what is the digestive system
6-0m tube lined with music covered epithelium. accessory organs attached to tube to help process/digest food
components of the digestive system
mouth, pharynx and oesophagus, peristalsis, stomach, small and large intestine, liver, gallbladder, pancreas and hepatic portal vein
function of the mouth
- food is broken up by teeth/tongue, moistened by saliva which initiates digestive of polysaccharides
- salivary glands secrete amylase
function of pharynx and oesophagus
- move food to stomach, gastric juices released and protein digestion starts
- respiratory passage closed off by soft palate and epiglottis to ensure food doesn’t enter nose or trachea
what is peristalsis
food is passed along digestive system by muscular contraction called peristalsis
function of stomach
- highly acidic, kills pathogens, alcohol is absorbed by stomach
- pepsin starts digestion (chemical)
function of small intestine
most nutrients are absorbed through villi and microvilli which increase the surface area
3 parts of the SI
- duodenum
- jejunum
- ileum
what does the duodenum do
receives secretions from liver, gallbladder and pancreas
what does the jejunum do
digestion and nutrient absorption
what does the ileum do
absorbs nutrients
what is absorbed in the SI
monosaccharides, amino acids, fatty acids, monoglycerides and nucleotides
function of large intestine
absorb left over material and then the indigestible material, bacteria and water accumulate in the rectum at the end of the digestive process
what is absorbed in the LI
water, salt and vitamins
how does the defection reflex get initiated
the rectal walls stretch
role of liver
- secretes bile, role in metabolism
- removes/breaks down toxins
- stores vitamins
- absorbs glucose and stores as glycogen
role of gallbladder
stores bile, releases bile into intestine to help digest fat
role of pancreas
neutralises acid from stomach and secretes digestive enzymes
role of hepatic portal vein
- intestines absorb products of digestion
- nutrients then travel via hepatic portal vein to liver - stored or released according to current contents of blood
nutritional requirements
55-60% complex carbs, 15-20% proteins and 20-25% fats
