ïGut also have taste receptors and can sense the
basic tastes in a man ner sim i lar to tongue.
Do you know?
The gastrointestinal tract has ability to sense and respond
specifically and differentially to the composition of a meal.The
fats and proteins do not stimulate the same endocrine and
exocrine responses as a meal of pure carbohydrate. The
traditional sensory receptors such as osmoreceptors and
stretch receptors did not seem to respond to biomolecules.
However, new researches and studies have revealed the
existence and role of chemosensory cells or taste receptors.
The gastrointestinal tract is the key interface between the
food and human body and can sense the basic tastes as
tongue. Its epithelial cells use or express G-protein - coupled
receptors and taste linked G-protein gustducin as taste buds.
These receptors taste the luminal content and transmit
signals that regulate nutrient transporter expression and
nutrient uptake as well as the release of gut hormones and
neurotransmitters involved in regulation of energy and
glucose homeostasis.
These receptors play a prominent role in communication
between the lumen, epithelium, smooth muscle cells, afferent
nerve fibres and brain to trigger adaptive responses that
affect gastrointestinal function, food intake etc.
Small intestine is the major site where dietary sugars are
absorbed into the body to provide energy and maintain
normal metabolism. If glucose gets absorbed in excess, it
may result in obesity. T1R3 and gustducin receptors get
expressed in specialised taste cells of gut which sense the
presence of glucose within the intestine and promotes
secretion of Glucagon Like Peptide 1 (GLP-1). It in turn
promotes insulin secretion and regulates appetite.
ïDo you know that stomach provides the most
hostile environment on Earth by being acidic
enough to digest iron nails and yet it allows life
to sustain?
Human stomach is one of the most hostile environments on
Earth, since, it bathes in very strong acids and its walls are
protected by sticky mucus and keeps churning constantly.
This makes the stomach uninhabitable by any life form.
However, it has been discovered that a hardy bacteria thrives
in the formidable environment of stomach. This remarkable
organism Helicobacter pylori has evolved a set of defenses to
escape detection and protection. But this bacteria is not a silent
coloniser in stomach. It exploits the sea of urea as protection
against acidic environment of stomach. A large amount of urea is
released as a result of protein digestion in stomach and is a
nitrogenous breakdown product of amino acids.
The outer membrane of H.pylori consists of ureases, an enzyme
that convert urea into CO 2 and ammonia. Ammonia being a base
combines with H+ to create NH+ 4 ions and reduce acidity. Thus,
protecting themselves from being killed by acidic environment of
stomach. It attacks the lining of stomach which protects it from
the acidic environment, thus causing sores or ulcers. They also
interfere with immune system so as to ensure protection. Most
peptic ulcers are found in duodenum and some in stomach itself.
Though earlier, before the discovery of H.pylori stress, food
habits and high levels of acid and enzyme production was
believed to cause peptic ulcers.ïDefecation is a complex process taking place by
combination of two reflexes and voluntary effort.
Do you know?
Most of the time, the rec tum is empty of faeces, as a weak
func tional sphincter ex ists about 20 cm from the anus, at the
junc ture be tween the sig moid co lon and rec tum which
con trib utes ad di tional re sis tance to fill ing of the rec tum. When a
mass move ment forces faeces into the rec tum, the de sire for
def e ca tion oc curs im me di ately, in clud ing re flex con trac tion of
rec tum and re lax ation of anal sphincters. Usu ally def e ca tion is
ini ti ated by def e ca tion re flexes. One of these is an in trin sic re flex,
me di ated by lo cal en teric ner vous sys tem in rec tal wall. When
faeces en ter the rec tum, dis ten tion of the rec tal wall ini ti ates
af fer ent sig nals that spread through the myenteric plex to ini tiate
peri stal tic waves in de scend ing colon, sig moid and rec tum
forc ing faeces to wards the anus. As the peri stal tic wave
ap proaches the anus, the in ter nal anal sphincter is re laxed by
in hib i tory sig nals from myenteric plexus. And if ex ter nal anal
sphincter is also vol un tarily re laxed at the same time, def e ca tion
oc curs. But this in trin sic myenteric def e ca tion re flex func tion ing
by it self is rel a tively weak, there fore an other def e ca tion re flex,
i.e. para sym pa thetic def e ca tion re flex also co mes into ac tion for
ef fec tive def e ca tion. This re flex in volves sa cral seg ments of
spi nal cord. When the nerve end ings in the rec tum areAmazing facts with proper explanation.
DIGESTIVE SYSTEM
Mukta Gigras