● The `color{violet}("intestinal mucosal")` epithelium has `color{brown}("goblet cells")` which secrete `color{violet}("mucus.")`

● The secretions of the `color{brown}("brush border cells")` of the `color{violet}("mucosa")` alongwith the secretions of the `color{brown}("goblet cells")` constitute the intestinal juice or `color{brown}("succus entericus.")`

● This `color{violet}("juice")` contains a variety of enzymes like disaccharidases (e.g., maltase), dipeptidases, lipases, nucleosidases, etc
.
● The `color{violet}("mucus")` alongwith the `color{violet}("bicarbonates")` from the `color{violet}("pancreas")` protects the `color{violet}("intestinal mucosa")` from acid as well as provide an alkaline medium (`color{brown}("ph 7.8")`) for enzymatic activities.

● `color{violet}("Sub-mucosal glands")` (`color{brown}("Brunner’s glands")`) also help in this.

● `color{violet}("Proteins, proteoses")` and `color{violet}("peptones (partially hydrolysed proteins)")` in the chyme reaching the intestine are acted upon by the `color{violet}("proteolytic enzymes")` of pancreatic juice as given below:

`color{violet}[tt ( ("Proteins"), ("Peptones") , ("Proteoses")) }] color{violet}[underset("Carboxypeptidase") overset("Trypsin/Chymotrypsin")→ "Dipeptides"]`

● `color{violet}("Carbohydrates")` in the chyme are hydrolysed by pancreatic amylase into disaccharides.

`color{violet}("Polysaccharides (starch)" overset("Amylase")⎯→ "Disaccharides")`

● `color{violet}("Fats")` are broken down by `color{violet}("lipases")` with the help of bile into di-and monoglycerides.

`color{violet}(" Fats" overset(" Lipases")→ "Diglycerides" → "Monoglycerides")`

● Nucleases in the pancreatic juice acts on nucleic acids to form nucleotides and nucleosides

`color{violet}("Nucleicacids" overset("Nucleases")→"Nucleotides" → "Nucleosides")`

● The enzymes in the succus entericus act on the end products of the above reactions to form the respective simple absorbable forms.

● These final steps in `color{violet}("digestion")` occur very close to the `color{violet}("mucosal epithelial cells")` of the intestine.

`color{violet}("Dipeptides" overset("Dipeptidases")→ "Amino acids")`

`color{violet}("Maltose" overset("Maltase")→"Glucose + Glucose")`

`color{violet}("Lactose" overset("Lactase")→"Glucose+Galactose")`

`color{violet}("Sucrose" overset("Sucrose")→"Glucose+Fructose")`

`color{violet}("Nucleotides" overset("Nucleotides")→"Nucleosides" overset("Nucleosides")→"Sugars+Bases")`

`color{violet}("Di and Monoglycerides" overset("Lipases")→"Fatty acids +Glycerol")`

● The breakdown of `color{violet}("biomacromolecules")` mentioned above occurs in the `color{violet}("duodenum region")` of the small intestine.

● The simple substances thus formed are absorbed in the jejunum and ileum regions of the small intestine.

● The undigested and unabsorbed substances are passed on to the `color{violet}("large intestine.")`

● `color{brown}("No significant digestive activity")` occurs in the `color{violet}("large intestine.")`

● The functions of `color{violet}("large intestine")` are:

(i) Absorption of some `color{violet}("water, minerals")` and `color{violet}("certain drugs.")`
(ii) Secretion of `color{violet}("mucus")` which helps in `color{violet}("adhering the waste")` (undigested) particles together and lubricating it for an easy passage.

● The undigested, unabsorbed substances called `color{brown}("faeces")` enters into the `color{violet}("caecum")` of the `color{violet}("large intestine")` through ileo-caecal valve, which prevents the back flow of the `color{violet}("faecal matter.")`

● It is temporarily stored in the `color{violet}("rectum")` till `color{brown}("defaecation.")`