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unit 6: microanatomy > GI Tract II > Flashcards

GI Tract II Flashcards

1
Q

How long is the small intestine and how long is each section of the small intestine?

A

6 meters long in total

Duodenum: 25 cm
Jejunum: 2.5m
Ileum: 3.5m

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2
Q

What are the major functions of the small intestine?

A

1- Move Chyme
2- Absorb Nutrients
3- Immunodefense

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3
Q

What three structures increase the lumenal surface area of the small intestine?

A

Plicae circularis (AKA valves of Kerckring), villi and microvilli

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4
Q

What are plicae circularis? How much do they increase surface area?

A

Permanent transverse circular folds of mucosa and submucosa that increase surface area 2-3 times

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5
Q

What are villi? How much do they increase surface area?

A

Finger like projections of the surface epithelium and lamina propria that increase surface area 10 times

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6
Q

What are microvilli? How much do they increase surface area?

A

Projections of the apical plasma membranes that increase surface area 20 times

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7
Q

What are Crypts of Lieberkuhn?

A

Simple tubular glands that extend from the surface epithelium down to the muscular mucosae

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8
Q

What are the 6 major cell types of the small intestine epithelium?

A 
1- Absorptive Cell
2- Goblet Cell
3- Enteroendocrine Cell
4- Paneth Cell
5- Stem Cell
6- < (microfold) cell
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9
Q

Describe the cell structure of absorptive cells?

A

Tall columnar cells with a striated border

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10
Q

How big are microvilli?

A

1 micron tall and 0.1 micron in diameter

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11
Q

What do absorptive cells secrete?

A

Disaccharidases and peptidases

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12
Q

Describe the action of disaccharidases and peptidases?

A

The are secreted by absorptive cells and bind to microvilli where they produce monosaccharides and amino acids for absorption

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13
Q

What happens to lipids when they are absorbed by absorptive cells?

A

Reesterified to TGs, converted into chylomicrons and released from lateral surface into the lamina propria where they are absorbed by the central lacteals

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14
Q

Describe the cell structure of goblet cells?

A

Unicellular glands

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15
Q

What do goblet cells produce?

A

Acid glycoproteins of the mucin type that lubricate and protect eh small intesting

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16
Q

Where are the goblet cells most abundant?

A

Less abundant in the duodenum and increase in number towards the ileum

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17
Q

Describe the cell structure of enteroendocrine cells?

A

Unicellular glands

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18
Q

What do enteroendocrine cells synthesize?

A

Synthesize hormones and vasoactive peptides

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19
Q

Where are enteroendocrine cells located?

A

Most are in the basal portion of the crypts of Lieberkuhn

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20
Q

How/ Where are paneth cells typically found?

A

In small groups at the base of crypts

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21
Q

What is in the apical cytoplasm of paneth cells?

A

Large, eosinophilic granules of lysozyme that has antibacterial activity which controls intestinal flora

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22
Q

Where are stem cells located?

A

Near the base of the crypts

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23
Q

How often do stem cells repopulate crypts and villi?

A

Every 3-6 days

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24
Q

How often do stem cells replace paneth cells?

A

Every 30 days

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25
Q

Where are M (microfold) cells found?

A

In the ileum only

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26
Q

What are M cells?

A

Specialized epithelial cells that cover peyer’s patches

27
Q

Describe the basement membrane beneath M cells?

A

Discontinuous basement membrane

28
Q

What is GALT?

A

Gut Associated Lymphoid Tissue (includes Peyer’s patches)

29
Q

What percentage of the mucosa is GALT?

A

25%

30
Q

What are Peyer’s patches? Where are they found?

A

Groups of 20-40 lymphatic nodules found in the ileum that are covered by M cells

31
Q

How are antigens from the lumen transported to Peyer’s patches?

A

They are taken up by the M cells and then delivered to lymphocytes and other cells in the peyer’s patches

32
Q

Where is IgA synthesized?

A

By plasma cells in the peyer’s patches

33
Q

Describe how sIgA is produced?

A

A glycoprotein (SC) is synthesized by the absorptive cells and then inserted into the basal membrane. Dimers of IgA bind to SC, enter by endocytosis and exit the apical plasma membrane with SC bound…this is sIGA

34
Q

What does sIgA bind?

A

Antigens, toxins, microorganisms

35
Q

Where are Brunner’s glands found?

A

In the submucosa of the duodenum

36
Q

What is the role of Brunner’s glands?

A

Mucous type of glands that secrete alkaline mucous that helps to protect against stomach acid and provide an optimum pH for pancreatic enzyme action

37
Q

True or False:

Most of the duodenum has an adventitia

A

True

38
Q

What part of the intestine has the most highly developed plicae cirularis?

A

Jejunum

39
Q

Which part of the intestine has the longest villi?

A

Ileum

40
Q

Which part of the small intestine has a serosa?

A

Jejunum

41
Q

What are the five gross subdivisions of the large intestines?

A 
1- Colon
2- Cecum
3- Appendix
4-Rectum
5- Anal Canal
42
Q

What are the major functions of the large intestine?

A

1- Absorption of water, salts, minerals, and vitamins
2- Mucus Secretion
3- Storage and elimination of fecal material

43
Q

What are plicae semilunaris and where are they found?

A

Temporary folds of the mucosa and submucosa that are in the colon and cecum

44
Q

Are there villi in the colon and cecum?

A

No

45
Q

Describe the crypts of the colon and cecum (what are they lined with)?

A

Lined with simple columnar epithelium with a striated border

46
Q

True or false:

Goblet cells are not found in the colon and cecum.

A

False…goblet cells are especially large and numerous

47
Q

What is unique to the colon and cecum?

A

Muscularis externa…the outer longitudinal smooth muscle is subdivided into tree bands called taenia coli and there is a thin layer of longitudinal smooth muscle between bands

48
Q

What do the taenia coli pucker to form?

A

Pucker the colon into haustra

49
Q

True or false:

The transverse and sigmoid colon have serosa

A

true

50
Q

What doe the ascending and descending colon and the cecum have?

A

Adventitia

51
Q

What is different between the epithelium of the colon/ cecum and the appendix?

A

The appendix has fewer and shorter crypts

52
Q

The submucosa of the appendix is frequently _____________.

A

Edematous

53
Q

True or false:

There are few lymphoid cells/ nodules in the appendix

A

False…the lamina propria has MANY lymphoind cells and lymph nodules that often interrupt the muscularis mucosae

54
Q

Is there a serosa in the appendix?

A

Yes

55
Q

Describe the musclaris externa of the appendix?

A

Has two complete thin layers and no taneia

56
Q

How is the rectum divided?

A

Into the upper rectum and anal canal

57
Q

What does the upper rectum resemble?

A

The colon…but it has less lymphoid tissue and no taenia coli

58
Q

How long is the anal canal?

A

2.5- 4 cm long

59
Q

How type of epithelium lines the rectum?

A

It changes….starts as…Simple columnar epithelium then changes to stratified cuboidal and then stratified sqamous nonkeratinized epithelium then stratified squamous keritinized

60
Q

Where can circumanal glands be found?

A

in the ano-cutaneous area

61
Q

What are circumanal glands?

A

Apocrine sweat glands

62
Q

Which layer of circular smooth muscle thickens to form the internal anal sphincter?

A

inner layer of circular smooth muscle

63
Q

Which layer of circular smooth muscle is replaced by skeletal muscle to form the external anal sphincter?

A

Outer longitudinal layer

unit 6: microanatomy (5 decks)

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