Exam 1: Embryology Flashcards
What is embryology
Biological science branch that focusses on study of the individual in the prenatal stage
Gametogenesis to birth
Gametogenesis
Male:
Spermatogonia –> spermatozoa
Female:
Oogonia –> Oocytes
Both haploid cells
Fertalization
Oocyte + Spermatozoon = Zygote
Zygote
Primary cell embryo comes from
Fertilization Steps (8)
- Spermatozoids deposited in vagina/uterus
•seminal secretions protect from pH (acid to alkaline)
•stop acrosome activity until right location - uterine tube - Spermatozoa capacitation
•loss of surface cholesterol and glycoproteins
•spermatozoon and acrosome membrane fuse - acrosome reaction - Enzymes from acrosome released
•hyaluronidase, cathepsins - Spermatozoon breaks through oocyte’s corona radiate
•follicular cells surrounding oocyte
5.Spermatozoon penetrates zona pellucida (glycocalyx) of oocyte *still in metaphase II)
•zona pellucida alters to repel other spermatozoa
- Spermatozoon’s membrane fuses with oocyte’s membrane
•once membranes fuse - zona pellucida changes conformation to prevent other sperm from entering - Genomic material from spermatozoon is released into cytosol of oocyte
•oocyte completes meiosis II - formation of female pronucleus
•Spermatozoon’s nucleus rehydrates - male pronucleus - Fusion of pronuclei = zygote
Outcomes of fertilization
Oocyte finishes meiosis - which was halted at metaphase II
Chromosome numbers re-established - pronuclei fusion
Sex is set
Growth begins via mitosis
Sex determiation
Mammals:
XX - female
XY - male
Birds:
ZW - female
ZZ - male
Growth phases
Growth begins with mitosis
Segmentation/cleavage
Gastrulation
Body shape acquisition:
Growth phases - segmentation/cleavage
Zygote divides into blastomeres (mitosis)
Blastomeres form a sphere (n>16) = morula
Morula (16+ blastomeres) differentiates
Morula migrates to uterine body from uterine tube, keeping zona pellucida
•fluid fills cavity - blastocoel
•Once blastocoel formed - now a blastocyst
What does morula differentiate into
Trophoblast - becomes the placenta
Embryoblast - becomes the embryo
What signals the end of segmentation/cleavage
Blastocyst formation
Growth phases - gastrulation
Embryoblasts goes from a collection of cells to 3 tissue types
Ectoderm - on outside of blastocyst
Endoderm - on inside of blastocyst
Mesoderm - in middle of blastocyst
Gastrulation - ectoderm
Starts elongating
Primitive node
Primitive groove
Notochord
Notochord
Forms intervertebral discs
Kinda like a rope that goes along the axis, in the middle
Kinda like an embryonic spinal cord
What signals the end of gastrulation
Notochord formation
Growth phases - body shape acquisition
Sketches of organs
Gene regulatory networks
Includes:
Neurulation
Mesodermal differentiation
Somatopleural tubulation
Body shape acquisition - neurulation
Ectoderm
Formation of: Neural plate (neuroectoderm) Neural groove Neural tube - will form CNS Neural crest cells (from neural tube) - will from PNS and adrenal gland
Body shape acquisition - Mesodermal differentiation
Mesoderm
Paraxial mesoderm
Intermediate mesoderm
Lateral mesoderm
Paraxial mesoderm
Next to axis - next to notochord
Somitomeres - cranial structures
Somites - axial skeleton
•Dorsal vertebrae, muscle, dermis
Intermediate mesoderm
Mesonephros
•Urinary and reproductive organs
Mesonephros - kidney
Lateral mesoderm
Divides into:
Somatopleure - attaches to ectoderm
•Thorax and abdominal structures, mesothelium, limbs
Splachnopleure - attaches to endoderm
•Epithelium and connective tissue - respiratory, digestive, thyroid, parathyroid
Body shape acquisition - tubulation or embryo folding
Tubulation of Somatopleure and Splachnopleure
Cranio-caudal folding
Lateral folding
What fluid infiltrates the morula
Embryotroph infiltrates morula and becomes the blastocoel
What is embryotroph
Substance secreted by uterine glands that serves as nutrients of the embryo at this stage
