Mammary Gland.

Mammary Gland.

Introduction.

Mammary gland(Latin means breast) form an important female accessory reproductive organ, its the most important content of the pectoral region in the superficial facial. The anatomy of breast is of great importance and it have to be studied in details.

Situation.

Breast is situated in the superficial facial of the pectoral region and it's present in both sexes(male and female) but rudimentary in male and prematured females and its well developed in a matured female where it provides food in form of milk to the neonates and infants.

It's divided into four quadrants; upperlateral, uppermedial, lowerlateral, and lowermedial quadrant. An extension of the upperlateral quadrant called axillary tail of Spence reached anterior part of axilla through an opening called foramen of langer.

Extent

Vertically; from 2nd to 6th rib.

Horizontally; from midaxillary line to the lateral border of sternum.

Deep relations

1. Breast lies on the pectoral facia covering pectoralis major.

2. It's separated from the pectoral facia by a loose areolar tissue called retromammary space.

3. Still deeper some muscles lie underneath the pectoralis major.

Structure of breast

For a more convenient study the breast is divided into three major parts; the skin, parenchyma and stroma.

The Skin

It covers the breast and it presents some structures as follows;

1. A conical projection called the nipple which lies at the level of 4 intercostal space just below the center of the breast. It's perforated by 15-20 lactiferous ducts and contains some modified sweat and sebaceous glands, longitudinal and round muscles that stiffen or flatten it and it's rich in nerve supply by many sensory nerve endings.

2. Base of the nipple is pigmented and formed a circular area called the areola.

The areola contains a modified sebaceous gland and it's raised during pregnancy and lactation to form so called tubercles of Montgomery. The skin of areola contains some small modified sweat gland apart from sebaceous gland and an oily secretion of these glands prevents cracking of the nipple and areola during lactation, also the skin is devoid of hair and therefore there is no fat subjacent to it.

Parenchyma

This is a tubulo-alveolar gland that secrets milk. It's formed by about 15-20 lobes that drain into the lactiferous ducts which converge and opened on nipple. Near the termination of the ducts there's a dilation called the sinuses where stored milk is seen.

The alveolar epithelium is cuboidal in resting state and columner during lactation and may appear cuboidal when distended but more larger than the that in resting state. The movement of milk is facilitated by myoepitheliocytes present in both alveolar ducts epithelia between the basement membrane and the epithelia.

Stroma

This formed a supportive framework for the the breast and made up of two parts; fibrous and fatty tissues.

Fibrous tissue part formed by septa that anchored the skin and gland to the pectoral facia.

Fatty tissue part formed the bulk of the breast and it's distributed everywhere except beneath the areola and nipple.

Blood supply

1. Superior thoracic artery- a branch of first part of the axillary artery.

2. Pectoral branch of thoracoacromial artery- a branch of the 2nd part of the axillary artery.

3. Lateral thoracic artery- a branch of the 2nd part of the axillary artery.

4. Lateral branches of posterior intercostal arteries.

5. Internal thoracic arteries through perforating branches.

These arteries are essentially enlarged in females for supplying the breast.


Nerve supply
The breast is inervated by anterior and lateral cutaneous branches of 4th to 6th intercostal nerves. The nerve supply sensory fibres to the skin and autonomic fibres to the smooth muscles, and don't control the secretion of milk as this is controlled by a hormone called prolactin.

Lymphatic drainage
This is of great importance to the medical students and surgeons because many form carcinoma of breast spread to other regional lymph nodes through lymphatics and this can be studied under two heads; lymph nodes and lymphatic vessels.

1.Lymph nodes; these are of different groups as shown in the diagram below;

2. Lymph  vessels:
> From  plexuses  inside  the  gland  between  the  lobules  [interlobular plexus]  and  beneath  the  areola  [subareolar  plexuses].
> These vessels  communicate  with:     A plexus  in  the  fascia  of  pectoralis  major  muscle.
> Lymph vessels  of  the  opposite  mammary  gland.
> A plexus  on  the  upper  part  of  the  rectus  sheath  of  the  abdomen.
> Vessels  that  perforate  the  intercostal  spaces  to  reach  the parasternal  nodes.

Lymph nodes: The  efferent  vessels  drain  into  the  following  nodes;
» Axillary  nodes:  [receive  70%  of  the  vessels].  The  1st  groups  to receive  the  lymphatics  are  the  pectoral  and  apical nodes.
» Parasternal  nodes:  [receive  25%  of  the  vessels]  along  the  internal thoracic  artery.
» Lymph nodes of  the  opposite  axilla.


APPLIED  ANATOMY: As  the  lactiferous  ducts  radiate  from  the  nipple,  incision  of  the  gland  should be  made  in  a  radial direction  to  avoid  cutting  across  the  ducts  and  lobules. Malignancy  in  the  gland  is  common.  Contraction  of  the  suspensory ligaments  by  cancer  will  pull  on  the  skin  over  the  gland  [peau  d’orange]  and retract  the  nipple. Infiltration  of  the  pectoralis  major  leads  to  fixation  of  the  tumour.