Mammalian Urogenital Lab Answers

The Mammalian Urogenital Lab Questions

1. The urine needs to be stored in egg-laying animals so that the fetus is not trapped in pools of urine inside of the egg. This keeps the urine separate from the fetus and its nutrients.

2. The fetuses of mammals that bear their young alive do not need a urine sac and does not form urine because all of the fetuses waste is taken out through the mother either through the placenta or the umbilical cord.

3. The testes are separated from the abdominal cavity in order to control their temperature. The testes work best when they are slightly cooler than our core body temperature so then during mating season, it is best to keep the testes a little farther away from the body. The testes should be withdrawn into the body when the outside temperature is too cold so as to receive some of the warmth back from the body and also for protection.
4.
Seminal fluid in a male is made by the contributions of many parts. The sperm itself is manufactured in the seminifurous tubules before they head to the epidiymus to be stored and to mature. When a male is ready to ejaculate, the sperm continues onto the vas deferens through involuntary contraction to end up in the urethral bulb. This is where all the other secretions that make up semen collect. The prostate gland secretes 30% of the seminal fluid by volume, a milky substance that activates the sperm and balance the pH of the acidic vagina (if that is where its going). The seminal vesicles provide almost 70% of the seminal fluid volume with fluid containing sugar and nutrients for the sperm to survive its journey. The Cowper’s gland secretions do not collect in the urethral bulb but gets released prior to ejaculation to cleanse the urethra and therefore some of its residual secretions will also comprise a very small percentage of the seminal fluid
volume.

5. It would be advantageous for some mammals to ovulate when triggered by hair pulling and biting to ensure that mating is to ensue and therefore not waste any eggs unnecessarily.

6. Egg laying mammals and marsupials cannot protect their unborn young as well as placental animals. Placental mammals get to carry their embryo with them everywhere they go and ensure that they are in the correct temperatures and get enough nutrients through their own diets as a continuing process through the time they are conceived until they are born, Egg-laying mammals may leave their eggs behind to look for food or to water and have to leave their embryos unprotected and vulnerable.

7. Only female birds have a medullary bone because it is there for re-absorption during their reproductive cycle for formation of the eggshells and is highly estrogen dependent.

8. Birds only lay one egg in a 24-hour period because they only have one working ovary which will have many ova but the largest ova will detach and become the yolk of the egg. Birds also only lay one eggs per day in order to keep their weight low. The eggs or heavy and accumulates too much bulk on the bird so it might not be physically possible to carry 2 eggs at a time to lay.

9. All of the eggs will usually hatch at the same time because the mother bird won’t start incubating until all of the eggs in her clutch are laid.