human niutrition Flashcards
Autotrophic
Autotrophs make their own food e.g.
plants
Heterotrophic
Heterotrophs take in food from the
environment. They cannot make their own
food
Heterotrophs can be divided into three main categories;
Carnivores
Herbivores
Omnivores
Carnivores
Animals that
mainly feed on
other animals
example of carnivore
fox
Herbivores
Animals that
mainly feed on
plants
example of herbivores
rabbits
Omnivores
Animals that
mainly feed on
plants and
animals
example of omnivores
humans
What is Digestion?
The physical and chemical breakdown of food into soluble particles
small enough to pass into body cells
Why do we need a digestive system?
To break down large food particles until they are small enough to pass
into body cells
Human Digestive System
a long tube, starting
at the mouth and ending at
the anus.
Stages in Human Digestion
Ingestion
digestion
absorption
egestion
Ingestion
Food is taken into the mouth
Digestion
The breakdown of food. Can be either
chemical or physical
Absorption
Digested food passes from the digestive
system into the blood
Egestion
The removal of the unabsorbed waste from
the digestive system
what does the mouth contain
Contains a muscular
tongue and a set of teeth.
what does the mouth secrete and from where
a juice called
saliva from the salivary
glands.
what does saliva contain
water,
salts, and the enzyme
Salivary amylase.
Humans have four types of teeth;
incisors, canines, premolars and molars.
Incisors
shaped like chisels and cut and slice food
Canines
long, pointed and fang like. They tear food
Premolars
large, flat teeth and are used to crush and grind food
Molars
large teeth which cut and grind food
Human Dental Formula
2 incisors, 1 canine, 2 premolars aand 3 molars
Oesophagus
A hollow muscular tube, 25 cm long that connects the pharynx to the stomach.
Oesophagus job
The walls of the Oesophagus secrete mucus and the food is moved by Peristalsis
Perestalisis
Peristalsis is a wave of muscular action in the walls of the alimentary canal that moves the contents along
Describe the shape of the stomach
J shaped muscular bag
How long does the food store in the stomach
About 4 hours
What kinds of digestion takes place in the stomach
Physical and chemical
Explain the mechanical digestion in the stomach
Peristalsis physically mixes up the food
with gastric juices, forming chyme.
Explain the chemical digestion in the stomach
using Gastric Juice containing: a) Mucus
b) HCI
c) Pepsin
Mucus in the stomach
Lines and protects the stomach wall from HCI & pepsin
HCI in the stomach
Kills bacteria
b. Activates pepsin, by lowering the pH
Pepsine in the stomach
Pepsin is an enzyme produced by the cells lining the stomach. Pepsin breaks down protein into peptides
Describe the lining in the stomach
The lining of the stomach is very muscular and highly folded
What happens in the lining of the stomach
Millions of gastric glands line the stomach producing gastric juice
Functions of hydrochloric acid
•This gives stomach a pH of 1 to 2!
•Very acidic
This acidity kills many bacteria, loosens fibrous and cellular foods
•Activates pepsin
•Denatures amylase from saliva
What happens if there is too much hydrochloric acid in the stomach
Leads to heartburn but can be neutralized with alkalis
How can ulcer result
If gastric juice does manage to digest the stomach wall, ulcers can result
•If ulcer becomes perforated, bacteria could get into body causing illness
What are the two main parts of the small intestine
The duodenum
The ileaum
What are the gland associated with the small intestines
Pancreas and the liver
What does the pancreas secreet
The hormone insulin and pancreatic juice
What does the pancreatic juice consist of
sodium hydrogen carbonate (which neutralizes chyme), and also enzymes such as amylase and lipase
•These enzymes enter the duodenum through the
pancreatic duct
Functions of pancreas
• Lipase converts lipids into fatty acids
Amylase converts starch into maltose
Liver functions
- Making bile
- Detoxifying the body
- Converting glucose to glycogen
- Converting excess carbohydrate to fat
- Storing vitamins and minerals
- Breaking down amino acids to form urea
Describe bile
Bile is a yellow-green liquid that is made in the liver and stored in the gallbladder
Enters the duodenum through the bile duct
Function of bile
Breaks down fats and oils, neutralizes chyme from the stomach and excretes pigments
Describe villi
The inner lining of the small intestine contains infoldings called villi which contain many microvilli.
Function of villi
These infoldings increase the surface area in the duodenum (for digestion) and in the ileum (for absorption)
Functions of the duodenum
The cells lining the duodenum produce digestive enzymes
•The products of the pancreas and liver also enter the duodenum
•Amylase and Lipase from the pancreas enter the duodenum. Amylase converts starch into maltose
Lipase converts lipids into fatty acids and glycerol
Carbohydrates digest into
Monosacharides
Proteins digest into
Amino acids
Lipids digest into
Fatty acids and glycerol
How is the food when it enters the ileum
Almost fully digested
What happens to the food in the ileum
The walls of the ileum contain many villi which are surrounded by many capillaries I
-The capillaries absorb water, glucose, amino acids, vitamins and minerals and carries them to the hepatic portal vein
The hepatic portal vein carries them to the liver where some nutrients are stored and some are released
- Amino acids cannot be used in the body and are broken down in the liver to form urea. The urea passes to the kidneys via the hepatic vein
• The capillaries in each villus absorb water and nutrients (e.g. glucose, amino acids and vitamins)
•The capillaries carry these to the hepatic portal vein which takes them to the liver
•The liver stores the nutrients
Amino acids are toxic to the body and cannot be stored - they are broken down in the liver to form urea- deamination
What is inside each villus
A lacteal which contains a liquid card lymph
What is transported by the lymph
Fats are transported by lymph in the lymph vessels to the bloodstream
Adaptations of the Small Intestine for Absorption
- It is very long
- Has villi and microvilli
- The walls of villi are very thin
- There is a rich blood supply to carry away water soluble products
- Each villus has a lymph system to carry away fats
Where are the caecum and appendix
The Caecum is at the junction of the small intestine, the appendix is at the end of the caecum
Function af caecum and apendix
In herbivores, the caecum and appendix contain bacteria which help in the digestion of cellulose
Large Intestine
Caecum
Appendix
• In humans, the caecum and appendix are vestigial organs (they no longer have a use)
What is the function of the colon
The function of the colon is to reabsorb water which converts the liquid waste that enters the large intestine into semi-solid waste called faeces
Faeces are stored in the rectum before being egested from the anus
What is Fibre made out of
Cellulose
Tole of fibre
•Humans cannot digest cellulose
• Fibre absorbs and stores water which causes the unabsorbed waste to expand
•This stimulates the muscles of the intestine to work i.e. it stimulates peristalsis
• Prevents constipation
What are symbiotic bacterias
Beneficial bacteria prevent the growth of disease causing bacteria and fungi
Functions of symbiotic bacteria
• Bacteria in the colon feed on waste and produce some B and K group vitamins. These vitamins are reabsorbed into the bloodstream in the colon
• Bacteria in the digestive system break down food, especially cellulose
Balanced diet
A balanced diet contains all the necessary food types in the correct
proportions
Components for balanced diet
- Carbohydrates
- Protein
- Lipids
- Vitamins
- Minerals 6. Water
- Fibre
The amount of food a person needs depends on
- Age
- Activity levels
- Gender
- Heath
