The Developmental Origins of the Gut and Accessory Organs Flashcards

1
Q

What is the gut?

A

A tube with accessory tubes that aid in digestion.

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2
Q

What are the accessory organs of the gut?

A

The salivary glands, liver, gall bladder and pancreas.

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3
Q

What organs arise from the gut but are not involved in nutrient extraction?

A

The lung and thyroid

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4
Q

What do the mouth parts arise from?

A

The branchial arches

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5
Q

What structures other than mouth parts do the branchial arches form?

A

Structures in the ear, head and neck.

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6
Q

What is the developmental stage of the human embryo at 32 days?

A

The four branchial arches are arranged symmetrically with the laryngeal pouch between.

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7
Q

What does the laryngeal pouch develop into?

A

The laryngeal groove

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8
Q

What does each segment of the branchial arches contain?

A

Cells that will develop into nerves, connective tissue and arteries surrounded by mesodermal tissue.

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9
Q

What kind of tissue is found on the outside of each branchial arch?

A

Ectodermal tissue

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10
Q

What kind of tissue is found on the inside of each branchial arch?

A

Endodermal tissue

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11
Q

What is the valley between the outside of each branchial arch called?

A

A cleft

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12
Q

What is the valley between the inside of each branchial arch called?

A

A pouch

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13
Q

What do the pouches give rise to?

A

The auditory tube, thymus and thyroid.

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14
Q

What do the clefts give rise to?

A

The skin of the ear, neck and eardrum.

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15
Q

What does the gut develop as?

A

An endodermal tube

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16
Q

What surrounds the endoderm of the gut and forms muscle and connective tissue?

A

The splanchnic mesoderm.

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17
Q

What provides nutrients to the embryo before the development of the placenta?

A

The yolk sac.

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18
Q

When does the foregut start to move and develop?

A

In week 4

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19
Q

What developmental activities are occurring in week 6?

A

The formation of the trachea. The stomach is fully developed and the dorsal and ventral pancreas are developing.

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20
Q

When does the hepatic bud that will become the liver form?

A

Week 4

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21
Q

What happens in week 5?

A

The hepatic bud develops more and starts to differentiate cells into hepatic cells.

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22
Q

What happens in week 6?

A
  • The buds of the endoderm form the pancreas
  • The secretion of enzymes and endocrine secretion hormones begins
  • The pancreas is attached the the gut by the pancreatic duct
  • The pancreatic buds converge to form one organ with acini and Islets of Langerhans
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23
Q

What does the dorsal pancreatic bud form?

A

The exocrine pancreas

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24
Q

How does the dorsal pancreas change in week 6?

A

It elongates and grows around the ventral pancreatic duct.

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25
Q

What are the 5 main regions of the gut?

A
  • The mouth and salivary glands
  • The pharynx and oesophagus
  • The stomach
  • The small intestine (duodenum, ileum and jejunum)
  • The large intestine (colon, rectum and anus)
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26
Q

What initiates the process of digestion?

A

Chewing

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27
Q

Where does most digestion occur?

A

In the lumen of the small intestine.

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28
Q

What is the function of the large intestine?

A

Removes water and electrolytes

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29
Q

Where are most nutrients absorbed?

A

In the small intestine

30
Q

What are the four layers of the gut wall?

A

The mucosa, submucosa, muscularis externa and the serosa.

31
Q

What is the function of the mucosa?

A

It lines the lumen and is highly folded to increase surface area. It is the absorptive surface of the gut and contains mucus.

32
Q

What is the function of the submucosa?

A

It is a thick layer of connective tissue that provides structural support and elasticity.

33
Q

What is the structure of the muscularis externa?

A

It consists of an inner ring of circular smooth muscle and an outer ring of longitudinal muscle and is innervated by the myenteric nerve plexus.

34
Q

What is the structure and function of the serosa?

A

An outer layer of connective tissue that secretes liquid that lubricates organs.

35
Q

What are the sections of the stomach?

A

The oxyntic and pyloric mucosae.

36
Q

What cells are found in oxyntic gastric pit and glands?

A
  • Mucus cells that secrete HCO3 rich mucus
  • Chief cells that secrete pepsinogen that is cleaved to initiate protein digestion
  • Parietal cells that secret HCl
  • Enterochromaffin-like cells (ECL) that secret histamine which stimulates HCl production
37
Q

What cells are found in the pyloric pit?

A
  • ECL cells
  • G cells which secrete gastrin which promotes motility and stimulates other cells
  • D cells which secrete somatostatin in response to acid and inhibits parietal, G and ECL cells.
38
Q

What are the villi of the small intestine lined with?

A

Enterocytes and goblet cells.

39
Q

What is the function of enterocytes?

A

They participate in nutrient absorption and fluid secretion.

40
Q

What is the site of enterocyte regeneration?

A

The Crypt of Lieberkühn

41
Q

What creates mass movement in the large intestine?

A

Simultaneous contraction of the ascending and transverse colon.

42
Q

What mixes matter in the large intestine?

A

Slow haustral contractions

43
Q

What induces the defecation reflex?

A

Distension of the rectum, relaxation of the internal sphincter and increased pressure on the external anal sphincter.

44
Q

What are the primary functions of the colon?

A
  • Absorption of Na, Cl and H2O to condense ileocecal material to stool
  • Absorption of short chain fatty acids
  • Secretion of K, HCO3 and mucus
  • Periodic elimination of faeces
45
Q

What is the largest organ in the peritoneal coelom?

A

The liver

46
Q

What are the functions of the liver?

A
  • To neutralise toxins
  • Glycogen storage and glucose homeostasis
  • Secretes albumin for blood plasma
  • Bile synthesis
  • Fe and Cu recovery
47
Q

How is the liver connected to the gut?

A

By the hepatic and cystic duct

48
Q

What are the sources of blood for the liver?

A

The hepatic artery and hepatic portal vein

49
Q

What is a liver lobule?

A

A unit of liver

50
Q

What is each liver lobule fed by?

A

A branch of the hepatic artery and portal vein.

51
Q

What does each lobule contain?

A

A bile canaliculi.

52
Q

What are hepatic plates?

A

A unit of a lobule

53
Q

What metabolises nutrients in hepatic plates?

A

Cords of hepatocytes

54
Q

What are the functions of hepatic plates?

A

Site of glycogen synthesis and maintenance of blood plasma glucose.

55
Q

What cells produce bile?

A

Hepatocytes

56
Q

What does bile secretion in the gut result in?

A

It emulsifies fats and aids lipid absorption.

57
Q

What are Kupffer cells?

A

A type of macrophage found in the sinusoid that neutralise bacteria and microbial debris.

58
Q

Where is the pancreas located?

A

Along the duodenum

59
Q

Where does glucose homeostasis occur?

A

In the pancreas

60
Q

What hormones does the pancreas secrete?

A

Gastrin, somatostatin and digestive enzymes

61
Q

How is the pancreas connected to the gut?

A

Through the pancreatic duct

62
Q

What is the function of the exocrine pancreas?

A

The drainage of glands into the duodenum

63
Q

What do duct cells secrete?

A

Bicarbonate which neutralises digestive juices.

64
Q

What is the function of acinar cells?

A

To secrete digestive enzymes

65
Q

What do Islets secrete?

A

Metabolic hormones

66
Q

What does secretin induce?

A

Bicarbonate secretion from the pancreatic duct.

67
Q

What does neutralisation of stomach acid result in?

A

Release of cholecystokinin (CKK) which induces release of digestive enzymes from the acini.

68
Q

What are the major digestive enzymes?

A

Pancreatic lipase, trypsinogen, sterol esterase and pancreatic amylase.

69
Q

What is the endocrine pancreas organised into?

A

Islets of Langerhans

70
Q

What do alpha cells produce?

A

Glucagon

71
Q

What do beta cells produce?

A

Insulin

72
Q

What do delta cells produce?

A

Somatostatin in response to acidification of blood.