Development Lab

The gametes produced in the gonads undergo mitosis to create primary spermatogonia or primary oogonia and meiosis to each become haploid cells. Four haploid sperm are produced in the testes, while only one functional haploid oocyte is produced in the ovaries. Each has ½ the number of chromosomes once the process of meiosis is completed.

Sperm are stored and released through the male ducts and deposited into the female vagina during intercourse. Sperm have been activated and must be alive and motile to swim through the female ducts and reach the ampulla of the Fallopian tube.

At ovulation, the ovaries release secondary oocytes into the peritoneum. The oocyte travels with some cuboidal cells that form the corona radiata which secretes a gelatinous material called the zona pellucida. The fimbria of the Fallopian tube sweep up the oocyte and it moves to the ampulla of this tube. The oocyte sends signals to the sperm moving up through the female reproductive tract. The oocyte stays in the ampulla for about 24 hours and the sperm are viable for about 48 hours.

During sperm movements through the female reproductive tract, they become capacitated and their acrosomal cap weakens. As the sperm encounters the corona radiata, the enzymes in the acrosomal cap are released and help to digest through the layers around the oocyte. When the sperm penetrates the cell membrane of the oocyte, the oocyte signals ionic changes that prevent other sperm from entering. The oocyte then completes its meiotic division to become a mature egg, or ovum.

Meiosis wall mount

Female Reproductive wall mount with Oocyte

Male Reproductive wall mount with Sperm

Development wall mount

Embryonic Development

Fertilization occurs in the ampulla of the oviduct and involves the joining of the haploid pronuclei of the egg and sperm to create a single celled fertilized egg called the zygote. At this time the chromosome number is restored to the diploid (2n) number and the sex of the individual is determined. Within 24 hours the zygote begins to move down the Fallopian tube and divide by mitosis to produce daughter cells called blastomeres. The mitotic division of the zygote is called cleavage. From one cell, two cells, then four cells, and 8 cells by mitotic division. Within 3 days there are 16 blastomeres and the zygote is termed a morula. Cells continue to divide as the morula enters the uterine cavity. Fluid from the uterus enters the morula and creates a sphere with a fluid filled hollow ball of cells known as the blastula. The outer rim of cells is called the trophoblasts and the inner group of trophoblasts will produce a hormone that signals pregnancy to the ovary so that the corpus luteum is maintained and progesterone is secreted for the uterine lining.

This hormone human chorionic gonadotropin (hCG) is the signal to the ovary and also forms the basis of the urine pregnancy tests. The outer group of trophoblasts forms chorionic villi that digest through the uterine lining during implantatin to help create the fetal portion of the placenta. The inner mass of cells becomes the embryo once the cells undergo gastrulation. The embryo after gasrulation consists of three germ layers: the ectoderm which forms the nervous system and the epidermis of the skin; the endoderm which forms the other epithelial linings, and the mesoderm which forms all the connective and muscle tissues.

Development wall mount

Embryonic Models

fertilization: beginning, finished

Embryo in Utero

Embryonic Development with membranes

Mitosis wall mount

Mitosis models: Prophase, Metaphase, Anaphase, Telophase

Mitosis Drawing

Zygote drawing

Zygote histology: Zygote, Early Cleavage, Late Cleavage

Embryology Development Model

Embryo Specimens

Embryo histology

Embryonic Tissues and Regions

Ultrasound of Embryo

Extra Embryonic Tissues

In order to support the embryo, extra (external) embryonic membranes form at 20 days.

The extra embryonic membranes are:

The placenta is a temporary endocrine structure composed of fetal chorionic villi and maternal blood supply. In addition to producing progestins, the placenta allows for nutrient and waste exchange between the fetus and mother.

The amnion is a thin membrane formed above the ectoderm. It contains amnionic fluid that helps provide a cushion and allows for embryonic development and movement.

The yolk sac is an outpocketing of the embryonic endoderm. It provides blood stem cells and the reproductive stem cells for the gonads. Eventually it is incorporated into the umbilical cord.

The allantois is also an outpockeing of the embryonic endoderm. It forms the umbilical cord and part of the lower digestive and urinary tracts.

Extra Embryonic Membrane Models

Placenta Models: Fetal Chorionic Villi, Afterbirth

Specimen: pregnant uterus

Placenta

fetus

Fetus In Utero Models

Development wall mount

Gestation

The period of the embryo occurs from fertilization through the second month or 8 weeks. During this time the tissues and organs are forming to create the body systems. After 8 weeks, the embryo is termed a fetus. During the fetal period, the organs formed during the first 8 weeks continue to grow and mature until the end of gestation at 9 months or the 40^th week. As pregnancy progresses, the uterus enlarges to accommodate the fetus. At parturition or childbirth the fetus is expelled during labor through the vagina to become a neonate.

The three stages of labor are dilation of the cervix, fetal delivery, and placental detachment & expulsion. The primary hormone responsible for labor is oxytocin (OT) which comes from the posterior pituitary and is controlled through positive feedback mechanisms.

Pregnancy models

Pregnancy Poster

Labor Stages : Dilation/Crowning, Delivery / Expulsion, Placental

Female pelvis with fetal head

Fetal Circulation

Fetal circulation differences occur. In utero, there are shunts that allow for bypasses to the liver and lungs. In the heart the bypasses around the fluid filled lungs are the foramen ovale and the ductus arteriosus. In the liver, the bypass is the ductus venosus. Shortly after birth, the bypasses close and allow for blood flow through the lungs and liver.

Fetal Structure Adult Structure

Foramen ovale Fossa Ovalis

Ductus Arteriosus Ligamentum Arteriosum

Ductus Venosus Round ligament of the liver

Fetal Circulation model

Medical Terminology

pedia- child post- after

-sis condition meso- middle

troph/o- nutrition chori- fetal membrane

germ- bud gest- bear, carry

omphal/o- navel prim- first

pto- fall terat/o- malformed fetus

vita life viscer/a- organ

amni/o- amnion -arche beginning

-gravida pregnancy -para to bear (offspring)

-tocia childbirth, labor neo- new

Exercises/Activities

I. ID development

A Drawings : Mitosis stages, Embryonic Regions

B Models: Identify Model A, Identify Model B

Identify the Extra Embryonic Membranes

Identify the Embryonic Stages

C Wall Mount

II. Obgyn report

Concept Map: Make a concept map of the events of development starting with fertilization until birth. Include this map as part of your LAR lab report (if selected) as a document insert or as an addtional PDF document scan.

Case Study

Applications

Premature Labor, Premature rupture of Membranes (PROM)

Abortion

Twins

Amniocentesis

Chorionic Villi Sampling

Fetal Alcohol Syndrome

Premature birth

Apgar score

Ectopic Pregnancy

Toxemias of Pregnancy: Preclampsia, Eclampsia