Digestion 2
The Story Continues
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Fat Digestion
Fats are of course water insoluble and as a
result they are treated differently from the
digestion of carbohydrates and proteins.
Whereas most digestive products enter the
blood stream, fats enter the lymph system.
http://mek1980.wordpress.com/2008/06/
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Lymphatic System
The lymphatic system is a complex network of lymph nodes, lymph ducts,
lymph capillaries and lymph vessels that produce and transport lymph
from tissues to the circulatory system. Lymph is blood plasma.
http://lumologie.com.au/Page/TheLymphaticSystem
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Lymphatic System
Lymph leaks from the capillaries of the circulatory system, becoming interstitial
fluid, and filling the space between individual cells of tissue. The excess interstitial
fluid is collected by the lymphatic system into lymph capillaries.
http://lumologie.com.au/Page/TheLymphaticSystem
4
Lymph Nodes
Lymph nodes are small bean-shaped structures that are usually less than 2.5 cm in
length. They are widely distributed throughout the body along the lymphatic
pathways where they filter the lymph before it is returned to the blood. They tend
to concentrate in regions such as the groin, armpits and neck. Lymph nodes
contain high concentration of lymphocytes.
http://training.seer.cancer.gov/module_anatomy/unit8_2_lymph_compo.html
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Lymphatic System
Finally, unlike the blood system which has a heart, the lymphatic system has no
centralized pump. Instead movement is mediated by muscle contraction along the
lymph vessels and one-way valves.
http://lumologie.com.au/Page/TheLymphaticSystem
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Lymphatic System: lymphatic filariasis
(Elephantiasis)
Caused by Parasitic nematodes blocking the lymphatic
system and preventing drainage of lymph back to
the main circulatory system.
Transmitted by certain Mosquito species.
http://www.bio.davidson.edu/Courses/immunology/Students/spring2006/Heeren
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Lymphatic System
http://trc.ucdavis.edu/biosci10v/bis10v
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Lymph System: Drains into Subclavian Veins
http://www.iupucanatomy.com/chapter_23.htm
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Other Related Organs
Spleen: Destroys redundant red
blood cells and in some animals
it also stores blood (horses and dogs).
Also involved in filtering blood, in a sense
in acts as a large lymph node but is not
connected to the main lymph system.
http://trc.ucdavis.edu/biosci10v/bis10v
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Other Related Organs
Thymus: Maturing lymphocytes – T Cells.
Not used significantly in adults, mainly
an organ of childhood and in fact
diminishes in size with age.
Can be bought at good butchers, where
it is called sweatbread.
http://trc.ucdavis.edu/biosci10v/bis10v
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Other Related Organs
Tonsils: Lymphatic tissue that is used to
combat respiratory infections especially
in childhood.
http://trc.ucdavis.edu/biosci10v/bis10v
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Other Related Organs
Tonsils: Lymphatic tissue that is used to
combat respiratory infections especially
in childhood.
Often a troublesome organ due to it
sensitivity to infection.
Most infections (Tonsillitis) are probably
viral but sometimes opportunistic
bacteria such as streptococcus or even yeast
can cause further problems.
Tonsillitis can abscess if not looked after to form a quinsy which can be
removed by surgical incision and drainage of the pus.
http://en.wikipedia.org/wiki/Image:Tonsillitis.jpg
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Figure 21-19 - Overview
Summary of Lipid Digestion
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Lymph System:
Summary of Functions
1.Drains excess lymph back to blood system.
2.Filters out particles, bacteria and some proteins
3.Transports fatty acids and Cholesterol
http://www.iupucanatomy.com/chapter_23.htm
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Large Intestine
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Large Intestine
The large intestine is separated from
the small intestine by the
ileocecal value.
The large intestine comprises of two
sections:
a) Cecum (large pouch , storage?, varies in size according to animal)
b) Colon
c) Appendix? (Probably a vestigial structure , or storage for flora )
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Appendix
Probably a vestigial structure from a time when we
consumed more plant material.
Rabbit Digestive Tract
http://www.fao.org/docrep/x5082e/x5082E05.htm
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20
Large Intestine
1. About 1.5 m long
2. Smooth surface but has goblet
cells.
3. Absorbs water, electrolytes and
some vitamins
4. Some breakdown of food by
bacteria can be also be absorbed here (eg Vitamin K, Biotin).
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Last but not Least
Anus: Comprises of two values (or sphincters):
1. Inner: Smooth Muscle (involuntary)
2. Outer: Skeletal Muscle (voluntary)
Composition of Feces:
1/4: Dry Matter
1/5: Bacteria
The rest is water.
Odor is from H2S and
other sulfur compounds such
as mercaptans (organic S)
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Other Kinds of Digestion
Ruminant Digestion
23
Four Stomachs
http://www.dkimages.com/discover/DKIMAGES/Discover/Home/Animals/Mammals/Even-toed-HoofedMammals/Anatomy/Internal-Anatomy/Internal-Anatomy-1.html
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Four Stomachs
http://www.nicksnowden.net/Module_3_pages/The_Cow_as_a_Herbivore_and_mutualist.htm
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Four Stomachs
The Rumen contains a complex mixture of
bacteria and protozoa, these organism
digest cellulose into organic acids.
http://www.scienceimage.csiro.au/index.c
fm?event=site.image.detail&id=2181
http://www.admani.com/AllianceBeef/Technic
alEdge/Ruminant%20Feed%20Microbes.htm
Cows "chew the cud" i.e. they chew
food for long periods, swallow it,
regurgitate it and then chew it again.
http://www.nicksnowden.net/Module_3_pages/The_Cow_as_a_Herbivore_and_mutualist.htm
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Four Stomachs
cellulose -> glucose -> ethanoic acid + carbon dioxide + methane
http://www.nicksnowden.net/Module_3_pages/The_Cow_as_a_Herbivore_and_mutualist.htm
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