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N320 Neo Peds Pathophysiology > Wk 6 GI Embryology & Anatomy/Phys > Flashcards

Wk 6 GI Embryology & Anatomy/Phys Flashcards

1
Q

The primitive gut tube is derived from the extraembryonic part of embryo’s yolk sac. True or false.

A

False

Extraembryonic yolk sac = 2ndary yolk sac –> provides nutrients to the embryo while utero-placental circulation is estsablished; later assimilited into umbilical cord.

Intraembryonic yolk sac = primitive gut

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2
Q

How is the gut tube formed from the 3 germ cell layers?

A

Endoderm: epithilial lining of digestive tube & digestive organs (liver, gallbladder, & pancreas) arise as buds

Mesoderm: through lateral folding, eventually surrounds the gut tube forming connective tissue & muscular walls.

Ectoderm: forms the neural tube that gives rise to the neural crest cells that invade the mesoderm forming neurons & glial cells intrinsic to GI tract

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3
Q

What are the 3 parts of the endodermal gut tube?

A

Foregut, midgut, & hindgut

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4
Q

What parts of the digestive system arises from the foregut?

A

Esophagus, stomach, proximal duodenum (to ampulla of Vater)

Liver/biliary apparatus

Pancreas

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5
Q

What artery supplies blood to the foregut?

A

Celiac

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6
Q

What parts of the digestive system arise from the midgut?

A

Small intestine (including duodenum distal to the bile duct)

Part of the large intestine: cecum, appendix, ascending colon & proximal transverse colon (2/3 of transverse colon)

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7
Q

What artery supplies blood to the midgut?

A

Superior mesenteric

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8
Q

What parts of the digestive system arise from the hindgut?

A

Large intestines: distal transverse colon, descending colon, sigmoid colon, rectum, superior part of anal canal

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9
Q

What parts of the endodermal gut tube (foregut, midgut, & hindgut) give rise to organs that are not part of the digestive system?

A

Foregut = Lower respiratory system & pharynx –> in the book known as a 4th section of the primitive gut, the Pharyngeal gut (includes the 2 mentioned above & the upper esophagus), the foregut is the lower esophagus down

Hindgut = epithelium of urinary bladder & most of urethra

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10
Q

What eventually forms into the liver, gallbladder, and pancreas?

A

Duodenal buds

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11
Q

By the 4th-6th week, what is a major early hematopoietic organ of the embryo?

A

Liver

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12
Q

When does the bone marrow take over hematopoiesis from the liver?

A

Approx 6 months

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13
Q

At birth a child’s liver is equivalent to an adult’s size. True or false.

A

False, at birth, the liver is 20% of the adult size –> will continue to grow for 25-30 years.

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14
Q

What attaches the liver to the ventral wall?

A

Falciform ligament

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15
Q

What is the respiratory diverticulum?

A

Lung bud

In the embryo, arising frm the foregut, the respiratory diverticulum grows from the ventral wall of the esophagus at its border with the pharyngeal gut.

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16
Q

What is the esophagotracheal septum?

A

The separation between the respiratory diverticulum & the foregut portion that eventually becomes the esophagus

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17
Q

What are the 4 layers of the GI tract? (inside to outside, include the sublayers)

A

Mucosa, submucosa, muscularis, & serosa

Mucosa (epithelium, lamina, muscularis mucosae)

Submucosa

Muscularis (Circular muscle layer, longitudinal muscle layer)

Serosa (connective tissue layer, peritoneum)

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18
Q

By which week of gestation does the respiratory diverticulum separate from the foregut that eventually becomes the esophagus?

A

Wk 4

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19
Q

What are the steps forming the enteric nervous system?

A

1) neural crest cells enter the gut
2) crest cells proliferate
3) crest cells migrate along the gut
4) crest cells differentiate & form connections w/ their targets.

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20
Q

How is the GI tract innervated?

A

ANS - sympathetic slows it down, parasympathetic (vagus nerve) speeds it up

Also have intrinsic innervation - submucosal plexus (Meissner plexus) & myenteric plexus (Auerbach plexus)

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21
Q

Describe the innervation of the stomach.

A

Extrinsic - originate outside stomach –> parasympathetic fibers frm vagus nerve & sympathetic fibers frm the celiac plexus

Intrinsic - originate w/in stomach & respond to local stimuli –> myenteric plexus

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22
Q

What is peristalsis?

A

Coordinated sequential contraction & relaxation of the outer longitudinal & inner circular layers of muscles.

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23
Q

What gestation age does the gut develop normal propulsive motility/peristalsis?

A

30 wks

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24
Q

What gestational age can you swallow?

A

11-12 wks

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25
Q

What gestational age does non-nutritive sucking develop?

A

18-24 wks

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26
Q

What gestational age does coordinated esophageal peristalsis occur?

A

32 wks

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27
Q

What gestational age does nutritive sucking occur?

A

34-35 wks when there is rapid growth of the fetal stomach & small intestine motility

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28
Q

What is the percentage of the blood supplied by hepatic artery and portal vein in the liver?

A

hepatic artery = 25%

portal vein = 75%

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29
Q

What is deglutition?

A

the act of swallowing

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30
Q

What are gastric glands and gastric pits? Location.

A

Location: stomach’s mucosa

Gastric pits: depressions in the epithelial lining of the stomach –> a duct where gastric glands empty into.

Gastric glands: found at the bottom of gastric pits - tubular in nature –> chief cells secrete gastric juice, parietal cells secrete stomach acid.

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31
Q

What are parietal cells? Location & function.

A

Location: stomach mucosa, fundus & body

Function: cells w/in the gastric gland that secrete hydrochloric acid (gastric acid) & intrinsic factor

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32
Q

What are chief cells? Location & function.

A

Location: stomach’s mucosa, fundus & body

Function: cells w/in the gastric gland that secrete pepsinogen & gastric juices

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33
Q

What is pepsinogen and pepsin? Source, action, & stimulus in the GI system?

A

Source: chief cells in stomach

Pepsinogen: enzyme precursor to pepsin; turns into pepsin at pH of 2

Pepsin: enzyme in gastric juice that degrades food proteins into peptides

Stimulus: acetylcholine through vagal nerve stimulation during cephalic & gastric phases

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34
Q

Describe the development of the intestine in the fetus & the gestational week.

A

Wk 4: begins as a single tube

Wk 5-9: tube elongates & herniates into unbilical cord & starts to rotate. Villi are formed in jejunum

Wk 10: tube reenters the abdominal cavity the rotates -270 degrees. Microvilli & crypts of lieberkuhn appear.

Wk 13: muscularis & muscle layers well dvlped

Wk 14: Villi throughout the intestine

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35
Q

When is meconium present in the fetus?

A

Wk 16

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36
Q

What are the parts of the small intestine?

A

Duodenum, jejunum, & ilem.

Duodenum begins at pylorus & ends at the Treitz ligament where it joins the jejunum. The end of jejunum & beggining of ileum not distinguished by anatomic marker, but jejunum slightly larger lumen than the ileum.

37
Q

What is the function of the small intestine?

A
38
Q

What is the Treitz ligament?

A

Suspensory muscle of the duodenum - connects the duodenum to the diaphragm.

Important anatomical landmark of duodenojejunal junction

39
Q

How are the 3 parts of the small intestine suspended or attached?

A

Duodenum: lies behind the peritoneum (retroperitoneal cavity) & attached to posterior abdominal wall.

Ileum & Jejunum: suspended in loose folds frm the posterior abdominal wall by the mesentary.

40
Q

What is the peritoneum? What are the 2 types?

A

Serous membrane surrounding the organs of the abdomen & pelvic cavity

Visceral peritoneum - lies over organs

Parietal peritoneum - lines walls of abdominal cavity

41
Q

What is the peritoneal cavity?

A

The space btwn the visceral & parietal peritoneum.

Contains fluid to lubricate 2 layers & prevent friction during organ movement.

42
Q

What is the mesentery? Location.

A

Location: abdominal cavity

A peritoneal membrane that suspends the ileum & jejunum loosely frm the posterior abdominal wall.

Facilitates intestinal motility & supports blood vessels, nerves, & lymphatics.

43
Q

What artery supplies blood to the small intestine?

A

Duodenum - gastroduodenal artery

Jejunum & ileum - superior mesenteric artery

44
Q

What is plica? Location

A

Location: small intestine

Mucosal folds that slow the passage of food = more time for digestion & absorption

45
Q

What are villi? Discuss location, function, & anatomy

A

Location: small intestine mucosa

Function: Cover the plica (mucosal folds) and secrete enzymes for digestion & absorb nutrients. At sites called tight junctions (where the columnar cells closely adhere to each other), water & electrolytes are absorbed.

Anatomy: composed of enterocytes (absorptive columnar cells) & goblet cells (mucus-secreting)

Each columnar cell has microvilli –> increases surface area for absorption.

46
Q

What is the brush border? Location.

A

Location: small intestine

Simple columnar epithleium covered by microvilli.

Has a coating of unstirred layer of fluid important for absorbtion of substances other than water & electrolytes.

47
Q

What is the lamina propria? Location & function

A

Source: connective tissue layer of the intestine’s mucous membrane, lies beneath the epithelial cells of the villi

Function: Contains lymphocytes & plasma cells. Plasma cells produce immunoglobulins & macrophages.

48
Q

What are crypts of Lieberkuhn? Location & function.

A

Location: space between the bases of the villi of the small intestine.

Function: extend to the submucosal layer; where undifferentiated (stem cells) & secretary cells & Paneth cells are located.

49
Q

What are Paneth cells? Location & function.

A

Location: at the bottom of the crypts of Lieberkuhn found in btwn villi of the small intestine.

Function: protects the small intestine - secretes antimicrobial peptide alpha-defensin 5

50
Q

What happens to the stem cells of the crypts of Lieberkuhn?

A

Stem cells = precursor of columnar epithelial & goblet cells. –> eventually rise frm the base of the crypt & move toward the tip of the villus, maturing in shape & function as they progress. After functioning for a few days, they are sloughed into the intestinal lumen & digested.

51
Q

Where do proteins, carbohydrates, & fats go after absorption?

A

Protein & carbohydrates broken down to amino acids & monosaccharides –> villus capillary –> hepatic portal vein –> liver

Fat broken down to monoglycerides & long-chain fatty acids –> lacteals –> thoracic duct –> systemic circulation –> liver

Fat broken down to short-chain fatty acids & glycerol –> villus capillaries –> portal vein –> liver

52
Q

What is a lacteal? Location & function

A

Location: within the villi of the small intestine.

Function: a lymphatic channel that absorbs & transports fat molecules.

53
Q

How often is the entire epithelial population of the small intestine replaced?

A

Every 4-7 days

54
Q

What major nutrients are absorbed at different sites of the digestive tract?

A

Stomach - alcohol & fluoride

Duodenum - Fats, proteins, sugars, water, iron, vitamins, calcium, magnesium, sodium

Jejunum - sugars, proteins

Ileum - bile salts, vit B12, chloride

Colon - water, electrolytes

55
Q

What are Peyer’s patches? Location & function.

A

Location: ileum of small intestine in the lamina propria

Function: organized lymphoid nodules that protect the ileum

56
Q

What is the ileocecal valve/sphincter?

A

Location: btwn ileum & cecum of large intestine.

Controls flow of chyme & prevents reflux into the small intestine

Normally closed but peristaltic waves cause it to open, allowing small amt of chyme to pass through

Intrinsically regulated

57
Q

Name the sphincters & location of the digestive system from the mouth to the anus?

A

Upper esophageal sphincter (Cricopharyngeal muscle) - prevents entry of air into the esophagus during respiration.

Lower esophageal sphincter (Cardiac sphincter) - prevents regurgitation frm the stomach.

Pyloric sphincter - stomach to duodenum

Ileocecal sphincter - ileum to cecum of large intestines

O’Beirne sphincter - sigmoid colon to rectum

Anal sphincter (internal/external)

58
Q

Describe the formation of the liver in the fetus & the gestational week.

A

Wk 3.5: liver bud

Wk 4-5 - Hepatobiliary frm foregut

Wk 12 - Bile secretion begins

59
Q

Describe the formation of the pancreas in the fetus and the gestational week.

A

Wk 4-5: pancreas dvlped from caudal end of foregut

Wk 12: Islet cells formed

Wk 16: Lipase & trypsin

Wk 22: Pancreatic amylase

60
Q

What vitamins does the liver store?

A

Vitamin A, B12, D, E, & K

61
Q

What mineral does the liver store?

A

iron & copper

62
Q

Which organ secretes bile & which organ stores it?

A

Liver secretes

Gallbladder stores

63
Q

What is enterohepatic circulation?

A

bile recycling

64
Q

Describe the process of bile recycling.

A

Gallbladder releases stored bile during eating to the duodenum.

In duodenum & jejunum, bile salts emulsify fats to form micelles so it can be absorbed.

In ileum, bile salts deconjugated by bacteria & absorbed

Enter the hepatic portal vein to the liver where in the bile acid pool, bile acids conjugated to form bile salts & where heapatocytes form bile acids when synthesizing cholesterol

Rectum - 15-35% of bile salts excreted in feces.

65
Q

What is the ampulla of Vater?

A

The union of the common bile duct of the liver & the pancreatic duct.

It empties into the duodenum through the sphincter of Odi

The pathway of bile secretion

66
Q

What is the role of the exocrine pancreas in the digestive system?

A

Produces enzymes to complete digestion of carbohydrates, proteins, & fats

Produces alkaline fluid that neutralizes chyme creating a duodenal pH that supports enzymes

67
Q

What enzymes does the exocrine pancreas secrete to digest protein, carbohydrate, & fats

A

Protein = proteases

Carbohydrates = amylase

Fats = lipase

68
Q

Name proteases produced by the pancreas

A

Trypsin, chymotrypsin, & carboxypeptidase

69
Q

The pancreas’ digestive enzymes are secreted in their inactive forms to protect the pancreas. What enzyme produced by the duodenum activates these inactive digestive enzymes?

A

Enterokinase

70
Q

Where do proteins, carbohydrates, & fats go after absorption?

A

Protein & carbohydrates broken down to amino acids & monosaccharides –> villus capillary –> hepatic portal vein –> liver

Fat broken down to monoglycerides & long-chain fatty acids –> lacteals –> thoracic duct –> systemic circulation –> liver

Fat broken down to short-chain fatty acids & glycerol –> villus capillaries –> portal vein –> liver

71
Q

Can newborns digest protein, carbohydrates, & fats adequately?

A

Yes - proteins & carbohydrates

No - fats

72
Q

Describe a neonate’s carbohydrate digestion.

A

Neonates = adequate carb digestion

Colonic salvage pathway

Normal disaccharidases @ 28 wks (except lactase - adult levels @ 36 wks)

Normal glucoamylase @ birth

73
Q

What is the colonic salvage pathway?

A

In newborns, lactose that is not absorbed in the small intestines goes into the the colon to minimize carbohydrate loss in stool

The bacterial fermentation of the carbohydrate to hydrogen gas & short-chain fatty acids, which are absorbed by the colon

74
Q

Describe the protein digestion of a neonate.

A

Normal absorption of nitrogen

Increased intestinal uptake of intact protein compared w/ adults –> decr. proteolysis & incr. mucosal permeability

75
Q

Describe the fat digestion of a neonate.

A

Lipases found in breast milk - lipoprotein lipase increases during lactation –> causes prolongued neonatal jaundice in BF infants.

Gastric lipases stimulated by feeding

Pancreatic lipase increase in 1st 6 mos of life.

76
Q

Describe a neonate’s capacity to absorb fat in breast milk & cow milk.

A

Breast milk: A full-term baby & premature baby increases fat absorption until 90% in 1st month

Cow milk: A full-term baby has lower absorption of fat than the BF infant; premature babies substantially lower fat absorption.

77
Q

By what age does the difference in absorption of fat disappear between a full-term breastfed infant and a full-term formula-fed infant?

A

6 months

78
Q

On the 1st day, what is the stomach capacity of a newborn?

A

5-7 mL, small marble, hazelnut

79
Q

What is the stomach capacity of a newborn on day 3?

A

22-27 ml, about 1 oz, usu. size of baby’s fist

80
Q

What is the stomach capacity of a newborn on day 10?

A

45-60 mL, 1.5-2 oz, size of a walnut or a golf ball

81
Q

At what age should solid foods be introduced?

A

6 months

82
Q

In reference to the appendix, what does vermiform mean?

A

“worm-like”

83
Q

What is the length of the appendix?

A

1-12 inches

84
Q

What is the difference between the appendix during childhood vs adulthood.

A

Appendix longest in childhood & shrinks in adulthood.

Opening of apendix closes in most people by middle age

85
Q

What does the appendix contain?

A

Lymphoid tissue

86
Q

What is the bowel length of an infant?

A

250 cm

87
Q

What is the normal bowel length for a child?

A

300-600 cm

88
Q

What is the normal length for an adult?

A

600-800 cm

N320 Neo Peds Pathophysiology (3 decks)

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