6.1 digestive system Flashcards
salivary glands
moistens food into a bolus. begins polysaccharide digestion. Secrete salivary amylase to start the digestion of starch.
Release saliva to moisten food and contains enzymes (e.g. amylase) to initiate starch breakdown. Salivary glands include the parotid gland, submandibular gland and sublingual gland.
draw diagram of digestive system
see ipad (photos)
liver
detoxifies certain molecules. stores vitamins, iron, glycogen. synthesizes bile.
Takes the raw materials absorbed by the small intestine and uses them to make key chemicals. Its role includes detoxification, storage, metabolism, bile production and haemoglobin breakdown.
gall bladder
stores / concentrates bile
The gall bladder stores the bile produced by the liver (bile salts are used to emulsify fats). Bile stored in the gall bladder is released into the small intestine via the common bile duct.
small intestine
absorbs nutrients.
A long, highly folded tube where usable food substances (nutrients) are absorbed. majority of digestion & absorption occurs here.
peristaltic muscle contractions slow to allow time for digestion/absorption
the wall of the small intestine contains villi to increase surface area for absorption.
rectum / anus
stores and expels feces
esophagus
transports food to stomach
A hollow tube connecting the oral cavity to the stomach. Food is mixed with saliva and then is moved in a bolus via the action of peristalsis.
stomach
stores and churns food. begins protein digestion.
A temporary storage tank where food is mixed by churning and protein digestion begins. It is lined by gastric pits that release digestive juices, which create an acidic environment (pH ~2)
pancreas
releases digestive enzymes. releases hormones (e.g. insulin). Also secretes certain hormones (insulin, glucagon), which regulate blood sugar concentrations.
Secretes digestive enzymes that include amylases, peptidases, lipases
Also secretes bicarbonate ions, a weak base, to neutralize stomach acid.
Also an organ of the endocrine system
large intestine
absorbs water and ions.
The final section of the alimentary canal, where water and dissolved minerals (i.e. ions) are absorbed. Consists of the ascending / transverse / descending / sigmoidal colon, as well as the rectum.
peristalsis
longitudinal and circular smooth muscles contract and relax to create a “peristaltic wave” that allows food to move along the digestive tract
digestion
the breaking down of food into smaller particles. mechanical and chemical.
mechanical digestion
includes chewing (mouth) and churning (stomach)
chemical digestion
the breakdown of polymers into monomers in enzyme catalyzed reactions. digestive juices aid this process.
alimentary canal
consists of organs through which food actually passes (oesophagus, stomach, small & large intestine)
3 enzymes of the digestive system
amylases, proteases/endopeptidases, lipases
accessory organs
aid in digestion but do not actually transfer food (salivary glands, pancreas, liver, gall bladder)
mouth pH
7
label a transverse cross section of the small intestine
see ipad (photos)
label a longitudinal cross section of the small intestine
carbohydrate digestion: how does Starch (amylose/amylopectin) → maltose → glucose → glucose monomers
starch → maltose
- mouth
- enzyme: salivary amylase, secreted from salivary glands
- optimal pH around 7
maltose → glucose
- small intestine
- enzyme: pancreatic amylase, secreted from pancreas
- optimal pH: 8
The epithelial lining of the small intestine also contains an enzyme called maltase, which further breaks down glucose into monomers.
Glucose then travels to the liver where it is metabolized into glycogen (if insulin levels are high).
protein digestion
Proteins → peptide → amino acids
protein → peptide
- stomach
- enzyme: pepsin, secreted from stomach
- optimal pH: 2
peptide → amino acids
- small intestine
- enzyme: trypsin, secreted from pancreas
- optimal pH: 8
pepsin
a type of protease enzyme
lipid digestion
- (triglycerides) → fatty acids + glycerol
- small intestine
- enzyme: lipase, secreted from pancreas
- optimal pH: 8
Explain the action of enzymes in the digestive system
Enzymes are proteins that speed up the rate of reactions
Each enzyme has an optimal pH level (max rate of reaction). Above/Below that pH, it is denatured.
3 components of small intestine
- lumen
- mucosa
- smooth muscle
structure of a villus (6)
- Single-layer of epithelial cells
- Large blood supply/capillary network
- Large number of villi
- Microvilli
- Lacteal
- Membrane Proteins
label villi diagram
see ipad (photos)
function of single-layer of epithelial cells in villi in small intestine
easy transport of nutrient, thin layer to cross
function of Large blood supply/capillary network in villi of small intestine
more surface area for absorption
function of having a large # of villi in small intestine
more surface area for absorption
function of microvilli in small intestine
more surface area for absorption
function of lacteal in villi of small intestine
transport of fatty acids
function of membrane proteins in villi of small intestine
facilitated diffusion & active transport
how is glucose transported across the epithelial cells of the small intestine?
- Secondary Active
- Co-transport w/ Na+ ions
- into Bloodstream
how are monosaccharides (besides glucose) transported across the epithelial cells of the small intestine?
- Facilitated diffusion
- Hydrophilic Channel proteins
- into Bloodstream
how are amino acids transported across the epithelial cells of the small intestine?
- Secondary Active
- Co-transport w/ Na+ ions
- into Bloodstream
how are lipids transported across the epithelial cells of the small intestine?
- Simple diffusion
- simple diffusion into hydrophobic part of plasma membrae
- into Lacteal
where are carbs, proteins, and lipids digested?
Carbohydrates are broken down in the mouth and small intestine, proteins in the stomach and small intestine, and lipids in the stomach and small intestine.
