HUMAN NUTRITION and DIGESTIVE SYSTEM Flashcards
Why are the energy requirements for women lower than men?
lower body mass than men
physical demands
Why does energy requirements increase as a child grows?
for the growth process
the extra energy needed to maintain their body temperature
How could jobs affect energy requirement?
A person who does hard labour work will use more energy than a person sitting on a desk
someone who takes part in a lot of sport will need more energy than a person who doesn’t
Describe the energy requirements of a pregnant woman.
If the woman has an adequate diet there is no need for more food as the baby’s metabolism will adapt to the demands of a growing baby and the demand for energy and protein increases
If the diet is deficient, in protein, calcium, iron, vitamin D, folic acid, she will need to increase the uptake.
What is a protein needed for?
Required for making tissues
What is calcium needed for?
Bone development
What is Iron needed for?
haemoglobin for blood
What is lactation?
Production of breast milk
How is lactation affected by energy requirements?
The production of milk rich in protein and minerals makes a large demand for the mother’s resources.
What is a balanced diet?
Contains the correct proportions of lipids, carbohydrates proteins, vitamins and minerals, water and fibre that the body needs to function properly
What are the sources of carbohydrates?
Rice potato pasta provide starch
deserts and sweet provide refined sugars
What are the functions of carbohydrates?
oxidised source of energy for respiration
excess carbo stored as glycogen and fat
What are the sources of lipids?
Meat and animal food rich in saturated fat and cholesterol
plant sources are rich in unsaturated fats
What are the functions of lipids?
energy store
provide insulation
make steroid hormones
form part of the cell membrane
What are the sources of proteins?
meat fish eggs legumes
What can deficiency in protein cause?
marasmus and kwashiorkor
What is the function of proteins?
To transport molecules
make enzymes
structural materials hormones and antibodies
What are the sources of vitamin c?
cherries citrus fruits green vegetables
What are the deficiency symptoms of vitamin c ?
Scurvy- production of fibres in the body is affected
What are the sources of vitamin d?
Liver, dairy products, eggs and sunlight
What are the deficiency symptoms of vitamin d?
rickets- bones are soft and may bend as vit D needed for absorption of calcium
What are the sources of iron?
red meat, liver spinach
What are the deficiency symptoms of iron?
Anaemia as iron is needed for the production of haemoglobin
What are the sources of calcium?
milk and cheese and fish
What are deficiency symptoms of calcium?
Weak bones, poor clotting of blood, uncontrolled muscle spasms, rickets
What is fibre?
Indigestible part of food mainly cellulose from plant cell walls
helps to stretch muscles in the gut and push food along through peristalsis
What is malnutrition?
Bad feeding includes eating too much, eating too little food or eating food in wrong proportions
Define Starvation
Suffering or death that is caused by not eating enough food
Describe the diet of kwashiorkor
Diet high in carbohydrates and low in protein
What are the signs of kwashiorkor?
mental and physical development may be impaired
slow muscle development and swollen liver
swollen abdomen due to water from the blood left behind in the tissues
what is marasmus?
general starvation. body tissues waste away, thin with wrinkled skin
What is coronary heart disease?
Too much saturated fat and cholesterol will cause blockage in blood vessels
What is constipation?
Infrequent bowel movements causing difficulty passing faeces
What is obesity?
When the fat storage is beyond a healthy limit
What is ingestion?
Taking substances through the mouth
What is mechanical digestion?
The breakdown of food into small pieces without chemical change to the food molecules
What is chemical digestion?
The breakdown of large insoluble molecules into small water-soluble molecules
What is absorption?
The movement of small digested food molecules and ions through the wall of the intestine into the blood
What is assimilation?
Movement of digested food molecules into the cells of the body where they are used becoming part of the cells.
What is egestion?
Passing out of undigested food substances and dietary fibre through the anus
What is diarrhoea?
It is the loss of watery faeces.
What is diarrhoea caused?
It is caused by a bacterial or viral infection from food or water
How does cholera cause diarrhoea?
Vibrio cholera bacteria are ingested and they multiply in the small intestine and invade its epithelial cells. As the bacteria become embedded they release toxins which irritate the intestinal lining and leads to the secretion of large amounts of water and salt. Salts decrease the osmotic potential of the gut drawing more water from surrounding tissues by osmosis. The blood contains too little chloride ions and water
What can diarrhoea cause?
The loss of body fluids and salt leads to dehydration and kidney failure.
What is treatment for cholera?
Oral hydration therapy
drinking plenty of fluids sipping small amounts of water at a time to rehydrate the body
What are the incisors meant to do?
for cutting and biting
What are the canines meant to do?
For holding and tearing
What are the premolars supposed to do?
For chewing and crushing
What are the molars supposed to do?
For chewing and crushing
What does the pulp cavity contain?
Tooth producing cells
blood vessels
nerve endings which can detect pain
What is dentine?
Harder than bone and made of calcium salts deposited on collagen fibres and has canals
What is enamel?
Hardest tissue in the body
produced by tooth forming cells and made of calcium salt
once formed enamel cannot be renewed or extended
What is the cement?
No canals and anchors tooth to jaw
What is gum?
Covers the junction between enamel and cement.
What is a periodontal membrane?
Bundles of collagen fibres anchoring the cement covering of the tooth to the jawbone
Many nerve endings which detect pressures
What is a cavity?
Small holes that appear in the enamel
What are cavities caused by?
By bacteria feeding on the sugars deposited on the teeth, respiring and producing acid which dissolves the calcium salts in the tooth enamel.
Describe dental decay
The enamel is dissolved away exposing the dentine to the acids. Dentine is softer than the enamel and dissolves more quickly so cavities form. The acids produced by the bacteria nitrate the nerve endings and cause toothache.
List 6 ways to prevent dental decay
Eating food with a low sugar content brushing of teeth twice a day Eating crisp vegetables dental floss or interdental cleaners visit the dentist fluoride treatment
What is chemical digestion?
Chemical digestion is breaking down large insoluble molecules into small soluble ones.
What is the ideal environment for chemical digestion?
Enzymes work at 37C at a suitable pH
Where does chemical digestion happen?
mouth
stomach
small intestine
Which enzyme is found in the mouth and what does it break down?
Maltase breaks down starch into soluble simpler sugar maltose.
What does saliva contain?
Sodium hydrogen carbonate which provides ideal pH conditions for amylase
What does the pyloric sphincter do?
Lets the liquid products of the digestion pass a little at a time into the first part of the small intestine called the duodenum.
What does the small intestine consist of?
Duodenum and ileum
What enters the duodenum?
Digestive juices from the liver (bile) and pancreas (enzymes)
What do the digestive juices contain that enter the duodenum?
Trypsin
amylase
lipase
bile
What is bile?
Bile is a green fluid delivered to the duodenum by the bile duct. It emulsifies the fats, breaking them up into small droplets with a larger surface area so it can be digested by lipase more efficiently. It neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach.
Where does the absorption of digested food take place?
In the ileum along with most of the water
Why is the ileum efficient in absorption?
The long and large absorbing surface area
Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
Wall of villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport
Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph
How does glucose and amino acids get absorbed?
they pass into the cells and through the wall of the capillaries in the villus and into the bloodstream
How do fatty acids and glycerol get absorbed?
they pass into the cells and are absorbed by the lacteal which connects to the lymphatic system
What is the lymphatic system?
Transport lymph, a fluid containing infection-fighting white blood cells throughout the body
What is the lacteal?
Absorbs fatty acids and glycerol
What is the thin epithelium?
One cell thick to increase the diffusion rate.
What is the blood capillary?
Absorbs glucose and amino acids
Where does the blood from the intestines travel to?
The liver
What are the functions of the liver?
Manufacture bile store glucose as glycogen transamination deamination detoxification
What is transamination?
converting amino acids into others that the body requires
What is deamination?
Removing nitrogen-containing part of amino acids to form urea followed by the release of energy from the remainder of the amino acid
What is detoxification?
Break down of alcohol and toxins
Why is the liver important?
It provides the ideal concentration of food molecules for the body tissues
What does the large intestine consist of?
colon and rectum
What does the material that passes into the large intestine consist of?
Consists of water with the undigested matter, largely cellulose, vegetable fibres, mucus and dead cells
What does the colon do?
Absorbs much of the water
What are faeces?
A semi-solid waste which is passed to the rectum where it is stored.
What do the salivary glands do?
Produce saliva and pour it into the mouth through the salivary ducts
What do the oesophagus?
a muscular tube which helps food move to the stomach by peristalsis
What is the stomach?
A muscular bag which stores food for a short time and mixes food with acidic digestive juices to form chyme
What is the gall bladder?
Stores bile before pouring it into the duodenum through the bile duct
What is the duodenum?
The first part of the small intestine where semi-liquid food is mixed with pancreatic juice and bile
What is the pancreas?
Produces pancreatic juices which are poured into the small intestine through the pancreatic duct
What is the ileum?
The longest part of the small intestine where digested food is absorbed into the blood and lymphatic system
What is the rectum?
Stores faeces before expelling them at a convenient time
What is the anus?
Exit for faeces
What is the large intestine?
The colon is part of the large intestine. It reabsorbs water from the gut contents which also absorbs some vitamins and minerals
What is peristalsis?
Waves of muscular contraction and relaxing in the oesophagus
What is the mouth?
Food is chewed by teeth and mixed with saliva
tongue rolls the food into a bolus
What is the epiglottis?
A flap of skin that prevents food from entering the bronchus.
Describe the movement of the muscles when a bolus enters the oesophagus.
When the bolus enters the oesophagus the v=cricular muscles behind its contract and the longitudinal muscles relax.
What is the enzyme that breaks down carbohydrates?
Carbohydrase
What is the enzyme that breaks down proteins?
Protease
What is the enzyme that breaks down lipids?
lipase
What is pepsin?
A protease enzyme which breaks down large protein molecules into small soluble amino acids
What is the mucus?
Protects the wall of the stomach
What do glands in the lining of the stomach contain?
Pepsin
Hydrochloric acid
mucus
What does the ileum absorb?
Fats
glucose
amino acids
Where is amylase made?
Pancreas/Mouth
Where is protease made?
Pancreas/stomach
Where is lipase made?
Pancreas
Why is the hydrochloric acid in the stomach useful?
Kill bacteria in the food and denatures enzymes in harmful microorganisms in food
Provides optimum pH for pepsin.
