Module 2 | EMBRYOLOGY

What is EMBRYOLOGY?

study of developmental changes of the body before birth

When is the EMBRYONIC period?

first 8 weeks

What major events occur during embryonic period?

Organs form from the 3 primary germ layers.
The basic body plan emerges.

When is the FETAL period?

Weeks 9 to 38 or birth

What major events occur during the fetal period?

organs grow in size and complexity

What are the stages that an embryo goes through during the first week?

Zygote
4 cell
Morula (Solid Cluster 12-16 cells)
Blastocyst-fluid filled structure 60 cells (embryo implants at this stage)

What is the embryo called during the when implantation occurs?

blastocyst

What is GASTRULATION?

- a process of invagination of epiblast cells
- begins at primitive streak
- forms the 3 primary germ layers

What are the 3 layers called that form?

primary germ layers
(develop for epiblast cells)

What happens during NEURULATION?

-neurulation (ectoderm)

starts forming brain & spinal cord

What forms from ECTODERM?

forms exoskeleton

brain, spinal cord, epidermis, hair, nails & skin

What forms from the MESODERM?

-nucleus pulposus of intervertebral discs
-heart, blood vessels, serosa, vertebrae, ribs, kidneys & gonads

What forms in the ENDODERM?

-inner epithelial lining of the gut tube
-respiratory tubes, digestive organs & urinary bladder

What happens from Weeks 5-8?

-limb buds form
-embryo first looks recognizably human (wk8)
-head is disproportionately large
-all major organs in place

What happens during FETAL PERIOD (wk 9-38)?

-maturation rapid growth
-cell differentiating during first half of fetal period
-normal birth occurs at 38 wks
-premature birth anything before 38wks.

What is the BASIC BODY PLAN?

-Skin
-Outer Body Wall
-Body Cavity & Digestive Tube
-Kidneys & Gonads
-Limbs