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Physiology S2 > Test 1: Mouth and Stomach > Flashcards

Test 1: Mouth and Stomach Flashcards

1
Q

What is digestion?

A

The breakdown of large insoluble food compounds into smaller water-soluble components so that they can be absorved into the blood plasma.

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2
Q

What is another word for digestion?

A

catabolism

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3
Q

What are the two types of digestion? Where do they occur? What do they involve?

A

1) MECHANICAL digestion:
- mouth
- physical breakdown

2) CHEMICAL digestion:
- gastrointestinal tract
- chemical breakdown by digestive enzymes

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4
Q

What is mastication? What other secretion is present? What does it begin to digest?

A

The process of chewing of food in mammals.
- saliva contains amylase
- begins the digestion of starch

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5
Q

What are the main components of gastric juices?

A
  • pepsin
  • hydrochloric acid
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6
Q

What is the main function of the liver? Where is it stored? Where is it secreted?

A

Produce bile.
Stored in the gall bladder.
Secreted into the small intestine.

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7
Q

What is the function of the pancreas?

A

Secrete pancreatic juices that aid in digestion and absorption of nutrients.

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8
Q

What is the process called which describes the loss of fecal material from the rectum?

A

defacation

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9
Q

What are the three classifications of animals based on their food habits?

A

HERBIVORES: eat only plant material
OMNIVORES: eat both plants and animals
CARNIVORES: eat only animal material

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10
Q

What does the digestive system depend on?

A

Numerous structural and functional adaptations of animals diets, habitats and other physiological characteristics.

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11
Q

What regulates the digestive process?

A
  • autonomic nervous system
  • hormonal control
  • reflex mechanism
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12
Q

Explain the regulation of the DS by the autonomic nervous system. What do parasympathetic nerves do? What do sympathetic nerves do?

A

Parasympathetic nerves stimulate gastrointestinal tract activities.

Sympathetic nerves inhibit gastrointestinal tract activities.

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13
Q

Explain the regulation of the DS by hormonal control.

A

Hormones from:
- the endocrine gland
- GI tract
help regulate the GI tract activities.

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14
Q

Explain the regulation of the DS by the reflex mechanism. Which organs in particular use this form of regulation?

A

Regions of the GI tract (especially stomach and small intestine) use reflexes to stimulate or inhibit one another.

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15
Q

What type of reflexes provide the digestive tract with extensive self control?

A

short reflexes

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16
Q

What type of effects do short reflexes have on the digestive process?

A

short=stimulatory effects

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17
Q

What are inhibitory short reflexes important for?

A

relaxation of the GI sphincters

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18
Q

What reflexes do distant parts of the digestive tract communicate with each other with?

A

enteroentric reflexes

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19
Q

What is the location of short reflexes?

A

fully contained within the walls of the digestive tract.

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20
Q

What is the location of long reflexes?

A

May originate within, as well as outside, of the digestive tract.

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21
Q

What do long reflexes involve?

A

long neural pathway b/w:
- central nervous system
- walls of the digestive tract

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22
Q

What hormone is produced in the stomach? What part of the stomach? What is its function?

A

Hormone:
- Gastrin

Location:
- distal stomach

Function:
- stimulates acid secretion from stomach glands
- stimulates gastric motility and growth of the stomach epithelium

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23
Q

What hormones, except of gastrin, has a function in the stomach? What do they do?

A

CCK’s:
- inhibits gastric emptying

GIP (Gastric Inhibitory Polypeptide):
- inhibits gastric motility and secretion activity

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24
Q

What are the secretion in the mouth stimulated by?

A

autonomic nervous system

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25
Q

What are the secretion in the small intestine stimulated by?

A

local reflexes

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26
Q

What are the secretion in the stomach stimulated by?

A
  • autonomic nervous control
  • hormonal control
  • reflex mechanism
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27
Q

Explain the regulation of hunger. What are the stimulants of hunger? What actually is the main communicator?

A

3 forms of ‘hunger feeling’:
- cerebral cortex
- “hungry blood” (decrease of glucose, amino acids and other nutrients in blood)
- empty stomach motility irrigates gastric mucosa mechanoreceptors

Main communicator:
- hypothalamus (arcuate nucleus)
- apetite center
- satiety center

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28
Q

What is injestion?

A

the entry of food in the digestive system

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29
Q

What are the 4 main aspects of digestion?

A
  • injestion
  • mechanical and chemical breakdown
  • absorption
  • excretion
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30
Q

How does absorption occur? What is absorption?

A

The movement of nutrients from the digestive system to the circulatory system and lymphatic system (capillaries) through osmosis, active transport and diffusion.

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31
Q

What is egestion?

A

Removal of undigested materials from the digestive tract through defecation.

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32
Q

What are the main functions of the digestive system?

A
  • feed intake and mechanical crushing
  • secretory
  • motility
  • breakdown of nutrients (hydrolysis)
  • reabsorption
  • excretion
  • protection
  • endocrinical
  • analytical
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33
Q

What are the 3 types of muscular movements in the GI tract?

A
  • peristalsis
  • mixing
  • segmentation
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34
Q

What is peristalsis?

A
  • wavelike movement that occurs from the pharynx to the reticulum
  • allows the GI tract to push food particles towards the anus
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35
Q

What is mixing? Where does it occur? What is its functon?

A

Function:
- repeated breakdown of food into smaller particles using mechanical digestion.

Location:
- stomach
- mouth

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36
Q

What is segmentation? Where does it occur? What is its functon?

A

Function:
- allow a more efficient digestion and absorption

Location:
- regions of the small intestine (contract and relax independently)

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37
Q

What does the gastrointestinal tract consist of?

A
  • oral cavity
  • pharynx
  • esophagus
  • stomach
  • small intestine
  • large intestine
  • anal canal
38
Q

What are the accessory organs of the digestive system?

A
  • teeth
  • tongue
  • glandular organs (salivary glands, liver, gallbladder, pancreas)
39
Q

What occurs in the oral cavity?

A
  • mechanical processing of food (teeth, tongue and palatal surfaces)
  • lubrication of food (mixing with salivary gland secretions) (preparing for transport through teh pharynx and esophagus)
  • initiation of teh swallowing reflex
40
Q

What is prehension? What does it depend on?

A
  • bringing of food to the mouth
  • mechanisms vary with behaviour and diet
41
Q

Explain the species differences in the prehension of food.

A

domestic animals: lips, teeth, tongue
cows: longue rough tongue
pigs: snout to root in ground, pointed lower lip to covey feed into mouth

birds: beak and tongue

42
Q

How does drinking vary between species?

A

most mammals: sucking
dogs and cats: use tongue to ladle

43
Q

Explain mastication. What are the species differences? Where is mastication especially important?

A

mastication/chewing:
- crushing food
- increasing food surface area (allowing enzymes to act on a greater surface)

especially important: non-ruminant herbivores

carnivores: reduce size to swallow
herbivores: chew continuously to increase the surface area

44
Q

What are the three large glands called?

A
  • parotid gland
  • mandibular gland
  • sublingual gland
45
Q

What is saliva? Where is it producted? What is it composed of?

A

saliva- secretion produced by salivary glands

composition:
- 50% serous secretion from parotid gland
- other glands (mandibular and sublingual) secrete viscous, mucous rich saliva

46
Q

What is the function of saliva?

A
  • moisten food during mastication,
  • make food easier to swallow,
  • dissolve food components
  • enable food to be ‘tasted’
47
Q

What type of animals decrete most saliva?

A

herbivores

48
Q

What is the composition of saliva adapted to?

A

the consistency of food

49
Q

Explain the amounts of salivary secretion of different species.

A

dogs: 0.5l/day
sheep: 3-10l/day
horse: 10-12l/day
cattle: 130-180l/day

50
Q

Explain the composition of saliva.

A

99.5% water
0.5% dissolved substances (amylase, bicarbonate ion, electrolytes)

51
Q

What is the function of amylase?

A

chemical digestion of carbohydrates

52
Q

What is teh function of bicarbonate ions?

A

maintain salivary pH at 6.5-7.5

53
Q

What is the pH of saliva?

A

pH 6.5-7.5

54
Q

What are the functions of saliva?

A
  • lubrication
  • antibacterial effect
  • enzymatic action
  • pH regulation
  • binding of tannins
  • provide urea for protein synthesis (in forestomachs)
  • thermoregulation
55
Q

What form of regulation are salivary glands under?

A

AUTONOMIC NERVOUS SYSTEM:
- sympathetic nerve fibers
- parasympathetic nerve fibers

56
Q

What does sympathetic stimulation result in?

A
  • decreased production of saliva by acinar cells
  • increased protein secretion
  • decreased blood flow to the glands
57
Q

What is the parasympathetic outflow coordinated by?

A

centers in the medulla oblongata

58
Q

How does parasypathetic stimulation occur?

A

afferent information from the mouth, tongue, nose and conditioned reflexes

59
Q

What does parasympathetic stimulation result in?

A
  • increased salivary secretion by acinar cells
  • increased HCO3- secretion (duct cells)
  • increased blood flow to salivary glands
  • contraction of myoepithelium to increase the rate of expulsion of saliva
60
Q

Explain the process of swallowing.

A
  • voluntary action –> involuntary action
  • tongue moves to the back of the mouth
  • soft palate seals of the nasal cavity
  • larynx is elevated
  • epiglottis is pushed against the glottis (keeps food out of the respiratory tract)
61
Q

What system is the pharynx? What is its function?

A

system: digestive and respiratory

function:
- ensure that only food and water enters the esophagus
- ensures that only air enters the trachea

62
Q

What happens once the swallowing reflex is initiated?

A

Respiration is briefly halted and the epiglottis moves into a position that closes the entrance to the respiratory tract.

63
Q

Explain the movement of food through the pharynx and upper esophagus during swallowing.

A

food reaches pharynx:
- epiglottis moves back (covers the entrance to the trachea)
- upper sphincter of the esophagus opens

food passes into esophagus:
- trachea entrance is reopened
- upper esophageal sphincter contracts

food is transported by peristaltic movement

64
Q

What is the esophagus?

A

Small muscle-lined tube extending from the pharynx to the stomach.

65
Q

What is at the start and end of the esophagus?

A

muscle cells functioning as sphincters

66
Q

What is teh esophagus wall composed of?

A

Muscles which undergo peristaltic movements

67
Q

What is the stomach? What type of digestion takes place in the stomach?

A
  • pouch like organ
  • designed for food storage (2-4h)
  • mechanical and chemical digestion
68
Q

What is chyme?

A

the mixture of feed and digestive secretions in the lumen of the digestive tract.

69
Q

What is the part of the stomach closest to the esophageal opening called? What does it not have?

A

esophageal portion
- no glands

70
Q

What two sphincters does the stomach contain? What are their functions?

A

esophagus –> cardiac (esophageal) sphincter
pyloric sphincter –> small intestine

  • regulate the movement of food
71
Q

What are the parts of the stomach? How many parts is the glandular stomach divided into?

A

4 parts:
- cardiac stomach
- fundic stomach
- body of the stomach
- pyloric stomach

72
Q

What is the pH of the stomach? Why?

A

low pH
- digestion of protein
- denatures food

73
Q

In what glands are most gastric juices produced?

A

glands of the:
- fundus
- corpus

74
Q

What 4 cell types does teh stomach mucosa contain?

A
  • chief cells
  • parietal cells
  • mucin-producing cells
  • endocrine cells
75
Q

What do chief cells secrete?

A

pepsinogen

76
Q

What do parietal cells secrete?

A
  • hydrochloric acid
  • intrinsic factor (glycoprotein)
77
Q

What is the function of the intrinsic factor secreted by parietal cells?

A
  • absorption of vitamin B12 in teh intestines
78
Q

What is the function of mucin-producing cells?

A

secrete:
- mucous
- alkaline substances (neutralize HCL in gastric juice)

79
Q

What is the function of endocrine cells? G-cells? ECL-cells? D-cells?

A

G-cells: gastrin (stimulates parietal cells and gastric secretion)

ECL-cells: histamine (stimulates HCL secretion)

D-cells: somastostatin (reduces the production of HCL; inhibits G-cells)

80
Q

What are the functions of HCL secretion in the stomach?

A
  • lowers pH= 1-3
  • transforms pepsinogen–> pepsin
  • acidifies stomach content
  • degrades connective tissue and muscle tissue
  • affects protein structure
  • kills microorganisms that enter the stomach with food
81
Q

What 3 types of digestion take place in the stomach? By what type of enzymes?

A
  • amylase: carbohydrates –> disaccharides
  • pepsin: protein–> peptides
  • lipase: lipid–>fatty acids
82
Q

What substance does the mixing of food with digestive enzymes result in?

A

chyme, yellowish paste

83
Q

What are gastric secretions regulated by? Explain.

A
  • autonomic nervous system
  • hormonal mechanism

FOOD ENTERS ESOPHAGUS:
parasympathetic nerves activate gastric hormone (G-cells) –> positive feedback

FOOD EXITS STOMACH:
sympathetic nerves inhibit gastric gland secretions by intestinal gastrin (released by the small intetsine)

84
Q

What are the 3 phases of gastric secretion regulation?

A

1) cephalic phase
2) gastric phase
3) intestinal phase

85
Q

Explain the cephalic phase.

A
  • sepcial senses detect food
  • parasympathetic nerves in the vagus nerve stimulate gastric activities
  1. sight, smell, taste of food causes the stimulation of the vagus nuceli in the brain
  2. vagus acid secretion:
    - parietal cells stimulated (major effect)
    - gastric secretions (lesser effect)
86
Q

Explain the gastric phase.

A
  • distention of stomach, stretch-receptors
  • stimulation by vagus nerve
  • vagus nerve stimulates acid secretion
  • chemo-receptors (amino acids and peptides stimulate acid secretion)
  • gastrin (parietal cells) and histamine (HCL)
  • acetylcholine (parasympathetic stimulation) stimulates HCL secretion
87
Q

When is gastrin secretion inhibited?

A

when pH of gastric juice falls below 2.5

88
Q

What type of stimulation is acetylcholine?

A

parasympathetic

89
Q

Explain the intestinal phase.

A

INHIBITION HCL SECRETION:
- CCK (cholecystokinin)
- GIP (gastric inhibiting peptide)
- secretin

  • released from duodenal epithelium

duodenum fills with chyme
-** sensory stretch receptors** are stimulated
- sensory nerve impulses travel to the CNS
- CNS –> vagus nerve –> inhibit peristalsis in the stomach wall

90
Q

Where does the enterogastric reflex take place?

A

small intestine (entero) –> gastric (stomach)

91
Q

Explain the rabbit stomach.

A

injested food: pyloric part (containing digestive enzymes)

reinjested fecal pallates: large fundus, remain seperate from food + fermentation continues

well developed cardiac and pyloric sphincters:
- vomiting is not characteristic of rabbits

92
Q

Explain the digestion in birds.

A

crop:
- moistens food

proventriculus:
- provides digestive secretions (HCl and proteolytic enzymes)

ventriculus/gizzard:
- grinds food

Physiology S2 (17 decks)

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