ANT334H5 Lecture Notes - Fall 2018 Lecture 3 - Neural plate, Endoderm, Periosteum
ANT334 LEC3 190918
Embryology & Bone Development
Why Study Embryology, Human Development & Growth in Osteology?
- If something goes wrong during this process, it will affect every step following
- Understanding the process allows you to make predictions about
o Sex differentiation
o Aging
o Adaptation
o Evolutionary change
- Help develop new techniques
- Better understand relationship between structure & function
- Foundation for understanding pathological conditions
3 Stages of Development
- Counting from day of ovulation
- Days 1-7
o Pre-implantation stage – involves cell division
- Weeks 2-8
o Embryonic stage – cell differentiation
- Week 9-birth
o Fetal stage – development and growth
- Counting weeks pregnant
o 1st day of last menstrual cycle (the one day that can be defined)
▪ 2 weeks pregnant at time of ovulation
- Embryologists use Carnegie stages
o Development not time
Preimplantation Stage: Fertilization to Blastocyst
- Release of ovum
a. sperm penetrates oocyte in fallopian tue = zygote
b-d. 2, 4, 8, cell stage – days 1, 2, 3
e. 16-32 cell morula (mass of cells) – day 4 uterine cavity fluid enters morula
o separates into 2 layer structure = blastocyst
o 1. Embryoblast
o 3. Trophoblast – placenta and membranes
o 4. Blastocyst cavity – space with fluid
f. morula entered uterus to become blastocyst – day 6
o Blastocyst attaches to uterine lining
Embryonic Period – weeks 2-8
- Sees differentiation
- 3 stages
o Presomite (days 8-21)
o Somite (days 22-31)
Document Summary
If something goes wrong during this process, it will affect every step following. Understanding the process allows you to make predictions about: sex differentiation, aging, adaptation, evolutionary change. Better understand relationship between structure & function. Days 1-7: pre-implantation stage involves cell division. Weeks 2-8: embryonic stage cell differentiation. Week 9-birth: fetal stage development and growth. Counting weeks pregnant: 1st day of last menstrual cycle (the one day that can be defined, 2 weeks pregnant at time of ovulation. Embryologists use carnegie stages: development not time. Blastocyst cavity space with fluid: morula entered uterus to become blastocyst day 6, blastocyst attaches to uterine lining. 3 stages: presomite (days 8-21, somite (days 22-31, postsomite (32-56) Somite is a block of tissue that is the same structure running the axial part of embryo. #6 & 4 on diagram = somites: segments of paraxial tissue. Days 8-13 formation of: 1 = yolk sac, 3 = amniotic cavity, 5 & 7 = embryonic disk.
