Endocrine and Reproduction Physiology

Q1. In the endocrine study questions you indicated that ketones are not made from amino acids. If not what are they made from? I was under the impression that the liver could utilize A.A.'s by changing them to keto acids which could then enter Krebs cyce.

A1. Ketones (aka ketone bodies) are made from fatty acids. Keto acids are made via deamination of amino acids. Keto acids are converted into glucose via gluconeogenesis. Ketones go into the metabolic pathways to make ATP. Just to make things more confusing, ketoacidosis is caused by an increase in ketones (not keto acids). In diabetes (especially Type I) there is an increase in lipolysis and generation of fatty acids and ketones. The elevation in ketones causes the ketoacidosis seen in untreated diabetic patients.

Q2. What is the role of the ejaculatory ducts in the male reproductive system? The name implies that they are involved in ejaculation is some way but from what I understand from the note the sperm and semen are ejaculated from the urethr through smooth and skeletal muscle stimulation.

A2. The ejaculatory ducts are the segments of the male reproductive system where the secretions from the seminal vesicles and prostate gland join the sperm coming from the vas deferens to form semen.

Q3. I was wondering if you clarify for me the difference between a primary oocyte, secondary oocyte, and ovum. I seem to keep getting them confused. Is the ovum a type of primary oocyte? Is a secondary oocyte only after excretion, and if so..does that mean an ovum can be both a primary and secondary oocyte depending on whether it has been released from the follicle? I also wanted to make sure that all the oogonias have undergone mitotic division to become primary oocytes before a baby female is born.

A3. These are confusing terms. A primary oocyte is an oocyte that has undergone mitosis and has begun meiosis by replicating its DNA. This process occurs during fetal development and stops (meiotic arrest) by about 7 months of gestation. At birth all of the oogonia have undergone the first DNA replication and become primary oocytes and are in meiotic arrest. The secondary oocyte is formed after the first meiotic division just before ovulation. According to the book, "ovum" refers to the egg after the second meiotic division. Since fertilization causes the second meiotic division occurs the egg does not stay an "ovum" very long. I was sloppy in my terminology during lecture. I should have been calling the ovum an oocyte or "egg" most of the time.

Q4. What all do we need to know from the handout that talks about birth control for the test that was handed out to us during class?

A4. The handout, which is more current than the syllabus and textbook, was for your personal information. What you need to know about birth control is what is in the syllabus and in the textbook. Basically, know which methods prevent ovulation, block sperm transport (barrier methods) or inhibit implantation.

Q5. Do T3 and T4 only inhibit TSH or do they also inhibit the Hypothalamus trophic hormone TRH? I belive that all of the hypophysiotrophic hormones involve long feedback systems to both the hypothalamus and the anterior pituitary. Is the TRH/TSH system an exception?

A5. T3 and T4 only inhibit release of TSH at the anterior pituitary (by down regulating TRH receptors). This is an exception to the hypothalamic negative feedback seen with other hormone systems.