Reproduction and Sexual Response Cycle

Reproduction, Fetal Development, and Heredity

• This chapter covers reproduction, fetal development, and heredity.
• It includes objectives for understanding the material, ranging from basic knowledge to evaluation of complex concepts.
• Comprehending the embryonic origins of specific tissues is one objective.
• Analyzing the components of semen and their role in reproductive success is another.
• Evaluating the differences between phenotypes and genotypes is a further objective.

The Sexual Response Cycle

• Sexual arousal can be reflexogenic or psychogenic.
• The sexual response cycle has four stages: excitement, plateau, orgasm, and resolution.
• During excitement, the autonomic nervous system causes changes like penile vasodilation (erection).
• The stages encompass physical and physiological changes.

The Male Sexual Response Cycle

• The cycle begins in the sacral spinal cord
• The cycle proceeds through excitement, plateau, orgasm, and resolution.
• Excitement involves penile erection, scrotum thickening, and elevated testes.
• During orgasm, seminal vesicles and prostate contract, with ejaculation.

The Female Sexual Response Cycle

• The cycle includes vaginal lubrication, uterine fibrillations, and clitoral erection/swelling.
• Excitement, plateau, orgasm, and resolution encompass this cycle's events.
• The orgasm stage involves rhythmic uterine contractions and vaginal dilation.

Components of the Male Ejaculate

• Seminogelin is a coagulant produced in seminal vesicles and holds sperm.
• Motility inhibitors keep sperm from struggling.
• Prostaglandins contract the uterus.
• hCAP-18 reduces cervical mucus viscosity.
• Factor III assists in coagulation and healing.
• PSAP prevents painful stimuli detection.

The Pre-Embryonic Period

• This period occurs before the embryonic stage.
• A detailed animation explains fertilization steps.
• Learning steps to fertilization is a key part of this period.

Capacitation

• Capacitation is a maturation process for sperm required for fertilization.
• Stages include insemination, sperm reservoir, initial capacitation, hyperactivation, cumulus mass penetration, and zona penetration.

Fertilization

• Fertilization is the fusion of a sperm and an oocyte.
• Capacitated sperm contact the zona pellucida; the acrosome reaction follows.
• Proteases digest the zona pellucida, and the plasma membranes rearrange and penetrate the perivitelline space.

Precise Fusion of Egg and Sperm

• Oocytes have microvilli, except where the pronucleus is.
• Microvilli serve as docking sites for sperm.
• Sperm-egg fusion activates the oocyte.
• PLCz triggers Ca2+ release from the oocyte's ER.

Pre-Embryonic Events Following Oocyte Activation

• Cortical reaction blocks polyspermy.
• Cortical granules release contents into the perivitelline space.
• The new barrier prevents further sperm fusion.

Early Embryogenesis

• Stages of early embryogenesis include cleavage, compaction, asymmetric division and blastulation.
• Cleavage is the division of a single-celled zygote into many.
• Blastulation leads to a blastocyst with a blastocoel.

Uterine Receptivity and Implantation

• Three stages prepare the uterus for implantation: apposition, attachment, and penetration.
• Apposition brings the uterine wall and blastocyst into proximity.
• Attachment involves blastocyst polarity and cytotrophoblast development.
• Penetration includes blastocyst burrowing into the endometrial stroma.

Embryogenesis and the Origin of Tissues

• Extraembryonic tissues originate from inner cell masses.
• The hypoblast creates extraembryonic endoderm.
• The epiblast gives rise to the embryo proper; both form the blastocyte.

Formation of the Three Primary Germ Layers: Gastrulation

• This process involves migrating cells displacing the hypoblast to generate the primary germ layers: endoderm, mesoderm, and ectoderm.

Embryonic Folding

• Embryonic folding involves cephalic-caudal and transverse axes.
• The folding results in a developing embryo divided into cephalic and caudal regions, with distinct layers formed (ectoderm, endoderm, and mesoderm).

The Fate of the Mesoderm

• The mesoderm differentiates into distinct structures like the kidneys, gonads, somites, and sclerotome.

The Fates of the Ectoderm and Endoderm

• Ectoderm develops into nervous tissue, epidermis, sense organs, teeth enamel, and other structures.
• Endoderm forms the internal lining of the respiratory system, GI tract, urinary tract, sections of the liver, pancreas, and parts of other organs

Structure and Function of the Placenta

• The placenta is a chimeric organ with maternal and embryonic tissues.
• It facilitates material exchange between the mother and fetus, and produces hormones required for pregnancy.

Pregnancy

• This stage covers crucial events like placental hormone production, uterine growth, and mammary gland changes.
• Pregnancy complications like ectopic pregnancy, placenta previa, preeclampsia, dystocia, and immature babies are explored.

Growth of the Uterus During Pregnancy

• The uterus grows significantly throughout pregnancy.
• Hypertrophic and hyperplastic uterine myometrium growth drives this change.
• The growth extends to the sternum.

Development of the Mammary Glands During Pregnancy

• The mammary glands develop in response to placental hormones to prepare for breastfeeding.
• Areola and nipples darken due to melanocyte-stimulating hormone (MSH).

The Hormones of Pregnancy

• Hormones like hCG, estrogen, and progesterone play vital roles in pregnancy.
• hCG's production occurs early and promotes uterine development.
• Estrogen stimulates uterine contractions for parturition (birthing).
• Progesterone prevents premature contractions.

Other Hormones Involved in Pregnancy

• Other important hormones include:
  • Placental lactogen (PL)
  • Prolactin (PRL)
  • Relaxin
  • Corticotropin-releasing hormone (CRH)

Parturition

• Parturition (the process of childbirth) involves three stages:
  • Cervical effacement and dilation
  • Fetal and placental expulsion
  • Hormonal regulation.

Sexually Transmitted Diseases (STDs)

• This section covers common STDs.
• Information on estimated numbers of new cases and examples of infections is provided.

Contraceptive Methods

• This section includes information on various contraceptive devices and their effectiveness for unintended pregnancy prevention.