Digestive System Flashcards
What is intestinal juice?
Juice secreted from small intestines lining that contains digestive enzyme capable of finalizing the digestion of carbs, proteins, and lipases.
E.g. peptidases: break down peptides into amino acids
sucrase: breakdown sucrose, lactose and maltose into glucose, galactose and fructose
lipases: breakdown lipids into fatty acids and glycerol
What do ribonuclease and deoxyribonuclease do?
Digest RNA and DNA
What do lipases do?
Break down fats into fatty acid and glycerol
What do amylase do?
Break down starch into the disaccharide maltose
What does trypsin/protease do?
Splits proteins into peptides
What is the jejunum?
Middle section of the small intestine. It’s lining allows for effective absorption of carbs and proteins.
What are the six functions of digestion?
-ingestion
-mechanical digestion
-chemical digestion
-movement of food along alimentary canal
-absorption of food and water into lymph and blood
-elimination of material that is not absorbed
Define digestion
The mechanical and chemical breakdown of food into smaller molecules that can be absorbed into the body
What is diarrhoea?
Frequent defecation of watery faeces cause by the irritation of small/large intestines which in turn speeds up the process of peristalsis.
Can be caused by: a bacteria, virus, parasite, cancer, lactose intolerance
What is constipation?
A condition in which defecation becomes difficult/painful with faces being hard and dry due to a long time period of sitting in the large intestine and it’s water being absorbed.
Can be caused by: lack of roughage in diet from plant matter (insoluble fibre/cellulose), emotional problems, lack of exercise
What is the importance of soluble fibre in a person diet?
Found in food derived form plants, soluble fibre has been linked to, low cholesterol, low risk of heart disease and cancer
What is excretion?
Removal of wastes of metabolism from the body
How is the small intestine well suited to absorption?
6-7m long
-large SA:V ratio due to villi and microvilli
-highly vascularised (lots of capillaries) allowing for higher absorption of nutrients
-segmentation which brings food to villi
-absorbs 80% of all nutrients in the internal surface
Function of the oesophagus
23-25 cm long
Links the pharynx to the stomach. Aids in transporting food from the throat to the stomach in a wave like motion known as peristalsis
Function of the epiglottis
Flap situated in the back of the throat closing over the trachea in order to prevent food or water from entering the lungs
Function of the cardiac sphincter
Stops acid reflux from occurring. Acts as a covering to prevent acid contents from the stomach getting into the oesophagus
What is chyme?
Semi-fluid mass of partially digested food that leaves the stomach.
What is mucosa?
Lining of the stomach containing cells specialized for secreting gastric juice and mucous.
What is chemical digestion?
Breakdown of food into smaller molecules by chemicals/enzymes
mouth- salivary amylase
stomach- pepsin
small intestine- pancreatic juice: amylase, protease, lipases, nucleases
intestinal juice: lipases, amylase, peptidases
What is mechanical digestion?
The physical breakdown of food into smaller molecules
- increase SA
- increase efficiency of chem digestion
Explain chemical digestion in the mouth
Food is mixed with saliva secreted into mouth cavity via the salivary glands. It contains mucous to lubricate as well as salivary amylase which digest starch into disaccharide maltose.
Explain mechanical mouth digestion
-ingestion
-food is broken down into smaller molecules by chewing, tearing, etc
-Tongue shapes food into bolus
What are the types of teeth?
- canines (2)
- molars (6)
- premolars (4)
- incisors (4)
What is a bolus?
A lump or ball like structure of food and saliva
Explain chemical digestion in the stomach
-enzymes in gastric juice (pepsin) secreted by mucosa
-break down amino acid bonds of protein=polypeptides
-breaks down nucleac acids into RNA and DNA
Why is absorption of nutrients into the bloodstream not possible in the stomach?
The internal surface is covered by a thick layer of mucus (mucosa)
Explain mechanical digestion in the stomach
Achieved by waves of muscular contraction that move along the stomach wall.
-conversion in a variety of ways due to 3 muscles (oblique. longitudinal, circular)
-Food is churned and mixed with acidic juice to form chyme.
Function of the ileum?
Last part of the small intestine.
- absorbs vitamin B12, bile salts and remaining products of digestion
Function of the gall bladder
Stores bile and releases it into the small intestine where bile emulsifies lipids
How is each nutrient absorbed in the body?
Fatty acids and glycerol: simple diffusion (recombine to form fat droplets, enter lacteal)
Water: diffusion (absorbed into blood capillaries)
Simple sugars (glucose): active transport (pass through cells on villi, into blood capillaries)
Amino acids: active transport (into blood capillaries)
Ways that the villi absorbs nutrients
-active transport (ATP is used to take in nutrients against a concentration gradient)
-simple diffusion (higher concentration of nutrient materials in interior than in cells of villi)
-continual muscular movement of intestinal wall (contact)
What are villi?
Projections from the internal lining of the small intestine who’s structure is well suited to nutrient absorption.
-single cell layering
-contain lymph capillaries (lacteal) which link to the blood vessels
How does digestion occur in the small intestine
Mechanical:
Secreted in via bile duct. Contains no digestive enzymes but is important in emulsifying fats to increase their surface area on which the lipases can act.
Chemical (pancreatic juice):
Enters duodenum secreted by pancreases via the bile duct. It neutralizes acid contents in the stomach and contains digestive enzymes: amylase, trypsin(protease), lipases, and nucleases
Chemical (intestinal juice):
Secreted from lining and contains enzymes that complete digestion of carbs, proteins, and lipases. Contains digestive enzymes: peptidases, sucrase, lactase, maltase, lipases
Digestive enzymes and their products:
Sucrase-sucrose into monosaccharide glucose
Lactase- lactose into fructose
Maltase- maltose into galactose
Amylase- starch into disaccharide maltose
Trypsin (protease)- proteins into peptides
Peptidases- peptides into amino acids
Lipases- fats into fatty acid and glycerol
Nucleases- digest RNA and DNA
What is segmentation?
Contraction of circular muscles that narrow small intestine’s lumen to breakup chyme
What are accessory organs?
Organs not a part of the GI tract that deposit enzymes into it
e.g. pancreas, salivary glands, tongue, liver, gall bladder
What is the pyloric sphincter?
Thick circular muscle at the base of stomach preventing digested food from going back into stomach from the small intestine.
What is peristalsis?
Waves of muscular contractions that push food further down the alimentary canal.
(successive bands of circular muscles contract in the oesophagus)
What is the GI tract?
Gastrointestinal tract. The direct link between all organs
What is the duodenum?
25cm long
-first section of the small intestines, curving around the pancreas
-most chemical digestion occurs here before chyme moves further along the intestine
Functions of the lymphatic system
-return lymph fluid to the circulatory system
-collect excess fluid (lymph) from tissue
-absorb fats from digestive system
-destroy infecting micro-organisms by phagocytic cells (phagocytosis-solid)
-filter the lymph for foreign cells
Function of a lymph node
Involved in the protection against infection
What occurs due to a build of of fluid in tissue (lymph wise)?
-returned to blood by lymphatic system
-lymph vessels are blind-ended tubes which means the system is a one way system carrying fluid away from tissue
-lymph capillaries are larger than blood vessels which allows for easy passage of micro-organisms
What is coeliac disease?
An intolerance to gluten
-caused by inheritance
-gluten is found in wheat, rye, barley
-If gluten is eaten, their immune system responds by damaging or destroying villi in the small intestine
-causing malnourishment
What is bowl cancer?
-also called colorectal cancer
-uncontrolled growth of cells in the large intestine’s wall
-a high red meat diet with low fruit may cause this
