<< Chapter < Page Chapter >> Page >

Homeostatic imbalances

Ulcers: when the mucosal barrier breaks down

As effective as the mucosal barrier is, it is not a “fail-safe” mechanism. Sometimes, gastric juice eats away at the superficial lining of the stomach mucosa, creating erosions, which mostly heal on their own. Deeper and larger erosions are called ulcers.

Why does the mucosal barrier break down? A number of factors can interfere with its ability to protect the stomach lining. The majority of all ulcers are caused by either excessive intake of non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin, or Helicobacter pylori infection.

Antacids help relieve symptoms of ulcers such as “burning” pain and indigestion. When ulcers are caused by NSAID use, switching to other classes of pain relievers allows healing. When caused by H. pylori infection, antibiotics are effective.

A potential complication of ulcers is perforation: Perforated ulcers create a hole in the stomach wall, resulting in peritonitis (inflammation of the peritoneum). These ulcers must be repaired surgically.

Digestive functions of the stomach

The stomach participates in virtually all the digestive activities with the exception of ingestion and defecation. Although almost all absorption takes place in the small intestine, the stomach does absorb some nonpolar substances, such as alcohol and aspirin.

Mechanical digestion

Within a few moments after food after enters your stomach, mixing waves begin to occur at intervals of approximately 20 seconds. A mixing wave    is a unique type of peristalsis that mixes and softens the food with gastric juices to create chyme. The initial mixing waves are relatively gentle, but these are followed by more intense waves, starting at the body of the stomach and increasing in force as they reach the pylorus. It is fair to say that long before your sushi exits through the pyloric sphincter, it bears little resemblance to the sushi you ate.

The pylorus, which holds around 30 mL (1 fluid ounce) of chyme, acts as a filter, permitting only liquids and small food particles to pass through the mostly, but not fully, closed pyloric sphincter. In a process called gastric emptying    , rhythmic mixing waves force about 3 mL of chyme at a time through the pyloric sphincter and into the duodenum. Release of a greater amount of chyme at one time would overwhelm the capacity of the small intestine to handle it. The rest of the chyme is pushed back into the body of the stomach, where it continues mixing. This process is repeated when the next mixing waves force more chyme into the duodenum.

Gastric emptying is regulated by both the stomach and the duodenum. The presence of chyme in the duodenum activates receptors that inhibit gastric secretion. This prevents additional chyme from being released by the stomach before the duodenum is ready to process it.

Chemical digestion

The fundus plays an important role, because it stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of salivary amylase continue until the food begins mixing with the acidic chyme. Ultimately, mixing waves incorporate this food with the chyme, the acidity of which inactivates salivary amylase and activates lingual lipase. Lingual lipase then begins breaking down triglycerides into free fatty acids, and mono- and diglycerides.

The breakdown of protein begins in the stomach through the actions of HCl and the enzyme pepsin. During infancy, gastric glands also produce rennin, an enzyme that helps digest milk protein.

Its numerous digestive functions notwithstanding, there is only one stomach function necessary to life: the production of intrinsic factor. The intestinal absorption of vitamin B 12 , which is necessary for both the production of mature red blood cells and normal neurological functioning, cannot occur without intrinsic factor. People who undergo total gastrectomy (stomach removal)—for life-threatening stomach cancer, for example—can survive with minimal digestive dysfunction if they receive vitamin B 12 injections.

The contents of the stomach are completely emptied into the duodenum within 2 to 4 hours after you eat a meal. Different types of food take different amounts of time to process. Foods heavy in carbohydrates empty fastest, followed by high-protein foods. Meals with a high triglyceride content remain in the stomach the longest. Since enzymes in the small intestine digest fats slowly, food can stay in the stomach for 6 hours or longer when the duodenum is processing fatty chyme. However, note that this is still a fraction of the 24 to 72 hours that full digestion typically takes from start to finish.

Chapter review

The stomach participates in all digestive activities except ingestion and defecation. It vigorously churns food. It secretes gastric juices that break down food and absorbs certain drugs, including aspirin and some alcohol. The stomach begins the digestion of protein and continues the digestion of carbohydrates and fats. It stores food as an acidic liquid called chyme, and releases it gradually into the small intestine through the pyloric sphincter.

Watch this animation that depicts the structure of the stomach and how this structure functions in the initiation of protein digestion. This view of the stomach shows the characteristic rugae. What is the function of these rugae?

Answers may vary.

Got questions? Get instant answers now!

Questions & Answers

what is the reason after birth the baby didn't cry
Karthik Reply
what is a cell cycle
GINA Reply
The cell cycle is essentially the life cycle of a cell. In eukaryotic cells, The cell cycle consists of the interphase and mitosis(cellular division).
Carmelo
What is blood
Clare Reply
Blood is composed of plasma and formed elements. Blood plasma is considered extracellular fluid and makes up 55% of blood volume. It contains about 90% water. It also contains nutrients, hormones, gases, ions, proteins, and other molecules. If you have an infection, it might also contain pathogens.
Carmelo
The formed elements are RBCs (45% of blood volume), WBCs and plalets (less than 1% of blood volume) A cool fact is that blood is considered a type of connective tissue since the formed elements of blood comes from mesenchyme stem cells origin.
Carmelo
differences between channel protein and carrier protein in the plasma membrane?
Kumih Reply
does the parietal pleura attached itself to the ribs
Kumih
The main difference is that solutes simply pass through a protein channel, while solutes bind to protein carriers causing a conformational change in the carrier protein and then allows the solute to pass by.
Carmelo
Besides that, both transporters have the same function which is to allow specific solutes in and out of the cell.
Carmelo
The parietal pleura does come in contact with the ribs.
Carmelo
what structure holds the vertebral column in place?
Holly Reply
the ligarmentum flavium
Kumsah
round cushion pads that sit on the between the vertebrae. The intervertebral disc is made up of strong tissue
Kumih
Alimentary canal tissue type
Noob Reply
it consists the oesophagus ,stomach small intestine, large intestine
Kumih
alimentary canal is a type of tissue that consists of mouth, pharynx, oesophagus, stomach, large intestine, small intestine, rectum, and anus
snr
The alimentary canal consists of 4 tunics, and it has all the main tissue types in the body. 1st tunic: Mucosa (simple columnar epithelia) 2nd tunic: Submucosa (dense irregular conn. tissue) 3rd tunic: Muscularis externa (smooth muscle) 4th tunic: Serosa (simple squamous epithelia).
Carmelo
There is also nervous tissue that are present in the muscularis extrena tunic. In the rectum and anus, the mucosal layer contains non keratinized stratified squamous epithelia.
Carmelo
what is epithelial tissue
snr Reply
epithelial tissue is a line in the outer surface of an organism and blood vessels through out the body and inner surface cavities
Kumih
Epithelial tissue is one of the main tissue types on the body. it's main function is to cover and line outer and inner surfaces of organs. For example your skin is epithelial tissue which lines your outer self. The lining of the mucosal layer in your gastrointestinal tract is epithelial tissue.
Carmelo
epithelial tissue is incredibly diverse in function though. It also synthesize and secrets certain products like saliva, hormones, sweat, sebum and mucus.
Carmelo
It also forms structures such as exocrine and endocrine glands, endothelial, and mesothelial membranes as well.
Carmelo
can someone please explain the process lymphatic system
famuyiwa
There are many different types of epithelial tissue and different functions they perform.
Carmelo
@Famuyiwa, the lymphatic organ system contains lymphatic capillaries, vessels, lymph nodes, lymphoid organs and tissues. The lymphatic system is responsible for maintaing blood pressure, filter lymph (activate the immune system), leukopoeiesis, and break down old RBCs.
Carmelo
thanks alot
famuyiwa
welcome, almost forgot, another important function of the lymphatic system is to transports fats inside chylomicrons to the liver and adipose tissue mainly.
Carmelo
This happens after absorption of fats in the enterocytes have occurred and are moved into the latest vessels that lead into lymphatic vessels.
Carmelo
ok
famuyiwa
lacteal*
Carmelo
What is anatomy
Arko Reply
Structures of anatomy
Arko
anatomy is the study of science that deals with how the parts of a body is being structured
snr
anatomy is the study of organisms and the relationship of it's parts
Kumih
tree diagram of the composition of the blood
Poonam Reply
please you said our external hair is dead n non sensational so we the ladies apply cream to it, does it have a negative effect or not?
Abigail Reply
stupiddihedd
Chisom
epithelial tissue connective tissue muscle tissue nervous tissue
Eliham Reply
....
Ruth
Is this a question.. or a statement!!?
Mel
Jesus love us!
Daniel
thank you I needed that!!! praise the lord
Melissa
praise God!
Sherin
lol. it was joke. i am atheist xd
Daniel
so what?
Sherin
Jesus is the only living God.
Sherin
one who find refuge in him will rest with him.
Sherin
isnt this a page to ask for anatomy questions.. not bible study
Mel
Share Jesus without fear all around the world
Sherin
and anywhere you want.
Sherin
ok bible thumper. my ex a preachers daughter was a closet lesbian who f***ed me more times at church then we did hymns
Mel
y'all are the worst hypocrites in the entire world
Mel
that's what you say... but we are living for the our King Jesus not for the world.
Sherin
your king will not save you
Mel
lady you need common sense not jesus
Mel
he's saves me everyday and I do have many testimonies
Sherin
as long as you repent on sundays. y'all are free to sin the rest of the week. but are biggots towards gays and those with a different mindset.
Mel
don't look at anyone else. please clean yourself first
Sherin
lady you are probably a troll
Mel
if you live according to the commandments in Bible, you get saved by Jesus as well
Sherin
I'm not a troll
Sherin
testimonies your kind will say y'all die in his name but dont know his words...
Mel
I'm sharing his word
Sherin
how... amen thats really shows people god exists
Mel
every word in the Bible is in tip of our tongue
Sherin
we live and die for him
Sherin
i think the same. i am atheist because all religions were made for money and authority. they telling us fake stories and scary us.
Daniel
you may have read the bible and may go to church but didnt deny being a biggot
Mel
Jesus do exist and I have experienced it mam
Sherin
not everyone is for money, Daniel
Sherin
again she wont deny shes a biggot
Mel
there are people who are fake in Christianity. I'm not saying there isn't. but there are people who just live for him because they experienced Jesus more in their lives. I will pray for y'all for him to touch you.
Sherin
let him speak to you in Jesus name!
Sherin
but mostly yes. they could do good things too but working in nonreligious organisations. i dont said everyone is bad.
Daniel
I'm not getting any money for telling this you.
Sherin
lady i have gone to church read the bible. and Quran both have truths but you as a whole as in the church are the worst Hippocrits
Mel
find churches that are small in congregation
Sherin
even if they had good intentions they spread bad theories, for example: creationism.
Daniel
all they do is pray
Mel
but wont do anything else
Mel
id love to meet you to see who im talking to from behind a screen who says Ill pray for someone who NEVER ASKED.
Mel
Quran does have truth because they copied it from the Bible. when was Bible written. Things which are happening now are from Bible. Think...when was Bible written? and things happening now from it... so are you saying there's no truth in it?
Sherin
think? they are not the same
Mel
in Quran, it says they have to make other people Muslim or else they have to kill people for their God. is that correct?
Sherin
there are less biggots again you dont deny that. and such nicer people with open arms
Mel
so you haven't read the Bible clearly.
Sherin
read the New Testament and you will figure it out.
Sherin
youll turn away a gay man and welcome a rapist
Mel
while Buddhists and islamics welcome the gays and turn away the phedos
Mel
so you are basically saying that people who worship Jesus are fake people right?
Sherin
i bet you never read the quran ever
Mel
Christianity welcomes everyone, but Church have been taught people come in.
Sherin
omg.... youll try to save rapist before allowing your own blood (child) to live in your homes who comes out gay. or not wanna be a Republican. or a gun holder
Mel
I haven't read it. But in its all hates
Sherin
but they have to change from it.
Sherin
ever person i met who is like you. has a conceal carry. owns a gun. goes to church is republican and doesnt like any races besides there own....
Mel
obviously after knowing his name, they clearly will get away from all the bad thinga
Sherin
my point you believe the bible but wont educate yourself on other beliefs...
Mel
who said that?
Sherin
now tell me if the other assumptions are wrong
Mel
which church or person said that to you?
Sherin
well you wont deny it? so it has to be true.....
Mel
no church saud it. i came from a mostly white town with plenty of racists gun wearing biggots
Mel
they are completely wrong. You think Allah said anywhere in the Quran that "he's coming back soon
Sherin
What's Gun used for? It's for yours or my protection from others right.
Sherin
it's not like you have to kill innocent people.
Sherin
if you or me kill innocent people what will happen?
Sherin
you or me will go to hell only.
Sherin
if someone try to come and fight with you or me. we will take the gun for our protection.
Sherin
allah is always creating and coming back by new life....
Mel
you as a person has no right to say about the quran till you have read it...
Mel
most of the American people have Gun with them. they go to church, they call God, they worship, they do fellowship etc.. for Jesus
Sherin
but again you dont deny your not a racist biggot
Mel
or welcome gays .....
Mel
religion doesn't mean racist.
Sherin
or dont protect rapist... or were you abused and liked it
Mel
I like everyone.
Sherin
rapist shouldn't be doing that. According to Bible it's sin
Sherin
guns shouldnt be owned by those who are not right mentally or ment for harm. but again police use deadly force everyday
Mel
Why does Christian doesn't fight back when they struggle with others?
Sherin
according to the bible we shouldnt wear mixed fabrics....
Mel
But why does Muslims does it?
Sherin
we shouldnt lay with man
Mel
According to Bible gays are sin as well
Sherin
man shouldnt lay with man excuse me
Mel
actually.. they dont
Mel
if you are married, it's okay to lay with a man. because in the Bible it says after marriage, they are one. not 2 anymore
Sherin
but you wouldnt know that since you never studied or educated yourself
Mel
you watch news?
Sherin
How many news I know about hate from Muslims towards Christianity.
Sherin
again your kind would rather protect a rapist who prays than your own kids who hide in the closet as a gay man or woman
Mel
Gun shots around the world done by Muslims towards Christianity in Churches.
Sherin
oh good lord....here we go i watch more news channels than i bet have in a year
Mel
heaven and hell doesnt exist. when we die we end our existence. TOTALY. there is nothing after death. we have only 1 life so dont waste time to pray something whad dont exist, and do some good for other people. we are here and now. everything on the world depends what we do. any god dont do anything
Daniel
and dont get me going on politics or trump lady
Mel
so you know. in America itself, in an year bow many Gun shot happens because of religious hates.
Sherin
who said I'm a trump supporter.
Sherin
I don't support any politics. I only live for Christ.
Sherin
How do you differentiate Haversian canal and Volkmann canal?
Holly Reply
These are differentiated based on location. Haversian canal are present right in the middle of the osteon. the Volkmann canals are located to the sides of Haversian canal and their blood vessels and nerve fibers invade deep into spongy bone in long bones.
Carmelo
thank you
Holly
What are coronal arteries?
julie
The coronary arteries/veins are the group of arteries and veins that supplies the myocardium of the heart.
Carmelo
What is augment
Safia Reply
I don't know
Taufik
Google works wonders at answering questions..
Mel
make greater or numerous
Kumih
how to identify tissues cells under a microscope
Carla Reply
any advice on how to identify tissue cells under a microscope?
Carla
structural and function of the living part
Parthiban
it depends on the specific type of tissue (endothelium, connective etc..). are you asking specifically how to tell different tissues or structures of the tissues apart or how to be able to physically see them?
Holly
What is homeostasis
Haji Reply
ability of living organisms to adjust it internal environment to maintain a stable equilibrium
famuyiwa
how to identify tissues cells under a microscope
Carla

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?

Ask