Changes

== Blood Supply ==

== Blood Supply ==

 

* In species with '''inguinal mammary glands''' (cow,ewe,goat,mare), the main blood supply is from the '''external pudendal artery'''.  This arises indirectly from the external iliac artery via the femoral artery. The external pudendal artery passes through the inguinal canal.

* In species with '''inguinal mammary glands''' (cow,ewe,goat,mare), the main blood supply is from the '''external pudendal artery'''.  This arises indirectly from the external iliac artery via the femoral artery. The external pudendal artery passes through the inguinal canal.

** Due to the extensive blood supply in the cow, there is also a small contribution from the '''internal pudendal artery''' which is a branch of the internal iliac atery.  Also, the external pudendal artery has a sigmoid flexure to permit the artery to stretch when the udder is full of milk.

** Due to the extensive blood supply in the cow, there is also a small contribution from the '''internal pudendal artery''' which is a branch of the internal iliac atery.  Also, the external pudendal artery has a sigmoid flexure to permit the artery to stretch when the udder is full of milk.

* In species which also have '''thoracic mammary glands''' (bitch,queen,sow) blood supply is from the '''internal thoracic artery''' and its branches - cranial and cranial superficial epigastric arteries.

* In species which also have '''thoracic mammary glands''' (bitch,queen,sow) blood supply is from the '''internal thoracic artery''' and its branches - cranial and cranial superficial epigastric arteries.

* Venous drainage is through '''sattelite veins''', except in ruminants.

* Venous drainage is through '''sattelite veins''', except in ruminants.

* During lactation in ruminants, the external inguinal vein cannot drain the extensive amount of blood present.  Thus, the '''cranial and caudal superficial epigastric veins''' anastamose to form the '''milk vein'''. Also, right and left mammary veins anasamose to form a ring around the base of the udder.  Valves become non-functional to accommodate the increased venous return and allow blood to flow in either direction.  This is important, for example if a cow were to lie down, the weight on one side would collapse the thin-walled veins on that side so anastamoses ensure continued venous return.

* During lactation in ruminants, the external inguinal vein cannot drain the extensive amount of blood present.  Thus, the '''cranial and caudal superficial epigastric veins''' anastamose to form the '''milk vein'''.

** Valves become non-functional to accommodate the increased venous return and allow blood to flow in either direction.  This is important, for example if a cow were to lie down, the weight on one side would collapse the thin-walled veins on that side so anastamoses ensure continued venous return.

 

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