GI HARC 2 Flashcards
Primitive gut tube has __ parts which develop into GI tract & organs
3
What are the 3 parts of which delove into GI tract and organs
Foregut
Midgut
Hindgut
• Foregut develops into:
- Oesophagus to 2nd part of duodenum
- Accessory organs – liver, gallbladder, pancreas
• Midgut develops into:
• 2 nd part duodenum to ¾ transverse colo
• Hindgut develops into:
• ¾ transverse colon to superior rectum
Name the colours
Orange: Foregut
Purple: Midgut
Green: Hindgut
What does the Lower GI tract consist of?
• Jejunum to anus
Function of the small intestine
- Mechanical and chemical digestion
- Absorption of 90% of nutrients
Function of large intestine
- Reabsorption of water & electrolytes
- Convert indigestible food into faeces – store & expel
Histology of Small Intestine
What are the key microanatomical features of mucosa:
- Circular folds
- Villi & Microvilli
- Intestinal glands
Properties of circular folds
• Increase surface area and slow chyme flow
Properties of Villi and Microvilli
- Maximise surface area of intestinal wall
- Most abundant in proximal 2/3 of S.I. – most absorption
Properties of Intestinal glands
- Enterocytes, Goblet cells, Paneth cells, etc. and multipotent stem cells to replace eroded epithelia
- Produce intestinal juices rich in digestive enzymes and hormones
Small Intestine
Small intestine
Histology of Small Intestine
Micrograph of circular folds
Micrograph of villi
Electron micrograph of microvilli
Histology of Large Intestine
What are the key microanatomical features:
- No circular folds or villi (except anal canal)
- Intestinal glands (many more, deeper crypts)
- Enterocytes – absorptive cells with a microvilli border
- Goblet cells – secrete mucous to facilitate faecal movement
Large Intestine
Histology of Large Intestine
What is this?
Section through wall of colon
Name a congential anomalies
Hirschsprung’s Disease.
Meckel’s diverticulum
Omphalocele- Abdominal Wall Defects
Gastroschisis-Abdominal Wall Defects
What is Hirschsprung’s Disease?
This disorder is characterized by the absence of particular nerve cells (ganglions) in a segment of the bowel in an infant. The absence of ganglion cells causes the muscles in the bowels to lose their ability to move stool through the intestine (peristalsis).
• Enteric nervous system has ______ and ________ plexuses
myenteric
submucosal
What does aganglionosis mean
The state of being without ganglia; for example, absence of ganglion cells from the myenteric plexus as a characteristic of congenital megacolon.
What does Hirschsprung’s Disease involve?
• HD involves agangliosis of both plexuses in distal colon & rectum
SO the absent/damage to the ganglia here means that the nerves are not funcitonal = muscle atrophy/wastage
- Functional obstruction develops from spasms in denervated colon
- Becomes apparent as severe constipation within first 2 months
How to identify Hirschsprung’s Disease?
• Biopsy to identify ‘transition zone’ between absent and present ganglionic cells. Surgery to remove affected segment
What is Meckel’s diverticulum?
A Meckel’s diverticulum, a true congenital diverticulum, is a slight bulge in the small intestine present at birth and a vestigial remnant of the omphalomesenteric duct (also called the vitelline duct or yolk stalk).
the vitellointestinal duct should seperate over time during development but sometimes the connection does perisist =.
What is vitellointestinal duct
(embryonic connection between yolk sac and midgut lumen)
In Meckel’s diverticulum can cause gastric mucosa which may cause bleeding from ‘gastric’ ulceration in its mucous membrane
What can this be mistaken for?
appendicitis
Meckles’s Diverticulum usually comes in Rule of 2s?
What does this mean?
Rule of 2s:
- 2% of population
- Presents in first 2 years
- 2 inches in length
- Approx. 2ft from ileocaecal valve
What is Omphalocele?
• Large herniation of intestines (and sometimes liver & other organs) out of umbilicus at birth (so more than usually comes out of umbilicus)
This leads to:
- Failure to return to abdomen after natural protrusion during development
- May be related to embryonic folding defect
IMPORTANT: herniation is covered by the peritoneal membrane and amnion
What is Gastroshcisis?
- Herniation of bowel loops (sometimes also stomach & liver) through para-umbilical defect in abdominal wall
- No surrounding membrane
- Cause unknown but genetic & environmental factors linked
- Possibly by compromise in vasculature to abdominal wall
surgery to repair
IMPORTANT: not covered by membrane
Out of Gastroschisis and Omphalocele which one is covered by y peritoneal membrane and amnion
Omphalocele
What does Antenatal US show on Gastroschisis and Omphalocele?
Omphalocele- Antenatal US shows herniated loops (but not free-flowing because contained within peritoneum)
Gastroschisis- Antenatal US can show herniation to right of umbilicus, freefloating and small fetal abdominal circumference
What imaging do we use to asses the GI tract?
X-ray
Ultrasound
Fluoroscopy
Cross section imaging (computed tomography) CT
MR- MAgnetic resonance imaging (MR)
How do we use X ray in the GI tract?
Predominanty to look for perforation or bowel perfiration and to look at bowel patterns
- abnormal/free gas
- Bowel gas pattern (obstruction)
- normal bowel gas,abnormal location
- calcificaiton
- tubes/lines/Fbs
What do the two starts indicate?
Subdiaphragmatic free gas
What are these X-rays showing?
Abdominal free gas
What is this Xray showing?
Gas in the bowel wall- pneumotosis
What is this Xray showing
Bowel gas pattern
What does this Xray show?
Normal bowel gas, abnormal place
so this is a diaphragmatic hernia
What can you see in this X-Ray
Calcification
Why would you do an ultrasound in the GI tract?
- Solid organs
- Fluid filled structures
- Free fluid/ collections
- Masses Abnormal bowel
What does this ultrasounds show
What does this ultrasound show in children?
What does this ultrasound show?
Crohn’s terminal ileitis
What is a fluoroscopy?
Real time live xray where you use a dye that shows up on xray to fill a hallow structure.
Why would you use a fluroscopy for GI
- Bowel lumen
- Transit/peristalsis
- Abnormal communications
What does this fluroscopy show?
Malrotation
What do these show
Hirschprung’s disease
Why do we do CT scans for GI
Free gas
Free fluid/ collections
Acute haemorrhage
Soft tissues
Vasculature
Calcifications
What is wrong is this CT?
Free gas
Why would you do MR in GI
Soft tissues
Free fluid/collections
Vasculature
Why do we need to know the circulation of peritoneal fluid, the spaces and how they communicate
Because it helps us understand the spread of tumour and infection
also can localise pathology by identifying the space continuing abnormal fluid/gas/tissue
also can predict disease behaviour
How many sacs do the peritoneum have?
2 greater and lesser
Falciform ligament attaches liver to _________
abdominal wall
Right Subhepatic space is bounded superiorly by the ____ _____ ___ of the l____. Continues with right ______ space and right ___ space as well
bounded supreriorly by the inferior right lobe of the liver. Continues with right subphrenic space and right colic space as well
Left Subhepatic space located between left lobe of _____ anteriorly and the ______ posteriorly.
located between left lobe of liver anteriorly and the stomach posteriorly.
The top and bottom portion so the peritoneal cavity communicates through the ______ _______
The top and bottom portion so the peritoneal cavity communicates through the paracolic spaces.
Between bladder and uterus we have______
vesicouterine pouch
Between Rectum and uterus-
rectouterine pouch
Where is the lesser sac located?
lies anterior to pancreas and posterior to the stomach.
