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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
What are the secretion in the small intestine stimulated by?
local reflexes
26
What are the secretion in the stomach stimulated by?
- autonomic nervous control - hormonal control - reflex mechanism
27
Explain the regulation of hunger. What are the stimulants of hunger? What actually is the main communicator?
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
28
What is injestion?
the entry of food in the digestive system
29
What are the 4 main aspects of digestion?
- injestion - mechanical and chemical breakdown - absorption - excretion
30
How does absorption occur? What is absorption?
The movement of nutrients from the **digestive system** to the **circulatory system** and **lymphatic system** (capillaries) through *osmosis*, *active transport* and *diffusion*.
31
What is egestion?
Removal of undigested materials from the digestive tract through defecation.
32
What are the main functions of the digestive system?
- feed intake and mechanical crushing - secretory - motility - breakdown of nutrients (hydrolysis) - reabsorption - excretion - protection - endocrinical - analytical
33
What are the 3 types of muscular movements in the GI tract?
- peristalsis - mixing - segmentation
34
What is peristalsis?
- wavelike movement that occurs from the pharynx to the reticulum - allows the GI tract to push food particles towards the anus
35
What is mixing? Where does it occur? What is its functon?
Function: - repeated breakdown of food into smaller particles using mechanical digestion. Location: - stomach - mouth
36
What is segmentation? Where does it occur? What is its functon?
Function: - allow a more efficient digestion and absorption Location: - regions of the small intestine (contract and relax independently)
37
What does the gastrointestinal tract consist of?
- oral cavity - pharynx - esophagus - stomach - small intestine - large intestine - anal canal
38
What are the accessory organs of the digestive system?
- teeth - tongue - glandular organs (salivary glands, liver, gallbladder, pancreas)
39
What occurs in the oral cavity?
- 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
What is prehension? What does it depend on?
- bringing of food to the mouth - mechanisms vary with behaviour and diet
41
Explain the species differences in the prehension of food.
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
How does drinking vary between species?
most mammals: sucking dogs and cats: use tongue to ladle
43
Explain mastication. What are the species differences? Where is mastication especially important?
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
What are the three large glands called?
- **parotid** gland - **mandibular** gland - **sublingual** gland
45
What is saliva? Where is it producted? What is it composed of?
saliva- secretion produced by salivary glands composition: - 50% *serous* secretion from **parotid** gland - other glands (mandibular and sublingual) secrete viscous, mucous rich saliva
46
What is the function of saliva?
- moisten food during mastication, - make food easier to swallow, - dissolve food components - enable food to be 'tasted'
47
What type of animals decrete most saliva?
herbivores
48
What is the composition of saliva adapted to?
the consistency of food
49
Explain the amounts of salivary secretion of different species.
dogs: 0.5l/day sheep: 3-10l/day horse: 10-12l/day cattle: 130-180l/day
50
Explain the composition of saliva.
99.5% water 0.5% dissolved substances (amylase, bicarbonate ion, electrolytes)
51
What is the function of amylase?
chemical digestion of carbohydrates
52
What is teh function of bicarbonate ions?
maintain salivary pH at 6.5-7.5
53
What is the pH of saliva?
pH 6.5-7.5
54
What are the functions of saliva?
- lubrication - antibacterial effect - enzymatic action - pH regulation - binding of tannins - provide urea for protein synthesis (in forestomachs) - thermoregulation
55
What form of regulation are salivary glands under?
AUTONOMIC NERVOUS SYSTEM: - sympathetic nerve fibers - parasympathetic nerve fibers
56
What does sympathetic stimulation result in?
- **decreased** production of **saliva** by acinar cells - **increased** **protein** secretion - **decreased blood flow** to the glands
57
What is the parasympathetic outflow coordinated by?
centers in the **medulla oblongata**
58
How does parasypathetic stimulation occur?
afferent information from the mouth, tongue, nose and conditioned reflexes
59
What does parasympathetic stimulation result in?
- **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
Explain the process of swallowing.
- 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
What system is the pharynx? What is its function?
system: digestive and respiratory function: - ensure that only food and water enters the esophagus - ensures that only air enters the trachea
62
What happens once the swallowing reflex is initiated?
Respiration is briefly halted and the epiglottis moves into a position that closes the entrance to the respiratory tract.
63
Explain the movement of food through the pharynx and upper esophagus during swallowing.
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
What is the esophagus?
Small muscle-lined tube extending from the pharynx to the stomach.
65
What is at the start and end of the esophagus?
muscle cells functioning as sphincters
66
What is teh esophagus wall composed of?
Muscles which undergo peristaltic movements
67
What is the stomach? What type of digestion takes place in the stomach?
- pouch like organ - designed for food storage (2-4h) - mechanical and chemical digestion
68
What is chyme?
the mixture of feed and digestive secretions in the lumen of the digestive tract.
69
What is the part of the stomach closest to the esophageal opening called? What does it not have?
esophageal portion - no glands
70
What two sphincters does the stomach contain? What are their functions?
esophagus --> **cardiac (esophageal) sphincter** **pyloric sphincter** --> small intestine - regulate the movement of food
71
What are the parts of the stomach? How many parts is the glandular stomach divided into?
4 parts: - cardiac stomach - fundic stomach - body of the stomach - pyloric stomach
72
What is the pH of the stomach? Why?
low pH - digestion of protein - denatures food
73
In what glands are most gastric juices produced?
glands of the: - fundus - corpus
74
What 4 cell types does teh stomach mucosa contain?
- chief cells - parietal cells - mucin-producing cells - endocrine cells
75
What do chief cells secrete?
pepsinogen
76
What do parietal cells secrete?
- hydrochloric acid - intrinsic factor (glycoprotein)
77
What is the function of the intrinsic factor secreted by parietal cells?
- absorption of vitamin B12 in teh intestines
78
What is the function of mucin-producing cells?
secrete: - mucous - alkaline substances (neutralize HCL in gastric juice)
79
What is the function of endocrine cells? G-cells? ECL-cells? D-cells?
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
What are the functions of HCL secretion in the stomach?
- 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
What 3 types of digestion take place in the stomach? By what type of enzymes?
- amylase: carbohydrates --> disaccharides - pepsin: protein--> peptides - lipase: lipid-->fatty acids
82
What substance does the mixing of food with digestive enzymes result in?
chyme, yellowish paste
83
What are gastric secretions regulated by? Explain.
- 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
What are the 3 phases of gastric secretion regulation?
1) cephalic phase 2) gastric phase 3) intestinal phase
85
Explain the cephalic phase.
- 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
Explain the gastric phase.
- 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
When is gastrin secretion inhibited?
when pH of gastric juice falls below 2.5
88
What type of stimulation is acetylcholine?
parasympathetic
89
Explain the intestinal phase.
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
Where does the enterogastric reflex take place?
small intestine (entero) --> gastric (stomach)
91
Explain the rabbit stomach.
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
Explain the digestion in birds.
crop: - moistens food proventriculus: - provides digestive secretions (HCl and proteolytic enzymes) ventriculus/gizzard: - grinds food

Physiology S2 (17 decks)

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