digestive system Flashcards
steps of digestion
- ingestion
- digestion
- absorption
- assimilation
- elimination
ingestion
taking food into the body
digestion
breaking down food
absorption
moving food into cells
assimilation
making food part of the cell
elimination
removing unused food
catabolism (metabolism)
larger molecule → smaller molceules + energy
anabolism (metabolism)
smaller molecules + energy → larger molecule
where does digestion take place
the gastrointestinal tract / alimentary canal
main organs of the gastrointestinal tract
- mouth
→ + salivary glands - esophagus
- stomach
- small Intestine
→ + duodenum, jejunum, ileum - caecum (in some cases)
- large Intestine
→ + colon - rectum
accessory organs of the gastrointestinaln tract
- liver
- gall bladder
- pancreas
mastication
chewing
incisors
- teeth at the front
- sharp
- used to cut food
canine teeth
- in the corner of the mouth
- long roots
- used for grasping and tearing at food
premolar teeth
- behind the canine teeth
- flat surface
- used for chewing
molar teeth
- at the back of the mouth
- bigger than premolars
- flatter surface than premolars
- used to chew smaller pieces of food
carnivore teeth
- canines
- inciosors
- premolars
- few molars
herbivore teeth
- incisors
- molars
- premolars
- no canines
omnivore teeth
- incisors
- canines
- molars
- premolars
why does the body produce saliva?
to start enzyme breakdown of food and to protect the oral mucosa
what enzymes are produced in the salivary glands?
- amylase (for carbohydrates)
- lingual lipase (for fats)
- lysozyme (acts as antiseptic)
oesophagus
- tube connecting the mouth to the stomach.
- smooth muscle for moving food
- food + saliva being swallowed down is called a bolus
mechanical digestion in the monogastric stomach
manual breakdown of food through the contraction of the stomach muscles moving the food towards the small intestine
chemical breakdown in the monogastric stomach
enzymes breaking down the food
monogastric stomach
- single chamber
- musucular bag
- folds (rugae) on the inside
- stomach expands when food enters from the oesophagus
- three layers of muscle; oblique, circular, longitudinal
enzymes in the monogastric stomach
- pepsin → breaks protein into amino acids
- gastric lipase → continues to break down fats
mucosa of the mongastric stomach
- inner lining of the stomach
- covered in gastric pits which lead to gastric glands
- parietal cells secrete hydrochloric acid
- chief cells secrete proteases
- neck cells secrete mucus
mucus
- secreted in the mucosa of the stomach
- protects the stomach lining from acids
- prevents auto-digestion (stomach digesting itself)
small intestine
- mucosa is the innermost layer → made of villi that increase surface area for absorption + lacteals for fat absorption
- more enzymes to further break down food
mechanisms for absorption
- osmosis → across a semipermeable membrane
- diffusion → from high concentration to low concentration
- active transport → from low concentration to high concentration, requiring cellular work
three parts of the small intestine
1.) duodenum
2.) jejunum
3.) ileum
caecum
large organ containing micro-organisms specialised for digestion of cellulose (hindgut fermentation)
large intestine
- no enzymes made in the large intestine
- water + some nutrients absorbed back into the body
hindgut fermenters
efficient at digesting cellulose through fermentation in the caecum / large intestine → produce bacteria to digest food which produce the enzymes necessary to break down cellulose
examples of hindgut fermenters
- guinea pigs
- horses
- rabbits
coprophagy
when animals eat a kind of faeces called caecotroph → gives the animal two chances at digesting the nutrients in their food, making their digestive systems very efficient
examples of animals that exhibit coprophagy
- capybaras
- hamsters
- rabbits
- chimps
- pigs
liver functions
- bile production + excretion
- excretion of bilirubin, cholesterol, hormones + drugs
- metabolism of fats, proteins + carbs
- enzyme activation
- storage of glycogen, vitamins + minerals
- synthesis of plasma proteins, such as albumin, + clotting factors
gallbladder functions
- stores and concentrates bile from the liver
- bile is released into the first section of the small intestine (duodenum)
pancreas functions
- makes alkaline pancreatic juices and enzymes
- contains bicarbonate, an alkaline substance that acts to neutralise stomach acids
- makes hormones
ruminant
- efficient at digesting cellulose through fermentation + ‘chewing the cud’
- food is digested by bacteria, which produce the enzymes to break down cellulose → bacteria located in the rumen
- ruminants don’t have top incisors, but have a dental pad
ruminant stomach segments
- rumen
- reticulum
- omasum
- abomasum
rumen
- largest segment of the ruminant stomach
- rely on bacteria to produce enzymes
- bacterial fermentation
- fats absorbed in the rumen
- breaks down food
- releases methane through eructation (burping)
- stores undigested plant material
- absorbs fatty acids and cellulose
reticulum
- separated from the rumen by a muscle fold
- contracts for mechanical digestion
- has a honeycomb-like filter that stops large particles entering the omasum
omasum
- grinds + squeezes
- absorbs water + nutrients (fatty acids)
- filters large food particles to be returned to the reticulum
abomasum
- final compartment
- known as the true / actual stomach
- similar to monogastric stomach
- hydrochloric acid and enzymes are secreted for nutrient breakdown
- symbiotic bacteria is digested in the abomasum and is a main source of protein
