Transcript Milk Production by Country 1995

The Mammary Gland
 The
milk secreting organ
 Modified sweat gland
 Exocrine gland
MAMMARY GLANDS
thoracic
inguinal
abdominal
MAMMARY GLANDS
• 4 abdominal; 15 openings / teat
MAMMARY GLANDS
• 2 thoracic, 6 abdominal, ; 3-7 openings / teat
MAMMARY GLANDS
• 2 thor., 6 abdom. 2 ing., ; 8-10 openings/ teat
MAMMARY GLANDS
• 4 thor., 2 abdom. 4 ing., ; 1 opening/ teat
MAMMARY GLANDS
• 2 inguinal ; 1 opening/ teat
MAMMARY GLANDS
• 2 inguinal ; 2 openings/ teat
MAMMARY GLANDS
• 4 thor., 6 abdom. 2 ing., ; 2 openings/ teat
MAMMARY GLANDS
• 4 inguinal ; 1 opening/ teat
Anatomy of the Mammary
Gland


Mammary gland - milk secreting structure
including teats, duct system, lobes,
lobules, and secretory tissue
 Modified sweat gland
 Exocrine gland
Cow
 Large & in inguinal region
 4 teats/quarters = 4 separate glands
 No mixing of ducts across quarters
Anatomy of the Mammary
Gland
 Rear
quartes produce approx. 60% of
the milk and the fore quarters
produce the remaining 40%
 The size and shape of udders vary
with the 1) producing ability, 2) age,
and 3) genetic of the cow
Anatomy of the Mammary
Gland
 Cow
Front
& rear quarters separated
by fine membrane
Left and right separated by
median suspensory ligament
Supernumerary teats (some with
duct and secretory system)
How much support is enough?
High producing Holstein cow
 Empty Udder = 25 kg.
 Milk = 30 kg
 25 + 30 = 55 kg !!!

Udder Support in
Cow
Skin
 Fine connective tissue below skin
 Connective tissue attaches front
quarters to abdominal wall
 Lateral suspensory ligaments (LSL)
 Median suspensory ligament (MSL)
 The subpelvic tendon

Udder Support
in Cow
 LSL
Sling
around udder
2 layers
Inelastic, more fibrous than MSL
Lateral Suspensory Ligaments
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
Udder
Support in
Cow
 MSL
Primary
support
Relatively elastic
2 layers
Broken MSL – pendulous udder
Median Suspensory Ligament





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
 Glands
on each half
are divided by sheets
of tissue
© Biology of Lactation, Schmidt
Udder Support
in Cow
 Lamella
septa
Connective
tissue
Runs between LSL & MSL
Divides parenchyma into lobes and
lobules
Duct System



Teat meatus, the small
canal located in the end
of each teat is .5 to 1 cm
long and is the only
sphincter in each gland
Seven or eight loose
folds of membrane
known as furstenburg
rosette are located above
the teat meatus
The teat cistern, the
cavity within the teat
hold 30 to 90 ml of milk.
The Secretory Tissue




A Lobe: group of lobules
A Lobule: group of alveoli
Alveoli: cluster of alveolus
Alveolus: a single layer of
epithelial cells surrounding a
central lumen
Blood Supply to Mammary
Gland
400 kg blood to produce 1 kg of milk
 2 major arteries
Front ½ of udder
Rear ½ of udder
 4 major veins
2 follow same path as arteries
2 mammary veins

Nervous System

Sensory (afferent)
nerves in skin and
teats
 Positive
stimulation
of teats and
surrounding area
initiates milk letdown reflex via
oxytocin
© Biology of Lactation, Schmidt
Nervous System

Sympathetic (efferent) (involuntary) nerves
associated with arteries in the gland
 Control blood flow to the gland
 Innervation of sphincters muscles
in teats
 Stress causes vasoconstriction decreasing milk
secretion and let-down
 No parasympathetic innervation

No nerves to myoepithelial cells or alveolar
cells
Lymph System of Mammary
Gland
What is lymph & what does it do?
 Supramammary lymph nodes
 Lymph vessels
 Factors that influence edema
Age
Diet (especially NaCl)
Exercise
Genetics

Mammary Gland Development

Five phases of mammary development
Prenatal (teats & cisterns dev.)
Prepubertal (limited growth)
Postpubertal
Pregnancy (most growth)
Early lactation
Mammary Gland Development
Major development occurs at puberty
and during gestation
 Hormones
Estrogen (growth of duct system)
Progesterone (development of
alveolar tissue in combination with
other hormones)
GH (growth of duct system)
Prolactin (initiation and continuity
of lactation)

Mammary Gland Development
Mammary Gland Development
Anatomy of the Mammary
Gland
 Goats
and sheep
2 teats/ 2 halves (glands)
 Pig
12-14 teats – 2 glands and duct
systems per teat
 Mare
4 quarters/duct systems but 2
teats
Mammary
Duct
System
Epithelial Cell
Lumen of alveolus
Fat
Droplet
Fat Droplet
migrating
Golgi Body
Lysosome
Nucleus
Mitochondria
Mitochondria
E.R
.
Blood Vessel