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Histology > Digestive System 3 > Flashcards

Digestive System 3 Flashcards

1
Q

What do the intestines of a mammal consist of?

A
  • small intestine (duodenum, jejunum, ileum)
  • large intestine (cecum, colon, rectum, anal canal)
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2
Q

What is the tissue found in the small intestine?

A

simple columnar epithelium
+ striated border

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3
Q

What tissue is the large intestine composed of?

A

simple columnar epithelium
+ striated border

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4
Q

What other cells, except of simple columnar epithelium, can be found in the intestines?

A

goblet cells

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5
Q

How is the tunica muscularis of the intestines organised?

What type of cells?

A
  • inner circular layer
  • outer longitudinal layer

smooth muscle cells

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6
Q

How do the intestines compare from a histological point of view?

A

They are very similar.
duodenum, jujenum, ileum are very similar; but also, small and large intestines are very similar.

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7
Q

What is the outermost layer of the intestines? Why?

A

Tunica Serosa
- serous cells provide secrete which lubricates the surface of intestines,
- allows intestines to glide against other organs

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8
Q

What is the second layer of the intestines (from the outside)?

A

Tunica Muscularis
- outer longitudinal layer
- inner circular layer
- (both layers = smooth muscle cells)

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9
Q

What is the 3rd layer (counting from the outside) of the intestines? What tissue is it based on?

A

Tunica Submucosa
- based on loose connective tissue

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10
Q

What is the final tissue layer of the intestines (most inner layer)? What cells is it composed of?

A

Mucosa:
- simple columnar epithelium
- striated border

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11
Q

What is meant by the “striated border” of the intestines?

A

“striated border” = microvilli

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12
Q

What are ‘microvillis’?

A

very small projections located on EACH simple columnar epithelial cell.

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13
Q

What do microvilli provide the intestines with? Why is this necessary?

A
  • microvilli increase the intestinal surface area
  • necessary to absorb water and nutrients more effectively
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14
Q

What is the major difference between the histological structure of the small and large intestine?

A

villi!
(only found in the small intestine)

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15
Q

What is the special structure of the small intestine?

A

villi

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16
Q

What are the differences in villi between species?

A

ruminants: short and thick
carnivores: long and slender

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16
Q

What is located at the bases of villi?

A

Invaginations of the epithelium called the intestinal glands.

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17
Q

What are the invaginations in the epithelium at the villi bases called?

A

intestinal glands

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18
Q

What occurs in the invaginations? How does it occur? What is a different name of the villi invaginations?

A

invaginations = intestinal glands
- replacement of the mucosal epithelium
- by cell division

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19
Q

By what process is mucosal epithelium replaced?

A

cell division

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20
Q

What is a distinctive feature of the small intestine?

A

Mucosa takes up a very large portion of the entire intestinal wall/organ.
- 80% of entire wall
- 20% remaining layers (tunica submucosa, muscularis and serosa)

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21
Q

What type of projections can be spotted in the small intestine?

A

outer projections: villi
inner projections: intestinal glands

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22
Q

What other organ has glands in the digestive system? What are their names?

A

stomach
gastric glands (in gastric pits)

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23
Q

What is the difference between glands in the stomach and small intestine?

A

stomach- gastric pits
small intestine- intestinal glands

stomach: invaginations (gastric pits) which only later open into gastric glands

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24
Q

What type of cells are located in intestinal glands?

A
  • stem cells
  • paneth cells
  • enteroendocrine cells
  • goblet cells
  • enterocytes
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25
Q

What is the function of stem cells in intestinal glands? Why is it important?

A
  • renewal of the intestinal epithelium,
  • important because the simple columnar epithelium has a very limited lifespan
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26
Q

What are feces based on?

A
  • dead epithelial cells
  • only small portion is undigested food
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27
Q

What are paneth cells? What is their main function?

A
  • innate immune system cells
  • produces enzymes (lysozyme) (which breaks down bacterial walls and recognises viruses)
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28
Q

What is the function of the lyzosyme enzyme? What cell secretes it?

A
  • paneth cells secrete lyzosymes

function:
- innate immune response
- break down bacterial walls
- recognise viruses
- phagocytosis (similar to macrophages and neutrophils)

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29
Q

Are paneth cells effective?

A

paneth cells secrete lyzosymes which are not 100% effective, however they do play a very good job in innate immune defence.

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30
Q

What is the function of endocrine cells in the intestinal gland?

A
  • secrete hormones: secretin, cholecystokinin, GIP

SECRETIN:
- regulates secretions in the pancrease, liver, small intestines and stomach,
- regulates pH levels

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31
Q

What feature makes the intestines similar to the stomach?

A

endocrine cells (both the stomach and small intestine have hormone secreting cells in their glands)

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32
Q

What is the function of secretin in the small intestine? What is it released by?

A

secretin is released by enteroendocrine cells.

function:
- regulates secretions (pancrease, liver, small intestines and stomach)
- regulates pH levels

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33
Q

What is the function of goblet cells in the small intestine?

A
  • not specific to the small intestine (can be found in almost the entire digestive tract)

function:
- production of mucous (necessary to lubricate food)

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34
Q

What is the most important cell of the small intestine?

A

enterocyte

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35
Q

What is enteritis?

A
  • the inflammation of intestines
  • affects enterocyte cells
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36
Q

What is present in the lamina propria and submucosa of the small intestine?

A

Peyer’s patches

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37
Q

What are “payers patches”? Where are they found?

A
  • aggregations of lymphatic nodules
  • present in the lamina propria and submucosa of the small intestine (especially ileum)
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38
Q

Where are peyer’s patches most common?

A
  • small intestine
  • ileum
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39
Q

What is the function of peyer’s patches?

A
  • guarantee immune surveillance of the intestinal lumen
  • facilitate the production of an immune response within
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40
Q

To what system do the intestines qualify too? Why? What cells are present?

A

immune system
- most exposure to pathogenic bacteria and viruses takes place within the digestive tract

cells:
- lymphocytes (deeper to the mucosa)
- peyer’s patches
- paneth cells (lysozymes)

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41
Q

What other glands (apart from intestinal glands) can be found in the intestines? Where exactly are they found? What other name can they be reffered to as?

A

Brunner’s glands (Duodenal glands)
- found in the duodenum
- within the submucosa and lamina propria

compound tubular submucosal glands

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42
Q

What type of glands are Brunner’s glands?

A

compound tubular submucosal glands

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43
Q

What is the main function of Brunner’s glands? Why do they do what they do?

A
  • produce a mucous-rich alkaline secretion (i.e. mucous containing bicarbonate) –> protects the duodenum from the acidic content (introduced by the stomach)
  • provide an alkaline condition for intestinal enzymes to be active –> enable absoption to take place
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44
Q

State the species differences of Brunner’s glands.

A

carnivores, sheep, and goats:
- limited to the initial or mid region of the duodenum

horses, pigs, and cows:
- extend into the jejunum

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45
Q

What is opposite in the stomach and intestines?

A

the pH levels!
- stomach= very low (acidic)
- intestines= high (alkaline)

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46
Q

Why are the intestines alkaline?

A

Due to Brunner’s glands secreting alkaline mucous.

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47
Q

Why do the intestines have to have a basic pH?

A

To allow intestinal enzymes to be active and therefore enable the absorption of nutrients.

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48
Q

What would happen if Brunner’s glands wouldn’t exist?

A
  • high pH would not be maintained in the intestines
  • proper digestion would not take place
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49
Q

Explain the structure of the large intestines.

A
  • similar to the small intestine
  • lack villi
50
Q

What additional structure does the large intestine have? Where is it located?

A
  • prominent LYMPHATIC NODULES
  • present in the submucosa
51
Q

What type of cells increase in the intestinal epithelium? Why?

A
  • GOBLET CELLS
  • increase the production of mucous (increase lubrication)
  • additional lubrication is required as water is removed from the intestinal contents (in preparation for defecation)
52
Q

What happens to intestinal contents in preparation for defacation?

A

water is removed

53
Q

How to distinguish the large intestine easily?

A
  • villi are absent
  • equal layer proportions (tunica mucosa=tunica submucosa=tunica muscularis=tunica serosa)
  • has invaginations (crypts)
  • no paneth cells
  • more goblet cells
54
Q

What cells line the large intestine?

A
  • the same cells that line the small intestine (simple colimnar epithelium)
  • NO PANETH CELLS
  • stem cells
  • enteroendocrine cells
  • MORE GOBLET CELLS
  • enterocytes
55
Q

What cells are absent in the large intestines?

A

paneth cells

56
Q

What is the effect of the lacking paneth cells in the large intestines?

A
  • large intestine is not less effective in immune responses
  • instead, there is a greater number of other immune system cells= LYMPHOCYTES
57
Q

What are the pear patches below the mucosa of the intestines?

A

lymphocytes

58
Q

What are the species differences of the cecum?

A

carnivores: small
herbivores: well developed (simpler stomach)

59
Q

What type of bands are present in the tunica muscularis of the large intestine? What are their latin names?

A

Taeniae ceci:
- outer layer
- longitudinal bandss of smooth muscle
- vary in number

Taeniae coli:
- longitudinal bands of smooth muscle
- PIGS and HORSES ONLY

60
Q

Which way does the rectum course?

A

retroperitoneally

61
Q

As the rectum courses retroperitoneally, what changes?

A

tunica serosa –> tunica adventitia

62
Q

What type of component is taeniae?

A
  • anatomical
  • it can be sen with the naked eye
  • smooth muscle cells combined in a very thick string
  • in tunica muscularis
  • longitudinal muscle bands
63
Q

What is special about the rectum?

A

the rectum is no longer positioned inside a cavity:
tunica serosa –> tunica adventitia

  • attaches rectum to outer structures
  • more stable, doesn’t move
64
Q

How to distinguish the large instestine from the stomach?

A

1) GASTRIC PITS:
stomach: glands opening into gastric pits
large intestine: no glands opening into invaginations

2) TUNICA MUSCULARIS:
stomach: 3 layers (inner oblique, middle circular, outer longitudinal)
large intestine: 2 layers (inner circular, outer longitudinal)

65
Q

What is the liver? What does it divide into?

A
  • large lobed gland
  • divided into lobes
  • lobes divide into numerous classic lobules
66
Q

What is each lobe covered by? What is beneath it?

A
  • covered by mesothelium
  • beaneath: CAPSULE OF THE LIVER (thin connective tissue layer)
67
Q

What is the “capsule of the liver”?

A

thin layer of connective tissue below the mesothelium

68
Q

What do classic lobules consist of?

A
  • sinusoids
  • hepatocytes (plates of parenchyma cells radially organised about a central vein)
69
Q

What are hepatocytes?

A

plates of parenchyma cells radially organised about a central vein

70
Q

What are the species differences of the liver? What allows one to distringuish between species?

A

ALL ANIMALS (except pig):
- lobules are indistinctly seperated from one another

PIG:
- boundries of connective tissue between lobules clearly identify their boundries

swinie sie widocznie roznia od innych

71
Q

What type of organ is the liver? Why?

A
  • parenchymal organ
  • it does not have a lumen
72
Q

What is a parenchymal organ? What structural components do parenchymal organs have?

A

1) only 2 components: parenchyma and stroma
PARENCHYMA: part of organ responsible for its function
STROMA: connective tissue providing organ shape and mechanical protection

73
Q

What are the functions of the liver? What part of the organ are they based on? What cells qualify to this part?

A

parenchyma of the liver (hepatocytes)- responsible for function

  • produce immune system components
  • provide metabolism for incoming substances (drugs, medication, alcohol, toxic substances)
  • provide physiological metabolism (produce fat, glucose)
  • produces bile (necessary for digestion)
  • storage of blood
74
Q

What cells in the liver function as the parenchymal part?

A

hepatocytes

75
Q

What is the parenchyma of an organ?

A

functional unit

76
Q

What is an organs stroma?

A
  • connective tissue
  • shapes an organ (combines cells)
  • provides protection from the mechanical aspect
77
Q

Explain the stroma of the liver.

A

stroma always begins with:
- CAPSULE of dense connective tissue

capsule has branches, that go deeper into the organ dividing the organ into:
- LOBES

smaller branches go deeper into the organ, dividing it into:
- CLASSIC LOBULES

78
Q

What shape do classic lobules have?

A

hexagonal or pentagonal

79
Q

What part of the liver do its lobules divisions qualify to as?

A

stroma

80
Q

What type of component are the liver’s lobules?

A

structural, not functional.

81
Q

Are ‘lobules’ visible in animals other than pigs? What structure helps orientation?

A

connective tissue between parts, seperating lobules into lobules is not visible.

BUT it is possible to orient where a lobule would be, as each lobule structure has a CENTRAL VEIN.

82
Q

What structure allows one to distinguish where a classic lobule is placed, and its borders?

A

the central vein

83
Q

What are the interlobular connective tissues of the liver?

A
  • bile duct
  • hepatic artery
  • portal vein
84
Q

What is the ‘portal triad’?

How else can it be referred to as?

A

the interlobular connective tissue, consisting of:
- bile duct
- hepatic artery
- portal vein

also known as: hepatic triad, and liver triad

85
Q

Explain the flow of liquids in the portal triad.

A

Blood travels in one direction, while, bile travels in the opposite direction (billary system).

86
Q

What does blood travel in in the liver?

A

enters:
- hepatic artery
- portal vein

through:
- hepatic sinusoids

exits:
- central vein
- –> sublobular vein
- –> hepatic vein

87
Q

How does blood travel into the liver?

A

through the hepatic artery and portal vein

88
Q

How does blood travel within the liver?

A

through sinusoids

89
Q

How does blood travel out of the liver?

A

through the central vein into the sublobular vein and finally into the hepatic vein.

90
Q

Where does blood enter when using the hepatic artery and portal vein?

A

into hepatocytes

91
Q

What are hepatic sinusoids?

A

capillaries, specific to the liver (gaps in their walls)

92
Q

Why are sinusoids capillaries ‘specific to the liver’?

A

they have gaps in their walls

93
Q

What is important to note about the blood going through the liver?

A

only a minor part goes through the system, a major part leaves the blood stream and enters hepatocytes.

94
Q

What happens to blood in the liver? What can it be compared to?

A

blood is filtered through hepatic cells (like through a sponge).

95
Q

What is the purpose of having two main blood insertions (ie. hepatic artery and portal vein) having the same direction of blood stream?

where does portal vein blood come from?

A

hepatic artery:
- oxygenated blood
- provides oxygen for hepatic cells (ie. parenchyma)

portal vein:
- nutrient rich blood

portal vein blood comes from the intestines.

96
Q

Where do the two blood sources unite?

A

the hepatic artery and portal vein unite at the central vein.

97
Q

What do hepatocytes produce? What direction does it flow in? Where to? What is its final destination?

A
  • hepatocytes produce bile.
  • bile flows in the opposite direction to the blood stream
  • bile is collected in the bile duct
  • goes further into the bile duct system, and then is collected in the gall bladder
98
Q

What is the classic hepatic lobule? Shape? Cells?

A
  • structural lobule of the liver
  • hexagonal mass
  • liver cells
99
Q

What is the portal lobule? What else is it referred to as?

A
  • territory of the liver tissue around a portal triad.
  • nutritional lobule of the liver.
100
Q

What are the hepatic acinus of Rappaport? Shape? Function?

A
  • diamond shaped area of the liver parenchyma
  • forms the structural and metabolic function of the liver
101
Q

Explain the structure of the liver acinus. How many zones is it divided into? What is the zone division based on?

A
  • divided into 3 zones
  • based on the gradient of blood supply

ZONE 1:
- around the vascular backbone
- well oxygenated

ZONE 2:
- intermediate zone
- moderately oxygenated

ZONE 3:
- close to the central vein
- least oxygenated

102
Q

Explain the 3 zones of the liver acinus. Location and oxygenation.

A

ZONE 1:
- around the vascular backbone
- well oxygenated

ZONE 2:
- intermediate zone
- moderately oxygenated

ZONE 3:
- close to the central vein
- least oxygenated

103
Q

What are the three concepts of liver lobules?

A
  • classical hepatic lobule
  • portal lobule
  • hepatic acinus of Rappaport

1) normal with dot inside; 2) between 3 dots (PORTAL); 3) between 2 dots

104
Q

What is the name of the structural lobule of the liver?

A

classical hepatic lobule

105
Q

What is the name of the nutritional lobule of the liver?

A

the portal lobule

106
Q

What serves metabolic and structural functions of the liver?

A

hepatic acinus of Rappaport

107
Q

What is the only type of lobule which can be seen?

A

classical hepatic lobule

108
Q

Why are zones important in the acinus of Rappaport?

A

Different zones have different functions.

i.e.
zone 1: highly oxygenated blood –> generation of glucose molecules
zone 3: limited oxygen –> conversion of lipids

109
Q

What is the pancrease? What is it surrounded by?

A
  • an organ
  • surrounded by thin connective tissue which extends between lobules of the parenchyma
110
Q

What is scattered around the pancrease?

A
  • endocrine pancreatic islets
  • exocrine acinar cells
111
Q

What are the exocrine secretory units? What do they secrete?

A

Exocrine acinar cells produce trypsinogen and chymotrypsinogen.

112
Q

What type of glands are present in the pancrease? What does each part contain?

A

both endocrine glands and exocrine glands.

endocrine glands- pancreatic islets
exocrine glands- acinar cells

113
Q

Explain the exocrine part of the pancrease.

A

stroma components:
- connective tissue capsule (dense regular connective tissue)
- branches dividing pancrease into lobes and lobules (not clear shape like the liver!)

114
Q

What type of cells make up acini? How are acini connected?

A

acini:
- pyramidal shaped cells
- connected by a duct system

115
Q

What is the initial portion of the exocrine duct system known as? What is it lined by?

A

the intercalated duct
- lines by flattened simple cuboidal epithelial cells

116
Q

What does the intercalated duct connect with? What is it lined by?

A

the intercalated duct connects with the intralobular duct,
- lined by simple cuboidal epithelium

117
Q

What else is located in the connective tissue between lobules? What is it lined by?

except: intralobular duct, intercalated duct

A

interlobular duct
- lined with simple columnar epithelium

118
Q

What are the three ducts in the pancrease? Order? Cells?

A

1) intercalated duct (lined by flattened simple cuboidal epithelial cells)
2) intralobular duct (lined with simple cuboidal epithelial cells)
3) interlobular cells (lined with simple columnar epithelium)

119
Q

What is the parenchyma of the pancrease based on? What are they composed of? Shape?

A

acinuses (composed of pancreatic acinar cells- triangular in shape)

120
Q

What do acinar cells secrete? Active or inactive? What occurs later?

A

trypsinogen and chymotrypsinogen:
- inactive forms of enzymes
- activated in the small intestine (due to high pH levels)

121
Q

Why does the pancrease not have active enzymes?

A

to prevent the pancrease from digesting itself.

122
Q

How are enzymes transported from the pancrease to the small intestine?

A

through the duct system
- intercalated duct
- intralobular duct
- interlobular duct

123
Q

What is the difference between the exocrine and endocrine part of of the pancrease?

A

Exocrine part has ducts.
Endocrine parts has no ducts and duct systems!

Histology (20 decks)

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