Digestive System Flashcards
2 types of digestive system invertebrates have
- simple
- Alimentary
4 types of vertbrate digestive systems
- Monograstic
- Avian
- Ruminant
- Pseudo-ruminant
Simple digestive system
1 opening - gastrovascular cavity where the mouth is the anus.
How do simple digestive systems work
Cells within the vacity secrete digestive enzymes that breakdown the food. The food particles are engulfed by the cells lining the gastrovascular cavity
Alimentary Canal
2 openings
Mouth for ingestion
Anus for elimination
Digestive system of Jellyfish
Simple
Digestive system of Earthworm
Alimentary canal
how do alimentary canals works
- Food passes through the esophagus
- its stored in the crop
- then passes through gizzard where it is churned and digested
- then passes through the intestine where nutrients are absorbed
- waste is eliminated as castings through the anus
What digestive system do rabbits have
Monograstic single-chambered stomach
How and why are rabits digestive system dif to humans
Rabbits are herbivorous (consume more cellulose) therefore have a much longer GI tract and double cycle.
Large cecum which contains lots of microbes to break down tough fibre
What kind of digestive system do birds have
Avian
How is birds mechanical digestion different
Birds do not have teeth as an adaptation for flight, and therefore have a different system of manipulation of food
Function of gizzard in birds
Crush food into smaller pieces instead of teeth
What digestive system do cows have
Ruminant
How do cows diet differ from humans
Quality and quantity - huge amounts of plant material
How do cows digestive system differ from humans
No upper incisor teeth as only chew plant material. The stomach is four-chambered to breakdown large amounts of cellulose and ferment ingested.
Alpaca digestive system
Pseudo ruminants
What are pseudo ruminants
3 chambered stomach - lacks a rumen
Cecum
The pouched organ at beginning of large intestine; contains microorganisms necessary for the digestion of plant materials; is large & is where roughage is fermented and digested
Function of saliva
- contains mucus that moistens food and buffers pH of food
- Containts immunoglobins and lysozomes which have antibacterial action to reduce tooth decay
- contains enzymes amalyse and lipase
Function of salivary amalyse
Convert starches into disaccharide
Function of lipase
Produced in the tongue and breaks down triglyceride
Function of tongue
Assist in swallowing and food manipulation, moves bolus from mouth into pharynx
What does the pharynx open into
2 passageways
- oesophagus leading to stomach
- trachea leading to lungs
Epiglottis function
When swallowing, epiglottis closes the glottis and food passes into the esophagus and not the trachea
Function of esophagus
Softened food passes through the esophagus after being swallowed
Structure of esophagus
Tubular organ connecting mouth to stomach
How does the esophagus work
Smooth muscles of esophagus undergo peristalsis (unidirectional, involuntary reflex)
What is the gastro-esophageal sphincter
Located stomach end o esophagus in most mammals but not humans
- prevents contents of stomach from travelling up the esophagus as it remains closed when there is no swallowing actions.
Structure of stomach
Sack-like organ that secretes gastric digestive juices and can expand ~20x when filled with food
Where is the primary site of protein digestion
stomach
2 processes occurring in the stomach
Chemical Digestion and Muscular activity
Chemical digestion in the stomach (2 things)
Pepsin is secreted by chief cells in the inactive form of pepsinogen. Pepsin can break up proteins into smaller polypeptides
Parietal cells sercete hydrogen and chloride ions, which combine in lumen to form HCL (primary acidic component)
Two functions of HCL in the stomach
Convert inactive pepsinogen to pepsin (for protein digestion)
Highly acidic enviornment kills many microbes and aids in hydrolysis of protein
Muscular activity in the stomach
Churning action of stomach muscles by contraction and relaxation mixes contents ~every 20 min
Chyme
Partially digested food and gastric juice mixed
When does gastric emptying occur
2-6 hours after a meal
Function of pyloric sphincter
Regulate small amounts of chyme at a time into the small intestine
Why doesn’t the stomach digest itself
- thick mucus lining to protect underlying tissue
- saliva contains mucus which buffers mouth pH, and immunoglobins and lysosomes which reduce tooth decay
How is chyme neutralised in the lower intestive
Rich alkaline solution (bicarbonate) in pancreatic juices neutralises the acidity
Function of small intestine
Main site of protein, fat, and carbohydrate digestion
Adaptation of small intestine
Enormous surface area because its a
- highly folded surface containing villi
- each villi contains many microvilli
All these folds increase surface area THEREFORE increase absorption efficiency of nutrients
How is nutrients absorbed from the small intestine
Bloodstream are right in the villi for efficient nutrient absorbtion
Function of bile
Our body is primarily water therefore we need bile to specifically attack fat components so they can diffuse into the blood
FAT DIGESTION
Structure of duodenum
C-shaped fixed part of the small intestine - beginning of the small intestine
What is bile and where is it produced
Bile contains lipid emulsifying bile salts and is stored and concentrated in the gallbladder
What occurs in the duodenum
The bulk of chemical digestion where digestive juices from the pancreas, liver, and gallbladder enter.
Absorbtion of fatty acids therefore occur here as bile is introduced
Jejunum
2nd part of small intestine where nutrient hydrolysis continues and by this time most of the carbohydrates and amino acids are absorbed.
Ileum
3rd part of the small intestine
- bile salts and vitamins absorbed into bloodstream
- undigested food is sent to colon via peristalsis
Function of gallbladder
Store and concentrate bile for fat digestion
Structure of large intestine
Wider and shorter than small intestine, however length and proportion varies greatly according to diet of different mammalls
Colon
The main part of the large intestine
Home to many bacteria to aid digestive processes
Site of water, salt, and mineral extraction
What mainly occurs in large intestine
Water comes out of stool so that we don’t lose water
What is the rectum
Terminal end of large intestine
Function of rectum
Store feces until defecation
How is waste eliminated
Feces are propelled out the anus using peristaltic movement of smooth muscle.
3 things we need from food
- organic building blocks
- chemical energy
- essential nutrients
What are organic building blocks from food
Material to build DNA for reproduction, growth, and maintenance of our body
What is chemical energy from food
Source of material for ATP production in cells
What are essential nutrients
Minerals and vitamins required for cellular functions that we cant synthesise ourselves
4 essential nutrients
Amino acids
Fatty acids
Vitamins
Minerals
How do we obtain essential nutrients
Feeding on plants or other animals - some animals can get vitamin C rom dies, whereas most have the ability to synthesise it from other nutrients
What are amino acids and how many are there
There are 20 amino acids which are the building blocks of protein
Why do we need amino acids/proteins
Structure, function, and regulation of tissues and organs
Can animals synthesize amino acids
Most animals have the enzymes to synthesize half the amino acids (as long as the diet includes sulfur and nitrogen)
What are essential amino acids
Amino acids we don’t make and therefore need to consume
How many amino acids do adult humans require from their diet
8 amino acids
Why do human infants need histidine but not adults
Histidine is important for growth, repair of damaged tissue, and making blood cells but human infants are unable to synthesize.
What source gives u all 8 of the amino acids you need
Animals/meat
What does it mean that proteins from plants are incomplete
Every plant is deficient in one or more amino acids
How do vegetarians obtain all the essential amino acids if plants are incomplete
Eating a varied diet of plant proteins
Anabolic amino acids meaning
Can build them yourself
Why do we need essential fatty acids
Variety of cellular processes - in membrane linings, signalling molecules, and also stored for when we need to deploy energy
Can humans produce linoleic acid
No, humans lack the enzyme to form the fatty acid so it must be consumed
How do we get essential fatty acids
Must be obtained by diet
What are vitamins
Organic molecules required in the diet in small smounts
How many vitamins do humans require
13
Vitamin C
A water soluble vitamin required for production of connective tissue
Vitamin D
Fat-soluble vitamin that aids in calcium absorbtion and bone formation
Scurvy
Serious vitamin C deficiency
How might a vitamin d deficiency occur
Lactose intolerance, vegan diet, lack of sun exposure
Overdose of water soluble vitamins
Harmless because excesses are excreted in urine
Overdose of at soluble vitamins
Fat-soluble vitamins are deposited in body fat, so overconsumption can cause them to accumulate to a toxic level
Vitamin K
Important for blood clotting, produced by microbiome or can be available from diet
Why are babies given a vitamin K shot at birth
Less bacteria in the gut where vitamin K is made and they do not recieve enough from mothers
Why is it important for people of blood thinners to maintain a constant level of vitamin K in diet
blood thinning medication reduces risk of blood clots which is the opposite action of vitamin K. Must maintain balance of medication otherwise blood will become too thin
Minerals
Inorganic nutrients (iron and sulfur) are required in small amounts.
Why do we need iron
Incorporated into the oxygen carrier of blood (haemoglobin)
Iodine function
regulate metabolic rate
Calcium function
Build and maintain bone
What mineral do humans often consume in excess and why
Sodium - flavours food and is used as a preservative. Over indulgence generally means we exceed daily dose
What does overconsumption of sodium cause
High blood pressure, health disease, stroke, and calcium loss
Why do humans need sodium (3 reasons)
- Conduct nerve impulses
- Contract and relax muscles
- maintain the proper balance of water and minerals
How does the type and quantity of 4 essentials of food vary between species
Every animal needs Minerals, vitamins, amino acids, and fatty acids to survive, but how they do it and what they need specifically varies between animals
What are carbohydrates
Long chains of sugar molecules that are mainly used for energy
what are the three types of carbohydrate
Monosaccharide, disaccharide, polysaccharide
Monosaccharide
Single sugar - fructose, glucose, galactose
Disaccharide
(simple sugars, 2 sugars linked together) - sucrose, lactose, maltose
Polysaccharides
Complex carbohydrate - many sugars linked together including starch, glycogen, fibre
What carbohydrate does salivary amylase break down and where
Salivary amylase breaksdown food starches, Polysaccharides, into maltose, a disaccharide
Where does carbohydrate digestion mainly take place
Duodenum
What enzymes break down disaccharides into monosaccarides
Maltase, sucrase, lactase, which are in the intestinal wall
Why are complex carbohydrates better
Take longer to digest and therefore have a more even dispersion of energy
Function of Sucrase
Break down sucrose into glucose and fructose
Function of lactase
break down lactose into glucose and galactose
Function of glucose
Used in metabolic pathways to harness energy
Where is glucose stored and in what form
Store in liver and muscles in the form of glycogen
Where is excess glucose store
As fat - good for hibernating animals so they can break down fat stores instead of protein (muscle loss)
Function of insulin
Essential hormone that helps bodyturn food into energy and control blood sugar levels
Diabetes
Body cant produce enough insulin or its defective
Pepsin breaks ___ into ____
Pepsin breaks proteins into peptides
What is a peptide
Short chain of 4-9 amino acids
Function of peptidase
Breakdown peptides into single amino acids so they can be absorbed into the bloodstream
Where does the bulk of lipid digestion occur
Small intestine
How does bile aid in digestion of lipids
Emulsification
Emulsification
Large lipid globules broked down into smaller lipid globules reducing aggregations and increasing surface area
Function of lipases
Breakdown lipids into fatty acids and glycerides
Adipose tissue
Connective tissue consisting mainly of fat cells
Function of adipose tissue
Specialised to synthesize fat and contain large globules of fat, within a structural network of fibres under the skin, in between muscles, and around the heart
How do fat stores benefit ectotherms
If ectotherms are not active/eating, they use fat stores to maintain energy
4 types of feeders
Filter feeders, substrate feeders, fluid feeders, bulk feeders
Dentition
Different diets (carnivores vs herbivores) have different adaptations for obtaining and manipulating food
