31.29
The Mammary Glands
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Q1: What is the basic structure of the mammary gland?
The mammary gland is a modified sweat gland consisting of 15 to 20 lobes separated by adipose tissue. Each lobe contains smaller compartments called lobules, which house grape-like clusters of milk-secreting glands termed alveoli. Connective tissue strands called Cooper's ligaments support the breast structure between these lobes.
Q2: How does milk move through the breast during lactation?
Myoepithelial cells surrounding the alveoli contract to propel milk into secondary tubules and mammary ducts. Near the nipple, these ducts expand to form lactiferous sinuses, where milk may be stored temporarily before draining into a lactiferous duct and emerging through openings at the nipple.
Q3: What hormones regulate milk production and release?
Milk production is primarily stimulated by prolactin from the anterior pituitary, with additional contributions from progesterone and estrogens. Oxytocin, released from the posterior pituitary in response to an infant's suckling, facilitates milk ejection. This hormonal regulation ensures milk is produced and released appropriately during lactation.
Q4: Where are the nipple and areola located on the breast?
The nipple is a pigmented projection at the center of each breast through which milk emerges via lactiferous duct openings. The areola is a circular pigmented area of skin surrounding the nipple that appears rough due to modified sebaceous glands. Both structures are visible external features of the breast.
Q5: How are the breasts attached to the chest wall?
Female breasts are hemispheric projections attached anteriorly to the pectoralis major and serratus anterior muscles by a dense, irregular connective tissue layer called fascia. Suspensory ligaments, also known as Cooper's ligaments, extend between the skin and fascia to provide additional support and maintain breast position.
Q6: What are alveoli and what is their function in the breast?
Alveoli are grape-like clusters of milk-secreting glands embedded within the lobules of the mammary gland. These specialized structures produce milk during lactation. Myoepithelial cells surrounding the alveoli contract to propel the produced milk into the ductal system for transport and storage.
Q7: What role do lactiferous sinuses play in milk storage?
Lactiferous sinuses are small expansions of the mammary ducts located near the nipple where milk may be temporarily stored before being released. These sinuses collect milk from the ductal system and hold it until the infant's suckling triggers oxytocin release, which causes myoepithelial contraction and milk ejection through the lactiferous ducts.