Week 3

Gametogenesis

meiosis occurs during this period, the process by which germ cells or gametes are produced

diploid

The gametes must have a ______ number (23) of chromosomes so that when the female gamete (egg or ovum) and the male gamete (sperm or spermatozoa) unite to form the zygote (fertilized egg), the normal human diploid number of chromosomes (46) is reestablished

Pre-embryonic stage

first 2-3 weeks, beginning with fertilization

Embryonic stage

week 4-8 weeks gestation

Fetal stage

9 weeks to birth

ovum

from ovulation to fertilization

zygote

from fertilization to implantation

embryo

from implantation to 5-8 weeks

fetus

from 5-8 weeks until term

conceptus

developing embryo and placental structures throughout pregnancy

Age of viability

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

fertilization

the beginning of pregnancy

• also referred to as conception and impregnation

• is the union of an ovum and a spermatozoa

ampullar

fertilization occurs at the ____ portion of fallopian tube

24 hours (48 hours at the most)

Once the mature ovum is released, fertilization must occur fairly quickly because an ovum is capable of fertilization for only about ___ hours

48-72 hours

Sperms survive only within _____ hours

2.5 ml

Average conduct per ejaculation is __ ml or 50-400 million

graffian follicle

Ovum is released from the _______ _____ of an ovary

peristalsis

During ovulation, high estrogen levels increase ______ in the fallopian tubes that helps movement of the tube.

Cilia

______ help propel the ovum along the length of the tube

Zona pellucida and Corona Radiata

are the rings that surround the ovum, protects it against injury

Capacitation

the final process that the sperm undergoes to be ready for fertilization

Hyaluronidase

proteolytic enzyme released by the sperm to dissolve the layers or rings that surround the egg

zygote

ova + spermatozoa = ______

XX Female

If X carrying spermatozoan enters the ovum =

XY Male

If Y carrying spermatozoan enters the ovum =

Equal maturation of both sperm and ovum

Ability of the sperm to reach the ovum

Ability of the sperm to penetrate the rings

Fertilization is never certain: 3 factors for it to be possible

22 hours

The first cleavage occurs about 24 hours; cleavage divisions continue to occur at a rate of about one every __ hours

16-50 cells

By the time the zygote reaches the body of the uterus, it consists of __-__ cells

morula - mulberry

At this stage, because of its bumpy outward appearance, it is termed _____

Embryo

Once implanted, the zygote is called an ____

blastocyst

Large cells tend to collect at the periphery of the ball, leaving a fluid space surrounding an inner mass called _________ which will form into an embryo. Structure that is attached to the endometrium

placenta and membranes

the outer layer of the ring, trophoblast cells form into ______ and _______

8-10 days

contact between the growing structure and the uterine endometrium occurs approximately ___ days after fertilization

true

After the 3rd to 4th month of free floating, the blastocyst shed the last residues of the corona radiata and zona pellucida

trophoblast cells

The blastocyst is able to invade the endometrium because as the _______ _____ on the outside of the structure touch the endometrium, they produce enzymes that dissolves any tissue they touch

Implantation

_______ is an important step in pregnancy many as 50 percent of zygote never achieve it.

progesterone

Under the influence of ______, the endometrium increases thickness and vascularity in preparation for implantation and nutrition of the ovum

Decidua

After implantation, the endometrium is called _____ meaning “falling off” lochial discharges

Decidua basalis

Decidua capsularis

Decidua vera

Three layers of decidua

Decidua basalis

part that lies directly under the embryo or the portion where the trophoblast cells establish communication with maternal blood vessels

Decidua capsularis

covers the blastocyst

Decidua vera

remaining portion of the uterine lining and lines the rest of the uterine cavity

Chorionic Villi

Once implantation is completed, the trophoblast layer of cells of the blastocyst begins to mature rapidly. As early as 11th or 12th day, miniature villi that resemble probing finger called _____

Syncytiotrophoblast or Syncytial layer

Cytotrophoblast or Langhan’s layer

Covering layers:

Syncytiotrophoblast or Syncytial layer

produces placental hormones such as HCG, estrogen, and progesterone

Cytotrophoblast or Langhan’s layer

present during 12 days gestation. To protect the growing embryo and fetus from certain infectious organisms such as: Spirochete of syphilis. On the 20th to 24th month disappears.

Amnion

originates from the ectoderm. A protective membrane that contains amniotic fluid

Yolk Sac

small and functions early in embryonic life. Develops in the blastocyst about 8-9 days after conception

Amniotic Fluid

• _______ ______ is absorbed by the amniotic membrane ranges from 800 to 1200 mL.

• Most important purpose is to shield the fetus against pressure or a blow to the mother’s abdomen

• Helps to control the embryo’s temperature

Hydramnios

more than 2000 ml of amniotic fluid

oligohydramnios

less than 300 ml of amniotic fluid

Amniotic membranes

• the smooth chorion eventually becomes the chorionic membranes. The outermost fetal membranes. The purpose of membrane lining the chorionic membrane, the amniotic membrane or amnion forms beneath the chorion

• Seen covering the fetal surface of the placenta

Umbilical cord

• formed from the fetal membranes (amnion and chorion)

• provides a circulatory pathway that connects the embryo to the chorionic villi of the placenta

• Transport oxygen and nutrients to the fetus from the placenta and to return waste products from the fetus to the placenta

Wharton’s Jelly

gives the cord body and prevents pressure on the vein and arteries that passes through it

One large vein

carrying oxygenated blood from the placenta to the fetus

Two small arteries

carrying unoxygenated blood from the fetus

Placenta

• shaped like a pancake, grows from the trophoblast. Grows parallel to the growing fetus

• Developed by the first month of pregnancy

• serves as nourishment, oxygen transport and elimination

• 30 separate segments or cotyledons

Human Chorionic Gonadotropin

Human Placental Lactogen

Estrogen and Progesterone

The Placenta produces hormones vital to the survival of the uterus

Human Chorionic Gonadotropin

The first placental hormone produced, can be found in maternal blood and urine as early as the first missed menstrual period. The announcer of pregnancy can be obtained through blood serum and urine test

Estrogen

hormone for women. Primary estriol second of the product of the syncytial cells of the placenta. Contributes to the development of mammary gland for lactation and stimulate uterine growth to accommodate the growing fetus

Progesterone

hormone for mothers which maintains the endometrial lining of the uterine during pregnancy

Human Placental Lactogen

hormone with both growth promoting and lactogenic milk producing properties. Promotes mammary glands in preparation for lactation

10

Pregnancy is calculated to last an average of __ lunar months 40 weeks or 280 days

280 days

___ days is calculated from the onset of the last normal menstrual period to the time of birth

The stage of an embryo starts on the day — beginning of the third week after conception and continues until approximately the 8th week or until the embryo reaches a crown to rump (to the bottom of the buttocks)

cephalocaudal direction

From the beginning of fetal growth, development proceeds in a _______ direction

8 weeks gestation

All organ system are complete at least in a rudimentary form at __ weeks gestation (the end of the embryonic period). During this time of organogenesis (organ formation) the growing structure is most vulnerable to invasion by teratogens that could adversely affect the fertilized ovum

Ectoderm

Mesoderm

Entoderm

3 germ layers

Ectoderm

• CNS

• PNS

• Skin, Hair, Nails, Sebaceous glands

• Sense organs

• Mucous membranes of the anus, mouth, nose, tooth enamel

• Mammary glands

Mesoderm

• supporting structures of the body (connective tissue, bones, cartilages, muscle ligaments, tendons, dentin of teeth

• Upper portion of the urinary system (kidneys and ureters)

• Reproductive system

• Heart, circulatory system, lymph vessels

Entoderm

• lining of pericardial, pleura, and peritoneal cavities

• lining of the gastrointestinal tract, respiratory tract, tonsils, parathyroid, thyroid, and thymus glands

• Lower urinary system (bladder and urethra)

Cardiovascular System

• One of the first systems to become function intrauterine life

• Single heart tubes forms as early as the 16th day of life

• Beats as early as 24th day

• Heartbeat may be heard with Doppler at 10th to 12th week of pregnancy

• ECG may be recorded on a fetus at 11th week though accuracy is 20th week

• 28th week the sympathetic nervous system has matured

16th day

Single heart tubes forms as early as the __ day of life

24th day

Heart beats as early as __ day

10th to 12th

Heartbeat ay be heard with Doppler at __ to __ week of pregnancy

20th week

ECG may be recorded on a fetus at 11th week though accuracy is __ week

28th week

__ week, the sympathetic nervous system has matured

Fetal circulation

This intricate system allows the fetus to receive oxygenated blood and nutrients from the placenta. It is comprised of the blood vessels in the placenta and the umbilical cord, which contains two umbilical arteries and one umbilical vein

Fetal hemoglobin

more concentrated and has greater oxygen affinity

17.1 g/ml

Newborn (hemoglobin)

11 g/ml

Adult (hemoglobin)

fetal circulation

____ __________ is the way blood flows in a developing fetus before birth, when the lungs are not yet working

placenta

The _______, a temporary organ attached to the mother’s uterus, acts as the fetus lungs, delivering oxygen and nutrients through the umbilical cord

foramen ovale and ductus arteriosus

The fetal heart has two special openings, called ________ and ____________, that allow blood to bypass the lungs and go directly to the body

ductus venosus

The blood also bypasses the liver which is not fully functional, through another vessel called the ___ _____

fetal blood

_____ _____has a higher concentration of hemoglobin, a protein that carries oxygen, than adult blood, to cope with lower oxygen levels in the womb

Umbilical vein

• brings arterial blood in the heart (before birth)

• obliterated, becomes round ligament of liver (after birth)

Umbilical arteries

• brings arteriovenous blood to placenta (before birth)

• obliterated, become vesical ligaments on anterior abdominal wall (after birth)

Ductus venosus

• shunts arterial blood into inferior vena cava (before birth)

• obliterated, becomes ligamentum venosum (after birth)

Ductus arteriosus

• shunts arterial and some venous blood from pulmonary artery to aorta (before birth)

• Obliterated becomes ligamentum arteriosus (after birth)

head, neck, brain and heart

Fetal circulation delivers the highest available oxygen concentration to the ________________

3rd

At the _____ intrauterine life, the respiratory and digestive tracts exists as a single tube

24th and 28th week

Alveoli and capillaries form between ____ and ____ week

3 months

Spontaneous respiratory practice movements begins as early as ___ months

Surfactant

a phospholipid substance is formed and excreted by the alveoli. It allows the lungs to expand and prevents them from collapsing. It improves the infant’s ability to maintain respirations extrauterine life

Nervous system

develops at 3rd to 4th weeks intrauterine life

Islet of Langerhan in the pancreas

__________ produces insulin needed by the fetus.

Thyroid and Parathyroid glands

play vital roles in fetal metabolic function and calcium balance

Digestive system

separates from the respiratory tract about 4th week of intrauterine life and grows rapidly

first stool intrauterine life accumulates at the 16th week

• appears to be black or dark green (obtaining its color from bile pigment)

• sterile before birth