Human Embryology 1 Flashcards
Process of an individual organism growing organically
Ontogenesis
Gestational Period from fertilization to parturition of mature fetus
38 week (266 days)
Three periods of gestation
- Preembryonic period
- Embryonic period [Week 3-8] (sensitive to congenital malformations)
- Fetal period [Week 9 - birth]
Gametes are _______ cells
Haploid
Somatic cell are _______ cells
Diploid
Mitochondria-filled area of the tail of the mature spermatozoon
Middle piece
The removal of glycoprotein coat and seminal plasma proteins to allow sperm to fertilize an ovum
Capacitation of sperm
The process by which the male and female gametes (sperm and ovum) unite to give rise to a zygote
Fertilization
Ampullary region of the oviduct
Site of fertilization
Three phases of fertilization
- Penetration of corona radiata
- Recognition and penetration of zona pellucida
- Membrane fusion and entry
After sperm binds to zona pellucida, induced by calcium ion influx
Acrosome reaction
Ovum (22+X) + Sperm (22+X)
Female
Ovum (22+X) + Sperm (22+Y)
Male
24 hours after fertilization, the mammalian zygote (1 cell) begins cleavage - forming 2 blastomeres; then 4 blastomeres
Cleavage
After 72 hours, blastomeres multiply forming
Morula
Blastocyst formation occurs day
4-5
Blastocyst is also called
Blastula
Three parts of blastocyst
- Inner cell mass (embryoblast)
- Trophoblast (outer cell mass)
- Blastocyst cavity (blastocoele)
Develops into embryo proper
Inner cell mass
Forms at the time 4-5 days after fertilization
Blastocyst
The discovery of Human Embryonic Stem Cells accredited to
James Thomson
The process by which the blastocyst is embedded into the endometrium of the uterus
Implantation
Implantation occurs after fertilization on day
7-8
6th - 7th ~ 11th - 12th
The process of implantation
Zona pellucida disappear —> polar trophoblast touch the endometrium —> secrete proteolytic enzyme —> binds to endometrium wall —> the area is sealed
Implantation occurs in which phase of cyclic changes of the endometrium (menstrual cycle)
Secretory phase
Trophoblast proliferates into two layers
- Syncytiotrophoblast (has lacunae filled with maternal blood - filled with nutrition for fetus)
- Cytotrophoblast
Implantation occurs normally in
Posterior wall of fundus and body of uterus
Implantation occurs abnormally in
- Placenta praevia
- Ectopic pregnancy (most often in oviduct)
Cells of the endometrium become polyhedral and loaded with glycogen and lipid droplets
Decidua reaction
The functional zone (functionalis) of the endometrium that performs the decidua reaction
Decidua
Three layers of the Decidua
- Decidua Basalis
- Decidua Capsularis
- Decidua Parietalis
key figure for examination
At the beginning of the 2nd week, bilaminar germ disc is formed having
- Epiblast
- Hypoblast
Amnioblasts differentiate into
Amniotic epithelium to form the amnion
Occurs during the third week of gestation, changes from bilaminar germ disc to trilaminar germ disc
Gastrulation
The appearance of the primitive streak determines the
Cranial and caudal end of the germ disc
Primitive node is at the _______ of the germ disc
Cranial end
Cells of the primitive groove proliferate and migrate downwards to form two cell layers
- Mesoderm
- Endoderm
Epiblast changes its name to ______ by the end of the third week during the formation of the trilaminar germ disc
Ectoderm
At the cranial end of the primitive streak
Oropharyngeal membrane (having endoderm & ectoderm, but no mesoderm)
At the caudal end of the primitive streak is the
Cloacal membrane (having endoderm and ectoderm, but no mesoderm)
Cells of the primitive pit proliferate and grow in the cranial direction forming the:
important in the formation of the neural tube
Notochord
The embryonic period is also called the
Period of organogenesis
Differentiation of ectoderm occurs between days _______ and results in the formation of the neural plate
18~19
Anterior neuropore will be closed at the _____ day after fertilization
25th
Posterior neuropore will be closed at the _____ day after fertilization
27th
Premordium of the Central Nervous System (from the ectoderm)
Neural tube
Anterior neuropore not closed
No brain
Posterior neuropore is not closed
Spina bifida
The ectoderm becomes the Peripheral Nervous System from the
Neural crest
Differentiation of the mesoderm occurs on the
17th day
Intermediate mesoderm forms
Most of the organs in the urinary and reproductive (genital) system
Lateral mesoderm has
- Intraembryonic coelum
- Somatic (parietal) mesoderm
- Splanchnic (visceral) mesoderm
Lateral mesoderm also forms
Heart and blood vessels
The epithelium of the digestive and respiratory system are derived from the
Endoderm
At the caudal end, structure present called the
Allantois