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Flashcards in Digestive system Deck (95)
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1

List in sequence the sections of the digestive tract

1. Oral cavity (mouth/jaws/lips/tongue/teeth)
2. GI tract - Oesophagus, Stomach, SI, cecum, LI (colon), rectum, anus

2

Most important feeding structure of vertebrates?

Jaw

3

Define crown

Part of tooth visible above gum

4

Define dentin

mineralised substance

5

Define root

anchor

6

Define dental pulp

connective tissues, nerves & blood vessels

7

Define enamel

hard outer substance of tooth.
Inorganic crystals, irreplaceable

8

Dental formula of dog (upper & lower)?

3142
3143

9

Dental formula of sheep (upper & lower)?

0033
4033

10

Tongue properties...?

muscle mass covered in mucous membrane
stratified, squamous epithelium covered in papillae

11

Different forms of papillae?

filiform
fungiform
foliate
vallate
conical

12

Define prehension and structures involved

Act of getting food into mouth - lips, tongue

13

Define mastication

1st act of digestion
initiates mechanical breakdown
Motility of mouth enables slicing, tearing, grinding & mixing food

14

What does mastication stimulate?

Secretion of saliva, gastric juices, bile, pancreatic juices

15

Define deglutition

Swallowing - relaxed upper oesophageal sphincter & closed soft palate

16

Draw micro-anatomy of the SI

...

17

What are the 2 levels of control of the GIT?

Extrinsic - ANS
Intrinsic (enteric) - unique to GIT; nervous & endocrine components

18

T or F - ANS nerves form link with enteric NS

true

19

T or F - extrinsic nerves originate within the GIT

false - outside the GIT

20

ANS influences GIT motility how?

1. modifies ongoing activity thru intrinsic plexus
2. alters levels of GIT hormone secretion
3. Acts directly on SM & glands

21

Properties & functions of the oesophagus?

To push boluses of food from pharynx to stomach
Contains mucus -> prevents damage

22

Muscle type in dog & ruminant oesophagus

entirely striated

23

Muscle type in bird & human oesophagus

entirely smooth

24

Muscle type in horse, cat & pig oesophagus

striated at origin then to SM

25

Draw stomach & label

...

26

Learn and distinguish differences between GIT of ruminant & non-ruminant...

4 compartments vs 1 compartments
much greater number of bacteria to aid in digestion
See illustrations

27

List the structures in the horse large intestine

Caecum, ascending colon, transverse colon, descending colon, rectum

28

Name the accessory digestive organs

Salivary glands
Pancreas
Liver

29

Name the salivary glands

Parotid
Mandibular
Sublingual
Buccal

30

Endocrine portion of pancreas contains ... & secretes ...?

Islets of Langerhans & insulin/glucagon

31

Exocrine portion of pancreas contains ... & ... cells which secrete... & ...?

Acinar cells - digestive enzymes
Duct cells - sodium bicarb solution

32

Functions of the liver...?

Bile secretion
Metabolic processing
RBC breakdown
Waste elimination
Plasma protein synthesis
Secretion/modification of hormones/growth factors
Gluconeogenesis

33

Liver stores what?

glycogen, fat, iron, copper, vitamins

34

Know how to label structures of liver

... slide 47 & 48

35

Know components of the avian digestive tract

...slide 51 (lec objective)

36

Characteristics of motility?

Mixing ingested material with secretions
Peristalsis - circular muscle contracts & longitudinal muscle relaxes and vice versa
Rate of movement varies bwn feed/spp

37

Characteristics of secretion?

Release of useful substances in GIT lumen
Secretions: enzymes, buffers, bile, lubrication, solvent

38

Characteristics of digestion?

Breakdown into smaller molecules - mechanical/enzymatic
Aided by secretions

39

Characteristics of absorption?

nutrient uptake & use
uses specialised cells lining GIT lumen
passive or active

40

Segmentation (haustration) involves what?

Random, localised contraction of smooth muscle
Occurs in SI & colon
non-propulsive; instead mixes digesta

41

Most saliva secretion comes from where?

Parotid glands
mandibular glands
sublingual glands

42

2 types of saliva secretions?

viscous - mucous rich (small glands)
serous - (parotids)

43

Which salivary glands secrete both (viscous & serous) saliva?

madibular & sublingual

44

T or F - Starch digestion begins in mouth due to amylose

False - amylase

45

Amylase digestion is high, low and absent in which animals?

High - pigs
Low - horses
Absent - ruminants

46

T or F - saliva provides alkaline buffer & fluid bicarbonate in the rumen

True - very important for ruminant digestion

47

T or F - salive provides evaporative cooling and oral protection

true - oral protection is due to buffer, lysosomes & antibacterial properties

48

Salivary center in medulla is stimulated by which factors?

Pressure receptors & chemoreceptors (mouth)
Cerebral cortex (sight of food ->'mouthwatering')

49

Cascade of events to stimulate saliva secretion...?

Visual/chemo-/pressure cues -> + salivary center -> + ANS -> + salivary glands -> + saliva secretion

50

Mucous cells secretions & role?

Alkaline mucous & protect mucosa

51

Chief cells secretions & role?

pepsinogen & protein digestion

52

Parietal cells secretions & role (2 secretions)?

Hydrochloric acid & activates pepsinogen
Intrinsic factor & facilitates absorption of vit B12

53

Enterochromaffin like cells (ECL) secretions & role?

Histamine & stimulates parietal cells

54

G cells secretions & role?

Gastrin & stimulates parietal, chief & ECL cells

55

D cells secretions & role?

Somatostatin & Inhibits parietal, G & ECL cells

56

Pancreatic enzyme properties...?

Potent enzymatic secretions
Aqueous alkaline secretions
VERY important in non-ruminants
Synthesised as zymogens (inactive enzymes)

57

3 principle types of pancreatic enzymes?

proteolytic (protein catabolism)
amylase (starch catabolism)
lipase (fat catabolism)

58

Describe the control of pancreatic sodium bicarb secretion

+acid in duodenum -> + secretin release (mucosa) -> +secretion of bicarb (pancreatic duct cells) -> duodenal lumen -> neutralises acid in duodenum

59

Describe the control of pancreatic digestive enzyme secretion

Fats & proteins in duodenum -> +CCK (mucosa) -> + secretion digestive enzymes (acinar cells) -> digests fats & proteins

60

Bile...

Stored in gall bladder (not stored in horse)
Emulsifies fats

61

Know SI anatomy diagram on slide 22 (lec 2)

...

62

In the small intestine, what impairs digestion & absorption?

Loss of surface area (villous atrophy)

63

Why is physical breakdown of food important?

Reduces particle size
Enlarges surface area

64

Reduction of food particles occurs where?

stomach

65

Chemical digestion involves...?

Complex nutrients -> simple ones
Via hydrolysis

66

Chemical digestion of CHO breaks which bonds?

glycosidic linkages

67

Chemical digestion of proteins breaks which bonds?

peptide bonds

68

Chemical digestion of fats breaks which bonds?

ester bonds

69

Chemical digestion of nucleic acids breaks which bonds?

phosphodiester bonds

70

Describe luminal phase of monogastric digestion (non-fibrous CHO)

Dietary polysaccharides such as starch & glycogen broken down in GI lumen by salivary & pancreatic AMYLASE into maltose & sucrose.

71

Describe membraneous phase of monogastric digestion (non-fibrous CHO)

Maltose, sucrose & lactose -> monosaccharides by brush border enzymes -> glucose & galactose absorbed apical membrane by Na+ cotransport. Fructose by facilitated diffusion

72

Describe monogastric protein digestion & absorption (3 steps)

1. Dietary & endogenous protein ingested -> hydrolysed by pepsin & pancreatic proteolytic enzymes
2. AAs across apical membrane via Na+/K+ pump
3. Small peptides absorbed by different carrier -> AAs by aminopeptidases or intracellular peptidases

73

Consider drawing monogastric protein digestion (3 steps)

slide 27...

74

Consider drawing monogastric CHO digestion

slide 26...

75

Describe lipid digestion & absorption in monigatrics

1. TGs emulsified in SI by bile (duodenum)
2. Pancreatic lipases hydrolyse TGs -> monoglycerides & FFAs
3. Micelles formed by lipase & bile carry monoglycerides & FFAs -> luminal surface
4. Micelles release monoglycerides & FFAs near epithelial surface -> passive diffusion thru lipid bilayer

76

Consider drawing monogastric lipid digestion

slide 28...

77

Properties of large intestine...?

absorb water & electrolytes
microbial CHO & protein digestion
mucosal glands -> buffer & mucous

78

What does hind gut fermentation in horses produce?

VFAs = energy

79

Draw diagram of rumen and label compartments

slide 31-32...

80

Role(s) of the rumen...?

fermentation - anaerobic, pH, temp, removes indigestible material & products of digestion

81

Role of reticulum?

'Honeycomb' appearance - movement of material, fluid etc.

82

Role of omasum?

Spherical shape - laminae grind roughage & squeeze fluid out of ingesta

83

Role of abomasum?

True 'glandular' stomach - enzymatic digestion

84

2 main types of motility in the rumen?

Primary contractions - mixing
Secondary contractions - eructation of gas

85

T or F - regurgitation is not considered a motility pattern

true

86

3 main steps to ruminate...?

1. Regurgitate - rumen & reticulum contract -> recently eaten food away from oesophagus replacing it with semi-liquid partially fermented -> reverse peristalsis up oesophagus
2. Remasticate - only some matter ->reinsalivate
3. Reswallow

87

What is fermentation? Briefly describe...

Metabolic action of bacteria & other microorganisms
Microbial enzymes hydrolyse large molecules

88

What are the key features of ruminant & hindgut fermentation?

CHO most important E source
37 degrees
osmolality (ionic strength) optimum range
anaerobic (-ve red-ox potential)
removal of ingestible material
rate of microbial removal = microbial regeneration
VFAs buffered or removed

89

5 major groups of microbes?

Bacteria
Protozoa
Fungi
Archael (methanogens)
Bacteriophage

90

CHO digestion in the rumen...?

Microbial fermentation -> Acetate, Butyrate, Propionate

91

T or F - SCFA account for between 30 - 50% digestible E intake

False. 50 - 70%

92

Why is propionate important?

glucose production

93

Increased roughage -> ?

increased acetate

94

Protein digestion in the rumen...?

Proteins -> AAs -> microbial protein prod. & ammonia prod.
Can -> VFA prod.

95

Lipid digestion in the rumen...?

Microbes release extracellular lipases -> meat & milk products to become saturated