The Digestive System in ASL and English with Paul Buttenhoff and Cara Barnett Produced by Todd Tourville

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The Digestive System - Technical English Transcript

This lecture covers information related to the digestive system consistent with an undergraduate setting. Transcript is below the video. | Back to Technical Lectures

Paul Buttenhoff in English

Closed captioning can be controlled by the CC button in lower right corner.

English Transcript

Hello, my name is Paul Buttenhoff. I’m an Assistant Professor here at the College of St. Catherine in Minneapolis. Today I’d like to talk
to you a little bit about the digestive system, one of 11 major organ systems in your body. Although the digestive system is unique in it’s
own right, we do have to remember that it does function in conjunction with all of the ten other organs systems to allow you to be alive
and to maintain homeostasis. That’s what we are all about.

From an anatomical standpoint the digestive system is divided into two regions or two portions. There is a digestive tract or sometimes
the alimentary canal or gastrointestinal tract that is primarily a 30 foot tube that starts at the mouth and ends at the anus. Different
regions of the alimentary canal are going to be specialized and will be given different names, for example the mouth, the esophagus,
the stomach, the small intestine or the large intestine. In any of these regions we are going to see there are specialized functions. The
accessory organs of the digestive system will contribute to the process. Usually they are not found exactly in the digestive system but
they exist outside, in the periphery. Accessory organs include things like teeth, salivary glands, the liver, the gallbladder and the pancreas
and we will get to their functions in a moment.

If we talk about the digestive system as a whole we can see that it carries out three primary functions for us. First of all at the top end,
the digestive system is designed to allow us to take food and beverages into our body, this process is known as ingestion. The second
step, or the second function, will be known as true digestion. Once food and beverages enter our body we need to be able to break
them down into their smaller usable components. Digestion will occur in several key areas and we will talk about those in a moment.
After material enters your body and is broken down, the third very important step will be known as absorption. Without absorption material
will simply pass through your body and will be unusable to you. Absorption will involve the movement of nutrients, sugars, proteins
and fats, vitamins and minerals, from the alimentary canal or gastrointestinal tract actually into your bloodstream across several layers
of tissues and then they will be available for transport to every other organ system in your body. The fourth function is the waste removal
function. Not everything that you eat is digestible and or absorbable. Your large intestine, which we will get to shortly, will handle the
removal of feces from the body.

What we are going to do today is pretend we are a chicken sandwich or a cheeseburger or curried lentils and we are going to start the
journey through the digestive system and we’re going to see what happens along the way. We’re going to primarily keep track of three
macromolecules. We are going to keep track of sugars, or carbohydrates. We are going to keep track of proteins and we are going to
keep track of fats, or lipids along the way.

When food enters your mouth, digestion starts. You use your teeth to physically, or mechanically, break large pieces of food down into
smaller pieces of food. This is going to be important because along the way we are going to mix food particles with chemicals and with
these smaller particles the surface area for chemical digestion is increased. Additionally in your mouth, saliva will be used to break carbohydrates, or sugars, down into smaller structures known as disaccharides. A disaccharide is not the smallest form of a sugar, but it’s
a good start. After you chew food and mix it with saliva you form a small round ball known as a bolus. Swallowing will be the process
in which you move this bolus from your mouth down into your stomach through a long muscular pipe known as the esophagus.

Your stomach receives balls of food, or boli, and the primary function of the stomach will be to break down or to initiate the digestion of
proteins that were found in those food particles. From an anatomical standpoint your stomach is a three-dimensional mixing bowl. It’s
got several layers of muscle that are designed to allow your stomach to contract or shrink in a three-dimensional fashion. Additionally,
the walls of the stomach produce a fluid known as gastric juice. Gastric juice primarily will be designed to help you break down proteins.
In gastric juice we’re going to find general water, we’ll find hydrochloric acid, or stomach acid, and we’re going to find a very important
enzyme that will act as a chemical scissors to start breaking proteins down into their smaller pieces. In the stomach, pepsin will break
proteins into smaller chains known as peptides. That is the primary function of your stomach. If you eat foods that contain a lot of protein,
pepsin will have a greater job and hence food will stay in your stomach for longer periods of time. If you eat foods that contain primarily
water or sugar, materials that do not contain proteins, they will pass relatively quickly through your stomach down to the next organ
in the system. After protein digestion has started and has proceeded to a sufficient degree, material, at this point known as chyme, will
enter your small intestine through a ring of smooth muscle known as the pyloric sphincter.

The digestive system, along the way, will contain several little key regions. If we had to talk about a region that was of primary importance
we would have to focus on the small intestine. Anatomically the small intestine consists of a duodenum, which is attached to the
stomach and two other lengths of tube, essentially, known as the jejunum and the ileum, respectively. The small intestine will receive
bile from the liver and the gallbladder and it will also receive a chemical called pancreatic juice through special ducts from the pancreas.
The functions of the small intestine will be two-fold. First of all the small intestine will continue the digestion process. The process was
started in your mouth and continued nicely in your stomach but now we need to finish the deal. In your small intestines fats will be broken
down into smaller structures known as triglycerides. Peptides from the stomach will be broken down into smaller structures known
as amino acids and the remaining sugars, that have not yet been broken down in your mouth, will be turned into disaccharides or monosaccharides. Those are the particles that we are really after. In the small intestine final digestion will occur. What started out as a
cheeseburger will now be entirely different. You have spent a lot of time and energy producing useful particles, it’s an energetically costly
process and it’s very carefully maintained. Now we must move these particles from the small intestine into the bloodstream so we
can transport the products of sugar and fats, minerals and proteins, to every other tissue in your body. The small intestine, primarily the
duodenum and the jejunum; the first two regions, contain many small finger-like projections known as villi. These villi are going to serve
as avenues for the movement of material from your digestive system into the bloodstream, technically that’s absorption. Most of the
nutrients, most of the components of fats, sugars and proteins are absorbed in the duodenum and the jejunum. The ileum is going to
be connected to the final portion of your digestive system known as the large intestine or sometimes referred to as the colon. In the
ileum we are not going to find a lot of villi but we will see that water absorption occurs to a great degree.

After you have taken food into your body, chewed it up, sent it to your stomach for mixing and sent it to your small intestine for final
digestion and absorption what we will end up with, at this point in the ileum and in the first portion of the large intestine, will be a material
known as feces. This will be undigested matter. This will be unabsorbable matter, and from your body’s standpoint this is waste
material and you must get this out of your body in order to remain healthy. In order to remain at homeostasis. The ileum of the small
intestine is connected to the first portion of the large intestine known as the cecum, which is a small round ball shaped receiving chamber.
Additionally, attached to the cecum there is a small piece of lymphatic tissue known as the vermiform appendix or sometimes simply
the appendix. In humans the function of the appendix really is not known and there are many people that have their appendixes
removed and suffer no ill effects.

The large intestine consists of the cecum, the colon, the rectum and the anus, down at the distil end. What we are going to do now is
start at the cecum and trace the path of feces as it finishes out the process. Keep in mind we are talking about undigested, unabsorbable
material at this point. From the cecum, feces will move up the right side of the body through the ascending colon. The ascending colon
will turn to the left and run across your body, through the transverse colon, and then turn down on the left side to become the descending
colon. As soon as the descending colon travels down into an imaginary ring formed by the bones in your pelvis, the descending
colon will form an S-shaped curve sometimes known as the sigmoid colon. And last but not least, the sigmoid colon will deliver feces
to the rectum. The rectum will deliver, ultimately, feces out of your body through the anus. If we take a look at the walls of the ascending,
transverse, descending or sigmoid colon we will see that they are constructed a little bit differently than the walls of any other tissue
in your digestive system. They do consists of large, hollow cup-shaped pouches that will be crucial for allowing you to absorb waterfrom undigested, unabsorbed material. The large intestine does function very heavily in allowing you to get water from the foods and
beverages that you eat. Additionally in your large intestines we are going to find large amounts of bacteria, helpful bacteria by the way,
and these bacteria will handle several functions. For example, your intestinal bacteria will produce vitamin K, a very important component
in blood clotting. Your intestinal bacteria will also help you further metabolize proteins and sugars, functions that could not take
place in your small intestines.

As material travels through the ascending, transverse, descending and sigmoid colon it collects at the rectum. Special components of
your nervous system in the rectum can detect increased presence of feces or increased stretch in the walls. Information will be sent to
your brain and you will perceive that as the urge to use the restroom. From the rectum material will move out of your body through a
structure known as the anus. The anus actually consists of two rings of muscle, an internal anal sphincter and an external anal sphincter.
Because the external anal sphincter contains muscle that you can voluntarily control, you should consciously have control over the
movement of feces from the rectum into the external environment.

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