Human Nutrition Flashcards
Nutrition: definition
The way an organism obtains and uses its food
Autotrophic: definition
A type of nutrition where an organism makes its own food. eg. certain plants
Heterotrophic: definition
A type of nutrition where an organism cannot make its own food.
Herbivores: definition
Animals that only feed on plants. eg. rabbits
Carnivores: definition
Animals that only feed on other animals. eg. fox
Omnivores: definition
Animals that feed on plants and animals. eg. badger
Digestion: definition
The physical and chemical breakdown of food into soluble particles small enough to pass into the body’s cells.
Why do we need digestion?
To break down large food particles until they are small enough to pass into body cells.
Why do we need a digestion system?
- Food can be digested in a single location
2. Individual cells do not have to contain all the digestive enzymes.
What are the four stages in human nutrition?
Ingestion
Digestion
Absorption
Egestion
Ingestion: definition
Food is taken into the alimentary canal
Digestion: definition
Food is broken down into smaller soluble pieces
Absorption: definition
The movement of digested food from the alimentary canal into the blood system
Egestion: definition
Removal of unabsorbed material as faeces
What is the role of the mouth in the digestive system?
- Physical/ mechanical digestion by chewing action of the teeth.
- Results in smaller particles, easier to swallow and greater surface area for digestion
Name the four types of teeth.
- Incisors
- Canines
- Premolars
- Molars
What do incisors do?
- Sharp edges
- Cuts, slices and bites
What do canines do?
- Long and pointed
- Grip, stab and tear food
What do premolars do?
- Have cusps
- They crush and chew food
What do molars do?
- Large teeth at the back
- Crush and chew food
What is the human dental formula?
-32 teeth in a full set of human permanent teeth.
What is the human dental formula for a human adult?
2( i 2/2 c 1/1 pm 2/2 m 3/3)
Does chemical digestion take place in the mouth?
Yes it does-
due to the presence of the enzyme amylase
Describe saliva.
- Secreted by 3 pairs of salivary glands
- Consists of water, salt, mucous, amylase and lysozyme
What does lysozyme do?
Helps kill micro-organisms
What is the function of the oesophagus?
-Carries food from the mouth to the stomach
How is the movement of food assisted down the oesophagus?
- By mucous (saliva and produced by wall of oesophagus)
- Peristalsis
What is peristalsis?
An involuntary wave of muscular contraction
What does the stomach do?
Breaks food mechanically, mixes food with gastric juice, forces chyme into the small intestine.
What does the small intestine do?
-Forces food backwards and upwards- helps absorption
What does the large intestine do?
-Pushes undigested waste (faeces) into the rectum.
What is the role of fibre in the diet?
- Consists of cellulose which humans cannot digest
- Fibre stimulates peristalsis
- Diet high in fibre reduces the risk of colon cancer as wastes are moved quickly through.
Describe the stomach.
- Muscular bag
- Stores and digests food
- Lining of stomach wall is heavily folded
- Secretes gastric juice
What does mucous do in the stomach?
- Coats the stomach
- Prevents self digestion
What is pepsinogen?
- Inactive enzyme
- Made active in the stomach due to low pH
- Breaks down proteins into peptides
What is the pH of hydrochloric acid?
pH 1 to 2
Very acidic
What does the acidity of the stomach do?
- Kills bacteria
- Loosens fibrous and cellular foods
- Activates pepsinogen
- Denatures amylase from saliva
What is chyme?
Food + gastric juices
How does chyme leave the stomach?
In small amounts when the pyloric sphincter opens
How is self digestion prevented?
- Mucous is alkaline and neutralises acid by the stomach wall
- Pepsin is released as inactive pepsinogen
- Cells that line the stomach can be replaced rapidly
What substances does the pancreas produce?
- Insulin
- Pancreatic juice
What does pancreatic juice contain?
- Sodium bicarbonate salt
- Amylase and lipase
What is the purpose of the sodium bicarbonate salt produced by the pancreas?
Neutralises chyme
What carries the pancreatic juice to the duodenum?
The pancreatic duct
Name some functions that the liver completes.
- Makes bile
- Detoxifies the body
- Breaks down excess amino acids
- Converts glucose to glycogen for storage
- Converts excess carbohydrate to fat
- Stores vitamins and stores minerals
Describe bile.
- Partly formed from the remains of red blood cells
- Yellow green viscous liquid
- Consists of water, bile salts and bile pigments
- No enzymes
Where is bile made?
The liver
Where is bile stored?
The gall baldder
How does bile get to the duodenum?
The bile duct
What are the functions of bile?
- Breaks down and emulsifies fats and oils (increases surface area)
- Helps neutralise chyme (sodium hydrogen carbonate)
What are the parts of the small intestine called?
- Duodenum
- Jejunum
- Ileum
What happens in the small intestine?
Digestion and absorption
How long does food stay in the small intestine?
1-6 hours
What is the main function of the duodenum?
- Main function of digestion
- Also produces intestinal juice
Amaylase \:Made \:Active in \:pH \:Substrate \:Product
- Salivary glands/ Pancreas
- Mouth/ Duodenum
- 7 - 8
- Starch
- Maltose
Pepsin \:Made \:Active in \:pH \:Substrate \:Product
- Stomach lining
- Stomach
- 2
- Protein
- Peptides
Hydrochloric acid \:Made in \:Active in \:Substrate \:Product
- Stomach lining
- Stomach
- Bacteria and fibrous foods
- Dead bacteria and softened food
Sodium Hydrogen Carbonate \:Made in \:Active in \:Substrate \:Product
- Pancreas
- Duodenum
- Acid
- Neutralised acid
Lipase \:Made in \:Active in \:pH \:Substrate \:Product
- Pancreas
- Duodenum
- 7-8
- Lipids
- Fatty acids and glycerol
What happens to the food by the time it leaves the duodenum?
Digestion is complete
What is the function of the jejunum and the ileum?
-Absorption of digested food
What are the adaptations of the small intestine?
- Lining contains many villi
- Very long
- Rich blood supply inside each villus
- Lacteal inside each villus
- Walls of villi only one cell thick
What do the capillaries absorb?
- Water
- Glucose
- Amino acids
- Vitamins
- Minerals
What is the function of the hepatic portal vein?
To transport nutrients to the liver
How long is the large intestine?
1.5 m
How long does food stay in the large intestine?
From 10 hours to a few days
What is the function of the colon?
- To reabsorb water
- Liquid waste is converted to semi-solid waste called faeces
How does diarrhea occur?
- Occurs when undigested food moves through the large intestine too quickly
- Less water is reabsorbed: faeces more liquidy
How does constipation occur?
- Undigested food moves through the large intestine too slowly
- Too much water is reabsorbed
Where are symbiotic bacteria found?
In the colon
What is the function of symbiotic bacteria?
- Produce B group vitamins and vitamin K
- Prevent growth of disease causing bacteria and fungi
- Break down food, cellulose, some of the digested food is absorbed into the body
Amount of food a person requires depends on:
- Age
- Activity levels
- Gender
- Health
