Anatomy and physiology of the lactating breast

Clinical tip for MER

oxytocin causes * myoepithelial cells to contract * uterine contractility *increases skin temp of breast therefore temp maintenance for infant * decreases maternal anxiety causes thirst

Lactose

paracellular pathway between lactocytes remains open, lacotse can escape from the milk secretion into the blood stream. Passes in maternal urine.

Previous breast surgery

periareolar incisions that severe the 4th intercostal nerve will prevent the functioning of the milk ejection reflex. This is routine for reduction mammaplasty

Areola

pigmented Areola changes associated with serum levels of placental lactogen and prolactin elicit odors that direct baby to nipple Studies - high number of Montgomerys follicles = higher weight gain

example of breast growth: low milk supply

placenta praevia with bleeds, SGA, LSCS , small breast growth in pregnancy Poorly implanted placenta, LSCS SGA - small baby stimulating supply poor breast growth

Hyperdenia

presence of additional mammary tissue with or without nipples most common - axilla no anatomical connection to the breast May become engorged. Treatment is symptomatic - cold pack,antiinflammatories

PROLACTIN RECEPTER SITES

prolactin moves into lactocytes and stimulates syntesis of breast milk components

EMPTY ALVEOLUS

prolactin receptors return to the normal shape. Prolactin moves through and increases milk synthesis

Involution

reversal of mammary changes that occurred during pregnancy. breast milk left in breast for longer periods during weaning, FIL accumulates and alveolar distension reduces transfer of prolactin into alveoli, slowing milk secretion. More than one feed per day is necessary to maintain milk secretion Milk becomes more colostrum like in compostion when voloume falls below 400mls/day

role of the lactocytes

secrete breastmilk components into the alveolar lumen

Feedback inhibitor of lactation( FIL)

small whey protein

Lymphatic drainage

subareolar plexus plus superficial and deep nodes drain lymph primarily to the lymphatic nodes in the axilla

FULL ALVEOLUS

walls expand and stretch leading to PROLACTIN RECEPTORS resulting in a decrease in milk synthesis

L3 and prolactin

Suckling response stimulates 4th intercostal nerve to release oxytocin and prolactin peaks about 45 minutes after a breastfeed returns to pre feed levels within 3 hours of breastfeed decreases over time. Intensity of suckline influences the degree of prolactin release (think twins)

Lactocytes

are milk producing cells of alveoli

Stroma

connective tissue, adipose tissue, blood vessels, lymphatics and nerves

AUTOCRINE control

determined by infants appetite

Pre glandular an abnormality of hormonal functioning

directly related to hormonal issues such as a retained placenta or postpartum thyroiditis.

Ducts

average of 9 - 10 ducts connecting alveoli to the exterior at the nipple diameter is individual Widening is associated with branching Follows a convoluted route Returns ot resting diameter after milk ejection Storage of milk does NOT occur in ductal system

Blocked ducts

A well latched baby is more effective. Pointing chin does not clear that duct.

Clinical tip for pregnancy ending after lactogenesis 1 has occurred

A woman whose pregnancy ends any time after lactogenesis I has occurred (ie possibly from 15 wks) may proceed into secretory activation. At this early stage of pregnancy many women would not be aware of this possibility and will require you to discuss methods to suppress their lactation.

Parenchyma

ducts, lobes and alveolar

Tail of Spence

axilliary tail lobes that project towards the underarm

Montgomery's follicle

become enlarged Sebaceous glands providing lubrication and antimicrobial factors

Growth and Function

Breast growth = increasing levels of HPL (breast size) / healthy placenta Breast function = increasing levels of prolactin (placenta stimulating pituitary gland)

Anomalies of breast development

embryological development

Nipple discharge

!. Galactorrhea - a response to an increase in prolactin. Can happen in pregnancy, pituitary adenoma, hypothyroidism 2. Montgomerys - thin clear to brown nipple discharge may occur 3. Intraductal papillomatosis - bloody discharge. Benign. Can signafy a rupture of vascular stalk 4. Duct ectasia - common cause. Dilation of the terminal ducts. An irritating lipid forms producing an inflammatory reaction and nipple discharge

Flat nipples

equally challenging gentle stimulation of nipples in shower prior to feeding will condition nipples to be erect

Nipple

openings of milk ducts Smooth muscle Least important structure Baby being able to take a large portion of breast tissue to form a teat

3 major phases of growth that impact lactation

1. Embryological 2.Puberty 3. Pregnancy and lactation

Embryological

1st month of gestation : galactic bands - mammary ridges, milk ridges, milk lines ,milk streaks 5 th week - develop into a ridge nipples and areolae - mammary ducts a loose fibrous stroma secondary buds - duct system Infancy nipple usually inverted everting shortly after birth, inactive until puberty "Witches milk" - mild inflammatory response , babies can secrete small amounts of milk like substance

Fatty tissue

3 areas Subcutaneous Intraglandular Retromammary

FREQUENT MILK REMOVAL

= increase in available receptor sites

Supportive anatomy

Blood supply, lymphatic draininge, nerve supply,fatty tissue, coopers ligaments

Hyperplasia- greater than 400mm3

overdevelopment of breast

Examples of food colours

Carrots - orange Beetroot - pink Sports drink - green Licorice - khaki

Clinical tip - blocked ducts

Clearing a blocked duct is important. A localized area of the breast where milk stasis occurs and remains for an extended period will 'shut-down' production of milk by the affected alveoli.

Colour

Colustrum - thick, clear to bright orange depending on the amount of beta carotene in mothers diet Transitional milk - thick and creamy Mature milk - thin bluish shade to whiter depending on the amount of fat in that sample

Secretory activation

breast swelling milk leakage change in appearance of milk change in infant cures breast fullness breast tingling increase in metabolism (maternal) and increase in mammary blood flow

Nerve supply

From branches 4,5 and 6 intercostal nerves aerola is the most sensitvie part of the breast lowermost branch of the 4th intercostal nerve becomes more superficial close to the areaola in the lower outer quadrant (about 5 o'clock on left breast and 7 o'clock on the right breast

Alveolus

Functional unit STORAGE Lobules

Colostrum in secretory differentiation

High concentrations of NA, CL, immunoglobulins and lcatoferrin. Lactose concentration is low

Breast growth

Human placental lactogen

HPL

Human placental lactogen (hPL), also called human chorionic somatomammotropin (HCS), is a polypeptide placental hormone, the human form of placental lactogen (chorionic somatomammotropin). Its structure and function are similar to those of human growth hormone. It modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus

Myoepithelial cells contract under the influence of

oxytocin

Nipple shapes Inverted

Iinverted - occurs during embryological stage An inverted nipple retracts into the breast whereas a normal nipple will remain everted

physiology of secretory activation

Lactation is influenced by a complex hormonal milieu including reproductive hormones (estrogen, progesterone, placental lactogen, prolactin, and oxytocin) and metabolic hormones (glucocorticoids, insulin, growth, and thyroid). The reproductive hormones act directly on the mammary gland, whereas the metabolic hormones act indirectly by altering endocrine response and nutrient flux to the mammary gland.[6] Ductal growth is primarily regulated by estrogen and growth hormone, and alveolar development requires progesterone, prolactin, and possibly placental lactogen.[7] During pregnancy, the high levels of circulating progesterone inhibit the secretory process of the mammary gland. Once the placenta is expelled after birth, progesterone levels decline rapidly, and increasing prolactin levels trigger the beginning of lactogenesis II, which is the onset of copious milk secretion. Oxytocin is essential for milk removal from the mammary gland.[8] In response to infant suckling, afferent impulses from sensory stimulation of nerve terminals in the areola travel to the central nervous system triggering the release of oxytocin from the posterior pituitary. In turn, oxytocin is carried through the bloodstream to the mammary gland where it interacts with specific receptors on the myoepithelial cells located on milk-secreting cells (alveoli) and ducts, initiating contraction of the cells, which results in expulsion of milk from the gland.[9] The main role of insulin appears to be in regulating nutrient fluctuation to the mammary gland by shunting nutrients away from traditional storage depositories, thereby making them more readily available for milk synthesis.[10] Thyroid hormones are essential for efficient milk production and, in animals, appear to be necessary for mammary responsiveness to growth hormone and prolactin during lactation.[11] One study in women with insufficient lactation found that the nasal administration of thyrotrophin-releasing factor (TRH) increased prolactin and daily milk volume.[12] In this randomized, double-blinded study, 19 women with insufficient lactation (< 50% of normal milk yield) were allocated to receive TRH or a placebo nasal spray. At the end of 10 days of treatment, milk yield increased significantly (P = .014) in the TRH group from a mean of 142 ± 33.9 g/d to 253 ± 105.3 g/d compared to no change in the placebo group. Additionally, prolactin levels increased in the TRH group from a mean of 117 ± 45.2 µg to 173 ± 55.5 µg (P < .001), whereas in the placebo group prolactin levels decreased from 137 ± 69.5 µg to 82 ± 37.7 µg. The early influence of these reproductive and metabolic hormones sets the stage for a transition to the autocrine function of the mammary gland. Autocrine control, also known as local control, refers to a mechanism whereby the gland regulates its own function through the local production of hormones and growth factors.[13] Evidence that the rate of milk secretion within individuals (and between breasts in the same mother) is directly correlated with the frequency of milk removal strengthens the theory of local control.[13,14] The mechanisms that regulate local control are not fully understood, but may include factors such as intramammary pressure,[15] milk removal,[4] bioactive factors in the milk that interact with milk cell membranes,[13,16] or a combination of these factors.

Secretory Activation

Lactogenesis 2 Copious secretion of milk *Milk synthesis is under endocrine control *characterised by a decrease in Na and total protein and an increase in lactose and citrate * occurs about 30 - 40 hours after birth of the infant and removal of placenta progesterone levels fall rapidly serum prolactin lavels are high at birthing osmotic transfer - lactose secretion by the lactocyte into the colostrum increases Other hormones - insulin, throxine and glucocorticoids Hormonally driven

Endocrine control

Lactogenesis 2 is controlled by hormones

L3

Lactogenesis III is the maintenance of milk secretion and is under autocrine control. This control requires regular removal of milk from the breast for ongoing milk secretion. A small whey protein, feedback inhibitor of lactation, acts as a negative feedback mechanism slowing milk secretion when there is a lot of milk in the breast. Increasing amounts of prolactin can move through the prolactin receptors on the basement membrane and into the alveoli as milk is removed from the breast, increasing rate of milk secretion. Breasts with a small breastmilk storage capacity will be more often emptied, leading to rapid milk secretion, while breasts with a larger breastmilk storage capacity will not be emptied so frequently and therefore rate of breastmilk secretion will be slower.

Glandular tissue

Lobes of breast 2/3'ss total breast tissue Average number = 9 Lobules- grape like clusters of alveoli Milk ducts - braches off main milk duct and ends at nipple largest portion of glandular tissu is found within a short distance ( 30mm radius) of nipple

Lactogenesis 3

Maintenance of milk secretion GALACTOPOIESIS milk continues to be removed for lactation to continue

Breast capacity

Maximum volume of milk able to be stored in breast at any one time Huge variations noted Alveoli store milk produced

Mastitis

causes tight junctions to open = saltier taste of milk at this time

Milk colour/discharge

Milky, green, gray or black discharges that are either unilateral or bilateral nad can be expressed from several ducts are not suggestive of cancer

Breastmilk composition

Na and cl fall lactose levels increase secretory IgA, lactoferring, and oligosaccharides reduces slightly

Preterm labour

Occasionally a woman in preterm labor, or 'threatened' preterm labor, may apparently move into secretory activation (while remaining pregnant). The physiology of this phenomenon isn't fully understood, but may have something to do with high corticosteroid levels and/or the routine administration of steroids. The corticosteroid competes with progesterone resulting in stimulation of the breast and causing secretory activation to occur before birth, with resultant poor lactation performance at term.

Lactation insufficiency

Pre glandular Glandular Post glandular

Breast function

Prolactin

Prolactin

Prolactin is produced by the anterior pituitary gland in the brain in response to the suckling of young after birth. * Red clover, fenugreek, or fennel can raise your prolactin levels. During pregnancy, a woman's body starts to produce higher than normal levels of prolactin. This hormonal increase causes the mammary glands to begin preparation for milk production, but elevated levels of the hormone progesterone prevent the breasts from lactating before birth. Progesterone production decreases shortly after giving birth as prolactin continues to increase, stimulated in part by the baby's first attempts to suckle at the breast, and this allows the breasts to begin lactating.

Greeny yellow

Pus from adenitis form of mastitis or breast abscess. If pumped will often seperate to bottom if left in milk collecting containiner (discard)

Breastfeeding in pregnancy

Rising blood levels of progesterone do not inhibit milk secretion when it is under autocrine control. That's why a mother can continue to breastfeed an older child during a subsequent pregnancy, or take the progestin-only contraceptive pill after lactation is well established.

Physiology

Secretory differentiation - Lactogenesis 1 Secretory activation - lactogenesis 2 lactogenesis 3

Increasing prolactin levels with a preterm baby with a weak suckling response

So double pumping, or pumping one side while breastfeeding from the other, should have the same effect on prolactin release as feeding twins simultaneously. That's useful to consider when I have a mother with a premature baby.

Breast engorgement

Stasis of milk in alveoli and increased interstitial fluid Massage and gentle arm rotation assist in facilitating the drainage of lymph massage towards the lymphatic nodes in the axilla

2. Puberty

The larche 9.5 - 10.3 years Estrogen and then progesterone Estrogenic effect - increase growth and branching in duct system Progesterone (luteal phase) - ducts and alveolar buds to proliferate Follicular phase - loss of hormonal support = some regression in growth Hormones: prolactin, FSH, luteinizing hormone, growth hormone, somatotropin, tsh, ACTH

Lactocytes

alveolar cells responsible for milk syntesis via four secretory pathways 1. Exocytosis 2. Lipid synthesis and secretion 3. Transport across the apical membrane 4. Transcytosis of interstitial molecules 5. Paracellular pathway - passage of substances through the tight junctions between the lactocytes rather than through the lactocyte

functional unit of the breast which secretes milk

alveolus

Breast capacity is determined by the

amount of milk that can be stored in the breast at any one time

The areola is

a scent organ of the breast

Hypoplasia - description

abnormalities of oestrogen and progesterone production during puberty and adolescence breast hypoplasia and a wide intermammary space (3.75cm, or greater between the breasts)

Polythelia

accessory nipples Common 2 - 6% Found anywhere on milk line - often mistaken for moles Sometimes associated with urogenital abnormalities

paracellular pathway

allows easy passage of components into and out of breastmilk

milk ejection

essential to the infants intake *minimal milk available to the infant PRIOR to milk ejection * oxytocin causes mypoepithelial cells to contract * neuro hormonal reflex * stimulation of nipple and areola ( lower branches of the 4th intercostal nerve supply) * hypothalumus is stimulated * releases oxytocin from posterior pituitary gland * prolactin is released from anterior pituitary gland * oxytocin travels via blood stream to breasts *Mypoepithelial cells contract forces milk into ductal system Oxytocin is released in a pulsatile fashion effective for about 1.5 - 2 minutes. No MER = hungry infant MER results of nipple/areola stimulation but becomes a conditioned reflex

Prolactin receptors

found on the basement membrane of the alveolus

Prolactin Receptors

found on the basement membrane of the alveolus as alveoli become distended, less prolactin is found

Intraductal papillomas or cracked nipples

fresh blood

Immune protection In discussions during pregnancy with the parents it is helpful to focus on the immunisation aspect (immune protection) of colostrum, assuring the mother the small amounts of colostrum will be sufficient for both the anti-infective and nutritional needs of her infant in the first 48 hours.

higher need for immune protection in first few days of life than large volume feeds

Physiology

https://www.slideshare.net/Prativas/physiology-of-lactation?qid=800aac3b-256d-4552-b693-ae1b2feef770

Prolactin Receptor Theory

increased suckling in early lactation stimulates the development of more receptors for prolactin Significant about 80 days postpartum, more receptors permitting transfer of more prolactin Encourage lots of breastfeeding in the early days postparum to create these addtional receptors

Blood supply

internal mammary artery - 62 - 70% of blood from medial side of breast lateral thoracic artery - supplies 31 - 40% Blood flow: 150 - 160ml/min

Pregnancy and Lactation

lactogenesis 1 = Secretory differentiation Lactogenesis 2 = copious milk production Lactogenesis 3 - maintenance of milk production

Colustrum

larger molecules sodium chloride Can pass through tight junctions as not tightly closed in first 3-4 days after birth.

Coopers Ligaments

loose structure of connective tissue which provides suppor for glandular and fatty tissues

Secretory differentiation

mammary epithelial cells differentiate into lactocytes with capacity to syntesize unique milk constituents Commences mid pregnancy Prolactin stimulates functional development Progesterone inhibits onset of copious milk secretion

Lactogenesis 1

mammary epithelial cells differnetiate into lactocytes with capacity to synthesize unique milk constituents (lactose) Ductal-lobular -alveolar system growth is rapid during first half of pregnancy Breast size increased Hormones = estrogen, progesterone, HPL and supportive metabolic and growth hormones including prolactin , epidermal growth factor, insulin like growth factor, parathryoid related protein, relaxin and cortisol Breast growth = increasing leveles of HPL Breast function = increasing levels of prolactin Progesterone holds the secretory process in checks

Rusty Pipe Syndrome

old blood