Other systems in the mammary gland support nervous circulatory and lymphatic
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Other Systems in the Mammary Gland: Support, Nervous, Circulatory, and Lymphatic. Melissa Hlavacek. Support Systems. Variation across species. Litter-bearing Species. No large suspensory ligaments Fibrous connective tissue and skin are the primary support

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Other systems in the mammary gland support nervous circulatory and lymphatic
Other Systems in the Mammary Gland: Support, Nervous, Circulatory, and Lymphatic

Melissa Hlavacek


Support systems
Support Systems Circulatory, and Lymphatic

  • Variation across species


Litter bearing species
Litter-bearing Species Circulatory, and Lymphatic

  • No large suspensory ligaments

  • Fibrous connective tissue and skin are the primary support

  • Examples: pigs, dogs, cats, rodents


Humans and litter bearing species
Humans and Litter-Bearing Species Circulatory, and Lymphatic

  • Gland is on top of muscle tissue

  • Strong, fibrous connective tissue separates it from the muscle

  • Suspensory ligaments are either attached to the muscle or the connective tissue

  • In litter bearing species, each half is also separated from the other

    • Midline

  • Skin also provides protection and a little support


The cow
The Cow Circulatory, and Lymphatic

  • Many different tissues…

    * Median suspensory ligament * Skin

    * Lateral suspensory ligament - Superficial fascia

    - Fine connective tissue - Subpelvic tendon

    - Coarse connective tissue

© The Babcock Institute


Connective tissue skin
Connective Tissue & Skin Circulatory, and Lymphatic

  • Fine connective tissue

    • Attaches skin to underlying tissue

  • Coarse connective tissue

    • Attaches front quarters to abdominal wall

  • Skin

    • Little support

    • Protection from pathogens

  • Front and rear are also separated by connective tissue

    • No internal crossover between any of the quarters


Median suspensory ligament
Median Suspensory Ligament Circulatory, and Lymphatic

  • Primary support of the udder

  • Two adjacent heavy sheets of tissue

  • Mostly elastic, some fibrous tissue

  • Attaches to the abdominal wall

  • Divides the udder into halves (left and right)

    • Glands on each half are divided by sheets of tissue

© Biology of Lactation, Schmidt


Lateral suspensory ligaments
Lateral Suspensory Ligaments Circulatory, and Lymphatic

  • Like a “hammock” around the udder

    • From the pelvis to the median suspensory ligament

  • Mostly fibrous tissue

    • Collagen

  • Attaches to the alveolar tissue

    • Provides internal framework

  • Does not connect at the base of the udder


How much support is enough
How much support is enough? Circulatory, and Lymphatic

  • High producing Holstein cow

  • Empty Udder = 50 lb.

  • Milk = 60 lb.

  • 50 + 60 = 110 lb. !!!


Importance
Importance Circulatory, and Lymphatic

  • Udder support can significantly affect milking ability and useful life

    • 10 – 25% heritable

  • Pendulous udders are more likely to suffer injury

    • Especially teats

    • Increased mastitis

    • Affect on offspring


Nervous system
Nervous System Circulatory, and Lymphatic

  • Few nerves go into the gland

  • Like other skin glands…no parasympathetic innervation


Sensory nerves
Sensory Nerves Circulatory, and Lymphatic

  • Skin and teats

  • Positive stimulation of teats and surrounding area initiates milk let-down reflex via oxytocin

    • Critical!

© Biology of Lactation, Schmidt


Sympathetic nerves
Sympathetic Nerves Circulatory, and Lymphatic

  • Associated with arteries in the gland

    • Control blood flow to the gland

    • Carry oxytocin to the gland

    • Innervation of sphincters muscles in teats

    • Stress causes vasoconstriction decreasing milk secretion and let-down

  • There are no nerves to myoepithelial cells or alveolar cells

    • Contraction is regulated by oxytocin


Nervous system1
Nervous System Circulatory, and Lymphatic

  • In species such as pigs, nerve supply to the abdominal mammary glands is different than inguinal mammary glands.


Circulatory system
Circulatory System Circulatory, and Lymphatic

  • All milk precursors come from the blood

  • No crossover between each side of the mammary gland

  • Venous circle

    • Prevents pinching off of areas of venous outflow when animal is lying down


Circulation
Circulation Circulatory, and Lymphatic

  • Elongation and proliferation of growing vessels

    • Angiogenesis

    • Vasculogenesis

  • Complex interactions between

    • Endothelial cells

    • Extracellular matrix

    • Specific stromal cells

  • Requires dramatic reorganization of surrounding tissue


    • Growth factors affect rates of endothelial cell proliferation and degree of vessel formation

      • VEGF-vascular endothelial growth factor

        • Major regulator

        • Maintains viability

        • Stimulates mitogenesis and chemotaxis

        • Changes permeability

    • Many growth factors in different isoforms

    • Enzymes alter surrounding tissue


    Sphincters
    Sphincters proliferation and degree of vessel formation

    • Capillary beds

      • alveolus ‘hairnet’

    • Sphincters constricted

      • no blood flow

    • Sphincters open

      • blood flow to alveolus


    • Local proliferation and degree of vessel formationcontrol of blood flow

      • High pO2 = high blood flow

      • Need ATP

      • ATP needs oxygen

      • High pO2= high ATP

      • = sphincters constricted

    Terminal arteriole

    Metarteriole

    Large vein

    sphincters

    Post capillary venule


    Other local controllers of blood flow
    Other local controllers of blood flow proliferation and degree of vessel formation

    * Oxygen

    * Carbon Dioxide

    • Adenosine

    • Lactic Acid

    • pH

    • Hormones

    • Nitric Oxide

      • Alveolar cells each control their own blood and nutrient supply


    So how much blood is enough
    So how much blood is enough? proliferation and degree of vessel formation

    500 Liters blood = 1 Liter milk

    1 truck of blood = 100 lbs. milk


    Hot area of research mammary tumors
    Hot area of proliferation and degree of vessel formationresearch: mammary tumors

    Depends on angiogenesis for survival

    Killer of females and males


    Estrogen
    Estrogen proliferation and degree of vessel formation

    • Mediates synthesis/secretion of local tissue growth factors

      • Direct effect?

    • Changes in angiogenesis of ovary, placenta, endometrium

    • Mammary gland is a reproductive organ

    • Other hormones?


    Tumors
    Tumors proliferation and degree of vessel formation

    • What’s u-PA?

      • Activator of the zymogen plasminogen

      • Plasmin degrades extracellular proteins

      • Increases angiogenesis and mammary development

    • High concentrations of u-PA in breast cancer patients


    Thermogenesis proliferation and degree of vessel formation

    Hot spot

    Infra-red thermography


    Lymphatic system
    Lymphatic System proliferation and degree of vessel formation

    • Molecules go out of the capillaries but not all can get back in

      • Disrupt the normal osmotic pressure

    • Functions

      • Pick up extracellular fluids and bring back to the circulatory system

      • Transport of leukocytes

      • Transport of immune cells


    Lymphatic system1
    Lymphatic System proliferation and degree of vessel formation

    • 2 Supramammary Lymph Nodes

      • Each above ½ the udder

      • Filter tissue fluids

      • Remove foreign material

      • Vaccination?


    1.6 L LYMPH proliferation and degree of vessel formation= 1 LbMILK


    Udder edema
    Udder Edema proliferation and degree of vessel formation

    • Parturition

    • Accumulation of secretions

      • Pressure

      • Passive flow is hindered

    • Tight junctions do not function well

      • Fluid enters interstitial space

      • Alters osmolarity

      • Alters hydrostatic pressure

      • Less fluid is removed

    • Connective tissue spaces swell

    • Causes???


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