Principles Of Embryology Flashcards
How many weeks are in the conceptus/embryo period of development
0-3
How many weeks are in the embryonic period of development
3-8
How many weeks are in the foetal period of development
9-40
At how many weeks if the highest risk of birth defects
5
When does the most GROWTH take place
During the foetal period
Phases of embryogenesis
Gametogenesis
Fertilisation
Cleavage
Gastrulation
Formation of a body plan
Organogenesis
What happens during gametogenesis
Formation of gametes
Mitosis and meiosis
When do primary oocytes begin meiosis
Week 28-30
What stage during the cell cycle do primary oocytes stop until puberty
Prophase
How long is each cycle of spermatogenesis
64-74 days
How does nondisjunction occur
Separation of chromosomes in 1 gamete does not occur (leading to 3 copies of 1 chromosome)
How does the ovum prevent polyspermate
Membrane of ovum depolarises to lose sperm receptors
What happens during the stage of cleavage
Rapid mitotic cell division
No increase in size
Morula then blastocyst
What happens during the stage of gastrulation
Formation of germ layers
Body axis established
What are the 3 germ layers of an embryo
Ectoderm
Mesoderm
Endoderm (inner)
How does the formation of the body plan occur
Folding of the embryo to form tubes
Direction of folding dependant on body axis
What structures are formed by embryonic folding during the formation of the body plan
Gut tube
Skin/body wall
What happens during organogenesis
Formation of organs and organ systems all in place by end of embryonic period
Continue to develop throughout fetal period
What happens during the foetal period
Growth and weight gain
Tissues become functional
Overt sexual differention
Bone laid
Connections made in CNS
What are the changes in anatomy labels for a foetus
Cranial
Ventral (anterior)
Dorsal (posterior)
Caudal (tail)
What are the cellular processes involved in forming a human body
Cell division
Differentiation
Cell attachment (tissues form)
Apoptosis
What is induction
Primary process
Ability of one cell type to cause another to differentiate
Directly or over distance
What is cell migration
Primary process
Movement from one location to another
What secondary processes take place in the process of turning a zygote to a human body
Axis formation
Control of development
What are the types of control of development
Genetic - gene expression
Epigenetic - expression of maternal or paternal
Environmental - diet, climate, stress
