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Mechanical digestion in the small intestine

The movement of intestinal smooth muscles includes both segmentation and a form of peristalsis called migrating motility complexes. The kind of peristaltic mixing waves seen in the stomach are not observed here.

If you could see into the small intestine when it was going through segmentation, it would look as if the contents were being shoved incrementally back and forth, as the rings of smooth muscle repeatedly contract and then relax. Segmentation in the small intestine does not force chyme through the tract. Instead, it combines the chyme with digestive juices and pushes food particles against the mucosa to be absorbed. The duodenum is where the most rapid segmentation occurs, at a rate of about 12 times per minute. In the ileum, segmentations are only about eight times per minute ( [link] ).


This diagram shows the process of segmentation in the intestines. The left panel shows the separation of chime, the middle panel shows the remixing of the chime by pushing it back together and the right panel indicates that the chime is being digested and absorbed.
Segmentation separates chyme and then pushes it back together, mixing it and providing time for digestion and absorption.

When most of the chyme has been absorbed, the small intestinal wall becomes less distended. At this point, the localized segmentation process is replaced by transport movements. The duodenal mucosa secretes the hormone motilin    , which initiates peristalsis in the form of a migrating motility complex    . These complexes, which begin in the duodenum, force chyme through a short section of the small intestine and then stop. The next contraction begins a little bit farther down than the first, forces chyme a bit farther through the small intestine, then stops. These complexes move slowly down the small intestine, forcing chyme on the way, taking around 90 to 120 minutes to finally reach the end of the ileum. At this point, the process is repeated, starting in the duodenum.

The ileocecal valve, a sphincter, is usually in a constricted state, but when motility in the ileum increases, this sphincter relaxes, allowing food residue to enter the first portion of the large intestine, the cecum. Relaxation of the ileocecal sphincter is controlled by both nerves and hormones. First, digestive activity in the stomach provokes the gastroileal reflex    , which increases the force of ileal segmentation. Second, the stomach releases the hormone gastrin, which enhances ileal motility, thus relaxing the ileocecal sphincter. After chyme passes through, backward pressure helps close the sphincter, preventing backflow into the ileum. Because of this reflex, your lunch is completely emptied from your stomach and small intestine by the time you eat your dinner. It takes about 3 to 5 hours for all chyme to leave the small intestine.

Chemical digestion in the small intestine

The digestion of proteins and carbohydrates, which partially occurs in the stomach, is completed in the small intestine with the aid of intestinal and pancreatic juices. Lipids arrive in the intestine largely undigested, so much of the focus here is on lipid digestion, which is facilitated by bile and the enzyme pancreatic lipase.

Moreover, intestinal juice combines with pancreatic juice to provide a liquid medium that facilitates absorption. The intestine is also where most water is absorbed, via osmosis. The small intestine’s absorptive cells also synthesize digestive enzymes and then place them in the plasma membranes of the microvilli. This distinguishes the small intestine from the stomach; that is, enzymatic digestion occurs not only in the lumen, but also on the luminal surfaces of the mucosal cells.

Questions & Answers

define cell injuries
Siva Reply
it is defined as any damage to structural and functional behaviour of cell...and is not performing appropriately.
what is the proximity of uterus or womb and kidney
Gebregiorgis Reply
answer is needed
hirsi dahir
war hye
i dont know
im just new in here.
im a freshmen student
ok Erik welcome
Am Amina
say ?
proximity of womb that is uterus is urinary bladder..bowel loop(means intestinal loop)..and rectum and that if kidney is..stomach,ureter,spleen in left, duodenum,quadratus lumborum muscle,psoas muscle,ribs(6,7,8),suprarenal gland,jejunum,colic flexure on right,.
hey hlo...m new here..yogesh Jindal🤗🤗guys listen proximity is same the structure lying on it's surfaces..or around it...so all must reply...as each new nd all must know structure around organs...nd vessels too
okz thanks bro me too new .....u all are unknow for me🤔🤔🤔🤔🤔
of course m unknown to all
Maine to ye names hi first tym sune hai
can i ask a question kn you guys?
yes Erik came on we here to answer any questions posted
give me tips about csir net
what do you mean csir net
net conducted by csir
I don't know yet , is there somebody understand what he said
can you give me atleast 20 anatomical terminologies that is not common ? its my assignment in my major.
are you still there?
im asking
ow Erik I learned medical terminology course past years in my University so I Know alot of words in my mind but I can't destinguash comon words and non comon
lower abdomen
can you help me?
for what
give me 20 terminologies that are not common . plz i really need to know. its my assignment in majoy subj
which have same sounds nd different meanings
20 terminologies; 1.TSB(tepid sponge bath) 2.OCU(eye) 3.DERMA(skin) 4.LEUK(white) 5.HYDRO(water)6.S/Sx(signs &symptoms)7.TX(treatment)8.Dx(diagnosis)9MAMM(O)breast10.it is(inflammation)
is that anatomical terminology? and yes including the meaning
yellow marrow has been identified as
Raychelle Reply
Which of the following accurately describe external resipration
Gwendolyn Reply
from the heart to the lungs
I think it's not outside organ of respiratory all respiratory organ are inside of human body
diffusion of CO2 and oxygen at a pulmonary capillary surrounding an alveolar sac.
In other words, from the external environment to the lungs (alveoli) then to the pulmonary capillary then to the heart. So this is a stage of inhalation. inhale = external respiration.
What kind of discussion
horyaal Reply
what is the function of the placenta
Nchimunya Reply
The placenta acts to provide oxygen and nutrientsto the fetus, whilst removing carbon dioxide and other waste products.
Also it's the barrier through which the mother is connected to the fetus.
I want to discuss... atherosclerosis.., everything about it, about to treatment n prevention at age 50 +
Please participate in discussion
ok let's discuss now
first define the word artherosclerosis
a disease of the arteries characterized by the deposition of fatty material on their inner walls.
hardening of the arteries, due to fats..
Q = which type of fat utilized for this.., I.e LDL, HDL, TG, VLDL...?
Atherosclerosis is a condition of deposition of plaque inside the artries
Plaque include such as fat, chalestrol, calcium etc
Thank you kumar...., is there any way that we can protect these plaques without any medicines., I. e exercises n food stuffs
go to the gym
what is chylomicrons?
how can plaque buildup in The angina or vessels ?
Atherosclerosis is a condition of deposition of plaque inside the artries
atherosclerosis can also be caused by tortuousness of arteries with old age as contributing factor.
You tube Prof Fink...he is an amazing lecturer and does a brilliant job on arteriosclerosis
what are cell
Chigozie Reply
The basic structural and functional unit of any living thing. Each cell is a small container of chemicals and water wrapped in a membrane. 
cell is the structural and functional basic unit of life
So every living thing was Created From a Cell
from a fusion of two cells , the sperm and the egg
What is the only bone that doesn't have any articulation?
that magical fusion of cells
why body immune system attack and destroy the body own cell during type 1 diabetes?
Sanamacha Reply
It's an autoimmune disease... targeting the pancreas
what are the three genetic defects of pregnancy?
Belinda Reply
structure of fallopian tubes
Akash Reply
what z the role played by the transport system
zinitha Reply
how fats are digested in the human body
Nabukwasi Reply
Fat digestion begins in the stomach but some argue in that it starts in the mouth. Reason is because the sublingual gland secretes an enzyme called lingual lipase. However, this enzyme is not activated until it comes into contact with gastric fluids (HCl). In the stomach, HCl breaks down the lipid..
due to body heat
into smaller molecules. Going from a triglyceride and a fatty acid to a monoglyceride and a a fatty acid no longer bound to one another. This is known as lipolysis.
After lipolysis in the stomach from gastric and lingual lipase, an acidic chyme is produced after stomach churning the bolus. The chyme exits the stomach at the pyloric sphincter and enters the first section of the small intestine known as the duodenum.
in the duodenum. An alkaline mucus from goblet cells neutralizes the acidic chyme to prevent acid burns. After that, the pancreas and gallbladder secrete a number of enzymes to continue lipolysis. Bile from the gallbladder enters the duodenum via common bile duct. The acinar cells in the pancreas...
secretes pancreatic lipase after enteroendocrine cells in the duodenum secrete a stimulator hormone called CCK. Cck stimulates bile synthesis and secretion as well as pancreatic lipase.
Bile emuslifies the lipid, allowing the lipases to continue lipolysis
this breakdown continues until it reaches the jejunum of the small intestines. At this point, the lipid has been broken down small enough to absorbed into the blood stream. So villi in the jejunum, absorb the contents.
ileum, the last small intestine region, absorbs anything that wasn't absorbed previously. Like minerals, vitamins, bile salts, water soluble material. Villi here complete that task. Fatty acid and glycerol however, are absorbed by lacteals. small lymph vessels. And are transported to the liver.
That concludes lipid digestion. Anything else that remains is deficated after it travels through the large intestines.
parents with blood group AB & 0,,,what will b the blood group of their offspring
what are the different branches of anatomy
hopefully that helped.
which ion is low of blood level?
Ezra Reply
what is coagulation?
feng Reply
liquid turning to solid... blood clots.
coagulation : liquid blood into blood clots caused with a coagulant.
when the blood turn from liquid form to solid
it said to coagulate by the action of active plasma protein called *fibrin*
I.e liquid inform of blood when to solid
it is the process by which blood becomes more viscous or becomes thick
cloting of blood cells
clot of blood
the process of forming semi solid lumps in a liquid
conversion of blood to solid state
semi solid., rather than solid form
what is pivot functioned
to less thefriction
how to calculate the micrograph
Ampong Reply

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