Ch 3 Prenatal Development Flashcards
Embryology
Study of prenatal development
Gametes
Sex cells
New organism is produced when they unite and fuse together
Male gamete
Sperm
Produced in testes
Survive for several days
Female gamete
Secondary oocytes (potentially mature ova)
Produced from ovaries
Survive several hours
Zygote
Cell resulting from union and fusion of gametes
Fertilized egg
Contains chromosomes (dna) from both parents
From repeated mitotic cell division it develops into new organism (cleavage);
Gamete differ from other Somites body cells, they contain
Haploid chromosome number
“N”
In humans n=23
A single set of chromosomes
Diploid chromosome number
2n
In nucleus of somatic cells
In humans this number is 46 (2 sets of 23)
Meiosis
Process of cell division in which diploid cells in testes and ovaries are converted into haploid gametes
End result is 4 cells
Meiosis I
Meiosis II
Gamete splits and goes to separate cells
Splits into 4
-not identical
-each separate
-law of probability of combo of genes
Down syndrome
Meiosis malfunction
Trisomy 21
Congenital defects that could affect mouth and teeth
Prenatal development consists of ___ lunar months and is divided into 3 successive periods. Which are?
10
1)Preimplantation
2)Embryonic
3)Fetal Period
Preimplantation period
Wk 1
Fertilized egg (zygote) niche into wall of endometrium
Zygote develops into morula after mitosis
Morula into blastocyst
7-10 days blastocyst implants and consists of
-trophoblast
-embryoblast
Morula
Solid ball of cells
Mitosis ongoing and fluid secretions
Blastocyst
Vesicle developed from morula
Undergoes implantation after 7-10 days and turns into trophoblast and embryoblast
Trophoblast
Layer of peripheral cells
Develops into placenta
Embryoblast
Small inner mass of embryonic cells
Develops to embryo
Embryonic period
Wk 2-8
First 3 weeks=proliferation, migration and some differentiation
Following 4 weeks=differentiation of all major external and internal structures
Vulnerable period for the embryo
Physiological processes occurring during Embryonic period (5)
- Induction
- Proliferation
- Differentiation
- Morphogenesis
- Maturation
Induction
Embryonic period
Group of cells induce other groups of cells to take different path
Proliferation
Controlled cellular growth, by genes
Differentiation
Taking on different structure to take on diff function
Morphogenesis
Development of specific tissue structure and shape
Maturation
Attaining adult size and function
Most predominant
2nd week of development
Creation of bilaminar embryonic disc
-flattened circular plate of bilateral cells
Consists of epiblast layer and hypoblast layer
Epiblast layer
Composed of high columnar cells and faces amniotic cavity
Hypoblast layer
Small cuboidal cells and faces yolk sac
Major events of wk 3
Forming of primitive streak
Migration of some cells of epiblast to locate in between epi and hypo to form mesenchyme
Bi to tri disc (Ectoderm, Mesoderm, endoderm)
Oropharyngeal membrane
Or
Buccalpharyngeal membrane
Cloacal membrane
Development of nervous system
Diff. Neuroectoderm cells of neural plate
Forming of neural groove, groove to folds, folds fuse to tube
Neural crest cells
Major events wk 4
Embryonic folding of disc into embryo and tissue in proper positions for further development
Ectoderm outside
Middle mesoderm
Inside endoderm
All organs present, membranes developed
Placenta developed 3rd month
Fetal period
9 wks to birth
Maturation of existing structures as embryo enlarges to fetus
(Last 2 trimesters)
Spindobifida
At wk 3 neural folds do not fuse properly to form neural tube
Primitive streak
Furrowed, rod shaped thickening that causes disc to have symmetry
Right and left half
Mesenchyme
Embryonic connective tissue
Ectoderm
Wk 3
Forms from epiblast
All epithelium and nervous system comes from
Mesoderm
Wk 3 embryonic
Somites
Everything in between Epithelium of skin and digestive tract
Endoderm
Digestive tract develops from this
Formed from hypoblast
Buccopharyngeal membrane
or
Oropharyngeal “ “
Cloacal membrane
@ cephalic end of disc, beginning of digestive tract
@ caudal end , end of dig. Tract
Both consist only of ectoderm and endoderm (fused)
Neural crest cells
Differentiate from neuroectoderm (taking on different structure to take on different function)
Will develop head and neck
Somites
Form end of wk 3
Mesoderm divides on each side of tube into 38 paired cuboidal segments
Implantation
Blastocyst embedded in endometrium, the innermost lining of the uterus on its back wall
