Digestive System Part 2 - Gastrointestinal Tract Flashcards
when we are done mechanically chewing our food, where does it go?
the oropharynx then into the laryngopharynx
at what point in food ingestion does the epiglottis drop?
at the laryngopharynx
what does the epiglottis do?
block the larynx to force food into the epiglottis
what is the esophagus?
a smooth muscle tube that has muscles that go into two different directions
what are the two types of muscles in the esophagus?
- circular smooth muscles
- longitudinal smooth muscles that run down the wall of the tube
where does the circular smooth muscles in the esophagus contract?
behind the bolus of food
what happens when a circular smooth muscle contracts in the esophagus?
they are going to squeeze and make the lumen of the esophagus smaller to push the bolus down
- longitudinal muscles work simultaneously
how does the longitudinal smooth muscles of the esophagus contract?
- in a wave-like motion to push the bolus down (sort of works with the circular muscles because the ‘pinch’ is in the same area)
how long does the circular and longitudinal smooth muscles of the esophagus contract and relax for?
all the way until we reach the opening of the stomach
what is a sphincter?
circular smooth muscle that when it contracts, it squeezes the tube shut
where is the lower esophageal spincter?
between the bottom of esophagus and the opening of the stomach
- sometimes called the cardiac sphincter because its not too far below the heart
what is the job of the low esophageal spincter?
- open when there is a bolus and let it into the stomach
- close behind the food (real job) because we don’t want the contents of the stomach going back up in the wrong direction
what is the top area of the stomach called?
the fundus
what is the entryway to the stomach called?
the cardia
what is the largest part of the stomach?
the body of the stomach
what are the two smaller, distal areas of the stomach?
- pyloric antrum
- pyloric canal
what happens when a bolus of food enters the stomach?
it spends quite some time in there going through mechanical and chemical breakdown
what are the two curvatures of the stomach?
- lesser curvature (superior side)
- greater curvature (inferior side)
how is mechanical breakdown of food done in the stomach?
squeezing and crushing and sloshing the bolus of food around
what is the difference between each of the 3 muscular layers of the stomach?
the fibres all go in different directions
what happens when all of the walls of smooth muscle in the stomach contract?
you get a lot of crushing of the food that is in the stomach and some sloshing
what does the inner wall of the stomach look like?
sort of lumpy like the brain
- called rugae
where do we find pits in the stomach called gastric glands?
in the rugae of the stomach
- all over inside the stomach
in the gastric glands, there is many types of cells in there. what are they all going to contribute to?
the digestive stuff in our stomach
- digestive enzymes
- mucous
what are the types of cells we can find in our gastric glands?
- surface mucous cell
- mucous neck cell
- parietal cell
- chief cell
- g cell
which gastric gland cells are the most superficial?
- surface mucous cell
- mucous neck cell
what do the superficial gastric gland cells produce?
mucous
why is fluid/mucous so important in the breakdown of food?
it allows us to chemically separate all the food and helps with the mechanical breakdown (makes it mushier)
what does the gastric gland parietal cell secrete?
- hydrochloric acid
- intrinsic factor
why is hydrochloric acid important in gastric glands?
because it is highly acidic (low pH), which will help us break down protein
- we cannot breakdown protein unless we have a very acidic environment
why is the only place in our body we see hydrochloric acid, is the stomach?
- other areas of the gastrointestinal tract, don’t have the lining in their walls to withstand that level of acid
when would we personally experience how acidic our stomach is?
- when we have vommitted
- if our lower esophageal sphincter for some reason as let stomach contents up into the esophagus and we get that burning sensation (heart burn)
what is gastroesophageal reflux?
an issue in some people when the lower esophageal sphincter does not close properly on a frequent basis
- can cause pain frequently in the esophagus (epithelial cells can be replenished, but still hurts)
what is intrinsic factor, secreted by parietal cells, important for?
the absorption of vitamin B12
- we cannot absorb vitamin B12 without it
what is vitamin B12 very important for?
for red blood cell function
what does chief cells and G cells produce?
digestive enzymes
- helps break down other nutrients and aspects of your food
when all the food is broken down by the stomach, what nervous system brings it where?
the enteric nervous system will send a message to the the pyloric sphincter to tell it that it is ready to be moved along and the food will move into the first section of the small intestine, called the duodenum
where is the pyloric sphincter?
at the bottom/end of the stomach
where is the duodenum in relation to the large intestine and the stomach?
below stomach, behind large intestine
what are the sections of the small intestine in order and how long are they?
- duodenum (10inch)
- jejunum (3ft)
- ileum (6ft)
what is the function of the small intestine?
absorption
where do we absorb all of our nutrients?
the small intestine
because we are absorbing all of our nutrients in the small intestine, what do we need in the small intestine?
- a lot of surface area
- a lot of blood
what is the form of food once it reaches the small intestine?
its molecular component so it can be absorbed
where are we trying to move our nutrients to in the small intestine?
from the interior of the intestine, to into the blood so that it can be distributed to the cells of our body
in order to get our nutrients from the intestine to the blood, what do we need?
- we need to be able to get access to all of the stuff inside our intestine to an area of the wall of the intestine
what gives us the big surface area of our small intestine?
all the bumps
on the inside of the small intestine, there are little bumps what are they?
villi
- then we have microvilli on the villi
- this gives us a big surface area in a fairly compact structure
what do we have inside our villi?
blood vessels
what cells are the walls of our small intestine?
single layer epithelial cells
- makes it very thin
what is allowing easy diffusion of nutrients across from the small intestine to the blood?
the single layer epithelial cells in the wall of the small intestine (makes it very thin)
after the small intestine, where does the blood go?
to the liver to be checked for toxins before it joins the bloodstream
once all of our food has gone through the small intestine, where does it go?
the large intestine
what is the large intestine important for?
- water absorption
- vitamin absorption
(which doesn’t really happen in small intestine because it focuses on carbs, lipids and proteins)
where does the ileum of the small intestine end at?
a sphincter called the ‘ileocecal sphincter’ because its between the ileum and the first part of the large intestine called the cecum
what is the job of the ileocecal sphincter?
to keep things from going back into the small intestine
what is the first part of the large intestine called?
the cecum
where is the appendix?
a pouch that is attached to the medial, posterior portion of the cecum and hangs off
- also called the vermiform appendix
what is the function of the appendix?
apart of the immune system
- immune function
- can recognize bacteria and will send a signal to the immune system to come and get it and to be on the lookout for more
do we need the appendix?
no
- the immune system has many backups
from the cecum, where does the food go?
up the ascending colon
where is the ascending colon located?
the right side of the abdomen
after the ascending colon, where does food go?
the transverse colon
there is a sharp turn to get from the ascending colon to the transverse colon. what is it called?
the right colic flexure (also known as hepatic flexure which means liver and that’s because the liver in located right above it)
what aspect of the large intestine is hanging in front of the duodenum of the small intestine?
the transverse colon
from the transverse colon, where does the food go?
down the descending colon
there is a sharp turn to get from the transverse colon to the descending colon. what is it called?
left colic flexure (sometimes called the splenic flexure because spleen is located right behind it)
is the spleen apart of the digestive system?
no
- located close but it is not involved
from the descending colon, where does the food go?
through the sigmoid colon
from the sigmoid colon, where does the food go?
through the rectum, into the anal canal, to the anus
by the time we get through the large intestine, what is left?
all the aspects of your diet that the body did not want
what is dumped into the large intestine by metabolism and other things?
waste products that would be excreted by the anus
what is the rectum?
the area between the sigmoid colon and the anal canal
what does the anal canal make up in the gastrointestinal tract?
the 1-1.5 inch of the gastrointestinal tract
if we hold onto the excretions in the rectum, anal canal and the anus, what happens?
pain
do we have conscious control of when our waste products are excreted?
yes
how do we control when our waste products are excreted?
we have smooth muscle in the wall of our anal canal
what are the muscles in the walls of the anal canal called?
- internal anal sphincter (smooth muscle / involuntary)
- external anal sphincter (skeletal muscle / voluntary)
what does our internal anal sphincter do since it is involuntary?
it just opens
what is the external anal sphincter connected to?
the levator ani muscle
what is the levator ani muscle apart of? what type of muscle is it?
- apart of the pelvic floor
- it is skeletal muscle (makes it voluntary)
which muscle in the wall of the anal canal can we choose to contract and relax?
external anal sphincter
