At the sides of the chest, the breast tissue can extend into the axilla (armpit), and can reach as far to the back as the latissimus dorsi muscle, extending from the lower back to the humerus bone (the bone of the upper arm). As a mammary gland, the breast is composed of differing layers of tissue, predominantly two types: adipose tissue; and glandular tissue, which affects the lactation functions of the breasts. : 115 Morphologically the breast is tear-shaped. The superficial tissue layer (superficial fascia) is separated from the skin by 0.5–2.5 cm of subcutaneous fat (adipose tissue). The suspensory Coopers ligaments are fibrous-tissue prolongations that radiate from the superficial fascia to the skin envelope. The female adult breast contains 14–18 irregular lactiferous lobes that converge at the nipple. The 2.0–4.5 mm milk ducts are immediately surrounded with dense connective tissue that support the glands. Milk exits the breast through the nipple, which is surrounded by a pigmented area of skin called the areola. The size of the areola can vary widely among women. The areola contains modified sweat glands known as Montgomerys glands. These glands secrete oily fluid that lubricate and protect the nipple during breastfeeding. Volatile compounds in these secretions may also serve as an olfactory stimulus for the newborns appetite.The dimensions and weight of the breast vary widely among women. A small-to-medium-sized breast weighs 500 grams (1.1 pounds) or less, and a large breast can weigh approximately 750 to 1,000 grams (1.7 to 2.2 pounds) or more.
Dihydropteridine reductase deficiency (DHPRD) is a genetic disorder affecting the tetrahydrobiopterin (BH4) synthesis pathway, inherited in the autosomal recessive pattern. It is one of the six known disorders causing tetrahydrobiopterin deficiency, and occurs in patients with mutations of the QDPR gene. The disease presents with such symptoms as elevated levels of phenylalanine (hyperphenylalaninemia), microcephaly, hypotonus, mental retardation and epileptic seizures. Diagnostics
Besides the traditional analysis of symptoms and investigation of phenylalanine concentrations, patients suspected for DHPRD undergo the assessment of enzymatic activity using the dried blood spot method - this permits to distinguish DHPR deficiency from the other forms of BH4 deficiency. Treatment
Patients are prescribed a phenylalanine-reduced diet, with regular monitoring of phenylalanine levels in the blood. Besides the diet, a patient may be prescribed sapropterin, a synthetic analogue of tetrahydrobiopterin. In order to restore dopamine levels in the central nervous system, patients are given L-dopa in conjunction with an inhibitor of aromatic amino acid decarboxylase that acts outside the nervous system, so as to promote the transformation of L-dopa into dopamine inside the central nervous system, and thus to improve the efficiency of the treatment. Since the insufficient levels of BH4 inhibit the transformation of tryptophan into 5-hydroxytryptophan in a reaction in which BH4 serves as a cofactor of the enzyme tryptophane hydroxylase 2, patients suffer from a lack of serotonin in their CNS. In order to correct this deficiency, they are given 5-hydroxytryptophan. In patients with DHPR deficiency, a pronounced lack of 5-methyltetrahydrofolate (5-MTHF) is observed in the central nervous system.