FETAL DEVELOPMENT

FETAL DEVELOPMENT

FROM CONCEPTION TO BIRTH

Healthcare Science Technology 1

Mrs. Burgstiner,BSN

A. Fertilization: Sperm penetrates Egg

• Oocyte is released from the ovary and begins down the fallopian tube.• Sperm enters the female reproductive tract through the vagina during

intercourse. • About 300 million sperm cells enter the vagina but only about 1%

make it through the uterus to the fallopian tubes after approximately 10 hours

• One sperm then penetrates the oocyte (egg) through the zona pellucida which is the membrane surrounding the oocyte (egg)

• Sperm then breaks apart inside egg: this helps to determine the sex of the developing fetus by the DNA

• Zygote: joining of the sperm and ovum (egg ) to create new life or a new cell.

• This completes the fertilization process.

B. Cleavage:(1.5-3 days post ovulation)• Rapid Division of the Zygote into two cells, then 4 cells

and so on and these cells are called blastomeres.• This series of divisions occurs about one every 24 hours. Then when the cell division reaches 10 – 32 cells it is called a Morula

The morula leaves the fallopian tube and enters the uterus.

This takes place about 3-4 days after fertilization.

C. Early Blastocyst: (4 days)

1. The Morula is now inside the uterus. 2. Cell division continues until a blastocele forms in the center of the Morula. 3. Once the blastocele forms in the morula it is then called a

blastocyst and has a cavity in the middle.4. Two types of cells are at work now:

A. Embryoblast: cells inside the blastocele. B. Trophoblast: cells outside of blastocele

D. HCG Hormone is Released (5-6 d.)• On around the 6th day: blastocyst hatches or is released

from zona pellucida (surrounding membrane)• The trophoblast cells then secrete an enzyme Human

Chorionic Gonadatropin (HCG) that erodes the uterine wall• This creates an implantation site on the inner uterine wall. • Implantation to uterine wall: hormones are stimulated and

the ovary produces progesterone and the HCG continues releasing as the blastocyst implants into the uterine wall.

• The blastocyst becomes swollen with new capillaries and circulation begins between mother and fetus…this process is necessary for pregnancy to continue.

E. Implantation is complete: 7-12 days)

1. The trophoblast cells continue to engulf/destroy the uterine lining

stimulating new capillary growth from the blood pools they create.

2. This is when placental circulation beginning) 3. Top layer of cells becomes the embryo

4. Lower layer : becomes the yolk sac.

ECTOPIC PREGNANCY

An Ectopic Pregnancy an occur during implantation. This is when the implantation takes place outside of the uterus….

Can take up to 16 weeks to manifest. Surgery is required in most cases to remove the implanted fetus. Also known as a tubal pregnancy).

F. Placental Attachment: Chorionic Villus:“fingers” of the formingplacenta, that anchor the placenta to theimplantation site in the uterus.The Embryo is attached by a connecting stalk to the developing placenta by the Umbilical cord.

This is a picture of the placenta after delivery. The baby and the placenta are both delivered….you can see the umbilical cord here as well.

G.Gastrulation begins: the 3 layers of the embryo

A narrow line of cells start to form and the future axis of the embryo takes shape and marks the beginning of gastrulation.Gastrulation forms the three layers of the embryo from which cells, tissues, organs and systems develop.The 3 layers are:EctodermMesoderm EndodermThe next slide will show you what these 3 layers become.

Ectoderm, Mesoderm and Endoderm

During gastrulation, three major cell lineages are being established. They are the Ectoderm (shown in the diagram as blue), Mesoderm (red) and Endoderm (yellow). Following gastrulation, various cell lineages are derived from these three primary cell types. For example, the Ectoderm gives rise to the epidermis and its derivatives such as nails, hair and teeth. On the other hand, the Ectoderm also gives rise to the Central Nervous System.

G. Fetus at 2-3weeks

1/10 of an inch longnervous system is developingblood cells are developed

H. Fetus at 4 weeks

May float freely for 48 hours before implantingArm buds start to be evidentgets more of a curved appearanceeyes start to developimplantation of to the uterus and placenta is taking place

I. The Fetus at 5 weeks•The nose starts to form•Placental blood vessels form•Endocardial (muscle) cells begins to form the two heart tubes

J. The Fetus at 6 weeks•1/2 inch long (floating in amniotic fluid)•leg buds present•spine is visible•ears are forming•at 6 weeks heart muscle starts to beat •has rapid growth at this stage•head/mouth/liver/intestines start to take shape

K. The Fetus at 7 weeks

• 3/4 inches long

• Hand/fingers are formed and moving

•eye lens form

•skull bones are visible and growing

•sexual organs are forming

•brain waves have started

•muscles develop and get stronger

L. Fetus at 8-9 weeks old

Heart Development Ends

The brain can move muscles

Sexual organs are forming

Feet become more defined

Digits are separating on hands/feet

Toe/Finger joints are visible

As you can see the fetus is in itsown sac of amniotic fluid attached tothe mother by an umbilical cordto the placenta where it gets all it’snourishment from. (Above are two twin boy fetuses in separate sacs)

M. 10 Week Old Fetus

(2 1/2 months old) Now considered a fetus• 1-2 inches long•Has a stump for a tail’• Is now very active• Facial features developed• Fingers/ Toes/ Hands/ Feet developed•Internal Organs are functioning• Nervous System is responsive: He/She can feel!

N. 11 Weeks old:

Now is 2 1/2 inches long

12 WEEKS(3 months)

•3 inches long•umbilical cord intact andis fully functional

14 WEEKS (3 1/2 months)

•3- 31/2 inches•weight is 1 ounce•muscles are developing•sex organs form•eyelids form•fingernails and toenails•spontaneous movement is observed

15-18 WEEKS( 4-4 1/2 months)

•Sensory Organs form at (15)•(16) is turning inside of MOM•(18) 5 1/2 inches•blinks, grasps, moves mouth, hair on head and body is present •all systems are developed•fetal respiration's are occurring•Must be at least 24 weeks to survive outside of womb

WEEK 22 (5 1/2 months)

•1/2 pound•10 inches long•sweat glands•external skin is turning from transparent to opaque

WEEK 26 (6 1/2 Months

•Inhales and exhales•cries•eyes are completely formed•has tongue and taste buds•has a 50% chance of survival outside of the womb with intensive Medical care

WEEK 30(7 1/2 months) (7 1/2 mo.)

•Is premature if born•But most do well if born at this time•Girls fair better than boys because their lungs are more developed.

FULL TERM (36 -40 weeks)

This is the end of normalgestation….Baby is now able to live outside of the mother’s womb.

PREMATURE BABIES(born before 36 weeks)

•May or may not have developed well enough•This is where some birth defects can occur•Difficult deliveries can cause birth trauma leading to problems•Drugs and Alcohol use can lead to premature births.•Stress or illness can cause premature birth

Premature baby at 28 weeks: 2 lbs.

Baby a yearLater:Still not outof NICU yet!

Genetic ProblemsChromosomal problems in the formation of the fetus can cause genetic problems. These children often have differences that follow them throughout their lives Drug Abuse:Is very detrimental at different stages of fetaldevelopment..they cross the placenta and cancause defects and addiction.