Breast Anatomy and Histology

Question 1

Describe the components of of secretory tissue in a non-lactating breast

Answer 1

Made up of 15-25 lobes, each consisting of a tubulo-acinar gland drained by a series of ducts leading to the nipple

Adjacent to secretory lobules - dense fibrous tissue which is in turn surrounded by adipose tissue

Question 2

What are suspensory ligaments?

Answer 2

Amongst the fibrous connective tissue are some larger condensations that extend from the dermis of the skin to the deep fascia overlying the muscle of the anterior chest wall. These are referred to as suspensory ligaments.

These are often most pronounced in the upper breast and are thought to support the breast tissue.

Question 3

Name the basic functional secretory unit of the breast

Answer 3

Terminal Duct Lobular Unit (TDLU)

Question 4

What is the terminal ductal lobular unit (TDLU)?

Answer 4

terminal ductules lead into an intralobular collecting duct which leads into the lactiferous duct for that lobe.

Question 5

What is the lactiferous sinus?

Answer 5

An expanded duct region near the nipple through which the lactiferous duct passes before opening at the nipple

Question 6

Describe the structure and components of the lobule

Answer 6

1. Extralobular (leading to lactiferous duct) and intralobular (terminal units) ducts
2. Rudimentary secretory acini
3. Dense fibrocollagenous tissue surrounding the lobule
4. Looser connective tissue surrounding the acini within lobule
5. Adipose tissue b/w lobules

Question 7

What are the two types of epithelium found within the lobule?

Answer 7

Lining of acini - secretory epithelial cells which vary from cuboidal to columnar

These secretory cells are surrounded by myoepithelial cells (MEp) - contractile

Basal lamina surrounds the MEp

Question 8

What are the two types of epithelium found in the ducts?

Answer 8

1. Thin stratified squamous to stratified cuboidal

2. Myoepithelial cells

Question 9

Name the type of epithelium that covers the surface of the nipple

Answer 9

Highly pigmented keratinised stratified squamous

Question 10

Describe the histological components of the nipple

Answer 10

Core of dense irregular connective tissue mixed with bundles of SM

Sebaceous glands that end directly on the surface of the skin
Several lactiferous ducts, each serving one lobe of the breast

Question 11

Describe the changes in the epithelium of the lactiferous duct as it traverses the depth of breast

Answer 11

As the duct approaches the surface, it becomes lined by stratified squamous epithelium

Deeper it is lined by stratified cuboidal epithelium.

Deeper still the duct lining may become only one cell thick.

Question 12

What are the changes that occur in the breast during LUTEAL phase?

Answer 12

Epithelial cells increase in height
Lumina of ducts enlarge
Small amount of secretion in the duct (not enough to express)

Question 13

What are the changes that occur in the breast during FOLLICULAR phase (prior to ovulation)?

Answer 13

Cells are shorter and closer together

Question 14

What are the changes that occur in the breast during the first trimester?

Answer 14

Elongation and branching of the smaller ducts, combined with proliferation of the epithelial cells of the glands and the myoepithelial cells.

Question 15

What are the changes that occur in the breast during the second trimester?

Answer 15

Glandular tissue continues to develop with differentiation of secretory alveoli.

Also, plasma cells and lymphocytes infiltrate the nearby connective tissue.

Question 16

What are the changes that occur in the breast during the Third trimester?

Answer 16

Secretory alveoli continue to mature, with development of extensive rER.

Question 17

Which hormones drive the change to lactating breast? What are the changes?

Answer 17

Hormones: Oestrogen and Progesterone

Change: Proliferation of secretory tissue. Fibro-fatty tissue becomes sparse

Question 18

What is the composition of human milk?

Answer 18

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 19

List the different components of milk and the mechanism whereby they are secreted

Answer 19

Lipid droplets surrounded by membrane with a small amount of cytoplasm - Apocrine secretion

Proteins in milk are made in the rER, packaged in the Golgi apparatus and secreted via vesicles (v) which merge with the apical membrane to release only their contents into the duct system - Merocrine secretion

Question 20

How does the breast change after menopause?

Answer 20

Secretory cells of the TDLU’s degenerate leaving only ducts.

In the connective tissue, there are fewer fibroblasts and reduced collagen and elastic fibres.