deck_1667685 Flashcards
What does the midgut give rise to?
o Small intestine, including most of the duodenum (post bile duct entry)o Caecum and appendixo Ascending colono Proximal 2/3rds of the transverse colon
How is the primary intestinal loop formed?
As a result of the rapid elongation of the midgut and the large size of the developing liver
Describe the midgut loop - What are its two parts, what is its axis and where does it connect?
- Cranial and caudal limbs- Superior mesenteric artery at ais- Connected to vitelline duct
What does the cranial limb of the midgut loop become?
Distal duodenumJejunumProximal ileum
What does the caudal limb become?
Distal IleumCecumAppendix Ascending ColonProximal 2/3 transverse colon
What process occurs to make room for developing midgut?
Physiological herniation
What is physiological herniation?
Intestines herniate into the proximal umbilical cord
What is rotation of the midgut?
Midgut rotates in a counterclockwise direction until we get the shape of the normal Gi. 270* counterclockwise rotation
In what order do parts of the midgut return to the abdominal cavity?
Cranial limb return first, moving to left hand sideCecal bud returns last
What happens to the cecal bud once it has returned to the abdomen
Descends, moving caecum to right lower quadrant
Give two types of malrotation
Incomplete rotationReversed rotation
What does malrotation result in?
Gut hypermobility and volvulus
What is incomplete rotation?
Midgut makes only one 90* rotationResults in left sided colon
What is reversed rotation?
Midgut makes one 90* rotation clockwiseTransverse colon passes posterior to the duodenum
What is a volvulus?
A bowel obstruction where a loop of bowel abnormally twists in on itselfMore likely with hypermobile (malrotates) guts
What can volvulus lead to/
Strangulation and herniation
What does the hind gut give rise to?
o Distal 1/3 Transverse Colono Descending colono Rectumo Superior part of anal canalo Epithelium of the urinary bladder
What is the cloaca?
The end of the hind gut
What is the cloaca separated from the outside world by?
Cloacal membrane
What happens at 6 weeks to the cloaca?
Partioning by the urorectal septum
What does partioning by the urorectal septum create in the cloaca?
Urogenital sinusAnorectal sinus
What are the two parts of the anal canal derived from?
Superior derived from hindgutInferior from ectoderm
What is the line at which the two parts of the anal canal separate?
Pectinate line
What is the Blood SupplyInnervationEpitheliaLymph Drainageabove the pectinate line
Blood Supply - IMAInnervation - S2-S4 PSEpithelia - ColumnarLymph Drainage - Internal iliac nodes
What is the Blood SupplyInnervationEpitheliaLymph Drainagebelow the Pectinate line
Blood Supply - Pudendal AInnervation - S2-S4 Pudendal nerveEpithelia - Stratified squamous (non K)Lymph Drainage - Superficial inguinal nodes
What is the only sensation possible aboe pectinate line?
Stretch
What is the sensation possible below pectinate line and why?
Temperature, touch and pain due to somatic innervation from pudendal nerve
What is the white line?
A portion of ectodermal anal canal which separates Non-K Strat squamous from K Strat Squamous
What is meckel’s diverticulum?
Ileal diverticulum. Cul-de-sack as the result of failure of closure of vitelline duct
What is the rule of 2’s for meckel’s diverticulum? (6)
o 2% of the population affectedo 2 feet from the ileocecal valveo 2 inches longo Usually detected in under 2’s Can be asymptomatico 2:1 Male:Female- 2 types of tissue, gastric or pancreatic
What is a vitelline cyst?
Vitelline duct frorm fibrous strands at either end
What is a vitelline fistula?
Direct communication between the umbilicus and intestinal tract. This results in faecal matter coming out of the umbilicus.
What is atresia and stenosis of intestines?
Complete loss or narrowing of lumen
Give two reasons for lumen atresia
Unsuccesful recanalisationVascular accidents due to a loss of blood supply and dead gut
Where does most atresia occur?
Duodenum
Where is loss of blood supply causing atresia most common?
Duodenum, but not the most common cause >Jejunum = Ileum > Colon
What is most common cause of atresia in upper duodenum?
Failure of recanalisation
What is most common cause of atresia in lower duodenum?
Vascular accident (malrotation and volvulus)
What is pyloric stenosis?
Narrowing of pyloric sphincter resulting in projecile vomiting
Give two defects of abdominal wall
GastroschisisOmphalocoele
What is gastrochisis?
Failure of closure of abdominal wall during embryo folding leaving gut tube and its derivatives outside the body NO COVERING
What is omphaocoele?
Persisence of physiological herniation Umbilical cord covered by reflection of the amnion COVERING PRESENT
Give three hindgut abnormalities
Imperforate anus - Failure of anal membrane ruptureAnal agenesis - Failure of developmentHindgut fistula - Abnormal connection to bladder
What five structures retain their mesentery?
o Jejunumo Ileumo Appendixo Transverse colono Sigmoid colon
What four structures have fused mesenteries?
o Duodenumo Ascending colono Descending colono Rectum (no peritoneal covering in distal 1/3)
