Digestion I Flashcards by Grace Harrison

what are the 6 main components of the gastro inter-stinal tract (GIT)

1) mouth
2) Pharynx
3) Oesophagus
4) Stomach
5) Small and large intestine
6) Rectum and Anus

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what are the 6 main accessory organs to the GIT

1) tongue
2) teeth
3) 3 pairs salivary glands
4) liver
5) gall bladder
6) Pancreas

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what are the 3 pairs of salivary glands

1) parotid
2) submandibular
3) sublingual

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the pancreas is two things, what are they

both endocrine an exocrine gland

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structures of the GIT from oesphagus-anus all have the same tissue arrangement. what are the 4 main components:

1) mucosa
2) submucosa
3) muscularis (circular/longitudinal)
4) serosa

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the mucosa has four main parts. what are they

1) inner lining has mucous membrane
2) epithelial layer
3) connective tissue layer
4) muscularis mucosae

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what is the mucous membrane of the mucosa in direct contact with

food contents

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what does the epithelial layer of the mucosa do

secretes enzymes and absorbs digested food

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what is the purpose of the connective tissue layer in the mucosa

houses blood vessels and lymphatics

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what does the muscularis mucosae contain

smooth muscle fibres which throws membranes into folds so increasing potential surface area for digestion

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3 points about the submucosa

1) connective tissue which binds mucosa to muscularis
2) has a rich blood supply
3) houses part of the autonomic nervous system which controls secretion from GIT

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4 points about the muscularis

1) smooth muscle found in 2 sheets
2) inner circular fibres, outer longitudinal fibres
3) these muscles serve to physically break down food and push it through the GIT
4) has nerve supply which controls motility

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serous membrane has two main components. what are they?

connective tissue layer and epithelial layer

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what does the serosa form

the inner layer of peritoneum called Visceral-Peritoneum

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what is the outer layer of peritoneum called (serosa)

parietal peritoneum

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what is the function of the peritoneum in the serosa

weaves between structures of the abdomen binding them together & housing blood lymphatic and nervous supply

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what 4 things form the oral cavity

1) cheeks
2) lips
3) gums
4) teeth

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the upper portion is formed by

the hard palate anteriorly and the soft palette posteriorly

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what is the uvula and what happens during swallowing to it

part of the soft palate and it will be drawn superiorly during swallowing to prevent food from entering the nasal cavity

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what is mastication

where the tongue, teeth and hard palate work together to begin the initial breakdown of food

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what do salivary glands begin

the chemical breakdown within the oral cavity

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where is saliva secreted from

the sublingual glands under the tongue, the submandibular glands found posteriorly beneath the base of the tongue and the parotid glands (which secrete via parotid duct to an area near the upper molars)

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what happens to food when swallowed

swallowed from the oral cavity and passes through the oral pharynx on route to the oesophagus

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what is the job of the epiglottis

prevents food entering the trachea during deglutiniation which is the swallowing action

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what 5 things does saliva contain

1) salivary amylase 2) mucus 3) water 4) bacteriolytic enzyme called lysozyme 5) immunoglobin

what is the job of salivary amylase

acts on starch

what does mucus do

lubricates the food

what does the water in saliva do

helps to dissolve food, allowing taste and early digestive reaction

what is the function of lysozymes in the saliva

kill bacteria and help protect mucous membrane

what is the job of immunoglobin in saliva

prevent attachment of microbes which may attack epithelium

what two complex glucose chains is starch found in most carbohydrates made of

polysaccharides and disaccharides

what will our blood stream only absorb

monosaccharides so the salivary amylase begins the breakdown of such chains

lingual glangs in the mouth secrete

lingual lipase

what is stimulated within the acidic environment of the stomach

lingual lipase

what does lingual lipase begin the breakdown of

triglycerides into diglycerides in the process of fat breakdown

what is the oesophagus

muscular collapsible tube behind the trachea

how does the oesophagus propel food to the stomach

by muscular contractions of the circular and longitudinal layers of the muscularis

what are the two main jobs of the oesophagus

1) secretes mucus | 2) transport food to the stomach

does chemical digestion or absorption take place in the oesophagus

what do the circular fibres above the bolus of food do in the oesophagus

constrict to push the food downwards

where are the longitudinal fibres in the oesophagus found in relation to the bolus

inferiorly

what do the longitudinal fibres do

shorten and allow the muscular walls of the oesophagus to be pushed outwards and accept the bolus

what is the name of the involuntary movement controlled by the medulla oblongata in the brain called

peristalsis

where is the cardiac sphincter found

at the lower end of the oesophagus

what does the cardiac sphincter do

open to allow food to enter the stomach

what does the cardiac sphincter prevent

hydrochloric acid within the stomach refluxing into the oesophagus. This is necessary as the acid is harmful to the lining of the lower end of the oesophagus

if there is a malfunction with the sphincter the patient will present with what condition

oesophageal reflux

what two things relax the sphincter which can worsen the problem of oesophageal reflux

smoking and alcohol

what are the 6 main parts of the stomach

1) cardia 2) fundus 3) body 4) pylorus 5) lesser curvature 6) greater curvature

what does the cardia do

surrounds lower oesophageal sphincter

where is the fundus

above and to the left of the cardia

what is the body of the stomach

large central portion

what does the lesser curvature do

concave medially

what does the greater curvature do

convex laterally

how does the inner lining mucosa in the stomach lie

in folds called rugae and contains gastric glands which secrete digestive enzymes and intrinsic factor

what are the three types of fibre that make up the muscularis in the stomach

1) outer longitudinal 2) middle circular 3) inner oblique fibres

what do gastric juices mix the food into

a chyme

what does the stomach absorb

water, drugs and alcohol only

what do the peristaltic waves in the stomach do

move the food round to enable mixing with gastric juices and pushing the food eventually towards the pylorus and on into the duodenum

why does food remain in the fundus for approx 1 hour

so amylase and lingual lipase continues breakdown of starch an fat

HCl in the stomach causes partial breakdown of

proteins

what does HCl stimulate

the release of hormones to stimulate bile released at a later stage of digestion

where is pepsin released and what does it do

within the stomach and breaks down the peptide bonds within the amino acids which make up proteins

what conditions does pepsin work well in

an acidic environment

what does the stomach lining produce to protect pepsin from acid damage

mucous secretions

what does gastric lipase do

splits triglyceride chains and so continues the breakdown of fats

what is the diameter and length of the small intestine

``` diameter= 2.5cm length= 6.35 metres long ```

what 3things does the small intestine consist of

1) duodenum (25cm) 2) jejunum (2.5 m) 3) ileum (3.6m)

where does the small intestine open

at pyloric sphincter from the stomach

where does the small intestine curve around

the head of the pancreas

what is the small intestine in close proximity to

the liver and gall bladder

where does the small intestine finish

ileo-caecal valve where it becomes the large intestine

where does the pancreas lie

posterior to greater curvature of the stomach

where is the pancreatic juice released

through the pancreatic duct and enters the duodenum through the sphincter of Oddi at the ampulla of Vater (hepato-pancreatic ampulla). this is the exocrine function of the pancreas

what does the pancreas contain and why

sodium bicarbonate which neutralises acid and stops the action of amylase. It also created optimum conditions for the small intestine enzymes to work

what 4 things does the pancreatic juice contain

1) pancreatic amylase 2) trypsin 3) pancreatic lipase 4) nucleic acid

what does pancreatic amylase do

digest carbohydrates

what is trypsin

protein digesting enzyme

when does trypsin become active

when it mixes with enterokinase as it enters the small intestine

what is pancreatic lipase

principal triglyceride digesting enzyme

what is nucleic acid digested by

ribonuclease and deoxyribonuclease

what does the liver produce

bile which contains sodium and potassium salts

what do the salts in bile do

emulsify lipids within fat to form globules which can be broken down further by the pancreatic lipase

where does bile drain

through the right and left hepatic ducts into the common hepatic duct

how does bile pass into the small intestine

through the common bile duct

what happens to the sphincter during meals

closes over and bile is stored in the gall bladder as it cannot enter the intestine