Changes

==Overview==

==Overview==

===Carnivore===

===Carnivore===

The dog and cat posses two '''anal sacs'''. In the dog, these are the size of a hazlenut. They are located ventrolaterally between the internal and external anal sphincters. They are large, coiled apocrine tubules that have many '''tubuloalveolar glands''' in their walls. These '''tubuloalveolar glands''' produce a fatty secretion. The '''fundus''' of the sac secretes a potent smelling fluid that drains through a single duct to an opening near the '''anocutaneous juncntion'''.

The dog and cat posses two '''anal sacs'''. In the dog, these are the size of a hazlenut. They are located ventrolaterally between the internal and external anal sphincters. They are large, coiled apocrine tubules that have many '''tubuloalveolar glands''' in their walls. These '''tubuloalveolar glands''' produce a fatty secretion. The '''fundus''' of the sac secretes a potent smelling fluid that drains through a single duct to an opening near the '''anocutaneous junction'''.

 

The anal sacs get compressed during defecation, which causes the fluid to be expressed. The scent of the fluid is thought to act as a territorial marker.

The anal sacs get compressed during defecation, which causes the fluid to be expressed. The scent of the fluid is thought to act as a territorial marker.

Anal sacs are clinically important as they are commonly diseased in dogs - frequently, they become enlarged due to accumulated secretion. The '''dog''' has '''perianal glands''' that lie in the skin surrounding the anus. They are modified sebaceous glands.

 

Anal sacs are clinically important as they are commonly [[Anal Sac Disease - General|diseased]] in dogs - frequently, they become enlarged due to accumulated secretion. The '''dog''' has '''perianal glands''' that lie in the skin surrounding the anus. They are modified sebaceous glands.

===Equine===

===Equine===

Click here for information on the [[Equine Alimentary System  - Anatomy & Physiology|equine]] anus.

Click here for information on the [[Alimentary System  - Horse Anatomy|equine]] anus.

===Porcine===

===Porcine===

At the anus, the '''columnar intestinal epithelium''' is replaced by the '''stratified squamous keratinised epithelium''' of the skin. The '''anal canal''' joins the bowel to the exterior and is the last 2-3cm of the alimentary tract. This is a short passage derived from the '''proctodeum''' (formed by invagination of the surface ectoderm). Sebaceous and large apocrine sweat glands both occur in this region in association with the anal sphincters. Before joining the anal canal, the rectum becomes dilated to form the ''rectal ampulla''. At the '''rectoanal''' junction, the lumen is constricted by longitudinal folds in the mucosa, these are normally pressed together to occlude the lumen. As the muscosa changes from columnar to cutaneous, three zones are created:

At the anus, the '''columnar intestinal epithelium''' is replaced by the '''stratified squamous keratinised epithelium''' of the skin. The '''anal canal''' joins the bowel to the exterior and is the last 2-3cm of the alimentary tract. This is a short passage derived from the '''proctodeum''' (formed by invagination of the surface ectoderm). Sebaceous and large apocrine sweat glands both occur in this region in association with the anal sphincters. Before joining the anal canal, the rectum becomes dilated to form the ''rectal ampulla''. At the '''rectoanal''' junction, the lumen is constricted by longitudinal folds in the mucosa, these are normally pressed together to occlude the lumen. As the muscosa changes from columnar to cutaneous, three zones are created:

1.'''Columnar'''

'''1.Columnar'''

The columnar zone has many longitudinal folds. It can be divided from the rectum by the ''anorectal line''. This is a line where the mucosa is stratified squamous epithelium containing lots of lymphoid tissue.  

The columnar zone has many longitudinal folds. It can be divided from the rectum by the ''anorectal line''. This is a line where the mucosa is stratified squamous epithelium containing lots of lymphoid tissue.  

2.'''Intermediate'''

'''2.Intermediate'''

The intermediate zone can be divided from the cutaneous zone by the ''anocutaneous line''.

The intermediate zone can be divided from the cutaneous zone by the ''anocutaneous line''.

3.'''Cutaneous'''

'''3.Cutaneous'''

The cutaneous zone is the skin. It is stratified squamous keratinised epithelium that surrounds the anus. The excretory ducts of the '''anal sacs''' open into this region.

The cutaneous zone is the skin. It is stratified squamous keratinised epithelium that surrounds the anus. The excretory ducts of the '''anal sacs''' open into this region.

==Links==

==Links==

'''Click here for information on the[[Intestines, Small and Large - Pathology|pathology Of The Small and Large Intestines]].'''

'''Click here for information on the [[Intestines, Small and Large - Pathology|Pathology Of The Small and Large Intestines]].'''

[[Category:Large Intestine - Anatomy & Physiology]]

[[Category:Large Intestine - Anatomy & Physiology]]

[[Category:To Do - AimeeHicks]][[Category:To Do - AP Review]]

[[Category:A&P Done]]