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A large part of protein digestion occurs in the stomach ( [link] ). The stomach    is a saclike organ that secretes gastric digestive juices.

Protein digestion is carried out by an enzyme called pepsin    in the stomach chamber. The highly acidic environment kills many microorganisms in the food and, combined with the action of the enzyme pepsin, results in the catabolism of protein in the food. Chemical digestion is facilitated by the churning action of the stomach caused by contraction and relaxation of smooth muscles. The partially digested food and gastric juice mixture is called chyme    . Gastric emptying occurs within two to six hours after a meal. Only a small amount of chyme is released into the small intestine at a time. The movement of chyme from the stomach into the small intestine is regulated by hormones, stomach distension and muscular reflexes that influence the pyloric sphincter. The low pH of the stomach will denature the amylase and lipase that were secreted in the mouth. Therefore, over time, chemical digestion of starches and fats will decrease in the stomach.

The stomach lining is unaffected by pepsin and the acidity because pepsin is released in an inactive form (pepsinogen) that is activated by the low pH. The stomach also has a thick mucus lining that protects the underlying tissue.

Small intestine

Chyme moves from the stomach to the small intestine. The small intestine    is the organ where the digestion of protein, fats, and carbohydrates is completed. The small intestine is a long tube-like organ with a highly folded surface containing finger-like projections called the villi. The top surface of each villus has many microscopic projections called microvilli. The epithelial cells at the surface of these structures absorb nutrients from the digested food and release them to the bloodstream on the other side. Methods of transport previously discussed (e.g.active transport)are used during this movement. The villi and microvilli, with their many folds, increase the surface area of the small intestine and increase absorption efficiency of the nutrients.

The human small intestine is over 6 m (19.6 ft) long and is divided into three parts: the duodenum, the jejunum and the ileum. The duodenum is separated from the stomach by the pyloric sphincter. The chyme is mixed with pancreatic juices, an alkaline/basic solution rich in bicarbonate that neutralizes the acidity of chyme from the stomach. This result raises the pH and creates an environment that is appropriate for enzymes. Pancreatic juices contain several digestive enzymes (amylase, trypsin, and lipase) that break down starches, proteins, and fats, respectively. Bile is produced in the liver and stored and concentrated in the gallbladder; it enters the duodenum through the bile duct. Bile contains bile salts, which make lipids accessible to the water-soluble enzymes. This is accomplished via a process called emulsification, a type of physical digestion. Bile keeps fat droplets from coming back together again, thus increasing the surface area available to lipase. The wall of the small intestines secrete disaccharidases, which faciltate digestion of disaccharides (e.g. maltose, sucrose, and lactose) into their respective monosaccharides. The monosaccharides, amino acids, bile salts, vitamins, and other nutrients are absorbed by the cells of the intestinal lining.

Questions & Answers

what is genetic engineering
Ebot Reply
good day please what is a cell?
Colota Reply
cell is the basic unit of all living things/organism
differenciate b/w cilia and flagellum
Cilia: 1. They are smaller in number. 2. Cilia usually occur throughout or major part of the surface of a cell. 3. They beat oar like and in a co-ordinated rhythm 4. Cilia help in locomotion, feeding, circulation, etc.. 5. Example: Paramecium
Flagella: 1. They are larger in size. ADVERTISEMENTS: 2. Flagella are commonly found at one end of the cell. 3. The flagella beat whip-like and independently. 4. Flagella help in locomotion. 5. Example: Euglena
smallest structural and functional unit of an organism!
cell is the basic unit of all living things
what is homeostasis
alex Reply
the ability of an organism to maintain stable internal environment, even when the external environment changes
what's the function of the hypothalamus
what is homeostasis
Edward Reply
constant maintenance of internal body temperature
What is the function of the Pituitary Gland?
how can homeostasis be maintained?
pituitary gland also known as the master gland secretes hormones which triggers other gland to secretes their hormones
what's the full meaning of DNA and RNA
Deborah Reply
DNA is Deoxyribonucleic acid and RNA means Ribonucleic acid
sha is mitochondria?
Sparrow Reply
what is biology
Femi Reply
biology is the study which deals with the study of the biological components or animal and plants.
biology is the study of life.
biology is the branch of science which deals with study of two parts 1.botany&2zoology these is known as biology....
biology is the study of human beings ...
Biology is a branch of science that deals with the study of nature
biology is the science of living organism
biology is the branch of science that deals with study of living organisms
what is neculer cell?
is it nuclear cell?
asthma occur in which part of the body organ?
Festus Reply
what is hemoglobin
Lucky Reply
a protein that carries oxygen, it is found within red blood cells
Apart from endocrinology, what other alternative should be done to a D/m client
Deborah Reply
good day please what is excretion
Blaise Reply
excretion is the process by which metabolic wastes and other none-useful materials are eliminated from an organism.
its the process of eliminating or removal of metabolic waste and non useful materials from an organ.
Its the removal of metabolic waste product from the body
it is the removal from the body of living organisms, toxic waste products of metabolism which if allowed to accurate can cost harm to the body..
how are protons formed?
Brian Reply
What is isotopes?
isotopes is a phenomenon in which atoms of the same element has the same atomic number but different mass number due to a difference in their neutron number or relative abundance in the earth crust
give me more mcqs there r just two mcqs
Salma Reply
Define the term Disease in one paragraph.
Sutanya Reply
Disease is any disorders that counteract with the normal performance of the immune system.
what is cell?
Cell is the basic unit of life It is the building block of an organism
do agree with me that if someone needs to truely be a biologist he should be mathematician physicist & chemist in oreder to acheive the level #biologist
what is a protoplasm?
colourless living part of the cell
what is protoplasm made up of?
what are the social differences between man and primates
flore Reply
Hy what is the meaning of DNA

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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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