Embryology Study Materials for Week 9 - Key Terms and Definitions

When does the embryonic disc undergo folding?

Week 4 gestation

Which layer of the trilaminar disc grows fastest?

Somatopleure

Which layer of the trilamminar disc grows slowest?

Splanchnopleure

What types of folding result from different growth rates of the somatopleure and splanchnopleure?

Lateral folding

Cranial-to-caudal folding

What gives the embryo the tube-within-a-tube body plan?

Lateral folding

What is formed by complete lateral folding?

Gut tube

Body cavity

Anterior body wall

What part of the embryonic disc does lateral folding not complete in?

Middle region

What prevents completed lateral folding in the middle region of the embryonic disc?

Secondary folk sac

What regions of the embryonic disc is lateral folding complete in?

Caudal and cranial regions

What are the AKAs of the Vitelline duct?

Omphaloenteric duct

vitellointestinal duct

Omphalomesenteric duct

yolk stalk

What happens to the secondary yolk sac during lateral folding?

It gets severely pinched

What does the pinching of the yolk sac create a passageway between?

Newly created midgut of the gut tube

The secondary yolk sac

What is the passageway between the secondary yolk sac and midgut called?

Vitelline duct

When does the vitelline duct normally degenerate away?

Between the second and third month gestation

What % of live births does the vitelline duct not degenerate away in?

2%

What is the term for a vitelline duct that does not degenerate away?

Persistent vitelline duct

What is the #1 congenital anomaly of the GI tract?

Persistent vitelline duct

What is the one major sequela of persistent vitelline duct?

Small bowel obstruction

What is the most common presentation of a persistent vitelline duct?

Merkel's diverticulum (2%)

What type of diverticulum is a Merkel's diverticulum?

True diverticulum

What part of the intestine is a Merkel's diverticulum a pouching of?

Ileum

Why is Merkel's diverticulum considered a true diverticulum?

Contains the usual intestinal wall layers

Contains the usual arteries, veins, and nerve and lymph

T or F: Most Merkel's diverticula are asymptomatic

True

What condition does a symptomatic Merkel's diverticulum resemble?

Appendicitis

What does a Merkel's diverticulum act as a lead point for?

Intussusception

Which intestines telescope in the event of a Merkel's diverticulum intussusception?

Proximal intestines telescope into the distal intestines

What can plug the lumen of a Merkel's diverticulum?

Fecal material

What can result from plugging of the Merkel's diverticulum?

Ischemia and gangrene

What results from trapping bacteria in a Merkel's diverticulum?

Infection/inflammation

perforation

sepsis

What can result from a rupture of an infected Merkel's diverticulum?

Acute abdomen

What is can result from an acute abdomen?

Intra-abdominal hemorrhage

Peritonitis

Septicemia

Death

What can an infected Merkel's diverticulum present with?

McBurney's sign

Rovsing sign

Elevated WBCs

What is the name of the sign for pushing slowly and deeply into the left lower quadrant, re-creating right lower quadrant pain?

Rovsing sign

T or F: Rovsing sign is a rebound test

False

What does rovsing sign indicate?

Appendicitis

What is the name for rebound tenderness at McBurney's point?

Mcburney's sign

How is mcburney's sign performed?

Push fingers into mcburney's point and then suddenly withdraw them

What is the positive finding of mcburney's sign?

Severe pain at McBurney's point

What does mcburney's sign indicate?

Appendicitis

What is the term for an open communication between the umbilicus and intestine?

Vitelline fistula

What is the term for a cystic structure that develops within a victualing fibrous cord?

Vitelline cyst

What is the term for adhesions/fibrotic tissue may attach meckel's diverticulum to other structures including umbilical plate?

Vitelline fibrous cord/ligament

What are the different types of persistent vitelline ducts?

Merkel's diverticulum

Vitelline fistula

Vitelline Cyst

Vitelline fibrous cord/ligament

Combinations

Which structures are intraperitoneal?

Abdominal esophagus

Stomach

Duodenal bulb

Jejunum

Ileum

Cecum

Transverse colon

Sigmoid colon

What process pushes fecal material towards the anus?

Peristalsis

/What types of vessels line the gut tube?

delicate arteries, veins, and lymph vessels

What is the term for movement away from the mouth?

Aboral movement

What is the primary sign of small bowel obstruction?

10/10 VAS pain in the abdomen

What are the signs of acute abdomen?

Severe abdominal pain

Vomiting

Nausea

Palpatory abdominal tenderness

What are the potential causes of acute abdomen?

Acute appendicitis

Perforated peptic ulcer

Acture pancreatitis

Diverticulitis

Ovarian torsion

Ectopic pregnancy

Fallopian tube rupture

Intestinal obstruction

Volvulus or intussusception

Ruptured aortic aneurysm

Lacerated liver or spleen

Cholecystitis

Urolithiasis

organ/bowel ischemia from vessel occlusion

What is the primary cause of acute abdomen?

ischemia from vessel occlusion

What are the two main causes of intestinal obstruction?

Technical

Functional (non-mechanical)

What is a mechanical obstruction?

Something physically blocks the intestinal lumen

What is a functional obstruction?

Peristalsis is not working due to enteric nervous system problem

What causes stomach distension with a mechanical obstruction?

Upstream bacteria are trapped and with time multiply

Release gas

What is the most common cause of mechanical intestinal obstruction in adults?

Intestinal adhesions (75%)

What are other common types of mechanical obstruction?

Intestinal hernias (10%)

Intestinal carcinoma (10%)

Other causes (Merkel's diverticulum) (5%)

What are rare causes of mechanical obstruction?

Intussusception

Volvulus

Stricture

Gallstone ileus

External compression

Foreign bodies

What is the most common cause of mechanical obstruction in children?

Intussusception

What is an intussusception?

Proximal intestine telescopes into the distal portion of the intestine

What is a volvulus?

Intestine twists upon themselves and get stuck

What is a stricture?

A tissue buildup within the lumen

What is gallstone ileus?

A fistula (tunnel) occurs between the biliary tree (usually the gallbladder and small bowel)

What is the name sign of bacteria releasing gas in the intestines in an obstruction seen on x-ray?

Stack of coins appearance

What are the two severities of blockage?

Partial blockage

Complete blockage

Which type of blockage leads to electrolyte problems and dehydration?

Complete blockage

What is the main sequela of intestinal blockage?

Intestinal wall ischemia

What is the ultimate sequela of intestinal blockage?

Intestinal necrosis and gangrene

What occurs due to increased bacteria population in the intestine?

Intestinal wall perforation

Peritonitis

Septicemia and hypovolemic shock

What are the clinical signs of abdominal obstruction?

Acute abdomen

dehydration

Emesis

What occurs due to dehydration from intestinal blockage?

Hyponatremia, hypotension

What is emesis?

Severe uncontrolled vomiting

What can entangle the bowels in the Merkel's diverticulum?

The fibrous cord

What does the fibrous cord run between?

Distal ileum and umbilical plate

What occurs when the vitelline duct is completely patent?

Vitelline fistula

What is the primary complication of a vitelline fistula?

Bacteria may infect the walls of the fistula

What is the term for a cavity within the vitelline ligament?

Vitelline cyst

What is the most common location of ectopic?

Gastric mucosa (83%)

What can be secreted by a gastric fistula?

Hydrochloric acid

Intrinsic factor

Pepsinogen

(HIP)

What type of infection can occur due to HIP secretion?

H. pylori

What are the ends of the gut tube?

Oropharyngeal membrane

Cloacal membrane

What are the 3 pieces of the gut tube?

Foregut

Midgut

Hindgut

What are the components of the oropharyngeal membrane?

Buccopharyngeal membrane

Mouth

What are the components of the cloacal membrane?

Cloaca

Cloacal plate

Anus / rectum

What forms the foregut?

Lateral folding

What forms the midgut?

both lateral and caudal-cranial folding

What forms the hindgut?

Lateral folding

What is the name of the opening between the secondary yolk sac and the foregut?

Anterior intestinal portal

What are the derivatives of the forgut?

Pharynx

Esophagus

Tracheobronchial tree (larynx, trachea, brocnhi)

Lungs

Stomach

Liver

Gallbladder

Bile ducts

Pancreas

Proximal duodenum (proximal to major duodenal papilla)

What are the derivatives of the midgut?

Distal duodenum (Distal to the major duodenal papilla)

Jejunum

Ileum

Cecum

Appendix

Ascending colon

Proximal two thirds of the transverse colon

What are the derivatives of the hindgut?

Distal one third of the transverse colon

Descending colon

Sigmoid colon

Rectum

Upper anal canal

What suspends the gut tube in the body cavity?

right and left somatic lateral plate mesoderm

What to the right and left somatic lateral plate mesoderms fuse to form?

dorsal mesentery

Where are the tracheobronchial tree and lungs derived from?

Foregut

What is the dividing line between the foregut and midgut in the duodenum?

Major duodenal papilla

What is the proximal 2/3 of the transverse colon derived from?

Midgut

What is the distal 1/3 of the transverse colon derived from?

Hindgut