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Mammary Gland - Anatomy & Physiology (view source)
Revision as of 13:05, 7 July 2008
, 13:05, 7 July 2008no edit summary
* Mammary buds grow into overlying mesenchyme and '''primary epidermal sprouts''' grow out of the bud apex. The epidermal sprout branches extensively and develops a complete '''duct system'''.
* Mammary buds grow into overlying mesenchyme and '''primary epidermal sprouts''' grow out of the bud apex. The epidermal sprout branches extensively and develops a complete '''duct system'''.
* Mammary adipose tissue is derived from mesoderm. This is required for complete mammary development and is thus absent in the male. As a result, mammary development in the male is halted at the epidermal sprout stage.
* Mammary adipose tissue is derived from mesoderm. This is required for complete mammary development and is thus absent in the male. As a result, mammary development in the male is halted at the epidermal sprout stage.
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== Structure ==
== Structure ==
* '''Medial Lamina''': elastic fibres from the tunica flava ventral to the pubic symphysis. Separates the udder into right and left halves.
* '''Medial Lamina''': elastic fibres from the tunica flava ventral to the pubic symphysis. Separates the udder into right and left halves.
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* 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'''. 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.
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== Innervation ==
* '''Sympathetic''': Innervation to the blood vessels and teat sphincter smooth muscle via the '''genitofemoral nerve'''.
* '''Sympathetic''': Innervation to the blood vessels and teat sphincter smooth muscle via the '''genitofemoral nerve'''.
* '''Somatic''': Ventral rami of spinal nerves. In the cow, spinal nerves L1-L4 and the pudendal nerve innervate the udder.
* '''Somatic''': Ventral rami of spinal nerves. In the cow, spinal nerves L1-L4 and the pudendal nerve innervate the udder.
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== Lymphatics ==
== Lymphatics ==
* '''Thoracic mammary glands''': axillary lymph node
* '''Thoracic mammary glands''': axillary lymph node
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== Histology ==
* Secretory tissue is arranged into '''lobes''',each consisting of many '''lobules'''. Each lobule contains groups of '''alveoli''' (secretory compound tubuloalveolar cells) surrounded by a network of blood vessels and connective tissue stroma. The alveolar lumen is filled with milk during lactation.
* '''Myoepithelial cells''' lie between alveolar epithelial cells and the basement membrane. These contract under the influence of oxytocin to release milk to the exterior.
* Lobes and lobules are drained by lactiferous ducts into the '''gland sinus''', which is continuous with the '''teat sinus'''. Epithelium lining lactiferous ducts and the sinus is two-layered cuboidal.
* A '''teat canal''' connects the teat sinus to the exterior. The lining is stratified squamous epithelium. Circular smooth muscle in the wall of the canal forms a '''sphincter'''. Between milkings, the narrow lumen of the teat canal is filled with a soft keratin plug to prevent bacteria entering the teat sinus and prevent milk leakage.
[[Image:Active Mammary Gland.jpg|left|thumb|250px|<small><center> The Active Mammary Gland. Copyright RVC 2008 (Courtesy of Tanya Hopcroft (RVC))</center></small>]]
[[Image:Active Mammary Gland high power.jpg|left|thumb|250px|<small><center> The Active Mammary Gland at High Power. Copyright RVC 2008 (Courtesy of Tanya Hopcroft (RVC))</center></small>]]
[[Image:Mammary Gland myoepithelial cells.jpg|right|thumb|250px|<small><center> Mammary Myoepithelial Cells. Copyright RVC 2008 (Courtesy of Tanya Hopcroft (RVC))</center></small>]]
[[Image:Mammary Gland lactiferous duct.jpg|right|thumb|250px|<small><center> Section of the Mammary Gland showing a Lactiferous Duct. Copyright RVC 2008 (Courtesy of Tanya Hopcroft (RVC))</center></small>]]
[[Image:Mammary Gland teat canal keratin plug.jpg|right|thumb|250px|<small><center> Cross Section through the Teat Canal of the Mammary Gland showing a Keratin Plug. Copyright RVC 2008 (Courtesy of Tanya Hopcroft (RVC))</center></small>]]
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