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

Wk 6 GI Embryology & Anatomy/Phys Flashcards

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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
What gestational age does non-nutritive sucking develop?
18-24 wks
26
What gestational age does coordinated esophageal peristalsis occur?
32 wks
27
What gestational age does nutritive sucking occur?
34-35 wks when there is rapid growth of the fetal stomach & small intestine motility
28
What is the percentage of the blood supplied by hepatic artery and portal vein in the liver?
hepatic artery = 25% portal vein = 75%
29
What is deglutition?
the act of swallowing
30
What are gastric glands and gastric pits? Location.
**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.
31
What are parietal cells? Location & function.
Location: stomach mucosa, fundus & body Function: cells w/in the gastric gland that secrete hydrochloric acid (gastric acid) & intrinsic factor
32
What are chief cells? Location & function.
Location: stomach's mucosa, fundus & body Function: cells w/in the gastric gland that secrete pepsinogen & gastric juices
33
What is pepsinogen and pepsin? Source, action, & stimulus in the GI system?
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
34
Describe the development of the intestine in the fetus & the gestational week.
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
35
When is meconium present in the fetus?
Wk 16
36
What are the parts of the small intestine?
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
What is the function of the small intestine?
38
What is the Treitz ligament?
Suspensory muscle of the duodenum - connects the duodenum to the diaphragm. Important anatomical landmark of duodenojejunal junction
39
How are the 3 parts of the small intestine suspended or attached?
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
What is the peritoneum? What are the 2 types?
Serous membrane surrounding the organs of the abdomen & pelvic cavity Visceral peritoneum - lies over organs Parietal peritoneum - lines walls of abdominal cavity
41
What is the peritoneal cavity?
The space btwn the visceral & parietal peritoneum. Contains fluid to lubricate 2 layers & prevent friction during organ movement.
42
What is the mesentery? Location.
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
What artery supplies blood to the small intestine?
Duodenum - gastroduodenal artery Jejunum & ileum - superior mesenteric artery
44
What is plica? Location
Location: small intestine Mucosal folds that slow the passage of food = more time for digestion & absorption
45
What are villi? Discuss location, function, & anatomy
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
What is the brush border? Location.
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
What is the lamina propria? Location & function
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
What are crypts of Lieberkuhn? Location & function.
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
What are Paneth cells? Location & function.
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
What happens to the stem cells of the crypts of Lieberkuhn?
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
Where do proteins, carbohydrates, & fats go after absorption?
**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
What is a lacteal? Location & function
Location: within the villi of the small intestine. Function: a lymphatic channel that absorbs & transports fat molecules.
53
How often is the entire epithelial population of the small intestine replaced?
Every 4-7 days
54
What major nutrients are absorbed at different sites of the digestive tract?
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
What are Peyer's patches? Location & function.
Location: ileum of small intestine in the lamina propria Function: organized lymphoid nodules that protect the ileum
56
What is the ileocecal valve/sphincter?
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
Name the sphincters & location of the digestive system from the mouth to the anus?
**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
Describe the formation of the liver in the fetus & the gestational week.
Wk 3.5: liver bud Wk 4-5 - Hepatobiliary frm foregut Wk 12 - Bile secretion begins
59
Describe the formation of the pancreas in the fetus and the gestational week.
Wk 4-5: pancreas dvlped from caudal end of foregut Wk 12: Islet cells formed Wk 16: Lipase & trypsin Wk 22: Pancreatic amylase
60
What vitamins does the liver store?
Vitamin A, B12, D, E, & K
61
What mineral does the liver store?
iron & copper
62
Which organ secretes bile & which organ stores it?
Liver secretes Gallbladder stores
63
What is enterohepatic circulation?
bile recycling
64
Describe the process of bile recycling.
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
What is the ampulla of Vater?
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
What is the role of the exocrine pancreas in the digestive system?
Produces enzymes to complete digestion of carbohydrates, proteins, & fats Produces alkaline fluid that neutralizes chyme creating a duodenal pH that supports enzymes
67
What enzymes does the exocrine pancreas secrete to digest protein, carbohydrate, & fats
Protein = proteases Carbohydrates = amylase Fats = lipase
68
Name proteases produced by the pancreas
Trypsin, chymotrypsin, & carboxypeptidase
69
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?
Enterokinase
70
Where do proteins, carbohydrates, & fats go after absorption?
**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
Can newborns digest protein, carbohydrates, & fats adequately?
Yes - proteins & carbohydrates No - fats
72
Describe a neonate's carbohydrate digestion.
Neonates = adequate carb digestion Colonic salvage pathway Normal disaccharidases @ 28 wks (except lactase - adult levels @ 36 wks) Normal glucoamylase @ birth
73
What is the colonic salvage pathway?
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
Describe the protein digestion of a neonate.
Normal absorption of nitrogen Increased intestinal uptake of intact protein compared w/ adults --\> decr. proteolysis & incr. mucosal permeability
75
Describe the fat digestion of a neonate.
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
Describe a neonate's capacity to absorb fat in breast milk & cow milk.
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
By what age does the difference in absorption of fat disappear between a full-term breastfed infant and a full-term formula-fed infant?
6 months
78
On the 1st day, what is the stomach capacity of a newborn?
5-7 mL, small marble, hazelnut
79
What is the stomach capacity of a newborn on day 3?
22-27 ml, about 1 oz, usu. size of baby's fist
80
What is the stomach capacity of a newborn on day 10?
45-60 mL, 1.5-2 oz, size of a walnut or a golf ball
81
At what age should solid foods be introduced?
6 months
82
In reference to the appendix, what does vermiform mean?
"worm-like"
83
What is the length of the appendix?
1-12 inches
84
What is the difference between the appendix during childhood vs adulthood.
Appendix longest in childhood & shrinks in adulthood. Opening of apendix closes in most people by middle age
85
What does the appendix contain?
Lymphoid tissue
86
What is the bowel length of an infant?
250 cm
87
What is the normal bowel length for a child?
300-600 cm
88
What is the normal length for an adult?
600-800 cm

N320 Neo Peds Pathophysiology (3 decks)

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