Alright. So we're going to finish up female anatomy by talking about the mammary glands. Mammary glands are actually modified sweat glands located within the subcutaneous tissue of the breast anterior to the thorax muscles. When I say "modified sweat glands," this modification happens very early in embryonic development for both males and females. In females, mammary glands go on to become more developed due to their high estrogen and progesterone levels. Despite that, mammary glands only actually function in lactating females. They will be producing milk in response to hormonal stimulation, particularly prolactin and oxytocin, which play a big role in milk production.
Each mammary gland contains between 15 to 25 lobes, so there's a good amount of variability across people there. These lobes radiate and open at the nipple. You can see we have a lobe depicted here, enclosed in that dark purple line — this entire thing is a lobe. The lobes are separated by fibrous connective tissue as well as fat, so they are quite distinct because of that very clear separation.
Within the lobes are units called lobules, and we've shown those here as these little purple circles all crammed together within that lobe. The lobules contain glandular alveoli, which are hollow sac-like structures that actually produce the milk during lactation. They are made of a modified epithelium that can synthesize and secrete milk.
We have our lobe, we have our lobules, and the milk has to actually get toward the nipple somehow. It does this by traveling down a duct system that we have drawn here in blue, called the lactiferous ducts. These ducts act as a passage for milk to reach the nipple itself. Additionally, we also have this little orange structure right there that is called a lactiferous sinus. This is essentially a sinus cavity where the milk can accumulate during nursing.
To summarize, each mammary gland will have an average of about 20 lobes. Within those lobes are lobules. Within the lobules are the glandular alveoli, which produce milk. The milk will then travel down the lobe via the lactiferous ducts and collect in the lactiferous sinus right near the nipple until it is ready to be used by the infant. Alright, those are mammary glands. Great job everybody with this entire lesson. It's been a long one to get through female anatomy, but you did fantastic. So I will see you in our next one. Bye-bye.