Digestive System Flashcards
digestive tract
- hollow passage from the mouth to the anus/cloacal opening
division of digestive tract (3)
- buccal cavity
- pharynx
- alimentary canal
alimentary canal (4)
- esophagus
- stomach
- small intestine
- large intestine
how does food truly enter the body
- it must be absorbed: pass through an epithelial cell or pass between two epithelial cells
digestive system: main functions
- digestion
- absoprtion
digestion
- breaking down of food into molecules that can be absorbed
absorption
- uptake of molecules through the epithelium of the digestive tract into the blood or lymph
general process of the digestive system (8)
- ingestion
- food storage
- mechanical digestion
- chemical digestion
- microbial digestion
- absorption
- water reabsorption
- defecation
general diets (6)
- other animals (carnivore)
- plants (herbivore)
- combination of everything (omnivore)
- dead organic material
- blood
- nectar
quality of food
- the relative difficulty of digesting the food and the amount of energy released when the food is digested
higher quality foods (2)
- release of a relatively large amount of energy
- requirement of relatively little time or energy for digestion
rank the quality of these foods: whole fish, leaves, blood
- blood
- fish
- leaves
what are the characteristics of an organism that eats high quality food (2)
- small or no stomach
- small intestine does not require much surface area
buccal cavity (4)
site of ingestion, feeding, and swallowing:
- tongue, chemoreceptors, salivary glands, saliva
buccal cavity: tongue
- aids to propel food through the pharynx and into the alimentary canal during swallowing
buccal cavity: chemoreceptors (taste buds) (2)
- signal to brain to start digestion
- detect quality of food
buccal cavity: salivary glands/saliva (3)
- mucus (lubrication, protect/buffer lumen lining)
- digestive enzymes
- toxins
pharynx (3)
- posterior to the buccal cavity
- many tetrapods lose slits during development, but are retained in fish
- many tetrapods have structure to prevent foods from entering larynx (epiglottis)
alimentary canal: esophagus
- muscular tube that transports food from pharynx to the stomach
aves: esophagus (2)
- contains crop used to store large amounts of food to be digested at a later time or regurgitated to feed their young
- lining of crop can produce nutritious substance (crop milk) that is regurgitated to feed young
alimentary canal: stomach (3)
- stores meal
- mechanically churns food to physically break it down into smaller pieces
- gastric glands secrete mucus, enzymes, and acid for chemical digestion
stomach: why is mechanical digestion necessary?
- increases SA to allow chemical digestion to be more efficient and accessible to enzymes
rugae
- folds in the stomach that can unfold to increase stomach volume for storage of food
mono-gastric stomach (2)
- single chamber stomach
- mechanical digestion generally due to muscular action
aves: stomach (3)
- two chambered stomach: gizzard and proventriculus
- proventriculus: produces acid and enzymes for chemical digestion
- gizzard: specialized grinding stomach, may contain sand or small stones
alimentary canal: small intestines (2)
- main site of chemical digestion of proteins, fats and carbohydrates
- major site of nutrient absorption
alimentary canal: anterior of SI (3)
- duodenum
- contains glands that produce alkaline secretions
- liver and pancreas produce secretions (bile, enzymes) into the duodenum
bile
- acts as an emulsifier: breaks globules of fat into smaller droplets, increasing SA for enzymes to act
what to the glands within the SI produce (2)
- enzymes
- mucus
what general structural features of the SI help to increase the total amount of nutrients absorbed (4)
- large surface area
- thin epithelium
- vascularization
- specializations that increase length of time spent in small intestine
how does the SI increase SA (2)
- plicae: circular folds in internal surface that are covered in microvilli; do not unfold (permanent)
- microvilli: tiny projections of the cell membrane
how many layers thicks is the epithelium of the SI
- one cell thick
small intestine: pyloric caeca (3)
- located at junction of stomach and duodenum
- sites of chemical digestion and nutrient absorption (not fermentation)
- internal surface contain villi and microvilli, increasing SA for nutrient absorption
small intestine: spiral valve (2)
- chrondrichthyes and sarcopterygii
- increases SA for digestion and absorption and slows passage of food through the intestine, increasing time available for digestion
how do vertebrates without spiral valves prolong digestion (2)
- small intestine length is greatly increased
- helps slow passage of food and increases SA
alimentary canal: microbial digestion (2)
- symbiotic microorganisms can digest some foods that vertebrate cannot produce enzymes for (cellulose; fermentation)
- some microorganisms produce vitamins as well
intestines: colic caecum (3)
- present at the junction between small and large intestines
- many aves have 2 colic caeca
- blind-ending chamber specialized for fermentation: contains enlarged SA and many microorganisms that digest cellulose
how do vertebrates that digest cellulose using fermentation in the caecum obtain nutrients from digested cellulose?
- release fecal pellets and eat them again to absorb cellulose nutrients
alimentary canal: large intestine (2)
- consolidates undigested material into feces for defecation
- water reabsorption from indigested material to avoid dehydration: from digestive glands, enzymes, mucus and other secretions
which large intestine would be larger: terrestrial tetrapods or freshwater tetrapods
- terrestrial tetrapods: conserving and retaining H2O is more important
coelom (2)
- created in space between splanchnic and somatic hypomere layers
- gives rise to major body cavities of adult body
peritoneum (3)
- continuous sheet of tissue/serous membrane that secretes lubricating fluid
- reduces friction to protect organs
- lines the pleuroperitoneal cavity/peritoneal cavity
