GI Patho

Question 1

What is the significance of the transition from a sterile gut to a colonized microbiome in the GI system?

Answer 1

It is an important step in postnatal adaptation.

This transition supports the development of the immune system and digestion.

Question 2

What are the primary roles of the GI tract?

Answer 2

Digestion and absorption of nutrients, immune function, and supporting endocrine and exocrine roles.

The GI tract is the largest and most active immune organ of the body.

Question 3

From which germ cell layers is the GI tract derived?

Answer 3

All 3 germ cell layers: ectoderm, mesoderm, and endoderm.

Each layer contributes to different structures within the GI system.

Question 4

What structures are derived from the foregut?

Answer 4

• Pharynx
• Esophagus
• Stomach
• Duodenum (proximal part)
• Liver
• Gallbladder
• Bile ducts
• Pancreas

The foregut is supplied by the celiac artery.

Question 5

What structures are derived from the midgut?

Answer 5

• Small intestine (distal duodenum)
• Cecum
• Appendix
• Ascending colon
• Part of transverse colon

The midgut is supplied by the superior mesenteric artery.

Question 6

What structures are derived from the hindgut?

Answer 6

• Part of transverse colon
• Descending colon
• Sigmoid colon
• Rectum
• Part of anal canal
• Epithelium of urinary bladder
• Most of urethra

The hindgut is supplied by the inferior mesenteric artery.

Question 7

What is the primitive gut?

Answer 7

It forms as a cavity lined by endoderm, giving rise to the epithelial lining of the digestive tube.

Digestive glands like the liver, gallbladder, and pancreas arise from this lining.

Question 8

What occurs during week 3 of embryological development of the GI tract?

Answer 8

Liver bud present, peritoneal cavity and mesentery forming.

This marks the beginning of gut formation.

Question 9

What significant changes occur during weeks 5 and 6 in GI development?

Answer 9

• Liver increases in size
• Midgut herniates into abdominal sac
• Stomach begins to rotate
• Fusion of dorsal and ventral pancreatic buds

These changes are largely driven by hematopoiesis.

Question 10

What happens to the lumen of the duodenum during week 7?

Answer 10

It becomes progressively smaller and eventually occludes.

This can lead to duodenal atresia if not recanalized.

Question 11

What is the role of the enteric nervous system (ENS) in the GI system?

Answer 11

It is the intrinsic nervous system of the GI tract that regulates secretions, controls peristalsis, and communicates with the CNS.

The ENS senses chemical and mechanical changes in the gut.

Question 12

What are the four major layers of the intestinal wall?

Answer 12

• Serosa
• Muscularis
• Submucosa
• Mucosa

There are variations in these layers across different organs.

Question 13

What are intestinal villi?

Answer 13

Small hair-like projections that increase the surface area of the epithelium for absorption.

They contain capillary beds and lacteals.

Question 14

What are the functions of absorptive cells in the gut?

Answer 14

Digestion and absorption of nutrients in chyme.

These cells are found throughout the intestinal mucosa.

Question 15

Which hormone is secreted by G cells?

Answer 15

Intestinal gastrin.

Gastrin stimulates gastric acid secretion.

Question 16

What is the primary function of the pancreas?

Answer 16

It functions in both exocrine (digestive enzymes) and endocrine (hormonal regulation) roles.

The islets of Langerhans are responsible for its endocrine functions.

Question 17

What is the role of the duodenum in digestion?

Answer 17

It regulates stomach emptying and is responsible for enzymatic breakdown of food.

The duodenum also plays a critical role in nutrient absorption.

Question 18

What causes gastroesophageal reflux (GER) in infants?

Answer 18

Transient relaxation of the lower esophageal sphincter (LES).

GER is common in preterm infants.

Question 19

What are warning signs of significant gastroesophageal reflux disease (GERD) in infants?

Answer 19

• Failure to thrive
• Airway issues
• Poor oral intake
• Coughing/choking
• Stridor

These symptoms may indicate severe reflux requiring medical attention.

Question 20

What is the role of colostrum in newborns?

Answer 20

It contains factors that stimulate epithelial cell turnover and maturation, enhancing the gut mucosal immune system.

Colostrum is crucial for newborns’ digestive health.

Question 21

What supplies blood to the jejunum and ileum?

Answer 21

The superior mesenteric artery.

Supplies blood to the intestines including the jejunum and ileum.

Question 22

What is the characteristic of immature myenteric muscle contractions until 32-34 weeks?

Answer 22

They are immature and not fully developed.

This affects intestinal motility in preterm infants.

Question 23

How does intestinal transit time in preterm infants compare to term infants?

Answer 23

It is 2x longer than in term infants.

This can affect nutrient absorption.

Question 24

What are the key features of the jejunum?

Answer 24

• Suspended in its mesentery
• Has many large circular folds called plicae circulares
• Increased surface area for nutrient absorption
• Villi are longer
• Less fat compared to ileum
• Larger diameter.

The jejunum is crucial for nutrient absorption.

Question 25

What is the role of the jejunum in nutrient absorption?

Answer 25

Involved in magnesium absorption and nutrient transfer to the liver via the hepatic portal vein. ## Footnote Nutrients absorbed pass from enterocytes to the liver.

Question 26

What are the characteristics of the ileum?

Answer 26

* Suspended inside the mesentery * Contains abundant Peyer’s patches * Shortest villi of small intestine * Thinner walls than jejunum * Absorbs vitamin B12 and bile salts. ## Footnote The ileum also absorbs products not absorbed by the jejunum.

Question 27

What are the two basic functions of the colon?

Answer 27

* Absorption of water and electrolytes * Storage and elimination of feces. ## Footnote The colon plays a significant role in hydration and waste management.

Question 28

What type of cells line the crypts of the colon?

Answer 28

* Absorptive cells * Goblet cells * Endocrine cells. ## Footnote Goblet cells are disproportionately large in number.

Question 29

What is the primary function of the liver during fetal development?

Answer 29

Hematopoiesis begins in the liver during the 6th week. ## Footnote The liver plays a crucial role in blood cell formation.

Question 30

What are the metabolic functions of hepatocytes?

Answer 30

* Detoxify body waste, hormones, drugs * Synthesize clotting factors * Store glycogen, fats, iron, vitamins. ## Footnote Hepatocytes are essential for maintaining metabolic homeostasis.

Question 31

What is enterohepatic circulation?

Answer 31

The recycling of bile salts between the liver and intestine. ## Footnote Bile salts are crucial for digestion and absorption of fats.

Question 32

Where does protein digestion begin?

Answer 32

In the stomach, aided by hydrochloric acid and pepsin. ## Footnote The process continues in the small intestine.

Question 33

What is the role of gastrin?

Answer 33

* Increases secretion of HCL and pepsinogen * Enhances gastric motility * Stimulates ileal motility. ## Footnote Gastrin is a key hormone in digestive regulation.

Question 34

What initiates carbohydrate digestion?

Answer 34

Salivary amylase in the mouth and pancreatic amylase in the small intestine. ## Footnote Lactase is also important for hydrolyzing lactose.

Question 35

What is the absorption rate of fats in term versus preterm infants?

Answer 35

Term infants absorb 85%, while preterm infants absorb as little as 50%. ## Footnote The type of fat and the presence of bile salts affect absorption.

Question 36

What is the function of bile salts?

Answer 36

Emulsify longer chain fats for absorption. ## Footnote They are essential for the absorption of fat-soluble vitamins.

Question 37

What are antenatal clues for gastrointestinal anomalies in newborns?

Answer 37

* Polyhydramnios * Bile-stained amniotic fluid * Maternal medications. ## Footnote These clues can indicate potential gastrointestinal issues.

Question 38

What is esophageal atresia?

Answer 38

Absence of a normal opening or failure of a structure to be tubular. ## Footnote It is one of the types of tracheoesophageal fistula.

Question 39

What is pyloric stenosis?

Answer 39

Hypertrophic muscle of the gastric outlet causing nonbilious projectile vomiting. ## Footnote It usually presents around 4 weeks of age.

Question 40

What is the incidence of duodenal atresia?

Answer 40

1 in 7000 live births. ## Footnote It is often diagnosed antenatally due to polyhydramnios.

Question 41

What is the common clinical presentation of jejunoileal atresia?

Answer 41

* Abdominal distension * Bilious vomiting * Failure to pass meconium. ## Footnote It results from an in utero vascular insult.

Question 42

What characterizes imperforate anus?

Answer 42

Abnormal development of the urorectal septum leading to incomplete separation of the cloaca. ## Footnote It occurs in 1 in every 400-5000 newborns.

Question 43

What is the most common cause of large bowel obstruction in newborns?

Answer 43

Hirschsprung disease. ## Footnote It results from arrested fetal development of the myenteric nervous system.

Question 44

What is the incidence of malrotation?

Answer 44

1 in 500 live births. ## Footnote It is the most common obstruction of the small bowel.

Question 45

What is omphalocele?

Answer 45

Herniation of abdominal viscera into the umbilical cord covered by a peritoneal sac. ## Footnote It occurs at the time of abdominal wall closure.

Question 46

What is necrotizing enterocolitis?

Answer 46

A spectrum of conditions causing necrosis of the intestine, primarily in preterm infants. ## Footnote It has a multifactorial pathogenesis.

Question 47

What are the clinical signs of spontaneous intestinal perforation?

Answer 47

* Stress * Hypoxia * Shock leading to transient intestinal ischemia. ## Footnote It is a separate clinical entity from NEC.