18.Rectum and anus

• Rectum


  • About 5 inches long
  • Begins in front of 3rd sacral vertebra, passes downward ends in front of the tip of coccyx – anal canal
  • Rectal ampulla – lower dilated portion
  • Peritoneum covers the anterior & lateral surfaces
  • Main pelvic cavity
  • Valves of Houston
• ANTERIOR


  • MALES: Upper 2/3 - sigmoid colon, coils of ileum that occupy the rectovesical pouch
  • MALES: Lower 1/3 - UB, vas deferens, seminal vesicles, prostate
  • FEMALES: Upper 2/3 - sigmoid colon , coils of ileum that occupy the rectouterine pouch
  • FEMALES: Lower 1/3 – posterior surface of the vagina
• POSTERIOR


  sacrum & coccyx, piriformis, coccygeus, levator ani, sacral plexus and sympathetic trunks
• Blood Supply - Supplied by

  • Superior rectal from IMA
  • middle rectal from internal iliac
  • inferior rectal from internal pudendal
• Blood Supply - Drained by

  • superior rectal – IMV to Portal
  • middle rectal – Internal iliac
  • inferior rectal – Internal pudendal to Internal iliac
• Upper 1/3 rectum


  Tercio superior del recto
• Arterial


  Inferior mesenteric a. → superior rectal a.
• Venous


  Superior rectal v. → inferior mesenteric v. → portal v
• Lymphatic


  Inferior mesenteric l.n.
• Upper 1/3 rectum


  Oberes 1/3 Rektum
• Arterial


  Inferior mesenteric a. → superior rectal a.
• Venous


  Superior rectal v. → inferior mesenteric v. → portal v.
• Lymphatic


  Inferior mesenteric l.n.
• Middle 1/3 Rectum Arterial


  Internal iliac a. → middle rectal a.
• Middle 1/3 Rectum Venous

  Middle rectal v. → internal iliac v.
• Middle 1/3 Rectum Lymphatic


  Internal iliac l.n.
• Lower 1/3 Rectum Arterial

  Internal pudendal a. → inferior rectal a.
• Lower 1/3 Rectum Venous

  Inferior rectal vein → internal pudendal v.
• Lower 1/3 Rectum Lymphatic


  Internal iliac l.n.
• Rectal Examination


  • Posterior - Sacrum and Coccyx
  • Lateral – Ischiorectal fossa and Ischial Spines
• Clinical Correlation


  In both sexes
• Male reproductive anatomy


  • Surface of bladder
  • Seminal vesicle
  • Vas deferens
  • Prostate
  • Perineal body
  • UG diaphragm
  • Bulb of penis
• Female anatomy


  • Rectouterine pouch
  • Vagina
  • Cervix
  • UG diaphragm
  • Perineal body
• Anal canal


  • Approximately 1 1/2 inches (4 cm) long
  • Begins where the rectal ampulla narrows at the level of the U-shaped sling formed by puborectalis muscle
  • Located in perineum
  • Begins at level of puborectalis up to the anus
  • Normally collapsed except during defecation
• Dentate line


  Separates the canal into 2 segments each with different embryonic origin, blood supply and innervations
• Pectinate/anorectal/dentate line indicates the junction between superior and inferior part
• Anal columns of Morgagni
• The anal canal is sensitive to pain, temperature, touch, and pressure
• Upper part anal canal

  • Derived from hindgut endoderm
  • Lined by columnar epithelium
  • With anal columns
  • Sensitive to stretch
  • Supplied & drained by superior rectal
  • Lymphatic drainage is to inferior mesenteric LN
• Lower part anal canal

  • Derived from ectoderm
  • Lined by stratified squamous epithelium
  • Without anal columns
  • Sensitive to pain, temperature, touch, pressure
  • Supplied & drained by Inferior rectal
  • Lymphatic drainage is to Superficial Inguinal LN
• Anatomic anal canal


  Begins from the dentate line and ends at the anal verge
• Surgical anal canal


  Begins from the anorectal ring or junction and ends at the anal verge
• External hemorrhoids


  Located distal to the entate lline and are covered with anoderm
• Internal hemorrhoids


  Painless protrusions of the anal canal covered by mucosa; contain dilated veins of the internal rectal venous plexus
• External hemorrhoids


  Painful enlargements covered by skin that contain dilated veins of the external rectal venous plexus
• Internal hemorrhoids


  Located proximal to the dentate line and covered by insensate anorectal mucosa
• Internal hemorrhoids grading


  Graded according to the extent of prolapse
• Hemorrhoidal cushions


  • Left lateral
  • Right anterior
  • Right posterior
• External hemorrhoids


  Located distal to the entate lline and covered with anoderm
• Internal hemorrhoids


  Located proximal to the dentate line and covered by insensate anorectal mucosa