Embryology Timeline

Embryology Timeline

Created by Arisel Aguilera-Flores

WEEK 6

The Brain

Embryology

WEEK 3 continued...

The Heart

• derives from ectoderm
• PROSENCEPHALON has folded to form
• MESENCEPHALON (middle brain --> thalamus and hypothalamus)
• TELENCEPHALON (end brain --> cerebral hemispheres, basal ganglia, lateral ventricles)

• the heart derives from the mesoderm
• develops alongside the aorta (AO begins to branch)
• begins to beat at about 21-23 days

The study of embryos and their development, starting from conception, all the way up to 8 weeks.

WEEK 1:

Menstruation

WEEK

Inferior Vena Cava

• derives from mesoderm
• develops in segments

* heaptic sections

* prerenal section

* renal section

* post renal section

Portal Vein

The first day of a woman's menstrual period which indicates the start of a new monthly cycle. The uterine lining sheds and causes a woman to bleed for an average of 5-7 days.

WEEK 4:

Missed period occurs here!

• derives from mesoderm
• primitives vascular network form together to give rise to the main portal vein

THYROID

• derives from endoderm
• begins circulating thyroid hormones
• regulates metabolism

WEEK 3 continued...

Neural Tube Development

WEEK 2:

Ovulation

Fertilization of Ovum resulting in Zygote

LIVER

• derives from endoderm
• hepatocites/immne system cells from hepatic parenchyma
• organized into lobules

*HEMATOPOIESIS BEGINS @ WEEK 6*

WEEK 2:

Fertilization/Zygote

WEEK 8

• derives from the ectoderm
• includes the central nervous system (brain and spinal cord)

The most fertile days in a woman's monthly cycle. A mature egg (ovum) releases from one of the ovaries. Usually occurs 2 weeks before next menstrual period.

BREAST DEVELOPMENT

- derives from ectoderm

- mammary ridges visible by 6 weeks

- by 8 weeks, breast bud has developed along ridges

If a male gamete/sperm unites with the egg/ovum and fertilizes it, the ovum is now considered a zygote. The woman is now pregnant, but does not know it yet. This week would mark the approximate week of conception.

XX

XY

WEEK 5:

SEX DETERMINATION

THANK YOU FOR READING!

• testes rise near the kidneys
• descend into scrotum around 7th month

• mullerian ducts form, fuse, resorb to create the uterus, vagina, and fallopian tubes

- presence of absence of Y chromosome

- prior to week 8, male/female embryos appear identical

WEEK 3:

Blastocyst/Implantation

PANCREAS

• derived from mesoderm
• develops alongside the liver and biliary tract

GI TRACT

• derives from endoderm
• FOREGUT --> mouth, stomach, esophagus, prox. duodenum, liver
• MIDGUT --> distal duodenum, proximal colon
• HINDGUT --> remainder of colon
• TAILGUT --> resorbed

KIDNEYS

• derives from mesoderm
• PRONEPHROS --> primitive buds
• MESONEPHROS --> excretory system
• METANEPHROS --> kidney forms (BUT DOESN'T FUNCTION UNTIL

WEEK 12)

SPLEEN

• derives from mesoderm
• produces red/white blood cells
• heart tube beats @ 110 BPM by end of week 5
• FHM (fetal heart motion) can be visualized by end of week 5 as well

The embryonic stage starts at about the third week of pregnancy. The blastocyst begins taking on human characteristics and is then called an embryo.

A blastocyst forms about 5-6 days after a sperm fertilization en egg.

A blastocyst is a cluster of dividing cells made by a fertilized egg (zygote.)