Lecture 4

Question 1

Sexual Intercourse

Answer 1

• Also, physiologically know as:
  Sex, coitus or copulation, erection and ejaculation
• Facilitates the union of the male and female gamete to
  accomplish reproduction
• Requires the delivery of sperm containing semen (sperm plus
  accessory gland secretions) into the female vagina
• At the correct time of the female ovarian cycle

Question 2

Super physiology to make conception happen:

Answer 2

Fortify the troops - The liquid portion of semen not only provides the sperm with nourishment for the journey, it actually coagulates in a woman’s vagina after ejaculation, forming a physical barrier that prevents the sperm from wandering in the wrong direction. This disappears within 30 min, when the semen becomes liquefied.
Call in the transport unit - The cervical canal is a much more welcoming environment, and sperm that make it there find themselves awash in a sea of cervical mucus. The mucus is specially designed to transport sperm efficiently when you’re most fertile. As you approach ovulation, the mucus becomes stretchy, clear and thin and strings of molecules line up like train tracks so that sperm can hop on and ride to their destination.
Picking up speed - A just-ejaculated sperm cell has to spend a couple of hours going through biochemical changes, called capacitation, speed to help it make its way into the uterus and fallopian tubes to find its target.
Timing is Important - Sperm must reach their destination within the right time frame for when the egg is there.
They also need to pick their destination carefully - An egg is usually only present in one of the two fallopian tubes in any given month.

Question 3

Sexual Response Cycle

Answer 3

1. Reflexive
   (autonomic activation; genital reflexes and sensations, innate
   copulatory behaviors)
   - involves hypothalamus, brainstem, spinal cord
2. Excitement phase
   Includes erection and heightened sexual awareness, increased genital bloodflow
3. Plateau phase
   Characterized by steadily increasing heart rate, blood pressure, respiratory rate, and muscle tension
4. Orgasmic phase
   Includes ejaculation and other responses that are collectively experienced as intense physical pleasure
5. Resolution phase
   Return of genitalia and body systems to pre-arousal state

Question 4

Question 5

Similar in female:

Answer 5

• Parasympathetic nerves signal erectile tissue around vaginal
  introitus
• Bartholin’s glands secrete mucus
• Orgasm isn’t necessary for fertilization

Question 6

Mechanism of Female Excitation

Answer 6

Sympathetic activation causes blood to accumulate in the spongiosum of the clitoris and labia

Question 7

Mechanism of Erection

Answer 7

Question 8

Question 9

Mechanism of Emission and Ejaculation

Answer 9

Question 10

Question 11

Volume of ejaculate?

Answer 11

Average 2,75 mL (2-6 mL)

Question 12

Contents of semen?

Answer 12

1. Sperm (20%)
   - ejaculate (60 mil per mL; up to 400 million total))
   - under 20 million regarded as infertile
2. Seminal plasma (80%)> Seminal vesicles (70%)
   - Fructose-energy
   - Prostaglandins – muscle contraction
   - Thick white and alkaline> Prostate (30%)
   - Citric acid, calcium and coagulation protein
   - Alkaline
   - Smell
   - Fibrinolysin> Bulbo urethral glands (> 1%)
   - Lubrication
   - neutralizes acidity of urine in urethra

Question 13

Male Fertility

Answer 13

Question 14

Journey of the Sperm

Answer 14

Question 15

Sperm capacitation

Answer 15

Question 16

Acrosome and cortical reaction

Answer 16

Question 17

Fertilization and Embryo development

Answer 17

The dividing embryo takes four or five days to move through the Fallopian tube into the uterine cavity.

Under the influence of progesterone, smooth muscle of the tube relaxes, and transport proceeds slowly.

The developing embryo reaches the uterus, it consists of a hollow ball of about 100 cells called a blastocyst.

Trophoblast cells secrete proteolytic enzymes

These act on the endometrium permitting penetration of blastocyst into endometrial stroma.

These cells + maternal cells, form the placenta & membranes of pregnancy.

Question 18

Implantation

Answer 18

Some of the outer layer of blastocyst cells will become the chorion, an extraembryonic membrane that will enclose the embryo and form the placenta.

The inner cell mass of the blastocyst will develop into the embryo and into three other extra-embryonic membranes.

These membranes include the amnion, which secretes amniotic fluid in which the developing embryo floats; the allantois, which becomes part of the umbilical cord that links the embryo to the mother; and the yolk sac, which degenerates early in human development.
Implantation of the blastocyst into the uterine wall normally takes place about seven days after fertilization.

The blastocyst secretes enzymes that allow it to invade the endometrium, like a parasite burrowing into its host.

Endometrial cells grow out around the blastocyst until it is completely engulfed. As the blastocyst continues dividing and becomes an embryo, cells that will become the placenta form finger-like chorionic villi that penetrate into the vascularized endometrium.

Question 19

Contraception

Answer 19

Abstinence is 100% effective
Interventional methods of contraception include: (1) barrier methods, which prevent union of eggs and sperm; (2) methods that prevent implantation of the fertilized egg; and (3) hormonal treatments that decrease or stop gamete production.
The efficacy of interventional contraceptives depends in part on how consistently and correctly they are used.

Question 20

The site of fertilization

Answer 20

The oviduct

Question 21

Implantation of the blastocys in the

Answer 21

prepared endometrium