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Anatomy & Physiology

Mammary Glands (Breast)

The breast or mammary gland is a highly efficient organ mainly used to produce milk and is a mass of

glandular, fatty, fibrous tissues. Mammary glands are exocrine glands that are enlarged and developmentally are

modified sweat glands that are actually part of the skin. They are also classified as tubualveolar glands and are

located in the breast lying on the top of the pectoralis major muscles. These glands are present in males and

females; however, they normally function in the latter gender only.

Function

The biological role of the mammary glands is to produce milk to nourish a newborn baby and to pass

antibodies needed for babys protection against infections (passive immunity) while the immature immune is initiating

its function.

Breast Anatomy

The breast is internally composed of the following parts:

Lobes and Lobules

Internally, the mammary gland is composed of 15-25 lobes that radiates around the nipple. Each lobe

consists of about 20-40 lobules, a smaller milk duct that contains 10-100 supporting alveoli.

Glandular tissue

Glandular tissues are responsible for milk production and transportation which is composed of:

1. Alveoli epithelial grape-like cluster of cells where milk is produced.

2. Ductules branch-like tubules extending from the clusters of alveoli and empties to larger ducts called lactiferous

ducts.

3. Lactiferous ducts widen underneath the areola and nipple to become lactiferous sinuses.

4. Lactiferous sinuses collect milk from lactiferous ducts and narrows to an opening in the nipple (nipple pore).

Connective tissue

Connective tissue supports the breast. Coopers ligaments are fibrous bands that attach the breast to the

chest wall and keep the breast from sagging.

Blood nourishes breast tissue and supplies the nutrients to the breast needed for milk production.

Nerves make the breast sensitive to touch, hence allowing the babys suck to stimulate the release of hormonesthat trigger the let-down or milk ejection reflex (oxytocin) and the production of milk (prolactin).

Lymph nodes removes waste products

Adipose tissue(fat) protects the breast from injury.

The breast is externally composed of the following parts:

Areola pigmented area at the center of each breast.

Nipple protruding area at the center of each breast.

Physiology

The function of producing milk is regulated by hormones. Stimulation of the female sex hormone,

estrogen, causes the development of glandular tissue in the female breast during puberty. Increase estrogen levels

during pregnancy causes the breast size to increase in size through the accumulation of adipose tissues.

Presence of progesterone stimulates the growth and maturation of the duct system. During pregnancy

levels of estrogen and progesterone rises (levels are needed to sustain pregnancy) that further enhances the

development of the mammary glands. This is the main reason why pregnant women has larger and more enhanced

breast.

Another hormone important for the implementation of mammary gland function is the presence of

prolactin and oxytocin. Without these hormones, milk will not be produced and ejected out of the breast. Prolactin

from the anterior pituitary gland stimulates the production of milk in the glandular tissues while oxytocin causes the

ejection of milk from the glands.

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Pathophysiology

Predisposing Factors

-heredity

-personal factors

-age

Risk Factors

-alcoholics

-oral contraceptives

-not having children( >35y.o)

-early exposure to estrogen

Mutations occur in DNA of

breast cells

Exposure of cells to

p53, BRCA1 and BRCA2

Uncontrolled divisions of cells

Failure of protective pathways

Increased cell proliferation

Stages:

Stage 0noninvasive carcinomas (LCIS or DCIS). Cancer cells have not invaded the surrounding breast tissue.

Stage Ithe tumor is no more than 2 cm in size and cancer cells have not spread beyond the breast.

Stage IIeither the tumor has spread to the lymph nodes under the arms but the tumor is less than 2 cmin size, or the tumor has not spread to the lymph nodes under the arms but is greater than 5 cm in size, or the tumor

is between 2 and 5 cm and may or may not have spread to the nodes.

Stage IIIthe tumor is greater than 5 cm in size and has spread to the lymph nodes under the arms.

Stage IVthe cancer has spread to other parts of the body (metastatic cancer).

Signs & Symptoms

y swelling of all or part of the breast

y skin irritation or dimpling

y breast pain

y nipple pain or the nipple turning inward

y redness, scaliness, or thickening of the nipple or breast skin

y a nipple discharge other than breast milk

y a lump in the underarm area

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Breast cancer, like other cancers, occurs because of an interaction between the environment and a

defective gene. Predisposing factors include heredity(which includes family history of developing ovarian or breast

cancers),personal factors( early onset of period) and women of increasing age. Risk factors of the said disease are

women who are alcoholics, dependence on oral contraceptives, not having children and having early exposure to

estrogen .Normal cells divide as many times as needed and stop. They attach to other cells and stay in place in

tissues. Cells become cancerous when mutations destroy their ability to stop dividing, to attach to other cells and to

stay where they belong. When cells divide, their DNA is normally copied with many mistakes. Error-correcting

proteins fix those mistakes. The mutations known to cause cancer, such as p53, BRCA1 and BRCA2, occur in the

error-correcting mechanisms. These mutations are either inherited or acquired after birth. Presumably, they allow the

other mutations, which allow uncontrolled division, lack of attachment, and metastasis to distant organs.

Normal cells will commit cell suicide (apoptosis) when they are no longer needed. Until then, they are

protected from cell suicide by several protein clusters and pathways. One of the protective pathways is

the PI3K/AKT pathway. Sometimes the genes along these protective pathways are mutated in a way that turns them

permanently "on", rendering the cell incapable of committing suicide when it is no longer needed. This is one of the

steps that causes cancer in combination with other mutations. Normally, the PTEN protein turns off the PI3K/AKT

pathway when the cell is ready for cell suicide. In some breast cancers, the gene for the PTEN protein is mutated, so

the PI3K/AKT pathway is stuck in the "on" position, and the cancer cell does not commit suicide.

Mutations that can lead to breast cancer have been experimentally linked to estrogen exposure. Failure

of immune surveillance, the removal of malignant cells throughout one's life by the immune system.

Abnormal growth factor signaling in the interaction between stromal cells and epithelial cells can facilitate

malignant cell growth. In breast adipose tissue, overexpression of leptin leads to increased cell proliferation and

cancer. Staging of breast cancer are the following:Stage 0noninvasive carcinomas (LCIS or DCIS). Cancer cells

have not invaded the surrounding breast tissue.Stage Ithe tumor is no more than 2 cm in size and cancer cells

have not spread beyond the breast.Stage II

either the tumor has spread to the lymph nodes under the arms but the

tumor is less than 2 cm in size, or the tumor has not spread to the lymph nodes under the arms but is greater than 5

cm in size, or the tumor is between 2 and 5 cm and may or may not have spread to the nodes.Stage IIIthe tumor is

greater than 5 cm in size and has spread to the lymph nodes under the arms.Stage IVthe cancer has spread to other

parts of the body (metastatic cancer).