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.