Week 5 Flashcards
What is the difference in mammary glands in males and females?
In males, mammary glands are rudimentary and functionless whereas in females, mammary glands are accessory to reproduction.
Describe the structure of the breast and the path taken by milk during lactation?
Breast is composed of 15-20 lobes divided by adipose tissue. These lobes contain alveoli which is the site of milk production and secretion. The milk then drain into the lactiferous ducts, which themselves drain into the lactiferous sinus, which is a small reservoir under the areola; which converges, and opens onto the nipple.
What is an alveolus in the context of the life cycle?
The site in which milk is produced in the breast.
How do the alveoli push milk out into the lactiferous duct?
They do that through the use of surrounding myoepithelial cells which contract to push the milk out into the lactiferous duct.
Describe hormone levels (pre-birth, after birth) and describe why these levels fluctuate in the way they do? Progesterone, estradiol, hPL, prolactin?
Progesterone, estradiol and human placental lactogen all rise significantly during pregnancy but fall very quickly after the delivery of the placenta. Prolactin, however, does not fall as it is necessary to complete the process of lactation for the newborn baby.
Describe the development of ducts and alveoli throughout the women’s development as well as the factors causing these changes?
At birth/pre-puberty: The ducts and alveoli have a very rudimentary structure, and are heavily underdeveloped
During puberty: The effect of progesterone and estrogen during puberty cause the development of the ducts as well as the alveoli. Oestrogen is mostly responsible for the development of the ducts while Progesterone is mostly responsible for the development of the alveoli.
During pregnancy: The effects of hyper increased hormonal levels of oestrogen and progesterone as well as prolactin and hPL cause an exponential proliferation of the ducts, and alveoli as well as maturation of these cells. Moreover, there is fat deposition making the breasts larger as well.
After birth: The ducts and alveoli are fully formed, matured, and producing milk.
What stimulus is needed to cause the initiation of the production and the maintenance of the secretion of milk? What is the hormonal control in charge of it?
The main stimulus in charge of this is regular suckling and removal of the milk that was produced. With every time the baby feeds, there is a spike in both prolactin and oxytocin, which are paramount to milk production and secretion postpartum.
Why do prolactin levels fluctuate postpartum?
The levels of prolactin generally go down progressively after birth, however, they are constantly stimulated and spike every time the baby suckles. Generally prolactin is controlled through constant inhibitory control of prolactin inhibitory hormone (PIH = dopamine), however, when there is the physical stimulation of the nipple through the baby sucking, there is a signal sent through the spinal cord to the hypothalamus, which causes an increased release in the secretion of prolactin from the anterior pituitary and a decrease in the release of PIH.
Why is milk unable to be pushed out until after pregnancy?
Because although the breasts, ducts, and alveoli are fully ready to produce and secrete milk, the high oestrogen and progesterone levels prepartum actually inhibit milk secretion through the inhibition of prolactin receptors. It is until delivery, where there is a sharp drop in oestrogen and progesterone levels, that breasts can respond to prolactin and secrete milk.
What is oxytocin responsible for in milk and how is it secreted?
Oxytocin is responsible for the milk let down (ejection) towards the nipple, as the presence of oxytocin triggers the contraction of myoepithelial cells surrounding the alveoli (full of milk) which causes the letdown of milk. The production of oxytocin is a response to the physical stimulation of the nipple which causes a signal to be passed through the spinal cord into the hypothalamus which triggers release of oxytocin from the posterior pituitary.
What drug mechanism do we need to target if we want to suppress lactation pharmacologically? Why? Give an example?
In order to suppress lactation, we need to drive down the production of prolactin, and therefore, give dopamine receptor agonists, as they act as prolactin inhibitory hormone. An example is bromocriptine.
What drug mechanism do we need to target if we want to promote lactation pharmacologically? Why? Give an example?
In order to promote lactation, we need to drive up the production of prolactin, and therefore, give dopamine receptor antagonists, as they act antagonize prolactin inhibitory hormone. An example is domperidone.
What is an important side effect of lactation? What is the physiological explanation for it?
Breastfeeding provides a 98% protection from pregnancy. This is due to the fact that lactation provides high prolactin levels. Prolactin directly inhibit GnRH (gonadotrophin releasing hormone), therefore inhibiting LH and FSH secretion. This inhibits menstrual cycles, and enter into a state of amenorrhea and anovulation for around 6 months postpartum.
What is galactorrhea? What is its cause?
Flow of milk in the absence of pregnancy or lactation. It is caused by hyperprolactinemia.
What is gynecomastia? What is its cause?
Breast development in males, either unilateral or bilateral. It is caused by increased estrogen:androgen ratio.
What is colostrum? What is its composition?
The milk excreted by the woman in the first few days postpartum. It is rich in proteins, vitamins, and minerals. It is especially rich in immunoglobulins (IGAs) in order to give the baby some kind of protection and immunity.
Describe the transition from colostrum to fully mature milk and how their compositions differ?
While colostrum is rich in proteins, vitamins, minerals, and immunoglobulins, it is low in fats and sugars. As milk matures, it loses immunoglobulins and proteins and allows for more fat and sugars, essentially making the milk more caloric. The volume is also widely different. While colostrum will be only produced at a rate of 40ml/day, fully mature milk can be produced at a rate of up to 500ml/day.
What is obesity? How is it identified?
Obesity is the condition caused by an excessive amount of adipose tissue. It is identified according to the Body Mass Index (BMI) which is a value gotten by the following equation: weight (kg)/height in m2
What are the BMI cutoffs?
Under 18.5 = underweight 18.5-24.9 = normal 25-29.9 = overweight 30-39.9 = obese >40 = Morbidly obese
What is the relationship between BMI and mortality risk?
Any BMI lower than 18.5 or higher than 25 increases the risks of mortality through cancer, CV disease or other causes. These risks of mortality increase as the difference from the normal BMI range increases.
Describe a drawback with using BMI?
- It is a measure tailored mostly to Caucasians. For instance, the cutoff points are lower in south Asians (e.g. overweight starts at 23 instead of 25 and obese starts at 25 instead of 30).
What other measures should be considered alongside BMI? How do they relate to risk of CV disease?
Waist circumference. The higher the waist circumference the higher the risk of CV disease.
What are the trends of overweight and obesity in the population?
Over the last 20 years the number of overweight individuals has doubled from 15% to 29%, and the amount of obese individuals has increased by 11% as well.
Who is more likely to be overweight or obese, men or women?
Men
