Lecture 19: Breast Flashcards
What are breasts?
Purpose of breasts
Mammary glands
Purpose
1) Feeding babies
2) Contraception
Describe how the breast is derived
- Mammary glands are modified sweat glands
- They are derived from tissue that is first identified in the mammary (or milk) crests that arise between the axilla and the groin
- Breast development begins with the formation of mammary buds at abou_t 6 weeks_
- The first development takes place as a d_own growth_ of the dermis to form the primary breast bud
-
Secondary buds develop from the pirmary bud
- These secondary buds will become the lactiferous ducts
- Under the influence of the steroid homrone, the buds develop lumens (become canalised
- oestrogen and progesterone
- By birth_, 15-20 lactiferous ducts_ are present
Mammary glands are _______
Mammary glands are modified sweat glands
secondary buds will become the _______
secondary buds will become the lactiferous ducts
When are the breasts fully developed?
At birth, the breasts are fully developed and could potentially make milk
Milk production would require hormonal stimulus
Because the fetus has been exposed to the placental steroids and maternal hormones at birth some babies do make colostrium like secretion called withc’s milk.
What is the word for…
noncancerous increase in the size of male breast tissue
Gynaecomastia
Describe the External structure of the breast
External structures:
1) Areola
- Pigmented circle of tissue surrounding the nipple
- Contains sebaeceous glands which give a granular texture to the surface
2) Body of breast - many different shapes
3) Nipple
- Raised (usually) cylindrical pigmented structure
- Can be inverted - common
- The lacterferous ducts join the skin at the nipple
Describe the Internal structure of the breast
1) Adipose tissue of the _pectoral fat pad (_major component)
- Fat gives the breast its texture and much of its shape
2) Breasts are supported by ligaments called the suspensory ligaments of Cooper or Cooper’s ligaments
- these ligaments are affected by age and hormones in pregnancy can become less supprotive
Breasts are supported by _________
Breasts are supported by ligaments called the suspensory ligaments of Cooper or Cooper’s ligaments
Describe the lobes of the breast
- The human breast contains 15-20 lobes each made up of milk secreting lobules
- Each of the lobules connects to a single lactiferous duct
- These structures look a little like a bunch of grapes
- The lactiferous duct runs towards the nipple and expands into a l_actiferous sinus (_broadening of the lactiferous duct)
- The laciferous sinuses (15-20) open onto the nipple and allow extraction of the milk
The human breast contains _____ lobes each made up of ___________
The human breast contains _15-20 l_obes each made up of milk secreting lobules
Each of the lobules connects to a ________________
Each of the lobules connects to a single lactiferous duct
The lactiferous duct runs towards the nipple and expands into a _______
The lactiferous duct runs towards the nipple and expands into a lactiferous sinus
Describe the hormonal influences on breast milk production
- Until puberty, the breast ducts don’t have alveoli- these start to develop during puberty, particualrly under the influence of oestrogen
- During the mentrual cycle, oestrogen and progesterone promote the growth University Entrance Exams_of alveolar buds_- successive cycles cause increased growth
- The steroids, particularly progesterone seem to prevent major milk production
- Progesterone is also a s_mooth muscle relaxant_ and prevents milk ejection
Until puberty, the breast ducts don’t have ____- these start to develop during puberty, particualrly under the influence of _____
Until puberty, the breast ducts don’t have alveoli- these start to develop during puberty, particualrly under the influence of oestrogen
Describe the hormones involved in the development of the breast during pregnancy
1) Oestrogen- essential for breast growth
2) Progesterone - induces side branching of ducts
3) Prolactin - ncessary for alveolar development but also stimulates casein and a-lactalbumin mRNAs (producing milk)
4) Growth hormone - (related to PRL) is important in some species
5) Insulin and cortisol - stimulate alveolar epithelial cell division
What are the differences between Resting mammary gland and active mammary gland
Active mammary gland has a lot more milk producing tissues and ducts (laciferous ducts)
For his lectures * must know blood normal ranges and lactational ammenorrhea lasts for 9 months and it is an effective form of contraception for most women
Lactation is a ____________
lactational ammenorrhea lasts for 9 months and it is an effective form of contraception for most women
Describe the role of progesterone in lactation
The steroids, particularly progesterone seem to prevent major milk production
Progesterone is also a smooth muscle relaxant and prevents milk ejection
Progesteron- from placenta and corpus luteum (main job is to cause quiescence in myometrium and in the cells that produce milk)
Describe the Endocrine control of lactation
- Prolactin is produced in large amounts in pregnancy and falls at birth
- Suckling of the infant on the nipple induces secretion of prolactin by the anterior pituitary
- Prolactin secretion is stimulated by a neuroendocrine reflex
- Cutting the nerve to the nipple prevents this reflex
- Suckling causes r_educed secretion of dopamine_ (prolactin inhibiting factor) into the portal blood
- Concurrently v_asoactive intestinal peptide (VIP)_ secretion by the paraventricular nnuclei is increased
- Both factors act on the lactotrophs to secrete prolactin
- Prolactin then induces the production of milk proteins
- The duration and extent of suckling correlates with prolactin secretion- two infants suckling induces more prolactin
- The level of prolactin correlates with the level of milk produced
- The milk ejection response (MER)
- Suckling also stimulates synthesis and secretion of oxytocin by the posterior pituitary
- Oxytocin i_nduces the contration of the myoepithelial cell_s of the alveoli causing ejection of the milk into the ducts
- Milk may also be ejected from the nipple
How is prolactin secreted?
- Suckling causes reduced secretion of dopamine (prolactin inhibiting factor) into the portal blood
- Concurrently vasoactive intestinal peptide (VIP) secretion by the paraventricular nuclei is increased
- Both factors act on the lactotrophs to secrete prolactin
Suckling of the infant on the nipple induces secretion of _____by the ________
_____secretion is stimulated by a ____________
Suckling of the infant on the nipple induces secretion of prolactin by the anterior pituitary
Prolactin secretion is stimulated by a neuroendocrine reflex
The level of prolactin correlates with the level of ________
The level of prolactin correlates with the level of milk produced
The baby can control the amount of feeding- more suckling = more food
What is the secondary response of suckling?
- The milk ejection response (MER)
- Suckling also stimulates synthesis and secretion of oxytocin by the posterior pituitary
- Oxytocin induces the contration of the myoepithelial cells of the alveoli causing ejection of the milk into the ducts
- Milk may also be ejected from the nipple
What can stimulate the female repoductive tract to induce MER?
Suckling of the baby (release of oxytocin)
Even other stimuli e.g. crying or smell of a baby can induce the Milk Ejection Reflex (MER)
Prolactin then induces the __________
Prolactin then induces the production of milk proteins
The duration and extent of suckling correlates with prolactin secretion- two infants suckling induces more prolactin
Describe lactation and fertility
Prolactin can suppress secretion of the gonaotrophs FSH and LH particularly LH
(thought to be via an effect on Kissepeptin neuron in the hypothalamus)
Therefore lactating women often have no or irregular menstrual cycles
Thus lactation has a contraceptive effect (but not very reliable)
Describe Supernumeroury Nipples
Usually women only have 2 breatss, but some have addiitonal breast tissue
Usually this is found along the line of the embyronic milk ridge
Additional nipples can occur on the breast or along the milk ridge and lactigerous ducts can exit the breast at stites outside the nipple
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