Fertilization and fetal development.docx

Fertilization

The process by which a sperm fuses with an ovum to form a new diploid cell called zygote.

Zygote

The initial cell formed after fertilization, containing 46 chromosomes (23 from the ovum and 23 from the sperm).

Capacitation

An enzymatic reaction that removes the glycoprotein coating from the spermatozoa, necessary for fertilization.

Acrosomal reaction

The release of enzymes by the sperm to penetrate the ovum's corona radiata during fertilization.

Block of polyspermy

Reaction preventing additional sperm from entering an ovum after fertilization.

Embryonic stage

The first 8 weeks of development post-fertilization, focusing on organ formation and vulnerability to teratogens.

Cleavage

Mitotic cell division of the zygote leading to the formation of a morula with inner cell mass and outer cell layer.

Blastocyst

The stage of development after the morula, characterized by a fluid-filled cavity and differentiation into embryonic disk.

Fetal stage

The period from the end of the 8th week until birth, marked by growth and development of organs formed during the embryonic stage.

Germ layers

Ectoderm, mesoderm, and endoderm, which differentiate from the blastocyst and give rise to all tissues, organs, and systems.

Quickening

The moment when the mother starts feeling fetal movements.

Vernix caseosa

A protective substance covering the fetus's skin, secreted by the sebaceous glands.

Grasp reflex

A reflex where the fetus grips onto objects placed in its hand.

Lanugo

Fine, downy hair covering the fetus's body, which starts disappearing as the fetus matures.

Crown-to-heel (C-H) length

Measurement from the top of the head to the heel of the fetus, indicating its size.

Pupillary light reflex

The response of the pupil to light stimuli, showing the development of the nervous system.

Rhythmic breathing movements

Controlled breathing movements initiated by the central nervous system, a sign of lung development.

Term pregnancy

Pregnancy lasting from 37 to 40 weeks after conception, considered full-term.

Testes descent

The process where the testes move from the abdomen into the scrotum in male fetuses.

Position of comfort

The fetal position where the head is downward, and the body is flexed, preparing for birth.

Corona radiata

Ring of elongated cells surrounding the zonal pellucida

Zona pellucida

Closest to the cell membrane of the ovum , a clear non cellular layer whose thickness influences fertilisation rate.

Spermatozoa

Derives energy for movement from the fructose in seven secreted by seminal vesicles.

Flagella movement of the tail

The spermatozoa propels themselves up the female tract by the flagella movement of their tails.

Physiology process of the sperm

Capacitation and Acrosomal reaction

Capacitation

An enzymatic reaction that removed the glycoprotein coating from the spermatozoa and plasma protein from the seminal fluid and occurs in the uterine tube or uterus. If not removed, the sperm will not be able to fertilize the ovum.Takes about 7hours

Characteristics of the sperm after capacitation

Ability to under acrosomal reaction

Ability to bind to the zona pellucida

Acquisition of hypermotility