Anatomy and Histology of the Breast Flashcards
In what week in fetal development do mammary ridges form?
4th wek
What do mammory rigdes form from?
From epidermis
What hormonal action leads to the formation of fetal breast development
Placenta-induced high levels of oestrogen in foeatal plasma levels
In what week do primary buds form in foetal breast development?
7th week
In what month do secondary buds for in foetal breast development?
4th month
What is the subsequent step in fetal breast development following secondary bud development?
Canalisation- – lactiferous ducts, open onto mammary pit – nipple. Alveolar formation and even milk secretion (witches milk) may occur in new-born infant – prolactin.
What percentage of breast nodules have symptoms of galactorrhea at birth?
5%
Which hormones influence pubertal breast growth
Oestrogen and progesterone
Enlargement of the breasts during puberty is mainly due to…
- fat deposition
- interlobular and intralobular connective tissue
- formation of more ducts by branching
What is gynecomastia?
Breast development in men
What causes gynecomastia?
Increased oestrogen and out of balance testosterone in men
What layer of the chest do the breasts reside?
Subcutaneous layer
What glands are located in the areola??
Sebaceous and sweat
What are the modified sweat glands of milk production (2).
Merocrine glands - protein leaving alveoli
Apocrine glands - lipids leaving alveoli
What paths do the arteries and veins to the breast tissue follow?
Path of the milk ducts
What arteries supply the breasts and what area of the breasts to they supply?
Subclavian artery – internal thoracic (perforating branches) – medial mammary branches.
Axillary artery – lateral thoracic – lateral mammary.
Small branches of the anterior and posterior intercostal.
Describe the venous drainage of the breasts
Most venous drainage is to the axillary vein, and the internal thoracic vein.
Describe the lymphatic system in relation to the breasts.
Ducts located in the connective tissue surrounding the alveoli.
Lymph drains from the nipple, areola and ducts to a subareolar lymphatic plexus. From there 75% of drainage drains to axillary and supra clavicular lymph nodes (lateral breast), and the parasternal lymph nodes (medial breast).
What percentage of lymph drains from the subareolar lyphatic plexus to the axillary, supraclavicluar lymph nodes and the parasternal lymph nodes?
75%
What is the clinical significance of the lymphatic drainage of the breast
Lymphatic drainage of the breast is important due to its role in metastasis of cancer cells in the breast. Cancer cells typically spread via lymph. Interference of lymphatic drainage by cancer cells can lead to lymphedema.
Which intercostal nerves and braches of these intercostal nerves supply the breasts?
Anterior and lateral branches of the 2nd to 6th intercostal nerves.
What does the autonomic nerves to the breasts control?
- Efelx secretion of prolactin and oxytocin.
Smooth muscle of alveoli = blood flow = engorgement and erection
- Myoepithelial cell contraction = let down reflex.
How many irregular lobes of breached tubuloalveolar glands make up the post-pubertal breast?
15-25
What aremammary gland lobules seperated by?
Connective tissue septae (suspensory/Cooper’s ligaments) radiating fromthe nipple.
What is the function of th suspensory/Cooper’s ligaments of the breasts?
- connect breast to muscle fascia (pec major & ser ant) beneath and dermis above
- provide support
- passage for blood, nerves, lymph
- maintain firm and standing appearance, loosen with age
Where is adundant adipose tissue located in the post-pubertal breast?
Interlobular spaces but much less in the intralobular connective tissue.
All interlobular ducts of each lobe end in one …
Lactiferous duct opening at the nipple.
Describe the epithlial types of the duct system of the breasts.
Simple cuboidal/columnar = Epithelium starting at alveoli
Two layers cuboidal = lactiferous sinus
Stratified squamous = terminal lactiferous duct
What is the order of structures in the ductal system of the breast from deep-> superficial?
Alveoli < intralobular duct < interlobular duct < lactiferous duct < sinus
An alveolus of the breast is composed of:
Single layer of secretory (cuboidal/columnar) epithelial cells
Basement membrane
Myoepithelial cells between epthelial cells and basement memebrane.
Lumen of alveolar ducts
Describe the glandular component of a post-pubertal inactive breast.
Glandular component consists mainly of undeveloped duct system with little or no lumen.
Are there alveoli in a post-pubertal inactive breast?
No = not functional
What type of tissue surrounds the ducts in a post-pubertal inactive breast
Loose connective tissue
What type of tissue is in between the lobes of a post-pubertal inacive breast?
Abundant fibrous connective tissue and adipose tissue between the lobes
What occurs during ovulation in a post-pubertal inactive breast?
Around ovulation time, LH + oestrogen increases size of ductal secretory cells – forms duct lumen and fluid accumulation in the connective tissue – hardening
What is mammogensesis?
In pregnant women, gestational preparation for milk synthesis takes place
What hormones are involved in mamogenesis and what are their effects on breast tissue?
- oestrogen – proliferation of the lactiferous ducts (ductal branching)
- progesterone – growth of secretory alveoli (maturation)
- human placental lactogen (hPL), prolactin, hCG and glucocorticoids (cortisol) are also involved
In mammogenesis, what causes an increase in breast volume?
- ductal branching
- proliferation and hypertrophy of secretory cells
- development of smooth muscle fibres along the lactiferous ducts
- eventually formation of many alveoli surrounded by myoepithelial cells
When is full gland and duct development completed in the proliferative/secretory stage of mammogenesis?
By the end of the 6th month
What occurs to connective tissue and adipose during the proliferation/secretion phases of mammogenesis
Decreases
What infiltrates loose connective tissue surrounding alveoli during the proliferation/ secretion stage of mammogenesis?
Plasma cells, lymphocytes and eosinophils
What happens to the areola and nipple during gestational dvelopment of the breast?
Becomes larger and more pigmented
What is the weight increase of the breast during secretory/proliferative stage of mammogenesis?
500-800g
Describe Lactogenesis stage 1:
Hormone-induced differentiation of secretory cells:
- Production of milk-specific components (lactose)
- Lactose in urine, marker for lactogenesis from week 10-22
- Formation of protein-rich, sticky, yellow colustrum
Describe lactogenesis 2:
Fully functional breast:
Occurs after birth (triggered by decreased progesterone + oestrogen).
High level prolactin = milk formation
Colustrum release in first 48 hrs.
Milk secretion replaced colustrum 2-3 days postnatally
What are the hormonal requirements for milk producion?
- Post-partum prolactin release
- PRL increase
- PIF decreased
What controls the amount of prolactin released for breast-feeding?
Supply and demand- Strength and duration of suckling induces increased secretion of prolactin
What are the hormonal requirements for milk ejection?
Suckling infant -> Sensory info-> paraventricular and supraoptic nucleus in hypothalamus-> increases production and release of oxytocin-> myoepithelial cells = contraction = let-down reflex
Why does lactation cause amernorrhea?
Breastfeeding women have a delay of the resumption of ovulation due to elevated prolactin. Reduced sensitivity of the pituitary to GnRH, reduced LH, reduced positive feedback. Also have decreased ovarian oestrogen production
How long does lactational amenorrhea last if woman is fully breastfeeding?
Around the first 6 months post-partum
What is functional involution?
Change from actively lactating to inactive breast, takes about 3 months
How longis the process of functional involution?
3 months
How does the absense of suckling cause functional involution?
Milk accumulation in alveoli and lactiferous ducts – distention of the breast:
- capillary compression – alveolar hypoxia and luck of nutrients
- rupture of alveolar wall
- phagocytosis of tissue debris
What occurs to the ratio of glandular tissue/ducts: Connective tissue/fat during functional involution?
The ratio is reduced
What occurs to secretory epithelium during functional involution?
Reverts to non-secretory. Back to post-pubertal state
What causes menopausal involution?
Oocytes depleted or not responsive to FSH:
During postmenopausal period, changes in ovarian hormonal (withdraw) leads to regression or involution of the breast – atrophy rather than inactivation
- lack of oestrogen – ductal changes (~ 3.5%)
- lack of progesterone – glandular (alveolar) changes (~ 23.5%)
Degeneration of what components of the breast tisse causes drooping?
Connective tissue fibroblasts, collagen and elastic fibres
What occurs to the coopers ligaents during menopausal invoution?
Stretched
What occurs to glandular tissue during menopausal involution?
Glandular tissue is replaced with fat and loose connective tissue
