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Rabbit Alimentary System

2012-03-01T18:09:02Z

Jrodgers: Fixed minor typos

==Introduction==

The rabbit is a monogastric hindgut fermenter and is a herbivore. Microbes in the hindgut produce [[Volatile Fatty Acids|volatile fatty acids (VFAs)]] which are available to the animal for energy. Microbes also produce vitamins and protein, which are available only in minimal quantities as they are produced in the hindgut (see [[Hindgut Fermenters - Anatomy & Physiology|advantages and disadvantages of hid gut fermentation]]). Most microbial fermentation occurs in the [[Caecum - Anatomy & Physiology|caecum]] (as opposed to the [[Equine Alimentary System - Anatomy & Physiology|horse]] where most occurs in the colon). Rabbits usually eat at dusk.

==[[Monogastric Stomach - Anatomy & Physiology|Stomach]]==

The rabbit has a simple and large stomach.

==[[Small Intestine Overview - Anatomy & Physiology|Small Intestine]]==

A rabbit's small intestine functions similar to other animals, but there are anatomical differences. The caudal flexure of the [[Duodenum - Anatomy & Physiology|duodenum]] is long and coiled, and may be referred to as the transverse part of the duodenum.
The ''sacculus rotundus'' exists at the ileocaecal junction. It is an enlargement of the [[Large Intestine - Anatomy & Physiology|large intestine]] and contains [[Lymphatic System Overview - Anatomy & Physiology|lymphoid tissue]].

==Large intestine==

Click here for information on the [[Large Intestine Overview - Anatomy & Physiology|large Intestine]].

==[[Caecum - Anatomy & Physiology|Caecum]]==

A rabbit's caecum is large, about twice the length of the abdominal cavity and 10 times the capacity of the stomach, 40% of the entire alimentary tract. It is folded into four parts that flex upon each other. It is thin-walled. Visible on the external surface is a spiral constriction that runs 20-30 times around the caecum. This is related to the folding of the mucosa internally.
There is an [[Appendix - Anatomy & Physiology|appendix]] at its distal end containing [[Lymphatic System Overview - Anatomy & Physiology|lymphoid tissue]].

==[[Colon - Anatomy & Physiology|Colon]]==
A rabbit's colon has ascending, transverse and descending parts. The '''ascending colon''' is very long and occupies most of the ventral abdomen. The first part has taenia and haustra, the second part does not and is arranged into coils that lie in the dorsal part of the abdominal cavity. The '''transverse''' and '''descending''' colons have the same anatomical arrangement as in other species.

==Coprophagia==

Rabbits eat some of their faecal pellets, called '''caecotropes''', directly from the [[Anus - Anatomy & Physiology|anus]]. Caecotropes differ from normal pellets as they are softer, covered in mucus, smaller and contain large amounts of bacteria and microbes. The purpose of this may be to gain access to the vitamins produced by bacteria in the [[Caecum - Anatomy & Physiology|caecum]]. Some microbial protein may also be available, but is thought to contribute little to the animal's requirement, as most is digested in the colon. Therefore, some amino acids (lysine and methionine) are added to commercial rabbit food. This behaviour is also seen in rodents.

==Calcium Metabolism==

Rabbits have unique calcium metabolism. Calcium is absorbed across the intestinal wall in the absence of vitamin D, which other mammals require for calcium absorption. Less-regulated calcium absorption results in calcium being excreted in the urine. Parathyroid hormone and [[Calcium#Calcitonin|calcitonin]] regulate blood levels. Kidney stones and calcification of soft tissue may occur if a high calcium diet is fed to rabbits for a prolonged period of time.

{{Template:Learning
|flashcards = [[Rabbit Alimentary System - Flashcards|Rabbit alimentary system]]
}}

[[Category:Alimentary System - Anatomy & Physiology]]
[[Category:Rabbit Digestion]]
[[Category:Large Intestine - Anatomy & Physiology]]
[[Category:A&P Done]]

Dental Formula - Rabbit

2012-03-01T18:02:24Z

Jrodgers: Added citations in text

==Overview==
[[Image:Rabbit Teeth.jpg|thumb|right|250px|Teeth of a Rabbit - Copyright Nottingham 2008]]
The formula for permanent teeth is: 2 (I2/1 C0/0 P3/2 M2-3/3).

There is a small pair of incisors called "peg teeth" directly caudal to the primary maxillary incisors. Some rabbit herds may be missing these peg teeth, as a dominant trait.<ref name="LAM2p331">{{citation|initiallast =Suckow|initialfirst =M|2last =Brammer|2first =D|3last= Rush|3first =H|finalfirst =C|finallast=Chrisp|year = 2002|title = Biology and Diseases of Rabbits. ''In'' Laboratory Animal Medicine|ed = 2nd|city = San Diego|pub =Academic Press|range = 331}}</ref>

Rabbit teeth are hypsodont, meaning they continue to grow throughout life.<ref name="LAM2p331"></ref>

<references/>

[[Category:Teeth - Anatomy & Physiology]]
[[Category:Rabbit Dentition|A]]
[[Category:A&P Done]]

Dental Formula - Rabbit

2012-02-29T17:24:28Z

Jrodgers: /* Overview */

[[Image:Rabbit Teeth.jpg|thumb|right|250px|Teeth of a Rabbit - Copyright Nottingham 2008]]

==Overview==

The formula for permanent teeth is: 2 (I2/1 C0/0 P3/2 M2-3/3).

There is a small pair of incisors called "peg teeth" directly caudal to the primary maxillary incisors. Some rabbit herds may be missing these peg teeth, as a dominant trait.

Rabbit teeth are hypsodont, meaning they continue to grow throughout life.

{{citation|initiallast =Suckow|initialfirst =M|2last =Brammer|2first =D|3last= Rush|3first =H|finalfirst =C|finallast=Chrisp|year = 2002|title = Biology and Diseases of Rabbits. In Laboratory Animal Medicine|ed = 2nd|city = San Diego|pub =Academic Press|range = 331}}

[[Category:Teeth - Anatomy & Physiology]]
[[Category:Rabbit Dentition|A]]
[[Category:A&P Done]]

Mice (Laboratory) - Pathology

2012-02-27T07:44:56Z

Jrodgers:

{{review}}

[[Image:White_mouse.jpg|200px|thumb|right|''Albino Mice'' WikiCommons]]
==Anatomic features==
The laboratory mouse has several unique characteristics, and there are vast differences in normal anatomy, physiology, and behaviour among different strains of mice, many of which represent abnormalities arising from homozygosity of recessive or mutant traits in inbred mice.

The '''dental formula''' is 2(I 1/1, M 3/3) = 16. The incisors are open-rooted and grow continuously.

The '''stomach''' is divided into a proximal nonglandular portion and a distal glandular portion.

The left '''lung''' consists of one lobe, while the right lung consists of four lobes.

Mice have 3 pectoral and 2 inguinal pairs of '''mammary glands''', with mammary tissue enveloping much of the subcutis, including the neck. Mammary tissue can be found immediately adjacent to to salivary glands.

The mouse has the narrowest thermoneutral zone of any mammal thus far measured. A mouse responds to decreases in ambient temperature by nonshivering thermogenesis, and to increases in ambient temperature by decreasing metabolic rate and increasing vascularization of the ears. Nonshivering thermogenesis can produce a threefold increase in basal metabolic rate, and for the most part occurs in '''brown fat'''. The highest concentration of brown fat is found in the subcutaneous tissues between the scapulae.

The '''brain and spinal cord''' are larger in mature male mice compared to females.

The zona reticularis of the '''adrenal cortex''' is not discernible from the zona fasciculata. A unique feature of the mouse adrenal is the X zone of the cortex, which surrounds the medulla. The X zone is composed of basophilic cells but when males reach sexual maturity and females undergo their first pregnancy, the X zone disappears.

'''Melanosis''' occurs in several organs, including the anteroventral meninges of the olfactory bulbs, optic nerves, parathyroid glands, heart valves, and spleens of melanotic mouse strains, such as B6 mice.

==Strain Information==
Most laboratory mice have contributions from both Mus musculus musculus and Mus musculus domesticus. There is evidence that smaller contributions also may have come from Mus musculus molossinus and Mus musculus castaneus. Therefore, they should not be referred to by species name, but rather as laboratory mice or by use of a specific strain or stock name. (In addition, some recently developed laboratory mouse strains are derived wholly from other Mus species or other subspecies, such as M. spretus). The laboratory mouse genome, including its retroelements, is a mosaic and an artificial creation, and there is no true "wildtype" laboratory mouse.
There are over 450 inbred strains that have arisen during the last century but the great majority of biomedical resaerch, including genomic research, is based on a relatively few mouse strains, including C57BL/6, BALB/c, C3H/He, 129, FVB, and outbred Swiss stocks.

'''For more information on specific strains and the pathology associated with them, click [[Laboratory mice strain information|here]]

==Genetically Engineered Mice==
===Terminology===
Genetically engineered mice have induced mutations, including transgenes, targeted mutations (knockouts or knockins), and retroviral, proviral, or chemically-induced mutations.

Transgenic mice carry a segment of foreign DNA incorporated into their genome via non-homologous recombination (e.g., pronuclear microinjection), infection with a retroviral vector, or homologous insertion.

Targeted mutant mice are produced by first inducing gene disruptions, replacements, or duplications into embryonic stem (ES) cells via homologous recombination between the exogenous (targeting) DNA and the endogenous (target) gene. The genetically-modified ES cells are then microinjected into host embryos at the eight-cell blastocyst stage. These embryos are transferred to pseudopregnant host females, which then bear chimeric progeny. The chimeric progeny carrying the targeted mutation in their germ line are then bred to establish a line. If the newly established line has a disrupted or deleted gene, it is called a knockout; if it has a new or duplicated gene, it is called a knockin.

Mice with chemically-induced mutations are produced by using a variety of chemicals. One popular chemical mutagen, ethylnitrosourea (ENU), is used to induce point mutations. ENU mutagenesis involves exposing male mice to ENU and then mating the treated males to untreated females. The resultant progeny, many of which carry point mutations, are screened for phenotypes of interest.

===Applications===
Genetically engineered mice are useful for elucidating basic biological processes, studying relationships between gene mutations and disease phenotypes, and modeling human disease. Research applications are included on strain data sheets in the JAX® Mice Database. The applications are compiled using a number of information sources (please refer to Mouse Information Resources), but they are not all-inclusive: rapidly advancing biomedical research continually uncovers new applications and uses for genetically engineered and mutant mice strains.

Some genetically engineered and mutant mice strains have a mutation associated with a specific human disease. If the gene or mutation is orthologous to that in humans and causes the same disease in humans, the strain is designated as a model of the human disease. Manifestation of the genetic mutation (phenotypic expression) may differ between humans and mice. Investigators are strongly encouraged to research recommended mouse models to be sure they are appropriate for their research.

== References==
*{{citation|initiallast = Percy|initialfirst = D.H|2last = and Barthold|2first = S.W|finallast = |year = 2007|title = Pathology of laboratory rodents and rabbits|pub = Blackwell Publishing. pp. 3-123}}

*http://jaxmice.jax.org/type/gemm/index.html

[[Category:Laboratory Animal Pathology]]

Mice (Laboratory) - Pathology

2012-02-27T07:44:22Z

Jrodgers: Changed "white" to "albino" as these mice have non pigmented eyes.

{{review}}

[[Image:White_mouse.jpg|200px|thumb|right|''Albino Mice''' WikiCommons]]
==Anatomic features==
The laboratory mouse has several unique characteristics, and there are vast differences in normal anatomy, physiology, and behaviour among different strains of mice, many of which represent abnormalities arising from homozygosity of recessive or mutant traits in inbred mice.

The '''dental formula''' is 2(I 1/1, M 3/3) = 16. The incisors are open-rooted and grow continuously.

The '''stomach''' is divided into a proximal nonglandular portion and a distal glandular portion.

The left '''lung''' consists of one lobe, while the right lung consists of four lobes.

Mice have 3 pectoral and 2 inguinal pairs of '''mammary glands''', with mammary tissue enveloping much of the subcutis, including the neck. Mammary tissue can be found immediately adjacent to to salivary glands.

The mouse has the narrowest thermoneutral zone of any mammal thus far measured. A mouse responds to decreases in ambient temperature by nonshivering thermogenesis, and to increases in ambient temperature by decreasing metabolic rate and increasing vascularization of the ears. Nonshivering thermogenesis can produce a threefold increase in basal metabolic rate, and for the most part occurs in '''brown fat'''. The highest concentration of brown fat is found in the subcutaneous tissues between the scapulae.

The '''brain and spinal cord''' are larger in mature male mice compared to females.

The zona reticularis of the '''adrenal cortex''' is not discernible from the zona fasciculata. A unique feature of the mouse adrenal is the X zone of the cortex, which surrounds the medulla. The X zone is composed of basophilic cells but when males reach sexual maturity and females undergo their first pregnancy, the X zone disappears.

'''Melanosis''' occurs in several organs, including the anteroventral meninges of the olfactory bulbs, optic nerves, parathyroid glands, heart valves, and spleens of melanotic mouse strains, such as B6 mice.

==Strain Information==
Most laboratory mice have contributions from both Mus musculus musculus and Mus musculus domesticus. There is evidence that smaller contributions also may have come from Mus musculus molossinus and Mus musculus castaneus. Therefore, they should not be referred to by species name, but rather as laboratory mice or by use of a specific strain or stock name. (In addition, some recently developed laboratory mouse strains are derived wholly from other Mus species or other subspecies, such as M. spretus). The laboratory mouse genome, including its retroelements, is a mosaic and an artificial creation, and there is no true "wildtype" laboratory mouse.
There are over 450 inbred strains that have arisen during the last century but the great majority of biomedical resaerch, including genomic research, is based on a relatively few mouse strains, including C57BL/6, BALB/c, C3H/He, 129, FVB, and outbred Swiss stocks.

'''For more information on specific strains and the pathology associated with them, click [[Laboratory mice strain information|here]]

==Genetically Engineered Mice==
===Terminology===
Genetically engineered mice have induced mutations, including transgenes, targeted mutations (knockouts or knockins), and retroviral, proviral, or chemically-induced mutations.

Transgenic mice carry a segment of foreign DNA incorporated into their genome via non-homologous recombination (e.g., pronuclear microinjection), infection with a retroviral vector, or homologous insertion.

Targeted mutant mice are produced by first inducing gene disruptions, replacements, or duplications into embryonic stem (ES) cells via homologous recombination between the exogenous (targeting) DNA and the endogenous (target) gene. The genetically-modified ES cells are then microinjected into host embryos at the eight-cell blastocyst stage. These embryos are transferred to pseudopregnant host females, which then bear chimeric progeny. The chimeric progeny carrying the targeted mutation in their germ line are then bred to establish a line. If the newly established line has a disrupted or deleted gene, it is called a knockout; if it has a new or duplicated gene, it is called a knockin.

Mice with chemically-induced mutations are produced by using a variety of chemicals. One popular chemical mutagen, ethylnitrosourea (ENU), is used to induce point mutations. ENU mutagenesis involves exposing male mice to ENU and then mating the treated males to untreated females. The resultant progeny, many of which carry point mutations, are screened for phenotypes of interest.

===Applications===
Genetically engineered mice are useful for elucidating basic biological processes, studying relationships between gene mutations and disease phenotypes, and modeling human disease. Research applications are included on strain data sheets in the JAX® Mice Database. The applications are compiled using a number of information sources (please refer to Mouse Information Resources), but they are not all-inclusive: rapidly advancing biomedical research continually uncovers new applications and uses for genetically engineered and mutant mice strains.

Some genetically engineered and mutant mice strains have a mutation associated with a specific human disease. If the gene or mutation is orthologous to that in humans and causes the same disease in humans, the strain is designated as a model of the human disease. Manifestation of the genetic mutation (phenotypic expression) may differ between humans and mice. Investigators are strongly encouraged to research recommended mouse models to be sure they are appropriate for their research.

== References==
*{{citation|initiallast = Percy|initialfirst = D.H|2last = and Barthold|2first = S.W|finallast = |year = 2007|title = Pathology of laboratory rodents and rabbits|pub = Blackwell Publishing. pp. 3-123}}

*http://jaxmice.jax.org/type/gemm/index.html

[[Category:Laboratory Animal Pathology]]