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LC Gastroenterology Week 4 > Clinical Anatomy of Faecal Continence – the Distal GI Tract > Flashcards

Clinical Anatomy of Faecal Continence – the Distal GI Tract Flashcards

1
Q

What is the distal Gi tract classed as?

A

The rectum
The anal canal
The anus

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2
Q

What does the control of excretion require?

A

A ‘holding area’ (the rectum) - to store faeces until appropriate defecate

Normal visceral afferent nerve fibres - to sense ‘fullness’ of the rectum

Functioning muscle sphincters - around the distal end of the GI tract to respond to this fullness - - to appropriately contract, preventing defecation, and to relax, allowing defecation

Normal cerebral function to control the appropriate time to defecate

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3
Q

What can affect the control of excretion of faeces?

A

Neurological pathology - dementia, stroke, MS, trauma

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4
Q

What can faecal continence also be affected by?

A

affected by medications

affected by the natural age-related degeneration of nerve innervation of muscle

affected by consistency of stool (harder stool, harder to get out)

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5
Q

Where does the pelvic cavity lie?

A

Lies within the bony pelvis

Lies between the pelvic inlet and pelvic floor

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6
Q

Where is the rectum located?

A

Within the pelvic cavity

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7
Q

What muscle is known as the pelvic floor?

A

The levator ani muscle it forms the musculofascial inferior part of the pelvic cavity

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8
Q

What do openings in the pelvic floor permit?

A

The distal parts of the alimentary, renal and reproductive tracts to pass from the pelvic cavity into the perineum

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9
Q

When does the sigmoid colon become the rectum?

A

Anterior to S3

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10
Q

What is the junction at which the sigmoid becomes the rectum at S3 called?

A

The rectosigmoid junction

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11
Q

When does the rectum become the anal canal?

A

Anterior to the tip of the coccyx just prior to passing through the levator ani muscle

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12
Q

What is the orifice through which faeces pass?

A

The anus

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13
Q

Where does the rectum ampulla lie in relation to the levator ani?

A

Immediately superior to the levator ani

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14
Q

What does the walls of the rectum allow?

A

Allow the walls to relax to accommodate faecal material

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15
Q

How many folds does the rectal ampulla have?

A

3

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16
Q

What does the peritoneum cover?

A

The superior rectum

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17
Q

Where do the rectouterine/rectovesical pouch lie in relation to the rectum?

A

Anterior to the superior rectum

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18
Q

Where does the prostate gland lie in a male?

A

Anterior to the inferior rectum

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19
Q

Where does the vagina and cervix lie in relation to the rectum in a female?

A

Anterior to the inferior/middle recutm

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20
Q

What does the levator and muscle form?

A

Forms most of the pelvic diaphragm - together with fascial coverings

Forms most of the floor of the pelvic
Forms most of the roof of the perineum
Skeletal muscle

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21
Q

What type of muscle is the levator ani muscle?

A

Skeletal muscle

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22
Q

What 3 muscle make up the levator ani muscle?

A

iliococcygeus
pubococcygeus
puborectalis

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23
Q

What does the levator ani muscle provide support for?

A

The pelvic organs - tonically contracted most of the time

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24
Q

When else does the levator ani muscle contract?

A

Reflexively contracts further during increase in intra-abdominal pressure e.g. coughing, sneezing

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25
Q

What needs to be relaxed in order to allow defecation?

A

The levator ani muscle

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26
Q

What is the levator ani muscle supplied by?

A

The nerve to the levator ani - a branch of the sacral plus and pudendal (S2,3,4)

27
Q

What is the puborectalis?

A

Part of the levator ani muscle

28
Q

What is the puborectal muscle important for?

A

Maintaining faecal continence

Contraction of this muscle decrease the anorectal angle - acting like a sphincter

29
Q

What type of muscle if the puborectal muscle?

A

Skeletal

30
Q

What will contra ion of the muscle help to maintain?

A

When the rectal ampulla is relaxed & filled with faeces, voluntary contraction of this muscle will help to maintain continence

31
Q

What 2 anal sphincters are there?

A

Enteral

External

32
Q

Describe the shape of the external anal sphincter?

A

Long tube
Quite high
Forms a canal

Has 3 parts, deep, superficial and subcutaneous areas

33
Q

Describe the internal anal sphincter?

A

smooth muscle

superior two thirds of anal canal (the top bit)

contraction is stimulated by sympathetic nerves (i.e. sphincter is closed)

contraction is inhibited by parasympathetic nerves

contracted all the time, relaxes reflexively in response to distension (filling) of the rectal ampulla

34
Q

Describe the external anal sphincter?

A

skeletal muscle

inferior two thirds of anal canal (superior part of the sphincter is continuous with the puborectalis muscle)

contraction is stimulated by the pudendal nerve

voluntarily contracted (along with puborectalis muscle) in response to rectal ampulla distension and internal sphincter relaxation

35
Q

Describe structures in the pelvis?

A

Body cavity

sympathetic, parasympathetic and visceral afferent

36
Q

Describe structures in the perineum?

A

Body wall

somatic motor and somatic sensory

37
Q

What are the sympathetic supply to the rectum/anal canal?

A

T12-L2: travel to inferior mesenteric ganglia, synapse, then travel via periarterial plexuses around branches of IMA
- contraction of
internal anal sphincter
- inhibit peristalsis

T12-L2 - spinal cord level not vertebral level

38
Q

What are the 2 important spinal cord levels to remember in terms of the rectum and anal cancel?

A

T12-L2

S2-S4

39
Q

Describe the somatic motor supply to the rectum/anal canal?

A

motor from pudendal nerve (S2-S4) and nerve to levator ani (S3,S4):
- contraction of external anal sphincter and puborectalis

40
Q

Describe the visceral afferents supply to the rectum/anal canal?

A

back to S2-S4: run with parasympathetics

- sense stretch, ischaemia etc.

41
Q

Describe the parasympathetic fibre supply to the rectum/anal canal?

A

from S2-S4: via pelvic splanchnic nerves, synapse in walls of rectum

- inhibit internal anal sphincter
- stimulate peristalsis
42
Q

What does S2,3, and 4 do?

A

S2,3,4 keeps your guts off the floor

43
Q

What is the pudendal nerve a branch of?

A

A branch of the sacral plexus

S2,3,4 anterior rami

44
Q

What does the pudendal nerve supply?

A

The external anal sphincter

45
Q

Where does the pudendal nerve exit the pelvis?

A

The great sciatic foramen

46
Q

Where does the pudendal nerve enter the perineum?

A

Via the messer sciatic foramen

47
Q

When can the pedundal nerve or sphincter be damaged?

A

During labour

The branches of the pudendal nerve could be stretching

fibres within the puborectalis or external anal sphincter muscle could be torn - results in weakened muscle (could lead to faecal incontinence)

48
Q

Where might the tear of the perineum occur during labour?

A

tear of the perineum extending posteriorly to involve the external anal sphincter

49
Q

Describe the pectinate line?

A

Marks the junction between the part of the embryo which formed the GI tract (endoderm) and the part that formed the skin (ectoderm)

(junction between end and ectoderm)

50
Q

What differs above and below the pectinate line?

A

The arterial supply
Venous drainage
Lymphatic drainage
Nerve supply

All differ above and below the pectinate line

Superior to line = visceral

Inferior to line = parietal

51
Q

Describe the supply above the pectinate line?

A

Nerve - autonomic (visceral)
Arterial - IMA
Venous - to portal venous system (IMV)
Lymphatic - IMA nodes (internal iliac nodes)

52
Q

Describe the supply below the pectinate line?

A

Nerve- somatic, pudendal
Arterial - from internal iliac artery
Venous - to systemic venous system (internal iliac)
Lymphatic - superficial inguinal nodes

53
Q

Where do lymph vessels lie in the pelvis?

A

Alongside the arteries

54
Q

Describe the main groups of lymph nodes draining the pelvic organs?

A

internal iliac (draining inferior pelvic structures)

external iliac (draining lower limb, and more superior pelvic structures)

common iliac (drain the lymph from the external and internal iliac nodes)

lymph draining through the common iliac nodes then drains to the lumbar nodes

55
Q

Describe the blood supply to the rectum and anal cancel?

A

IMA - supplies hindgut organs - hindgut extends to the proximal half of the anal cancel (the pectinate line)

The remainder of the GI tract is supplied by the internal iliac artery

(there is a degree of anastomoses)

56
Q

Describe the venous drainage of the rectum and anal canal?

A

Enteral iliac vein drains below the pectinate line - systemic venous system

IMV drains the hindgut organs - above pectinate line - portal venus system

57
Q

When do recatal varies occur?

A

Form in relation to portal hypertension

dilation of collateral veins between portal and systemic venous systems

58
Q

What are haemorrhoids?

A

haemorrhoids are prolapses of the rectal venous plexuses

when there is a weakness in the muscle wall and increase in the pressure, straining, constipation etc

59
Q

Which out of internal and external haemorrhoids are more painful and why?

A

External - it is somatic so hurts

internal - visceral doesnt hut so much

60
Q

What is the Ischioanal Fossae?

A

ischioanal fossae (right and left) lie on each side of the anal canal.

filled with fat and loose connective tissue (allows distentions of the GI tract)

the two fossae communicate with each other posteriorly

61
Q

What in an infection within the ischioanal fossa called?

A

an infection within the ischioanal fossa is called an sischioanal abscess

infection can run round both sides - abscess get larger and then it may become obvious to see

62
Q

When might these infections occur? (Ichioanal fossa)

A

Anal fissures etc

63
Q

What does proctoscopy look at?

A

The interior of the recutm

LC Gastroenterology Week 4 (9 decks)

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