Nutrition In Humans Flashcards
What is nutrition?
Nutrition is the process by which organisms obtain food and energy for growth, repair, and maintenance of the body.
Definition of absorption
The process of absorbing products of digestion into the body
Definition of assimilation
A process whereby absorbed food are used to provide energy or converted into new protoplasm
What happens during ingestion
• Occurs in the mouth, leading to the buccal cavity
• Involves:
– Teeth-> Breaks down large pieces of food into smaller pieces
– Salivary glands -> Secretes saliva into the buccal cavity via the
salivary ducts
– Tongue-> Mixes food with saliva
– -> Taste buds help identify and select suitable food
Definition of digestion
Breakdown of food
– Large, insoluble food
molecules to smaller,
soluble food molecules
– To be absorbed into the
body
• Two types:
– Physical
– Chemical
What is physical digestion and where it takes place
Involves a mechanical breakdown with no help
of chemicals (enzymes)
• Occurs in:
– Mouth (Teeth & Tongue)
– Oesophagus
– Stomach (Stomach walls)
• Increases the surface area to
volume ratio of the ingested
food so that digestive
enzymes can act on the food
more efficiently.
How does physical digestion occur in the mouth
• Teeth
– ‘cuts’ and grinds the food from larger pieces to
smaller pieces
• Tongue
– Mixes the food with saliva
• Mucin softens food
– Rolls the partially digested
food into small bolus
• For ease of swallowing
What is chemical digestion
• Enzymatic hydrolysis of large food molecules
into small food molecules with the help of
digestive enzymes
• Occurs in:
– Mouth
– Stomach
– Duodenum
– Ileum
What is chemical digestion
• Enzymatic hydrolysis of large food molecules
into small food molecules with the help of
digestive enzymes
• Occurs in:
– Mouth
– Stomach
– Duodenum
– Ileum
Chemical digestion in the mouth?
• Partial digestion of starch occurs
• Salivary amylase (pH 7)
– Secreted by salivary glands
– Breaks down the long carbohydrate polypeptide
(starch) into shorter carbohydrate polypeptides
(maltose)
• Enzymatic reaction
– Starch Salivary amylase Maltose
Functions and structures of oesophagus
• Made of 2 layers of
antagonistic muscles:
– Longitudinal
– Circular
• Responsible for the
movement of food along the
gut and mixing of food with
digestive enzymes through
peristalsis and gravity
What is peristalsis
• Rhythmic wave-like contractions of the gut wall
caused by the movement of the two
antagonistic muscles
• The antagonistic muscles are a pair of muscles
whose movements contradict each other i.e.
when one contracts, the other relaxes
• Found throughout the gut from the oesophagus
to the rectum
• Occurs throughout the alimentary canal
