Download The Large Intestine

The Large Intestine
By: Nisha Kumar
Jia Mohnani
Structure
Connected to small intestine at a T-shaped
junction
Muscular called a sphincter controls the
movement of material
One part of the T is a pouch called a cecum,
and in humans, it has finger like extensions
called an appendix, which is dispensable
About 1.5 meters long
Simple columnar epithelium
Abundance of goblet cells
Micro
1. Colon
The mucosa of the colon is lined by a simple
columnar epithelium with a thin border and
numerous goblet cells.
3 layers of mucosa membrane:
a.muscular mucosae (longitudinal layer)
b.submucosa ( irregular connective and
adipose tissue)
c.muscularexterna (smooth muscle)
micro
2. Appendix
1. The muscularisexterna resembles that of
the small intestine, because it has an
inner smooth muscle layer and a complete
outer smooth muscle layer.
2. Lymphoid nodules frequently accumulate
in the submucosa.
Micro
3. Recto-anal
Junction
A narrow zone of transition from the simple
columnar epithelium of the intestine to the
keratinized is stratified squamous epithelium.
Within the transition zone, you may find
stratified columnar epithelium and
nonkeratinized stratified squamous epithelium.
macro. structure
Parts of the large intestine are:
Cecum– the first part of the large intestine
Taeniae coli– three bands of smooth muscle
Haustra – bulges caused by contraction of taeniae coli.
Epiploic appendages- small fat accumulations on the
viscera
The wall of the large intestine is lined with simple
columnar epithelium.
The mucosa of the large intestine does not have folds.
macro- Structure vs Function
The appendix is attached to its inferior surface of the cecum. It
contains the least of lymphoid tissue. It is a part of mucosa
associated lymphoid tissue which gives the appendix an important
role in immunity.
On the surface we have bands of longitudinal muscle fibers called
taeniae coli.
There are three bands, and they start at the base of the appendix
and extend from the cecum to the rectum. Along the sides of the
taeniae, we have fat, called epiploic appendages (or appendices
epiploicae).
The sacculations, called haustra, are characteristic features of the
large intestine, and distinguish it from the small intestine.
Functions
Major function is to recover water that entered
the alimentary canal as the solvent of various
digestive juices-with small intestine recover
90% of water lost (7 L in total loss)
Feces becomes more sold and moved along in
colon via peristalsis
Large colon allows for digested food to move
along slowly and allow for vitamins and water to
be reabsorbed into the bloodstream
Structure vs. Function
Herbivores have longer colons/large intestines
since they have to process fibrous, protein-poor
eucalyptus leaves
An herbivore's cecum is usually longer so that it
can function as a fermentation chamber where
symbiotic bacteria convert the shredded leaves
into a more nutritious diet
Secretions
Secretes bio carbonate and potassium- why
severe diarrhea can cause metabolic acidosis
and hypokalemia
Symbiotic bacteria producing vitamins as
biproducts ex) oesophagus and gullet
What can happen?
Diarrhea is caused when bacteria or a virus
irritates the colon, causing less water to be
reabsorbed by the colon
Constipation is when peristalsis moves feces
along the colon too slowly, causing too much
water to be reabsorbed
Metabolic acidosis- too much acid produced or
when kidneys don't remove enough acid from
body
Hypokalemia- levels of potassium are too low
What's Living there?
Lots of harmless bacteria, including Escherichia
coli (E. coli)
What does it mean?
If E. coli is found in lakes and streams it means
it has been contaminated by untreated sewage
A by-product of these bacteria generate gases,
including methane and hydrogen sulfide
Some also produce vitamins including biotin,
folic acid, vitamin K, and several B vitamins
food absorbed at the date..
The large intestine has over 700 species of bacteria that
perform a variety of functions. The large intestine absorbs
some of the products formed by the bacteria inhabiting this
region.(mostly water). Undigested polysaccharides (fiber)
are metabolized to short-chain fatty acids by the bacteria in
the large intestine and absorbed by passive diffusion. (all
the nutrients are left from the small intestine are absorbed
by the large intestine) Everything else that wasnt absorbed
by Keavers and Hector turns into feces.
Work cited
BBC News. BBC. Web. 10 May 2012. <http://www.bbc.co.uk/health/treatments/healthy_living/nutrition/healthy_digestive.shtml>.
"Large Intestine." Large Intestine. Web. 10 May 2012. <http://home.comcast.net/~wnor/largeintestine.htm>.
"National Digestive Diseases Information Clearinghouse (NDDIC)." - National Digestive Diseases Information ClearinghouseYour
Digestive System and How It Works. Web. 10 May 2012. <http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/>.
"Where Is Food Digested?" Where Is Food Digested? Web. 10 May 2012. <http://www.edinformatics.
com/math_science/where_is_food_digested.htm>.