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What is the Preembryonic Stage?
Fertilization through the second week
- blastocyte-trophoblast- implantation
What is Embryonic stage?
- end of second week through the eight week
- -basic structures of major body organs and exteran features
What is Fetal Stage?
end of eighth week until birth
What is the clear protein layer that protects a single sperm inside the ovum? How long does it last?
- zona pellucida
- Disappears in 5 days.
What is a zygote?
How long does it take to travel through the fallopian tubes?
- 1.when sperm and ovum combine to form diploid
- 2. travels through fallopian tubes to uterus
- 3.divides by mitoses (cleavage) and all cells are identical
1. 3-4 days
Where does fertilization take place?
In outer third ampulla of the fallopian tube
Name the three embryonic layers of cells
Ectoderm- forms CNS, special senses, skin, and glands
Mesoderm-forms skeletal, urinary, circulatory, and reproductive organs
Endoderm-forms respiratory system, liver,pancreas, and digestrive system
What is a morula?
Mass of 16 cells
What is a inner mass cell?
Blastocyte- forms the embryo and amnion
What is the outer mass cell?
trophoblast- forms the placenta and chorion
How long does it take for sperm to reach the fallopian tubes?
5 minutes after intercourse
How long can sperm awat the ovum? How long can Ovum survive?
- 3-5 days (sperm)
- 24 hours (ovum)
what occurs from the Blastocyst-Trophoblast stage?
- 3-4 more days until implants in endometrium
- Now called blastocyst
- Outside layer of blastocys made up of cells called tropho blasts
What forms the placenta in early pregnancy?
chorionic villi, imbed into endometrium and form the placenta
How long does it take for implantation to occur?
What is hCG?
Human chorionic gonadotropin- hormone preserves copus lteum and its progesterone production in order to maintain uterine lining, basis for urine and serum pregnancy tests
What does Estrogen do during pregnancy?
- causes enlargement of breasts, uterus, external genitalia,
- stimulates myometrial contractillity
What is the role of progesterone in pregnancy?
- maintains endometrium
- decreases contractillity of the uterus
- provides nourishment for early conceptus
What is the role of Relaxin?
- 1.acts synergistically with progesterone to maintain pregnancy
- 2.causes relaxation of pelvic ligaments and softens cervix to prepare for delivery
Describe Fetal development at week 3
- development of:
- Spinal cord
- Nerual tube forms
- GI tract
- Leg and arm buds appear and grow out of body
What occurs during week 4 of fetal development
- Brain differentiates
- limb buds grow and develop more
What occurs during week 5 of fetal development?
- heart now beats at reg rhythm
- Beginning structures of eyes and ears
- some visible cranial nerves
- muscles become innervated
Descibe what occurs durrin week 6 of fetal development
- Lungs begin to form
- fetal circulation is established
- Liver produces RBCs
- Further develpment of brain
- Primitive skeleton forms
- CNS forms
- Brain waves detectable
What occurs during week 7 of fetal development?
- Straightening of trunk
- nipples and hair follicles form
- elbows and toes visible
- arems and legs move
- diaphragm formed
- mouth with lips and early tooth buds
What occurs during week 8 of fetal development?
- Rotation of intestines
- facial features develop
- Heart development is complete
- Resembles Human being
What occurs in weeks 9-12 of fetal development?
- sexual differentiation continues
- buds for all 20 temp teeth laid down
- digestive system shows activity
- head comprises nearly half of fetus size
- face and neck well formed
- urogenital tract completes development
- RBC produced in liver
- Urine begins to be produced and excreted
- fetal gender can be determined by 12 weeks
- lims are long thin, digits are well fomred
What occurs durring weeks 13-16 of fetal development
- Lanugo (fine hair) develops on the head
- fetal skin is almost transparent
- bones become harder
- fetus makes active movements
- sucking motions are made with the mouth
- amniotic fluid is swallowed
- fingernails and toenails present
- weight quadruples
- fetal movement or QUICKENING detected by mother
What occurs weeks 17-20 during fetal development
kidneys continue to secret urine into amniotic fluid
- rapid brain growth
- Fetal heart tones can be heard with stethoscope
vernix caseosa, white greasy film covers fetus
- eyebrows and head hair appear
- brown fat deposited to help maintain temp
- nails present on both fingers and toes
- muscles well developed
What occurs during week 21-24 fetal development?
Eyebrows and eyelashes well formed
fetus has hand grasp and startle reflex
alveoli forming in lungs
skin is translucent and red
lugns begin to produce surfactant
What occurs during week 25-28 of fetal development?
Fetus reaches 15 inches in length
rapid brain development
eyelids open and close
nervous system controls some functions
fingerprints are set
blood formation shifts from spleen to bone marrow
fingerprints are set
blood formations shifts from spleen to bone marrow
fetus usually assumes head down postion
What occurs during weeks 29-32 of fetal development?
Rapid increase in amount of body fat
Increased CNS control of body functions
Rhythmic breathing movements occur
Lungs are not fully mature
Fetus stores Iron, calcium and phosphorus
What occurs during weeks 33-38 of fetal development?
Testes are in scrotum of male fetus
Lanugo begins to disappear
Increase in body fat
Fingernails reach the end of fingertips
Small breast buds are present on both sexes
Mother supplies fetus with antibodies against disease
Fetus isconsidered full term at 38 weeks
Fetus fills uterus
What is the concern of oligohydraminos?
(Too little amniotic fluid) <500mL at term
fetal renal abnormalities
What is the concernt of hydraminios?
(Excessive amniotic fluid) >2,000mL at term
neural tube defects
chromosomal deviations and malformations of CNS and/or Gi tract that prevents normal swallowing of amniotic fluid by the fetus
What are the important components of the fetal blood supply?
AVA- Artery Vein Artery
Wharton's jelly- specialized connective tissue surrounds the three vessels preventing compression, which would cut off fetal blood and nutrient supply
What is Monozygotic Vs Dizygotic twins?
Monozyogic- comes from one zygote that separtes, produces identical twins
Dizygotic twins- comes from 2 separate zygotes, the individuals are different and not identical
What is the Chorion?
Thick outside layer of amniotic sac
adjacent to maternal surface of placenta