melk

Plasma

Total milk quantity minus the fat content

Serum

Total plasma quantity minus the casein micelles

Solids-not-fat (SNF)

The total solids content minus the fat content
Consists of proteins, lactose, minerals, acids, enzymes, and vitamins

Total milk solids

Fat content plus the total solids-not-fat

Energy content of the milk

The lactose, protein, and fat content multiplied by their relative energy values

Mammogenesis

State of mammary gland from the onset of puberty and throughout pregnancy, when it develops to a functioning state

Lactogenesis

During the last trimester of pregnancy, when milk synthesis and secretion is established

Galactopoiesis

Establishment of mature milk and throughout lactation

Involution

Occurs at the end of lactation, with the breast slowly returning to its pre-pregnant state

Golgi/secretory vesicle pathway

Proteins

Milk proteins are synthesized in the rough ER. The proteins are modified in the ER lumen and transported to the Golgi apparatus in vesicles. The proteins are then processed and glycosylated in the Golgi apparatus. The proteins are next sorted to their final destinations and packaged into secretory vesicles. The secretory vesicles fuse with the plasma membrane and release their contents into the alveolar lumen.

Lactose

Lactose is produced in this pathway

Lactose is produced via the aid of the lactose synthase enzyme complex which is the combination of a alpha-lactalbumin and a gal-transferase, activating the fusion of the two sugars (galactose and glucose) that make up lactose

Glucose transporters move glucose to the mammary gland where it forms galactose as needed to form lactose

Lactose is osmotically active meaning it is pulling water into the secretory vesicles which dilutes the casein micelles

Lipid secretion

Fat droplets (made from triglycerides or fatty acids) are produced in the rough and smooth endoplasmic reticulum or, in the case of fatty acids, come in from the plasma.Tryglicerides diffuse out of the smooth endoplasmic reticulum and are forced together into droplets due to their non-polar nature. These droplets diffuse towards the apical membrane of the cell and push up against this membrane. The membrane surrounds the fat droplet and it exits as a milk fat globule. This cell membrane coating prevents the fat from diffusing into the milk.

These micro lipid droplets appear in milk without a cell membrane. There is no known mechanism for this; however, the leading theories are that the micro lipid droplets diffuse out through the cell membrane, are somehow exocytosed, or small vesicles interact with the lipid droplet in a way that forms a double membrane layer which exocytosis the membrane bound lipid droplet to the outside

Eccrine secretion of water and minerals

Ion pumps and channels

Intracellular concentrations fluctuate based on if the tight junction is closed or open

If the tight junction is closed, all the ions are pumped through the cell

Transcytosis

The mechanism that transports proteins from the extracellular space into the milk space.

Intercellular space proteins (IGA) interact with a poly immunoglobulin receptor which binds to the IGA, forming a dimeric sIGA. During this process the receptor splits off of the basal membrane, freeing the IGA molecule within a vesicle. This free IGA retains a small amount of the receptor and once it is secreted it is called secretory IGA.

These vesicles are then sorted as they move through the apical cell. When they reach the apical membrane, they exocytose the contents of the vesicle

IGA is important for protecting the infants gut health

IgG follows a similar mechanism

IgG is responsible for providing immune cells to the infant

Paracellular transport

Where the junctions between the cells open up and allow the flow of anything within the cytoplasm into the milk.

List some of the factors affecting composition

Species breed, feed, stage of lactation

Breeds effect on milk composition

Holsteins and brown swiss have lower fat content (3.5%) and higher milk production

Gernseys and jerseys have higher fat content (5.2%)

Feeds effect on milk composition

High fat and/or low roughage diets can reduce the fat content of milk.

Diet has small effects on protein content and none on lactose content

Describe how milk components impact physical and chemical properties

Density, freezing point, color, pH, acidity, flavor of the milk

Milk density’s impact on physical and chemical properties

The density of milk products can be used to convert volume into mass and mass into volume, to estimate the amount of solids present in milk, and to calculate other physical properties.

Milk freezing point’s impact on physical and chemical properties

The freezing point of milk is lower than the freezing point of water because of the dissolved components in milk.

The freezing point of milk is 31℉

Milk pH’s impact on physical and chemical properties

The pH of milk is higher, or more alkaline, outside of the cow than inside the cow due to loss of carbon dioxide to the air.

The pH is determined after processing the milk to assure that lactic acid is being produced at the desired rate by added microorganisms during the preparation of cheeses and fermented milk.

Milk acidity’s impact on physical and chemical properties

Titratable acidity is the amount of alkali required to bring the pH to neutrality.

This property of milk is used to determine bacterial growth during fermentations, such as cheese and yogurt making, as well as compliance with cleanliness standards.

Naturally, there is no lactic acid in fresh bovine milk, however, lactic acid can be produced by bacterial contamination, but this is uncommon.

The titratable acidity is due to the casein and phosphates.

Benefits associated with bacteria in milk

Indicator of improper or inadequate pasteurization or contamination after pasteurization.

Can produce chemical changes that are desirable in the production of fermented dairy products because they are able to ferment lactose to lactic acid.

Problems associated with bacteria in milk

Pathogenic bacteria can cause foodborne illnesses

Spoilage microorganisms cause degradation of proteins, fats, and carbohydrates and the milk’s texture, color, taste, and smell is deteriorated.

How do somatic cells get into milk and cultured dairy products

Enter milk primarily as a result of inflammation in the cow's udder (mastitis), where they are released as part of the immune response to infection

How do microorganisms get into milk and cultured dairy products

Enter milk from various sources including the cow's skin, the milking environment (like contaminated equipment), and potentially from the air, with infections in the udder being a significant contributor to both somatic cell and microbial contamination in milk

Calcium

Functions in the mineralization of bones and teeth, muscle contraction and relaxation, nerve functioning, and blood clotting.

Ion

Carries oxygen as a part of hemoglobin in blood or myoglobin in muscles, and it is required for cellular energy metabolism.

Magnesium

A factor involved in bone mineralization, the building of protein, enzyme action, normal muscular function, transmission of nerve impulses, proper immune function and maintenance of teeth.

Phosphorus

Involved with mineralization of bones and teeth, it is important in genetic material, in cell membranes as phospholipids, in energy transfer, and in buffering systems.

Potassium

Facilitates reactions, including the making of protein.

Involved in the maintenance of fluid and electrolyte balance, the support of cell integrity, the transmission of nerve impulses, and the contraction of muscles, including the heart.

Sodium

Maintain normal fluid balance in the body. Sodium is critical to nerve impulse transmission.

Zinc

Associated with hormones, it is needed for many enzymes, it is involved in making genetic material and proteins, immune cell activation, transport of vitamin A, taste perception, wound healing, making of sperm, and normal fetal development.

Describe the principle involved in manufacturing cottage cheese

The destabilization of casein combined with a lowering of the pH to the isoelectric point of the protein (roughly 4.5) causes the neutralization of the negative charge on the outside of the casein micelles allowing the casein micelles to come together to form the curds commonly found in cottage cheese, separating it from the whey

Describe the principle involved in manufacturing greed yogurt

Acidification of milk may be used to form many fermented products such as yogurt and to fractionate the milk proteins to produce acid casein.

Components of bovine milk that contribute to non-protein nitrogen

Nucleotides

Nucleic Acid in nucleosomes

Urea

Free amino acids

Enzymes in the bovine milk

Lipoprotein lipase, lactoperoxidase, xanthine oxidase, alkaline phosphatase

Lipoprotein lipase

Catalyzes the hydrolysis of triglycerides to free fatty acid.

This reaction causes dairy products to have soapy, bitter, rancid, and unclean flavors.

Lactoperoxidase

Catalyzes the oxidation of unsaturated fatty acids leading to the development of oxidized flavors.

Can act as an antibacterial in the presence of thiocyanate and peroxide to kill salmonellae, shingellae, and pseudomonads

Xanthine oxidase

Catalyzes non-specific oxidation of dairy products

Alkaline phosphatase

Almost completely inactivated by pasteurization, and it is therefore used as an index of the efficiency of such heat treatments.

Describe the effects of carbonate on the free calcium in the milk.

Cow's milk has a lower pH than human milk,

Less tendency to make carbonate = less calcium carbonate combined in the milk (more free calcium).

Describe the relation between milk fat composition and melting point.

A higher proportion of saturated fatty acids leads to a higher melting point

Preterm milk

Similar to the composition of colostrum, but it has higher levels of Immunoglobulin A, lactoferrin, and lysozyme to support the immune system and development, LC-PUFAs are higher and stay high for the first 6 months in the mother, has 24 calories per ounce compared with 20 cal per ounce of regular milk.

Colostrum

Thick, yellowish milk that comes in for mothers at the time of birth or slightly before birth, lasts for 2-4 days after birth, low in volume but high in protein, fat soluble vitamins, minerals, and antibodies.

Transitional

Replaces colostrum, still a creamy milk that lasts for about 2 weeks and leads to engorgement of the breasts as they come in, has high levels of fat, lactose, vitamins, and more calories than colostrum

Mature milk

Follows transitional milk near the end of the 2nd week after birth, thinner and contains more water than the colostrum or transitional milk, about 80-90% water and carbohydrates, proteins, fats needed for development.

Non-nutritive bioactive components of human milk

Alpha-lactalbumin complex, immune cells, lactoferrin, glycoproteins, secretory IGA, lysozyme, B lymphocytes, T lymphocytes, neutrophils, macrophages

Alpha-lactalbumin complex

A-lactalbumin, oleic, and linoleic acid increases antibiotic activity against MRSA, and anti-tumor activity.

Immune cells

Get ingested in the milk, increase when the mother or baby has an infection

Lactoferrin

Helps with iron absorption while inhibiting bacteria from absorbing iron, protects against tumor growth, modulator of immune responses, aids in bone development.

Glycoproteins

Mucins, bile salt stimulated lipase, lactadherin, all protect against infection from viruses, bacteria.

Secretory IGA

Given from the mother after she is exposed to pathogens, it makes more of the antibody to give passive immunity to the child.

Lysozyme

Breaks down the outer cell wall of bacteria, more concentrated in human milk than bovine milk, resistant to breakdown in the stomach (like trypsin).

B lymphocytes

A phagocyte that produces antibodies

T lymphocytes

Phagocyte that kills infected cells directly (apoptosis) and mobilizes the immune system.

Neutrophils

Lymphocytes that attack and digest bacteria, most abundant in colostrum.

Macrophages

Kill microbes in the gut and produce lysozyme, mobilize the immune system

R-type

Produce large numbers of very immature young after a short gestation period

Produce more milk than k-type species

K-type

Produce very few well-developed young

Milk is lower in protein than r-type

How might species evolve to have different numbers of glands at different locations?

Species evolve to have different numbers of glands at different locations to accommodate for the size of their litter and the most accessible location for the offspring to feed. All mammary glands originate from the duct in early embryonic development

Human structure and function of mammary glands

Milk is held in the alveoli until there is a hormonal signal that indicates it should be released (oxytocin)

The oxytocin interacts with the myoepithelial cells causing contractions in the smooth muscle surrounding the secretory cells which enables the removal of the stored milk

Proteins produced on the ribosomes of the alveolar epithelial cell migrate through the golgi system into the secretory vesicles which are then released from the cell into the milk

Capillaries produce the precursors for milk

Two teats

DO NOT have a gland cistern

Most of the milk is stored in the alveoli

Each breast is an individual exocrine gland that functions and develops independent to extract materials from the blood and convert them into milk

Each lobe has its own opening through the skin of the nipple

No median suspensory ligament because they are separate glands

Circular smooth muscle is responsible for preventing milk from leaking

Bovine structure and function of mammary glands

Ducts feed into the gland cistern where a substantial portion of milk is stored; however, the greatest portion of milk is still inside of the alveoli

Below the gland cistern is the teat cistern which holds 10-50 ml of milk

At the end of the teat there is a sphincter

This prevents milk from flowing out when there is not pressure for it to be released

Bovine mammary glands have a significant amount of connective tissue

This is because it is required to support the immense weight and size of the udder

Suspensory ligament holts up the udder

Four teats

Streak canal (or teat canal)

What are the 3 fluid transport systems in a mammary gland

Blood

Milk Ducts

Lymphatic system

Palade

Separated various acinar from the mammary gland by disolving away connective tissue, resulting in secretory tissues whose biochemistry could then be studied via invitro biochemical assays

Linzel and Peaker

Transplanted the udder of a goat to conduct perfusion studies with an intact gland in isolation of the animal while still keeping the animal intact to observe blood flow, nutrient concentrations, and rates of nutrient extraction

Isolated mammary tissue slices

The tissue was destroyed to observe the enzymes that were only associated with mammary secretory cells

Isolated acini

Grind and find cell distribution

Electron microscopy

Electron microspy allowed individuals to observe the structures of these cells and form hypothesis about their function and how they may change during the lactogenesis process

Cell culture model system

Mammary tissue is digested with collagenase which breaks down the collagen tissue and hyaluronidase which breaks down interstitial fluid. The organoids (secretory cells) are cultured and undergo differential trypsinization into heterogeneous epithelial cells and fibroblasts. The fibroblasts and myoepithelial cells are washed off, leaving epithelial cells. Eventually the cells will produce proteins that join the membrane of each cell to another cell. After they replicate a number of time they will sensce

Structure and function of tight junctions

A specialized cell-cell junction that forms a continuous, barrier-like seal between epithelial cells, effectively blocking the movement of molecules through the space between cells (paracellular pathway), and thereby maintaining the separation of distinct tissue compartments

Conditions that open tight junctions

Parturition

Weaning

Pressure from milk production opens tight junctions and allow the flow of lactose and water back into circulation

Mastitis

Bacteria causing mastitis release small factors that activate immune cells and macrophages force their way between the epithelial cells, forcing open the tight junctions, creating an opening between the inside of the body and the outside of the body

Oxytocin

In high concentrations, the myoepithelial cells can overcontract and break tight junctions

Although the recommendations from WHO, CDC, etc., is exclusive breastfeeding for 6 months, an acceptible public health goal in the US according to the Healthy people 2020 (US DHHS) is approximately ___ % of babies

25%

Over the last decade, the rates of all breast feeding and rates of exclusive breastfeeding are

both increasing

Impacts of breastfeeding include ALL of the following EXCEPT

Preventng an inadequate number of calories for infants in the US.

Worldwide ____% of infants are exclusively breastfed for the first 6 months of life.

~34%

A mother is breastfeeding her 4 month old baby exclusively, is able to sleep for a 6 hour stretch at night without breastfeeding, and menses has not returned. Which of the following is correct regarding her chances of pregnancy?

She has a higher risk of becoming pregnant than if feeding every 2-3 hr, and should use a complementary family planning method if pregnancy is not desired.

Complementary foods should be started around 6 months of life because the baby needs higher amounts of which nutrient in his/her diet?

Iron

Consumption of bovine milk may have which of the following benefits? (check all that apply).

Decrease oxidative and inflammatory stress

Decrease in colon cancer

Prevention of metabolic syndrome, obesity, cardiovascular disease, hypertension and type 2 diabetes

Prevention of rickets, osteomalacia, osteoporosis Decrease oxidative and inflammatory stress

Decrease in colon cancer

Prevention of metabolic syndrome, obesity, cardiovascular disease, hypertension and type 2 diabetes

Prevention of rickets, osteomalacia, osteoporosis

List the top three milk producing countries, as of 2011. (bovine milk)

US, India, and China

Total milk production trends in the US have been increasing over the years due to which factors?

Cows are each producing more milk.

Larger efficient farms with more high prodcuing cows.

Cows in cool climates, such as UK, produce most milk in the months of April and May and the least in October, December, and January.

True

In the US, Americans tend to consume more milk in the cooler months and less milk in the summer.

True

Reasons that adults consume milk from different species include ALL of the following EXCEPT

milk is usually the lowest cost source of calories in the marketplace.

Which of the following are remedies for lactose intolerance?

Milk containing predigested lactose

Pills/drops of lactase

Consuming small amounts of foods with fermented lactose (yogurt)

Three cups of milk contains more the 50% of the RDA for ALL of the following nutrients EXCEPT:

energy (Calories)

Lymphatic ducts contain

Excess interstitial fluid

Alveoli contain

Milk

The vascular system contains

Blood

Which of the following is LEAST likely to be a rate limiting step in the synthesis of lactose by the mammary epithelial cells?

Uptake of galactose from the blood stream to the mammary cells.

Which of the following is the LEAST likely mechanism for secreting lipid into milk?

Enzymes that have been secreted by the mammary cell can synthesized fatty acids and triglycerides inside the alveoli and milk ducts.

In embryonic development of the mammary gland, the earliest feature to develop is

mammary ducts

In a normal cycle of lactation, the latest event to occur is...

involution

The nerves connecting the mammary gland to the brain have the a main function best described as..

release of oxytocin and control of sphincter muscle tone

Different species of mammals can differ from each other with respect to ALL of the following anatomical features EXCEPT...

The presence or absence of mammary glands in the female