LU 2 Fertilization and Conception

What is conception ?

• complete process that leads to pregnancy

• consists of ovulation, fertilization and implantation

What is fertilization ?

• begins when a sperm fuses with an ovum

• after ovulation, ovum transported to the fallopian tube

• fertilization occurs in the ampula of the fallopian tube

What are the 2 processes of change that sperm undergoes before penetrating ovum ?

• Capacitation (removal of glycoprotein coat and seminal proteins)

• Acrosomal reaction (releases 2 enzymes)

What is Zona reaction ?

• sperm successfully penetrates the membrane surrounding the ovum which make it impenetrable for other sperm

Briefly explain the cell division of zygote ?

• mitotic cellular replication (cleavage) begins as the zygote travels the length of fallopian tube into uterus

• within 24 hours being fertilized, it starts dividing very fast to form a cluster of cells known as morula

What are the structure of blastocyst ?

• consists of ‘

• trophoblast : placenta and chorion

• inner cell mass : fetus, amnion, umbilical cord

Briefly explain the implantation of blastocyst ?

• occurs in the endometrium of the anterior/ posterior wall of uterus near fundus between day 6-10 after fertilization

• after implantation, endometrium is called decidua

What hormone does cytotrophoblast produce ?

• human chorionic gonadotrophin (hCG) which prevents generation of corpus luteum

• corpus luteum produces estrogen and progesterone

• progesterone maintains the integrity of decidua

What is inner cell mass and its layer ?

• it will forms the fetus

• 3 layers known as embryonic plate :

• ectoderm : forms the skin and nervous system

• mesoderm : forms bones, muscles, heart and blood vessels

• endoderm : forms mucous membrane and glands

What are the stages of fetal development ?

• Preembryonic stage : Fertilization to 2-3 weks

• Embryonic stage : 4-8 weeks of gestation

• Fetal stage : 9 weeks after conception until birth

Briefly explain the fetal circulation

• oxygenated blood from placenta enter fetus via umbilical vein

• deoxygenated blood return to placenta via umbilical arteries originating from the internal iliac near the bladder

When will the placenta develop ?

• after third week of gestation

How to achieve optimal circulation of placenta ?

• when the mother is lying on her left side

What are the surfaces of placenta ?

• fetal surface : a smooth appearance with umbilical cord attached at centre

• maternal part : a rough appearance and divided into several cotyledons

What are the placenta functions ?

• as endocrine gland

• metabolic, respiratory, renal and nutrient function

• immunologic functions as it transfer immunoglobin and antibodies from mother to fetus

• protective barrier against harmful effect of certain drugs and microorganism

What are the membrane layer of the fetus ?

• inner layer (amnion)

• outer layer (chorion)

• yolk sac

• allantois

How many vein and arteries does umbilical cord have and what are its function ?

• one vein and two arteries

• vein : to carry nutrient and oxygen rich blood to the fetus

• two arteries return blood containing waste from fetal circulation back to the placenta

What is the normal length of umbilical cord ?

• 50-60 cm

• if less than 40 cm : it is short

What is true knot ?

• true knot in the umbilical cord lead to fetal death in utero at 39 weeks

Briefly explain the hormonal changes in fertilizations ?

• once fertilized eggs implants, it secretes hCG which trigger the production of progesterone and estrogen

• these hormone maintain the pregnancy and support the growth and development of the embryo

• placenta releases pregnancy supporting hormones to provide nutrients and oxygen to the developing fetus and removing waste products

What are the key hormones in pregnancy ?

• Human Chorionic Gonadotropin (hCG) : sustain the corpus luteum to produce estrogen and progesterone

• Estrogen : increasing blood flow to the uterus

• Progesterone : to maintain uterine lining and prevent miscarriage

• Human Placental Lactogen (hPL) : regulate maternal glucose and fat levels

• Prolactin : to prepare the breast in milk production

• Relaxin : relaxes ligaments and connective tissues to make space for growing fetus