Prenatal Growth from Conception to Birth Fetal Development Prenatal Growth from Conception to Birth These are my notes 11/22/2018 Fetal Development

Outline of Topics Conception •Sperm •Ovum Zygotic Period •Conception - 1st week Embryonic Period •2nd week - 2nd month Early Fetal Period •3rd - 6th month Later Fetal Period •7th - 9th month/birth 11/22/2018 Fetal Development

Key Terms Conception Sperm Ovum Zygote Mitosis Embryo Ectoderm Mesoderm Endoderm Congenital Malformations Fetus 11/22/2018 Fetal Development

Conception Conception occurs when the sperm meets and penetrates the ovum, or egg Also known as fertilization 11/22/2018 Fetal Development

Sperm Sperm is the male reproductive cell Chief Characteristics: Tightly packed tip (acrosome) that contains 23 chromosomes that carry genetic information Short neck region Trail to propel it in its search for the ovum Microscopic One of the smallest cells in the male body 11/22/2018 Fetal Development

Sperm Facts Remains capable of fertilizing egg for 24-48 hours after ejaculation Of 200 million sperm that enter the vagina, only about 200 survive the journey to the fallopian tubes, where fertilization occurs Males, at birth, have in their testes those cells that will eventually produce sperm 11/22/2018 Fetal Development

Ovum (Egg) The ovum is the female reproductive cell Chief Characteristics: Round .01 mm in diameter Consistency of stiff jelly Contributes 23 chromosomes Barely visible to the naked eye 11/22/2018 Fetal Development

Ovum (Egg) Facts Females already have 1-2 million primal eggs at birth Eggs usually fertilized about 12 hours after discharged from the ovary or they die within 12-24 hours 11/22/2018 Fetal Development

Zygotic Period (Conception - 1st Week) A zygote is a fertilized egg with 46 chromosomes Genetic potential determined at this time Egg is 2.5 mm in diameter at end of 1st week Mitosis, a process of cell division, occurs during this period 11/22/2018 Fetal Development

Rejection from the body A variety of reasons cause about 50% of fertilized eggs to spontaneously abort during this period Reasons include: Rejection from the body Continuance of ingestion of drugs or alcohol by mother (usually unaware of pregnancy at this time) 11/22/2018 Fetal Development

Embryonic Period (2nd Week - 2nd Month) The differentiation of embryonic cells into layers marks the beginning of the embryo, or embryonic period Period when all body systems form Highly sensitive for susceptibility of congenital malformations, or abnormal conditions with which an infant is born 11/22/2018 Fetal Development

3 Layers of Cells in the Embryonic Period: Ectoderm--sense organs and nervous system develop from this layer Mesoderm--accounts for formation of muscular, skeletal, circulatory systems Endoderm--eventually accounts for formation of digestive and glandular systems 11/22/2018 Fetal Development

Embryonic Period: End of the 1st Month 1/4 inch (6 mm) long 1 oz. Weight Crescent-shaped with small limb buds on sides Tail with tiny ridges Rudimentary circulatory system is forming Heart begins to beat Growth acceleration 11/22/2018 Fetal Development

Embryonic Period: End of 2nd Month 1.5 inches long Beginning of face, neck, fingers, toes develop Limb buds lengthen Muscles enlarge Sex organs begin to form Rapid brain development Embryo is firmly planted on uterine wall and is receiving nourishment from placenta and umbilical cord 11/22/2018 Fetal Development

Early Fetal Period (3rd - 6th Month) Period of the fetus begins around the 3rd month and continues until delivery Movement first becomes apparent to mother at this time No new anatomical features appear during this period, yet still critical time 11/22/2018 Fetal Development

Early Fetal Period: 3rd Month Rapid growth, 3 inches long at end of 3rd month Sexual differentiation continues Teeth buds emerge Stomach and kidneys begin to function Vocal cords appear Reflex actions felt: opens/closes mouth, clenches fist, sucks thumb 11/22/2018 Fetal Development

Early Fetal Period: 4th Month Most rapid growth rate (doubles in length to 6-8 inches) 6 oz. Weight Hands fully shaped Bony tissue begins to form 11/22/2018 Fetal Development

Early Fetal Period: 5th Month Reaches 1/2 of birth length (8-10 inches) Only 10% of birth weight (1/2 lb.) Skin, hair, nails appear Internal organs grow and assume proper anatomical positions Pigmented hair on head and eyebrows appears 11/22/2018 Fetal Development

Early Fetal Period: 6th Month 13 inches long 1 lb. Weight Eyelids reopen and are completed Structurally complete but functionally immature 11/22/2018 Fetal Development

Later Fetal Period (7th - 9th Month/Birth) From the 7th month to birth, the fetus triples in weight This is a period of filling out Preparation for birth 11/22/2018 Fetal Development

Later Fetal Period: 7th Month A layer of adipose tissue begins to form under skin (serves as both insulator and food supplier) Rapid 2-4 lb. Weight gain 14-16 inches long Fetus is quiet for long periods of time Brain more active and is increasing control over body systems 11/22/2018 Fetal Development

Later Fetal Period: 8th Month Fetus is more active (frequent changes in position) Fatty deposits distributed 16-18 inches long 4-6 lbs. 11/22/2018 Fetal Development

Later Fetal Period: 9th Month (Birth) 19-21 inches long 6-8 lbs. Birth process is initiated by placenta and contraction of uterine muscles Birth generally occurs after week 40 of gestation (normal is 38-42 wks.) Find out more about birth at: Childbirth.org 11/22/2018 Fetal Development

Review Activity Now it is time to test your new knowledge on Fetal Development! Click the arrow above to view and print a “Review Activity” worksheet. The next five slides will show only pictures and brief descriptions of each of the five periods of development in random order. Your job is to write down the letter of the slide next to the corresponding stage on the worksheet. We will go over the answers at the end of the lesson. Good luck! 11/22/2018 Fetal Development

A. Movement first becomes apparent to the mother Fetus begins to suck it’s thumb Skin, hair, and nails appear No new anatomical features during this period, yet still a critical time 11/22/2018 Fetal Development

B. The sperm meets and penetrates the ovum, or egg 11/22/2018 Fetal Development

C. The differentiation of embryonic cells into layers marks the beginning of this period Highly susceptible period for congenital malformations Heart begins to beat Beginnings of face, neck, fingers, toes develop 11/22/2018 Fetal Development

D. Genetic potential determined during this period Mitosis occurs 50% of fertilized eggs spontaneously abort at this time 11/22/2018 Fetal Development

E. Fetus triples in weight Period of filling out and preparation Rapid weight gain More active 11/22/2018 Fetal Development

Answers: How did you do? 1. Conception B 2. Zygotic Period D 3. Embryonic Period C 4. Early Fetal Period A 5. Later Fetal Period E Good Job! 11/22/2018 Fetal Development

References Dacey, J.S. & Travers, J.F. (2002) Human Development Across the Lifespan. McGraw Hill. New York Gallahue, D.L. & Ozmun, J.C. (2002) Understanding Motor Development. McGraw Hill. New York Fetal Development Overview: http://www.w-cpc.org/fetal.html Conception Icon: http://warmcat.com/milksop/conception.jpg Ovum Icon: http://www.advancedfertilityservices.com/ Sperm Icon: http://www.hc.cc.tx.us/san_angelo/departments/general_studies/Biology/Images/sperm.jpg 11/22/2018 Fetal Development

Review Activity 1. Conception 2. Zygotic Period 3. Embryonic Period 4. Early Fetal Period 5. Later Fetal Period 11/22/2018 Fetal Development