The Digestive System Flashcards
(21 cards)
What is digestion?
Chemical (enzymes) and physical breakdown of food into small soluble pieces to ensure food can be absorbed into bloodstream
What does autotrophic mean?
An organism that can make it’s own food
(E.g. plants)
What does heterotrophic mean?
Organisms that cannot make their own food
(E.g. Herbivores, omnivores, carnivores)
What is a saprophyte?
Organism that takes its nutrition from a dead source (fungi)
What are the five stages of human nutrition?
- Ingestion
- Digestion
- Absorption
- Assimilation
- Egestion
What occurs in the mouth?
Physical digestion - Teeth
Incisors (2/2), canines (1/1), molars (2/2), premolars (3/3)
Chemical digestion - Saliva
Contains an enzyme called amylase (breaks down starch into maltose)
What occurs in the oesophagus?
A bolus (ball of food) is formed and swallowed.
Bolus of food enters the oesophagus by epiglottis.
Food is moved by muscular action called peristalsis.
Food enters the stomach by the cardiac sphincter muscle
What occurs in the stomach?
Physical digestion by churning the food.
Food remains for 1 and a half hours and forms chyme.
It leaves the stomach into small intestine by pyloric sphincter muscle.
What gastric juices are found in the stomach?
Hydrochloric acid, pepsinogen and mucuous
What is the function of hydrochloric acid?
pH 2 (acidic)
Kills bacteria
Activates pepsinogen into pepsin
What is the function of pepsinogen?
Activated into pepsin by hydrochloric acid and chemically digests polypeptides (protein)
What is the function of mucous?
Lining of stomach muscle preventing self digestion and ulcers
What are the two parts of the small intestine called?
The ileum and the duodenum
What occurs in the duodenum?
Digestion is fully achieved.
Pancreas releases pancreatic enzymes into duodenum
Name the pancreatic enzymes released into the duodenum.
Pancreatic protease
(Breaks down proteins into amino acids)
Pancreatic amylase
(Breaks down starch into maltose
Pancreatic lipase
(Breaks down lipids into glycerol and 3 fatty acids)
Pancreatic maltase
(Breaks down maltose into glucose)
What occurs in the ileum?
Ileum coiled to increase surface area for absorption
Absorption occurs here through villi in bloodstream
Inner lining of ileum contains finger like projections called villi.
Digested food moves through the thin walls of villi into the bloodstream (except fats).
The ileum joins to the liver by the hepatic portal vein carrying blood rich in absorbed food.
Fats (fatty acids and glycerol) move into the lacteal of villi.
All lacteals join and fats enter the lymphatic system (vessel)
Fats drain into the blood at the subclavian vein (collarbone)
How are villi adapted?
They’re one cell thick for rapid absorption of food.
Excellent blood supply for rapid movement of nutrients.
Finger like increasing surface area for absorption.
Microvilli for increasing surface area for absorption.
What occurs in the liver?
Liver produces bile which is stored in the gallbladder and released into duodenum by bile duct.
Deamination
(Breaks down proteins into urea)
Stores glucose (glycogen), vitamins and minerals
Detoxifies
What is the name of the vein that connects the liver to the small intestine?
Hepatic portal vein
What occurs in the large intestine?
Small intestine joins to large at a junction called caecum.
Undigested food moves through large intestine (colon, rectum (stored), and anus) by a process called peristalsis
What is the function of the large intestine?
Reabsorb H2O leaving a solid waste (faeces).
Symbiotic bacteria live in large intestine and digest cellulose, in turn they produce vitamins B and K.
