digestion Flashcards
define ingestion
the taking of substance, eg. food and drink, into the body though the mouth
define mechanical digestion
the breakdown of food into smaller pieces without chemical change to the food molecules
define chemical digestion
the breakdown of large, insoluble molecules into small soluble molecules
define absorption
the movement of small food molecules and ions through the wall of the intestine into the blood
define assimilation
the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
define egestion
the passing out of food that has not been digested or absorbed, as faeces, through the anus
cholera is a disease caused by ___
bacterium
diarrhoea is treated using ___
oral rehydration therapy
what does cholera bacterium do
produces a toxin that causes secretion of chloride ions into the small intestine -> reduces water potential in small intestine
- > causing osmotic movement of water into the gut, causing diarrhoea
- > dehydration and loss of salts from blood
amylase function
secreted by alimentary canal and breaks down starch into maltose
• maltose is broken down by maltase to glucose on the membranes of the epithelium lining the small intestine
breaks down large INSOLUBLE STARCH molecules to smaller more SOLUBLE disaccharide maltose
protease function
breaks down protein to amino acids
lipase function
breaks down fats to fatty acids and glycerol
(brief) what are the functions of HCl in gastric juice
low pH
- denatures enzymes in harmful microorganisms in food
- gives optimum pH for pepsin activity
(brief) role of bile
- neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action
- emulsifies fats to increase the surface area for the chemical digestion of fat to fatty acids and glycerol by lipase
water is absorbed in the ___ and the ____ but most of the absorption of water happens in the ______
water is absorbed in the small intestine and the colon but most of the absorption of water happens in the small intestine
the alimentary canal is ———-
a long tube running through the body from the mouth to the anus
(role in digestive system) mouth
food is mixed with saliva and chewed to break it into smaller pieces which are easier to swallow and digest
(role in digestive system) liver
a large, important gland with many different jobs
it makes bile to emulsify fats so that they can mix with the digestive juices in the small intestine
(role in digestive system) gall bladder
stores bile made by the liver
when the fat is eaten, the bile is emptied into the duodenum
(role in digestive system) duodenum
first part of the small intestine
bile and juice from the pancreas are added to the food in the duodenum
(role in digestive system) large intestine (colon)
absorbs water from the chyme into the blood, leaving solid waste called faeces
absorbs bile salts from waste material
minerals are also absorbed
caecum
first large part of the large intestine
(role in digestive system) appendix
no part of digestion, little value to humans
rectum
last part of the large intestine
where the faeces (made up mainly of indigestible food) are stored before they are passed out through the anus (egestion)
anus
the final sphincter
describe sphincters
Muscular walls thickened to form rings of muscle called sphincters
Can contract to close the tube and relax to open it
Sphincters at each end of the stomach can either hold food in the stomach or let it pass out
Main sphincters:
CS- cardiac spincter (start of stomach area)
PS- pyloric sphincter (end of stomach area)
ICV- ilio-caecal valve (around caecum)
AS- anal spincter (end of anus)
name of the process of chewing
mastication
what does mechanical digestion do
increase the surface area of the food by breaking it into smaller pieces
• provides larger surface area for digestive enzymes where they can BREAK down COMPLEX food MOLECULES into SIMPLE ones (chemical)
4 different types of teeth
incisors
canines
premolars & molars
incisors
chisel-shaped at the front of the mouth
used to cut pieces from food
canines
pointed teeth on both sides of the incisors
used for gripping and tearing
premolars and molars
flat-topped teeth in the cheeks (have points or cusps)
upper and lower cusps fit together
used for grinding and crushing food between their surfaces
crown
part of the tooth which is visible above the gum
its shape depends on the job which it has to do
neck
the part of the tooth covered by the gum
root
the part of the tooth which is fixed into the jawbone
- root canal lets blood in to feed the tooth
- as human teeth gets bigger, this canal becomes narrow, reducing the blood supply until the tooth stops growing
cement
bone like tissue which covers the root
fixes the root of the tooth into a bony socket in the jaw
fibrous tissue
joins the cement to the bone
they allow the tooth a little movement in its socket, so reducing the risk of breakage
pulp cavity
hollow space in the centre of the tooth
contains pulp which carries nerves to give the tooth ‘feeling’ and blood vessels to feed the tooth
cavity is lined with cells which make the dentine
dentine
hard as bone (softer than enamel, inside enamel)
most of the tooth made of dentine
running through are tiny channels which carry the raw materials needed to build up and feed the tooth
enamel
the hardest material in the body
forms the tough outer covering of the crown of the tooth
fluoride does what for teeth?
strengthens the enamel of the teeth, giving them a hard exterior surface
tooth decay is caused by
bacteria in plaque, which changes sugar to acid that attacks the enamel and dentine of the tooth
what happens if particles of sugary food are left between your teeth
Bacteria in plaque changes the sugar into acid because they are respiring anaerobically
Acid attacks the enamel on the surface of a tooth and this starts off tooth decay
When the enamel is worn away, acid will attack the dentine
If the cavity reaches the pulp cavity it will cause a severe toothache, an abscess may form in the root
acid can make your gums
red and swollen
dentine is not ____ and dissolves ____
dentine is not acid resistant and dissolves easily
holes formed in the teeth are called ?
dental cavities/caries
describe the process up to swallowing food
• incisor and canine teeth bite into chunks
premolar and molar grind into smaller pieces
• mixed with saliva, moistened, rolled into a bolus and pushed to back of mouth (pharynx) and swallowed
• epiglottis closes over opening of trachea (glottis), preventing food from going into the lungs
if food goes the wrong way it
triggers a reflex cough
salivary glands make saliva which contains
mucus: slimy substance that lubricates the passage of the food bolus down the throat
amylase: the enzyme that catalyzes the breakdown of starch to maltose
after leaving the stomach the food is called
chyme
chyme is pushed along the tube by what process?
peristalsis
peristalsis (bolus)
involves a wave of muscular contractions that squeeze the food bolus, carrying it down the oesophagus to the stomach
describe peristalsis
circular muscles contract (CC) & longitudinal muscles relax (LR) BEHIND bolus to PUSH it along
circular muscles relax (CR) and longitudinal muscles contract (LC) to widen the oesophagus to allow the bolus of food to move along
does peristalsis also occur in the s and l intestine
yes but to lesser extent
where does amylase work best, where does it stop
neutral pH
stops once bolus reaches the stomach
food arrives from the oesophagus into the stomach through the _______
cardiac sphincter
stomach is located —-
left of the body, just below the diaphragm
Roles of the stomach
- physical churning, mixing, and breaking up of food from the bolus (MECHANICAL digestion)
- destruction of bacteria, fungi etc that might enter the body with the food
- the CHEMICAL digestion of PROTEINS
muscular sac
glands of the stomach produce
gastric juice and mucus
what does the gastric juice contain and what does it do
the protease enzyme pepsin which breaks down proteins into shorter chains of amino acids called peptides
(word eq: ..?)
hydrochloric acid
- optimum pH for pepsin, kills potentially harmful microbes
whats needed for chemical digestion of proteins in the stomach
hydrochloric acids and pepsin (enzyme) from gastric juices
how does mechanical digestion in the stomach happen
muscular contraction (peristalsis)
how does chyme leave the stomach
through the pyloric sphincter
what coats the stomach’s walls and what does it do
mucus coats the stomach’s walls
forms protective barrier between it and gastric juice which would damage tissues
food leaving the stomach enters the ___
duodenum
which two important associate organs have ducts leading into the duodenum
pancreatic duct- bringing pancreatic juice from the pancreas
the bile duct- bringing bile from the gall bladder, where it has been stored after being made by the liver
what does the entry of chyme into the duodenum trigger
release of bile and pancreatic juice down their ducts
bile and pancreatic juice are ___ because —
pH
alkaline because the food from the stomach has a low pH which makes it unsuitable for enzymes in the small intestine
bile contains ___ ____ and _____
bile pigments and cholesterol
why is the breakdown of fats by bile mechanical and not chemical digestion?
the molecules aren’t chemically changed by enzymes
How does the emulsification by bile salts aid chemical digestion by enzymes?
The smaller droplets have more surface area for the enzymes to act on
what does pancreatic amylase do
continues breaking down any remaining starch molecules to maltose
maltase
- enzyme found in the membranes of the epithelium cells that line the small intestine
- breaks down the double sugar maltose into the single sugar glucose which is absorbed
what does trypsin do
breaks down proteins down into amino acids
is protease enzyme like pepsin
why is trypsin needed in the small intestine instead of pepsin
optimum pH of pepsin is acidic (1.5-2.5) but the conditions of the intestine are alkaline
esophagus
the muscular tube that connects the mouth and stomach
pancreas
what does it produce and where are they released
produces trypsin, amylase and lipase enzymes
releases these into the small intestine
small intestine
- produces protease (trypsin), amylase, and lipase enzymes to complete digestion
- where nutrients are absorbed out of the alimentary canal into the body
- where most of the water is absorbed into the body
- it has two parts – the duodenum and the ileum
gum
soft tissue that surrounds and protects the tooth and bone
where is amylase made
salivary glands, pancreas, small intestine
where are proteases made
stomach, pancreas, small intestine
SPSI
where are lipase made
pancreas, small intestine
describe the process of diarrhoea
diarrhoea is watery faeces
• occurs when water can’t be absorbed from the intestines/ extra water secreted onto them
• loss of water
-> dehydration
-> loss of salt, glucose and other important minerals
- affects the functioning of the body, can cause the
body to lose more water
long time -> serious dehydration, maybe death
how does ORT work
what are ORSalts usually made of
drinking water that contains relatively large amounts of dissolved salt, glucose, and other important minerals
• brings body’s levels of water, salt, glucose and other important minerals back up
needs to be given regularly until diarrhea stops
ORS made of mixture of salts, glucose and cooled boiled water
• diarrhea: sodium rich intestinal secretions lost before they can be reabsorbed
• glucose: imp energy source, can’t be absorbed properly from gut without enough sodium
what are absorbed into the lacteals and drained into the lymphatic system
what happens to them after
fatty acids, glycerol and fat-soluble vitamins absorbed into lacteals
this transports them to a blood vessel under the coller bone where they join the general circulation
(vili) what substances are absorbed into the ___ network
sugars such as glucose, amino acids, minerals and water-soluble vitamins absorbed into the capillary network in the vili
(vili) are the materials actively or passively transported
both
adaptions of small intestine
- long tube with ridged walls covered with finger-like projections called villi and these have cells with projections called microvilli -> large SA
- rich blood supply- large SA for exchange
- lacteals which help with the absorption of less soluble vitamins
lacteal
digested fats go here and are taken away into the lymphatic system
what do glands (small intestine) make to do what
cells make digestive juice to add to the food in the small intestine
why is defecation egestion rather than excretion
excretion is the removal of newly created chemicals which is not the case for defecation
what are absorbed into lacteals and what happens to them
fatty acids, glycerol and fat-soluble vitamins absorbed into the lacteals and drained into the lymphatic system
transports them to blood vessel under coller bone -> join general circulation
how is cholera treated
ORT, patients drink mixture of water, glucose and salts to rehydrate themselves
(vili) what do the capillaries do and what is a result of this
carry absorbed molecules away
- > maintains high concentration gradient
- allows more molecules to diffuse into capillaries
Salivary amylase
6.8
Pancreatic protease (trypsin)
7.5-8.0
Stomach protease (pepsin)
1.5-2.0
Describe the structure of a villus
- Central lacteal used for transporting fatty acids and glycerol in the
lymph fluid - Lots of capillaries to absorb nutrients into the blood
- Thin wall to minimise the diffusion distance
Give 2 examples of protease enzymes
Pepsin and trypsin
Where in the alimentary canal is lipase secreted?
pancreas
How can dental decay be prevented?
-Brush teeth regularly and thoroughly with
fluoride containing toothpaste twice a day for
roughly 2 minutes
- Control diet and limit the consumption of
sugary food and drinks
How are villi adapted for absorption?
- Thin walls
- Large surface area
- Good blood supply close to the surface
How is the ileum adapted to absorption?
The ileum is lined with villi and microvilli
which provide a large surface area for
absorption
What is the function of the duodenum?
The duodenum receives food directly
from the stomach and uses enzymes
and chemical digestion to break the food
down
Describe the passage of food through the alimentary
canal
Mouth → oesophagus → stomach →
small intestine → large intestine →
rectum
What is the difference between the alimentary canal and the digestive system?
The alimentary canal involves the tubes
that the food passes through whereas
the digestive system also includes digestive glands
What is an ion channel?
They are proteins that span cell membranes that
allow charged molecules to pass through the
membrane
ileum
second section of the small intestine
main site of absorption of the products of digestion
enzymes in the epithelial lining digest peptides and maltose
other than enzymes what does pancreatic juice contain
sodium hydrogen carbonate which partially neutralizes gastric juices from the stomach
