Anatomy- Faecal Continence

Question 1

what does the control of the excretion of faeces require?

Answer 1

a holding area (the rectum) to store faeces until appropriate to defecate
normal visceral afferent nerve fibres to sense the ‘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

Question 2

what can affect the control of the excretion of faeces?

Answer 2

• neurological pathology eg dementia, stroke, MS, trauma
• medications
  natural age-related degeneration of nerve innervation of muscle
• consistency of stool

Question 3

where is the pelvic cavity?

Answer 3

within the bony pelvis
continuous with abdominal cavity above
lies between pelvic inlet and pelvic floor

Question 4

where is the rectum located?

Answer 4

within the pelvic cavity

Question 5

levator ani muscle

Answer 5

pelvic floor

Question 6

purpose of pelvic floor

Answer 6

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

Question 7

where does the sigmoid colon become the rectum?

Answer 7

anterior to S3

recto-sigmoid junction

Question 8

where does the rectum become the anal canal?

Answer 8

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

Question 9

where are the anal canal and the anus?

Answer 9

in the perineum

Question 10

where is the rectal ampulla?

Answer 10

immediately superior to the levator ani muscle

Question 11

what is the purpose of the rectal ampulla?

Answer 11

its walls can relax to accommodate faecal material

Question 12

where does the prostate gland lie?

Answer 12

anterior to the inferior rectum

Question 13

what covers the superior rectum?

Answer 13

peritoneum

Question 14

what does the levator ani muscle form?

Answer 14

most of pelvic diaphragm together with fascial coverings
most of floor of pelvis
most of roof of perineum

Question 15

what is the levator ani muscle made up of?

Answer 15

pubococcygeus
puborectalis
illiococcygeus
skeletal muscles

Question 16

what is the purpose of the levator ani muscle?

Answer 16

provides continual support for the pelvic organs- tonically contracted most of the time
reflexively contracts further during increase in intra-abdominal pressure eg coughing, sneezing
must relax to allow defecation to occur

Question 17

what nerve is the levator ani muscle supplied by?

Answer 17

‘nerve to levator ani’

a branch of the sacral plexus and pudendal (S2,3,4)

Question 18

what is the importance of the puborectalis?

Answer 18

contraction of this muscle decreases the anorectal angle, acting like a sphincter
when the rectal ampulla is relaxed and filled with faeces, voluntary contraction of this muscle will help to maintain continence

Question 19

what are the 2 anal sphincters?

Answer 19

1 internal sphincter (smooth muscle)

1 external sphincter (skeletal muscle)

Question 20

what stimulates the contraction of the internal anal sphincter?

Answer 20

sympathetic nerves (ie sphincter is closed)

Question 21

what inhibits contraction of the internal anal sphincter?

Answer 21

parasympathetic nerves

Question 22

what stimulates contraction of the external anal sphincter?

Answer 22

pudendal nerve

Question 23

what is the nerve supply of structures in the pelvis?

Answer 23

body cavity
sympathetic
parasympathetic
visceral afferents

Question 24

what is the nerve supply of structures in the perineum?

Answer 24

body wall

somatic motor and somatic sensory

Question 25

what is the role of sympathetic fibres from T12-L2?

Answer 25

contraction of internal anal sphincter | inhibit peristalsis

Question 26

what is the course of sympathetic fibres from T12-L2?

Answer 26

travel to inferior mesenteric ganglia- synapse- then travel via periarterial plexuses around branches of IMA

Question 27

what is the role of somatic motor from pudendal nerve (S2-S4) and nerve to levator ani (S3,S4) ?

Answer 27

contraction of external anal sphincter and puborectalis

Question 28

what is the role of visceral afferents back to S2-S4?

Answer 28

run with parasympathetics | sense stretch, ischaemia etc

Question 29

what is the role of parasympathetic fibres from S2-S4?

Answer 29

inhibit internal anal sphincter | stimulate peristalsis

Question 30

what is the course of parasympathetic fibres from S2-S4?

Answer 30

via pelvic splanchnic nerves, synapse in walls of the rectum

Question 31

describe the pudendal nerve

Answer 31

branch of sacral plexus S2, S3, S4 anterior rami supplies external anal sphincter

Question 32

how does the pudendal nerve exit the pelvis?

Answer 32

via greater sciatic foramen

Question 33

how does the pudendal nerve enter the perineum?

Answer 33

via lesser sciatic foramen and branches to supply structures of the perineum

Question 34

what can happen to the pudendal nerve during labour?

Answer 34

branches of the pudenal nerve could be stretched fibres within the puborectalis or external anal sphincter muscle could be torn results in weakened muscle and may lead to faceal incontinence

Question 35

what does the pectinate line mark?

Answer 35

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

Question 36

what differs above and below the pectinate line?

Answer 36

``` arterial supply venous drainage lymphatic drainage nerve supply superior to line = visceral inferior to line = parietal ```

Question 37

describe the supplies above the pectinate line

Answer 37

autonomic nerve supply arterial supply from inferior mesenteric artery venous drainage to hepatic portal system lymphatic drainage to inferior mesenteric nodes

Question 38

describe the supplies below the pectinate line

Answer 38

somatic and pudendal nerve supply arterial supply from internal iliac artery venous drainage to systemic venous system lymphatic drainage to superficial inguinal nodes

Question 39

describe the groups of lymph nodes draining the pelvic organs

Answer 39

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

Question 40

what supplies the blood to the hindgut organs (to the proximal half of the anal canal)?

Answer 40

inferior mesenteric artery

Question 41

what supplies blood to the remainder of the GI tract?

Answer 41

internal iliac artery (there is a degree of anastomoses)

Question 42

what drains blood from the hindgut organs above the pectinate line?

Answer 42

inferior mesenteric vein

Question 43

what drains blood below the pectinate line?

Answer 43

internal iliac vein to the systemic venous system

Question 44

what causes rectal varices to form?

Answer 44

portal hypertension

Question 45

what are rectal varices?

Answer 45

dilatation of collateral veins between portal and systemic venous systems

Question 46

what are haemorrhoids?

Answer 46

prolapses of the rectal venous plexuses

Question 47

what causes haemorrhoids?

Answer 47

raised pressure eg chronic constipation, straining, pregnancy

Question 48

where do the ischioanal fossa lie?

Answer 48

on each side of the anal canal

Question 49

what fills the ischioanal fossa?

Answer 49

fat and loose connective tissue

Question 50

what is an infection within the ischioanal fossa called?

Answer 50

an ischioanal abscess