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Medical Science > Digestive System > Flashcards

Digestive System Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

5 parts of a tooth

A 
Enamel
Dentin
Pulp
Cementum
Periodontal ligament
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2
Q

Enamel description

A

Crystalline rods of calcium phosphate and carbonate
No living cells
Hardest tissue of the body
No sensation

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3
Q

Dentin description

A

Contains odontoblasts

Similar to bone but cells occur nearby in the pulp instead of scattered through the dentine

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4
Q

Pulp description

A

Soft tissue

Contains blood vessels, nerves and lymphatics

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5
Q

Cementum description

A

Calcified connective tissue covering the root

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6
Q

Periodontal ligament description

A

Collagen fibres linking the bone of the socket to the cementum
Rapid turnover

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7
Q

Enamel location

A

Outside layer of the crown

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8
Q

Dentin location

A

Underneath enamel

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9
Q

Pulp location

A

Underneath dentin

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10
Q

Cementum location

A

In the root on the outside of the dentin

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11
Q

Periodontal location

A

Covers cementum

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12
Q

Odontoblasts

A

Tooth cells around the outside of the pulp

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13
Q

Periodontal ligament functions

A

Protection

Force transducer

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14
Q

Importance of vitamin C

A

Collagen synthesis
Without it, periodontal ligament gets destroyed without being replaced, disconnecting the tooth from the alveolar bone and allowing teeth to fall out
Scurvy

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15
Q

Describe the tongue muscles

A

Skeletal muscle allowing voluntary manipulation
Longitudinally arranged muscle fibres around the outside
Transverse muscle fibres and vertical muscle fibres alternating in groups along the tongue

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16
Q

Transverse contraction in the tongue

A

Narrowing and protruding

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17
Q

Vertical contraction in the tongue

A

Narrowing

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18
Q

3 types of papillae on the tongue

A

Fungiform
Filiform
Vallate

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19
Q

Fungiform papillae

A

On the tip of the tongue
Medium sized
Few tastebuds

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20
Q

Filiform papillae

A

Covering the tongue
Small
No tastebuds

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21
Q

Vallate papillae

A

Middle of the tongue
Large
Most tastebuds found here

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22
Q

3 major salivary glands

A

Parotid
Sublingual
Submandibular

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23
Q

Parotid salivary gland

A

Under ear

Serous cells

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24
Q

Sublingual salivary gland

A

In cheek

Mucous cells

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25
Q

Submandibular salivary gland

A

By jawbone

Serous and mucous cells

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26
Q

Serous cells

A

Secrete enzyme rich secretion of amylase and lysozyme

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27
Q

Saliva makeup

A

Water
Mucous
Enzymes

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28
Q

Amylase function

A

Breaks down starchy debris left between teeth to stop bacteria feeding

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29
Q

Lysozyme function

A

Antibacterial enzyme

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30
Q

3 ways to increase internal surface area of the small intestine

A

Circular folds (plicae circularis)
Evaginations
Invaginations

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31
Q

Increasing external surface area of the small intestine

A

Gross convolutions

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32
Q

Four tunics of the gut tube

A

Mucosa
Submucosa
Muscularis externa
Serosa (or adventitia)

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33
Q

Mucosa layers

A

Epithelium
Lamina propria
Muscularis mucosae

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34
Q

Gut tube epithelium function

A

Protection, absorption or secretion

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35
Q

Lamina propria

A

Loose connective tissue providing a soft fibrous bed for epithelium
Carries nerves and blood capillaries populated with defensive cells
Support

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36
Q

Muscularis mucosae

A

Two thin layers of smooth muscle, inner circular and outer longitudinal
Provides mucosa with movement independent of external muscle coat

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37
Q

Submucosa

A

Thick bed of loose connective tissue carrying larger blood vessels, lymphatic vessels and nerves
Connects mucosa to external muscle coat but allows some movement between the two
Support

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38
Q

Muscularis externa

A

External smooth muscle
In two layers to produce peristalsis
Inner circular, outer longitudinal
Myenteric nerve plexus occurs between layers

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39
Q

Serosa

A

Slippery outer covering for gut tube
Two layered, outer mesothelium sits on bed of connective tissue
Also known as visceral peritoneum

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40
Q

Adventitia

A

Outermost connective tissue layer referred to as adventitia when structure is not in contact with body cavity
Same as serosa

41
Q

Enteric nervous system

A

Guts autoregulation

Controls submucosa and myenteric nerve plexus

42
Q

Submucosal nerve plexus

A

Bottom of submucosa

Coordinates muscularis mucosa

43
Q

Myenteric nerve plexus

A

Between inner circular muscle and outer longitudinal muscle of the muscularis externa
Coordinates layers

44
Q

Describe peristalsis movement

A

Coordinated contraction of outer muscular layer shortening and contraction of inner muscular layer narrowing causes bolus of food to be pushed inwards and downwards

45
Q

Functions of the oesophagus

A

Transport

Protection

46
Q

Epithelium of mucous membrane

A

Stratified squamous epithelium with sacrificial outer layers for protection against abrasive fragments of food
Stem cells just above the basement membrane divide and migrate upwards to replace sloughed off cells
Entire epithelium renewed every 7 days

47
Q

External muscle of the oesophagus

A

Smooth muscle

Skeletal muscle in the upper third to allow rapid contraction and voluntary control of swallowing

48
Q

Serosa of the oesophagus

A

Mostly does not lie in a body cavity so lacks a serosa
Instead covered with fibrous adventitia which attaches it to neighbouring organs e.g. trachea
Abdominal oesophagus only part lined with serosa

49
Q

Four regions of the stomach

A

Cardia
Fundus
Body
Pylorus

50
Q

Describe the stomach

A

J shaped bag on left side
Enlargement of gut tube
Capacity of about 1.5 L
Storage - food can be eaten more quickly than it can be digested and absorbed

51
Q

Pyloric sphincter

A

Well developed muscular sphincter at outlet of stomach

52
Q

Rugae

A

When stomach is empty, it is lined with longitudinal folds called rugae

53
Q

Epithelium of mucosa in stomach

A

Forms many gastric pits lined with mucus secreting cells and gastric glands which open into the pits

54
Q

External muscle of stomach

A

Three layers:
Outer longitudinal
Inner circular
Innermost oblique

55
Q

Functions of the stomach

A 
Storage
Secretion of acid, enzymes and mucus
Digestion
Absorption
Transport
Protection
56
Q

Function of the innermost oblique layer

A

Churns and mixes food

57
Q

Cells in the mucosa of the stomach

A 
Surface mucous cells
Undifferentiated cells
Parietal cells
Mucous neck cells
Chief cells
Gastrin cells
58
Q

Surface mucous cells

A

Secrete insoluble alkaline mucous which protects mucosa from acid and pepsin
Stops ulceration
Disintegrates at the top of the gastric pit

59
Q

Undifferentiated cells

A

Stem cells which divide to generate new epithelium

60
Q

Parietal cells

A 
Secrete HCl (as H+ and Cl- separately) to sterilise and acidify the environment
Secretes intrinsic factor
61
Q

Mucous neck cells

A

Secrete soluble acid mucous at mealtimes

62
Q

Chief cells

A

Secrete pepsinogen (precursor to pepsin to prevent autodigestion) and gastric lipase
Exocrine cells
Apical secretions

63
Q

Gastrin cells

A

Enteroendocrine cells
Responsible for gut hormone secretions int surrounding blood vessels
Gastrin stimulates secretion of acid and pepsinogen, increases muscular contractions of stomach and relaxes pyloric sphincter
Basal secretions

64
Q

Intrinsic factor

A

Necessary for vitamin B12 absorption which is essential for red blood cell synthesis

65
Q

Hepatocytes

A

Epithelial cells of the liver derived from embryonic endoderm

66
Q

3 things hepatocytes require

A

Access to nutrient laden blood drained from intestinal wall
Access to oxygenated blood from the systemic circuit
Access to ducts which drain bile to the gall bladder

67
Q

Roles of bile

A

Emulsification of lipids to increase lipid surface area by breaking down and making lipid digestion easier by pancreatic enzymes
Helps wit fat absorption

68
Q

Describe the structure of a hepatocyte

A

When stacked together form passageways to segregate bile
Bile kept in the bile canaliculus in hepatocyte cytoplasm, connected to lymph space of Disse by tight junctions
Lymph space of Disse has microvilli on the inside surface and endothelial cells on the outside surface with lymph in between
Sinusoid space on the outside of the lymph space of Disse contains red blood cells

69
Q

Endothelial cells by hepatocytes

A

Fenestrated enodthelial cells act as a filter to allow passage of lymph and exclusion of red blood cells

70
Q

Liver lobule

A

Plates of hepatocytes stacked together in hexagonal cross section
Incoming oxygenated systemic blood via the hepatic artery
Incoming nutrient laden blood via the hepatic portal vein
Outgoing deoxygenated blood via the central vein
Outgoing bile via the canaliculus leading into bile duct

71
Q

Pancreas

A

Exocrine gland manufacturing precursors of digestive enzymes and secreting them as alkaline pancreatic juice
Endocrine gland - Islets of Langerhans secrete insulin and glucagon into the bloodstream to regulate blood glucose levels

72
Q

Pancreatic precursors

A

Secreted via duct system leading to duodenum
Converted to active form once they arrive in duodenum to digest proteins, carbohydrates, lipids and nucleic acids
Avoids autodigestion

73
Q

Acinus

A

Secretory unit of the pancreas (leaf of the tree)

74
Q

Intercalated ducts

A

Twig of the tree

75
Q

Main pancreatic duct

A

Trunk of the tree

76
Q

Small intestine regions and sizes

A

Duodenum: 25 cm
Jejunum: 1 m
Ileum: 2 m

77
Q

Small intestine

A

3 cm in diameter
Over 3 m long
Most digestion and absorption

78
Q

Brunner glands

A

Secretes a bicarbonate rich mucus that neutralises acidic chyme and optimises pH for pancreatic enzymes

79
Q

Plicae

A

Circular folds 1 cm high

Each plica covered with mucosa and has a core of submucosa

80
Q

Villi

A

Mini finger like projections 1 mm high

Covered in epithelium with lamina propria core

81
Q

Microvilli

A

Microscopic projections 1 micron high
Form a brush border on the surface of individual absorptive cells
Covered with cell membrane and filled with cytoplasm

82
Q

Mucosal cells of the small intestine

A 
Columnar absorptive cells (enterocytes)
Goblet cells
Enteroendocrine cells
Undifferentiated cells
Paneth cells
Smooth muscle
83
Q

Enterocytes

A

Absorb small molecules resulting from digestion

84
Q

Enteroendocrine cells in small intestine mucosa

A

Secrete secretin into lamina propria capillaries

85
Q

Paneth cells

A

Phagocytic cells that secrete lysozyme
Secretions on the apical surface
Defence

86
Q

Lacteal

A

Lymph vessels in each villus
Lymph is ‘milked’ along the lacteal by contraction of smooth muscle fibres in lamina propria which shorten the villus
Arise from muscularis mucosae

87
Q

Secretin release

A

From enteroendocrine cells
Stimulated by arrival of acid chyme
Secretin in the bloodstream stimulates pancreatic juice release

88
Q

Villus atrophy

A

Decrease in numbers of villi means absorption is impaired

Common in coeliac disease

89
Q

Describe the large intestine

A

Soft muscular tube about 1.5 m long with 7 parts
Absorbs salts and water (1 L/day)
Conversion of chyme into feces
Absorb vitamin K and B produced by bacteria
Secretion of mucous to lubricate feces

90
Q

Ileocecal valve

A

Conrols intermittent flow of chyme from ileum into cecum

91
Q

Cecum

A

Dilated pouch
Bacteria responsible for digestion instead of enzymes
Humans can’t digest cellulose alone

92
Q

Feces

A 
30% bacteria
30% undigested dietary fibre
Cells shed from intestinal lining
Mucous
Brown pigment from bacterial decomposition of bilirubin
93
Q

Reasons for diarrhoea

A

Increased speed of intestinal motility decreases time chyme spends in large intestine - less water absorption, watery feces
Cholera locks G protein in active state which increases ion secretion - water follows, watery feces
Decreased enterocyte function

94
Q

Mucosa of the large intestine

A

No villi but many intestinal glands
Surface epithelium cells are absorptive enterocytes
Intestinal glands contain goblet cells but not Paneth cells
Clusters of lymphocytes in lamina propria due to lots of bacteria

95
Q

Describe the intestinal gland of the colon

A

Columnar absorptive cells (enterocytes)
Goblet cells (more further down to increase lubrication)
Undifferentiated cells
White blood cells (mostly lymphocytes for protection against bacteria)

96
Q

Rectum

A

Final 20 cm of gut tube

97
Q

Anal canal

A

Last 2 cm of rectum

Closed by internal and external sphincter

98
Q

External muscle of the large intestine

A

Outer longitudinal muscle thickened in three strips called teniae coli
Tonically active teniae coli contract to pull intestinal tube into sac like pockets called haustra coli which change shape and position

Medical Science (11 decks)

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