Download Nutrition

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project

Document related concepts

Bile acid wikipedia , lookup

Pancreas wikipedia , lookup

Ascending cholangitis wikipedia , lookup

Glycogen storage disease type I wikipedia , lookup

Fatty acid metabolism wikipedia , lookup

Gastric bypass surgery wikipedia , lookup

Hepatotoxicity wikipedia , lookup

Transcript
Nutrition
photosynthesis
Autotroph
Herbivores
Heterotroph
Carnivores
Omnivores
Nutrition
Balanced diet includes all 7 components
Energy content of food measured in
kilocalories
The average teen-ager needs
Approximately 2200 calories for girls
2800 calories for boys
Carbohydrate- 4.5 calories/g
Protein –
4.5 calories/g
Fats9 calories/g
Obesity
New Food Pyramid 2005
- emphasise importance of controlling
weight and physical activity
- dietary fats – limit saturated fats
20-35% or less of energy should come
from fats, healthiest are
monounsaturated and polyunsaturated
-limit sugar intake
-stress benefits of wholegrains
Alimentary canal
2 main functions:
•Digesting and absorbing nutrients
•Protecting from invasion
Mouth
-mechanical digestion (mastication) = teeth, tongue
-chemical digestion = saliva (amylase, lysozyme)
Trachea - windpipe
Uvula – prevents food entering the nose
Epiglottis – safety hatch. A flap of cartilage
prevents food from entering the trachea
Oesophagus
-transfers food to stomach by peristalsis
Cardiac sphincter
-opens to allow food oesophagus stomach
-heartburn –acid escapes stomach
oesaphagus
http://library.thinkquest.org/11226/main/c03txt.htm
Stomach
Short term storage reservoir (1L for up to 4h)
Digestion = chemical (HCl and enzymes) - proteins
= mechanical - liquefication of food
Slowly releases food into intestine
chyme
Cardiac sphincter
Pyloric sphincter
http://35.9.122.184/images/41-AnimalNutrition/41-16-Duodenum-L.gif
Stomach Epithelium
Mucous – goblet cells
Prevents self-digestion
Enzymes (pepsinogen) – chief cells
Acid (HCl) – parietal cells
Activated to pepsin
Converts proteins peptides
pH 1-2
Kills bacteria
Hormone (gastrin) – G cells Loosens
Controlsfibrous
gastricfoods
motility and
Activates
pepsinogen
acid secretion
Denatures salivary amylase
Stomach epithelial cells are
some of the fastest growing
cells in the body, typically
replacing themselves
about every 3 days
Ulcers (stomach, duodenum) –
peptic ulcers. Most commonly
caused by H. pylori
Small Intestine
Around 6m in an adult
Food takes 1-6 h to pass through
2 main tasks = digestion, absorption
3 parts
Duodenum
Jejenum
Ileum
Duodenum = digestion = 25cm long
Pancreas –pancreatic juice= NaHCO3, enzymes (insulin, glucagon)
pH of duodenum = 7-8
Amylase, lipase, trypsinogen, chymotrypsinogen
Liver –
bile made in liver, stored in gall bladder = Water, salts, bile salts
Neutralise HCl
Digestion and absorption of fats and fat soluble vitamins (emulsification)
Waste products eliminated by secretion into bile and elimination in feces
(e.g. bilirubin, biliverdin)
Liver
Right lobe
Left lobe
Blood rich in
food from ileum
Weighs about 1.5kg
Holds about 13% of total blood
Liver cell = hepatocyte
Unique ability to regenerate – average life = 150 days
The liver performs over 500 jobs. Some of these are:
•Makes bile (600mls/day)
•Detoxifies body (alcohol, drugs etc)
•Breaks down excess amino acids urea (deamination) kidney
•Converts glucose glycogen for storage (source of quick energy)
•Converts excess carbohydrates fat
•Stores vitamins - A, D, E and K
•Stores minerals – Fe, Cu, Zn
•Makes plasma proteins e.g. fibrinogen – blood clotting
•Makes cholesterol – needed to form many hormones
•Produces heat to warm blood
•Clears blood of particles, including bacteria
•Fights infections –half the body’s macrophages -destroy bacteria
•Produces hormones, including the sex hormones
http://www.britishlivertrust.org.uk/content/liver/about.asp
Small Intestine cont.
Jejenum – digestion/ absorption. 2.5m long
Ileum – absorption. 4m long
Walls only one cell thick
Villi, microvilli – increase surface area for absorption
Rich blood supply – capillaries absorb water and soluble nutrients (glucose, amino acids,
vitamins, minerals) and the blood carries the nutrients to the liver, which stores nutrients
and releases them as required
Lacteal – contains lymph. Fatty acids and glycerol are absorbed by the epithelial cells
where they reform into fats. They become coated in protein (chylomicrons) and pass into
the lymph in the lacteals. It takes around 18h for lymph to rejoin the blood, the protein
coat dissolves and fats are absorbed into cells
Large Intestine
1.5m long, 6cm diameter
Food stays 10h to a few days
Caecum
Appendix
Function unknown – in
herbivores they
contain bacteria that
help digest cellulose
Colon
Reabsorbs water – so waste is converted to semi-solid = faeces – egested
Diarrhoea, constipation (fibre helps stimulate peristalsis)