Question

Human chorionic gonadotropin (hCG) is secreted by a. the anterior pituitary. b. the posterior pituitary. c. the placenta. d. the thymus.

Short answer

Human chorionic gonadotropin (hCG) is a hormone that plays a vital role in pregnancy and is secreted by the placenta. Therefore, the correct answer is c. the placenta.

Step-by-step solution

Definition of hCG

Human chorionic gonadotropin (hCG) is a hormone that plays a vital role in pregnancy. It helps maintain the production of progesterone, support fetal growth, and signal the mother's body that she is pregnant. This hormone is what at-home pregnancy tests detect to determine if a person is pregnant or not.

Identify the source of hCG

Out of the options given, we need to determine which gland is responsible for secreting hCG. The anterior pituitary, posterior pituitary, thymus, and pineal gland are all part of the endocrine system, but they have a variety of functions and secrete different hormones. The correct answer is that hCG is secreted by the placenta during pregnancy.

Conclusion

Based on the given information, we can conclude that the correct answer is: c. the placenda.

Key concepts

Introduction to the Endocrine System

The endocrine system is a network of glands that produce and release hormones. These chemical messengers regulate many different bodily functions, including growth, metabolism, and reproduction. Unlike the nervous system, which provides quick, short-term responses, the endocrine system works over a longer period, effecting changes that can last from a few hours up to a lifetime.

Hormones travel through the bloodstream to targeted organs and tissues, where they bring about specific responses. This system plays a crucial role during pregnancy, where a finely tuned hormonal balance is essential for the development of the fetus and the health of the mother.

Hormone Function during Pregnancy

Pregnancy is a time of significant hormonal changes that are critical to support fetal development and prepare the mother's body for birthing. One of the key hormones is human chorionic gonadotropin (hCG), which ensures the maintenance of the corpus luteum and therefore the secretion of progesterone. Progesterone keeps the uterine lining thick and hospitable for the embryo.

Besides hCG, several other hormones play pivotal roles. Estrogen, for example, helps in the development of the fetus and stimulates milk duct development in the breasts. Oxytocin assists with labor, and relaxin helps to soften and widen the cervix. The harmony of these hormonal functions is crucial; any imbalance could result in complications.

Placental Secretion of hCG

The placenta is a remarkable organ that allows for the exchange of nutrients, gases, and waste between mother and fetus. It is also an endocrine gland that secretes various hormones, including the crucial human chorionic gonadotropin (hCG). After implantation of the fertilized egg, cells that will become the placenta begin to produce hCG.

The early presence of hCG signals the corpus luteum to continue producing progesterone, thus preventing menstruation and sustaining the pregnancy. The levels of hCG can be detected in a woman's blood or urine; this is the basis for pregnancy tests. Once the placental development is sufficient to maintain progesterone production itself, the importance of hCG diminishes. The whole process demonstrates the dynamic and critical role of the placenta in endocrine functions during pregnancy.