Week 4 Development Part 2 Flashcards

1
Q

What is physiological herniation and when does it occur

A

During 6th week
As liver growing rapidly alongside midgut it pushes midgut loop into umbilical cord- covered by amnion
- physiological as normal development process that is resolved

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2
Q

How does the midgut rotate and what is happening at each stage?

A

3 90degree turns anti-clockwise
First turn leaves cranial on R and caudal on L
- cranial limb elongates much more- s.intestine
Second turn leaves cranial at bottom
- ceacal bud forms
last turn moves cranial to L first and then caudal to R- transverse colon ends up in front of duodenum
- ceacal bud continues to drop

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3
Q

What does the cranial and caudal limbs of the midgut loop develop into?

A

Cranial- s.intestines- distal duodenum, jejunum, ilium

Caudal- distal ilium, caecum, appendix, ascending colon, proximal 2/3 transverse colon

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4
Q

Congenital abnormalities- What types of malrotation can occur and what does this result in?

A

Incomplete rotation- only one 90degree turn- L sided colon
Reversed rotation- One 90degree clockwise turn- transverse colon passes posterior to duodenum

Results in:
Volvulus- twisted intestinal loop
Strangulation of bowel
Ischaemia- due to abnormal distribution of viscera

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5
Q

Congenital abnormalities- what abnormalities can arise as a result of remnants of the yolk stalk?

A

Vitalline duct can persist (patient uracus) resulting in;
Vitalline cyst- remained fluid filled and duct forms fibrous strands
Vitalline fistula- leakage of intestinal content into umbilicus
Meckels diverticulum- ileal diverticulum
- 2% of population, usually seen in under 2yrs, 2:1 male to female
- ilium can contain ectopic gastric and pancreatic tissue- not designed for proteolytic enzymes in it

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6
Q

What is Recanalisation and why does it occur?

A

Primitive gut tube is a simple tube- during development growth in some gut structures can become so rapid that the lumen is partly or completely obliterated
- oesophagus, bile duct, small intestine
Recanalisation occurs to restore the lumen

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7
Q

Congenital defect- what happens if Recanalisation is not completed and where does this most commonly occur?

A

if uwholly or partly unsuccessful =
atresia - total failure- no lumen
stenosis- partial failure- narrowed lumen
- most occurs in duodenum- upper part due to recanalisation failure
- lower part due to vascular accident- volvulus, malroatation or body wall defect

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8
Q

congenital abnormalities- what is pyloric stenosis, why does it occur?

A

hypertrophy of the circular muscle in the region of the pyloric sphincter
not a recanalisation failure
- common abnormality of the stomach in infants- narrowing of the stomach exit= projectile vomiting

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9
Q

What does the midgut give rise to?

A

Small intestine including most of duodenum, caecum and appendix, ascending colon, proximal 2/3 of transverse colon

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10
Q

congenital abnormalities (anterior abdo wall defects)- what is gsatroschisis and omphalocoele?

A

gastroschisis- intestinal loop outside body wall- failure of closure of abdominal wall during folding of embryo- leaves gut tubes outside
- picked up at 20week scan, isolated defect- prognosis good if bowel not damaged

omphalocoele- examphalos- persistence of physiological herniation- differs from umbilical hernias as they have covering of skin and tissue whereas this is covered only by amnion
- can be associated with other conditions

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11
Q

When the midgut elongates what is its axis, what duct connects it to the yolk sac

A

SMA

Vitelline duct

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11
Q

what does the hindgut give rise to?

A

distal 1,3 duodenum, descending colon, rectum, superior part of anal canal, epithelium of urinary bladder

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12
Q

what line is the anal canal divided by and what does this separate?

A

pectinate line separates histologically distinct superior and inferior parts
- different arterial, venous, nervous and lymphatic supply - affects pain

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13
Q

Describe the partitioning of the cloaca and the development of the anal canal

A

anteroposterior devision
- wedge of mesoderm grows down into cloaca dividing it into urogenital sinus anteriorly and anorectal canal posteriorly - end of 7th week

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14
Q

Describe what occurs after cloacal partitioning and what tissues make up each part?

A

Cloacal membrane is in a pit and contains endo and ectoderm layer
Perineal body formed where partition meets cloacal membrane which is in the pit
Ectoderm curves up inside the first part of anal canal

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15
Q

By what is the anal canal separated and describe each section- artery, nerve, lymph supply, epithelia?

A

By pectinate line
Above line:
- IMA- artery of hindgut
- S2,3,4 pelvic parasympathetics- splanchnic nerves
- columnar epithelia- derived from endoderm
- lymph drainage- internal iliac nodes

Below line:

  • pudental artery
  • S2,3,4 pudental nerve- somatic nerve
  • stratified epithelia- from ectoderm
  • lymph drainage- superficial inguinal nodes
16
Q

What are the two sections of the anal canal sensitive to?

A

Above line- only sensation possible is stretch

Below line- temp, touch and pain sensitive- somatic innervation

17
Q

Discuss the innervation and pain sensation to the peritoneum,

A

Visceral peritoneum- pain poorly localised- forgut=epigastrium, midgut=periumbilical, hindgut=suprapubic
- only sense stretch
Parietal peritoneum- has somatic innervation also so pain much more localised

18
Q

Congenital abnormalities- discuss the hindgut abnormalities that may occur?

A

Imperforate anus- failure of anal membrane to rupture
Anal/ anorectal agenesis
Hindgut fistula

19
Q

What structures are retained by mesentery and which have fused mesenteries?

A

Retained by- things could hold in dissection
jejunum, ilium, appendix, transverse and sigmoid colon

Fused mesenteries- duodenum, ascending and descending colon, rectum

20
Q

What does the dorsal and ventral mesentery become?

A

Dorsal- greater omentum
- gastrolienal ligament- stomach to spleen
- lienorenal ligament- spleen to kidney
- mesocolon, mesentery proper- Jedinal and Ileal loops
Ventral- lesser omentum- foregut to liver
- falciparum ligament- liver to ventral body wall

21
Q

State the blood supply and innervation of the midgut and hindgut

A
Midgut
Blood supply- SMA and SMV
Innervation- para s- vagus
                   - symp- superior mesenteric ganglion and plexus
Hindgut
Blood supply- IMA and IMV
Innervation- para s- pelvic- S2,3,4,
                   - symp- inferior mesenteric ganglion and plexus