Digestive System 1 Flashcards
8 key functions of the digestive system
Ingestion
Mastication
Propulsion
Mixing
Secretion
Digestion
Absorption
Elimination
Role of ingestion
Bringing food to the stomach
Role of mastication
Chewing
Role of secretion
For lubrication, liquification, digestion
Role of absorption
Movement of molecules into cells and circulation
Role of elimination
Removal of waste products
Role of digestion
breakdown of molecules into their constituent parts
What are the 2 forms of digestion
Mechanical and Chemical
What is mechanical digestion?
Physical disruption of food into smaller parts - chewing food
What is chemical digestion?
- Breaks down food into small soluble constituents
- Reliant on enzymes
- Some enzymes produced by the body some are produced by commensal bacteria
What are the 4 segments of the gastrointestinal tract
- Mucosa
- Submucosa
- Muscular layers (Tunica muscularis)
- Serosa / adventitia (smooth tissue membrane)
Function of the mucosa
absorption
Function of the submucosa
support
Function of the tunica muscularis
Propels and moves substances along the tract
Function of the serosa / adventitia
movement of the tract
What is peristalsis
The method that allows the movement of substances along the tract, by contraction of muscles
What mechanical digestion takes place in the mouth / oral cavity?
- Chewing / mastication
- Physical break up of food
What chemical digestion takes place in the mouth / oral cavity?
- Saliva from salivary glands contains salivary amylase for carbohydrate digestion
What is starch broken down into
Starch —-> maltose + isomaltose
What are the 3 sets of salivary glands called?
1) Parotid
2) Sublingual
3) Submandibular
Location of parotid gland
Beside the ear
Location of sublingual gland
below the tongue on the floor of the mouth
Location of submandibular gland
Below the jaw
Oesophagus function
Transports food from pharynx to stomach
Oesophagus structure
Outer longitudinal muscle and inner circular muscle
Mechanical digestion functions of the stomach
- Churning and mixing of food
- Increases contact between enzymes and digesta
3 Chemical digestion functions of the stomach
- Pepsinogen - breaks down protein
- Hydrochloric acid - break down protein and absorb essential nutrients
- Rennin / Chymosin - helps control blood pressure and maintain healthy level of sodium and potassium in the body.
Fermentation function in the stomach
Rely on bacteria, fungi and protists to break down food
What are the 3 muscle layers of the stomach?
Outer - longitudinal
Middle - circular
Inner - oblique
What are rugae?
Wrinkles in the stomach.
Present in an empty stomach, disappear when bloated.
What are ruminants stomach?
The stomach of cows, sheep, goats.
Have 4 chambers for specialised cellulose digestion, to break down cellulose.
Cellulose is broken down by the enzyme cellulase.
Fungi, bacteria and protozoans produce cellulase.
Functions of chief cells.
1) Produce pepsinogen
2) produce rennin/ chymosin
What are mucosa?
Mucus secreting cells
Simple columnar epithelium with gastric pits
Functions of parietal cells
1) produce Hydrochloric acid
2) Intrinsic factor
Function of pepsinogen
- Break down protein into smaller peptides
Function of rennin/ chymoin
- coagulate milk
- important in very young babies
Function of Hydrochloric acid
- minor digestive effect
- maintains acidity
- kills ingested bacteria
What molecule is Intrinsic factor and what is its function?
- glycoprotein
- binds to vitamin B12
Function of the rumen
- Receives swallowed food - holding and fermentation vat
- Food can be regurgitated, remasticated, reswallowed
Structure of the rumen
fluffy fibrous fibers
Distinctive papillated mucosa
Reticulum function
- Small accessory chamber
- Contracts to slosh chyme between itself and rumen
Reticulum structure
‘Honeycomb’ structure mucosa
Omasum structure
Epithelium folded into laminae
Omasum function
Pumps food into abomasum
Abomasum function
Enzymatic digestion, highly acidic
Abomasum structure
Distinctive simple columnar, glandular epithelium
Ruminoreticula groove
Mill bypasses rumen via ruminoreticula groove
Closes into tube connecting oesophagus to omasum
Liver function
produces and secretes bile
Gall bladder function
Stores bile and secretes it to the digestive tract
- releases it into the duodenum during meals
What are the 4 anatomical lobes of the liver
Right lobe, left lobe, quadrate lobe, caudate lobe
Structure and location of the gallbladder
Pear shaped sac under right lobe of liver
What is the function of the pancreas
Produces most of the digestive enzymes in the small intestine
- Proteolytic enzymes e.g. trypsin, carboxypeptidase
- Nucleic acid enzymes
- Pancreatic amylase - for polysaccharide digestion
Name the 3 parts of the small intestine
Duodenum, Jejunum, Ileum
How is the small intestine involved in chemical digestion?
Secretes pancreatic juice
Secretes bile
Secretes intestinal juice
What does the small intestine absorb?
- Proteins
- Carbohydrates
- Fats
What is the structure of the duodenum?
C - shaped and encircles pancreas
Function of the jejunum and ileum
enzymes –>
Disaccharidases = disaccharides–> monosaccharides
Peptidases = peptide chains –> amino acids
Nucleases = DNA –> bases
Function of microvilli in the jejunoileum
Increase surface area allowing more nutrients to be absorbed
Structure and function of the mucosa of the small intestine
The mucosa is lined with villi and highly folded
The cells lining the villi contain microvilli
Allow an increased surface area for absorption of protein, carbohydrate and fat
Does the amount of nutrient absorption increase or decrease as you approach the large intestine.
Decreases
What is midgut fermentation
Cellulose digestion by commensal bacteria in the ascending colon
What is the function of smooth mucosa in the intestinal glands - (no villi)
Allows:
- Absorption of salts
- Absorption of water
- Fermentation of complex carbohydrates
- Excretion of faeces
Functions of the rectum
Pelvic part of GI tract
Supports and stores faecal mass before defecation
Function of the anus
Build up of pressure against walls causes internal sphincter to relax, open and allow faeces into canal
Relaxation of external sphincter allows defecation
