Fertilization Flashcards
Capacitation
glycoprotein coat and seminal plasma proteins are removed from the plasma membrane that overlies the acrosomal region of the spermatozoa.
Acrisomal reaction
Release of acrosin, esterase or neuroaminidase
Elicited by zona pellucida
Phases of fertilization
Penetration of corona radiata
Penetration of zona pellucida
Fusion of the sperm and oocyte plasma membrane
Completion of 2°meiotic division/ Formation of female pro nucleus
Formation of male pro nucleus
Fusion of pronucleuses
Phases of embryology
Zygote Morula Blastomere Gastrula Neurula
Results of fertilization
Restoration of the diploid number of chromosomes
Determination of chromosomal sex of the new individual
Initiation of cleavage
Zygote transported to uterus by
Peristalsis
Ciliary beats
First week of development
Cleavage
Blastocyst formation
Implantation begins
30 hrs after fertilization
2 cell stage
Blastomere
Day three
Morula
16 cells
Day 4
Uterine fluid gushes in
Trophoblast and embryoblast formed
Blastocele
Day 5
Blastocyst(100-150 cells)
Zona pellucida degraded
HCG released
Day 6
Implantation begins
After implantation functional endometrial layer converted to
decidua
Day 8
Syncithiotrophoblast and cytotrophoblast
Hypoblast and Epiblast
Amniotic cavity forms
Trophoblasts
Enzyme for zona pellucida degradation
Release Human chorion gonadotropin
endometrial stromal cell become swollen & filled with glycogen called
decidual reaction
mediate initial attachment of the blastocyst to the uterus
L selectin on trophoblast cells and its carbohydrate receptors on the uterine epithelium
Cytotrophoblast
Secrete enzymes for uterine breakdown
Products absorbed by Syncythiotrophoblast
Placenta previa
Near internal os
Day 9
Lacunae form
Exocoelomic membrane
Fibrin coagulum
Day 11-12
Blood flows into the lacunae forming uteroplacental circulation
Extraembryonic mesoderm forms and cavities begin to form between them
Decidua reaction
Extra embryonic cavity aka
Chorionic cavity
13 day
Masses pinch of the primary yolk sac and form the secondary yolk sac and the exocolemic cyst
3rd week
characterized by formation of primitive streak and 3 germ layers
By gastrulation stage we can identify
craniocaudal axis
cranial and caudal ends
dorsal and ventral surfaces
right and left sides
Remnants of primitive streak
Sacrococcygeal Teratomas
Functions of notochord
Defines primordial axis of the embryo
Provides rigidity to the embryo
Serves as a basis for the development of the axial skeleton
Indicates the future site of the vertebral bodies/column
Regulates differentiation of surrounding structures
Nucleus pulposus
Remnants of notochordal tissue give rise to
Chordomas
Inward movement of epiblast
Invagination
embryonic mesoderm separate ectoderm and endoderm completely except
Oropharyngeal membrane cranially
Cloacal membrane caudally
In the middle cranial to primitive node where notochordal process extends
Process of formation of neural plate, neural folds & their closure to form neural tube
Neurulation
Nerulation induced by
Notochord formation
Somites development
Intraembyonic mesoderm-> paraxial mesoderm->somites
Somites function
Axial skeleton
Musculature
Dermis
agents such as drugs and viruses that produce or increase the incidence of congenital anomalies
Teratogens
Teratogens
agents such as drugs and viruses that produce or increase the incidence of congenital anomalies.
Neural tube forms the
CNS
Neural crest forms the
PNS
The cranial pit becomes the& separated from gut tube by .
oral pit (stomodeum) , oropharyngeal membrane
The caudal pit becomes the separated from caudal end of primitive gut by .
anal pit (proctodeum), cloacal membrane
Dorsal end of yolk sac
Primitive gut
Primitive gut
Foregut
Midgut
Hindgut
The development of the cardiovascular system is essential because
diffusion of nutrients by the early uteroplacental circulation can no longer satisfy the nutritional needs of the rapidly developing embryo
Derivatives of Ectoderm
Attractoderm
Mouth, eyes, hair, skin, nervous system, adrenal medulla, pituitary gland, nail, anus, mammary gland
Mesoderm derivatives
Musculoderm or CT
Muscle, dermis, bone, cartilage, adrenal cortex, circulatory system, kidney, gonad, spleen
Endoderm derivatives
Tubingderm
Liver, pancreas, respiratory tract, GI tract, lower urinary tract, thyroid, thymus
9th-12th week
Primary ossification centers appear
Urine formation
Genitalia distinguished
13-16th week
Rapid growth
Ossification begins
Primordial follicles
17th-20th week
Growth slows down
Fetal movements are commonly felt by the mother
The skin is covered with vernix caseosa.
covered with fine hair called lanugo
Uterus formed
Testes begins descent
Brown fat forms
21st-25th week
Weight gain
Surfactant
Surfactant secreted by
types II pneumocytes
26th-29th
Safe for Pre mature birth
Eyes open
30th-34th week
Pupillary light reflex
Pink skin
Descent of testis continues till 32nd week or above
8% fat
35th-38th week
Firm grasp 16% fat Prominent chest White or bluish-pink skin Testes in scrotum
MULTIPLE PREGNANCIES cause
multiple ova & abundant spermatozoa = Dizygotic or Multizygotic
May develop by splitting of the zygote, morula, or blastocyst = Monozygotic
Dizygotic twins
Two ova and two sperm
Placenta may fuse
Separate amnion and chorion
When placenta fuse, the blood vessels may anastomose & blood mixes forming blood group
chimesas
Monozygotic twins
One ova and one sperm
Splitting
Early separation
30 hours after fertilization
2 chorion, placenta and amnion
Implanted close
Separated at 1 week
1 chorion and placenta
2 amnion
Late separation
2 weeks
1 amnion, chorion and placenta
Conjoined, parasitic, or separate twins
site of attachment of conjoined (Siamese) twins
Thoracopagus
Pygopagus
Craniopagus
Omphalopagus
Craniothoracopagus
Massive fusion
the fertilization of two or more oocytes at different times.
Superfecundation
