A system of organs within multicellular animals that has the purpose to take in food, digest it, extract energy and nutrients, and expel the remaining waste
-The hollow tube stretches from mouth to anus and includes the liver, gallbladder and pancreas. Initially the GI tract is a closed system
-The breakdown and movement of food products is completed through chewing, enzyme function, and peristalsis within the gut
-In an adult, the system is usually around 30 feet in length
Embryologic Development
of the Digestive System
Weeks 6-8
During this time, there is a separation between the intestinal and genitourinary tracts and the formation of the anal opening as well
The distal end of the gut tube will empty into the cavity known as the cloaca. The primitive
genitourinary tract also empties here.
– during weeks 6-7 these two will be separated by the urorectal septum
– the dorsal portion will become the rectum and anal canal
During week 8 the membrance covering the anal opening ruptures to establish a full patent tube that travels from the oral cavity to the anus
Fetal Development
Weeks 9-term
Embryological Development Weeks 4-8
1. Foregut
2. Hindgut
3. Midgut
4. Central nervous system
5. Tracheobronchial diverticulum
6. Heart
7. Liver bud
8. Buccopharyngeal membrane
9. Vitelline duct
10. Allantois
11. Cloacal membrane
Implications for the APRN
Midgut
Foregut
Errors in development of the midgut can cause:
omphalocele
- failure of the intestine to return to the abdomen
- also a failure in abdominal musculature development
- occurs in one of 6,600 births
umbilical hernia
- gut returns to abdomen, but later herniates through the umbilicus
gastroschisis
- linear defect of the abdominal wall that doesn’t involve the umbilicus
- herniation of the bowel occurs prior to the normal migration into the umbilicus
Meckel’s diverticulum
- a pouch of tissue can form along the intestine wall
The foregut gives rise to the
- pharynx & lower respiratory system
- esophagus, stomach, & proximal duodenum
- liver, biliary tree & pancreas
Errors of development can cause:
- various forms of esophageal atresias and TEF disorders – probable cause of malformation is an unequal division of the foregut into separate respiratory and digestive tracts
- jejunal atresia
- congenital hypertrophic pyloric stenosis
Week 4
Characteristics
• Rapid body growth
• Differentiation of tissues, organs, and systems
• Relative slowdown in head growth compared to remainder of body
• Periods of normal continuous growth alternate with prolonged intervals of absent growth
The primitive gut forms during the 4th week of gestation
- A flat embryonic disc folds in median and horizontal planes to form a tubular structure
This folding incorporates part of the yolk sac into the embryo
•Folding of the lateral sides forms the MIDGUT
•Folding of the cranial and caudal ends forms the FOREGUT and HINDGUT
•There is interdependent development of the hindgut (the intestinal canal) and the urogenital system
Hindgut
- The hindgut gives rise to the distal transverse colon, descending colon, sigmoid, rectum and proximal anal canal
- The caudal portion of the hindgut forms the cloaca – the cloacal membrane separates the hindgut from the external environment
- Errors of development of the hindgut can cause Hirschsprung disease – which develops from failure of the migration of the neural crest cells to the colonic wall usually during the 5th – 7th week of gestation
Weeks 4-5
Digestive System
Midgut
The key events in the development of the GI tract occur between weeks 4-8 of gestation
Development is proximal to distal
Weeks 4-5 of Gestation
By the end of the 4th week, the proximal end of the ‘tube’ has established an open communication to the amniotic fluid in the area that will go on to become the oral cavity and pharynx
-Formation of the respiratory tract will begin during the 4th week and there is the development of a small ‘diverticulum’ next to the esophageal area of the gut tube
-Separation of the respiratory tract and the proximal gut occurs with the development of tissue folds that will form a tracheoesophageal septum
- Assessment
- Diagnosis
- Management & treatment
- Counseling ~ future risk & future care
- Resources for family & education
-The midgut gives rise to the distal duodenum, jejunum, ileum, appendix, ascending colon and proximal transverse colon
-Forms a U-shaped loop that herniates into the umbilical cord during the 6th week of development
-While in the umbilical cord, the midgut loop rotates a full 90 degrees and during the 10th week the midgut will return to the abdomen rotating another 180 degrees
- The development of the GI system is craniocaudal in direction
- Upper portions of the digestive tube begin specialization sooner than the lower
- The three germ layers include the ectoderm, the mesoderm and the endoderm
The endoderm, which is a germ layer that appears around the eighth day, forms the yolk sac and this is the basis for the digestive tract
The formation of the body ‘cylinder’ creates an internal and external environment
- Extraembryonic – outside the embryo, the yolk sac regresses and disappears with assimilation into the umbilical cord
- Intraembryonic – inside the embryo, the yolk sac will form the primitive gut
This will develop into the foregut, midgut, hindgut, liver and pancreas
- Substantial weight gain
- Better proportioned
Weeks 21-25
Fetal spleen erythropoiesis passes on to bone marrow to process--still retains its potential even in adult life
Week 12
Week 28
Weeks 30-34
Weeks 10-11
Weeks 35-38
Week 9
Weeks 13-16
Congenital omphalocele is persistence of the herniation of abdominal contents into the proximal part of the umbilical cord.
- Results from impaired mesodermal & ectodermal growth of abd wall.
- Covering of the hernia sac is a derivative of the amnion.
- Must be surgically repaired.
- Insulin secretion begins.
- Peritoneal cavity is connected with the extraembryonic coelom
- Intestines return to the abdomen from the umbilical cord--reduction of the midgut hernia.
- Small intestine returns first, passing posterior to the superior mesenteric artery and occupies central abdomen.
- Large intestine rotates another 180 degrees counterclockwise.
- Descending & sigmoid colon move to the right
Weeks 10-11
- Growth is rapid during weeks 14-16
- Bile entering the duodenum through the bile duct after the 13th week gives the meconium a dark green color.
- Some of small intestines in the proximal part of umbilical cord due to liver/kidney size.
- Liver is major site of erythropoiesis.
- Pancreatic acini begin to develop from cell clusters around the ends of parenchymal tubules & pancreatic islets develop from groups of cells that separate the tubules and lie between the acini.
Other defects during this stage of development:
Umbilical hernia forms when greater omentum and part of small intestine re-herniates into imperfectly closed umbilicus.
- Different from omphalocele with covering of subcutaneous tissue and skin & surgery usually unnecessary unless hernia persists to age of 3 to 5 years.
- Crown rump length has more than doubled.
- Erythropoiesis decreases in the liver, begins in the spleen.
- Bile formation by hepatic cells begins in the liver.
- Waste products are transferred to the maternal circulation by passing across the placental membrane.
- Alpha-fetoprotein (AFP) is synthesized in the fetal liver, umbilical vesicle, and gut--found in high concentration in fetal serum peaking @ 12 weeks.
- Anomalies of ventral abdominal wall show abnormally high concentrations of AFP in the amniotic fluid.
Weeks 17-18
- Stomach & duodenum rotation causes duodenum & pancreas to fall right posterior abdominal wall & lie retroperitoneal.
- Pancreatic head & ascending colon also become retroperitoneal.
- If pleuroperitoneal canal is still open, some intestine and other viscera may pass into the thorax pushing over & compressing the lungs and heart. Often stomach, spleen, and most of intestines herniate.
- Gastroschisis
- Malrotation
- Nonrotation
- Mobile cecum
- Internal hernia
- Malfixation
- Ileal diverticulum.
- Growth slows down during this period.
Assessment & Diagnosis
Resources
- International foundation for functional gastrointestinal disorder
- Cancerinstitute.com
- Crohn's & colitis foundation of America
- Aboutkidshealth.ca
- Womensmedicine.org
- Parents of galactosemia children, inc. (Galactosemia.org)
- Cystic fibrosis foundation (CFF.org)
- Matriculate at an accredited University to learn excellent assessment & diagnostic skills
- Know what constitutes a surgical emergency
- Immediate repair or diagnosis: Volvulus or midgut rotation, CDH, Gastroschisis, Omphalocele, Imperforate anus w/o fistula, TEF/EA, Choanal atresia, Galactosemia & Cystic Fibrosis (both on NGS)
- Surgical repair soon after birth: Intestinal stenosis, atresia, or webs, CL/CLP
- Utilize resources for diagnosis:
- OMIM, experienced APRNs, neonatologist, radiologist, surgeon
Management & Treatment
Congenital Gastrointestinal Disorders
- Surgical vs medical management
- EBP
- Follow up future care for family
- Genetic counseling for recurrence risk
- Embryonic of the gut is complex. Due to this complexity it is unsurprising that abnormalities of development occur.
- Abnormalities may be complex & multiple with more than one part of gut affected or other system involvement.
- Wide variety of syndromes & abnormalities are associated with gastrointestinal malformations.
- Focus on structural defects rather than function involving enzyme deficiencies.
Volvulus or Midgut Rotation
- AD-OMIM #193250
- Boxy head, frontal bossing
- Eyes: telecanthus intercanthal distance > width of eye.
- Long palpebral fissures.
- Surgical emergency
VACTERL
Meckel's Diverticulum
- Mnemonic describes a condition with multiple abnormalities, some within some outside the gut.
- Must have 3 of 6 defects to be diagnosed.
- X linked mutation or deletion of ZIC3 gene on Xq26 OMIM #314390
- Fanconi anemia group B, which is another genetic cause of X linked VACTERL-H.
Esophageal Atresia
- AD- OMIM #155140
- Bulge in small intestine @ birth.
- Remnant of yolk stalk.
- Higher in males
- Found in distal lumen 60-100 cm from ileocecal valve.
- Can cause intussusception or present like acute appendicitis.
- Problematic can be surgically resected.
Hirshprung's Disease
CHARGE Syndrome
Congenital Diaphragmatic Hernia
- OMIM #189960-NO known molecular etiology
- CHARGE syndrome may play a role in the molecular etiology.
- Occurs 1 in 3,500 and 1 in 5,000. If a sibling has had the condition the incidence is 1 in 50.
- 6X more common in twins, Trisomy 13, 18, 21.
- May have urogenital, CV, Colorectal--genetic component unclear.
- 85% have distal TE fistula, 10% have no fistula.
Cleft Lip & Palate
- AD- 10q11.21. OMIM #142623.
- Caused by gene-mutation responsible for disruption of the endothelin gene- affects nerve trunk to the gut.
- Begins in the rectum and advances proximally in varying degrees.
- Associated with other conditions-Downs Syndrome.
- Colostomy may be performed/aganglionic segment must be removed.
- Absence of intramural ganglionic cells
- AD, 6p24.3
- OMIM #119530
- 30% of such cases are part of a syndrome with other abnormalities.
- Most common deformity with world wide incidence 1 in 700.
- Incidence of cleft palate alone is 1 in 2,000.
- Anticonvulsant, benzodiazapine, & steroid use in pregnancy increase risk.
- Inhibits maternal bonding/difficulty with feeding and speech.
- Surgical tx=good outcome.
- Must have 4 of 7 features including 1 major feature.
- AD chromosome= 7q21.11, 8q12.1-q12.2 OMIM #214800
C=Coloboma of the eye, 80% affected possible nystagmus. Poss retinal detachment occurs.
H=Heart anomalies-VSD-ASD, Tet of Fallot, PDA are common.
A= Posterior Choanal atresia. 50% occurence
VACTERL
- X-Linked, unbalanced or deletion of 15q26.1.
- OMIM #142340.
- Most are idiopathic, 15% chromosome implication.
- Stomach/intestines impinge on the structures in the chest-compromise to pulmonary and CV function.
- Early surgical repair is required.
Intestinal Stenosis, Atresia, or Webs
Esophageal Atresia
V=Vertebral defects- single/multiple hemi-vertebrae, scoliosis, rib deformities.
A=Anorectal malformations including imperforate anus/Cloacal deformities.
C=Cardiovascular defects=VSD, tet of Fallot, ASD, PDA, Coarct AO, (R) side Ao arch, single Umbilical artery.
TE=Tracheoesophageal defect or esophageal atresia w/wo fistula (TOF).
R=Renal anomalies seen with Potter syndrome bilateral renal agenesis, Polycystic kidney, Urethral/ureteral malformations, horseshoe kidney.
L=Limb deformities-Radial dysplasia, absent radius,radial deformities, syndactyl, polydactyl, lower limb deformities.
Kartagener's syndrome
Exomphalos & Gastroschisis
Hypertrophic Pyloric Stenosis
Genetic Diseases of the Digestive System
- Remainder is a mixture of proximal fistula.
- Feeding can lead to aspiration and early surgical repair is essential for survival
- AR-2p16,2p21. OMIM #243150.
- Can occur any location esophagus, duodenum most common(1 in 10,000) 30% have Downs syndrome. 30% have CV defects.
- Antenatal US dx is often possible.
- Surgical intervention is required
- Combined esophageal and duodenal atresia is more complicated
Pentalogy of Cantrell
CHARGE syndrome
Imperforate Anus
- AR-9p13.3
- OMIM #604366.
- Associated with Situs Inversus & gastro-intestinal malformations.
- Severe gastro-esophageal reflux with uncontrolled regurgitation.
- May be seen with large hiatal hernia.
Mouth breathing cannot be established. Life threatening.
Polyhydramnious in pregnancy.
R=Retardation-mental/growth. 70% IUGR, Developmental delay 70% with possible micorcephaly and cerebral atrophy.
G=Genital hypoplasia 70% boys & 30%girls. Micropenis, Cryptorchidism, microlabia.
E= Ear abnormalities and deafness 90%, external ear is abnormal, often small and low set. Deafness is often a mixed type.
- Chromosomal duplication syndrome 1p31.3.
- AD, OMIM #164750.
- Feature of Beckwith-Wiedemann syndrome OMIM #130650 & Shprintzen-Goldberg #182210.
- Occur in about 1 birth in 3000.
- Deficiency of the abdominal wall and contents herniate into space.
- Prune belly syndrome: 97% boys, deficiency in abdominal wall. Cryptorchidism, hydornephrosis, possibly pulmonary hypoplasia, usually gut intact.
- X-linked Dominant, Xq25-q26.1
- OMIM #313850.
- Rare syndrome-defects of the diaphragm, abdominal wall heart and sternum.
- Inclusive of: omphalocele, diaphragmatic hernia (anterior, sternal cleft, and ectopia cordis.
- AR-vs-Multifactoral. OMIM #207500.
- Abnormalities in rectum or anus
- minor=1 in 500 births,
- major abnormalities=1 in 5,000 births.
- Abnormalities with small intestine, esophagus, GU system, CV, Sacral area.
- Preoperative resuscitation required, nature of surgery is dependent on the location of the lesion and other possible complications.
- AD- 12q-OMIM #179010.
- Not present at birth develops later.
- Common boys/white/1st born/ 2 to 4 per 1000 incidence.
- Failure of gastric emptying/feeding followed by projectile vomiting/2-8 weeks after birth.
- Electrolyte imbalance-hypochloremic, dehydration, metabolic alkalosis.
- DX: Ultrasound
Crohn's Disease
Colon Cancer
- Classified IBD-inflammation, ulceration sm/lg intestine
- Class of IBD Ulcerative Colitis/Crohn’s Disease.
- UC-affects inner lining colon rectum.
- CD-extends into deeper layers of intest wall.
- 20% cases of CD runs in families.
- Locus on Chromosome 3, 7, 12, 16 ARD
- Inflammatory response B-lymphocytes,CD11,IL44 receptor.
- Leukocyte& microbacterial cell adhesion.
- OMIM # 266600
- >93 k cases in 2000, 47K deaths.
- All kinds of cancer occur with cell division.
- Regulated cell division-get out of control.
- Environmental- smoking, diet, exercise.
- Genetic-genes MSH2 and MSH6 on Chromosome 2. MLH1 on Chomosome3.
- Mutation in MSH2, MSH6, MLH1 protein, not repaired-lead to damaged DNA = Colon Cancer.
- Specific-3p22.2-OMIM #609310
Diabetes Type I
Pancreatic Cancer
- Chronic metabolic disorder/affects insulin production.
- Risk for: CV/Blindness/Renal disease/Neurological.
- Type 1 or Juvenile=most severe form of disease.
- Known as a complex trait, most likely Chromosome 6 and 7 with 10 different loci. On 6p21.3/ARD
- Class under autoimmune disease of Chromosome 6.
- Requires insulin administration.
- OMIM #222100
- Production insulin/glucagon/digestion of protein.
- 1997 27k new cases= 28K deaths.
- Possible tumor suppressor gene lost with disease.
- Chromosome- 12p12.1,17p13.1, 15p13.3
- OMIM #260350 AD pattern
- Survival 5 years < 5%
Glucose Galactose Malabsorption
Cystic Fibrosis
Zellweger Syndrome
Wilson's Disease
- Rare metabolic disorder.
- Severe diarrhea/dehydration as early as first day of life.
- Diet removal: lactose, sucrose, glucose, & Galactose.
- 50% is a result of familial intermarriage.
- 10% general pop has some form of glucose intol. Possible mild form of disease.
- ARD 22q12.3
- Unable to transport these sugars out of intestine/left untransported they draw h20 out of body=diarrhea
- CF defective gene disorder most common fatal genetic disorder in the U.S.
- Produces thick sticky mucus clogs the lungs=infection, pancreas=affects digestive enzymes=malnutrition/digestion.
- Defective transporter of Chloride/ secondarily Sodium by epi cells= Na increased in bodily secretions.
- Chromosome 7q31.2/ ARD
- OMIM #219700
- Slight success in Gene therapy/more study research
- Rare disorder chromosome 7q21.2 ARD/OMIM #214100
- Neurological - Hepatic dysfunction.
- Elevated serum levels of Fe-Cu.
- Peroxisomes function inhibited, the enzymes they carry are responsible for metabolic reactions.
- Specific enzymes are responsible for lipid metabolism and metabolic oxidations.
Death at a early age.
- Cardiac malformations
- small mandible
- flexion of fingers
- agenesis of corpus callosum
- Rare ARD 13q14.3/OMIM #277900.
- Disorder of copper transport accumulation/toxicity in brain an liver.
- Kayser-Fleisher ring=Cu-colored ring periphery cornea
- Related to Menkes disease=Cu transport disease.
- Skin tone will be a dark Cu or green tint.
- Urine color is a patina colored green.
- Affects basal ganglia brain/dopamine production alteration. Parkinson like movements
The Alimentary System
by Angie Lawson, Laura Sullivan, &
Eugene Snyder