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COT - Exam 2 > 12.3 - Organization and Embryology of the GI System > Flashcards

12.3 - Organization and Embryology of the GI System Flashcards

1
Q

Describe the characteristics of the esophagus, including epithelium, glands, tissue layers, or any other important structures

A
  • beginning after the upper esophageal sphincter (UES) is lined with SSNK epithelium
  • contains sparse esophageal submucosal glands (esophageal glands proper) in lamina propria
  • contains even sparser esophageal cardiac glands in the lamina propria
  • Contains 2 sphincters
    1) Upper Esophageal Sphincter (UES)
    2) Lower Esophageal Sphincter (LES)
  • mucularis mucosae layer is incomplete near larynx
  • the muscularis externa has skeletal muscle fibers in it (more of them near larynx)
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2
Q

What are the two glands of the esophagus, and what tissue layer are they located in?

A
  • Glands are located in lamina propria layer
    1) Esophageal Submucosal glands = esophageal glands proper
  • sparse
    2) Esophageal cardiac glands
  • even sparser
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3
Q

What are the two sphincters associated with the esophagus

A

1) Upper Esophageal Sphincter (UES)
2) Lower Esophageal Sphincter (IES)
- clinically important
- physiological sphincter
- formed by ICL near the juncture with the stomach

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4
Q

Describe the muscular tissue layers in the esophagus

A

1) Muscularis Mucosae
- is of varying thickness
- incomplete near the larynx
- is innervated by the submucosal (Meissner’s) plexus - (as is the mucosa in general)
2) Muscularis Externa
- novelly includes skeletal muscle fibers (more near the larynx)
- innervated by myenteric (Auerbach’s) Plexus - like the rest of the GI system

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5
Q

What are the 3 histologically distinct regions of the stomach

A

1) cardiac stomach
- near LES
2) fundic stomach
- forming the majority of the organ
3) Pyloric stomach
- near the pyloric sphincter, the junction with the duodenum

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6
Q

What are gastric glands

A

= long, simple tubular glands

  • characteristic of the body of the stomach
  • contain large numbers of parietal cells (produce hydrochloric acid and gastric intrinsic factor)
  • also contain large numbers of chief cells (produce enzyme precursors - i.e. pepsinogen)
  • in cardiac and pyloric regions - the cardiac and pyloric glands are shorter and contain primarily mucous neck cells
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7
Q

What are parietal cells

A
  • in the gastric glands in large numbers

- produce hydrochloric acid and gastric intrinsic factor

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8
Q

What are chief cells

A
  • in the gastric glands in large numbers

- produce enzyme precursors (zymogens) such as pepsinogen

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9
Q

what are Rugae

A

= the anatomical temporary folds of the surface of the stomach

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10
Q

What are the gastric pits

A

= nearly microscopic invaginations in the surface of the stomach
- lined entirely with surface mucous cells in all regions

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11
Q

Describe the muscularis externa of the stomach

A
  • consists of three layers

befitting an organ that is more a bag than a tube

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12
Q

What are the 3 distinct anatomical segments of the small intestine

A

1) Duodenum
2) Jejunum
3) Ileum

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13
Q

What are intestinal villi

A

= the chief novel characteristic of the small intestine

= macroscopic epithelial evaginations

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14
Q

Describe the two most common cells in the intestinal epithelium

A

1) Enterocytes
- have a striated border - consists of dense microvilli and a glycocalyx
2) Goblet cells
- produce mucus

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15
Q

What are the significance of the intestinal crypts

A
  • contain Paneth Cells at their bases

- Paneth cells secrete zymogens

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16
Q

What are enteroendocrine cells (EEC)

A

= also called enterochromaffin cells - because most are reactive for chromium salts
- are found scattered throughout the simple columnar epithelia of the digestive system

17
Q

What are central lacteals

A
  • in the core of the intestinal villi

= lymphatic vessels specialized to carry dietary lipids in the form of chylomicrons

18
Q

Describe the regional specializations within the small intestine

A

1) Brunner’s Glands
- in the submucosa of the duodenum
2) Peyer’s Patches
3) Gut-associated lymphoid tissue (GALT)
- contain lymphoid follicles
- within the ileum

19
Q

What are M-cells

A
  • interact with lymphocytes of the GALT

= specialized cells for transcytotic transport of antigens

20
Q

What are plicae circulares

A

= permanent, circular mucosal folds

- most prominent in the lower duodenum + upper jejunum

21
Q

What are the 5 anatomical portions of the large intestine

A

1) Cecum
2) Ascending Colon
3) Transverse Colon
4) Desccending Colon
5) Rectum (12cm straight section of colon which pierces the peritoneal wall)
- not distinguished from each other histologically except for cecal appendix (vermiform appendix)
- all regions of large intestine lack villi, but possess crypts
- ratio of goblet cells increases as move toward rectum

22
Q

What is significant about the cecal appendix and what is its other name

A

= vermiform appendix

- contains significant amounts of lymphatic tissue + lymphoid follicles

23
Q

What are taenae coli

A

= the discrete bands (up to 3) of the Outer longitudinal layer (OLL) of the muclaris externa,
- the muscularis externa is discontinuous in the large intestine

24
Q

Describe the important characteristics of the anal canal

A
  • approximately 4cm of length
  • contains the transition between the simple columnar epithelium of the colon and the SSK epithelium of the skin (goes to SSNK first)
  • submucosa = specialized with longitudinal folds called anal columns (columns of Morgagni)
  • Has both internal and external anal sphincters
25
Q

What is the pectinate line

A

= the first transition within the anal canal

  • from simple columnar epithelium of the colon to the SSNK
  • is an abrupt transition
26
Q

Describe the specialization of the submucosa of the anal canal

A
  • has longitudinal folds = anal columns = columns of Morgagni
27
Q

Describe the sphincters of the anal canal

A
  • the ILL of the mucularis externa terminates in the internal anal sphincter
  • an external anal sphincter of skeletal muscle is also present
28
Q

Describe the body folding occurring in the 4th week of development and on WRT the GI system

A
  • when body folding is complete the endoderm layer forms the gut tube with 3 regions
    1) Foregut
    2) Midgut
    3) Hindgut
  • enddermal lining of the gut tube is surrounded by lateral plate mesoderm
  • endoderm gives rise to the specific cells of glands associated with the GI tract:
    A) liver
    B) Gall Bladder
    C) Pancreas
29
Q

What is the role of the Splanchnic LPM in the GI development

A
  • gives rise to the remainder of the wall of the GI tract including the stroma of
  • glands
  • muscle
  • CT
  • Peritoneal lining of the gut tube
30
Q

What are the Major glands of the GI system

A
  • salivary glands
  • liver
  • gall bladder
  • pancreas
31
Q

What are the histological layers of the GI from lumen inwards

A

1) Mucosa
= wet lining surface composed of 3 layers
1A - Epithelium - primarily SS or simple columnar
1B - Lamina Propria - well vascularized loose CT (can be quite cellular and may contain glands
1C - Muscularis Mucosae - thin ICL and OLL of smooth muscle, modifies shape of the mucosa
2) Submucosa
- Dense irregular (usually) CT with larger blood vessels, nerves, occasional glands
3) Musclaris Externa
- thicker than the muscularis mucosae
- ICL and OLL are helically arranged (spiral)
- FXNs to move material through the GI tract
4) Adentitia or Serosa
- surrounding layer of supporting CT
- may be either continuous with that of an adjacent organ or body wall (adventitia) or free in a body cavity and covered with a mesothelium (serosa)

32
Q

What are the five main functions of the GI tract that is responsible for the alterations seen in the histological layers of each organ/section of the tract

A

1) Mechanical Propulsion
- the peristaltic and segmental movement of ingested material through the tube
2) Digestion
- both physical breakdown and chemical degradation
3) Absorption
- the uptake into the body of needed substances
4) Secretion
- both lubrication and delivery of digestive enzymes, hormones, antibodies into the lumen
5) Protection
- the defenses that prevent/limit invasion by ingested viruses/bacteria and which, in some areas of the GI tract, protect against self-digestion

COT - Exam 2 (28 decks)

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