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Home , Apocrine, Duct (anatomy), Gland, Holocrine, Mammary gland, Merocrine

Frequency vs. Interval

• 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 & ! • Alveoli • Basic milk-producing unit • Lined with epithelial cells • Phagocyte • that engulfs and absorbs • 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 ? Altered Composition During Mastitis

Somatic cell counts (SCC)

Na, Cl, whey (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 • Susceptibility of milk fat globule membranes to the action of lipases, resulting in breakdown of triglycerides. Altered Composition During Mastitis

• 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 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 PHYLOGENY & ONTOGENY

Phylogeny – the evolutionary development of any animal species (related to mammary development) Class Mammalia:

I. Subclass Prototheria - “1st beasts”, egg layers A. Order Monotremata - Monotremes, egg- laying , most primitive MG Examples: 1. Duckbill 2. Porcupine anteater or

Gland Tubes

• No • No internal milk storage • Milk secreted onto and lapped up by young • https://www.youtube.com/watch?v=NG uIezLFidY (18:00) When does a initiate ?

• In cows and : • Placenta detaches • ↓ and • ↑ • 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: - 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

• 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 or 2 to 4 years for males Kangaroo Kangaroo Kangaroo Kangaroo Kangaroo Kangaroo Kangaroo 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:

II. Subclass Theria - “beasts,” born alive B. Infraclass Eutheria -”true beasts”, animals with placentas, highly developed MG 4,000 species Humans, cows, , , bats, , whales, , shrews, armadillos, etc.

PHYLOGENY & ONTOGENY

Ontogeny- the life history or biological development of an individual organism (or ). The relationship of to other . Gland and Secretion Types

Exocrine Endocrine Secreted by ducts Not secreted by ducts Secretion poured directly at site Pour into the Secrete enzymes Secrete Control short term activity Control long term of target organs Examples: Gastric gland, Examples: , , sweat glands gland, Secretion

• Secretions excreted via exocytosis from secretory cells into an epithelial-walled , 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 and ) 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

Sebaceous Glands

• Simple branched acinar gland

• Gland has multiple cell layers

• Most numerous adjacent to sheath and duct opens to

• 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. 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 Overactive Sebaceous Glands

Cradle Cap Acne Eccrine Gland

• Type of • Simple, unbranched • Terminates in coil in (corium) • Ductal portion is 2-3 layers of cells • Secretory portion is 1 layer of cells • Secretion released (diffuses) through • 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?