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Digestive > Microanatomy > Flashcards

Microanatomy Flashcards

1
Q

4 tunics of the digestive system

A

Mucosa
Submucosa
Muscularis externa
Adventitia/Serosa

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2
Q

3 layers of mucosa

A

Epithelium
Lamina propria
Muscularis mucosae

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3
Q

Adventitia

A

Outermost connective tissue between two adjacent structures

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4
Q

Serosa

A

Slippery outer covering for the gut tube between structure and body cavity

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5
Q

Mesothelium

A

Layer of serosa attached to organs that produces serous fluid

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6
Q

Epithelium fuction

A

Protection (physical and chemical)
Secretion
Absorption

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7
Q

Lamina propria function

A

Supportive tissue that allows nutrients to diffuse to avascular epithelium
Both functional and structural support

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8
Q

Muscularis mucosae is only found in:

A

Smooth muscle

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9
Q

Muscularis muscosae function

A

Provides movement to mucosa independent of peristalsis at a microcellular level

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10
Q

Submucosa function

A

Functional and structural support to mucosa

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11
Q

2 layers of muscularis externa

A

Inner circular

Outer longitudinal

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12
Q

Muscularis externa function

A

Generates peristaltic movement

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13
Q

Intraperitoneal organs are covered with:

A

Serosa, lined with a single thin squamous layer of mesothelium

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14
Q

Mesothelium is also known as:

A

Visceral peritoneum

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15
Q

Retroperitoneal organs are covered with:

A

Adventitia on the posterior surface and mesothelium on the anterior surface

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16
Q

Ascites

A

Inappropriate drainage of serous fluid creates pressure, discomfort, abdominal swelling and distortion of visceral organs

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17
Q

Peritonitis

A

Physical damage, chemical irritation and bacterial invasion leads to inflammation which interferes with normal functioning

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18
Q

Amylase

A

Salivary enzyme that digests carbohydrates

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19
Q

Parotid salivary glands

A

Found at upper back of mouth
Only serous acina
Produces 25% of saliva

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20
Q

Sublingual salivary glands

A

Found in lower gum underneath teeth
Mixed, but predominantly mucus acina
Produces 5% of saliva

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21
Q

Submandibular salivary glands

A

Found in lower jaw
Both mucus and serous acina
Produces 70% of saliva

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22
Q

Serous acina produce a _____ secretion

A

Watery

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23
Q

Mucus acina produce a _____ secretion

A

Viscous

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24
Q

Serous acina features

A

Stain dark due to zymogen granules
Nuclei are centrally located and round
Visible myoepithelial cells

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25
Q

Myoepithelial cells

A

Found in both mucus and serous acina

Contract and squeeze secretions into surrounding ducts

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26
Q

Zymogen granules contain:

A

Digestive enzymes such as amylase

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27
Q

Mucus acina features

A

Don’t pick up stain very well
Nuclei peripheral and squished
Contain myoepithelial cells but very squished to the periphery and hard to see
Contain mucus granules

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28
Q

Striated duct features

A

Intralobular
Lots of mitochondria giving a striated appearance
Generate HCO3- and K+

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29
Q

Composition of saliva

A 
99% water
Mucins
Bicarbonate ions
Lysozyme
Lactoferrin
Immunoglobulin A
Amylase
Lipase
Haptocorrin
Kallikrein
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30
Q

Role of mucins

A

Carbohydrate-rich glycoproteins that provide lubrication and prevents bacterial adhesion

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31
Q

Role of bicarbonate in the mouth

A

Counteracts acidic bacterial secretions and protects from acidic vomit

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32
Q

Role of lysozyme

A

Breaks down bacterial cell walls

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33
Q

Role of lactoferrin

A

Defence against iron dependent bacteria

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34
Q

Role of immunoglobulin A in the mouth

A

Important first line of defence in mucus membranes

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35
Q

Role of amylase

A

Active in pH of 4 - 11

Breaks down carbs in the mouth

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36
Q

Role of lipase

A

Optimal pH of 4

Breaks down fats in the mouth

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37
Q

Role of haptocorrin

A

Binds B12 and protects it from acidic stomach environment so it can be absorbed later

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38
Q

Role of kallikrein

A

Serine protease that increases blood flow

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39
Q

Xerostomia

A

Dry mouth

Can be caused by mumps, salivary duct stones, salivary gland tumours, sjogrens syndrome and medications

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40
Q

Hypersalivation

A

Also known as water brash

Associated with many medical conditions, medications and toxins

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41
Q

Area of digestive tract with a dense adventitia

A

Oesophagus
Density means not a lot of room for expansion or compression
Everywhere except for 1-2 cm between diaphragm and stomach because this is a retroperiotoneal area

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42
Q

Function of oesophagus

A

Rapid transport of food bolus to stomach through peristaltic contractions.
Straight tube about 25 cm long with thick muscular walls and a protective lining.
Collapsed outline with folds of submucosa when empty, stretched out as food descends to stomach

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43
Q

Epithelium of oesophagus

A

Thick sacrificial stratified squamous epithelium, non-keratinised in humans. Transitions into simple cuboidal/columnar as it approaches stomach.

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44
Q

Muscularis mucosae of oesophagus

A

Absent/rare near upper oesophagus but developed near stomach. Longitudinal smooth muscle and elastic network.
Allows independent movement and folding of mucosa which aids absorption and digestion when needed.

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45
Q

Muscularis externa of oesophagus

A

Thick inner and outer coats not always regularly circular and longitudinal.
Skeletal muscle present at pharyngeal end, smooth muscle only at gastric end.
Upper and lower sphincters. No obvious muscle thickening but some increase in inner muscle coat for tonal contraction.

46
Q

Achalsia

A

Aperistalsis of the oesophagus

Failure of lower oesophagul sphincter to relax while swallowing

47
Q

Gastro-oesophageal disease

A

Acid reflux causing heartburn and dysphagia

48
Q

Barrets oesophagus

A

Repeated exposure to stomach acid causes cellular shift in lower oesophagus from stratified squamous epithelia to simple columnar epithelia with Goblet cells which can increase susceptibility to oesophageal cancer

49
Q

4 areas of stomach

A

Cardia
Fundus
Body
Pylorus

50
Q

3 muscular layers of stomach

A

Innermost oblique
Inner circular
Outer longitudinal

51
Q

Cardiac glands secrete:

A

Mucus

52
Q

Parietal glands (from fundus and body) secrete:

A

HCl
Intrinsic factor
Pepsinogen
Somatostatin

53
Q

Pyloric glands secrete:

A

Pepsinogen
Mucus
Gastrin
Somatostatin

54
Q

Rugae

A

Transient stomach folds

Visible when empty but not when full due to stretching

55
Q

Cells of the stomach

A 
Simple columnar mucus cells
Mucus neck cells
Undifferentiated stem cells
Parietal cells
Chief cells
Enteroendocrine cells
56
Q

Simple columnar mucus cells of stomach

A

Secrete insoluble alkaline glycoproteins to form a protective mucus bicarbonate barrier, preventing autodigestion

57
Q

Mucus neck cells of gastric glands

A

Secrete soluble acidic glycoproteins when food is present

58
Q

Parietal cells

A

Secrete H+ and Cl- to combine in the lumen
HCl sterilises food and acidifies environment, vital for pepsinogen activation
Also secretes intrinsic factor which enables vitamin B12 absorption

59
Q

Chief cells

A

Secretes pepsinogen from zymogen granules into lumen. Acidity from HCl activates pepsinogen which is cleaved into pepsin

60
Q

Pepsin

A

Endopeptidase that breaks down proteins into peptides

61
Q

3 types of enteroendocrine cells in the stomach

A

G cells
D cells
ECL cells

62
Q

G cells

A

Secrete gastrin which targets parietal and ECL cells

63
Q

ECL cells

A

Enterochromaffin-like cells

Secrete histamine

64
Q

D cells

A

Secrete somatostatin

65
Q

Somatostatin

A

Inhibits insulin and glucagon secretion

66
Q

3 phases of gastric acid secretion

A

Cephalic
Gastric
Intestinal

67
Q

Cephalic phase

A

Occurs at sight/thought of food
PSNS (vagus nerve) stimulation causes ACh and gastrin releasing peptide
Innervate parietal, enteroendocrine, chief and mucus cells

68
Q

Gastric phase

A

Occurs at arrival of food in stomach
Stimulate stretch and chemoreceptors causing reflexive muscularis contraction
Amino acids and high pH detected by enteroendocrine cells which release gastrin, acting on parietal and chief cells

69
Q

Intestinal phase

A

Chyme enters duodenum which stimulates duodenal gastrin release and weakly stimulates acid production

70
Q

Cells of the small intestine

A 
Columnar absorptive cells (enterocytes)
Goblet cells
Enteroendocrine cells
Undifferentiated cells
Paneth cells
71
Q

Enterocytes

A

Columnar absorptive cells
Microvilli brush border to increase surface area
Membrane studded with digestive enzymes e.g. glycosidases, enterokinases and enteropepsidases
Glycocalyx coat which selectively attracts and repels molecules

72
Q

Goblet cells

A

Secrete mucus
No microvilli brush border
Mucinogen granules fill apical cytoplasm
Basal nucleus

73
Q

Enteroendocrine cells

A

Usually release secretions basolaterally into capillaries

Secretory granules release CCK, serotonin and somatostatin

74
Q

Serotonin actions on small intestine

A

Increases peristalsis

Increases intestinal secretions

75
Q

Somatostatin actions

A

Increased absorption
Increased smooth muscle contraction
Gastrin inhibition

76
Q

CCK actions

A

Contracts gallbladder
Inhibits gastrin in the stomach
Releases pancreatic enzymes

77
Q

Secretin actions

A

Released bicarbonate from pancreas and bile

Inhibits gastrin in stomach

78
Q

CCK stimulation

A

Fatty acids and amino acids

79
Q

Secretin stimulation

A

Acidic chyme

80
Q

Paneth cells

A

TNF-alpha, lysozyme and defensin secretions

81
Q

TNF-alpha

A

Produces inflammation in response to bacteria and parasites

82
Q

Defensins

A

Increases ion channels in cell membranes of invading organisms and increases permeability

83
Q

Brunners glands

A

Only present in duodenum

Secrete bicarbonate rich mucus

84
Q

Peyers patches

A

Lymphocyte aggregates found in ileum
Macroscopically visible
Core of B lymphocytes with M cells on the outside

85
Q

Plicae circularis

A

Circular folds projecting into the lumen of the small intestine

86
Q

Area of the small intestine with the most plicae circularis

A

Jejunum

87
Q

Main functions of the colon

A

Reabsorb fluids and vitamins

Compact feces

88
Q

Caecum

A

Sac at the beginning of colon that collects and stores arriving materials from the ileocaecal valve and begins the process of compaction

89
Q

Appendix

A

Slender, hollow tube dominated by lymphoid nodules

90
Q

Mucosa of colon

A

Smooth, no plicae of villi
Numerous mucosal glands
Dominated by columnar absorptive cells and Goblet cells

91
Q

Intestinal/mucosal glands are also called:

A

Crypts of Lieberkuhn

92
Q

Columnar absorptive cells of colon

A

Absorb water and electrolytes

Absorb vitamins produced by bacteria (B and K)

93
Q

Goblet cell presentation in colon

A

Become more numerous further down the colon due to increased dehydration of feces requiring more mucus for easy passing

94
Q

Lamina propria of colon

A

Dense layer of collagen immediately below surface epithelium

Numerous lymphatic nodules extending down into submucosa

95
Q

Muscularis externa of colon

A

Circular and longitudinal muscle layers

Longitudinal muscle layer thickened into three bands called teniae coli

96
Q

Teniae coli

A

Allow segments of colon to contract independently, pulling it into haustra coli pockets

97
Q

Colon coverings

A

Adventitia on posterior surface

Serosa everywhere else

98
Q

Oesophagus germ cells

A

Located at basal epithelium, migrate up to surface

Replaced every few days

99
Q

Stomach germ cells

A

Located near neck of gastric glands, migrate both up and down
Superficial cells replaced every few days, deeper cells less often

100
Q

Small intestine germ cells

A

Located in the lower crypts of Lieberkuhn, migrate both up and down
Superficial cells replaced every few days, deeper cells less often

101
Q

Large intestine germ cells

A

Located in lower crypts of Lieberkuhn, migrate up to surface

Replaced every few days

102
Q

Hepatic lobule

A

Anatomical hexagonal subunit of liver

103
Q

Liver acinus

A

Functional division of liver - rhombus shape where blood flows to opposite corners towards central veins

104
Q

Portal lobule

A

Triangle formed by 3 central veins. Bile flows from central veins towards portal space - opposite direction to blood flow

105
Q

Hepatocytes

A

Cells of the liver that make up a hepatic lobule. Cells and sinusoids radiate out away from central vein

106
Q

Sinusoid

A

Very leaky capillary that supplies mixed blood to hepatocytes, then collected by central vein in the middle
Can fit more than one red blood cell through lumen at once

107
Q

Kupffer cells

A

Specialised macrophages in the liver lining the walls of the sinusoids
Prevent obstruction and provide antibacterial defence

108
Q

Endothelium in liver

A

Leaky, fenestrated cells that line the sinusoids

Also have intercellular openings

109
Q

Fat storing cells in liver (pericytes)

A

Located between endothelial basement membrane and neighbouring hepatocytes
When quiescent - vit A metabolism
When activated - scar tissue formation

110
Q

Bile canaliculi

A

Membranous infoldings form channels between hepatocytes which drain to bile ductules then into the bile duct in the portal space for gallbladder storage

Digestive (9 decks)

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