Breasts: Structure, Function, Development and Anatomy Explained

Breasts are an essential anatomical and functional part of the human body, present in both men and women. While male breasts remain underdeveloped throughout life, female breasts undergo considerable changes, especially during puberty, pregnancy, and lactation. Understanding breast structure and function is important for anatomy students, medical learners, and anyone interested in human biology.

What Are Breasts?

Breasts (mammary glands) are specialized organs located on the chest. They consist of glandular tissue, fibrous tissue, and fatty tissue. Their primary biological function is milk production and secretion during lactation.

Both men and women have breasts, but:

• In men: breasts stay in a rudimentary state.
• In women: they grow and develop during puberty and significantly during pregnancy and breastfeeding.

Female Breast Anatomy

1. Location and Shape

In young women, breasts are hemispherical structures situated on the anterior chest wall.
They vertically extend from the 2nd to 6th rib, and horizontally from the lateral border of the sternum to the mid-axillary line.

Axillary Tail

A superolateral extension called the axillary tail of Spence moves into the armpit area and is closely associated with axillary lymph nodes.

2. Retromammary Space

A loose areolar space behind the breast allows it to glide freely over chest muscles such as:

• Pectoralis major
• Serratus anterior
• External oblique

This space separates the breast from the deep fascia.

External Features of the Breast

1. Nipple

The nipple is a small conical projection usually located at the fourth intercostal space.
It contains:

• 15–20 lactiferous duct openings
• Smooth muscle fibers that cause nipple erection or retraction

Retraction of the nipple during development may create difficulty in breastfeeding.

2. Areola

The pigmented area surrounding the nipple is called the areola.
Color changes:

• Pink/light in virgins
• Darkens during pregnancy
• Lightens after lactation

Areolar glands enlarge during pregnancy and secrete an oily substance that protects the skin during breastfeeding.

Internal Structure of the Breast

The breast is composed of three main components:

1. Glandular Tissue

• Contains 15–20 lobes
• Lobes contain smaller lobules
• Lobules contain alveoli (milk-secreting structures)

Each lobe drains into a lactiferous duct, which widens into a lactiferous sinus—a temporary milk reservoir.

2. Fibrous Tissue

Connective tissue forms ligaments of Cooper, which support the breast.
In breast cancer, these ligaments may contract, causing skin dimpling.

3. Fatty Tissue

Surrounds the glandular tissue and largely determines breast size and shape.

Breast Development (Mammogenesis)

Before Puberty

• Only ducts exist
• No alveoli
• Growth mainly due to fat accumulation

At Puberty

Estrogen stimulates:

• Branching of ducts
• Formation of terminal buds
• Development of early alveoli

During Pregnancy

Hormones involved: estrogen, progesterone, prolactin, growth hormone

Changes include:

• Formation of true milk-secreting alveoli
• Increased duct branching
• Production of colostrum (yellowish, nutrient-rich fluid)

Lactation

Begins 4–5 days after childbirth.
Myoepithelial cells contract to push milk through ducts when stimulated by the infant’s suckling.

After Lactation

• Milk stops
• Alveoli shrink
• Glandular tissue reduces

After Menopause

• Glandular tissue atrophies
• Breast becomes smaller and fatty

Male Breast

Male breasts remain rudimentary, containing:

• Basic ducts (few in number)
• Some fibrous tissue
• Fat

They usually do not develop functioning alveoli.

Blood Supply, Lymphatic Drainage and Nerves

Blood Supply

Breasts receive blood from:

• Axillary artery branches
• Internal thoracic artery
• Intercostal arteries

Venous Drainage

Veins form a network around the nipple called the venous circle, draining into:

• Axillary vein
• Internal thoracic vein

Nerve Supply

From the 4th–6th thoracic nerves, providing:

• Sensory supply
• Sympathetic fibers

Hormonal control is responsible for milk secretion, not nerves.

Conclusion

Breasts are complex organs with significant structural, functional, and hormonal importance, especially in women. From puberty to pregnancy to menopause, breast tissues undergo remarkable changes governed by hormones. Understanding the anatomy and physiology of breasts is essential for medical students, healthcare professionals, and educational content creators.

FAQs About Breast Anatomy, Structure, and Function