<< Chapter < Page Chapter >> Page >

The three lipases responsible for lipid digestion are lingual lipase, gastric lipase, and pancreatic lipase    . However, because the pancreas is the only consequential source of lipase, virtually all lipid digestion occurs in the small intestine. Pancreatic lipase breaks down each triglyceride into two free fatty acids and a monoglyceride. The fatty acids include both short-chain (less than 10 to 12 carbons) and long-chain fatty acids.

Nucleic acid digestion

The nucleic acids DNA and RNA are found in most of the foods you eat. Two types of pancreatic nuclease    are responsible for their digestion: deoxyribonuclease    , which digests DNA, and ribonuclease    , which digests RNA. The nucleotides produced by this digestion are further broken down by two intestinal brush border enzymes ( nucleosidase    and phosphatase    ) into pentoses, phosphates, and nitrogenous bases, which can be absorbed through the alimentary canal wall. The large food molecules that must be broken down into subunits are summarized [link]

Absorbable Food Substances
Source Substance
Carbohydrates Monosaccharides: glucose, galactose, and fructose
Proteins Single amino acids, dipeptides, and tripeptides
Triglycerides Monoacylglycerides, glycerol, and free fatty acids
Nucleic acids Pentose sugars, phosphates, and nitrogenous bases


The mechanical and digestive processes have one goal: to convert food into molecules small enough to be absorbed by the epithelial cells of the intestinal villi. The absorptive capacity of the alimentary canal is almost endless. Each day, the alimentary canal processes up to 10 liters of food, liquids, and GI secretions, yet less than one liter enters the large intestine. Almost all ingested food, 80 percent of electrolytes, and 90 percent of water are absorbed in the small intestine. Although the entire small intestine is involved in the absorption of water and lipids, most absorption of carbohydrates and proteins occurs in the jejunum. Notably, bile salts and vitamin B 12 are absorbed in the terminal ileum. By the time chyme passes from the ileum into the large intestine, it is essentially indigestible food residue (mainly plant fibers like cellulose), some water, and millions of bacteria ( [link] ).

Digestive secretions and absorption of water

This image shows the human digestive system. Next to each organ, a text callout identifies how water and digestive secretions such as saliva and bile are processed.
Absorption is a complex process, in which nutrients from digested food are harvested.

Absorption can occur through five mechanisms: (1) active transport, (2) passive diffusion, (3) facilitated diffusion, (4) co-transport (or secondary active transport), and (5) endocytosis. As you will recall from Chapter 3, active transport refers to the movement of a substance across a cell membrane going from an area of lower concentration to an area of higher concentration (up the concentration gradient). In this type of transport, proteins within the cell membrane act as “pumps,” using cellular energy (ATP) to move the substance. Passive diffusion refers to the movement of substances from an area of higher concentration to an area of lower concentration, while facilitated diffusion refers to the movement of substances from an area of higher to an area of lower concentration using a carrier protein in the cell membrane. Co-transport uses the movement of one molecule through the membrane from higher to lower concentration to power the movement of another from lower to higher. Finally, endocytosis is a transportation process in which the cell membrane engulfs material. It requires energy, generally in the form of ATP.

Questions & Answers

epinephrine is the true meaning of epi
Michele Reply
what does the word 'epi' means
Melex Reply
good evening, my question is what are function of metal in human body like aluminum?
Yosef Reply
please want you to help me in understanding digestive system
Hamidu Reply
this is muscular system?
Patel Reply
bruh moment
It is an organ system consisting of skeletal ,smooth and cardiac muscles
im too retarded to be here
naww Viana, I know it's hard to absorb info, I'm having the same issue, but keep practising, chin up.
what is the question
to have a better understanding as to how our human bodies function. the knowledge we gain can improve our quality of life. Without our study of anatomy how could a doctor know what prescription to give us when our bodies is being attacked by a bacteria? We wouldn't!
Robin Reply
discuss nervers system in human being life.
Allen Reply
neuralgia what is other name of it
how are neurons adapted to their function
Namiyaba Reply
machenic support production of blood cells locomotion protection of delicate organs
Ackson Reply
what are hormones?
what is anatomy
Juma Reply
what are the functions of bones
To support and control the movements of the body
the study of human body is called anatomy
the study of human body is nt only anatomy but also physiology and histology
ooops lol I thought Michael was the one with the questions so sorry people. yes anatomy is the study of the body(structure)and it's physiology (functions).
what are the muscles of respiration?
Hi everyone, Why actyl choline decreases blood pressure although it affects adrenal gland leading it to secret adrenaline and noradrenaline which increase blood pressure?
cholinergic receptors are mostly under Parasympathetic response while adrenergic (norepinephrine) receptors are mostly sympathetic although they are cholinergic adrenergic receptors as well
why do I have pain in my right side of the stomach I had ulcer
go to gastro physician may be but some time it is a gas
vocal cords
MT Reply
musah was admitted to your ward yesterday with traumatic amputation of the right thump . he complained this morning that he has not passed enough urine. Questions. 1) will you consider his complain to be pathological or physiological?. 2) in less than three sentences, justify your opinion. 3) Apply your understanding of the renin- angiotensin-aldosterone system to explain the factors and mechanisms accounting for his complains.
Ellen Reply
please i want you guys to help understand digestive system
digestive system is the system that ingestion breakdown by mechanical and chemicals via mouth to stomach throughout alimentary canal
please alimentary canal what it is and it functions
Ellen de condition is physiological, traumatic amputation causes the body to go to shock in which less blood is sent to the organ (kidney) causing decreased in blood pressure in the renal tubules and low glomerular filtrate will be produced as ultrafiltration can't occur.
Alimentary canal is a long tube that runs from the mouth to the anus and helps in peristalsis and digestion of food to smaller soluble particles to be absorbed into the blood and assimilated into the cells for to obtain energy for cellular function
much thanks
accessory organs it functions
which accessory organs
that's the tongue,salivary gland and the teeth
accessory organ the organ which not part of digestive tract e.g tongue salivary gland liver pancreas gallbladder etc which heps in digestion
salivary glands (parotid, sublingual and submandibular) for secreting saliva for lubrucation and salivary amylase in carbohydrates breakdown in the mouth.teeth helps in chewing, tongue rolls de food into bolus.gallbladder stores biles produced by the liver and helps emulsify fats.liver detoxify food
my question is what is the location of pituitary gland in anatomy
what is average value of hair at scalp give me answer .if no one know about answer .so than I given answer
The value of hair at scalp is 100.000
please explain
100000 to 150000 scalp
OK good
where is cartilage present in large amount a)Thoracic cage b) head c) lower limb d)upper limb
the human scalp has almost 100000 to 150000 hair follicles from hair grow and come out the life of single hair grows have three different stages of hair growth it is considered normal if have lose 50 hairs approx
thoracic cage have 12
what is AV node?
amir khan
pituitary gland is small oval shape which present in brain
AV stands for atrioventricular node, it consist of cardiac muscle tissue and its lies in the right atrium along the lower part of the interartrial septum..
what is the function of AV and SA nodes
SA node is the pacemaker of the human heart and it generates an electrical signal that cause upper chambers (atria) to contract .. the signal that passes through the AV node to the lower heart chambers (ventricles) causing them to contract or pump ...
Anatomy ?
it is the study of structure and parts of human body
when can someone have a shower after the operation of eyes ?
the mineral salt which break up a large portion of bone tissue is
Aurora Reply
please I need help. musah was admitted to your ward yesterday with traumatic amputation of the right thump. he complained this morning that he has not passed enough urine. Questions. 1). will you consider his complain to be pathological or physiological?.
2). In less than three sentences, justify your opinion.
musah copmlan to be physiological because of:-
cholesterol and triglycerides in simplest terms are fats (lipid) found in blood
Roy Reply
calcium is important for bone density and development. it also helps for safe / normal blood clotting, blood circulation to and from the heart, and muscle movement
please undertand me action potential ?
minimum potential that must be overcomed to cause polarization and stimulate a neuronal response( generate impulse)

Get the best Anatomy & Physiology course in your pocket!

Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?