Chapter 5 : Nutrition In Humans Flashcards
State the pathway which food takes through your digestive system (8)
Mouth —> Pharynx —> Larynx —> Oesophagus —> stomach —> Small intestine —> Large intestine —> Rectum —> Anus
Name the 4 accessory organs in your digestive system and their functions
- Salivary glands (Produces saliva which moistens food and salivary amylase)
- Liver ( produces bile)
- Gallbladder (stores and secretes bile)
- Pancreas (Secretes insulin, glycogen, as well as pancreatic juice which contains amylase, lipase and protease )
State what type of muscles are circular and longitudinal muscles and hence what are their uses
The circular and longitudinal muscles are antagonistic muscles. When the circular muscles constrict the lumen, the longitudinal muscles lengthen the lumen.
These contractions are known as peristalsis and help to
A) mix food with digestive juices
B) moves food along the gut
What is physical digestion and where does it occur ?
The mechanical break up of food into smaller smaller particles
It occurs in
A) the mouth ( mastication )
B) the stomach (churning breaks up food and mixes them with digestive enzymes)
What is the purpose of physical digestion
To incr SA:V so that the digestive enzymes can act on the food more efficiently
What is chemical digestion
Breaking down of large molecules in food into small soluble molecules which can be easily absorbed. Involves hydrolytic reactions catalyse by digestive enzymes
What is the pH value in the
a) Mouth
b) Stomach
c) Small intestine
a) around 7
b) 2
c) around 7
Name the 2 enzymes present in gastric juice and their main function
Pepsin and renin
Pepsin digests protein to polypeptides
Renin curdles milk proteins by converting the soluble caseinogen into insoluble casein. This prevents the proteins from passing through the stomach as easily as water and allows the caesin to remain long enough to be digested by the pepsin
The partly digested food becomes liquified forming ____ , ____ passes in _____ amounts when the _______ ________ relaxes and opens
Chyme, chyme, small pyloric sphincter
As Chyme enters the small intestines, which 3 liquids are secreted
Intestinal juice, Pancreatic juice, Bile
What is the function of HCl in the stomach ?
1) stops action of the salivary amylase by denaturing it
2) changes inactive forms of enzyme, pepsinogen and prorennin, to active forms pepsin and renin
What does pancreatic juice contain ? (3)
Amylase ( Starch to maltose )
Trypsin ( proteins to polypeptides )
- trypsinogen needs to be activated by enterokinase in intestinal juice
Lipase (fats to glycerol and fatty acids)
What does intestinal juice contain ? (4)
Enterokinase (activates trypsinogen)
Disaccharidase ( Disaccharides into monosaccharides)
Erepsin ( Polypeptides to amino acids )
Lipase ( Fats to glycerol and fatty acids )
Function of bile
Emulsify fats by reducing the attractive forces between fat molecules, turning large fat globules into tiny fat droplets
Adaptation of Small intestine (4)
- Length ( longest part of alimentary canal )
- Internal SA (Increase SA:V)
- Absorption across thin membrane (epithelium is 1 cell thick)
- Capillary Network ( dense network close to epithelium to carry absorbed food particles away quickly, maintains conc grad between ileum ad blood capillaries to aid in diffusion )
How do microvilli help in absorption (2)
- Presence of Microvilli ( small finger-like projections which further increase SA
- Movement of Villi ( Villi move back and forth independently, increases rate of absorption )
How are nutrients absorbed in the Small Intestine (3)
Amino acids and simple sugars
—> Mainly Active transport and diffusion
—> to the capillaries, then transported to the liver through the hepatic portal vein
Fatty Acids and Glycerol
—> Absorbed into the lacteal and transported to the lymphatic system
Name the process in which faeces are discharged from the body
Egestion
Difference between hepatic portal vein and hepatic vein
Hepatic portal vein
- transports water soluble nutrients
- ileum to the liver
- nutrient rich but deoxygenated blood
Hepatic vein
- transport waste products away from liver
- deoxygenated good and nutrient poor
Function of the hepatic artery
Transport oxygenated but nutrient poor blood form aorta to liver
How is glucose assimilated in the body ? ( 3 )
Excess glucose is converted into glycogen for storage in the body.
It is converted back into glucose when blood sugar level is low (Glucagon)
Used in cellular respiration
How is fats assimilated in the body ? (3)
Stored in the adipose tissue to be used when glucose and glycogen is used up.
Acts as a layer of insulation under the skin
Used in synthesis of cell membrane
How are amino acids assimilated in the body ? ( 2 )
Used in the synthesis of proteins, enzymes and hormones
Excess mini acids are delaminated in the liver to form urea and glucose
Why is dietary fibre important in a person’s diet ?
Dietary fibre (roughage) helps in peristalsis by increasing the movement of food/ materials in the alimentary canal.
Gives volume to the food / faeces for muscle contractions to push the food.
Increased movements prevent over absorption of water in the alimentary canal
Prevents constipation
What is glycogenesis ?
Process of converting glucose to glycogen, stimulated by the hormone insulin
What is Glycogenolysis
Process of converting glycogen to glucose, stimulated by the hormone glucagon
Name the 9 functions of the liver (9)
- Regulation of blood glucose concentration
- Production of bile
- Iron storage
- Heat production
- De-amination of excess amino acids (converted to glucose)
- Protein synthesis
- Detoxification
- Regulation of blood levels of amino acid levels
- Production of special proteins and cholesterol
