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Mammary Glands: Structure, Types, Diagram, Functions, Breast Cancer, Practice Problems and FAQs

What comes to mind when you hear the word ‘mammals’? The first thing that we are reminded of is that mammals give birth to their young ones and feed and nurture them till they grow up. Where do you think ‘mammals’ gets their name from? They get it from the presence of mammary glands in their body which is unique to the members of class Mammalia.
We all have seen women around us breast-feeding their children since the time of birth of the child to an age of around 2-3 years. Do you ever wonder how a human mother produces milk to feed her child? This is where the mammary glands present in the breast of mammalian females, including humans, come into play. Come let us learn more about these unique glands present in human females.

Table of Contents:

Mammary Glands

All female mammals have a characteristic feature and that is the presence of a functional mammary gland. These glands help to nourish the young ones by feeding them the milk produced by the mammary glands in the lactating mothers. 

Each breast is a variable-sized hemispheric projection situated anterior to the pectoralis major muscles on the front wall of the chest. The pectoralis muscle, which runs from shoulder to breast bone, is a flat muscle in the chest. 

pectoralis-major-muscle

Development of Mammary Glands

Mammary glands are under developed stage until puberty. Once the female attains puberty, they begin to develop under the influence of oestrogen and progesterone hormones. 

developmoent-of-mammary-glands-with-age

mammary-gland-development

External Structure of Breast

Externally, each breast has a pigmented projection which is referred to as the nipple. Nipple possesses a set of closely spaced openings of ducts called lactiferous ducts. These are the ducts from where milk emerges. Surrounding the nipple, there is a circular area of pigmented skin which is termed as the areola. It is a rough surface and contains numerous sebaceous gland. 

external structure of brest

Internal Structure of Breast

The breast is supported by strands of connective tissue known as the suspensory ligaments of the breast (Cooper's ligaments). The suspensory ligaments loosen with age or due to excessive strain caused due to long-term jogging or high impact aerobics. 
A mammary gland is a modified sudoriferous (sweat) gland that produces milk, and is found within each breast. The mammary gland of each breast has glandular tissue composed of 15-20 mammary lobes or mammary compartments that are separated by variable amounts of adipose tissue. 
Each mammary lobe consists of clusters of milk secreting cells known as alveoli which secrete milk and store it in the cavities (lumens) of the clusters or alveoli. Alveoli are embedded in the fibrous connective tissue. The fibrous connective tissue supports alveoli and ducts. The fatty adipose tissue is present between the lobes that cover the surface of mammary glands. 

internal structure of brest
Each alveoli opens into mammary tubules. A mammary duct is formed when tubules emerging from each lobe join together. A mammary ampulla is formed when several mammary ducts merge. Mammary ampulla is further connected to the lactiferous duct through which milk is sucked out. 

internal structure of brest

Types of Mammary Glands

There are two types of mammary glands that are described below:

  • Simple mammary gland: This is a simple type of gland that contains many milk secreting tissue leading to the single lactiferous duct.
  • Complex mammary gland: This is a complex type of gland that contains many simple mammary glands. These glands serve only one nipple. In humans, two complex mammary glands are present, one in each breast. Each complex mammary gland is composed of 10-20 simple glands.

Functions of Breast

The breast performs the following functions:

  • Breast is primarily involved in the secretion and ejection of milk. This phenomenon is called lactation and is associated with pregnancy and childbirth.
  • The anterior lobe of the pituitary gland secretes prolactin, which stimulates milk production.
  • The posterior lobe of the pituitary gland secretes oxytocin, which stimulates milk ejection.
     

    function of breast

Mammary Glands in Males

The mammary glands in males are rudimentary and not well-developed like in females. They do not play any role in nursing the new-borns. Sometimes hyposecretion of androgens or hypersecretion of estrogens in males can cause the male mammary glands to swell up. This condition is known as gynaecomastia.

Breast Cancer

Breast cancer is a type of cancer that initiates in the breast. At a given time, it can develop in both breasts. When breast cells start to divide uncontrollably, then the condition is known as breast cancer. It is the most common type of cancer diagnosed in females. It can start from different parts of the breast. Breast cancer spreads in the body when the cancer cells reach the blood or lymph. These cancer cells are carried to other parts of the body through these connective tissues. The two common types of breast cancer are:

  • Invasive ductal carcinoma: This type of cancer originates in the ducts of the mammary gland and then spreads outside the ducts into different parts of the breast. It can also spread to other parts of the body.
  • Invasive lobular carcinoma: This type of cancer originates in the lobules and then spreads to other parts of the breast. These cancer cells can also spread to other parts of the body.

Symptoms of Breast Cancer

The commonly seen symptoms of breast cancer are enlisted below:

  • The breast size starts increasing which feels different from the surrounding tissue.
  • The size, shape and appearance of the breast changes.
  • The skin over the breast starts dimpling, i.e. dimple formation starts.
  • A newly inverted nipple is formed in some cases.
  • The skin over the breast gives a reddish appearance.
  • The pigmented area surrounding the nipple starts peeling, scaling or crusting.

Causes of Breast Cancer

The causes of breast cancer can be hormonal, environmental or lifestyle based. In some cases, it occurs because of the complex interaction between the genetic makeup and environment. Breast cancer can also be inherited in which cancers are linked to gene mutations that are passed through generations.

Practice Problems of Mammary Glands

Question 1. The alveoli of the mammary gland opens into which of the following structures:

a. Mammary ampulla
b. Mammary tubules
c. Mammary lobes
d. Mammary duct

Solution: The cells of alveoli secrete milk that are stored in the cavities of alveoli. Each alveoli opens into mammary tubules. The tubules are further joined to form the mammary duct. Hence, the correct option is b.

Question 2. Under the influence of which hormone(s), mammary glands develop?

a. Oestrogen
b. Progesterone
c. Oxytocin
d. Both a and b

Solution: Until puberty, the mammary glands are not fully developed. When a female reaches puberty, oestrogen and progesterone hormones begin to influence its development. Hence, the correct option is d.

Question 3. Study the given diagram and choose the option which represents the correct labelling.

1

a.  A - mammary ampulla, B - mammary tubule, C - lactiferous duct, D - mammary duct
b.  A - mammary tubule, B - mammary duct, C - mammary ampulla, D - lactiferous duct
c.  A - mammary duct, B - mammary tubule, C - lactiferous duct, D - mammary ampulla
d.  A - lactiferous duct, B - mammary duct, C - mammary tubule, D - mammary ampulla

Solution: Each alveoli opens into mammary tubules (A). A mammary duct (B) is formed when tubules emerging from each lobe join together. A mammary ampulla (C) is formed when several mammary ducts merge which is further connected to the lactiferous duct (D) through which milk is sucked out. 
Thus, the correct option is b.

internal structure of brest

Frequently Asked Questions of Mammary Glands

Question 1. What are the four common symptoms of breast cancer?

Solution: The four common symptoms of breast cancer are:

  • The size, shape and appearance of the breast changes due to the abnormal growth of cells.
  • A newly inverted nipple is formed in some cases.
  • The skin over the breast gives a reddish appearance.
  • The pigmented area surrounding the nipple starts peeling, scaling or crusting.

Question 2. In humans which type of mammary glands are present?

Solution: In humans, complex mammary glands are present. This type of gland contains many simple mammary glands that serve only one nipple.

Question 3. What are the three common functions of the breast?

Solution: The common functions of the breast are enlisted below:

  • Breast is involved in the lactation during pregnancy.
  • The breast cells produce milk under the stimulation of prolactin hormone.
  • The breast cells secrete milk under the influence of oxytocin hormone.

Question 4. What are the common causes of breast cancer?

Solution: Breast cancer can be caused by hormonal or environmental reasons. Gene mutations linked to cancer cells can also be inherited from ancestors.

Question 5. How do breasts produce milk?

Solution: A mammary gland is a modified sweat gland that produces milk, and is found within each breast. The mammary gland of each breast has glandular tissue composed of 15-20 mammary lobes or mammary compartments that are separated by variable amounts of adipose tissue. 
Each mammary lobe consists of clusters of milk secreting cells known as alveoli which secrete milk and store it in the cavities (lumens) of the clusters or alveoli.
Each alveoli opens into mammary tubules. A mammary duct is formed when tubules emerging from each lobe join together. A mammary ampulla is formed when several mammary ducts merge. Mammary ampulla is further connected to the lactiferous duct through which milk is sucked out.

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