Chapter 3: Embryology Flashcards
Embryology
Pre-embryonic period
Embryonic period
Fetal period
Prenatal period, first 38 weeks of human development
First 2 weeks after fertilization of egg/ formation of zygote
3-8th week of development when all major organs are developed-embryo
9-28th week growth dominates-fetus, fetal period ends at birth
Mitosis
diploid cell produces two genetically identical diploid daughter cells
Gametogenesis
Autosomes
Gametes
sex organs begin to produce sex cells- gametes
contain genetic information for human characteristics (eye color, height)
Haploid (23 chromosomes) Diploid (23 pairs)
Meiosis (I and II)
Male Viable sperm
Female oocyte
1 diploid parent cell produces two daughter cells each containing 23 double stranded chromosomes (Meiosis I)
Meiosis II) produces 4 haploid daughter cells each containing 23 single-stranded chromosomes
4
1 oocyte, other 3 form polar bodies and die, don’t participate in formation of fetus
Corona radiate
Zona Pellucia
Sperm-fertilized-zygot
Ovum
ovum expelled from ovary surrounded by both structures
C.R- several layers of cuboidal cells
Z.P- clear layer of proteins under C.R
Sperm must penetrate both structure to fertilize, if fertilized secondary oocyte complete Meiosis II-forms zygote, which will produce 2 daughter cells unequal division of cytoplasm
ovum- larger cell, 23 chromosomes that will combine with 23 provided by sperm, smaller polar body will degenerate in 24 hours
Oocyte development (Oogenesis)
Oogonia- location, enter phase, start and end, primary oocyte
Meiosis I- polar body, secondary oocyte
Ovulate
oogonia- parent cell that produce haploid oocytes (eggs) through meiosis, located in ovaries, enter prophase I during fetal development- primary oocyte, oogenesis starts in fetal life and ends until puberty, number of primary oocyte begin to mature by resuming meiosis I
Meiosis I produced two daughter cells but cytokinesis divides the cellos unequally
polar body- smaller cell and will die
secondary oocyte- larger cell, stops at Metaphase II and is ovulated- ovary into uterine tube, only complete meiosis II if fertilized or else dies
Sperm development (spermatogenesis)
Spermatogonia-live-mitosis
Primary spermatocytes-meiosis-spermatids
spermiogenesis- flagellum
Spermatogonia- parent cells that produce haploid sperm through meiosis, in male testes, divides by mitosis produce two genetically identical cells-Primary spermatocytes, undergoes meiosis -> four haploid spermatids 23 chromosomes-spermatids
spermiogenesis-spermatids become mature sperm, grow a long tail- flagellum
Fertilization Capacitation Acrosome Corona radiate penetration Zona pellucida penetration Fusion of sperm and oocyte
two sex cells fuse to form new cell with genetic material from parents, sperm deposited in female reproductive tract & initially unable to fertilize with secondary oocyte, capacitation- period of condition for sperm in the vagina
acrosome- on the sperm head, digestive enzymes that eat through zone pellucida and facilitate sperm penetration into cytoplasm of the egg
CRP- sperm motility allows to push through cell layer, changes to prevent another sperm after fusing
ZPP- sperm releases acrosome
nucleus of the sperm enter the cytoplasm of the oocyte
Cleavage Compaction Morula Blastocyst cavity - Blastocyst Trophoblast Embryoblast (inner cell mass) Pluripotent
- series of mitotic division after zygote is formed
- number of cells increase total size remains same increased contact between cells
- close to when it enter uterus, 16th stage, and continues to divide
- after morula enters uterine cavity develops fluid-filled cavity and organism is now blastocyst
- outer ring of cells that will develop into chorion
- cluster of tightly packed cells inside trophoblast
- inner cells able to differentiate into any cell type
Implantation Endometrium- 2 layers Day 7: Cytotrophoblast and Synctiotrophoblast Day 9 (Fig 3.6)
end of 1st week after fertilization, zone pellucida has degraded, trophoblast makes direct contact with cells that line the inside of the uterus- endometrium, deep basal layer (stays) and superficial functional layer (gets removed every month during menstruation, Day 7: blastocyst invades functional layer and trophoblast turns into two layers: inner cell layer and outer thick layer, forms placenta, continues to invade endometrium, Day 9: blastocyst completely burrowed into uterine wall
Formation of the Bilaminar Germinal Disk (Day 8) Hypoblast Epiblast Bilaminar germinal disk (Fig 3.6)
embryoblast differentiate into 2 types
layer of small cuboidal cells facing blastocyst cavity
layer of columnar cells deep to the hypoblast
together they form a flat disk
Formation of the Extraembryonic Membranes Yolk Sac Amnion Chorion (Fig 3.7)
- formed and continuous with hypoblast, serves as a site for early blood cell and vessel formation
- thin layer of cells forms above and derived from epiblast, fluid filled amniotic cavity appears between amnion and epiblast layer
- outermost membrane responsible for formation of placenta, derived from cytotrophoblast and synctiotrophoblast
Development of the Placenta
Functions
Formation
- important for attaining nutrition, gets rid of waste, highly vascularized organ serves as physical and biochemical interface btwn embryo and mother
- exchange of nutrients, waste products, & blood gases exchange, transmission of maternal antibodies, and production of antibodies- estrogen and progesterone
- forms during 2nd week of development, embryonic portion is chorion and maternal portion is endometrium
Gastrulation Primary Germ layers Embryo Primitive Streak Primitive Node Primitive Pit Invagination Mesoderm Endoderm Ectoderm
- 3rd week of development after implantation, process by which cells from epiblast migrate to form 3 primary germ layers
- which are the cells which all body tissue develop
- once all three germ layers are present called embryo
- gastrulation begins with P.S, thin depression on surface of epiblast
- cephalic (head) end of the streak
- depression in the node
- cells from epiblast move through primitive steak and locate themselves between epiblast and hypoblast layer
- cells btwn epiblast and hypoblast
- migrating cells displace hypoblast (bottom)
- remaining in the epiblast (top)
Differentiation of Ectoderm Structures Neurulation Neural tube Notochord
- located on external surface of the embyo
- epidermis of the skin, derivatives of epidermis: hair nail, and nervous system
- formation of neural tube from overlying ectoderm cells
- develop into the central nervous system and begins with appearance of notochord
- derived from mesoderm, cylindrical structure, forms internal and parallel to primitive streak
