Digestive System Flashcards
How do heterotrophic organisms obtain nutrition?
“By taking in or ingesting food.”
What happens to food in the body?
“It is broken down into simple
What is the process of breaking down food called?
“Digestion.”
What happens to digested food?
“It is absorbed and used up by body cells (assimilated).”
How do organisms get rid of undigested food?
“Egested.”
What are the basic steps in heterotrophic nutrition?
“Ingestion
What varies among heterotrophs?
“The feeding mechanism.”
What does the feeding mechanism depend on?
“Whether the organism is holozoic
How do holozoic organisms obtain food?
“They have special structures for capturing prey or food.”
What kind of food do holozoic organisms eat?
“Solid or fluid food.”
What structures do holozoic organisms use to seize large food?
“Claws
How do holozoic organisms feeding on small food obtain it?
“Filter-feeding mechanisms.”
How do fluid-feeders obtain food?
“Structures for sucking fluid food.”
What form of food do parasitic and saprophytic organisms take in?
“Fluid form.”
How do saprophytes obtain food?
“Special mechanisms to change solid food to liquid before absorbing it.”
How do many parasites obtain food?
“Structures for boring into hosts and sucking tissue fluids.”
Where does digestion and absorption take place in most holozoic animals?
“Alimentary canal or gut.”
Where does digestion take place in unicellular animals?
“Inside the cell within a food vacuole (intracellular digestion).”
What kind of gut cavity do simple multicellular animals have?
“A sac-like gut cavity with one opening (the mouth).”
What is extracellular digestion?
“Digestion in the gut cavity
What kind of alimentary canal do most higher animals have?
“A long tube with two openings (mouth and anus).”
What is the function of the mouth?
“Taking in food.”
What is the function of the anus?
“Getting rid of undigested food.”
Where is Amoeba proteus found?
“Muddy water at the bottom of ponds and ditches.”
What does Amoeba proteus feed on?
“Microscopic organisms or decayed food substances.”
Does Amoeba have a mouth or alimentary canal?
“No.”
How does Amoeba obtain food?
“Puts out a pseudopodium to flow around and engulf food particles.”
What is a food vacuole?
“A small cavity formed when the pseudopodium engulfs food with some water.”
What is ingestion?
“The process of engulfing food particles.”
How is food digested in Amoeba?
“Enzymes from the cytoplasm are secreted into the food vacuole.”
What happens to the products of digestion in Amoeba?
“Soluble products diffuse into the cytoplasm.”
How does Amoeba get rid of undigested material?
“Egested as waste.”
Where does Paramecium caudatum live?
“Muddy waters.”
What does Paramecium caudatum feed on?
“Tiny microscopic organisms like bacteria and decayed food particles.”
How does Paramecium take in food?
“Beating of cilia creates a water current that enters the gullet through a mouth-like opening.”
Where does digestion occur in Paramecium?
“Food vacuoles in the cytoplasm (intracellular digestion).”
What happens to soluble nutrients in Paramecium?
“They diffuse into the cytoplasm.”
How does Paramecium get rid of undigested waste?
“Through the anal pore.”
What does Hydra eat?
“Tiny animals (carnivore).”
How does Hydra capture prey?
“Stinging cells on tentacles inject poison to stun it
Where does the prey go in Hydra?
“Gut cavity.”
What happens in the gut cavity of Hydra?
“Gland cells secrete digestive juices
What happens to partially digested food particles in Hydra?
“Amoeboid cells engulf them into food vacuoles for intracellular digestion.”
What happens to digested food in Hydra?
“It diffuses to all parts of the body.”
How does Hydra get rid of undigested wastes?
“Through the mouth.”
What do filter feeders eat?
“Plankton floating in the aquatic environment.”
How do filter feeders draw water towards themselves?
“Movements of appendages or action of cilia.”
How do filter feeders trap food?
“Water passes through a sieve-like structure in the gut.”
Examples of filter feeders
“Whales
What do whales use for filter feeding?
“Baleen plates made of whalebone.”
What does baleen do?
“Strains plankton from the water.”
What does a flamingo use for filter feeding?
“A straining device in its bill.”
What do oysters use for filter feeding?
“Gills.”
How do oysters trap food?
“Mucus-covered gills trap food particles from the water drawn in by cilia.”
What do mosquito larvae use for filter feeding?
“Feeding brushes (modified mouthparts with bristles).”
How do mosquito larvae trap food?
“Continuous movement of feeding brushes sweeps water containing microscopic organisms into the mouth.”
How is food separated in mosquito larvae?
“Straining devices in the foregut.”
How do copepods filter feed?
“Brush-like appendages create water currents that are directed into a filter chamber.”
What do fluid feeders eat?
“Fluids like nectar or body fluids.”
Examples of animals that feed on nectar
“Hummingbirds
Adaptations of fluid feeders
“Mouthparts adapted to reach and suck fluids (e.g.
Examples of insects that feed on sap
“Aphids
Examples of insects that suck body fluids
“Mosquitoes
How do ticks feed?
“Pierce the skin with hooked mouthparts and feed on blood.”
How do insects like aphids and leaf-hoppers feed?
“Pierce the plant surface and suck the sap in the phloem.”
Examples of insects that suck body fluids of other animals
“Mosquitoes
How do ticks pierce the skin?
“By means of hooked mouthparts.”
What are the functions of the mammalian alimentary canal?
“Breaking up food
How does the alimentary canal structure vary?
“According to the complexity of the animal and the kind of food it eats.”
What does the digestive system consist of?
“The alimentary canal and associated glands/organs that produce enzyme-rich secretions.”
Are the enzymes and reactions of digestion similar in all organisms?
“Yes.”
What is the first step in digesting food for most animals?
“Breaking it down into small molecules in the alimentary canal.”
How is food broken down in the alimentary canal?
“Mechanically and chemically.”
What is mechanical digestion?
“Teeth break up food into smaller pieces
Why is mechanical digestion important?
“Increases the surface area of food for effective chemical digestion.”
How is chemical digestion carried out?
“By enzymes.”
Do all animals have teeth?
“No.”
What is the function of teeth in most animals (if present)?
“To grasp food before swallowing.”
What is the function of mammalian teeth?
“Play an important role in mechanical digestion.”
What is dentition?
“The number
What is dentition related to?
“The type of food a mammal eats.”
What kind of dentition do humans have?
“Omnivorous.”
How many sets of teeth do humans have?
“Two (milk and permanent).”
How many milk teeth do humans have?
“20.”
How many permanent teeth do humans have?
“32.”
What are the four types of permanent teeth?
“Incisors
What is the shape and function of incisors?
“Chisel-shaped
What is the shape and function of canines?
“Conical
What is the shape and function of premolars and molars?
“Broad surfaces for grinding food.”
What is a dental formula?
“A way to show the number and types of teeth in one half of each jaw.”
What is the dental formula of a human?
“2 1 2 3 / 2 1 2 3 = 16 (times 2 = 32 total).”
What do the letters in the dental formula stand for?
“i (incisor)
What are the main parts of a tooth?
“Crown
Where is the crown located?
“Projects above the gums.”
Where is the root located?
“Embedded in the jawbone.”
What is the neck of a tooth?
“The junction of the crown and root.”
What is the pulp cavity?
“The center of the tooth
What is dentine?
“A hard
What is the function of the hole at the tip of the root?
“Allows blood vessels and nerves to connect to the pulp.”
What is enamel?
“A white layer covering the dentine in the crown
What is the function of enamel?
“Protects the pulp and dentine.”
What covers the dentine in the root region?
“Cement.”
What surrounds the cement?
“The periodontal membrane
Is the tooth rigidly fixed to the jawbone?
“No
Does a tooth grow?
“No
Why do teeth decay?
“Germs grow on food stuck to the teeth and produce acids.”
What do the acids do to teeth?
“Wear away enamel and dentine
What are the consequences of tooth decay?
“Toothache
How can we prevent tooth decay?
“Regular oral hygiene
What is the alimentary canal?
“A long tube from the mouth to the anus.”
Where is most of the alimentary canal located?
“Coiled up in the abdominal cavity.”
What are the main regions of the alimentary canal?
“Mouth
What happens to food in the mouth?
“Teeth cut and grind it
What enzyme is present in saliva?
“Ptyalin.”
What does ptyalin do?
“Acts on cooked starch
What kind of substance is saliva?
“Watery
What does the tongue do in the mouth?
“Mixes food with saliva and rolls it into a bolus.”
What is a bolus?
“A ball of chewed food.”
What is the function of the epiglottis?
“Covers the trachea during swallowing to prevent choking.”
What is the oesophagus?
“A muscular tube that carries food from the pharynx to the stomach.”
How does food move through the oesophagus?
“Peristalsis (alternating muscle contractions and relaxations).”
What is anti-peristalsis?
“Backward movement of food.”
How does food enter the stomach?
“Sphincter at the entrance of the stomach relaxes.”
What happens to food in the stomach?
“Muscular walls churn it
What does gastric juice contain?
“Pepsin
What is the function of pepsin?
“Digests proteins to polypeptides
What is the function of hydrochloric acid in the stomach?
“Kills bacteria in food.”
What is the function of rennin?
“Coagulates milk into curds (casein)
What is chyme?
“Thick
How long does food stay in the stomach?
“Three to four hours.”
Where does chyme go after the stomach?
“Duodenum.”
What is the duodenum?
“First part of the small intestine.”
What are the other parts of the small intestine?
“Jejunum and ileum.”
What is secreted into the duodenum?
“Pancreatic juice and bile.”
Where is pancreatic juice produced?
“Pancreas.”
What kind of liquid is pancreatic juice?
“Watery alkaline liquid.”
What enzymes are present in pancreatic juice?
“Amylopsin
What does amylopsin do?
“Breaks down starch to maltose.”
What does trypsin do?
“Breaks down proteins to polypeptides.”
What does lipase do?
“Breaks down fats to carboxylic acids and glycerol.”
What kind of medium do pancreatic juice enzymes require?
“Alkaline.”
Where is bile produced?
“Liver.”
Where is bile stored?
“Gall bladder.”
What kind of liquid is bile?
“Greenish alkaline liquid.”
Does bile contain digestive enzymes?
“No.”
What are the functions of bile?
“Adds water to chyme
What does emulsify fats mean?
“Breaks down large fat droplets into tiny droplets.”
What is chyle?
“More watery form of chyme in the ileum.”
Where is intestinal juice produced?
“Special cells of the small intestine (ileum).”
What kind of medium do intestinal juice enzymes work in?
“Alkaline.”
What does maltase do?
“Changes maltose to glucose.”
What does lactase do?
“Changes lactose to glucose and galactose.”
What does sucrase do?
“Changes sucrose to glucose and fructose.”
What are the end-products of carbohydrate digestion?
“Simple sugars (glucose
What does erepsin do?
“Changes polypeptides to amino acids.”
What are the end-products of protein digestion?
“Amino acids.”
What does lipase do (small intestine)?
“Changes fats to carboxylic acids and glycerol.”
What are the end-products of fat digestion?
“Carboxylic acids and glycerol.”
Where are glucose, amino acids, fatty acids, glycerol, vitamins, and mineral salts absorbed?
“Small intestine.”
What are the adaptations of the small intestine for absorption?
“Folds and furrows
What are villi?
“Small finger-like projections that increase the surface area of the small intestine.”
What is the epithelium of the villus?
“The thin inner surface layer that allows absorption.”
What vessels are present in villi?
“Blood capillaries and lacteals (lymphatic tubes).”
What do lacteals absorb?
“Fatty acids and glycerol (recombined to form fats).”
Where do lymphatic vessels empty their contents?
“Into blood vessels near the heart.”
Where are excess fats stored?
“In adipose tissue (fat cells).”
What do capillaries absorb?
“Sugars
Where do capillaries transport absorbed food?
“Hepatic-portal vein.”
What organ processes the food substances?
“Liver.”
What does the liver do with the food substances?
“Breaks some down
Where is the food carried after the liver?
“To cells in the rest of the body for assimilation.”
What happens to undigested food?
“Passes into the colon (large intestine).”
What is absorbed in the colon?
“Water.”
What are faeces?
“Semi-solid waste products in the colon.”
Where are faeces stored?
“Rectum.”
How are faeces eliminated?
“Through the anus.”
What facilitates the movement of faeces?
“Dietary fibre or roughage.”
What is constipation?
“Difficulty in removing the bowels due to insufficient roughage.”
How long does it take for food to pass through the gut?
“About one and a half days.”
What is the largest organ in the body?
“Liver.”
What vessels bring blood to the liver?
“Hepatic-portal vein (from gut) and hepatic artery (oxygenated blood).”
