LACTNET Archives

Lactation Information and Discussion

LACTNET@COMMUNITY.LSOFT.COM

Options: Use Forum View

Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Reply To:
Lactation Information and Discussion <[log in to unmask]>
Date:
Tue, 10 Apr 2001 12:29:48 EDT
Content-Type:
text/plain
Parts/Attachments:
text/plain (85 lines)
In the book LACTATION Physiology, Nutrition, and Breast-Feeding (1983) by
Neville and Neifert there are histology slides and electronmicrographs of the
ductal system in a few different women who were deceased.  One was a woman
who died 48 hours after last nursing her child. Another was a nulliparous 15
y o.
parenchyma are functioning elements; stromal are supportive framework

"Prior to pregnancy, the mammary gland from the adult female is in an
inactive state which permits easy identification of its parenchymal and
stromal organization.  ...the lobules consist of tubules or ducts lined with
epithelium and embedded in a connective tissue stroma. They are widely
separated and connective tissue and adipose tissue are the predominate
elements. The interlobular connective tissue is dense, fibrous, and markedly
less cellular than the intralobular connective tissue."

"At this stage of development, there is only a scanty contribution from the
glandular parenchyma.  A few budlike sacculations may be seen arising from
the ducts, but the gland consists predominantly of lactiferous, interlobar,
and interlobular ducts.  The larger ducts are lined by stratified cuboidal
epithelium, except near the nipple where they are lined by stratified
squamous epithelium."  "The few alveoli present consist of simple cuboidal
epithelial elements without distinctive morphologic features. They are
virtually indistinguishable from the epithelium of the smaller ductal
channels."

"A point of importance ... is that the glandular parenchyma of the breast
apparently does not respond to the hormonal environment in a totally
synchronous fashion.  Different areas within the same breast may change to
greater or lesser degrees."

"A modest, though discernible, degree of alveolar development occurs at the
time of menarche, but with the advent of the hormonal changes of pregnancy,
the mammary gland undergoes a spectacular phase of growth and proliferation.

"The active phase is characterized by a rapid increase in the number of
alveoli.  Growth occurs at the terminal portions of the intralobular ducts
which branch numerous times to end in alveolar sacculations.  In the early
trimester, the secretory alveoli are collapsed, but as gestation advances the
saccules expand and enlarge, transforming the gland into a classic
tubuloaveolar structure.

"During the first few days after parturtion, a significant change occurs in
the secretory elements of the mammary gland.  Within the first 12 hours, the
cells lining the alveolar sacculations become high cuboidal to columnar and
develop classic cytologic characteristics of an exocrine cell.

"Regular suckling stimulates the continuation of milk secretion.  When this
is stopped, the gland quickly ceases its activity and undergoes a relatively
rapid phase of regression.  Within a few days, the milk remaining in the
alveolar lumina and ducts is resorbed.  A steady decrease in parenchymal
elements ensue with the concomitant reappearance of larger amounts of
interlobular and interlobar connective tissue.  The gland, however, does not
regress to its original prepubertal state and many of the alveoli persist.

"Within the alveolar epithelium a great amount of lysosomal and autophagic
activity accounts for the initial regression of the epithelium."  "The gland
then remains in a resting condition until the advent of the next pregnancy
wherein the developmental cycle of proliferation and secretion commences."

"Near the menopause, but usually before true cessation of cyclic ovarian
functions, the mammary gland and surrounding breast tissues begin to atrophy.
 Loss of tissue begins initially in the peripheral aspects of the lobe, but
eventually almost all alveolar and interlobular ductal elements are lost "

Part of their summary:
"Prior to pregnancy the gland is composed primarily scattered ductal elements
which drain into a series of collecting or lactiferous ducts.  These ducts
drain into the nipple. Upon appropriate hormonal stimulation, the mammary
ducts develop numerous secretory alveoli which cyclically produce milk and
empty their contents into the ductal system.  Upon termination of suckling, a
raid regression occurs in the alveolar and ductal trees with end stage
involution occurring after the menopause.

They do say most of this is "predicated on animal models as little
information is available on the structure and functional morphologic changes
seen in the human."

Mardrey Swenson IBCLC

             ***********************************************
The LACTNET mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software together with L-Soft's LSMTP(TM)
mailer for lightning fast mail delivery. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html

ATOM RSS1 RSS2