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Y2S2-Anatomy-GI > Anatomy of the rectum and anal canal > Flashcards

Anatomy of the rectum and anal canal Flashcards

1
Q

What forms the bony pelvis?

A

Two hip bones that are separated by the sacrum posteriorly and meets anteriorly at the symphysis pubis

  • The pelvic cavity is continuous with the abdominal cavity (their is no diaphragm in between)
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2
Q

What are the joints of the pelvis?

A

1) Symphysis pubis (secondary cartilage)

2) Sacroiliac joint (synovial plane joint)

  • They allow little movement of the pelvis
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3
Q

What is the pelvic inlet?

A

It is a line that passes from the upper border of the symphysis pubis to the sacral promontory

  • Above the pelvic inlet it is called as the false pelvis (part of the abdominal cavity), and below this line it is called the true pelvis
  • The true pelvis has an inlet & outlet, the inlet is at the brim, while the outlet is closed by the pelvis diaphragm (pelvic diaphragm separates the pelvis from the perineum)
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4
Q

What is the pelvic brim?

A
  • It marks the distention between the greater pelvis (false pelvis) and the lesser pelvis (true pelvis)
  • The greater pelvis is part of the abdominal cavity
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5
Q

What is the pelvic outlet?

A

It is a line that passes from the lower border of the symphysis pubis to the tip of the coccyx

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6
Q

Where does the true pelvis lie?

A

Between the pelvic inlet and the outlet

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7
Q

What is the pelvic diaphragm?

A
  • The bony pelvis is lined with muscles (laterally, posteriorly, and inferiorly)
  • The inferior muscles is the pelvic diaphragm which separates he contents of the pelvis from the perineum
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8
Q

What happens to the abdominal pressure when the pelvic diaphragm contract?

A

It increases

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9
Q

What are the muscles that forms the pelvic diaphragm?

A

1) Levator ani

2) Coccygeus

  • Along with their superior and inferior fascia
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10
Q

What are the muscles that covers the lateral wall of the pelvis?

A

1) Piriformis

2) Obturator internus

  • Along with their fascia
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11
Q

What is the piriformis muscle?

A
  • One of the small lateral rotators of the thigh
  • It originates from the anterior 3 sacral pieces, passing through the greater sciatic notch to insert in the upper border of the greater trochanter
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12
Q

What is the obturator internus?

A
  • It is one of the small lateral rotators of the thigh, the inner surface of the obturator membrane insert into the greater trochanter
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13
Q

What is the function of the pelvic diaphragm?

A
  • It is the pelvic floor that holds in and supports the viscera
  • Beneath it is the perineum
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14
Q

What is the origin of the perineum?

A

The tip of the ischial spine

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15
Q

Where is the coccygeus inserted?

A

At the side of the last piece of the sacrum and the first piece of the coccyx

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16
Q

What is the nerve supply of the coccygeus?

A

Lower sacral nerve

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17
Q

What is the action of the coccygeus?

A

It does not have a action in humans, however in animals is moves the coccyx and tail

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18
Q

What is the origin of the levator ani muscle?

A

1) The posterior surface of the body of the pubis

2) The upper thickened part of the obturator fascia

3) Ischial spine

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19
Q

Where is the levator ani muscle inserted into?

A
  • It has 3 origins and thus

1) Perineal body (where two of the origins meet medially, anterior to the anal canal)

2) The side wall of the anal canal

3) The anococcygeal body (where two of the origins meets medially, posterior to the anal canal)

4) The tip of the coccyx

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20
Q

What are the different parts of the levator ani muscle?

A

1) Puborectalis

2) Pubococcygeus (sphincter vaginae in females, or levator prostate in males)

3) Ileococcygeus

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21
Q

What is the puborectalis?

A
  • It is a U-shaped sling, which extends from the body of the pubic bone, past the urogenital hiatus and around the anal canal
  • Its main function is to maintain fecal continence (during defecation this muscle relaxes)
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22
Q

What is the pubococcygeus (sphincter vaginae)?

A

They are from the fibers the divides and loops around the prostate in males (levator prostate) and the vagina in females (pubovaginalis)

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23
Q

What is the iliococcygeus?

A

Its a part of the levator ani muscle that starts anteriorly at the ischial spine and the posterior aspect of the tendinous arch, posteriorly they attach to the coccyx and the anococcygeal ligament

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24
Q

What is the nerve supply of the levator ani muscle?

A

1) The pelvic surface is supplied by the lower sacral and coccygeal nerve

2) The Perineal surface is supplied by the inferior rectal nerve (which is a branch of the pudendal nerve)

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25
Q

What is the action of the levator ani muscle?

A

1) It raises the intra-abdominal pressure during forces expiration and expulsive acts (like defecation, cough and vomiting)

2) The anterior fibers (levator prostate, pubovaginalis, or sphincter vag forms a sling around the prostate or the vagina which acta as a sphincter for the vagina

3) The puborectalis closes the rectal/anal junction and reinforces the external anal sphincter, and it also maintains the fecal continence

  • The puborectalis muscle relaxes while squatting (and thus the squatting position helps in the full excavation of the rectum)
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26
Q

A damage to the pelvic floor can result in which condition?

A

Incontinence

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27
Q

What is the name of the pelvic tissue that surrounds the pelvic organs providing it with support and protection?

A

The pelvic fascia

28
Q

What are the pelvic organs?

A
  • Most anterior

1) Pubic symphysis

2) Urinary bladder withe the urethra

3) Uterus and the vagina in females

4) Rectum with the anal canal

5) Sacrum

  • Most posterior
29
Q

What covers the male pelvic organs?

A

The peritoneum of the anterior abdominal wall covers some of the pelvic organs including

1) The superior surface of the urinary bladder and the upper part of its posterior surface

2) The anterior and side parts of the upper part of the rectum

3) The anterior part of the middle of the rectum

  • The lower part of the rectum is not covered
  • A recto-vesical pouch is formed as the peritoneum reflects to cover the rectum
30
Q

The anterior abdominal wall peritoneum covers which female pelvic organs?

A

1) Superior surface of the urinary bladder except for a small portion posteriorly

  • It then forms a pouch between the urinary bladder and the uterus called (utero-vesical pouch)

2) It then covers the anterior surface of the body of the uterus, its fundus, the posterior surface of its body, the posterior surface of the “supra-vaginal” cervix, and the upper part of the vagins

  • It then reflects on the rectum forming the recto-vaginal pouch

3) Then it covers the front and sides of the upper 1/3 of the rectum, anterior part of the mid rectum, and it does not cover the lower rectum

31
Q

What is the peritoneal covering of the vagina?

A

Only the upper part of its posterior surface

32
Q

What is the peritoneal covering of the uterus?

A
  • The fundus fully
  • The body of the uterus (anteriorly and posteriorly)
  • Only the supra-vaginal portion of the cervix posteriorly
33
Q

At which location does the rectum begin?

A

At the 3rd sacral piece as a continuation of the pelvic colon

34
Q

Where does the rectum ends?

A

About 1-inch in front and below the tip of the coccyx where it becomes continuous with the anal canal

35
Q

What are the general features of the rectum?

A

1) Sacral curvature

  • It is curved following the concavity of the sacrum and the coccyx

2) Lateral curvature

  • The upper part forms 3 lateral flexures, where the upper and lower flexures are concave to the left, while the middle one is concave to the right (however the beginning and end of the rectum lies at the median plane)

3) Perineal curvature

  • At the junction of the rectum and the anal canal, and it s directed forward, unlike the other parts it does not show appendices, epiploica, taenia coli and sacculations (CAR (cecum, appendix, rectum) don’t have appendices epiploicae, while AR (appendix, rectum) don’t have appendices epiploicae, tenia coli, sacculations)

4) Its lower part is dilated to form the rectal ampulla

36
Q

What is the ampulla of the rectum?

A

It is the dilation of the lower part of the rectum

37
Q

How is the peritoneum related to the rectum?

A

1) The upper 1/3 (Front and sides only)

2) The middle 1/3 (front only)

3) The lower 1/3 has no peritoneal covering

38
Q

What are the anterior visceral relations of the rectum (in females)?

A

1) Above: Rectouterine pouch

2) Below: The posterior wall of the vagins

39
Q

What are the anterior visceral relations of the rectum (in males)?

A

1) Above: The rectovesical pouch

2) Below: The base of the bladder, seminal vesical, ampullae of the vas, the terminal parts of the ureter and prostate

40
Q

What are the lateral (side) relations of the rectum?

A

The pararectal fossa

41
Q

What is the posterior relation of the rectum?

A

1) Sacrum and coccyx

2) Piriformis, coccygeus & levator ani muscles

3) Median sacral vessels

4) Branches of the superior rectal vessels

5) Sympathetic trunks, lower sacral and coccgeal nerves

6) Ganglion impare (it is a solitary retroperitoneal structure located anterior to the sacrococcygeal junction. This ganglion marks the end of the two sympathetic chains and is the only unpaired autonomic ganglion in the body. Gray communicating nerve fibers pass from the ganglion impar to the spinal nerves)

42
Q

What is the blood supply of the rectum?

A

1) Superior rectal artery

2) Middle rectal artery

3) Inferior rectal artery

43
Q

The superior rectal artery is a continuation of which artery?

A

Inferior mesenteric artery

44
Q

Where will the inferior mesenteric artery becomes the superior rectal artery?

A

Once it crosses the left common iliac at the level of L3

45
Q

What is the origin of the middle rectal artery?

A

It is a branch of the anterior division of the internal iliac artery

46
Q

What is the origin of the inferior rectal artery?

A

It is a branch of the internal pudendal artery

47
Q

What is the rectal venous drainage?

A

They correspond to the arteries, and begins from the rectal venous plexus

48
Q

What is the lymphatic drainage of the rectus?

A

1) Pararectal lymph nodes

  • Ascends along the superior rectal vessels

2) Inferior mesenteric lymph nodes

  • Along the sigmoid mesocolon

3) Internal iliac lymph nodes

  • Along the middle rectal vessels
49
Q

Where does the anal canal begins?

A

A continuation of the rectum, 1-inch below and in front of the tip of the coccyx

  • It then passes down and back for 1.5 inch
50
Q

Where does the anal canal ends?

A

The anal orifice

51
Q

What are the anterior relations of the anal canal?

A

Perineal body

1) In males the perineal body will seperate the anal canal from the membranous urethra and the bulb of the penis

2) In females the perineal body separates the anal canal from the lower end of the vagina

52
Q

What is the posterior relation of the anal canal?

A

The Anococcygeal body

  • It separates the anal canal from the tip of the coccyx
53
Q

What is the lateral relation of the anal canal?

A

1) The upper part is related to the levator ani

2) The lower part is related to the ischiorectal fossa (which gives space for the anal canal to expand during defecation)

54
Q

What is the external anal sphincter?

A
  • It is a voluntary striated muscle fiber
  • It surrounds the lower 2/3 of the canal, thus overlapping the internal sphincter in the middle third
55
Q

What are the parts of the external anal sphincter?

A

1) Subcutaneous (no bony attachments)

2) Superficial (between the perineal and the anococcygeal body and the tip of the coccyx)

3) Deep part (around the middle 1/3 of the anal canal)

56
Q

What is the nerve supply of the external anal sphincter?

A

The inferior rectal nerve and the perineal branch of the 4th sacral nerve (somatic since it is a voluntary muscle)

57
Q

What is the action of the external anal sphincter?

A

Continence (voluntary closure of the anal canal)

58
Q

What is the internal anal sphincter?

A
  • It is a smooth muscle fiber
  • It acts involuntary
  • It is formed by the thickening of the gut which surrounds the upper 2/3 of the canal
59
Q

What is the nerve supply of the internal anal sphincter?

A

Sympathetic fiber (from the superior and inferior hypogastric plexuses “autonomic nerve supply”)

60
Q

Describe the anal mucosa

A
  • It shows longitudinal folds which are called (ANAL COLUMNS)
  • The lower end of the anal column are connected with each other via semilunar valves which are called ANAL VALVE
  • Anal valve is found along the WHITE LINE OF HILTON
61
Q

What are the anal columns?

A

Longitudinal folds of the anal mucosa

62
Q

What are the anal valves?

A

semilunar valve that connects the lower ends of the anal columns

63
Q

What are the white line of Hilton?

A
  • It is an indication between the upper endodermal part (lined by the columnar epithelium “and it is insensitive to pain”) and the lower ectodermal part (lined by stratified squamous “highly sensitive to pain”)
  • This line gives attachment to the anal membrane during the fetal life, which separates the upper endodermal part from the lower ectodermal part
64
Q

What is the internal hemorrhoids?

A
  • Due to the breakdown of the muscularis mucosa, a prolapse o the rectal cushions (the rectal mucosa which contains the internal rectal venous plexus “Anastomoses between Portal and systemic circulation”)
  • It occurs in the upper part of the anal canal (which is why it is painless)
  • The patient will come complaining of bleeding and not pain
65
Q

What is an external hemorrhoid?

A
  • Occurs due to the thrombosis of the external rectal venous plexus
  • They are painful as they are covered by skin, and receives somatic sensation
  • Bleeding and pain
66
Q

What is an anal fissure?

A
  • A small tear in the lining of the anal canal causing pain and bleeding
  • It is usually located at the posterior midline inferior to the pectinate line
  • Painful as the region is supplied by sensory somatic fibers
  • Due to the pain spasms occur at the external anal sphincter as the inferior rectal nerve supplies both the lining of the anal canal below the pectinate line and the mucsle

Y2S2-Anatomy-GI (6 decks)

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