Stages of Fetal Development Flashcards by Aleiah Luardo

Q

From ovulation to fertilization

A

Ovum

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Q

From fertilization to implantation

A

Zygote

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Q

From implantation to 5–8 weeks

A

Embryo

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Q

From 5–8 weeks until term

A

Fetus

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Q

Developing embryo and placental structures throughout pregnancy

A

Conceptus

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Q

The earliest age at which fetuses survive if they are born is generally accepted as 24 weeks or at the point a fetus weighs more than 500–600 g

A

Age of viability

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Q

3 STAGES OF FETAL DEVELOPMENT:

A

Pre-embryonic (Zygote)
Embryonic Stage
Fetal Stage

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Q

Stage of Fetal Development

First 2 wks. (14 DAYS), beginning with
fertilization

A

Pre-embryonic (Zygote)

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Q

 union of the ovum and spermatozoon
 Other terms: conception, impregnation, or fecundation

A

Fertilization

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Q

Fertilization

 union of the ___ and ____.
 Occurs in the ____ of the _____.
 Functional life of spermatozoon – _____hrs.

A

 ovum and spermatozoon
 outer 3rd of the fallopian tube (ampulla)
 48 – 72 hrs

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Q

Stage of Fetal Development

From day 15 – 8 wks. after conception, or until the embryo measures 3 cm from crown to rump

A

Embryonic Stage

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Q

Embryonic Stage

At the end of __ wk. all _____ and _____ are present, and the ____ is unmistakably human.

A

8th; organ systems and external structures; embryo

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Q

Embryonic Stage

From day __ – _ wks. after conception, or until the embryo measures _ cm from crown to rump

A

day 15 - 8 wks after conception; 3 cm

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Q

Stage of Fetal Development

From approximately 9 wks. – term

A

Fetal Stage

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Q

Fetal Stage

Fetus less vulnerable to _____ except for those affecting CNS functioning.

A

teratogens

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Q

Period of organogenesis.

A

1st trimester

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Q

Period of rapid increase in length.

A

2nd trimester

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Q

Period of continuous growth & development.

A

3rd trimester

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Q

Intrauterine Fetal Development:

1) ___ M sperms enter the upper part of vagina, only _ M enter the uterus up to ampulla

A

300 M enter the upper part of vagina; 3 M enter the uterus up to ampulla

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Q

Intrauterine Fetal Development:

2) Sperm penetrate the _____ by releasing an enzyme ______ (FERTILIZATION)

A

zona pellucida; hyaluronidase

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Q

Intrauterine Fetal Development:

3) Nuclei of ___ & ___ fuse, _______ combine

A

ovum & sperm; chromosomes

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Q

Intrauterine Fetal Development:

4) After the nuclei of ovum & sperm fuse, chromosomes combine, the ____ forms.

A

Zygote

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Q

Intrauterine Fetal Development:

5) ____ begins to form as zygote travels the uterine tube Into the uterus (Blastomeres)

A

Cleavage

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Q

Intrauterine Fetal Development:

6) _____ (16-CELL MASS) is produced within 3 days, Still surrounded by zona pellucida

A

Morula

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Intrauterine Fetal Development: 7) Morula enters the __________.

uterine cavity

Intrauterine Fetal Development: 8) _____ forms at the center of morula, while ZONA PELLUCIDA remains the same size

Blastocele

Intrauterine Fetal Development: 9) _____ forms after blastocele.

BLASTOCYST

Intrauterine Fetal Development: 10) Blastocyst hatches from the ______ ( _ day after fertilization) as it enters the uterus

zona pellucida; 6th day

Intrauterine Fetal Development: 11) _____ occurs after blastocyst hatches from the zona pellucida ( _ to _ days after fertilization).

Implantation; 8-10 days

Intrauterine Fetal Development: 12) ____ cells secretes an enzyme ( _____ ) which erodes the epithelial uterine lining

Trophoblast; strypsin

Intrauterine Fetal Development: 13) Trophoblast cells engulf & destroy cells of the _____.

uterine lining

Intrauterine Fetal Development: 14) New _____ grow, foretelling the growth of the _____.

capillaries; placenta

Intrauterine Fetal Development: 15) After implantation, the endometrium is termed ____.

decidua

Intrauterine Fetal Development: 16) ____ (inner cell mass) forms 2-layered disc.

Embryoblast

Intrauterine Fetal Development: 17) ____ develops from trophoblast and contains _____ on its surface.

Chorion; chorionic villi

Intrauterine Fetal Development: 18) ____ burrow into the decidua basalis

Villi

Intrauterine Fetal Development: 19) As villi burrow into the decidua basalis, the formation of _____ starts to develop.

placenta

Intrauterine Fetal Development: 20) Chorion becomes the covering of the side ___ of the placenta (contains major umbilical blood vessels).

fetal

Intrauterine Fetal Development: 21) ____ develops from the inner cell mass of the blastocyst

Amnion

Intrauterine Fetal Development: 22) Developing ____ draws the amnion around itself to form a ______.

embryo; fluid-filled sac

Intrauterine Fetal Development: 23) Amniotic cavity derives its fluid by _____ from the ______.

diffusion; maternal blood

Intrauterine Fetal Development: 24) ____ is also formed.

Yolk sac

Intrauterine Fetal Development: 25) _____ & _____ are manufactured in the yolk sac (2nd - 3rd wk.)

Blood cells & plasma

Intrauterine Fetal Development: 26) ___ begins to beat & circulate blood through the embryo, connecting ____, ____ & ____ sac (end of 3rd wk.)

Primitive; stalk, chorion & yolk sac

Intrauterine Fetal Development: 27) Part of _____ incorporated into the embryo’s body as the primitive GIT (4th wk.)

yolk sac

Intrauterine Fetal Development: 28) Connecting stalk forms the _____ (5th wk.)

umbilical cord

Intrauterine Fetal Development 300 M sperms enter the _____, only 3 M enter the ___ up to _____.

upper part of vagina; uterus up to ampulla

BLASTOCYST 2 cell types are forming:

1) Embryoblast 2) Trophoblast

BLASTOCYST (cell inside the blastocele)  Give rise to the embryo

Embryoblast

BLASTOCYST (cell outside the blastocele)  Give rise to the placenta

Trophoblast

When does the blastocyst hatch from the zona pellucida?

6th day after fertilization

When does implantation occur?

8-10 days after fertilization

1) portion directly under the blastocyst

Decidua basalis

2) portion covering the blastocyst

Decidua capsularis

3) portion lining the rest of the uterus

Decidua vera

Embryoblast (inner cell mass) forms 2-layered disc:

1) Top layer 2) Lower cells

becomes the embryo & amniotic cavity

Top layer

become the yolk sac

Lower cells

A Blastocyst is considered an Embryo when ______. How many days after fertilization?

the amniotic sac develops; 10 – 12 days after fertilization

Functions of Amniotic Fluid: (5) 1) Helps maintain a _______ 2) Source of _____ & a _____ for waste 3) ______ the fetus from trauma from the outside forces 4) Allows ______ for musculoskeletal development 5) Keeps the embryo from _______, facilitating symmetric growth of the fetus

1) Helps maintain a constant body temp. 2) Source of oral fluid & a repository for waste 3) Cushions the fetus from trauma from the outside forces 4) Allows freedom of movement for musculoskeletal development 5) Keeps the embryo from tangling with the membranes, facilitating symmetric growth of the fetus

Volume of amniotic fluid: 12 wks. = ?

50 ml

Volume of amniotic fluid: 14 wks. = ?

100 ml

Volume of amniotic fluid: 16 wks. = ?

175 ml

Volume of amniotic fluid: 18 wks. = ?

250 ml

Volume of amniotic fluid: 20 wks. = ?

325 ml

Volume of amniotic fluid: Term = ?

800 - 1,200 ml

↓300 ml

oligohydramnios; assoc. with renal abnormalities

↑2 L

hydramnios; assoc. with GIT & other malform.

Connecting stalk forms the umbilical cord (5th wk.) Contains: _ arteries (_____) & _ vein (_____) Diameter: _ cm at term Length: __ – __ cm (ave. 55 cm.)  ____ jelly

Contains: 2 arteries (deoxygenated) & 1 vein (oxygenated) Diameter: 2 cm at term Length: 30 – 90 cm (ave. 55 cm.) Wharton’s jelly

DEVELOPMENT OF PLACENTA 1) On the __ or __ day, the ____ villi start to form from the ____ villi that protrude from a single layer of cells to start the formation of ____.

11th or 12th day; chorionic villi start to form from the miniature villi; placenta

DEVELOPMENT OF PLACENTA 2) The chorionic villi have a ____ and _____, and a double layer of _____.

central core and fetal capillaries, and a double layer of trophoblast cells.

DEVELOPMENT OF PLACENTA 3) Placenta begins to form at _____.

implantation

DEVELOPMENT OF PLACENTA 4) Chorionic villi grow into the spaces with 2 layers of _____ cells:

TROPHOBLAST

DEVELOPMENT OF PLACENTA 5) 3rd layer develops into _______, dividing the projecting decidua into _____.

anchoring septa; cotyledons

DEVELOPMENT OF PLACENTA 6) In each of the __ to __ cotyledons, the chorionic villi branch out and ______ form

15-20; fetal blood vessels

DEVELOPMENT OF PLACENTA 7) Placenta is complete by __ wk.

12th

Chorionic villi grow into the spaces with 2 layers of TROPHOBLAST cells:

1) Outer syncytium (functional layer of the placenta) 2) Inner cytotrophoblast

produces placental hormones such as hPL, hCG, estrogen, and progesterone.

1) Outer syncytium (functional layer of the placenta)

• The Langhans’ layer is the middle layer and it protects the embryo and fetus from infectious diseases. This layer appears to function as early as 12 days’ gestation. • The layer disappears on the 20th to 24th week of gestation, however, leaving the fetus more susceptible to infections.

2) Inner cytotrophoblast

The _____ is the middle layer and it protects the embryo and fetus from infectious diseases. This layer appears to function as early as __ days’ gestation.

Langhans’ layer; 12

The Langhans' layer disappears on the __ to __ week of gestation, however, leaving the fetus more susceptible to infections.

20th to 24th week

Functions of the Placenta: 1) As an endocrine gland that produces 4 hormones to maintain pregnancy (produced in syncytium)

a) Human Chorionic Gonadotropin (hCG) b) Chorionic Somatomammotropin (human placental lactogen) c) Progesterone d) Estrogen

 Preserves the function of the corpus luteum, ensuring continued supply of estrogen & progesterone needed to maintain pregnancy  Suppresses maternal immunologic response so that placental tissue is not detected and rejected as a foreign substance.

a) Human Chorionic Gonadotropin (hCG)

 Similar to GH  Stimulates maternal metabolism to supply needed nutrients for fetal growth  Increases resistance to insulin  Facilitates glucose transport across the placental membrane (facilitated diffusion).  Stimulates breast development to prepare for lactation.

b) Chorionic Somatomammotropin (human placental lactogen)

 Maintains the endometrium.  Decrease contractility of uterus  Stimulates the development of breast alveoli & maternal metabolism

c) Progesterone

 Stimulates uterine growth and uteroplacental blood flow.  Causes proliferation of the breast glandular

d) Estrogen

a) Human Chorionic Gonadotropin (hCG)  Preserves the function of the ______, ensuring continued supply of _____ & _____ needed to maintain pregnancy

corpus luteum; estrogen & progesterone

a) Human Chorionic Gonadotropin (hCG)  Suppresses _______ so that placental tissue is not detected and rejected as a foreign substance.

maternal immunologic response

b) Chorionic Somatomammotropin (human placental lactogen)  Stimulates ______ to supply needed nutrients for fetal growth

maternal metabolism

b) Chorionic Somatomammotropin (human placental lactogen)  Increases resistance to ____.

insulin

b) Chorionic Somatomammotropin (human placental lactogen)  Facilitates ______ across the placental membrane (facilitated diffusion).

glucose transport

b) Chorionic Somatomammotropin (human placental lactogen)  Stimulates _______ to prepare for lactation.

breast development

c) Progesterone  Maintains the ____.

endometrium

c) Progesterone  Decrease _____ of uterus

contractility

c) Progesterone  Stimulates the development of _____ & ______.

breast alveoli & maternal metabolism

d) Estrogen  Stimulates _____ and _______.

uterine growth and uteroplacental blood flow

d) Estrogen  Causes _____ of the breast glandular

proliferation

d) Estrogen secreted by the placenta

Estriol

d) Estrogen produced by ovaries

Estradiol

2) Metabolic Functions of the Placenta: (4)

a) Respiration b) Nutrition c) Excretion d) Storage

Mechanisms by which nutrients cross the placenta: (4)

1. Diffusion 2. Facilitated diffusion 3. Active transport 4. Pinocytosis

Mechanisms by which nutrients cross the placenta: -O2, CO2, sodium, chloride -substances cross a semipermeable membrane from an area of higher conc. to an area of lower conc.

Diffusion

Mechanisms by which nutrients cross the placenta: -glucose -a carrier moves a substance across a membrane.

Facilitated diffusion

Mechanisms by which nutrients cross the placenta: -essential amino acids, water-soluble vitamins -a substance cross from an area of lower conc. to an area of higher conc. with the aid of energy and action of enzyme.

Active transport

Mechanisms by which nutrients cross the placenta: -gamma globulins, lipoproteins, phospholipids; virus -cross the placenta through absorption by the cellular membrane

Pinocytosis

A narrow line of cells appears on the surface of the embryonic disc, forming the _______.

3 GERM LAYER

It is more concentrated and has greater oxygen affinity, two features that increase its efficiency.

FETAL HEMOGLOBIN

Because hemoglobin is more concentrated, a newborn’s hemoglobin level is about _______ compared with a normal adult level of ______.

17.1 g/100 ml; 11 g/100 ml

a newborn’s hematocrit is about __ compared with a normal adult level of __.

53%; 45%

In contrast to the adult RBC lifespan of ___ days, the lifespan of the neonatal erythrocyte is only __ to __ days with preterm infants having an even shorter life span of __ to __ days.

120; 60 to 90; 35 to 50 days

_____ has a tendency to denature and damage the membrane from within, contributing to the shortened the red cell lifespan.

Hb F

FETAL DEVELOPMENT • LENGTH: 25 cm. • WEIGHT: 223 gm • Quickening present • Hair & eyebrows • formed • Meconium present in upper intestine • Vernix caseosa forms • Definite sleeping patterns develop

5 MONTHS (17 – 20 wks.)

FETAL DEVELOPMENT • LENGTH: 28 – 36 cm; • WEIGHT: 550 gm • Passive antibody transfer • Meconium present in the rectum • Start of surfactant production • Eyelids open • Pupils reactive to light • Well-defined eyebrows & eyelashes • Capable of hearing sounds

6 MONTHS (21 – 25 wks.)

FETAL DEVELOPMENT • LENGTH: 35 – 38 cm. • WEIGHT: 1,200 gm • Alveoli matures • Surfactant present in amniotic fluid • Testes begins to descend • Retinal blood vessels are thin and extremely susceptible to damage.

7 MONTHS (26 – 29 wks.)

FETAL DEVELOPMENT • LENGTH: 38 – 43 cm; • WEIGHT: 1,600 gm • Deposition of brown fat • Fetus responds to external voice • Active moro reflex present • Iron stores develop • Fetus assumes birth position

8 MONTHS (30 – 34 wks.)

FETAL DEVELOPMENT • LENGTH: 43 – 48 cm. • WEIGHT: 1,800 – 2,700 gm • Body stores glycogen, iron & carbohydrates. • Calcium deposition • Deposition of subcutaneous fats • Presence of 1 – 2 creases on sole of foot • Decrease in lanugo

9 MONTHS (35 – 37 wks.)

FETAL DEVELOPMENT • LENGTH: 48 – 52 cm; • WEIGHT: 3,000 gm • Fetus kicks actively • Start conversion of fetal hemoglobin to adult • Vernix caseosa fully formed • Sole creases cover 2/3 of feet • Lightening may be present.

10 MONTHS (38 – 40 wks.)

• LENGTH: 7 – 8 cm. • WEIGHT: 45 gm • Nailbeds formed • Formation of bone ossification centers • Tooth buds present • Heartbeat audible by Doppler • Kidney secretion starts

3 MONTHS (9 – 12 wks.)

• LENGTH: 10 – 17 cm; • WEIGHT: 55 - 120 gm • Fetal heart audible by stethoscope • Lanugo well formed • Functional liver & pancreas • Fetus swallows amniotic fluid • Urine present in amniotic fluid • Sex determined by ultrasound

4 MONTHS (13 – 16 wks.)

• LENGTH: 0.75 – 1 cm • WEIGHT: 400 mg • Spinal cord fused & at midpoint • Rudimentary heart appears as a bulge on the anterior surface • Extremities appear as buds • Discernible eyes, ears, nose

1 MONTH (1 – 4 wks.)

2 MONTHS (5 – 8 wks.) LENGTH: 2.5 cm; WEIGHT: 20 gm Completed organogenesis Heart with septum beats rhythmically Facial features discernible Extremities developed External genitalia present but cannot be distinguished U/S shows gestational sac