Embryology and fetal development Flashcards
Capacitation
A maturing process that’s the sperm go through once in the denial reproductive tract
Acrosome reaction
Enzymes from the acrosome digest outer layer of the ova
Ovum
From ovulation to fertilisation
Zygote
Fertilisation to implantation
Embryo
Implantation to the 8th week
Fetus
From 8 weeks until term
Fertilisation
The union of an oocyte and a sperm (conception)
Where does fertilisation take place
Fallopian tube
What does oestrogen cause that helps sperm cells be able to swim?
Thinning of uterine secretions
What stimulates flagella for swimming?
Prostaglandins
What prevents addition of more sperm cells into the secondary oocyte after one sperm cell has penetrated?
Changes to the egg cell membrane and zone pellucida
First trimester
1-12 weeks
Second trimester
13-27 weeks
Third trimester
28 weeks-birth
Period of mitosis when cells get smaller and smaller
Cleavage
Dividing solid mass of cells
Morula
When the morula hollows what is formed?
A blastocyst
What does the blastocyst do?
Implants into the endometrium
Blastocyst
A hollow sphere of cells that used to be a morula
When do cells of morula/blastocyst stop being pluripotent
When the blastocyst implants on the uterus
Totipotent
Cells can form all cells in the body including placental or embryonic cells
Pluripotent
Cells that can give rise to any cell types in the body (no embryonic/placental)
The cells of the blastocyst have two potential purposes
- Some become the placenta
- Others become the inner cell mass that gives rise to the embryo
Outer cell wall of the blastocyst
Trophoblast
Cells of the trophoblast
Trophoblastic cells
What happens where the trophoblastic cells touch the endometrium of the uterus?
They undergo DNA synthesis and change shape to cuboid
What happens to trophoblastic cells after DNA synthesis
They form the cytotrophoblast
Cytotrophoblast
Inner layer of the trophoblast
What do the daughter cells from trophoblast Mitosis form?
A syncytium
(Mass of tissue with a protoplasm, nuclei and a syncytiotrophoblast
Syncytiotrophoblast
Outer layer of the trophoblast
What does the endometrium of the uterus becomes what after a syncytium is formed?
Decidua
What is formed inside the blastocyst?
Inner cells mass
What do the cells of the inner cell mass divide into?
Embryonic disc
Two layers of the inner cell mass
Epiblast
Hypoblast
By day 12 what covers the blastocyst
Uterine epithelium
What hormone do trophoblast cells secrete?
Human chorionic gonadotropin (hCG)
What does hCG do?
Maintains the corpus luteum and the therefore uterine lining
Corpus luteum
Structure in ovary that secretes hormones
What hormone is secreted by the placenta for breast development?
Placental lactogen
Which hormone increases initially and then decreases and plateaus?
hCG
Which hormone levels increase through pregnancy?
Estrogens
Progesterone
What hormones are inhibited by placental estrogens and progesterone?
LH
FSH
Bilaminar disc
The epiblast and the hypoblast
What does gastrulation form?
Primitive streak
Epiblast cells heap up on the embryonic disc and spill over which forms a third layer called what?
Mesoderm
Gastrulation
Process where the inner cell mass becomes the three layer start of an embryo
What are the three layers of the epiblast following gastrulation
Ectoderm
Mesoderm
Endoderm
Neurulation
The folding process of the three layers of the epiblast and formation of a neural tube
Notocord
Transient embryonic structure that’s provides pattern for surrounding tissue
Induces change in the ectoderm
Neural tube
Forms from the ectoderm which thickens and forms a neural plate
Neural plate folds over and zips to form a tube
Becomes the brain and spinal cord
Ectoderm becomes
Nervous system
Mesoderm becomes
Muscle Bone Blood Lymphatic and blood vessels Organs
Endodermal layer becomes
Digestive and respiratory tracts
Bladder
Urethra
Hard outer covering around the blastocyst
Zona pellicida
What will the inner cell mass develop into
Embryo
What will trophoblast develop into
Placenta
Three features of the chorion membrane
Thick, opaque
Produces progesterone
Sticks to decidua
3 features of the amnion membrane
Tough, translucent
Formation of amniotic fluid
Produces prostaglandins
What is the name of the lines in the placenta?
Cotyledons
Purpose of the notocord?
Activates signalling pathways that order tissues to differentiate and develop
3 functions of placenta
Obtains nutrients and O2 for embryo
Disposed of waste products from embryo’s metabolism
Protects fetus and nurtures it
What is the immunological role of the placenta
To prevent fetal rejection
4 components required by the fetus
Amino acids-cell building
Glucose-energy
Calcium-teeth and bones
Iron- blood
Trophoblast develops an inner layer which combines with the trophoblast to form what?
Chorion
Spaces around the chorionic Villi
Lacunae
What’s the lacunae filled with
Maternal blood
Bean shaped thing in the chorion membrane of the uterus to the left of the other bean shape
Yolk sac
Bean shaped thing to the right of the other, enclosed by the chorion?
Amnion
What is inside the amnion
Amniotic cavity
Where tidied the placenta form from?
The chorion
Where is the embryo
In the amniotic cavity
Where does the amnion attach around the edge of?
Embryonic disc
Amniotic fluid function
Prevents compression if embryo and cushions it from movements of the mother
Infection barrier
Maintains temperature
Amnion membrane vs chorion
Chrorion -thick and opaque
Amnion- smooth and translucent
What hormones does the commotion produce
Progesterone
What does the amnion produce
Prostaglandins
Which membrane adheres closely to the decidua
Chorion
Amniotic fluid can be oligiohydramnious or polyhydramnious, what does this mean
Oligiohydramnious- too little amniotic fluid
Polyhydramnious-too much amniotic fluid
5 functions of amniotic fluid
Symmetrical growth of fetus Barrier to infection Stops amnion sticking to fetus Cushioning Constant temperature
Why does the distance between maternal and fetal blood get smaller?
The membrane thins as the fetus expands
What additional 2 membranes from during development
Yolk sac-gives rise to sex cells
Allantois- produces blood cells
In the villi of the chorion there are what
Maternal capillaries
Structures anterior and posterior to uterus
Bladder
Bowel
