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2A - Alimentary System > Embryology of the GI > Flashcards

Embryology of the GI Flashcards

1
Q

When does fertilisation to implantation occur?

A

Week 1

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2
Q

When does the bilaminar germ disk form?

A

Week 2

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3
Q

When does the trilaminar germ disk form?

A

Week 3

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4
Q

When does organogenesis occur?

A

Week 3 to 8

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5
Q

What is organogenesis?

A

The production and development of the organs of an animal or plant

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6
Q

What is responsible for establishing the left sideness of an organ or body body?

A

Genes such as the PTX2 gene

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7
Q

What does mutations in the PTX2 gene result in?

A

Dextrocardia because it is responsible for establishing the left sideness of an organ

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8
Q

What are the general 3 phases of embryological development?

A

1) Growth/proliferation (cell division and elaboration of products)
2) Morphogenesis (development of shape, size of a particular organ or part of the body)
3) Differentiation (maturation of physiological processes)

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9
Q

What does exposure to teratogens during weeks 4 to 8 lead to?

A

Major congenital conditions

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10
Q

What is gastrulation?

A

Process of bilaminar embryonic disc being converted into trilaminar disc

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11
Q

What are the 3 layers of the trilaminar disc?

A

Ectoderm

Mesoderm

Endoderm

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12
Q

What does the ectoderm go onto form?

A

Skin (epidermis, hair, nails)

CNS

PNS

Sensory epithelia of the eye

Ear

Nose

Liver (except parenchyma)

Urinary bladder

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13
Q

What does the endoderm go onto form?

A

Epithelial lining of renal system

GI tract

Liver

Pancreas

Thyroid

Parathyroid parenchyma

Urinary bladder

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14
Q

What does the mesoderm go onto form?

A

Muscle

Bones

Cartilage

Dermis

Vascular system

Most of the CVS connective tissue

Blood cells

Bone marrow

Urogenital system except bladder

Spleen

Suprarenal gland cortex

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15
Q

What are the 3 parts of the digestive system?

A

Foregut

Midgut

Hindgut

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16
Q

What gives rise to the parietal and visceral mesoderm?

A

Lateral plate mesoderm

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17
Q

When does the gut tube form?

A

During the 3rd and 4th week from the endoderm lining the yolk sac

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18
Q

What is the gut tube closed by at the cranial end?

A

Oropharyngeal membrane

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19
Q

What is the gut tube closed by at the caudal end?

A

Cloacal membrane

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20
Q

What does the foregut form?

A

Oesophagus

Stomach

Omental bursa (lesser sac)

Duodenum

Liver and bilary apparatus

Spleen

Pancreas

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21
Q

Explain the development of the oesophagus?

A

1) Develops from cranial part of primitive gut tube
2) Laryngo-tracheal diverticulum (lung bud) develops from the ventral wall of the foregut
3) Tracheo-oesophageal septum divides the foregut tube into the trachea and oesophagus

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22
Q

What is the lung bud also known as?

A

Laryngo-tracheal diverticulum

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23
Q

What divides the foregut tube into the trachea and oesophagus?

A

Tracheo-oesophageal septum

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24
Q

When does the stomach develop?

A

4th week

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25
Q

Explain the development of the stomach?

A

1) Foregut dilates to form the stomach
2) Differential growth of the stomach wall creates the greater and lesser curvatures
3) Stomach rotates and adapts its shape to fit in with the other developing organs
4) Undergoes a 90o rotation around its own longitudinal axis
5) Undergoes an anterio-posterior roation to create final adult position

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26
Q

What is the stomach attached to the dorsal and ventral wall by?

A

Mesogastrium (a mesentery)

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27
Q

Explain the development of the omental bursa (lesser sac)?

A

1) Stomach is attached to dorsal and ventral wall by mesogastrium
2) Rotation along its longitudinal axis pulls the dorsal mesentery to the left creating the omental bursa (lesser sac)

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28
Q

When the stomach rotates on its longitudinal axis, what direction is the ventral mesogastrium pulled in?

A

Right

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29
Q

What is the duodenum formed from?

A

Caudal part of the foregut and cranial part of the midgut

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30
Q

Explain the development of the duodenum?

A

1) Formed from the caudal part of the foregut and the cranial part of the midgut
2) As the stomach rotates the duodenum becomes c-shaped and also rotates
3) Duodenal cap retains its dorsal mesentery but the rest of it is retroperitoneal following the fusion of the dorsal mesentery with the peritoneum of the posterior abdominal wall

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31
Q

What supplies blood to the duodenum?

A

Coeliac trunk and superior mesenteric artery

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32
Q

When does the liver bud appear?

A

Middle of the 3rd week

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33
Q

What is the liver bud also known as?

A

Hepatic diverticulum

34
Q

Explain the development of the liver and gallbladder

A

1) Liver bud appears as outgrowth of endoderm in the distal end of the foregut
2) Liver bud (hepatic diverticulum) grows into septum transversum
3) Connection between the liver bud and foregut (duodenum) narrows to form bile duct
4) Ventral outgrowth from bile duct forms the gallbladder and cystic duct

35
Q

What forms the gall bladder and cystic duct?

A

Ventral outgrowth from the bile duct

36
Q

When is the spleen formed?

A

5th week

37
Q

Explain the development of the spleen?

A

1) Mesenchymal condensation develops in the dorsal mesogastrium near the body wall
2) Mesenchyme differentiates to form the spleen

38
Q

What layer of the trilaminar disc is the spleen formed form?

A

Mesoderm

39
Q

What does the spleen act as up to week 14?

A

Haematopoitic organ (produces blood cells)

40
Q

When is the spleen colonised by T cells?

A

Weeks 15 to 17

41
Q

Wheen does the precurser for B-cells arrive at the spleen so it can begin its lymphoid function?

A

Week 23

42
Q

What is mesenchymal condensation?

A

Occurs when previously dispersed mesenchymal cells gather together to differentiate into a single tissue type

43
Q

What are mesenchymal cells?

A

Multipotent stromal cells that can differentiate into a variety of cell types

44
Q

Explain the development of the pancreas?

A

1) Forms from 2 buds which grow from the endodermal lining of the duodenum
2) As the duodenum rotates the ventral bud also moves to lie close to the dorsal bud
3) Dorsal and ventral bud fuse to form pancreas

45
Q

When does the pancreas form?

A

Week 6

46
Q

What is the main pancreatic duct formed from?

A

Combination of the ventral duct and distal part of the dorsal duct

47
Q

What does the proximal part of the dorsal duct of the pancreas form?

A

Can form an accessory duct

48
Q

What are examples of foregut developmental anomalies?

A

Oesophageal atresia and trachea-oesophageal fistula

Annular pancreas

49
Q

How does oesophageal atresia and trachea-oesophageal fistula happen?

A

If the trachea-oesophageal septum deviates incorrectly then there is an incomplete separation of laryngo-tracheal tube (lung bud)

50
Q

How does annular pancreas occur?

A

If the ventral bud of the pancreas fails to migrate around the duodenum correctly it may cause duodenal stenosis and pancreatic tissue may form in other areas of the foregut (accessory pancreatic tissue)

this is the most common birth defect seen in the pancreas: a ring of extra pancreatic tissue covers the first part of duodenum.

51
Q

What does the midgut form?

A

Distal part of duodenum

Jejunum

Ileum

Caecum

Appendix

Ascending colon

Proximal 2/3rds of the transverse colon

52
Q

Explain the development of the midgut?

A

1) Enlongation of gut tube and its associated mesentery to form primary intestinal loop
2) Cephalic part of primary intestinal loop forms distal duodenum, jejunum and proximal ileum
3) Caudal part of primary intestinal loop forms distal ileum, caecum, appendix, ascending colon and proximal 2/3rds of transverse colon
4) Undergoes rotation and physiological herniation to reach adult pattern

53
Q

What does the cephalic part of the primary intestinal loop go onto form?

A

Distal duodenum

Jejunum

Proximal ileum

54
Q

What does the caudal part of the primary intestinal tube go onto form?

A

Distal ileum

Caecum

Appendix

Ascending colon

Proximal 2/3rds of the transverse colon

55
Q

When does rotation of the primary intestinal loop occur?

A

Week 6

56
Q

Explain the rotation and herniation of the primary intestinal loop?

A

1) Initial rotation pccirs around the axis of the superior mesenteric artery
2) Rotation is 90 degress anti-clockwise
3) Gut tube herniates into the extraembryonic cavity in the umbilical cord
4) Allowing the growth of the gut tube which never had room before due to liver and kidneys
5) Abdominal cavity becomes more spacious during 10th week to intestinal loop moves from the umbilical cord back ino the abdominal cavity

57
Q

What direction is the rotation of the primary intestinal loop?

A

90 degrees anti-clockwise

58
Q

What direction is the cranial part of the primary intestinal loop carried during rotation?

A

Right

59
Q

Why does the abdominal cavity become more spacious during the 10th week?

A

Growth

Regression of kidneys

Slower growth of liver

60
Q

What are some midgut developmental anomalies?

A

Abnormal rotation of primary intestinal loop

Reversed rotation

Omphacocele (abdominal wall birth defect)

Gastrochisis (intestines outside babys body)

Remnants of vitelline duct

61
Q

What is omphacocele?

A

Herniation of abdominal viscera through an enlarged umbilical ring due to failure of the umbilical ring to retract

62
Q

What may omphacocele involve?

A

Liver

Stomach

Intestinal loops

63
Q

What covers omphacocele?

A

Layer of amnion

64
Q

What is amnion?

A

Layer that closely covers the embryo when it is first formed

65
Q

What is gastrochisis?

A

Herniation of abdominal contents directly through the body wall into the amniotic cavity

66
Q

What are remnants of vitelline duct?

A

Small vitelline duct persists forming Meckel’s diverticulum, may form fistula or vielline cyst/ligament

67
Q

What does the hindgut include?

A

Distal 1/3 of transverse colon

Descending colon

Sigmoid colon

Rectum

Upper part of anal canal

68
Q

What is the bladder and urethra formed from?

A

Endoderm of hindgut

69
Q

Explain the development of the hindgut?

A

1) Terminal portion of hindgut joins posterior part of the cloaca (primitive anal canal)
2) The allantois enters the anterior part of the cloaca

70
Q

What is the primitive anal canal called?

A

Cloaca

71
Q

What is the anterior part of the cloaca?

A

Primitive urogenital sinus

72
Q

What is the endoderm/ectoderm boundary of the hindgut development?

A

Cloacal membrane

73
Q

What is cloaca?

A

Endoderm lined cavity with surface ectoderm at its ventral boundary

74
Q

What happens in terms of arteries supplying the gut tube as the body elongates?

A

They subdicide into celiac, superior mesenteric and inferior mesenteric

75
Q

What does the coeliac artery supply?

A

Foregut

it supplies oxygenated blood to the liver, stomach, abdominal esophagus, spleen, and the superior half of both the duodenum and the pancreas.

76
Q

What does the superior mesenteric artery supply?

A

Midgut

the midgut from the ampullary region of the second part of the duodenum to the splenic flexure of the large intestine.

77
Q

What does the inferior mesenteric artery supply?

A

Hindgut

the distal 1/3 of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum

78
Q

What are some examples of hindgut developmental abnormalities?

A

Urorectal fistula

Rectovaginal fistula

Rectoanal atresia

Imperforate anus

79
Q

What is imperforate anus?

A

Failure of anal membrane to breakdown

80
Q

What is a fistula?

A

Abnormal connection between two hollow spaces

81
Q

What is an atresia?

A

Absence or abnormal narrowing of opening in the body

2A - Alimentary System (41 decks)

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