Lecture 15- Rectum and anal canal anatomy

Question 1

how long is the rectum

Answer 1

12-15cm long passes through the pelvic floor

Question 2

anatomy of the rectum

Answer 2

• Has a continuous band of outer longitudinal muscle
• Curved shape anterior to sacrum
• Parts covered in peritoneum (some parts extraperitoneal)

Question 3

function of the rectum

Question 4

where does the anal canal start

Answer 4

• Starts at the proximal border of the anal sphincter complex

Question 5

anatomy of the anal canal

Answer 5

• Rectum points anteriorly
• Puborectalis sling changes the direction of anatomy
• Ana canal points posteriorly

Question 6

Anal is involved in continence

• Factors required:

Answer 6

• Distensible rectum
• Firm bulky faeces
• Normal anorectal angle
• Anal cushions
• Normal anal sphincters

Question 7

blood supply the rectum

Answer 7

blood supply to rectum is from sevral arteries that for a plexus

• superior rectal artery
• middle rectal artery
• inferiro rectal

Question 8

superior rectal artery is a continuation of the

Answer 8

inferior mesenteric artery

Question 9

middle rectal artery is a continuation of the

Answer 9

internal iliac

Question 10

inferior rectal artery is a contiuation of the

Answer 10

pudendal artery

Question 11

venous drainage of the rectum

Answer 11

• portal draiange through superior rectal vein
• systemic driange through internal iliac vein
  
  • portional for porto-systemic anastomosis

Question 12

anal sphincter complex comprises

Answer 12

• internal involuntary sphincter
• external anal sphincter

Question 13

internal involuntary sphincter

Answer 13

• thickening of circular smooth muscle
• under autonomic control (80% of resting anal pressure)

Question 14

External anal sphincter is

Answer 14

striated muscle–> under more voluntary control

Question 15

• External anal sphincter is striated muscle

Answer 15

• Deep section
  
  • Upper anal canal
  • Mixes with fibres from Levator ani
  • Joins with puborectalis to form sling
• Superficial and subcutaneous section
• Nerve supply- pudendal nerve- conscious control
• 20% of resting pressure

Question 16

process of dafaecation

Answer 16

1. mass movement
2. defecation reflex
   
   • stimulus= distension in rectum
   • responses
     
     • contraction in rectum and sigmoid colon
     • relaxation of internal anal sphincter
     • contraction of external anal sphincter
3. increased pressure in rectum
4. delay of defaecate
5. delay
   
   • contraction of external anal sphincter
   • contraction of puborectalis muscle
   • reverse peristalsis in rectum
6. defaecate
   
   • relaxation of external anal sphincter
   • relaxation of puborectalsis muscle
   • forward peristalisis in rectum and sigmoid colon
   • valsalva maneuver (increased abdominal pressure)

Question 17

valsalva maneuver

Answer 17

increased abdominal pressure

Question 18

where is the dentate canal found

Answer 18

the anal canal

Question 19

what is the dentate line in the anal canal

Answer 19

junction of hindgut and proctodaeum (ectoderm)

Question 20

above the dentate line what sort of pain receptors are there

Answer 20

visceral pain receptors

Question 21

above the dentate line what sort of cells are found

Answer 21

columnar epithelium

Question 22

below the dentate line what sort of pain receptors are found

Answer 22

somatic pain receptors

Question 23

below the dentate line what sort of epithelium is found

Answer 23

stratified squamous epithelia

Question 24

visceral opain receptors type of pain

Answer 24

vague, not localized

Question 25

somatic pain

Answer 25

sharp well localised- very painful

Question 26

haemorrhoids are caused by

Answer 26

problems with anal cushions

Question 27

anal cushions

Answer 27

* (PLEXUS OF BLOOD VESSELS FORMS PART OF CONTINCNECE)

Question 28

plexus of blood vessels which form anal cushions

Answer 28

* Divided into 3+ areas of tissues called anal cushions * posterior * antirior * lateral * Play a role in anal continence * There are connections between the veins and some arteries * Present from birth and a normal finding

Question 29

haemorrhoids can be classified as...

Answer 29

internal or external haemorrhoids

Question 30

**Internal haemorrhoids found**

Answer 30

above the dentate line

Question 31

external haemorrhoids

Answer 31

found below the haemorrhoid line

Question 32

features of internal haemorrhoids

Answer 32

* Loss of connective tissue support * Above dentate line * Relatively **painless** * Enlarge and prolapse through anal canal * **Bleed bright red blood** * **Pruritus’**

Question 33

treatment for internal haemorrrhoids

Answer 33

* Increased hydration/ high fibre diet - soften stool * Avoid straining * Rubber band ligation * Surgery

Question 34

grading of haemorrhoid: grade 1

Answer 34

no prolapse just prominent blood vessels

Question 35

stage 2 internal hameorrhoids

Answer 35

prolapse upon bearing down, but spontaenous reduction

Question 36

grade 3 internal haemorrhoids

Answer 36

prolapse upon bearing down requiring manual reduction

Question 37

stage 4 intenral haemorrhoid

Answer 37

prolapse with inability to be manually reduced

Question 38

external haemorrhoids are found

Answer 38

below dentate line

Question 39

features of external hameorrhoids

Answer 39

* below dentate line * swelling o anal cushions which may then thrombose * painful ++ * surgery has good outcome

Question 40

anal fissure

Answer 40

linear tear in andoderm (usually posterior midline)

Question 41

cause of anal fissure

Answer 41

* High internal and sphincter tone * Reduced blood flow to anal mucosa * passing of hard stool

Question 42

symtoms of anal fissure

Answer 42

* Pain on defaecation ++ * **Haematochezia**

Question 43

* Haematochezia

Answer 43

Hematochezia is the passage of fresh blood per anus, usually in or with stools.

Question 44

causes of haemotochezia most common

Answer 44

diverticulitis

Question 45

other causes of haematochexia

Answer 45

* Diverticulitis’s * Angiodysplasia (small vascular malformation in boewl wall) * Colitis * IBD * Infective * Colorectal cancer * Anorectal disease * Haemorrhoids * Anal fissure * Upper GI bleeding (least common) * Large bleed with fast transit

Question 46

malaena

Answer 46

* Black tarry stools * Offensive smelling * Due to Hb being altered by digestive enzymes and gut bacteria

Question 47

* Common causes of melaena

Answer 47

* Upper GI bleeding * Peptic ulcer disease * Variceal bleeds * Upper GI malignancy * Oesophageal/ gastric cancer

Question 48

* Uncommon causes of melaena

Answer 48

* Gastritis * Meckels diverticulum * Iron supplements