Care of Developing Fetus

Ovum

from ovulation to fertilization.

Zygote

from fertilization to implantation

Fetus

from 8 weeks until term

Conceptus

developing embryo and placental structures throughout pregnancy

Age of viability

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

Fertilization

union of an ovum and spermatozoon. referred to as conception, impregnation or fecundation.

outer third of the fallopian tube, ampullar portion

where fertilization occurs

24-48 hours

Viability of ovum

48-72 hours

Spermatozoon life span

2.5ml of fluid containing 50-200 million spermatozoa per ml or an average of 400 million sperm cells per ejaculation

average semen ejaculation

Graafian follicle

Where the ovum is released in the ovary

zona pellucida and corona radiata

protective structures surrounding primary oocyte

zona pellucida

a protective mucopolysaccharide layer which is a thick, transparent coating rich in glycoproteins that surrounds an oocyte.

corona radiata

The layer of granulosa cells that surround an oocyte after is has been ovulated.

fimbriae

hairlike structures at the fallopian tube openings, create currents to propel the ovum into the fallopian tube.

3-4 days

how many days does the zygote travels from the ampulla of the fallopian tube to the uterus

morula stage

the zygote undergoes mitotic cell division with 16-50 undifferentiated cells.

blastocyst

A fluid-filled sphere formed about 5 days after fertilization of an ovum that is made up of an outer ring of cells and inner cell mass. This is the structure that implants in the endometrium of the uterus and differentiates into three germ layers.

ectoderm, mesoderm, endoderm

3 primary germ layers of embryo

Ectoderm

outermost germ layer; produces sense organs, Adrenal Medulla, nerves, and outer layer of skin

Mesoderm

middle germ layer; develops into Kidneys and Ureters, Reproductive System, Bone & Cartilage, Muscles, Vasculature, Lymphatics, Spleen Adrenal Cortex

Endoderm

the inner germ layer that develops into the lining of the digestive and respiratory systems, Liver, Bladder, and Urethra

trophoblast

The outer layer of cells that develops in the germinal period. These cells provide nutrition and support for the embryo. forms the placenta and other support structures.

corpus luteum

Endocrine tissue which produces hormones, estrogen, and progesterone which prepares the uterine lining for receiving an embryo

human chorionic gonadotropin (hCG)

trophoblast absorbs nutrients from the endometrium and secretes what to maintain the corpus luteum

Cytotrophoblast (inner layer)

Proliferates upon implantation, forming primary chorionic villi used in early genetic testing (chorionic villus sampling).

Syncytiotrophoblast (outer layer)

Supports the cytotrophoblast and facilitates nutrient, waste, and gas exchange between maternal and fetal systems.

Implantation

contact between the growing structure and the uterine endometrium that occurs between 8-10 days after fertilization (or about 8 days after ovulation)

Decidua

specialized layer of endometrium that forms the base of the placental bed. most ideal site for implantation

prolactin, renin, corticotrophin releasing hormone (CRH), growth hormone, prostaglandin, oxytocin, and endothelin-1

hormones released by decidua

•Decidua vera or parietalis-

•Decidua basalis or placentalis

Decidua capsularis-

Layers of Decidua:

Decidua vera or parietalis

the remaining portion of the uterine lining

Decidua basalis or placentalis

forms the maternal portion of the placenta

Decidua capsularis

the layer which encloses the blastocysts after implantation

Chorionic villi

tiny projections of placental tissue that look like fingers and contain the same genetic material as the fetus. allow for the absorption of gases and nutrients from the maternal blood supply while eliminating fetal waste

Chorionic frondosum

villi at the embryonic pole in contact with decidua basalis. Later form the fetal side of the placenta

Chorion leave "bald chorion"

villi not involved with implantation that gradually degenerates, becoming thin and eventually forming the chorionic membrane

Fetal membrane

surrounds the fetus during pregnancy and is a thin tissue composed of two layers, the chorion and the amnion.

Chorion

among the vital membranes that form the amniotic sac. has tail-like structures (chorion villi) for providing extra protection to the embryo. facilitates the exchange of nutrients between the mother and child during the pregnancy period.

Amnion

contains a thin transparent fluid called amniotic fluid in which the embryo is suspended

Amniotic Fluid

acts as a cushion and protects the fetus from any mechanical jerks. It maintains even pressure and protects the fetus from damage. composed of 99% water and 1 % solid particle

ranges from 500-1200 ml averaging at 1000ml.

Amniotic Fluid volume range

7.00-7.25

Amniotic fluid pH

1.005-1.025

specific gravity of amniotic fluid

Amniotic Fluid

contains albumin, urea, uric acid, creatinine, lecithin sphingomyelin, bilirubin, minerals and suspended materials such as desquamated epithelial cells and vernix caseosa.

Umbilical Cord

originated from the yolk sac and umbilical vessels. connects the fetus to the placenta (carry oxygen and nutrients to the placenta and return oxygenated blood and fetal waste products to the placenta).

Wharton's jelly

gelatinous substance within the umbilical cord, largely made up of mucopolysaccharides to insulate and protect the umbilical cord

Thomas Wharton.

DIscovered Wharton's jelly

50-55 cm long and 2cm in diameter

length of the umbilical cord

350ml/min

rate of blood flow at term

Short cord

Intrapartum hemorrhage due to premature separation of the placenta

Delayed descent of the fetus during labor

Inversion of the uterus

Long cord

Cord presentation

Coiling of the cord around the neck

True knots of the cord

Placenta

A structure that allows an embryo to be nourished with the mother's blood supply. formed from the chorionic villi and decidua basalis. Temporary endocrine organ. Weighing approximately 500 grams at term with a diameter of 15-20cm and 3 cm thick.

700-900ml

Uteroplacental blood flow at term

cotyledons

attaches to the mothers uterine wall. This side is dark red in color and is made up of many lobes (15-20) which adheres to the uterus and connect with mother's circulation.

Zygote growth

development proceeds cephalo-caudal (head-to-tail) direction

Cardiovascular System

one of the 1st systems to become functional in intrauterine life.

single heart tube

forms as early as the 16th day of life and beat as early as 24th day.

6th or 7th week

Septum that divides the heart into chambers develop during

After 28th week

week when sympathetic nervous system matures, the heart rate stabilizes and a consistent heart rate of 110-160 beats/min

Fetal Circulation

fetus derives oxygen and excretes carbon dioxide not from gas exchange in the lungs but from exchange in the placenta

Foramen ovale

connects the left & right atrium, bypassing the lungs

fossa ovalis

remnant of foramen ovale of fetal heart

Umbilical vein

brings oxygenated blood coming from the placenta to the heart and liver

round ligament (ligamentum teres hepatis)

Remnant structure of umbilical vein

Umbilical arteries

carry deoxygenated blood from the fetus to the placenta. Its obliterated portion will become umbilical ligaments

Ductus venosus

carry oxygenated blood from umbilical vein to inferior vena cava, bypassing the fetal liver

ligamentum venosum or Arantius ligament.

remnant of ductus venosus

Ductus arteriosus

carry oxygenated blood from pulmonary artery to aorta bypassing fetal lung.

ligamentum arteriosum

remnant of ductus arteriosus

Respiratory System

at 3rd week of intrauterine life, exist as a single tube along with the digestive tract

4th week

by the end of what week will a septum begin to divide the esophagus from the trachea.

24th week of pregnancy

Surfactant, a phospholipid substance, is formed and excreted by the alveolar cells of the lungs beginning approximately

lecithin & sphingomyelin

2 components of surfactant

2:1

35 weeks there is a surge in the production of lecithin, which then becomes the chief component by ratio of

8th week

Brain waves can be detected on electroencephalogram by what week

24 weeks

by what week is the ear capable of responding to sound, and the eyes exhibit a pupillary reaction, indicating sight is present

neural plate

3rd week, what becomes apparent? its top portion differentiates into the neural tube, which will form the CNS and the neural crest

Endocrine System

function begins along with neuro system development

6th week

by what week will the intestine become too large to be contained by the abdomen

32 weeks or weighs 1500 grams

swallowing and sucking reflex are not mature until about

meconium

by the 16th week, a collection of cellular wastes, bile, fats mucoprotein, mucopolysaccharides and portions of vernix caseosa, accumulates in the intestines. It is sticky in consistency and appears black or dark green

26 weeks

by what week does fetus begin to store brown fats to be utilized as a source of heat in the 1st hours after birth

36 weeks

at what week does GI secretes enzymes necessary for digestion of CHO, CHON

Fetal Liver

stores glycogen at week 9. Cannot synthesize coagulation factors because of lack of vitamin K

Pancreas

Originate from the foregut and is formed between 5th & 8th weeks.

12th week

Islets of Langerhans develop at what week

20 weeks

Fetus produces insulin beginning at what week

11th week

Fetus can be seen to move on ultrasonography as early as

12th week.

Ossification (natural process of bone formation) of the cartilage into bone begins at abou

4 weeks

at what week does a part of the mesoderm gives rise to the bones and muscles

13 weeks

skeleton begins to calcify at what week

8 weeks

Child's sex can be ascertained as early as __ by chromosomal analysis of fetal cells in the mother's blood stream

34-38 weeks of gestation

testes 1st form in the abdominal cavity and do not descend into the scrotal sac until

Urine

formed by the 12th week and is excreted into the amniotic fluid by the 16th week of gestation

500ml/day

At term, fetal urine is excreted at a rate of up to

oligohydramnios

too little amniotic fluid. Suggests fetal kidneys are not secreting adequate urine and that there is a kidney, ureter or bladder disorder

36 weeks

skin of fetus appears thin and almost translucent until subcutaneous fat begins to be deposited underneath it at about

vernix caseosa

important for lubrication and for keeping the skin from macerating in utero.

lanugo

Skin is covered by soft downy hairs that serve as insulation to preserve warmth in utero