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
Autosome
Results of a fetilized ovum
Conceptus
Cells that remain after ovum formation and secrete estrogen and progesteron
Corpus luteum
Developing baby from weeks 3 through 8
Embryo
Reproductive cell
Gamete
Cell division in body cells
mitosis
Formation of female gametes
oogenesis
Release of the mature ovum from the ovary
Ovulation
Structure that provides nourishment for developing baby
Placenta
Ordinary body cell
Somatic cell
What are the two major occurrences immediately after fertilization
the zona pellucida prevents the other sperm from entering and the ovum completes its second meiotic division.
List three reasons the fundus is the best area for implantation
Good blood supply thick uterine lining muscle to limit post birth blood loss
When during prenatal development does this event occur? Closure of the neural tube
4 weeks
When during prenatal development does this event occur? Heart contains four chambers
8 weeks
When during prenatal development does this event occur? all abdominal organs are within the abdominal cavity
10 weeks
When during prenatal development does this event occur? External ear development begins
6 weeks
When during prenatal development does this event occur? Fetal sex apparent by external genitalia
12 weeks
When during prenatal development does this event occur? fetal movements felt by mother
16-24 weeks
When during prenatal development does this event occur? surfactant production begins
24 weeks
Describe the fetal structure or substance and state their purpose? Vernix caseosa
creamy skin covering to lubricate and protect fetal skin from amniotic fluid
Describe the fetal structure or substance and state their purpose? Lanugo
fine downy hair that helps vernix adhere to the skin
Describe the fetal structure or substance and state their purpose? Brown fat
heat producing fat found in back of the neck behind sternum and around kidneys
Describe the fetal structure or substance and state their purpose? Surfactant
Surface active lipid substance that helps alveoli remain slightly open between breaths to ease the work of breathin
Explain how the following mechanisms allows the fetus to thrive in the relativly low oxygen environment of the uterus?Fetal H/H
A high fetal H/H give the fetus more oxygen carrying capacity fetal hemoglobin can carry 20% to 50% more oxygen than adult hemoglobin
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
Fetal carbon dioxide quickly diffuses into the mothers blood causing her blood to become more acidic and fetal blood to become more alkaline this allows fetal blood to combine with oxygen more readily
Describe how passage of maternal immunoglobulin G (IgG) antibodies can be either benifical or harmful to the fetus? beneficial
Provides the newbore with temporary passive immunity to disease to which the mother is immune
Describe how passage of maternal immunoglobulin G (IgG) antibodies can be either benifical or harmful to the fetus? Harmful
Maternal blood type antibodies may cross the placenta and destroy incompatible fetal erythrocytes
Explain the function of this placental hormone? Human choionic gonadotropin (hCG)
Causes persistence of the corpus luteum to maintain estrogen and progesterone secretion during early pregnacy and causes fetal testes to secrete testoterone to stimulate development of normal male reproductive structures
Explain the function of this placental hormone? Human placental lactogen (hPL)
Promotes normal growth and nutrition of the fetus stimulates maternal breast development and makes more glucose available to the fetus by reducing maternal insulin sensitivity and glucose utilization
Explain the function of this placental hormone? Estrogen
causes uterine and breast enlargment growth of the breasts ductal system and enlargement of fetal external genitalia
Explain the function of this placental hormone? Progesterone
Change endometrium into decidua to nourish conceptus before placenta is established reduces uterine contractions and stimulates breast growth and development of the breast alveoli and ductal system
State the three functions of amniotic fluid?
Cushions fetus from impacts
provides stable temperature
Promotes normal fetal growth and development (Promotes symmetrical development preventing membrane adherence and allows fetal movement)
Explain the umbilical cord structure and functions? Umbilical vein
Carries oxygenated blood and nutrients from the placenta to the fetus
Explain the umbilical cord structure and functions? Umbilical arteries (two)
Carries deoxygenated blood and waste products from the fetus to the placenta
Explain the umbilical cord structure and functions? Whartons jelly
Protects the cord vessels from stretching or pressure that would interrupt flow
An important purpose of seminal fluid is to?
protect sperm from the acidic vaginal environment
Fertilization is complete when?
Fusion of the sperm and ovum nuclei occurs
The embryois fully implanted in the uterus on which day after conception?
10
Which fetal circulatory structure carries blood with the highest oxygen concentration