Human Nutrition Flashcards by Manny A

Nutrition

The way an organism obtains and uses food

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Autotrophic (eg)

Organism that makes its own food (e.g. plants - photosynthesis)

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Heterotrophic (eg)

Organism that can’t make its own food

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Digestion

The physical and chemical breakdown of food

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need for digestion

Breakdown large food particles until they’re small enough to pass into body cells

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need for digestive system

digest food in single location, individual cells don’t have to contain full range of digestive enzymes

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main stages of digestion

ingestion
digestion
absorption
egestion

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ingestion

Food taken into alimentary canal

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digestion

Food broken down into smaller soluble pieces

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absorption

Movement of digested food from alimentary canal into blood system

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egestion

Removal of unabsorbed material as faeces

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methods for mechanical breakdown of food

teeth
contractions in stomach wall
peristalsis

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peristalsis

waves of muscular action in walls of alimentary canal moving contents along

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what stimulates peristalsis

fibre

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teeth & use

incisors - cutting
canines - tearing
pre molars & molars - crushing/grinding

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dental formula

2(I 2/2 - C 1/1 - PM 2/2 - M 3/3)

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amount of teeth in child and adult

adult - 32
child - 20

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length of oesophagus

muscular tube 25cm long

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location of oesophagus

connects pharynx to stomach

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Function of oesophagus

Food moves down the oesophagus by peristalsis

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Stomach shape

J shape muscular bag

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Functions of stomach

-Stores food for about four hours -churns and mixes food with gastric juice forming chyme
-digests food

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Mechanical digestion in the stomach

peristalsis

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Chemical digestion in the stomach

Use of gastric juice containing: mucus, HCL & pepsinogen

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Mucus

Lines and protects stomach wall

Hydrochloric acid

-Kills bacteria -activates pepsinogen (i.e. pepsin)

Pepsinogen

-activates enzyme pepsin due to hydrochloric acid -pepsin converts proteins into peptides

Cardiac sphincter muscle

Circular muscle which contracts to close entry from oesophagus to stomach

Pyloric sphincter muscle

Circular muscle which contracts to close entry from stomach to duodenum

length of small intestine

5 - 6m long

Function of small intestine

digestion & absorption

Parts of small intestine

duodenum, jejunum, ileum

length of duodenum

25cm

Function of duodenum

digestion

Function of jejunum and ileum

absorb nutrients

adaptations for absorption

Long tube = gives time for absorption Villi = Increase surface area available for absorption of digested food

Villi

Infoldings in lining of small intestine

Functions of large intestine

-Reabsorbs water -produces B group vitamins -digest cellulose

How are functions in large intestine carried out?

by symbiotic bacteria

Symbiosis

Relationship between two organisms where at least one organism benefits

Mutualistic symbiosis

Relationship between organisms where both benefit

Symbiotic bacteria

Obtain food and place to live from humans

Functions of symbiotic bacteria in humans

Produce vitamin B and digest cellulose

Functions of caecum and appendix

Unknown in humans

Rectum

Stores faeces

Functions of the liver (5)

-Produces bile -detoxifies body (alcohol and drugs) -breaks down dead red blood cells -stores vitamins -produces heat to warm blood (respiration)

Bile (colour)

yellow-green liquid

bile (location)

-stored in gall bladder -enters duodenum through bile duct

Bile consists of

- water - bile salts - bile pigments

Functions of bile

-Neutralises acidic chyme from stomach -Emulsifies fats (increases the surface area of fat droplets)

Functions of the pancreas (ie)

-Produces insulin (regulates blood sugar level) -Production of enzymes (i.e. amylase lipase)

Benefits of dietary fibre

-Stimulates peristalsis in colon -Prevents constipation

Constipation

When undigested material passes through colon too quickly

Enzymes involved in digestion

-amylase -pepsin -lipase

Role of salivary amylase

Digest starch

Production site of salivary amylase

Salivary glands

Where does salivary amylase act?

Mouth

PH of salivary amylase in the mouth

8 (alkaline)

Digestion product of salivary amylase

Maltose

Role of pepsin

Digest protein

Production site of pepsin

Gastric glands in stomach wall

Where does pepsin act?

Stomach

PH of pepsin in mouth

2 (acidic)

Digestion products of pepsin

Peptides

Role of lipase

Digest fat

Production site of lipase

Pancreas

Where does lipase act?

duodenum

PH of lipase in mouth

8 (alkaline)

Digestion products of lipase

Fatty acids and glycerol

Features of a balanced diet

-Must contain all necessary food types in correct proportions -food types must be eaten in moderation

Food type is necessary for a balanced diet (7)

Water, vitamins, protein, carbohydrates, minerals, lipid, fibre

Factors that affect food intake

-Age -gender -activity levels