Human nutrition Flashcards
What is digestion?
Digestion is the chemical (enzymes) and physical breakdown of food into small soluble pieces.
What is the function of digestion?
To ensure food can be absorbed (into bloodstream)
What does autotrophic mean?
An organism that can make its own food (plants)
What does heterotrophic mean?
Organisms that cannot make their own food (carnivores, herbivores, omnivores)
What is a saprophyte?
Organism that takes in nutrition (food) from a dead source (fungi)
What are the 5 stages in human nutrition?
- Ingestion (take in food)
- Digestion
- Absorption (into bloodstream)
- Assimilation (how cells use the absorbed food)
- Egestion (getting rid of undigested food)
Name an example of physical digestion in the mouth
Teeth grind food
Name all the types of teeth found in the mouth
Incisors 2/2, canines 1/1, pre-molars 2/2, molars 3/3 (32 teeth total)
How does chemical digestion occur in the mouth?
Saliva - contains an enzyme called amylase - starch is broken up using amylase into maltose
What occurs in the oesophagus?
A bolus (ball) of food is formed and swallowed.
Bolus of food enters the oesophagus by epiglottis (cartilage to ensure food enters the right pipe).
Food is moved by muscular action called peristalsis.
Food enters the stomach by the cardiac sphincter muscle
What shape is the stomach?
J - shaped muscular bag
How does physical digestion occur in the stomach?
Stomach churns food.
Name the 3 gastric juices
Hydrochloric acid (HCL), pepsinogen, mucous
What are the qualities of hydrochloric acid?
pH 2 (acidic), kills bacteria, activates pepsinogen into pepsin
What are the qualities of pepsinogen?
Activated into pepsin by HCL and chemically digests polypeptides into peptides (protein)
What is the function of mucous in the stomach?
Lining of stomach muscle preventing self digestion and ulcers
What happens to food in the stomach after 1 and a half hours
Chyme is formed
How does food enter the small intestine?
By the pyloric sphincter muscle
Name the two parts of the small intestine
Duodenum and ileum
How long is the duodenum?
25cm long
What occurs in the duodenum?
Digestion is fully achieved,
pancreas releases pancreatic enzymes/ juices into duodenum
Name the four pancreatic enzymes released into the duodenum?
Pancreatic protease (breakdown proteins into amino acids)
Pancreatic amylase (starch into maltose)
Pancreatic lipids (lipids into glycerol and 3 fatty acids)
Pancreatic maltase (maltose into glucose)
At what pH do pancreatic enzymes function best at?
pH 8
Where is bile produced?
In the liver
Where is bile stored?
The gall bladder
How is bile released into the duodenum?
Through the bile duct
What type of organ is the liver?
Heat organ
What are 3 functions of bile?
Neutralises chyme (pH 8)
emulsifies fat
produced by dead red blood cells
What is deamination in the liver?
Breakdown of proteins into urea
What is stored in the liver?
Glucose (glycogen), vitamins, minerals
Name another function of the liver
Detoxifies
How long is the ileum?
4-5m long (highly coiled to increase surface area for absorption)
What is found on the inner lining of the ileum?
Finger-like projections called villi (villus)
How does digested food move into the bloodstream?
Through the thin walls of villi (except fats)
How does the ileum attach to the liver?
By the hepatic portal vein (carrying blood rich in absorbed food)
Where do fats move to in the ileum?
Into the lacteal of the villi (joined to lymphatic vessel and fats enter the lymphatic system)
Where do fats drain into the blood?
At the subclavian vein (collarbone)
How are villi adapted to their function?
They’re only one cell thick for rapid absorption of food.
Excellent blood supply for rapid movement of nutrients.
Finger like increasing surface area for absorption.
Microvilli for increasing surface area for absorption.
Where does the small intestine join to the large intestine
At a junction called caecum.
How long is the large intestine?
large in diameter but only 1m long.
What are the parts of the large intestine?
colon, rectum and anus
How does undigested food move through the large intestine?
By a process called peristalsis
What is the function of the large intestine?
- Reabsorb H2O leaving a solid waste (faeces)
- Symbiotic bacteria (2 organisms living in close contact where at least 1 benefits) live in large intestine and they digest cellulose. In turn produce vitamins B and K.
Name three types of symbiotic bacteria.
Parasitism, mutualism and commensialism
