccyx
  • flexes the coccyx
36
Q

puborectalis attachments

A

origin = no posterior attachment; posterior pubic bone, 3 cm above the arcus tendinous levator ani, from there the PR slings around the rectum back to the pubis to lasso the anorectum

37
Q

puborectalis functions:

A
  1. spinchter-like in nature:
    - contraction = decrease the anorectal angle (aids fecal continence by grossly kinking off the anorectal junction)
    - slips muscle attach into the vaginal and rectal muscularis
  2. contracts simulataneously with EAS with cough and strain to further optimize the continence mechanism
  3. despite continence meachanism relationship, evidence suggests that the PR is anatomically part of the LA (wallner et al., 2008)
    - Histochemically stained serial sections of human fetuses showed that the pubococcygeus and puborectalis have intervening and inseparable muscle fibers at pubic origin
    - puborectalis/EAS appear at different time points during development
    - they have differnet nerve innervations
38
Q

puborectalis and other LA muscles innervation:

A

LA nerves

39
Q

EAS innervation

A

pudendal nerve with minor innervation from LA

40
Q

OASIs

A

Obsteric anal sphincter injuries

41
Q

OASIs info

A
  • 3rd or 4th degree tears to anal sphincter

- rate of OASI varied from .6%-10.2%

42
Q

Risk factors for OASIs:

A
  • nulliparity
  • midline episiotomy
  • operative vaginal birth: forceps or vacuum
  • epidural analgesia
  • advancing maternal age
  • fetal position occipital posterior
  • shoulder dystocia
  • increased birth weight
  • longer second stage of labor
43
Q

effects of OASIs:

A
  • between 1/3 to 2/3 of participants who sustained 3rd degree tears suffered from fecal incontinence (Frank & Erxleben, 2015)
  • Participants with prior OASIs during birth were 3x greater risk of laceration during subsequent births
  • Paricipants diagnosed with OASIs were 2x as likely to experience FI in the postpartum period
44
Q

Sex difference of anal sphincter:

A
  • EAS shorter in women than men
  • superficial transverse perineal muscle more superiorly oriented in women than men
  • Men have the central perineal tendon where muscle fibers insert while women have the perineal body where muscle fibers overlap
45
Q

Age differences in anal sphincter

A
  • thickening of IAS with increased CT
  • EAS atrophy (especially in men)
  • caution in differential do between pathological EAS changes vs. changes associated with normal aging
  • reduced thickness of longitudinal muscle
46
Q

Levator/Urogenital hiatus

A
  • hernial portal through which female organ prolapse develops
  • opening within LA muscles through which the urethra and vagina pass, as well as rectum
47
Q

T/F: males have a urogenital hiatus

A

False

48
Q

Levator/Urogenital hiatus support

A
  • anteriorly = pubic bones and LA muscles

- posteriorly by perineal body and EAS

49
Q

Levator/Urogenital hiatus baseline activity levels

A

keeps levator hiatus closed by compressing vagina, urethra, and rectum:

  • pelvic floor and organs compress toward cephalic direction
  • diameter narrows with puborectalis contraction
50
Q

What makes the Levator/Urogenital hiatus diameter narrow?

A

contraction of puborectalis

51
Q

Which direction do the pelvic floor muscles compress in the Levator/Urogenital hiatus?

A

cephalic

52
Q

EVIDENCE concerning LA abnormalities and underactive PFM

Falkert, Endress, Weigl, & Seelbach-Göbel, 2010

A
  • 53.8% of women with underactive PFM contraction had LAA vs. 16.1% of women with normal PFM contraction
  • Women w underactive PFM were less likely to reduce hiatal size (mean 7%) vs. 25% of participants with normal PFM
  • underactive PFM contraction was associated with stress urinary incontinence but not fecal incontinence or anterior prolapse
53
Q

EVIDENCE: Correlation between mode of birth and persisting pelvic floor disorders 18-24 months after
first birth assessed by 3D ultrasound (Falkert, Willmann, Endress, Meint, & Seelbach-Göbel,
2013)

A
  • prospective observational study of 130 primiparous women
  • spontaneous or operative vaginal first birth resulted in significantly larger hiatal area and axial distension than cesarean
  • participants with persisting stress urinary incontinence after 2 years following birth had larger hiatal areas than those without SUI
54
Q

Nerve supply of GI and bowel function

A
  • enteric nervous system

- CNS

55
Q

enteric nervous system

A
  • located within the wall of the GI tract
  • works w the CNS and neural pathways through sympathetic ganglia to control digestive function
  • contains 200-600 million neurons in humans: – Myenteric system: extends from the upper esophagus to the internal anal sphincter; Submucosal plexus: located in the small and large intestines, but not in stomach and esophagus
56
Q

connections b/w the ENS and CNS are carried by:

A

vagus and pelvic nerves and sympathetic pathways

57
Q

Roles of CNS along the GI tract:

A
  • striated muscle movement in the esophagus
  • stomach contractility and acid secretions through vagovagal reflexes
  • defecation via centers in the lumbosacral spinal cord
58
Q

Roles of ENS along the GI tract:

A
  • smooth muscle activity of small intestine and colon
  • transmucosal fluid flux
  • local organ blood flow
59
Q

What is Onuf’s nucleus?

A
  • distinct group of neurons located in anterior horn of sacral spinal cord responsible for bowel and bladder control
  • Primarily S2, but can run from S1-S3
  • Although neurons supply striated muscle, they are smaller than average alpha-motor neurons and resemble autonomic nerves
  • travel in pudendal nerve
60
Q

Pudendal nerve origin

A

originates at S2, S3, S4

61
Q

pudendal nerve supplies:

A
  • 70% somatic
  • 50% sensory
  • 20% motor
  • 30% autonomic = responsible for maintaining a degree of tone in the PFMs to facilitate continence
62
Q

3 branches of pudendal nerve:

A
  1. Inferior rectal nerve (inferior hemorrhoidal, inferior anal nerve)
  2. Perineal Nerve
  3. Dorsal nerve of the penis/clitoris
63
Q

Inferior Rectal Nerve branch:

A
  • may arise at the sacrospinous ligament, before Alcock’s canal, in Alcock’s canal, or after alcock’s canal
  • Sensation to: distal aspect of anal canal, perianal skin, may supply sensory branch to lower vagina in females
  • Motor to: EAS
  • communicates with the terminal branch of the perineal nerve, the labial/scrotal nerve
64
Q

Perineal Nerve branch origin/path:

A
  • runs inferiorly in alcock’s canal and divides into posterior labial/scrotal branches (sensory) that overlap with the posterior femoral cutaneous nerve, inferior rectal nerve, and motor branches
65
Q

Perineal Nerve branch sensation:

A

perineum, ipsilateral posterior surface of the labia majora/scrotum, skin of the lower vagina in females

66
Q

Perineal Nerve branch motor:

A
  • superficial and deep transverse perineal muscles
  • bulbocavernosus
  • ischiocavernosus
  • external urethral sphincter
  • anterior portion of the external anal sphincter
  • levator ani
67
Q

Dorsal nerve of the penis/clitoris origin:

A

origin: emerges underneath the inferior pubic rami, turns sharply cephalad and travels b/w the ischiocavernosus muscle and inferior margin of the inferior pubic rami.

68
Q

Dorsal nerve of the penis/clitoris sensory:

A

afferent nerve carrying sensory information from the clitoris/penis

69
Q

Dorsal nerve of the penis/clitoris function:

A

responsible for erection and sensation of desire to urinate

70
Q

Other Pelvic floor ANS input:

A

Autonomic input:

  • sympathetic (L1-3) = superior hypogastric plexus
  • parasympathetic

Pelvic Floor Physical Therapy (11 decks)

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