major parts of the digestive tract
oral cavity
- pharynx
-esophagus
- stomach
- small intestine
- large intestine
- anus
histological layers of the digestive tract
- mucosa : inner most layer secrets mucus
- sub mucosa : connective tissue layer contains blood vessels
- muscularis : 2/3 muscle layers movement and secretion
- serosa : outmost layer, holds tract together
mouth function
- chew food and turn into bolus
- mechanical and chemical digestion
oesophagus function
- transport bolus to stomach
stomach function
- mechanical digestion - food churned
- chemical digestion - protein digestion
small intestine function
chemical digestion of carbs, proteins and lipids by pancreatic enzymes
absorption of small molecules
large intestine function
last chance for body to reabsorb any nutrients, bacteria in the large intestines produces vitamins and then faeces is formed. As more water is absorbed from the chyme the faeces becomes harder and is pushed towards the rectum
three accessory organs of the digestive tract
- liver,
gallbladder and pancreas
liver function
breaks down fat and produces bile
gall bladder function
stores bile which is then delivered to the duodenum
pancreas function
produces digestive enzymes and pancreatic juices
difference between digestion and absorption
digestion is the breakdown of foo into building blocks
absorption is when the building blocks are absorbed into the blood stream and delivered to the cells
carbohydrates
- monosaccharides
- produce atp
- backbone of dna and rna
protein
amino acids, peptide bonds
- regulate body functions, hormones and enzymes
lipids
triglyerides (glycerol and 3 fatty acids)
- used to produce atp
- require more energy to break down
recommended amounts of lipids carbohydrates and proteins
lipids 20-35%
carbohydrates 45-65%
proteins 10-35%
stages of digestion
ingestion - intake of food
digestion - breakdown of food into building blocks. mouth stomach small intestine
absorption - building blocks are absorbed into the blood stream and delivered to cells, liver
cellular respiration - cells breakdown the building blocks to release energy
function of bile
break down fat allowing enzymes to better access the lipids
mastication
to chew food begin mechanical breakdown by breaking down food into smaller pieces allowing digestive enzymes to come into contact with greater surface area of food particles
role of the tongue once food is in the mouth
- tongue pushed the bolus against the hard palate and then directed it to the pharynx and then into the oesophagus
types of teeth
incisors, canines, premolars, molars
number of each tooth and the role it plays in digestion
incisors 8 cutting
canines 4 tearing
pre molars 8 grinding
molars 12 grinding
how does saliva contribute to digestion
saliva is composed of serous and mucous which helps lubricate the food for easier chewing and swollowing
why is the small intestine so long
Make sure all nutrients are absorbed from the broken down food are absorbed into the blood, once in the blood they go to the cells where they are used to produce energy or form substances within the cell
