Human Nutrition Flashcards
What are the three branches in heterotrophs?
Herbivores, Carnivores and Omnivores
What are herbivores?
Animals that feed exclusively on plants eg, cattle, sheep
What are carnivores?
Animals that feed on other animals eg, seals
What are omnivores?
Animals that feed on plants and animals eg, humans, bears
What is digestion?
It’s the breakdown of food into particles that are small enough to pass into body cells
What does digestion allow?
Allows materials needed to process the food to be localised in a single place eg, teeth in mouth
Prevents each cell having to contain a full range of digestive enzymes
What is ingestion?
It’s the taking in of food into the alimentary canal eg, putting food in your mouth
What is digestion?
It’s the mechanical or chemical breaking down of food into particles that are small enough to pass into body cells
Why is digestion essential for absorption?
If food isn’t broken down, chemicals in food would not pass from digestive system into body tissues
What is absorption?
Soluble food is passed from cells into bloodstream
What is egestion?
It’s the removal of unabsorbed and undigested material from the digestive system through anus
What sort of digestion occurs in the mouth?
Mechanical digestion, chewing action of teeth
Function of incisors
Cutting, slicing
Function of Canines
Tearing
Function of Premolars and molars
Chew, crush
What is the human dental formula?
Shows the arrangement of the different types of teeth
2(2/2 I, C 1/1, PM 2/2, M 3/3)
Upper numbers = upper jaw of one side of mouth, Lower numbers = lower jaw of one side of mouth
Digestion in the mouth
Mechanical digestion - teeth = break down food into smaller particles so it is easier to swallow and have a greater surface area for enzyme to action
Chemical digestion - due to the enzyme amylase in saliva. Saliva is produced by 3 parts of salivary glands located under the tongue, back of the jaw and cheeks. It helps soften and dissolve food so we can swallow it
What does saliva consist of?
Water, Salts, Mucous [mucin] and enzymes amylase and lysozyme
What does amylase do?
It digests starch into maltose
Ideal ph is 7/8 and temperature is 37 degrees
What is the function of the epiglottis?
It closes over the trachea and ensures it passes down the oesophagus
What is the function of the oesophagus?
It carries food to the stomach by peristalsis
What is peristalsis?
It’s an involuntary wave of muscular contraction
When food enters the oesophagus, what assists the movement?
Mucous found in saliva and by mucous produced by inner lining of oesophagus
What is the function of peristalsis?
It moves food though the alimentary canal
In stomach - it helps breakdown food mechanically
Iit mixes food with the secretions of the stomach and then forces into the small intestine
Small intestine - forces food forwards and backwards, which helps food to be absorbed
Large intestine - Strong wave of peristalsis forces waste into the rectum
Name a fibre
Dietary fibre [also called roughage] consists of cellulose from plant cell walls. Humans cannot digest cellulose
Give sources of fibre
Wholemeal bread, cereals, vegetables and fruit
What is the function of fibre?
It absorbs and store water which causes unabsorbed wastes to expand, especially in large intestine
Physical bulk of waste stimulates the muscles of intestines to work = fibre stimulates peristalsis
Reduces constipation
What is the stomach?
It’s a muscular bag that stores and digests food
What is a sphincter muscle?
A circular muscle that opens and closes
How are gastric glands formed?
Due to the lining of the stomach being heavily folded
What is gastric juice?
Gastric glands produce a range of secretions
What does gastric juice consist of?
Mucous - coats the stomach and prevents self digestion
Pepsinogen - inactive enzyme which is converted to the active enzyme pepsin by acid in the stomach
Hydrochloric acid - gives the stomach a pH of 1 to 2. This acid kills many bacteria, loosens fibrous and cellular foods and activates pepsinogen
What enzyme digests proteins?
Pepsin digests proteins into peptides
What do the contraction of the stomach walls do?
Helps churn and digest food mechanically. This turns it into a mixture called chyme
Protection from self digestion
Mucous lines the stomach
Mucous is alkaline and reduces acidity near stomach wall
Pepsin is released as an inactive pepsinogen
What are the glands associated with the small intestine?
Pancreas, Liver
What does the pancreas secrete?
The hormone insulin + digestive materials = form pancreatic juice
What does pancreatic juice consist of?
Sodium hydrogen carbonate and enzymes such as amylase and lipase
What does the sodium hydrogencarbonate in the pancreas do?
It neutralises the chyme
What does pancreatic lipase do?
It converts lipids to fatty acids and glycerol
Where are pancreatic lipase and amylase active in?
In the duodenum
What pH does lypase work best in?
pH of 7/8
What are the functions of the liver?
Makes bile, detoxifies the body [breaks down poisons such as alcohol], breaks down amino acids to form urea, converts excess carbohydrates into fat and produces heat to warm the body
What is bile?
It consists of water, bile salts and bile pigments [no enzymes]
Partly formed from remains of dead red blood cells
Where is bile made and where is it stored?
Made in liver and stored in gall bladder
Where can gallstones form?
In the bile duct and prevent the release of bile
Where does bile enter?
Duodenum through bile duct
Functions of bile
It emulsifies lipids - breaks down fats into tiny droplets which increases the surface area for enzyme digestion
Contains sodium hydrogen carbonate which helps neutralise chyme in stomach
The small intestine consists of two main parts, what are they?
The duodenum [where most of the digestion occurs] and the ileum [absorption of digested food into the body takes place]
What is the function of the duodenum?
Digestion
Cells lining the duodenum produce digestive enzymes
Products or pancreas and liver enter duodenum
What is the function of the ileum?
Absorbs nutrients
What is the function of villi?
It increases the surface area for either digestion or absorption
What are the intestinal glands?
Found between the villi and produce a large range of enzymes called intestinal juice
Where are the villus found?
Lining of duodenum and Ileum
What do the capillaries in villus do?
Carry nutrients to hepatic portal vein and then to liver
Where do urea and other wastes leave the liver?
Through hepatic portal vein and to kidney
What is lacteal?
Found inside each villus and contains lymph
Where are fatty acids and glycerol absorbed into?
Cells of villus lining where they reform into fats coated with protein. They then pass into lymph in lacteals
Where are the fats transported into the bloodstream?
Transported by lymph and is carried to bloodstream at subclavian veins near base of neck.
Adaptions of small intestine for absorption?
Very long
Numerous villi
Walls of villi are one cell thick
Rich blood supply to carry away water soluble products
Each villus has lymph supply [lacteal] to carry away fats
What is the large intestine made up of?
Caecum, appendix and colon
Where is the caecum and appendix?
Below junction of small intestine
What are the functions of caecum and appendix
Not known, to many herbivores they contained bacteria capable of digesting cellulose.
What are the caecum and appendix known as
Vestigial organs - they have lost their former use, no longer need to digest cellulose as we get carbohydrate supplies from starch
What is the function of the colon?
To reabsorb water
How so faeces formed?
Liquid waste enters large intestine and turns into faeces
Where is faeces stored?
In rectum and then egested through anus
What is diarrhoea
Occurs when unabsorbed material passes too rapidly through the colon, less water is reabsorbed so faeces contains more liquid
What is constipation?
When unabsorbed material passes through the colon too slowly so that too much water is reabsorbed.
What is a symbiotic bacteria?
Bacteria that live in or on another organism to the benefit of at least one
Give examples of symbiotic bacteria?
Bacteria in the colon feed on waste and produce some B group and K group vitamins . We absorb these vitamins from the colon.
The presence of beneficial bacteria prevent the growth of pathogenic bacteria and fungi
Bacteria in the digestive system also break down food, especially cellulose. Some of the digested nutrients are absorbed into the body from the intestines
What is a balanced diet?
Correct amounts of each food type
The amount of food a person requires depends on what?
Age [young people need more food than older individuals]
Activity levels
Gender [male needs more food]
Health
What are the four food groups?
Cereals, bread and potatoes
Fruit and vegetables
Milk, cheese and yogurt
Meat, fish and poultry
Give two functions of the large intestine
Reabsorbs water, peristalsis, egestion
Outline two beneficial functions of bacteria that live in digestive tract
Production of vitamins - colon
Beneficial bacteria
Digestion - digest cellulose
What is the ph of the contents of the small intestine?
Alkaline
(The enzymes in the small intestine work best in alkaline conditions, but the food is acidic after being in the stomach. A substance called bile neutralises the acid to provide the alkaline conditions needed in the small intestine)
Name two glands that pass their secretions into the small intestine and name the secretions
Pancreas- pancreatic juice
Liver - bile
Where in the human alimentary canal is the most water absorbed?
Colon
Why is digestion necessary?
For absorption
Transport
One digestive function of the pancreas
Produces enzymes
What part of the digestive system are the products of digestion absorbed into the blood?
Ileum
What part of the digestive system is water absorbed into the blood?
Colon - large intestine
Name a substance transported to the liver in the hepatic portal vein
Co2
Name two associated glands of the human alimentary canal
Liver, Pancreas
What is lipase?
Enzyme that digests lipids
Give one part of the alimentary canal that secretes lipase and what is the approx pH at the site of lipase action?
Pancreas
7-9
Draw and label digestive tract
Purple book page 30-31
Exam papers - pg 115
Structure of Villi
Purple book - page 31
Exam papers - page 111
From which part of the alimentary canal does food arrive into the duodenum?
Stomach
Draw a labelled diagram to show the relationship between the liver, the small intestine and the hepatic portal vein
Purple book - 31
Where in the human body is the liver located in relation to the stomach
To the right
Give one role that bole salts play in the digestive process
Emulsify lipids
Neutralising acid food
Where is lipase secreted and where does it act?
Secreted - Pancreas
Act - Duodenum
Name the part of the digestive system in which the products of digestion are absorbed into the blood
Ileum
Name a process involved in the passage of the products of digestion into the blood
Difussion
State the precise location of the liver in the human body
Upper abdomen
What type of food is mainly absorbed into the lacteal
Lipids
What is the function of the blood capillaries in villi?
Absorb glucose and amino acids
