Conception and prenatal development Chapter 12

Gametogenesis produces ova and sperm that have half the full number of chomosomes or 23 unpaired chromosomes when and ovum and a sperm unite at conception, the number is restored to 46 paired chromosomes as in other body cells.

No new ova are formed after 30 weeks of prenatal gestation

One primary oocyte results in one mature ovum that contains 23 unpaired chromosoms (22 autosomes and an X chormosome)

A male can continuously produce new sperm from puberty through the rest of his life, although this production gradually declines with age.

One primary spermatocyte results in production of four mature sperm.  Two of the mature perm have 22 autosomes and an X chromosome.  two have 22 autosomes and a Y sex chromosome

THe male determines teh babys sex because sperm carry either an X or a Y sex chromosome.  The female contributes only an X chroomosome to the baby.

THe basic structure of all organ systems is established during the first 8 weeks of pregnancy.  Teratogens during this period can cause major structural and functional damage to the developing organs.

The fetal period is one of growth and refinement of established organ systems.

The placenta is an embryonic or fetal organ with metabolic respiratory and endocrine functions.

Transfer of substances between mother and her developing baby occurs by four mechanisms: simple diffusion facilitated diffusion active transport and pinocytosis.

Most substances in the maternal blood can be transferred to the fetus.

The fetal membranes contain the amniotic fluid which cushions the fetus allows normal prenatal development and maintains stable temperature

Two umbilical arteries carry deoxygenated blood and waste product to the placenta for transfer to the mothers blood one umbilical vein carries oxygenated and nutrient rich blood to the fetus.  Coiling of the vessels and enclosure in WHartons Jelly reduce compression and torsion of the umbilical vessels.

Three fetal circulatory shunts partially bypass the liver and lungs the ductus venosus the foramen ovale and the ductus arteriosus.  These structures close functionally after birth but are not closed permanently until several weeks or months later

Multifetal pregnancy may be monozygotic or dizygotic. twins are the most common form of multifetal pregnancy

Dizygotic twins are more likely to occur in certain families and racial groups, in older mothers, and in women who undergo infertility therapy.

Non-sex hormone

Results of a fetilized ovum

Cells that remain after ovum formation and secrete estrogen and progesteron

Developing baby from weeks 3 through 8

Reproductive cell

Cell division in body cells

Formation of female gametes

Release of the mature ovum from the ovary

Structure that provides nourishment for developing baby

Ordinary body cell

What are the two major occurrences immediately after fertilization

List three reasons the fundus is the best area for implantation

When during prenatal development does this event occur? Closure of the neural tube

When during prenatal development does this event occur? Heart contains four chambers

When during prenatal development does this event occur? all abdominal organs are within the abdominal cavity

When during prenatal development does this event occur? External ear development begins

When during prenatal development does this event occur? Fetal sex apparent by external genitalia

When during prenatal development does this event occur? fetal movements felt by mother

When during prenatal development does this event occur? surfactant production begins

Describe the fetal structure or substance and state their purpose?  Vernix caseosa

Describe the fetal structure or substance and state their purpose? Lanugo

Describe the fetal structure or substance and state their purpose? Brown fat

Describe the fetal structure or substance and state their purpose? Surfactant

Explain how the following mechanisms allows the fetus to thrive in the relativly low oxygen environment of the uterus?Fetal H/H

Explain how the following mechanisms allows the fetus to thrive in the relativly low oxygen environment of the uterus? Relative fetal and maternal blood carbon dioxide levels

Describe how passage of maternal immunoglobulin G (IgG) antibodies can be either benifical or harmful to the fetus? beneficial

Describe how passage of maternal immunoglobulin G (IgG) antibodies can be either benifical or harmful to the fetus? Harmful

Explain the function of this placental hormone? Human choionic gonadotropin (hCG)

Explain the function of this placental hormone? Human placental lactogen (hPL)

Explain the function of this placental hormone? Estrogen

Explain the function of this placental hormone? Progesterone

State the three functions of amniotic fluid?

Explain the umbilical cord structure and functions? Umbilical vein

Explain the umbilical cord structure and functions? Umbilical arteries (two)

Explain the umbilical cord structure and functions? Whartons jelly

An important purpose of seminal fluid is to?

Fertilization is complete when?

The embryois fully implanted in the uterus on which day after conception?

Which fetal circulatory structure carries blood with the highest oxygen concentration