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Frequency vs. Interval
• Milking Frequency
– 2 times/day (2X) or 3 times/day (3X)
• Milking Interval
– 12 hours, 8 hours, etc.
• How often do cows want to be milked?
Frequency vs. Interval
What are the advantages and disadvantages
of more frequent milkings?
Chemotactic
agents: attract
PMN into
tissues & milk!
• Alveoli
• Basic milk-producing unit
• Lined with epithelial cells
• Phagocyte
• Cell that engulfs and absorbs
bacteria
• PMN
• Polymorphonuclear neutrophil
• First line of defense against
invading pathogens during
mastitis
• Majority cell type accounting
for SCC
• Macrophages, lymphocytes
• Chemotaxis
• Movement of an organism in response to a chemical
stimulus
• Somatic cells and bacteria move according to chemicals
in their environment
• Where and why would they be moving?
• What is a common example of chemotaxis unrelated
to milk secretion?
Altered Composition
During Mastitis
Somatic cell counts (SCC)
Na, Cl, whey protein (e.g., serum
albumin, Ig)
lactose, casein, K, α-lactalbumin
Altered Composition During Mastitis
• Lactose
• Synthesis is decreased
• Casein
• Proteolysis
• Proteolytic enzymes from leukocytes and bacteria
• Milk fat
• Susceptibility of milk fat globule membranes to the
action of lipases, resulting in breakdown of
triglycerides.
• Na+, Cl-, K+
• Electrical potential across apical membrane disrupted
• This is the basis of the electrical conductivity methods of
detecting mastitis
• https://www.youtube.com/watch?v=P-imDC1txWw
• Polymorphonuclear neutrophils (PMNs)
• Mastitis causes chemotaxis of the cells into the tissue and
disruption of epithelial tight junctions
• This is the basis of many mastitis detection methods
• Albumin, immunoglobulins
• Enter the milk via disrupted tight junctional complexes
Altered Composition During Mastitis
PHYLOGENY & ONTOGENY
Phylogeny –
the evolutionary development of
any animal species (related to
mammary gland development)
Class Mammalia: Monotremes
I. Subclass Prototheria - “1st beasts”, egg layers
A. Order Monotremata - Monotremes, egg-
laying mammals,
most primitive MG
Examples:
1. Duckbill platypus
2. Porcupine anteater or echidna
Gland Tubes
• No nipples
• No internal milk storage
• Milk secreted onto hairs and lapped up by
young
• https://www.youtube.com/watch?v=NG
uIezLFidY (18:00)
When does a monotreme
initiate lactation?
• In cows and humans:
• Placenta detaches
• ↓ estrogen and progesterone
• ↑ prolactin
• Lactation begins
• If no placenta is present and eggs are laid,
how would the body know to produce milk 10
days after the eggs are laid (when they
hatch)?
Class Mammalia: Metatheria
II. Subclass Theria - “beasts,” born alive
A. Infraclass Metatheria - “succeeding
beasts”, no true placenta, increased
complexity of MG
Examples: Marsupials - pouched,
opossum, kangaroo
Kangaroo
• Joeys can be as small as a grain of rice, or as big as a bee, at 0.2 to 0.9
inches (5 to 25 millimeters) at birth
• Joeys live in the pouch for another 120 to 450 days
• Joeys urinate and defecate in the mother's pouch
– Pouch lining absorbs some of the mess, but occasionally the
mother will need to clean it out, which she does by inserting
her long snout into the pouch and using her tongue to remove
the contents
• Able to suckle two joeys at different developmental stages at the same
time with milk that has different nutritional content!!
• Joeys are fully mature at 14 to 20 months for females or 2 to 4 years
for males
Kangaroo
Kangaroo
Kangaroo
Kangaroo
Kangaroo
Kangaroo
Kangaroo
Marsupial Videos
Opossum Babies in Pouch:
https://www.youtube.com/watch?v=HQI0HRToyiI
Kangaroo Birth:
https://www.youtube.com/watch?v=UpsnREY-6no
Joey in Pouch:
https://www.youtube.com/watch?v=qT-Za3wolVo
Class Mammalia: Eutheria
II. Subclass Theria - “beasts,” born alive
B. Infraclass Eutheria -”true beasts”,
animals with placentas, highly
developed MG
4,000 species
Humans, cows, dogs, cats, bats, rats, whales,
elephants, shrews, armadillos, etc.
Ontogeny-
the life history or biological
development of an individual
organism (or organ).
The relationship of mammary gland
to other skin glands.
PHYLOGENY & ONTOGENY
Gland and Secretion Types
Exocrine Endocrine
Secreted by ducts Not secreted by ducts
Secretion poured directly at site Pour secretions into the blood
Secrete enzymes Secrete hormones
Control short term activity Control long term of target
organs
Examples: Gastric gland,
salivary gland, sweat glands
Examples: Pituitary gland,
thyroid gland, adrenal gland
Merocrine Secretion
• Secretions excreted via exocytosis from secretory cells into an
epithelial-walled duct, then onto a bodily surface or into the lumen
• Most common manner of secretion
• The gland releases its product and no part of the gland is lost or
damaged (compare holocrine and apocrine)
Holocrine Secretion
• Secretion produced in the cytoplasm of the cell and released by
the rupture of the plasma membrane
• Destroys the cell and results in the secretion of the product
into the lumen
• Most damaging type of secretion
Apocrine Secretion
• Secretion buds off through the plasma membrane producing
membrane-bound vesicles in the lumen
• Apical portion (top) of the secretory cell pinches off and enters
the lumen
• Part of apical cytoplasm is lost with the secreted products
• Simple branched acinar gland
• Gland has multiple cell layers
• Most numerous adjacent to hair sheath and duct opens to hair follicle
• Secrete sebum (mostly lipid, but also contains cellular debris)
• Whole cell and contents are released – what type of secretion is this?
• Secretion discharged as sebum through the sebaceous duct connecting
the gland to the hair follicle
• Other sebaceous glands open to skin surface are not associated with
hair
• E.g. lips and eyelids
Sebaceous Glands
Sebaceous Glands
• Sebaceous glands begin to form from embryonic hair follicles
gestation and are well-developed at birth
• Acne occurs when the outlet from the gland to the surface of
the skin is plugged
• Sebum accumulates in the follicle and sebaceous duct
• Chemical breakdown of triglycerides in the sebum, possibly
by bacterial action, releases free fatty acids
• Triggers an inflammatory reaction, producing pimples
Sebaceous Glands
Overactive Sebaceous Glands
Cradle Cap Acne
Eccrine Gland
• Type of sweat gland
• Simple, unbranched tubular gland
• Terminates in coil in subcutaneous tissue (corium)
• Ductal portion is 2-3 layers of cells
• Secretory portion is 1 layer of cells
• Secretion released (diffuses) through cell membrane
• Little change to cell
• Merocrine secretion
• Secretion contains Na, K, Cl, urea, lactate
Eccrine Gland
How Sweating Occurs
How Sweating Occurs
Apocrine Gland
• Type of sweat gland
• Large tubular gland associated with hair follicles
• Located around nipples, groin, anus, pubic region,
underarms, and eyelids
• Continuously secrete a fatty sweat into the gland tubule
• Secretion composed of: protein, carbohydrate, ammonia,
lipids, ferric iron, fatty acids
• Stress causes the tubule wall to contract, expelling the
fatty secretion to the skin, where local bacteria break it
down into odorous fatty acids
What Causes BO?
What Causes BO?
What Causes BO?
What type of secretion
is milk?
What type of gland is
the mammary gland?
What type of secretion
is milk?APOCRINE / EXOCRINE
What type of gland is
the mammary gland?APOCRINE / EXOCRINE
Questions?