Milk Production by Country 1995
Download
Report
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