Breast histology

Question 1

Describe the basic structure of the breast

Answer 1

1. Each breast is made up of 15-25 secretory lobes. Adjacent to the secretory lobules is fibrous tissue amongst this exist suspensory ligaments which extend from dermis od the skin to the deep fascia overlaying the muscle of ant. chest wall. This is then surrounded by adipose tissue.
2. Each of theses lobes is a compound tubular acinar gland. The acini empty into ducts.
3. The ducts from each lobule empty into a lactiferous duct that empties onto the surface of the nipple.
4. These ducts are surrounded by smooth muscle in the regon of the nipple, contraction of which makes the nipple become errect.

Question 2

What is the basic functional secretory unit of the breast and describe it ?

Answer 2

The terminal duct lobular unit (TDLU):

1. Terminal ductules lead into an intralobular collecting duct which leads into the lactiferous duct for that lobe.
2. The lactiferous duct leads to the nipple, passing through an expanded duct region near the nipple termed the lactiferous sinus.

Question 3

Describe the structure of a lobule

Answer 3

• They have both extra & intralobular ductus which join/drain into the lactiferous duct for that lobe
• Within each lobule is rudimentary secretory acini/terminal ductules & loose connective tissue surrounding the acini (allows room for rapid expansion in pregnancy)
• The acini are lined by secretory cells, which are surrounded by myoepithelial cells which are contractile cells

Question 4

What is a lobe made up of ?

Answer 4

Lobules

Question 5

What is the linning of the lactiferous duct ?

Answer 5

Changes from statified cuboidal to stratified sqaumous epithelium as it approaches the surface of the nipple

Question 6

Describe the structure of the nipple

Answer 6

• It has a wrinkled sruface covered by a thin layer of highly pigmented straified squamous epithelium
• It has a core of dense irregular connective tissue, mixed with bundles of smooth muscle

Question 7

What changes occur during the menstrual cycle in the mammary glands?

Answer 7

During the luteal phas the epithelial cells increase in height, the lumen of the ducts become enlarged & small amounts of secretion appear in the ductus

Question 8

During pregnancy what changes occur in the mammary glands?

Answer 8

1. In the 1st trimester there is elongation and branching of the smaller ducts + proliferation of the epithelial cells of the glands and the myoepithelial cells.
2. In the 2nd trimester glandular tissue continues to develop with differentiation of secretory alveoli. Also, plasma cells and lymphocytes infiltrate the nearby connective tissue.
3. In the 3rd trimester secretory alveoli continue to mature, with development of extensive rER.

These changes are accompanied by a reduction in the amount of connective tissue and adipose tissue present.

Question 9

What is the composition of breast milk ?

Answer 9

• 88% water
• 1.5% protein (mainly lactalbumin and casein)
• 7% carbohydrate (mainly lactose)
• 3.5% lipid

With small quantities of: ions, vitamins and IgA antibodies

Question 10

Following menopause, what happens to the secretory cells of the TDLU and the connective tissue of the breast?

Answer 10

1. Secretory cells of the TDLU degenerate
2. Decreased fibroblasts & collagen & elastic fibers in connective tissue (hence saggy tits)