Histology Of The Small And Large Intestine Flashcards

1
Q

Endocrine secretion happens in the small intestine. True or false? Thank

A

True

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2
Q

Viewed with the naked eye, the lining of the small intestine shows…

A

…a series of permanent circular or semilunar folds called plicae circulares

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3
Q

Plicae circulares are composed of…

A

mucosa and submucosa

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4
Q

Plicae circulares are best developed in the

A

Jejunum

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5
Q

The entire mucosa of the small intestine is covered by…

A

…short outgrowths called villi

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6
Q

What are intestinal villi?

A

Mucosal(epithelium plus lamina propria) outgrowths that project into the lumen

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7
Q

Which parts of the mucosa form the villi?

A

epithelium plus lamina propria

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8
Q

Each villus has a core of loose connective tissue that extends from the lamina propria. True or false?

A

True

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9
Q

Each villus contains

A
Fibroblasts
Lymphocytes and plasma cells
Smooth muscle fibers
Fenestrated capillaries
A lacteal (a central lymphatic)
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10
Q

Shapes of intestinal villi

A

In the duodenum, they are leaf-shaped but gradually assume finger-like shapes moving towards the ileum

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11
Q

Intestinal villi are covered by…

A

…a simple columnar epithelium of absorptive cells (enterocytes) and goblet cells

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12
Q

What are intestinal crypts or crypts of Lieberkükn?

A

They are small openings of short tubular glands between the villi

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13
Q

The epithelium of each villus is continuous with…

A

…that of the intervening glands

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14
Q

The epithelium of the intestinal glands contain:

A
  • Absorptive/enterocytes
  • Goblet cells,
  • Paneth cells,
  • Enteroendocrine cells
  • Stem cells that give rise to all these cell types
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15
Q

What will you find in the basal half of absorptive cells?

A

An oval nucleus

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16
Q

At the apex of each absorptive cell is…

A

…a homogeneous layer called the striated /brush border

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17
Q

When viewed with the electron microscope, the striated border of absorptive cells is seen as…

A

…a layer of densely packed microvilli covered by glycocalyx

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18
Q

How many microvilli is each absorptive cell estimated to have?

A

An average of 3000 microvilli

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19
Q

Microvilli greatly increase the area of contact between the intestinal surface and the nutrients. True or false?

A

True

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20
Q

Total absorptive area of the intestines

A

200m.square

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21
Q

What absorb the nutrient molecules produced by digestion?

A

Enterocytes

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22
Q

Which cells are interspersed between the absorptive cells?

A

Goblet cells

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23
Q

Goblet cells are less abundant in the ___ but are abundant in the ____?

A

They are less abundant in the duodenum and more numerous in the ileum

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24
Q

Which cells produce glycoprotein mucins that are hydrated to form mucus to protect and lubricate the lining of the small intestine?

A

Goblet cells

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25
Q

Paneth cells are exocrine cells with large eosinophilic secretory granules. True or false?

A

True

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26
Q

Paneth cells are located in…

A

…the basal portion of the intestinal crypts below the stem cells (arrow heads)

27
Q

Paneth cells undergo exocytosis to release…

A

…lysozymes, phospholipase A2, and defensins

28
Q

Products of exocytosis of Paneth cells do what?

A

They bind and breakdown membranes of microorganisms and bacterial cell walls

29
Q

Paneth cells functions

A

–Innate immunity

–Regulation of the microenvironment of the intestinal crypts

30
Q

Enteroendocrine cells represent…

A

…part of the widely distributed diffuse neuroendocrine system

31
Q

Upon stimulation, enteroendocrine cells secrete…

A

…various peptide hormones by exocytosis

32
Q

Effects of hormones secreted by enteroendocrine cells

A

Paracrine (local) or endocrine effects which include:

  • Control of peristalsis
  • Regulation of secretions necessary for food digestion
  • Sense of being satiated after eating
33
Q

What are M cells?

A

They are specialized epithelial cells for transport of particles and microorganisms

34
Q

M cells are located in…

A

the ileum, overlying the lymphoid follicles of Peyer patches

35
Q

M cells contain

A

macrophages and lymphocytes

36
Q

Functions of M cells

A

They are important in the defense provided by mucosal immunity and transport of particles and microorganisms

37
Q

The lamina propria move round the core of each intestinal villus, bringing with it microvasculature, lymphatics, and nerves. True or false?

A

False. It penetrates.

38
Q

What are responsible for the rhythmic movements of villi which are important for efficient absorption?

A

Smooth muscle fibers inside the villi

39
Q

What facilitates local movements of the plicae circulares that help propel lymph from the lacteals into submucosal and mesenteric lymphatics?

A

Contractions of the muscularis mucosae

40
Q

What are the duodenal Brunner glands?

A

Large clusters of branched tubular mucous glands present in the proximal part of the duodenum with small excretory ducts opening among the intestinal crypts

41
Q

The mucus produced by the Brunner glands is acidic with pH from 2 to 4.8. True or false?

A

False. It is alkaline with pH 8.1-9.3

42
Q

Where are Peyer’s patches present in the ileum?

A

In both the lamina propria and submucosa

43
Q

Peyer’s patches are…

A

…lymphoid nodule aggregates and an important component of the mucosa-associated lymphoid tissue (MALT)

44
Q

The muscularis of the small intestine is composed of…

A
  • an internal circular layer
  • an external longitudinal layer between which is the myenteric (Auerbach) nerve plexus
    • The serosa- Covered by a thin serosa
45
Q

Function of the myenteric (Auerbach) nerve plexus

A

It produces peristalsis

46
Q

What kind of serosa covers the small intestine?

A

Thin serosa

47
Q

Lacteals are especially important for…

A

…lipid absorption

48
Q

The mucosa of which organ in the GIT lacks villi?

A

Large intestine

49
Q

Which part of the intestine lacks folds?

A

Everywhere except the rectum

50
Q

The whole length of the large intestine is penetrated by…

A

…tubular intestinal glands

51
Q

The glands and the intestinal lumen of the large intestine are lined by…

A

…absorptive, goblet and a few population of the enteroendocrine cells

52
Q

Absorptive cells of the large intestine are called…

A

Colonocytes

53
Q

Properties of colonocytes

A

They have irregular microvilli and dilated intercellular spaces indicative of active fluid
absorption

54
Q

In which part of the large intestine are Goblet cells most abundant?

A

Towards the distal part of the colon and the rectum

55
Q

Functions of goblet cells in the large intestine

A

Production of mucus for lubrication

56
Q

The lymphoid cells and lymphoid nodules of the lamina propria oftentimes extend into the submucosa of the large intestine. True or false?

A

True

57
Q

The richness in MALT in the large intestine is orchestrated by…

A

…the large bacterial population in this segment of the digestive tract

58
Q

The appendix with little or no absorptive function, plays important role in MALT. True or false?

A

True

59
Q

Omental appendages stem from…

A

…the serosa

60
Q

The muscularis of the large intestine is made up of…

A

…longitudinal and circular layers

61
Q

Type of epithelium at the anorectal junction

A

Stratified squamous epithelium of the skin at the anus

62
Q

The mucosa and submucosa of the anal canal form…

A

…several longitudinal folds called the anal columns

63
Q

Fate of the circular layer of the rectum

A

Near the anus, the circular layer is thickened to form the internal anal sphincter

64
Q

What is Crohn disease?

A

A chronic inflammatory bowel disease that occurs most commonly in the ileum or colon. It causes excessive lymphocytic activity and inflammation in any or all the tract producing pain, localized bleeding, malabsorption and diarrhea