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By the end of this section, you will be able to:
  • Describe the structure of the lactating breast
  • Summarize the process of lactation
  • Explain how the composition of breast milk changes during the first days of lactation and in the course of a single feeding

Lactation is the process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to an infant sucking at the nipple. Breast milk provides ideal nutrition and passive immunity for the infant, encourages mild uterine contractions to return the uterus to its pre-pregnancy size (i.e., involution), and induces a substantial metabolic increase in the mother, consuming the fat reserves stored during pregnancy.

Structure of the lactating breast

Mammary glands are modified sweat glands. The non-pregnant and non-lactating female breast is composed primarily of adipose and collagenous tissue, with mammary glands making up a very minor proportion of breast volume. The mammary gland is composed of milk-transporting lactiferous ducts, which expand and branch extensively during pregnancy in response to estrogen, growth hormone, cortisol, and prolactin. Moreover, in response to progesterone, clusters of breast alveoli bud from the ducts and expand outward toward the chest wall. Breast alveoli are balloon-like structures lined with milk-secreting cuboidal cells, or lactocytes, that are surrounded by a net of contractile myoepithelial cells. Milk is secreted from the lactocytes, fills the alveoli, and is squeezed into the ducts. Clusters of alveoli that drain to a common duct are called lobules; the lactating female has 12–20 lobules organized radially around the nipple. Milk drains from lactiferous ducts into lactiferous sinuses that meet at 4 to 18 perforations in the nipple, called nipple pores. The small bumps of the areola (the darkened skin around the nipple) are called Montgomery glands. They secrete oil to cleanse the nipple opening and prevent chapping and cracking of the nipple during breastfeeding.

The process of lactation

The pituitary hormone prolactin    is instrumental in the establishment and maintenance of breast milk supply. It also is important for the mobilization of maternal micronutrients for breast milk.

Near the fifth week of pregnancy, the level of circulating prolactin begins to increase, eventually rising to approximately 10–20 times the pre-pregnancy concentration. We noted earlier that, during pregnancy, prolactin and other hormones prepare the breasts anatomically for the secretion of milk. The level of prolactin plateaus in late pregnancy, at a level high enough to initiate milk production. However, estrogen, progesterone, and other placental hormones inhibit prolactin-mediated milk synthesis during pregnancy. It is not until the placenta is expelled that this inhibition is lifted and milk production commences.

After childbirth, the baseline prolactin level drops sharply, but it is restored for a 1-hour spike during each feeding to stimulate the production of milk for the next feeding. With each prolactin spike, estrogen and progesterone also increase slightly.

Questions & Answers

How does blood circulate in the upper limbs
Mary Reply
describe the muscles found in the heart
Atotwe Reply
myocardial
Kenndy
thank you very much
Atotwe
asalamu aleikum
Cabdala
waalekum salam
Tifu
types of connective tissues?
Tifu
what is a muscular system and details about it
Jackson Reply
what is the type of homones responseble for blenking of eyes
Moses Reply
what are the functions of cell?
Keyirangzile Reply
how does the femur act as a lever?
Mutoni Reply
what is stumac
Abdussalam Reply
What is phagocytosis
Mohamed Reply
Phagocytosis, process by which certain living cells called phagocyte
Sadashiv
It is the process that is carried out by the immune system of the body, that certain specialized immune cells (macrophages, Nks, dendritic cells, etc) that engulf and neutralize the foreign substances that invades the body.
Wesley
So that they can be predicate out of the body.
Wesley
phagocytosis is the process by which living cell or yh plasma membrane engulf large molecules into it internal environment ... it also known as food feeding
Boateng
all that you are say what does it mean?
Dzah
simply is the way the immune system fights foreign bodies by engulfing them..
Dzah
by the help of the immune cells...
Dzah
The process by which a cell engulfs particles such as bacteria, other microorganisms, debris of dead cell.e.g: neutrophils and monocytes (types of white blood cells)
Tifu
what are the six types of connective tissues
Athieno Reply
loose and dense , cartilage and bone , blood and lymph
Queen
describe the structure of the liver
Atwebembeire Reply
what is specific name for spinal cord
Stanley Reply
what is the best description for skeletal muscular
Stanley
what is the best description for skeletal muscular
Stanley
costs of bones of skeleton, their joint s and voluntary
grace
what are examples of long bones
grace
example of long bones will be the femur tibia and humerus and even radius
Nina
so basically long bones are mostly in you hands and feets
Nina
skeletal muscular are voluntary and are attached to the bone by tendon which help maintain the posture and position of the body and it also protects internal organs in the abdominal region
Nina
The specific name for spinal cord is coccygeal segment
Sandra
what are the hormones responseble for blenking of eyes.
Moses
Smallest unit of life
Kimberly Reply
cell
Adnan
The cell is the smallest structural and functional unit of living organisms, which can exist on its own. Therefore, it is sometimes called the building block of life. Some organisms, such as bacteria or yeast, are unicellular—consisting only of a single cell—while others, for instance, mammalians, a
Adnan
cells are the building blocks of life
Stanley
Describe the complications of fracture
Zaifa Reply
functions of connective tissue
renah Reply
binding and structural support protection Insulation Transport of materials
Priyantha
Is there any artery that carries oxygenated blood? what's the name?
Sayo
Deoxygenated blood enters the right atrium from the vena cava. Blood moves into right ventricle. Blood is pumped into the pulmonary artery. The pulmonary artery carries deoxygenated blood to the lungs. The blood becomes oxygenated in the lungs. Oxygenated blood leaves the lung via the pulmonary
Danni
all arteries carry oxygenated blood except pulmonary artery
SAMSON
protection,,,,,transport,,,,,,connection,,,,,,,support,,,,,these are functions of connective tissue
Tifu
and insulation
Tifu
what is a local potential
Nandi Reply
potential of neurons
vipin
response of neurons against sodium ion Chanel
vipin
The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.
Adnan

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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