Welcome to our project dedicated to the remarkable process of digestion and absorption in humans! Prepare to embark on an enlightening journey as we explore the intricate mechanisms behind the breakdown and absorption of nutrients in our bodies.
Our presentation offers a comprehensive overview of the digestive system, from the moment food enters the mouth to its final journey through the intestines. Through engaging visuals, informative diagrams, and clear explanations, we unravel the step-by-step process of digestion.
Discover how our teeth, saliva, and enzymes in the digestive tract work together to break down food into smaller molecules. Learn about the roles of the stomach, liver, pancreas, and small intestine in further digestion and nutrient extraction.
Dive into the fascinating world of absorption, where the nutrients derived from our food are transported from the intestines into our bloodstream. Explore the specialized structures and processes involved in absorbing carbohydrates, proteins, fats, vitamins, and minerals.
Uncover the significance of the gut microbiome, the diverse community of bacteria that resides in our digestive system, and its role in digestion and overall health.
Whether you are a student, a health enthusiast, or simply curious about the wonders of the human body, our presentation on digestion and absorption will enlighten and inspire. Join us on this educational journey as we unravel the mysteries and marvels of how our bodies extract vital nutrients from the food we consume
21. 21
Functions of saliva
1. Ptyalin or salivary amylase at pH 7 hydrolyses starch and glycogen into maltose,
isomaltose and limit dextrins
2. Some maltose is hydrolysed into glucose by maltase
3. Mucus in saliva mixes with food and makes it soft and viscous to be easily masticated
by pm and m
4. With saliva the churned food forms a bolus to be swallowed easily. Bolus is the well-
chewed food that is made into a ball-like structure for swallowing in the buccal
cavity.
5. Saliva keeps the tongue and buccal cavity moist and helps in speaking
6. Enzyme polysaccharidase destroys bacteria
7. Bicarbonates, phosphates and mucin act as buffers and neutralise acids in food
8. Saliva helps in tasting of food
9. Lysozyme present in saliva acts as an antibacterial agent that prevents infections
10.Thiocyanate ions- [SCN]− act as an antimicrobial agent and prevent bacterial infection
28. 28
All these secretions collectively form the gastric juice. Its daily
secretion is 2-3l per day. The pH of gastric juice is 1.2 to 1.8. HCl
forms 0.05-0.3% of gastric juice. Gastric juice secretion is stimulated
by the thought of food, smell of food, chewing of food and the contact
of food with the stomach wall.
Functions of HCl:
1. It softens the food and disinfects it by killing bacteria
2. It stops the action of salivary enzymes
3. It activates pepsinogen to pepsin and prorennin to rennin
4. It maintains the appropriate pH value of about 1.8 for protein digestion
5. It controls the function of Castle’s Intrinsic Factor
6. It controls the opening and closing of the pyloric sphincter
29. 29
INTESTINAL GLANDS
Numerous, microscopic glands present in the mucosa of small intestine between the villi and these are of the
following types:
30. 30
Secretion of intestinal glands is called
intestinal juice or succus entericus which is
alkaline with pH 7.8-8.3. About 2-3l of
intestinal juice is secretes per day
47. 47
symbiotic bacteria like Escherichia coli and
residing in the human colon feed on protein contents of the chyle breaking them into
amino acids which are absorbed into the blood
colon bacteria also synthesise vitamins B and K. They convert bile into brown
pigments like stercobilin that give characteristic colour to the faeces.
51. 51
Na+ is transported by simple diffusion and active transport. The absorption of Na+
is coupled with glucose molecule as a symport. Ca++, Mg++, Iron, K+ and PO43- are
taken in by active transport. Absorption of Ca++ is enhanced by vitamin D and
parathormone. Cl- may enter the mucosa by diffusion or active transport
All water soluble vitamins are absorbed by simple diffusion. B12 requires the
presence of Castle’s Intrinsic Factor for absorption.
Absorption of substances takes place in different parts of the alimentary canal,
like mouth, stomach, small intestine and large intestine
However, maximum absorption occurs in the small intestine
A summary of absorption (sites of absorption and substances absorbed) is given
in the table below:
53. 53
The incorporation of absorbed food material into the tissue cells so
that it becomes an integral part of their cytoplasm and is used for
energy, growth and repair process is called assimilation
1. In the body cells fatty acids and glycerol in the form of chylomicrons are
again converted into fat which is stored in adipose tissue to be used again
when there is a metabolic need
2. The glucose formed after digestion is metabolised in every cell to release
energy for life processes. Extra glucose is converted to glycogen which is
stored in the liver and muscle cells. The stored glycogen is used under
conditions of stress
3. Amino acids are utilised by cells to synthesise various types of structural
proteins and enzymes. The excess amino acids are deaminated. Ammonia
released during deamination combines with CO2 to form urea and
eliminated through urine. The deaminated organic molecules of amino
acids are converted into glucose and then into fats for storage
