Digestion - organised disassembly and absorption

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  • Created by: Alex
  • Created on: 02-06-13 12:25
role of oesphagus
transit
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role of stomach
storage, milling and acid/peptic digestion
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role of S.intestine
fat, protein & carbohydrate digestion and absorption. water and electrolyte transport. bile salt transport
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Role of large intestine
storage and water reabsorption
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role of anus and rectum
defaceation
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role of the mouth
apprehension, mechanical chewing, chemical (salivary amylase) breakdown
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whats mastication?
chewing - rhythmic action to break up food into smaller particles
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role of saliva
moistens food to make it easier to swallow - also contains amylase, some- anticoagulant, poison, thermoregulation, anti-bacterial
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whats deglutition?
propulsion of chewed material into the oesophagus
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is chewing automatic or willed?
automatic act initiated by a willed decision - controlled by neural 'pattern generator' in brain stem
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what does chewing do?
grind and break food to help swallowing, mix food with saliva, stimulates the taste buds - increase saliva, gastric, pancreatic and bile secretions
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Constituents of saliva
water(99.5%), Ions, mucus, alpha amylase, lysozyme
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3 glands saliva is secreted fomr
the parotid, sublingual and submaxillary
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How much saliva is secreted daily?
1-2L
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How many times do we chew food
33
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whats bolus
Lump of chewed fod
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what happens when bolus is pushed to the back of the mouth
initiates reflex involvin 25 skeletal muscles - propel bolus into oesophagus where it is then moved by peristalasis
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what guards oesophagus at the bottom?
gastroesophageal - prevents back flow/heart burn
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what stops us inhaling food?
epiglottis (small flap of tissue) closes the opening to the airway
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stomach:
muscular region of the digestive tract - extends from the oesophagus to the small intestine
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chemical digestion
bathes material in strong acid medium and attacks proteins with pepsin -chief cells in gastric glands secrete pepsinogen
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Mechanical digestion
mixing turns material into chyme
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What is gastric uice made of?
water, HCl, Pepsinogen, Intrinsic factor and Mucous
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what do parietal cells secrete?
HCl
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What secretes pepsinogen?
Chief cells
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what controls gastric secretion?
Stimulus - food arriving in stomach Activates parasympathetic nerves & hormones are released
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how is the stomach protected against acids?
protective stomach mucus - alkaline, lubricates gastric mucosa, prevents self digestion. Luminal membranes impermeable to H+ so acid can't penetrate and damage. cardiac cells secrete bicarbonate. lining replaced regulary 3-4 days
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where are fats digested ?
in the small intestine onlt
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pylorus
s the region of the stomach that connects to the duodenum (the beginning of the small intestine
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Parts of the rumen
reticulum, omasum and abomasum
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role of the rumen
fermentation chamber
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where do you find lightweight low density material in the rumen?
top - straw needs longer to digest
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where do you find medium density material in the rumen?
sinks to the bottom
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where do you find high density material in the rumen?
sinks into the cranial sac - e.g. grains
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motor activity of the rumen
mixes contents, propels digested material into the omasum, removes gaseous products of fermentation, initiates rumination
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what is rumination?
chewing of cud - regurgitation, re-salivation, re-mastication, re-deglutition
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when does rumination occur?
following special A-cycle - triple contraction of reticulum propelling material into the esophagus
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B cycle
contraction and shifting inside means gas bubble moves over cardia allowing gas to escape
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Other cards in this set

Card 2

Front

role of stomach

Back

storage, milling and acid/peptic digestion

Card 3

Front

role of S.intestine

Back

Preview of the front of card 3

Card 4

Front

Role of large intestine

Back

Preview of the front of card 4

Card 5

Front

role of anus and rectum

Back

Preview of the front of card 5
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