Question

Describe the process through wish a desert is digested. The dessert is predominantly composed of water, sucrose, protein, fat and a small amount of fibre. List the correct order of structures the dessert will go through, from beginning to end and the function of each structure. Give details about the mechanical & enzymatic events mediating digestion (including hormonal processes). Lastly, explain where and how the nutrients would be absorbed.

Answer 1

STRUCTURES IN THE PROCESS OF DIGESTION AND ABSORPTION

STRUCTURE     FUNCTION

1. Mouth Ingest food, chews and mixes food,allow to taste the food,moves food in to pharynx, begins chemical breakdown of carbohydrates

2.Pharynx Propels food from mouth to oesophagus

3.Oesophagus Propels food to stomach(peristalsis)

4.Stomach Mix the food with gastric juice to form chyme, Stimulate protein digesting    enzyme,Absorb some fat soluble substances,Antimicrobial activities,   begins chemical breakdown of protein, secrete intrinsic factor for vit B12 absorption

5.Small intestine Mix chyme with digestive juice,propels food slowly for digestion and absorption,absorb breakdown products of carbohydrate ,protein,and fat, enzymatic activity

6.Large intestine further breakdown of food residues,absorb most residual water,electrolytes and vitamins produced by enteric bacteria, eliminate feces, propels feces towards rectum

7.Accessory structures Liver:produce bile salts

Gallbladder:release bile

Pancreas:Produce digestive enzymes and bicarbonates

MECHANICAL AND ENZYMATIC ACTIVITY OF DIGESTION

1.Mouth

Salivary digestion

Process: Mastication

starch   Ptyalin(enzyme)   dextrin and maltose

No protein and fat digestion takes place in the mouth

PERISTALSIS TAKES PLACE IN THE OESOPHAGUS

2.Stomach

-There is no digestive action of carbohydrate in stomach

-Proteins  pepsin   proteoses and peptones

( A hormone called gastrin stimulate the release of pepsin)

gastrin stimulate parietal cells to release hydrochloric acid. it convert inactivated pepsinogen to pepsin.

milk protein   rennin(enzyme)   casein

casein+calcium calcium caseinate pepsin peptones

- In the stomach fat forms a coarse emulsion and eventuallu released in to duodenum.

3.Intestine

-starch amylase(pancreatic juice)   maltose

sucrose   sucrase or invertase  glucose and fructose

-pancreatic juice contain enzymes trypsin and chymotrypsin. They hydrolyse peptones and proteoses into polypeptides.

polypeptides erepsin(secreted by intestinal mucosa)   amino acids

-pancreatic juice   pancreatic lipase hydrolyses neutral fat fatty acids and mono glycerides

liver   bile salt   detergent action on fat

intestinal lipase   neutral fat   glicerol and fatty acids

ABSORPTION OF NUTRIENTS

-The end product of carbohydrate digestion glucose fructose and galactose are absorbed in the intestine.

bulk amount in the duodenum and jejunum

small amount in the ileum

glucose and galactose readily absorbed

fructose slowly absorbed

absorption of carbohydrate from intestine is controlled by glands like anterior pituitary thyroid and adrenal cortex.

-Amino acids are absorbed by the small intestine and they are carried to the tissue or to the liver. 11% of total protein is absorbed by stomach, 60% by the intestine and 28% by colon.

-Bile salts promote emulsification and help the fat into partial solution og fats and fatty acids. The water-soluble Glycerol is quickly absorbed. Cholesterol esters are converted to bile acids in the liver, re-excreted into the small intestine and reabsorbed.

-THE FIBER IN FOOD PASSES INTO THE INTESTINE AND ABSORBES WATER. THE UNDIGESTED FIBER CREATES BULK, SO THE MUSCLES IN THE INTESTINE CAN PUSH WASTE OUT OF THE BODY.  

-THE SMALL INTESTINE, AT AROUND TWENTY FEET LONG, EFFICIENTLY ABSORBES WATER INTO THE CELL MEMBRANE AND BLOOD STREAM. A SMALL PORTION OF ALL WATER ABSORPTION OCCURS IN THE STOMACH AND THE COLON.