embryology

EmbryologyBy: Bryan Mae Degorio

04/18/2023 Apollo Brawmell Nursing School

Objectives….. Contents…..

Discuss the process involve in ovulation, fertilization and implantation

Identify the different germ layers and how it affects the development of fetal membranes

Discuss fetal development and the corresponding developmental milestone

A. Ovulation, fertilization and implantation

B. Placenta and fetal membranes

C. Fetal growth and development

- Germ layers- Physical and physiologic

changes- Factors influencing

growth- Fetal circulation

D. Effects of Teratogens


Review on Menstruation?Menstruation- Refers to the cyclic

changes in a sexually mature, non-pregnant female that culminate in menses.

- Facts:a. Typically 28 daysb. Average blood loose

of 50-150 ml (1/4-1/2 cup)


Conception, Cell Division and Gametogenesis…Cell Division - The process by the which

the cell divides.

a. Mitosis- the body cells replicates to yield two cells of same genetic make-up

b. Meiosis- the germs cells divide and decrease in chromosomal number by half

Germatogenesis- The process by which

our body produces sex cells

a. Oogenesis- the process of egg formation

b. Spermatogenesis- the process of sperm production


Cont. Germatogenesis…


Conception- Refers to the union of single sperm and egg- It marks the beginning of pregnancy

a. Ovum/Egg is a mature oocyte Surrounding structure:

- zona pellicuda- corona radiata

b. Sperm/Spermatozoa 200-500 million

sperm per ejaculation Contains Flagella-

responsible in propelling toward the fallopian tube


Fertilization…..Is the union of the sperm and the egg.Zygote- fertilized ovumStages of fetal Development:

a. Pre-embryonic- 1st 14 daysb. Embryonic stage- 15-60 daysc. Fetal stage- 61 days until birth


The Blastocyst…- Forms when uterine

fluid starts to sip inside the morula and in between the blastomeres.

- Parts:a. Thropoblast- outer

layerb. Embryoblast- inner

laterc. Blastocyst cavity


Implantation…- It happens when the

thropoblast displaces endometrial tissue that it to burrow beneath the endometrial lining.

- Decidua- is the term used to describe the endometrium after implantation

a. Decidua basaleb. Decidua capsularisc. Decidua vera


Pre-embryonic Stage…1st 14 days starting from fertilizationFrom zygote, morula, blastocyst, initial development of

fetal membranes and the development of 3 germ layers.


Embryonic Stage…Starts from 15 days

unit 8 weeks or 60 days after fertilization.

The period of organogenesis.a. Development of fetal

membranes and the placenta

b. Development of the fetal embryo

The Fetal membranes and the Placentaa. Chorionic villib. Placentac. Umbilical cordd. Fetal membranes-

amniotic sac and amniotic fluid


Chorionic Villi- These are finger-like

projections that reach out to the uterine endometrium.

- It differentiates in to two layers:

a. Cytotrophoblastb. Syncytiotrophobl

ast


Placenta- This is the mature and

well developed villi.- It serves as the fetal

lungs, kidney, GIT and a separate endocrine system.

- Facts:a. It only allows diffusion of

selective substancesb. It is divided into segments

known as cotyledonsc. It weighs around 400-600

grams at term

- Functions:

a. Circulatory functions

b. Endocrine functions Human Chorionic

Gonadotropin Estrogen Progesterone Human Placental

Lactogen


Umbilical Cord- Forms from the

chorion and amnion and provided circulatory pathways for the fetus

- Facts:a. 2 veins and 1 arteryb. Blood flow of 350 ml/min

at termc. It surround by gelatinous

substance called Whartons jelly

d. Length 53 cm (21 inch) at term

e. Can be used for diagnostic sampling


Fetal Membranes- These are double layer

of membranes the form the amniotic sac.

a. Chorion- the outermost layer

b. Amnion- the inner layer


Amniotic Fluids- A clear to slight tinted fluids

the constantly formed and absorbed by amnion.

- Characteristics: it contains albumin, urea,

uric acid, creatinine, lecithin and sphingomyelin, bilirubin, fructose and leukocytes including lanugo.

800-1200 ml at term- Abnormalities:

Change in color: green, yellow, red

Oligohydramnios and polyhydramnios


The Fetal Circulation…Cardiovascular system is the first organ system.Facts:a. Fetal hemoglobin is carries 20-30% more O2 than maternal

hemoglobinb. The hemoglobin concentration is about 50% greater that that of

the motherc. The FHT is around 110-160 bpm making the CO higher than per

unit body weight.


Teratogens….These are agents that can disturb the

embryonic of fetal development.Classes:

a. Maternal infection (TORCH)b. Radiationc. Chemicald. Drugs


Alcohol- Is associated with the

development of fetal alcohol syndrome

- It characterized by abnormalities of craniofacial features.

Cigarette- This is associated IUGR,

LBW and SGA- It is a risk factor for

abruptio placenta- It also associated with

SIDS

Chemical…


Radiation… Rapidly growing cells are extremely vulnerable to radiation.

CDC believes that the most vulnerable period is between 0-18 weeks of pregnancy

Is associated with:a. Death of zygoteb. Mental retardationc. Cancer development in later life.


Drugs…This includes drugs

that are prescribed, OTC, herbal supplements and even recreation drugs

General rules:a. No medications should be

taken during pregnancy unless prescribed or approved by a physician

b. Childbearing age should take no drugs other than prescribed to avoid exposure should she become pregnant


Maternal infections…

TORCH infections

T- toxoplasmosis

O- others ( syphilis, varicella zoster, parpovirus)

R- Rubella

C- Cytomegalovirus

H- Herpes infection

embryology

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