MAMMARY GLANDS

Development of Mammary Glands:. 
•Are a modified and highly specialized type of apocrine 

sweat glands.

•

Consist of parenchyma, which is formed from ducts, and connective 

tissue stroma.

•Parenchyma derives embryonically from surface ectoderm;

stroma arises from surrounding mesenchyme.

•

Mammary buds

begin to develop during the sixth week as solid downgrowths 

of the epidermis into the underlying mesenchyme

•These changes occur in response to an 

inductive influence from the mesenchyme.•

•Mammary buds develop as downgrowths from thickened mammary 

crests, which are thickened strips of ectoderm extending from the 

axillary to the inguinal regions 

•The mammary crests (ridges) appear during the fourth week 

but normally persist in humans only in the pectoral area, 

where the breasts develop

•

Each primary bud gives rise to several secondary mammary 

buds that develop into lactiferous ducts and their 

branches.

Development of Nipples and Areola :•During the late fetal period, the epidermis at the site of origin of the mammary gland becomes 

depressed, forming a shallow mammary pit

•

The nipples are poorly formed and depressed in newborn 

infants.

•Soon after birth, the nipples usually rise from the mammary 

pits because of proliferation of the surrounding 

connective tissue of the areola, the circular area of skin 

around the nipple.

The smooth muscle fibers of the nipple and areola 

differentiate from surrounding mesenchymal cells.

Gynecomastia

•The rudimentary lactiferous ducts in males normally 

undergo no postnatal development.

•Gynecomastia (Gr. gyne, woman + mastos, breast) refers 

to the development of the rudimentary lactiferous ducts 

in the male mammary tissue.

•

During midpuberty, approximately two thirds of boys develop 

varying degrees of hyperplasia of the breasts. This 

subareolar hyperplasia may persist for a few months to 2 

years.

•A decreased ratio of testosterone to estradiol is found

•80% of males with Klinefelter syndrome (XXY) have 

gynecomastia.

Absence of Nipples (Athelia) or Breasts (Amastia)

•Rare congenital anomalies may occur bilaterally or 

unilaterally.

•

Result from failure of development or disappearance 

of the mammary crests.

•May also result from failure of mammary buds to 

form.

•More common is hypoplasia of the breast, often 

found in association with gonadal agenesis and 

Turner syndrome

Gland Structure:

•Near the opening at the nipple, lactiferous ducts

are lined by a stratified squamous keratinized 

epithelium.

•

The lactiferous sinus and the lactiferous duct

leading to it are lined by stratified cuboidal 

epithelium,

•Smaller ducts leading to the lactiferous duct are 

lined by a simple columnar epithelium.

•Stellate myoepithelial cells located between the 

epithelium and the basal lamina wrap around the 

developing alveoli and become functional during 

pregnancy.

Mammary Gland Secretion: Milk Production:

•Prolactin is responsible for the production of milk

•Oxytocin is responsible for the milk ejection reflex.

•

Although the mammary gland is prepared to secrete milk even before 

birth, certain hormones prohibit this.

•When the placenta is detached in the adult female, prolactin from the 

anterior pituitary stimulates the production of milk, which reaches full 

capacity in a few days.

•Before that, for the first 2 or 3 days after birth, a protein-rich thick 

fluid called colostrum is secreted.

•Colostrumis a  

high-protein secretion, rich in vitamin A, sodium, and chloride, also contains 

lymphocytes and monocytes, minerals, lactalbumin, and antibodies 

(immunoglobulin A) to provide nutrition and 

passive immunity to the newborn.

•Milk, usually produced by the 4th day after parturition, is a fluid that 

contains minerals, electrolytes, carbohydrates (including lactose), 

immunoglobulins (mostly immunoglobulin A), proteins (including caseins), 

and lipids.

•Production of milk results from the stimuli of sight, touch, handling of the 

newborn, and anticipation of nursing, events that create a surge in 

prolactin release.

Summary: Mammary Glands •Modified and highly specialized type of apocrine sweat 

glands

•Consist of parenchyma, which is formed from ducts, and connective 

tissue stroma.

•Parenchyma derives embryonically from surface ectoderm; stroma 

arises from surrounding mesenchyme (inductive interactions).

•The 6-week embryo has two ventral ridge-like thickenings of 

epidermis, the mammary (milk) lines, extending from axillae to the 

inguinal area.

•The major part of each ridge disappears almost immediately, but one 

pair remains in the pectoral area and penetrates the 

mesenchyme.

•Then, 15-25 solid epithelial cords develop from each and are later 

canalized to form future lactiferous ducts.

•Mesenchyme gives rise to loose connective tissue around each duct. 

Denser connective tissue forms septa between them to divide the 

gland into lobes.

•Childhood gland structure is rudimentary and alike in both sexes.

•At puberty, glands in girls grow and undergo structural changes 

directly influenced by ovarian hormones (estrogen and 

progesterone).

•They are not fully formed and functional, however, until pregnancy 

and lactation.

•In pregnancy, terminal ends of ducts develop into hollow, sac-like 

secretory alveoli, which are lined by simple cuboidal epithelium.

•Women who give birth have highly specialized exocrine glands that 

synthesize and secrete milk. Prolactin, human placental lactogen, 

estrogen, and progesterone in the presence of prolactin from the 

anterior pituitary result in milk production; oxytocin from the 

posterior pituitary induces milk release. 

OBESITY

Obesity is defined as having an excessive amount of body fat. Obesity is more than just a cosmetic concern, though. It increases your risk of diseases and health problems such as heart disease, diabetes and high blood pressure.

Below 18.5	Underweight
18.5 — 24.9	Normal
25.0 — 29.9	Overweight
30.0 and higher	Obese
40.0 and higher	Extreme obesity

Causes:

• Inactivity. If you're not very active, you don't burn as many calories. With a sedentary lifestyle, you can easily take in more calories every day than you use through exercise and normal daily activities.
• Unhealthy diet and eating habits. Having a diet that's high in calories, eating fast food, skipping breakfast, eating most of your calories at night, drinking high-calorie beverages and eating oversized portions all contribute to weight gain.
• Pregnancy. During pregnancy, a woman's weight necessarily increases. Some women find this weight difficult to lose after the baby is born. This weight gain may contribute to the development of obesity in women.

  Treatments:

  • Dietary changes
  • Exercise and activity
  • Behavior change
  • Prescription weight-loss medications
  • Weight-loss surgery

STOMACH

The stomach is divided into four major anatomic regions: the cardia, fundus, body, and antrum. The cardia and antrum are lined mainly by mucin-secreting foveolar cells that form small glands. The antral glands are similar but also contain endocrine cells, such as G cells, that release gastrin to stimulate luminal acid secretion by parietal cells within the gastric fundus and body. The well-developed glands of the body and fundus also contain chief cells that produce and secrete digestive enzymes such as pepsin.

PANCREATITIS

Pancreatitis:
 is inflammation in the pancreas associated with injury to the exocrine parenchyma.


Acute pancreatitis is reversible pancreatic parenchymal injury associated with inflammation. Acute pancreatitis is relatively common, with an annual incidence rate in Western countries of 10 to 20 cases per 100,000 people.
common causes of acute pancreatitis include:
•    Obstruction of the pancreatic duct system
•    Medications. More than 85 drugs have been implicated. These include furosemide, azathioprine, 2′,3′-dideoxyinosine, estrogens
•    Infections, including mumps,
•    Ischemic injury from shock, vascular thrombosis, embolism, and vasculitis.
•    Trauma. Both blunt abdominal trauma and iatrogenic injury during surgery or endoscopic retrograde cholangiopancreatography.

CHRONIC PANCREATITIS

Chronic pancreatitis is defined as inflammation of the pancreas with irreversible destruction of exocrine parenchyma, fibrosis, and, in the late stages, the destruction of endocrine parenchyma.
causes of chronic pancreatitis include:
•    Long-standing obstruction of the pancreatic duct by pseudocysts, calculi, trauma, neoplasms, or pancreas divisum. There is often dilation of the pancreatic duct
•    Hereditary pancreatitis, which is caused by germline mutations in PRSS1

THYMUS

The thymus is embryologically derived from the third and, inconstantly, the fourth pair of pharyngeal pouches. At birth it weighs 10 to 35 gm. It grows until puberty, when it achieves a maximum weight of 20 to 50 gm, and thereafter undergoes progressive involution to little more than 5 to 15 gm in the elderly. The thymus can also involute in children and young adults in response to severe illness and HIV infection.


Macrophages, dendritic cells, a minor population of B lymphocytes, rare neutrophils and eosinophils, and scattered myoid (muscle-like) cells are also found within the thymus. The myoid cells are of particular interest because of the suspicion that they play some role in the development of myasthenia gravis, a musculoskeletal disorder of immune origin.

SPLEEN

The spleen is an ingeniously designed filter for the blood and a site of immune responses to blood-borne antigens. Normally in the adult it weighs about 150 gm and is enclosed within a thin, glistening, slate-gray connective tissue capsule. Its cut surface reveals extensive red pulp dotted with gray specks, which are the white pulp follicles. These consist of an artery with an eccentric collar of T lymphocytes, the so-called periarteriolar lymphatic sheath. At intervals this sheath expands to form lymphoid nodules composed mainly of B lymphocytes, which are capable of developing into germinal centers identical to those seen in lymph nodes in response to antigenic stimulation


The spleen has four functions that impact disease states:

	1.	Phagocytosis of blood cells and particulate matter. As will be discussed under the hemolytic anemias.. red cells undergo extreme deformation during passage from the cords into the sinusoids. In conditions in which red cell elasticity is decreased, red cells become trapped in the cords and are more readily phagocytosed by macrophages. Splenic macrophages are also responsible for “pitting” of red cells, the process by which inclusions such as Heinz bodies and Howell-Jolly bodies are excised, and for the removal of particles, such as bacteria, from the blood.
	2.	Antibody production. Dendritic cells in the periarterial lymphatic sheath trap antigens and present them to T lymphocytes. T- and B-cell interaction at the edges of white pulp follicles leads to the generation of antibody-secreting plasma cells, which are found mainly within the sinuses of the red pulp. The spleen seems to be an important source of antibodies directed against platelets and red cells in immune thrombocytopenia purpura and immunohemolytic anemias, both discussed in Chapter 14 .
	3.	Hematopoiesis. Splenic hematopoiesis normally ceases before birth, but can be reactivated in severe anemia. As we have seen, the spleen is also a prominent site of extramedullary hematopoiesis in myeloproliferative disorders, such as chronic myeloid leukemia.
	4.	Sequestration of formed blood elements. The normal spleen contains only about 30 to 40 mL of red cells, but this volume increases greatly with splenomegaly. The normal spleen also harbors approximately 30% to 40% of the total platelet mass in the body. With splenomegaly up to 80% to 90% of the total platelet mass can be sequestered in the interstices of the red pulp, producing thrombocytopenia. Similarly, the enlarged spleen can trap white cells and thereby induce leukopenia.