human nutrition

Nutrition

• Taking in of nutrients

Why we eat:

• For energy

• Growth

  • Increase in size and number of cells

• Development

• Repair of damaged cells/tissues

• Prevent disease

  • Survival

Mouth

• Food ingested

• Chewing occurs

  • Mechanical digestion

• Chemical digestion

  • Done by enzymes

  • Breakdown of food molecules into

  • Saliva contains enzymes amylase

    • Produce maltose

      • A disaccharide

• Saliva

  • Starch -(amylase)> maltose

  • Lubricates the food and makes it into bolus ( balls of food); it is easier to swallow

Gullet/oesophagus

• No chemical digestion

• Peristalsis occurs

  • The muscles in the gullet contract-alternately and push the bolus down towards the stomach

Stomach

• Secrets gastric juice containing pepsin and hydrochloric acid

• Chemical digestion

  • Proteins -(pepsin)> polypeptides (amino acids)

  • Hcl - provides the acidic medium for pepsin to function properly

• Churning

  • Stomach contracts to "mix" the chyme (liquid form) of food

    • Mechanical digestion

Duodenum

• The liver and pancreas play an important role here

Liver

• Secretes bile

  • Emulsifies fats

    • This is when bile breaks down fats into smaller fat droplets

      • Mechanical

  • Bile neutralises the food from the stomach, which is acidic, since it is an alkali (contains )

Pancreas

• Secretes pancreatic juice

Ileum

• For absorption of digested/soluble substance

• Fats/lipids  -(lipase)> fatty acids 

• Proteins/polypeptides  -(trypsin)> ammino acids

• Starch and glycogen -(amylase)> disaccharides

  • All of it can NOW be digestible

Adaptations of villas as ideal area for absorption 

• Increases Surface area

  • Presence of microvilli

  • Projection

• Presence of capillary network

• Presence of lacteal

• The thinness of the epithelium lining

  • Speeds up the movement

  • One cell thick

  • It reduces diffusion distance

    • Your substances will take a shorter time

Emulsification

• Breaking down of fats into smaller droplets

Churning

• Contraction of the muscles that will result in squeezing

• Longitudinal

• Diagonal

Teeth

• Causes of dental decay

  • (sugary)Food stays in the mouth and forms plaque by mixing with bacteria

  • This causes (lactic) acid to form when the bacteria respire

  • The acid then eats away or destroys the enamel

    •  It is not the bacteria nor the sugar that destroys enamel but acid does

Diet                                                                                                                                                     

Food that is eaten in one day

A balanced diet contains all the essential elements that the human body needs.

• Humans need six types of nutrients

  • Should also contain fibre

    • Not really a nutrient

    • Not absorbed

    • Passes straight through

      • Passes as faeces

• A diet needs to be balanced with all nutrients

Energy needs

Amount of food energy needed to balance energy expenditure

• Everyone uses energy everyday

  • Age can depend how much you need

  • Your sex can use different energy use as well

  • Different jobs require different energy

• Energy comes from food

  • Too much food,  could be store in fat

  • Too little food, not enough energy needed

    • Could cause tiredness

• All food contains energy

  •  specific kinds of food have different amounts of energy

  • One gram of fat, twice as much in protein and carbohydrate of same weight

• Diets may need to change

  • Pregnant women eat more than they used to

    • Sometimes more protein or more calcium

      • They'll be need for the baby as well

    • Eat more for breastfeeding

  • People eat less when they reach over 50

    • Slowed metabolism

Nutrients

Chemical substance found in every living thing on Earth.

• Food is needed for many reasons

• If you don't have the needed nutrients, your body won't function well

Carbohydrates

• Needed for energy

• Usually in forms of starch

  • Potatoes, wheat, rice, etc.

• In sweet foods too

• Provide glucose in the body

• 45 - 65% of total daily calories

Fats and oils

• Need for energy and make cell membranes

• Excess fat and oil under skin

  • Adipose tissue

    • Connective tissue that is mainly composed of fat cells called adipocytes

    • Energy storing

    • Large globules of fat

      • Lipid droplets surrounded by structural network of fibres

• Insulates

  • Reduces heat loss

• Layers around organs

  • Mechanical protection

  • Cushioning around soft organs

    • Kidneys

• Found in oils, meat, eggs, dairy, etc.

• Can help with absorption of some nutrients

  • Vitamins A, D, and E

  • Fat-soluble

    • Only can be absorbed with help of fats

• Can produce important hormones

  • Leptin

    • Secreted into bloodstream

    • Can reduce the urge to eat

    • Control body manage storage of body fat

    • Regulate energy balance

Proteins

• Build new cells for growth

• Helps with haemoglobin, insulin, antibiotics

• From meat, dairy, beans, seeds, etc.

• 10 - 35% of total calorie needs in a day

• Make hormones and enzymes

  • Growth hormone

  • Prolactin

    • Stimulates milk production after childbirth

Vitamins

• Organic compound

• Needed in tiny amounts

  • They can cause toxicity

• If not enough, you can get a deficiency disease

Minerals

• Inorganic substance

• Small amounts needed

• Same problems as vitamins if not given enough

Fibre

• Helpful in the alimentary canal

  • Part of digestion process

  • Muscles contract and relax

    • Peristalsis

      • Rhythmical muscular contractions that move food through the alimentary canal

    • Softs foods don't require too much muscle work

    • Works harder with tougher food

      • Fiber prevents constipation

      • Help digestive system work well

• All plants contain it

  • Because of cellulose cell walls

  • We can't digest cellulose

    • Used to be the appendix's job

• Great source is husks of cereal grains

  • Oats, wheat, barley

    • Bran

• Found in whole meal bread, unpolished rice

Water

• 60% of human body

• Important solvent

  • Cytoplasm

    • Watery liquid

    • Spaces between our cells

• Inside cells

  • If dries out, cell will stop reactions and die

• Used for chemical reactions

  • Metabolic reactions

• Part of the blood

  • Plasma

    • Mostly water

    • Many substances

    • Transported around body

• Dissolve enzymes and nutrients

  • Digestion help

• Get rid of waste

  • Kidney help

    • Removes urea

      • Dissolved in water

      • Forms urine

• Must from drinking fluids

• From some fruits

  • Contain water

    • Melons, honeydew, cantaloupe, strawberries, etc.

Deficiency diseases

The human digestive system                                                                                                                        

Converts food we eat into simplest forms

• Group organs working together to perform digestion

• Includes liver and pancreas

• Break down food

  • Absorbed into blood

    • Delivered in body cells

• Ingestion

  • Food taken in

  • Drink and food into mouth

  • Use of lips, teeth, tongue

  • Swallowing

• Digestion

  • Large, insoluble molecules broken into smaller molecules

  • Food comes in large pieces

  • Broken down physically and chemically

    • Physical digestion

      • Without chemical change

      • Squeezing and chewing

      • Mostly done by teeth

      • Churning in stomach

    • Chemical digestion

      • With the use of chemicals

      • Stomach acid for example

      • Chemical reactions place

      • Catalysed in enzymes

      • Easier absorption

  • Help food get through walls of intestines and to blood

• Absorption

  • Small molecules and mineral ions though intestines into blood

  • Helps supply nutrients into rest of the body

  • Soaked up

• Assimilation

  • Nutrients become part of body

  • Nutrients into individual cells

    • Energy use

    • Making of new substances

• Egestion

  • Some things we can't digest

    • Fibre

  • Not absorbed

  • Remains in intestine

    • Passes as faeces

    • Removed

The alimentary canal

Long tube that runs down from the mouth to anus

Pathway for food

• For digestion

• Includes liver and pancreas

• Contains muscles

  • Help with physical digestion

  • Contract and relax

    • Push food along

  • Peristalsis

• Some foods kept in one area of the canal for a while

  • Moves after some time

  • Some muscles close the path

    • Sphincter muscles

      • Circular

      • Open and closes

      • Regulate flow of substances

        • Bile, urine, faeces

• Food slides easily because of mucus

  • Lubricates

  • From goblet cells

    • Found in lining

    • Along entire canal

• Each section has each own task

The mouth

• Oval-shaped cavity inside the skill

• Use of teeth, lips, tongue

  • Teeth grind food into small pieces

    • Increase surface area

  • Physical digestion

  • Tongue mixes food with saliva

    • Makes a little ball to be swallowed

  • Salivary glands

    • Makes saliva

    • Makes food moist to swallow easier

    • Has amylase

    • Important for oral health

    • Just below the ear and below the jaw

    • Mixture of water, mucus, amylase

      • Dissolves substances

      • Allows taste

      • Bind into a ball to be swallowed

      • Amylase to digest starch

The oesophagus

• Muscular tube

• Connected to stomach

• Behind trachea

• Hole in the centre

  • Food passes

  • Called lumen

    • Used for anything with space in the middle

    • In all blood vessels

• Entrance in stomach is closed

  • Relaxes to let food in

  • Contracts to close entrance

The stomach

• j-shaped organ

• Has strong, muscle walls

  • Contract and relax

  • Mixes food with enzymes and mucus and with muscle movement

• Contains goblet cells

• Cells for enzymes

• Cells to create hydrochloric acid

  • pH of  2

  • Kills microorganisms

  • Optimum for protease

• Digests proteins

• Can store food

  • After an hour or two stomach exit opens

    • Partly digested food

    • Into duodenum

      • First part of small intestine

      • Pancreatic duct and bile duct

      • Between small intestine and stomach

      • Mixes bile and gallbladder juices

The small intestine

• Between stomach and colon

• 5m long

• Quite narrow

• Has different sections (in order)

  • Duodenum

  • Jejunum

    • Absorbs sugars, amino acids, fatty acids

  • Ilium

    • Absorbs into blood

• Pancreas duct leads into duodenum

  • A tube connecting

• Pancreatic juice

  • Many different enzymes

  • Chemical digestion continued in duodenum

The large intestine

• Final part

• Colon and rectum

  • Rectum is holding area for the stool

    • When full, pushes through anus

  • Receives almost completely digested food

  • Absorbs water and nutrients

  • Passes wase

• End with anus

The pancreas and liver

• Not part of alimentary canal

  • No food passes through

• Pancreas secretes enzymes for the digestion

• Liver secretes bile

  • Alkaline

    • Neutralises acidity in stomach

  • Helps with fat digestion

  • Made in gall bladder

  • Into duodenum through bile duct

  • Yellowish green

  • Watery

Digestion                                                                                                                                                    

• Makes too big of molecules to get through intestine walls

Teeth

• Indigest and mechanical digestion

• Bite pieces of food

• Chop, crush, grind into small pieces

  • Larger surface area

    • Good for enzymes to function

    • Helps soluble molecules in food to dissolve

Chemical digestion

• Sure physical digestion makes food pieces smaller but not enough to be absorbed

• Every part which releases chemical for digestion comes in different pHs

  • Some acidic; some alkaline

  • Some areas need to be neutralized some affected highly by acid

Enzymes in the human digestive system

• Enzymes break the large molecules down

• Amylase

  • Secreted into mouth and duodenum

    • Both areas, do the same thing

    • Break starch down

      • Maltose, if you chew long enough you'll taste sugar

• Maltose

  • Two glucose molecules linked together

  • Smaller than starch

    • Too large to absorb

  • Maltase breaks into glucose

    • From intestine cell lining

      • Epithelium

    • Doesn't go in lumen

    • Attached to epithelial cells

      • Sits on cell membranes

  • Digested in epithelial cells

Starch --amylase--> Maltose --maltase--> Glucose

Protease

• Secreted from stomach and duodenum

• Pepsin

  • From stomach walls

  • Gastric juice

    • Hydrochloric acid

    • Kill harmful microorganisms from food

  • pH 2

  • Acidic conditions

• Trypsin

  • Produced in pancreas

  • Produce amino acids

    • Can be absorbed

  • Break protein

  • pH 7

    • Neutralises

    • Alkaline

  • Bile and pancreatic juice

• Bile

  • Emulsifies fats

    • Fats and oils insoluble

    • Don't fully mix in water

    • Physical digestion

    • Increases surface area

  • Liquid detergent

  • Breaks fat down

    • Doesn't do anything to the fat per say

• Fat-digestion enzyme

  • Lipase

  • Chemically digests

  • Forms fatty acids and glycerol

Absorption and assimilation                                                                                                                                                                         

• When passed through duodenum, large molecules digested to smaller ones

• Carbohydrates into glucose

• Protein into amino acids

• Fats into fatty acids

• Small, soluble molecules pass through

  • Through small intestine

  • Into blood

  • Absorption

• Different small molecules and ions can be small enough to absorb but not digest

Villi

• In walls of small intestines

• Each one 1mm long

• Lines intestine

• Covered in microvilli

  • Tiny folds on the surfaces of the cells of the epithelium of the villi in the small intestines

  • Where maltose acts

  • Breaks into glucose

  • Where everything that can be absorbed is absorbed

• Blood capillaries inside

  • Most substances pass through

  • Join a vein

    • Hepatic portal vein

    • Takes up the substances

    • Blood vessel

• Liver cells

  • Absorb and assimilate

  • Changes glucose to glycogen

    • Storage

  • Amino acids used

    • Make different proteins

    • Returned to blood

    • Broken down into liver into urea

      • Excreted

• Lacteals

  • Fatty acids and glycogen pass through

  • Eventually emptied into blood

Function