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?