EMBRYOLOGY

Rarest Footage of Fetal Development

• http://www.ehd.org/playlist-movies.php?list=5

ACROSOME

Embryology

• Development begins at the moment of fertilization and conception– Development can be divided into stages as follows:– Embryological Development comprises events

from fertilization to 2 months. The study of these events is called Embryology.

– Fetal Development begins at the 9 weeks till birth.– Developmental Anatomy is the study of sequence

of events from fertilization to an adult organism.

Fertilization

• Ovum & Sperm=Gametes• Oocyte is viable for 12-24 hrs• Sperm is viable for up to 72 hrs• Intercourse must occur 72 hrs before

ovulation or 24 hrs after ovulation for fertilization to occur.

• Only about 100 sperm out of 200-400 million reach the area of the oocyte.

Fertilization Cont.

• It takes many sperm working cooperatively together to penetrate the corona radiatia (a layer of follicle cells that surrounds the oocyte for nutrition. Below the corona radiatia is a 2nd layer called the zona pellucida

• The acrosomal cap of many sperm release enzymes, one of which is called Acrosin. Acrosin helps to break down the corona radiate.

Fertilization cont.• Suddenly one sperm breaks all the way through. This

triggers a chemical composition change to the ovum which blocks any other sperm from penetrating ovum. Many sperm die from all the work to penetrate the ovum.

• Of the millions of sperm, only ONE can penetrate the oocyte. Fertilization occurs at the moment the genetic material of the sperm combines with the ovum to form an ZYGOTE.

• Fertilization is defined as the union of the sperm cell & oocyte with subsequent union of their genetic material

ACROSOME destroys Corona Radiate

Contact with Zona Pellucida=Fertilization

Boy or Girl• The Zygote represents the first cell of the new

individual. The sex of the new infant is determined at the very instant of fertilization & depends entirely on the pattern of sex chromosomes present in the nucleus of the sperm.

• All cells, except gametes contain 46 chromosome (DNA &RNA) which are blueprint of information of how person develops.

• 44 chromosomes are for development, but 2 are sex chromosomes.

Sex Determination

• Two types of sex chromosome.– Female have two X chromosomes (XX) + 22 other

chromosomes– Males have one X and one Y (XY)+ 22 other

chromosomes.At Fertilization the 23 chromosomes from each parent

combine for full set of 46 chromosomes, but sex is determined by sperm. An ovum fertilized with an X carrying sperm = female embryo. An ovum fertilized with a Y carrying sperm= male embryo.

Genetic Hereditary

• When the nuclei of two gametes fuse at fertilization, the resulting zygote has chromosomal genetic hereditary information from both parents.

• Offspring exhibit characteristics of both parents, but not exact copies.

• Some genes are dominant and others recessive. A dominant trait only requires one gene, were as a recessive trait requires both genes from each parent.

Dominant/Recessive Traits

• You inherit a gene for blood hair from one parent and a gene for dark hair from the other parent. Chances are you will have dark hair. Dark hair is dominant.

• Widows peak, dimples, clockwise hair whirl, dark hair, curly hair, long eyelashes, turned up nose, free earlobes, freckles, dark eyes & hazel eyes, tongue rolling====all dominant traits

Early Fetal Development• With fertilization, the ovum is no longer just an egg. It is the

start of a new human being. This newly formed early cell development is referred to as a Zygote.

• The time that this new human being spends in the female reproductive tract is referred to as gestation. This would include the zygote, embryo and fetus.

• Human gestation is about 38 weeks, counted from the estimated day of fertilization or 40 weeks from the last menstrual period (LMP).

• The branch of medicine that deals with pregnancy, labor, delivery and the time immediately after delivery is called OBSTETRICS.

Trimesters

• Gestation is divided into 3 trimesters of 3 months duration each.

• 1st Trimester: Embryonic and Early Fetal development: rudimentary beginnings of organs are formed.

• 2nd Trimester: Organ development is near completion.

• 3rd Trimester: Rapid fetal growth with many organs functioning.

Mitotic Cell Division• As the zygote journeys down the fallopian tube, it

begins to undergo mitotic cell division forming first 2 cells, then 4 cells and so on.

• Mitosis: the process of cell division that results in 2 daughter cells with exactly the same number and type of chromosomes as the parent cell.

• This early stage of development is called CLEAVAGE (cell division following fertilization)

• Cleavage increases the number of cells in the zygote, it does not increase the size of the zygote. It is still contained in the zona pellucida and is still getting nutrition form the corona radiate.

Journey to the Uterus

• The zygote remains in the FT for about 3-4 days, dividing repeatedly during it’s slow journey to the uterus.

• At the proximal end of the FT, the tiny zygote is a ball of 16 cells called a MORULA.

• Morula is a solid spherical mass of cells, still surrounded by the zona pellucida, resembles a mulberry, and is the same size as the original zygote.

Reaching the Uterus• At about day 4 ½ to 5 days, the Morula reaches the uterus &

has continued to divide into a dense cluster of about 100 cells with a hollow center.

• Upon entering the uterus it is referred to as a Blastocyst (hollow). The blastocyst has an outer covering called the TROPHOBLAST. This outer covering will form the placenta.

• The inner cell mass of the blastocyst will form the actual embryo.

• Uterine lining is still preparing for the fertilized ovum, so the zygote will float freely in the uterine cavity. The zona pellucid is now disintegrated, the zygote is enlarged. It now recieves nourishment temporarily from uterine secretions called uterine milk

Implantation • Around day 6-12 after ovulation, the blastocyst will

attach to the endometrium of the uterus, eroding the lining away in a small area, embedding itself in the thick velvet musoca of the endometrium.

• Once the blastocyst is embedded, the uterine lining forms the hormone called HCG (Human Chorionic Gonadotrophin).

• Implantation outside of the uterus is called Ectopic Pregnancy. Tx is surgery. The embryo has to be terminated to save the mother. Efforts are made to save the FT and ovary if possible. Prompt treatment must occur to save the mother.

Human Chorionic Gonadotrophin (HCG)

• Pregnancy Hormone that is produced by the uterine lining after implantation

• This is then secreted by the kidneys, and can be detected in urine=pregnancy tests.

• HCG tells the corpus luteum to continue to produce progesterone to maintain the lining of the uterus to maintain the pregnancy. Thus HCG stops the menses from starting.

EMBRYO DEVELOPMENT 1

Zona pellucida

CLEAVAGE

Morula

BLASTOCYST

EMBRYO DEVELOPMENT 2

• http://www.ehd.org/movies.php?mov_id=5

• View each of the slides in 0-2wk• http://www.ehd.org/science_main.php?level=

i (view movie the first week and

CLEAVAGE

MORULA

Inner Cell Mass

• While implantation occurs, the inner cell mass continues to develop into three germ layers. These 3 primary germ layers form the foundation for development of organs and organ systems.

• The process of gastrulation is the movement of the inner cell mass that creates the three primary germ layers.

Primary Germ Layers

• Ectoderm: gives rise to the Nervous system, epidermis of the skin (including nails & hair), & upper layer of cells & nerves.

• Endoderm: forms mucosa & associated glands, the lower layer of cells (digestive & respiratory, portions of urinary, reproductive & endocrine). Also liver & pancreas

• Mesoderm: gives rise to everything else. Develops in middle of Ectoderm & Endoderm. Includes heart, bone cartilage, muscles and blood vessels

IMPLANTATION-Day 8 Notice the chorionic villi

Placenta Formation• Once the blastocyst is implanted, it develops

projections called Chorionic Villi. These projections form from the outer fetal membrane called chorion.

• These projections form the Placenta. • Placenta=temporary organ that provides

nourishment & waste removal for the embryo• By 3rd week: Placenta is delivering nutrients &

oxygen and removing waste. This exchange occurs through the placenta barrier. Mom & Embryo blood remain separate

Placenta Formation• By the end of 2nd month, the placenta becomes an

endocrine organ, producing estrogen & progesterone to maintain the endometrium

• With formation of the placenta, the embryo is now surrounded by a fluid filled sac called AMNION (Fluid=amniotic fluid). This sac is the inner membrane protecting the embryo. The CHORION is the outer layer of the fetal membrane. It is attached to the placenta by a blood vessel containing a stalk of tissue called the umbilical cord.

PLACENTA & UMBILICAL CORD

Umbilical Cord• Umbilical cord is the link between the embryo

and the placenta. One large blood vein carries oxygen, blood & nutrients to the embryo and 2 vessels (arteries transport deoxygenated blood, & waste products from the embryo to the placenta. Till birth, the cord supplies everything the developing embryo needs.

ECTOPIC PREGNANCY

• 9-Week Human Embryo from Ectopic Pregnancy

Teratogen

In the Iate 1950s a German company launched thalidomide, marketed as a cure for morning sickness . Many fetal deaths resulted and a large range of disabilities, typically short limbs and flipper-like arms as well as deafness and blindness.

FAS

• http://www.nofas.org/wp-content/uploads/2012/10/NOFAS-FASD-What-Everyone-Should-Know-2012.pdf

• S&S• http://www.nofas.org/wp-content/uploads/

2012/05/identification.pdf

Folic Acid

• http://www.marchofdimes.com/pregnancy/folicacid.html

AMNIOTIC SAC AND UMBILICAL CORD

Amniotic Fluid

• Serves as a shock absorber. The baby floats in the fluid throughout uterine life

• Temperature of Amniotic Fluid is approx 99.5 degrees. This is to warm the infant

• This warm amniotic fluid not only warms the baby, but also the mother!

UMBILICAL CORD

AMNIONIC SAC

2-8 weeks of Life• Through the 8th week we refer to the developing

individual as an embryo with the following characteristics:• Length 4 cm long, Weight 1GM• All organs in place• Brain waves at 6 weeks, 2 days with the brain making half

the body weight.• Kidneys making urine at 8 weeks• Limbs are present, initially buds, then webbed fingers &

toes.• Heart beating at 3-4 weeks at 140-150 beats/min

Risk of Miscarriage• Miscarriage or spontaneous abortion occurs in

approx 25% of all pregnancies.• Greatest risk is during period of rapid

development during first 8 weeks• Some believe that miscarriages are due to

malformation or genetically abnormal embryo.• Early cervix dilatation, infection, STD’s, high

temps, drug ingestion, smoking, & alcohol use may be other causes of miscarriage

FINGERS AND TOES

FIRST TRIMESTER

Third Month: 9-12 weeks• At the 9th week we now refer to the developing baby

as a fetus & is capable of the following:• Flexes arms and legs, jerks back to stimuli, • Has hiccups• Liver, spleen and bone marrow begin to produce

blood cells• Sex can be determined• 9cm from crown to rump• Fingerprints present at 10 weeks• Rooting reflux present at end of 3 months

2nd Trimester, Fourth Month 13-16 weeks

• Sense organs are present• Eyes & ears in position. Fetus can see light—

will shield face from light with hand.• Most bones are distinct• Joint cavities apparent• Tibia is ossified

Vernix Caseosa

What is the function of Vernix Caseosa?

LANUGO

• This soft prenatal hair is called lanugo hair. Most of the time, most of this hair is shed during the 7th or 8th month of pregnancy. Sometimes it is still present for a few months after birth, especially in babies born early.

Fifth Month, 17-20 weeks

• Vernix Caseosa: protective skin coating made up of fatty secretions of sebaceous glands covers body; aides in delivery

• LANUGO: silk-like hair covers skin to help retain vernix caseosa

• Quickening occurs: mother feels spontaneous muscular activity of fetus

• Crown to rump: fetus measures 12cm

Sixth-Seventh Month, Weeks 21-30Mid Term of Pregnancy

• Fetus increases in weight• Most energy goes to brain growth• May survive if born premature at 27-28 weeks• Baby can move freely doing “somersaults” till end of

7th month, when it starts to become cramped.• 26 weeks-can develop tears• Skin is red and wrinkled, with nails present• Testes descend into scrotum• Crown to rump: 28 cm

3rd Trimester

• 8-9 months, 30-40 weeks• Skin is whitish pink, fat is laid down under SQ

tissue• Crown to rump 35 cm (14-15 inches) & weight

6-10#• Engagement occurs with head descending into

lower end of uterus as the cervix thins

Prenatal Care• Pregnancy is a natural condition; not an illness• Good Diet;high in iron & calcium, exercise, & regular

prenatal care are important for infant and mother.• Risks increase with age of mother• Dr’s visits include checking: weight, B/P, blood grouping,

medical history, FHT, testing for STD, & fundus height• Prenatal vitamins with folic acid is essentialDr’s only may allow mother to take Tylenol.-Exposure to infectious disease, especially Rubella can cause

serious fetal damage.

Effacement

The cervix effaces and thins out in the final weeks of pregnancy. As labor progresses the cervix dilates from 0 centimeters to 10 centimeters

PREGNANCY CONDITIONS

• TOXEMIA: pregnancy induced hypertension. Monitor weight & edema. Can led to Pre-eclampsia

• PRE-ECLAMPSIA: Toxemia of pregnancy with HTN, Headaches, proteinuria, edema of legs

• ECLAMPSIA: progression of pre-eclampsia with coma and convulsions. Can lead to death

Engagement or LighteningThis is the fetus descending into the lower pelvis. Mom will feel an increased pressure in the lower abdomen and notice that the baby is gradually dropping. Mom is relieved to find it much easier to breath.

PARTURITION = PROCESS OF BIRTHING

Early Stage I • This is usually the

longest phase of labor. However, contractions tend to last less than a minute with five or more minutes between contractions. These contractions thin and begin to open the cervix. Most women maintain normal activity

Active Stage IDuring this phase, the cervix dilates from four to seven centimeters. Women are more actively involved in the work of labor. Contractions grow progressively stronger and longer during this time, lasting 40-60 seconds or more and coming every two to five minutes.

Transition• Transition:This is

usually the hardest phase of the first stage of labor, but often the shortest. This phase completes dilation of the cervix to 10 cm. Contractions are very intense, lasting 60-90 seconds and occurring as close as every two minutes.

• Crowning occurs.

Episiotomy

BREECH Presentation

Stage III Placenta Delivery

Videos

• http://www.babycenter.com/video/live-birth

Vaginal deliveryInductionC-section -Twins

Breastfeeding

• http://www.womenshealth.gov/breastfeeding/breastfeeding-benefits.php

TWINS

Fraternal twins develop when two eggs are fertilized by two sperm.

Identical twins are formed from one fertilized egg that splits into two identical halves after conception.

AMNIOCENTESIS

http://www.youtube.com/watch?v=xwZOmVsiOHI orhttp://www.youtube.com/watch?v=DQQyZ8v7_C8

CHORIONIC VILLUS SAMPLING

• http://msjensen.cehd.umn.edu/webanatomy_archive/wa_reproductive/wa_repro_diseases1.html