Lecture 18- Digestion 1 Flashcards Preview

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1

Describe the anatomy of the digestive system:

-

2

Describe the muscle bit of the digestive tract wall?

-two layers of smooth muscle, in different orientations inner= circular so contraction = decrease in diameter or increase if relaxed outer= longitudinal= shorten or lengthen the tube = that's how we get movement in the digestive tract moving things inside= shortening and changing diameter

3

Describe the layers in the digestive tract wall? (part 2)

mesentry=connected to serosa= aslso to the body wall= prevents the tubes from tangling --way the nerves and blood vessels can access the intestines serosa=outer layer, continuos with mesentry, rich with lymphatic cells and covers the entire thing submucosa=glands in there

4

What is peritonisis?

peritonisis= inflamation of the peritonium, but typically it is also of serosa

5

What is the Autonomous smooth muscle function in the digestive system?

-GIT motility=Propels food from mouth to anus =Mechanically mixes & breaks down food -GIT contains layers of single unit smooth muscle fibres =Specific cells noncontractile maintain oscillating resting potentials=drive the regular cycling behaviour of the cycling contractions of the gut -slow wave activity= below threshold then hit threshold= lot of activity -the strength of contraction depends on how many AP

6

What are the systems regulating digestion in general?

-Local changes in digestive tract leads to a response from Receptors in digestive tract

7

What is the enteric nervous system, what does it use to control the digestive system?

enteric nervous system= ENS= one big subdivision of the autonomic nervous system -sensory afferent neurons -interneurons -motor (efferent) neurons = =Stimulatory neurons,mainly cholinergic ie acetylcholine = Inhibitory neurons - neurotransmitters eg nitric oxide, vasoactive intestinal peptide=also effects on blood flow

8

What are the extrinsic nerves involved in the regulation of the digestive system?

-nerve from the brain or spinal chord -part of the autonomic nervous system -both Parasympathetic (mainly vagus nerve) and Sympathetic =their main role is to modify enteric nervous system -modifying activity, even without its input the digestive system works well (during sleep etc)

9

What are the three things involved in digestion in the mouth?

-prehension= getting the food to the mouth(hands for us) -mastication= chewing=mechanical breakdown -saliva= contains amylase =no nutrition absorption here! only processing

10

What secretes saliva?

-sublingual -submandibular -and parotid glands

11

How much saliva do ruminants produce per day?

-100-200 liters

12

What is the difference in saliva contents in ruminants and monogastrics?

-Monogastrics (Low [NaCl], low [HCO3-]) -Ruminant (High [HCO3-] & [PO4-] =ruminants= the components important for what happens in the stomach

13

What is the deal with amylase?

-some species have it and some don't have it, the ones who eat more starch more likely to have it

14

What is lingual lipase?

-break down fat=thought to help cats determine the nature of the food -medium-chained fats in cats

15

What is the composition of a tooth?

-enamel, dentin, cementum -no cells within the hard tooth structure (no living cells)unlike bones enamel= sharp and hard crystals= tough edge brittle dentin= more flexible cementum= protective layer

16

What is the difference between a homodont and a heterodont?

homodont= just one type of teeth heterodont= more types =incisors, canine, premolar, molar =incisors= cutting, prehension(grasping) canine= fighting, tearing premolar and molar= solid big teeth, crunching breaking bones and grass(shearing)

17

What is an elodont and an anelodont?

elodont= continue growing )rabbits= continues to grow if not enough chewing in horses huge root= so continues coming out anelodont= limited period of growth

18

What is a brachydont and a hypsodont?

brachydont=Short crown (dogs /cats)=brachydont= short crown= crunching hypsodont= continual eruption, seen in herbivores

19

What is a Diphyodont / polyphyodont?

diphydont= have disiduous teeth 2 polyphyodont: more than two sets of teeth

20

What are ruminant teeth like?

-ruminants= only upper incisors and down= a plate, hold onto food by action of head

21

In which animals is amylase and in which it isn't?

-Present in ominvores eg pig, rat, human - Absent in carnivores eg dog, cat - Absent in some herbivores eg sheep

22

What does amylase do?

-amylase starts the process of breakdown (ominvores= usually have amylase) herbivores have different system as they also need to break them down

23

What can stimulate salivation?

-pressure receptors and chemoreceptors in the mouth=when food is in the mouth -cerebral cortex -also the Conditioned reflex(remember pavlov= salivating with the bell = conditioned reflex= anticipation of food) =all these stimulate the Salivary center in medulla which via autonomic nerves stimulates salivary glands= salivation!

24

What is swallowing?

-also called deglutition -it is sequentially programmed=all-or-nothing reflex(can't do half a swallow, all or nothing can't stop once started) -Respiratory centres are inhibited during swallowing

25

What are the three phases of swallowing?

-Buccal=back of oral cavity stimulated -Pharyngeal=pharyx modifies itself to allow the material to roll back -Oesophageal= opens so it can go into the oesophagus

26

What is reverse peristalsis?

bringing food back into the mouth cats and dogs= it comes up if unhappy with the food, useful ruminants= different role, the ability to chew the fibrous material to smaller bits again horses= don't have either do have to be careful

27

What is the purpose of the stomach?

storage, regulates the amount coming into the small intestine (duodendum)

28

Describe the anatomy of the stomach:

phyloric sphincter=held shut most of the time controls how much gets in

29

What are the four stages of stomach motility and where does it take place in the stomach?

-Gastric filling=Plasticity and Receptive relaxation(similar to the bladder, increase in volume without increasing the tension too much) -Gastric storage= Body & fundus region of stomach, Less smooth muscle -Gastric mixing=further down,continual movement of the posterior part of the stomach -Gastric emptying=via the phyloric sphincter

30

How big is the stomach in monogastrics?

-In monogastrics from 50ml to 10L (horse) -not large in comparison to th eanimal. can expand in cats and dogs, lot of plasticity but stomach has a limit= if reached can rupture