Transcript PP 1x

PP 1 Human Alimentary Canal/
Mechanical Digestion
Plus –Definitions for All of Digestion
Definitions
• Ingestion – taking in substances (food [eating] /
drinking) into the body through the mouth.
• Digestion – breaking down large insoluble food
molecules into small water soluble molecules
using mechanical and chemical processes.
• Absorption – movement of digested food
molecules through the wall of the intestines into
the blood or lymph .
Definitions continued
Assimilation – movement of digested food
molecules into the cells of the body where
they are used – becoming part of cell.
Egestion – Passing out of food that has not been
digested as faeces through anus
Alimentary canal = long tube that starts at the mouth and ends at the anus – the way food
travels through the system.
Ingestion
Assimilation
ENZYMES
ENZYMES
Digestion
Absorption
Egestion
Nasal Cavity
Mouth
Small intestine =
Duodenum ->
Ileum
Large Intestine =
Colon -> Rectum
Trachea
Oesophagus
Liver
Gall Bladder
Duodenum
Stomach
Pancreas
Ileum
Abdomen = the area below
Ribs and above Hip bone
Large Intestine
Appendix
Colon
Rectum
Anus
Capillary absorb:
• sugar / a. a. / vitamins
/ inorganic ions / water
Lacteal absorb:
• fatty acids / glycerol
The Villi: Surface area is important
•
Breaking food down
• 10 hours for food to pass through from the
mouth
• Mechanical digestion = physical breaking up
food by teeth (chewing) and stomach walls
churning (Peristalsis).
• Chemical Digestion = Break down of food
molecules via enzymes.
Regions of
Alimentary Canal
Functions
Relations to :
ingestion/
Digestion/
Absorption/
Assimilation
Mouth
(more on
chewing/teeth
structure/ fluoride
for teeth)
Use of lips / teeth / tongue to break down food
mechanically (Mastication = chewing).
Taste buds decide chemically if safe to eat or not.
Ingestion
Salivary glands
Water + Amylase (starch -> maltose) + Mucus
(slippery substance that allows slide)
Digestion
Esophagus
Takes food from mouth to stomach after swallowing.
Ingestion
Stomach
Gastric juices (HCl (pH 2) + pepsin – to break down
protein) secreted & Mucus also secreted to protect
the stomach from being digested itself (but if it does
happen – the sore is called an Ulcer.
Physical churning is called Peristalsis.
*Vitamins are directly absorbed
Digestion
*Absorption
Regions of
Alimentary
Canal
Functions
Relations to :
ingestion/ Digestion/
Absorption/
Assimilation
SI :Duodenum
Liver / Pancreatic juices mix here.
* Contains Villi (finger like projections)
Digestion
* Absorption
SI : Ileum
Contains villi: (finishes digestion / absorption)/
increases surface area to seep up the rate of
absorption) / thin walls so not must time /
space for absorption.
All large molecules broken down to their
simplest parts (maltose -> glucose via maltase)
Absorption: sugar / a.
a. / fatty acids /
glycerol / vitamins /
inorganic ions / water
(into blood or lymph)
Pancreas
Releases Pancreatic juices (enzymes) & flows
into duodenum via pancreatic duct. Also
contains Sodium hydrogen carbonate (helps
neutralize acids) from stomach pH 2 -> pH 6.5.
=. Avoids harm to small intestine.
Enzymes = carbohydrase (amylase) & Protease
(trypsin) & Lipase
Digestion
SI : Small Intestine / LI = Large Intestine
Regions
of
Aliment
ary
Canal
Functions
Relations to :
ingestion/ Digestion/
Absorption/
Assimilation
liver
Produces bile / store in gal bladder
Assimilation
After absorption of molecules – all go to the liver via
hipatic portal vein.
Liver’s job ; to Sort out molecules:
• Some molecules will be carried in blood to the cells that
need them.
• Some will be stored in liver
•Some will be changed for storage
Eg. Glucose that is not used will be converted to glycogen
(stored in liver). Long term stored glycogen will be
converted to fat (stored in other areas eg. Abdomen).
Eg. Amino acids will be used to make protein and then
transported by blood to other parts of the body.
Excess a. a. will be converted into urea and removed via
urine.
• Break down dangerous toxins (alcohol)
•Liver disease = cirrhosis
Regions of
Alimentary Canal
Functions
Relations to : ingestion/
Digestion/ Absorption/
Assimilation
Gal Bladder
Bile is stored here and released into
the duodenum when food is there via
the bile duct. Bile = Helps digest fats
(made of bile salts). Bile Salts break fat
into droplets this is called
Emulsification. It makes it easier for
the fats to be digested and later
absorbed.
Digestion
LI: Colon
Fiber and water left .
Water is absorbed
5-10 decimeter cubed of water
absorbed by the SI
0.3-0.5 Decimeter cubed by the LI
Absorption
LI: Rectum
Stores feces
Egestion
Anus
Removes feces
Egestion
SI : Small Intestine / LI = Large Intestine
Process of Chewing
• In the mouth:
- Large premolars and molars
- Both have broad surfaces / ridges on them =>
when pushed together they crush the food
- To increase the surface area of the food
- Makes it easier for the enzyme to work on the
food.
- Bolus = Food made by the tongue into a ball of
food to be swallowed.
Human teeth – structure / function
Structure
Function
Incisors
In front of mouth – helps to bite off pieces of food to take into the
mouth
canines
Next to incisors. Same function as incisors. In other carnivores – they
are longer – for killing prey
Pre molars
Behind the canines- for chewing food into small pieces and mix with
saliva – easier for swallowing and tasting & Increase surface area of
food so that digestive enzymes can work on food.
molars
Behind pre molars. Function – same as pre molars.
Dental decay / proper teeth care
• Tooth decay – when enamel
erodes due to acids (produced by
bacteria)
• Plaque formation – bacteria and
food caught in between teeth that
harden around the tooth.
• Foods full of sugar can increases
changes for plaque formation =>
dissolve enamel down to the
dentine.
Teeth decay prevention
• Avoid sugary foods.
• Regularly clean your teeth (brush / dental
floss/ tooth pick)
• Use tooth paste with fluoride (is absorbed by
the teeth and prevents acid build up)
• Visit dentist regularly.
Fluoride & prevention of tooth decay
• Fluoride in drinking water creates less tooth
decay.
• Too much fluoride can cause black spots of
teeth. Can cause vomiting / stomach cramps
too.
• Best concentration of fluoride is 1 part per
million.
Peristalsis
• Longitudinal muscles –
lengthwise
• Circular muscles – around
Swallow -> circular muscle relaxes
(tube gets wider) -> behind food
circular muscle contracts .
When circular muscle relaxes –
longitudinal muscle contracts
(visa versa)
• Happens all the way down the
alimentary canal