Logan Steele
The breasts lie over the pectoralis muscle, also known as the 'pec' chest muscle, which is atop the rib cage. The pectoralis major muscle forms the base of the breast, extending from the second to sixth rib early in life, and may extend below the sixth rib as the breast matures and sags. The breast is anchored to the pectoralis major by suspensory ligaments, which allow for movement in the breast. The pectoralis muscle is frequently used in reconstructive plastic surgery as it can provide good muscle coverage for a breast implant.
| Characteristics | Values |
|---|---|
| Location of breast muscles | The breast lies over the pectoralis muscle and the uppermost portion of the rectus abdominis muscle between the second and sixth ribs. |
| Base of the breast | The pectoralis major muscle |
| Blood supply to the breast | Internal mammary artery |
| Lymph nodes | Located in the axilla (underarm), infraclavicular (under the collarbone), supraclavicular (above the collarbone), and internal mammary (beneath the pectoralis muscle) |
| Muscle tissue | Present in the nipples and around the lobules |
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What You'll Learn
- The pectoralis major muscle forms the base of the breast
- The breast is anchored to the pectoralis major by suspensory ligaments
- The axillary tail of Spence is a tail of breast tissue that extends into the underarm
- The nipple contains muscle fibres that contract to make it erect
- The breast is bordered by the external oblique muscle
The pectoralis major muscle forms the base of the breast
The pectoralis major is the largest muscle of the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. The pectoralis major is the most superficial muscle in the pectoral region. It is also referred to as "pecs", "pectoral muscle", or "chest muscle".
The pectoralis major has its origin in the anterior surface of the medial half of the clavicle, the anterior surface of the sternum, the first 7 costal cartilages, the sternal end of the sixth rib, and the aponeurosis of the external oblique of the anterior abdominal wall. It has two heads, the clavicular and the sternocostal, which reference their area of origin. The sternocostal head is described as having between 2 to 7 distinct segments. The pectoralis major is highly vascularised via the thoracoacromial artery, reducing the chances of necrosis in flap formation.
The primary functions of the pectoralis major are flexion, adduction, and internal rotation of the humerus. It is also responsible for keeping the arm attached to the trunk of the body. The clavicular part of the muscle is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. The sternocostal part is antagonistic to the clavicular part, contributing to the downward and forward movement of the arm and inward rotation when accompanied by adduction.
The pectoralis major is also an accessory muscle of inspiration, assisting in forced inspiration when the diaphragm and intercostal muscles are insufficient for proper breathing. It also assists in elevating the thorax.
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The breast is anchored to the pectoralis major by suspensory ligaments
The breast is a complex structure with many components, including blood vessels, lymph vessels, lobes, and nipples. While breasts are present in both males and females, they are more prominent in females following puberty.
The pectoralis major is a large, fan-shaped muscle that starts at the lateral sternum and clavicle and attaches to the humeral head. The breast is positioned over the pectoralis muscle and the uppermost section of the rectus abdominis muscle, between the second and sixth ribs. The breast is anchored to the pectoralis major by suspensory ligaments known as Cooper's ligaments. These ligaments traverse the breast tissue, extending from the dermis of the skin to the pectoralis fascia.
Cooper's ligaments are not taut, allowing the breasts to maintain their natural mobility. However, with age, these ligaments lose tension, leading to breast ptosis or sagging. The pectoralis muscle is often utilized in reconstructive plastic surgery as it provides good coverage for breast implants.
The base of the breast lies on the pectoral fascia, a thin layer of connective tissue associated with the pectoralis major muscle. The suspensory ligaments attach to and secure the breast to the dermis and this underlying pectoral fascia. The fibrous stroma, which is the connective tissue surrounding the breasts, condenses to form these suspensory ligaments.
The breast can be divided into two regions: the circular body, which is the largest and most prominent part, and the axillary tail, which is a smaller part that runs along the inferior lateral edge of the pectoralis major towards the axillary fossa. The nipple, located at the centre of the breast, is composed of smooth muscle fibres. The areola, a circular area of skin that surrounds the nipple, contains sebaceous glands that secrete an oily substance to lubricate and protect the nipple during breastfeeding.
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The axillary tail of Spence is a tail of breast tissue that extends into the underarm
The axillary tail of Spence, also known as Spence's tail, the axillary process, or the axillary tail, is a historical concept in anatomy. It refers to a supposed extension of the tissue of the upper outer quadrant of the breast into the axilla or underarm area. The concept was first described by Scottish surgeon James Spence, who served as President of the Royal College of Surgeons in Edinburgh in the 19th century.
Spence's original description referred to "an undefined tail-like projection creeping up from the breast towards the axilla." However, he did not provide any anatomical diagrams or detailed descriptions of the structure. Spence's peers interpreted his remarks and published varying accounts, leading to confusion and a lack of consensus on the existence and nature of the axillary tail.
Despite the widespread adoption of the concept in medical literature and education, recent studies have challenged the existence of the axillary tail of Spence. Researchers have conducted pinch tests and topographic mapping on patients and found no evidence of a continuous superolateral tail of fat extending from the breast to the axilla. Instead, they identified distinct focal fat mounds, suggesting that the axillary mound is separate from the primary breast.
It is important to note that while the axillary tail of Spence as a continuous structure may not exist, there is a separate axillary breast mound. This axillary mound is more likely to contain accessory ductal tissue, which can be a site of breast cancer formation. Therefore, while the specific concept of the axillary tail of Spence is questionable, the presence of breast tissue in the axillary region and its clinical significance remain relevant in the fields of surgery, oncology, and anatomy.
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The nipple contains muscle fibres that contract to make it erect
The nipple is the area at the centre of the areola with an opening to release milk. The areola is the circular darker-coloured area of skin surrounding the nipple. The nipple contains muscle fibres, and when these contract, the nipple becomes erect or pointed outward. This is due to the contraction of smooth muscle under the control of the autonomic nervous system. Nipple erection is a product of the pilomotor reflex, which causes goose bumps.
The nipple-areolar complex is covered by keratinizing squamous epithelium. The dermis of the nipple and the areola contains many multibranched, free nerve fibre endings. The areola and nipple are rich in arteriovenous anastomoses, which enhance the process of nipple erection. Local venostasis and hyperemia occur during nipple erection. The nipple contains bands of smooth muscle that run parallel to the major lactiferous ducts and circumferentially towards the base. The smooth muscle acts as erectile tissue and is involved in eliminating milk from the nipple.
The human nipple has numerous ostia, while rodent nipples have only a single outlet. Male rodents lack nipples. Bundles of smooth muscle fibres are arranged radially and circumferentially in the dense connective tissue and longitudinally along the lactiferous ducts that extend up into the nipple. These muscle fibres are responsible for the erection of the nipple in response to various stimuli. Nipple erection can occur due to tactile, thermal, or sexual stimulation.
Nipple stimulation may produce sexual excitement, and erect nipples can indicate an individual's sexual arousal. Studies have shown that nipple erection can significantly impact people's perceptions of and behaviour towards women. For example, men are more willing to help women with erect nipples, possibly because they view them as more sexually attractive and approachable. Nipple stimulation or breast stimulation may be performed as part of sexual activity and can be used to initiate and enhance sexual arousal.
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The breast is bordered by the external oblique muscle
The breast is a complex organ with a unique anatomy that varies between individuals. It is important to understand the anatomy of the breast to comprehend the disorders that affect this organ, such as breast cancer, and to plan surgical procedures.
The breast is bordered by several muscles, including the external oblique muscle. The external oblique muscle is a fan-shaped muscle found on the anterolateral aspect of the thoracic wall. It is situated on the lateral and anterior parts of the abdomen and is the largest and outermost of the three flat abdominal muscles in this region. The muscle is thin and irregularly quadrilateral in shape, and in most humans, it is not visible due to subcutaneous fat deposits and its small size.
The external oblique muscle originates from the ribs, specifically the fifth to twelfth ribs (lower eight ribs), and its digitations are arranged in an oblique line. The muscle has a segmental blood supply that originates from the inferior intercostal vessels. The external oblique functions to pull the chest downwards and compress the abdominal cavity, increasing intra-abdominal pressure. It also performs ipsilateral side-bending and contralateral rotation.
In relation to the breast, the external oblique muscle borders the inferolateral wall of the breast. The base of the breast sits over this muscle and the serratus anterior muscle. The pectoralis major muscle forms the base of the breast and is anchored to the breast by the suspensory ligaments of Cooper, which allow for natural mobility. The pectoralis major muscle receives blood supply from branches of the internal mammary and thoracoacromial arteries.
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Frequently asked questions
The breast lies over the pectoralis muscle and the uppermost portion of the rectus abdominis muscle, between the second and sixth ribs.
The pectoralis major is a broad, fan-like muscle that forms the base of the breast. It originates from the lateral sternum and clavicle and inserts at the humeral head.
Yes, the nipple contains muscle fibres. When these muscle fibres contract, the nipple becomes erect.
The axilla is the area under the armpit. The main regional nodes of the breast are in the axilla, but they also include those under the collarbone and above the collarbone.
The pectoralis muscle is frequently used in reconstructive plastic surgery as it can provide good muscle coverage for a breast implant.
