Download Nutrition

The Digestive System
and Nutrition
http://apc.ucc.ie
Nutrition
photosynthesis
Autotroph
Herbivores
Heterotroph
Carnivores
Omnivores
Nutrition
Balenced diet includes all 7 components
Energy content of food measured in
Joules (J)
Amount of food required depends on..?
Approx
9600kJ girls
12,600kJ boys
Carbohydrate-17kJ/g
Protein –
17kJ/g
Fats38kJ/g
Obesity
New Food Pyramid 2005
-emphasise importance of controlling
weight and physical activity
-dietary fats –limit saturated fats
20-35% of energy should come from
fats, especially monounsaturated and
polyunsaturated fats
-limit sugar intake
-stress benefits of wholegrains
Alimentary canal
2 main functions:
•Digesting and absorbing nutrients
Mouth •Protecting from invasion
-mechanical digestion (mastication) = teeth, tongue
-chemical digestion = saliva (amylase – breaks down
starches)
Three main salivary glands:
1.
Parotid - behind the ear
2.
Submandibular – down and in front of
parotid
3.
Sublingual – under tongue
Trachea – windpipe – part of respiratory
system= air passage
Uvula – prevents food from entering the
trachea
Esophagus - tube
-transfers food to stomach by peristalsis
Cardiac sphincter
-opens to allow food into the stomach
-heartburn –acid escapes stomach and goes
into the esophagus
http://library.thinkquest.org/11226/main/c03txt.htm
Stomach
Short term storage reservoir (1L for up to 4h)
Digestion = chemical (HCl and pepsin) – proteins are broken
down
= mechanical - liquefication of food by peristalsis
Slowly releases food into small intestine
Chyme = released food
Rugae = wrinkles of tissue that line
Cardiac sphincter
Pyloric sphincter
http://35.9.122.184/images/41-AnimalNutrition/41-16-Duodenum-L.gif
inside of stomach – cause increase
in surface area to help with
mechanical breakdown of food
Chemicals found in stomach
Mucus – prevents self digestions
Pepsin –
Acid (HCl) –
Stomach epithelial cells are
some of the fastest growing
cells in the body, typically
replacing themselves
about every 3 days
Converts proteins to smaller peptides
pH 1-2
Kills bacteria
Loosens fibrous foods
Activates pepsin
Denatures salivary amylase
Ulcers (stomach, duodenum) –
peptic ulcers. Most commonly
caused by excess acid, stress
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
Mesentery = tissue that hooks
intestine to abdomen wall
Small Intestine cont.
Duodenum = = 25cm long – where the majority of
food and water absorption occurs
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 to the cells
Large Intestine
1.5m long, 6cm diameter
Food stays 10h to a few days
Reabsorbs remaining water,
vitamins and minerals – so waste is
converted to semi-solid = feces
Diarrhea, constipation- Excess
orlack of water absorption
Fiber helps stimulate peristalsis
Appendix
Function unknown – in
herbivores they
contain bacteria that
help digest cellulose
Bacteria
1-2kg of bacteria in your gut = 4000 species
Bad - bacteria that can cause illness e.g. H pylori (ulcers), Salmonella, E. coli,
Listeria (food poisoning)
Good – symbiotic bacteria. These live in close harmony with the body without causing
harm, and have additional health benefits. Probiotics are live micro-organisms that,
when consumed in adequate amounts, confer a health benefit to the host.
e.g. bifidobacteria, lactobacillus
•Aid digestion
•Break down toxins
•Produce vitamins B12 and K
•Stimulate the immune system
•Help prevent growth of cancers
•Convert prodrugs to drugs
Accessory Organs
Pancreas –releases pancreatic juice= sodium bicarbonate (a base), enzymes (insulin, glucago
to the duodenum = pH of duodenum = 7-8
Enzymes =Amylase, lipase, trypsin, chymotrypsin
Enzymes act on starches, fats, and proteins
Liver –
Bile made in liver, stored in gall bladder = contains water, salts, bile salts
Neutralizes HCl
Digestion and absorption of fats and fat soluble vitamins (emulsification)
Waste products eliminated by secretion into bile and elimination in feces
Liver
Right lobe
Left lobe
Blood rich in
food from ileum
The liver performs over 500 jobs. Some of these are:
•Makes bile (600mls/day)
•Detoxifies body (alcohol, drugs etc)
•Breaks down excess amino acids to urea Converts
• Converts glucose to glycogen for storage (source of quick
energy)
•Converts excess carbohydrates to 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 –helps the body’s white blood cells -destroy
bacteria
•Produces hormones, including the sex hormones
http://www.britishlivertrust.org.uk/content/liver/about.asp
Gall Bladder
• Stores and
concentrates
bile