chapter21 Digestion Flashcards
What are the three dietary categories?
- Carnivores: Lions, Tigers
- Herbivores: Goats, Oxen, Sheep
- Omnivores: Humans, Bears
What are the types of feeding mechanisms?
- Bulk feeders: Eating large pieces of food:E.g Humans
- Filter feeders: Sifts small organisms and food particles from water: Whales
- Substrate feeders: Lives within the organism and eats the organism: E.g Maggots. Caterpillars
- Fluid feeders: Sucks nutrient rich liquid from the organism: E.g Mosquitoes, Bees
What are the 4 stages of food processing?
- Ingestion: Taking the food in
- Digestion: Breaking down the food to convert the food so that it can be absorbed
- Absorption: Absorb the nutrients
- Elimination: Repel the contents that cannot be digested
What are the 2 phases of digestion?
- Mechanical breakdown: Breaking down food to facilitate easy chemical breakdown and increase the surface area that enzymes touch
- Chemical breakdown(hydrolyses) is breaking down food (complex polymers) by enzymes to simple monomers so that they can be absorbed
What chemicals are proteins converted to during digestion?
Amino acids
What chemicals are complex sugars (poly saccharides and disaccharides ) converted to during digestion?
Mono sachcharides which are soluble in water.
Fructose, Glucose and Galactose
What chemicals are fats converted to during digestion?
Glycerol and fatty acids
What chemicals do nucleic acid converted?
Nucleiotides
What absorbs the nutrients?
Epitherlial tissue that lines the inside of the digestive tract
What are the 2 digestive processes that happens in the mouth?
Mechanical break down by teeth and chemical break down by the enzymes in saliva
How does intra cellular digestion happen?
- The food particle is trapped within a vacuole by phagocytosis (engulfs)
- The vacuole fuses with a lysosome that has digestive enzymes
- The digested food is absorbed through the vacuole membrane to the cytosol
What type of organisms digest food within the vacuoles?
Single celled organisms such as protists and sponges
What is a gastro vascular cavity?
Compartment within an organism with a singe entrance, the mouth to take food in and anus to expell food is the same opening.
E.g Hydra
How is food digested in the gastrovascular cavity?
- Cells lining the inside of the gastrovascular cavity secretes enzymes.
- These enzymes break down the food in to smaller particles
- The other cells lining the digestive tract engulfs these food particles. The food is trapped within vacuoles created by phagocytosis
- The digestion is complete within the vacuole
- Undigested material are expelled through the mouth
What is an alimentary canal?
A digestive tube extending from one opening that takes food inside (mouth) to another different opening that expells food (anus)
What are the differences between a gastrovascular cavity and an alimentary canal?
- The gastrovascular cavity has one opening (anus and mouth) where as an alimentary canal has 2
- Food travels only in one direction in a gastrovascular cavity, mouth to anus
- Because food travels in only one direction there are specialized areas in the alimentary canal that carries out food processing.
What are the different components of the alimentary canal?
- Mouth: Takes in food
- Pharynx: Directs food to the Esophagus
- Esophagus: Channels food to the stomach, Crop or gizzard
- Stomach, Crop or Gizzard:
a. Crop stores the food
b. Stomach and gizzard churns, mixes and chemically digests the food - Intestines: Chemically digests and absorbs food and water
- Anus : expells the food
What are the components of an earthworms alimentary canal?
Mouth->Pharynx->Esophagus->Crop->Gizzard->Intestine->Anus
What are the components of a grass hoppers alimentary canal?
Mouth->Esophagus->Crop->Gastric pouches->Midgut->Hindgut->Anus
What are the components of a birds alimentary canal?
Mouth->Esophagus->Crop->Stomach->Gizzard->Intestines->anus
What is the advantage of an alimetary canal over gastrovascular cavity?
Alimentary canal has specialized regions where digestion can take place and hence digestion is more efficient
What are the 7 primary organs of the human digestive system?
- Oral cavity
- Esophagus
- Stomach
- Small intestines
- Large intestines
- Rectum
- Anus
What are the structures that assist digestion?
- Salivary glands
- Gall bladder
- Liver
- Pancreas
If you swallow food while upside down would food go to the stomach? Why?
Yes, Food is pushed one way through the alimentary canal by peristalsis, a alternate waves contraction and relaxation of smooth muscles that lines the inside of the alimentary canal
What regulates food in and out of the stomach?
Muscular ring like valves called Sphincters opens and closes the passageway to the stomach to keep the food inside it (2-6 hours) log enough to digest the food.
What are the functions of the teeth?
- Incisors: Break
- Canine: Kill and rip
- Pre Molar: Grind and crush
- Molar: Grind and crush
What are the functions of the tongue?
- Detect taste triggering secretion of saliva
- Break and mix food
- Direct the food to the pharynx during the course of swallowing by shaping the food in to a ball (Bolus)
What are the functions of saliva?
- Lubricate the food so that it is easy to swallow and protect the inside lining of the mouth
- Buffers in saliva neutralizes the acids in food preventing it from harming the teeth
- Antibacterial agents kill many bacteria on food
- Contains the enzyme Amylase that breaks down the polysaccharides to disaccharides
What are the 2 openings in the pharynx?
Esophagus and Trachea
What is the function of the epiglottis?
When the swallowing reflex happens the epiglottis closes the entrance to the Trachea so that food can go down the Esophagus
What prevents food from coming out once it enters the Esophagus from the Pharynx?
A muscular valve called Esophagal Sphincters closes once the bolus enters the Esophagus so that peristalsis can push the food down
What happens if food accidentally enter the larynx (voice box) by the incorrect positioning of the epiglottis ?
The Epiglottis opens up the trachea and a strong cough reflex is triggered
What is the function of the stomach?
- Mix and breakdown food
- Break down proteins (break large polypeptides to small polypeptides) by secreting the enzyme pepsinogen
- Secretes HCL (Hydro Chloric Acid) to convert pepsinogen in to pepsin that truly digest proteins
- Stores the food for 2-6 hours till the food is digested
How does the stomach produce pepsin?
- Pepsinogen and HCL are produced by gastric glands ans is secreted in to the stomach
- Reacting with HCL pepsinogen is converted to pepsin
- Pepsin in turn helps activate more pepsinogen to produce more pepsin
The produced pepsin is used to digest proteins
How does the stomach protects itself from being digested by pepsin and being eroded by the HCL that is secreted?
- Gastric glands get activated and secretes enzymes only when food is present in the stomach. So the enzymes dont directly touch the stomachs internal surface
- The cells that get eroded gets replenished quickly
- The gastric glands secretes only pepsinogen which is not reactive with proteins to protect stomach tissue. The glands then secrete HCL to activate the reaction that converts pepsinogen to pepsin. This happens only when food is present
What triggers the secretion of gastric juices that contains the enzymes?
When food smell or taste is sensed the brain sends a signal to the stomach tissue that secretes a hormone called gastrin that activate the stomachs soft muscular tissues to contract and relax giving hunger pangs or rumblings of the stomach. Also gastrin stimulates the glands that secrete gastric juices
What stops gastric juices from being secreted?
When the stomach is too acidic gastrin secretion is inhibited and hence will reduce the secretion of gastric juices
What is a chyme?
An acidic broth of food partially digested and broken down by the stomach ready to enter the small intestines
What are the 3 major sections of the small intestines and what are their major functions?
- Duodenum: Completely chemically digest the food
- Jejunum: Absorb the nutrients
- Ileum: Absorb more nutrients
Describe the chemical reactions that happens at the duodenum and related enzymes that participate in the process?
- Polysaccharides - (Pancreatic amylase)->Maltose and other disaccharides -(Matase, sucrase, lactase etc) -> Monosaccharides
- Polypeptides -(Trypsin, Chymotripsin)-> Smaller polypeptides - (various peptidase)-> Amino acids
- DNA and RNA -(Nucleases)->Nucleotides -(other enzymes)-> Nitrogenous bases, sugars and phospates
- Fat globules -(Bile salts)-> Fat droplets -(Lipase)-> Glycerol and Fatty acids
What produces bile and what stores bile?
The liver produces bile and the gall bladder stores the bile
How does gall bladder stones form?
Crystallized bile slats
What is the function of the pancreas in digestion?
Produce panceatic juices that
- Has Amylase enzyme that digests complex sugars (poly saccharides)
- Contains an alkaline that neutralizes the acidity in Chyme
- Contains Lipase that digests fat droplets
- Contains Trypsin and Chymotrypsin that digests polyopeptides
What is the function of the bile?
- Contains bile salts that breaks down fat globules that are not soluble in water in to smaller fat droplets to increase the surface area where the enzymes can act on
(think of it as a soap or emulsifier)
What is the enzyme that breaks down Fat droplets to Glycerol and Fatty acids?
Lipase secreted by the pancreas
What are the enzymes that breaks down polypeptides to amino acids?
Trypsin, Chymotripsin, Peptidases
Where is maltase, sucrase and lactase synthesized?
In the intestinal wall of the duodenum. These enzymes help digest polysaccharides
Where is nuclease produced?
In the intestinal wall of the duodenum (small intestine). Nucrease helps break down DNA to nucleotides
How are the small intestines structurally made to absorb nutrients?
To increase the surface area of absorption the internal wall of the small intestines have
- Folds
- Villi which are tiny projections on the intestinal wall
- Micro villi tiny projections on villi which further increases the surface area
How do nutrients get to blood?
They are transferred to blood vessels via diffusion or pumped against the concentration gradient by active transport through the epithelial cells and the to the blood in the capillaries (amino acids and sugars) and lymph vessels (Glycerol and fatty acids) in the small intestines
Where is this nutrition rich blood then transported?
To the liver
What transports blood from small intestines to the liver?
Hepatic portal vein
What is the function of the liver in food digestion?
- Converts excess glucose to glycogen to be stored in the liver cells. Liver by doing this controls the level of metabolism
- Synthesizes many essential proteins
- Removes excess calories and converts it to fat to be stored for later use
- Converts toxins such as alcohol and drugs to inactive substances that can later be removed by urine
What is the purpose of the large intestines?
Absorb water and compact feces
What is the cecum?
A pouch at the location where small intestines empties in to the large intestines
What is the appendix?
A small finger like projection of the Cecum that contains a mass of white blood cells. This organ contributes minimally to immunity
How does appendicitis occur?
A bacterial infection of the appendix that is causes by the blockade of Cecum and appendix
What is the colon?
Large portion of the large intestines that absorb the water that the small intestines could not
Also colon hosts some bacteria which produces Vitamins B and K which is later absorbed by the colon
What are feces?
Waste of the digestive system
What does feces consist of ?
- Undigested material
- Cellulose
- Procaryotes that live in the colon
How long does it take food to travel the colon?
About 24 hours
Why is it important to take Vitamin B and K after taking antibiotics?
When the antibiotics kill the harmful bacteria it also kills the good bacteria in the colon that produces vitamin D and K. So it is necessary to supplement
How does diarrhea happen?
When the colon is not functioning properly to absorb all the water in the feces, feces moves fast through the colon
How does constipation occur?
When feces move too slowly through the colon excess water is absorbed. Feces moves too slowly because there is not enough plant matter in the feces
What is the final portion of the colon and what is its function?
Rectum and Rectum stores the feces
How is expelling feces regulated?
By a voluntary sphincter and an involutary sphincter. When the voluntary sphincter is open feces is expelled by peristalsis that results in defacation
Describe the adaptations of the vertebrate alimentary canal based on its diet?
- Carnivores have large expandable stomachs to store lots of food because they can go without food for a long time. Therefore they need to eat a lot in one sitting
2.Longer alimentary canal in herbivores and omnivores to digest plat matter that is more difficult to digest than flesh - Specially large pouches to host cellulose digesting bacteria and protists
E.g. Horses and Koalas have a large Cecum that hosts bacteria that breaks down cellulose
4.Some animals like rabbits eat their own feces to recover the cellulose digesting microbes lost during defalcation
What are ruminants?
Animals like cattle, sheep and deer
Ruminants have 4 partitions in the stomach each partition containing microbes that digest the food. Ruminants regurgitate food to move food from one partition to another
What are the advantages of a long alimentary canal?
- Increase surface area for nutrient absorption
2. Increase time to process difficult to digest material
