Fertilization and Embryonic Development Flashcards
(99 cards)
1
Q
roughly on what day does the heart starting beeting
A
18th day
2
Q
what are the two periods within pregnancy
A
embryonic period of development and fetal period of development
3
Q
what establishes the beginnings of the placenta
A
chorionic villi
4
Q
what develops from the ectoderm (6)
A
- outer skin and associated structues like hear and nails
- nervous tissue and sense organs
- pituitary gland
- tooth enamel
- adrenal medulla
- eye lens
5
Q
what happens during the third week regarding mesoderm cells and what will this become
A
a thickened band of mesoderm cells develops along the back of the embryonic disk which will eventually become the baby’s back and come together to form the notochord
6
Q
what does the trophoblast eventually develop into
A
the chorion membrane
7
Q
what is the space that forms between the inner cell mass and the trophoblast called
A
amniotic cavity
8
Q
where do the two parts of the placenta colme from
A
chorion tissue of the embry and the other part consists of blood from the mothers circulatory system
9
Q
what are the chorionic villi
A
finger-like projections that extend from the chorion into the uterus lining
10
Q
what does the chorion enclose
A
all the other extra-embryonic membranes as well as the embryo
11
Q
whats the endocrine functions of the placenta (2)
A
secretes hormones
- allows hormones from teh fetus to diffuse into the mothers blood and hormones from the mother to diffuse into the fetus’s blood
12
Q
what is the function of the vein in the umbilical cord
A
brings oxygen rich blood to the fetus
13
Q
what are the key developmental events in the 7th and 8th week (4)
A
- embryo has distinct hman characteristics
- roughly 90% of organs and other structures are established
- organs will continue to enlarge and mature until birth
- now called a fetus
14
Q
whats teh placenta
A
a dish shaped organ within that uterus that atteches the embryo or fetus to the uterine wall and facilitates metabolic exchange
15
Q
define cleavage
A
the process of cell division without cell growth
16
Q
what are the general types of changes that occur during the fetal period of development (2)
A
- body grows rapidly
organs begin to function and coordinate to form organ systems
17
Q
whats the order of the extra-embryonic membranes from outside to inside
A
chorion, amnion, yolk sac, allantois
18
Q
whats the respiratory function of the plaenta (1)
A
transports oxygen from teh mother to the fetus and carbon diozide from the fetus to the mother
19
Q
whats the umbilical cord
A
frlexible often spirally twisted tube that connects the abodmen of a fetus to the mothers placenta in thr uterus and thorugh which nutrients are delivered and waste is expelled
20
Q
what is the general process of how body organs are formed
A
each day different rates of cell division in the primary germ layers occur which cause the tissues to fold into distinct patterns; gradually the three layered embryo is transformed into a body with separate parts
21
Q
what are the event leading up to fertilization (including males and females) (8 steps)
A
- egg is released from an ovary and swept into an oviduct
- egg is carried toward the uterus by muscular contractions and the cilia in the walls of the oviduct
- several hundred million sperm cells exit the males urethra during ejaculation
- once the sperm enters the female vagina, they make their way to the cervix, then through the uterus and finally to the oviduct into which the egg was released
- once the surviving sperm reaches the egg, its acrosome releases its enzymes to digest a path into the egg
- sperm continues to advance further until there is a path where one sperm can successfully enter the egg
- once the sperm enters the egg, the egg’s plasma membrane depolarizes to prevent any other sperms from entering
- within 12h the membranes of both disappear and fertilization is complete
22
Q
what does the chorion develop into
A
the fetal part of the placenta
23
Q
whats a morula
A
a zygote when it becomes a 16-cell sphere following repeated cleavage
24
Q
whats the mesoderm
A
the middle germ layer formed during embryogenesis
25
when do the chorionic villi extend into the uterine lining
by the end of the second week after fertilization
26
what happens to the yok sac and amniotic sac near the end of the 8th weeks
it shrinks and the amniotic sac enlarges
27
when does the baby switch from being called an embryo to a fetus
at the end of the 8th week
28
what develops from the endoderm (8)
- cellular lining of the respiratory tract, digestive tract, urinary bladder and urethra
- most of the liver
- gallbladder
- pancreas
- thymus
- part of the tonsils
- parathyroid glands
- thyroid gland
29
where does the nervous system develop from
the ectoderm that is located just above the notochord
30
is a zygote haploid or diploid
diploid
31
when does the umbilical cord ford
near the end of the 8th week
32
whats a zygote
a cell formed by the union of two gametes
33
what happens soon after neurulation begins
a reddish bulge that contains the heart forms
34
when does the secretion of hCG begin to slow and why
continues at a high level for about 2 months then it declines to a low level by the end of four months because the placenta is able to secrete sufficient estrogen and progesterone to maintain the endometrium
35
what happens to the extra-embryonic membranes and the placenta and umbilical cord during birth
after the fetus is born they are expelled from the uterus
36
define extra-embryonic membranes
any in an intricate system of membranes external to the time
37
how many veins does the umbilical cord contain
1
38
where are all the cells, tissues and organs of the body derived from and how
the primary germ layers through differntiation
39
what process marks the start of organ formation
neurulation
40
whats the immune function of the placenta (1)
transports antibodies from the mtoehr into the fetus's blood to provide passive immunity
41
when does the fetal period take place in pregnancy
from the 9th week through till birth
42
whats ectoderm
outermost germ layer formed during embryogenesis
43
how many arteries does the umbilical cord contain
2
44
what are the key developmental events in the 5th week (3)
- embryo's head is very large compared to its body
- eyes are open but they dont have eyelids or irises
- cells in the brain are differentiating very quickly
45
what are the steps of neurolation (5)
1. the notochord forms from mesoderm on the back side of the embryo
2. the neural tube starts as a plate o ectoderm just above the developing notochord
3. the edges of this plate fold inward, meeting to form a hollow tube surrounded by cells
4. the neural tube pinches off from the ectoderm and develops into the spinal cord and brain
5. cells migrate from the meeting margins of the neural tube and eventually form other organs, bone and muscles
46
what are the nutritional functions of the placenta (2)
- transports nutrients from the mothers blood to the fetus's blood
- sto9res nutrients in early pregnancy and releases them to the fetus later when fetal demand is greater than the mother can absorb from her diet
47
whats human chorionic gonadotropin
hormone secreted by the trophoblast at the time of implantation of the embryo
48
whats endoderm
the innermost germ layer formed during embryogeneis
49
what does the proximety of the mother and babys circulatory system allow for
nutrients and oxygen to diffuse from the mothers circulatory system to the developing baby and for wastes to leave the babys circualtion and enter the mothers for excretion
50
what is the embryonic disk supported by
a short stalk that connects the blastocyst with the endometrium
51
define primary germ layers
first layers of cells formed during embryogenesis
52
whats allantois
extra-embryonic membrane that forms the foundation for the umbilical cord
53
what does the chorion develolp into
the fetal part of the placenta
54
whats the outermost extra-embryonic membrane
chorion
55
what are the three primary germ layers from outer to inner
ectoderm, mesoderm, endoderm
56
how many germ layers are there
3
57
what are the common viral STIs (4)
HIV/AIDS, hepatitis ABC, genital herpes and human papilloma virus (genital warts)
58
whats a blastocyst
embryo at the stage in which it is implanted in the wall of the uterus and consists of a nearly hollow ball of cells
59
what weeks do the organs form in
between the third and eighth weeks
60
what hormone does hCG have similar effects as
LH
61
what are the functions of the arteries in the umbilical cord
they transport oxygen depleted blood from the fetus to the placenta
62
what are the 10 steps that occur between the occurence of fertilization and implantation
1. within 30h the zygote divides by mitosis for the first time to produce two new cells
2. these cells also divide forming four cells
3. these cells divide again and the process repeats very quickly
4. once it has divided into a sphere of 16 cells it becomes a morula
5. within 3-5 days it will reach the uterus
6. during this time it begins to fill with fluid that diffuses from the uterus
7. as the fluid-filled space developed two different grtoups of cells form and it becomes a blastocyst
8. between the 5th and 7th day the blastocyst attaches to the endometrium with the inner cell mass positioned against the endometrium
9. the trophoblast cells begin secreting enzymes that digest some of the tissues and blood vessels of the endometrium and the blastocyst slowly sinks into the endometrium
10. the women is now said to be pregnant
63
whats differntiation
cellular process that enables a cell to develop a particular shape and to perform specific functions that are different from the functions of other cells
64
whats neurulation
the process of forming the neural tube which develops into the brain and spinal cord
65
whats the inner cell mass
the inner cells of the blastocyst that will develop into the embryo
66
what specific structure does the baby develop in
the amniotic cavity
67
what does the chorion enclose
all the other membranes as well as the embryo
68
what is the blastocyst made up of
two groups of cells; the trophoblast and inner cell mass
69
how does the blastocyst change after the process of implantation is complete
a space begins to form between the inner cell mass and the trophoblast which soon fills with fluid
70
whats the function of the yolk sac
contributes to the formation of the digestive tract and produces the first blood cells and the future egg or sperm cells
71
whats gastrulation
the formation of the three primary germ layers in embryogenesis
72
when does implantation occur
within the first week after fertilization
73
what does the secretion of hCG prevent and why is this important
the degeneration of the corpus luteum which allows the corpus luteum to continue secreting estrogen and progesterone to maintain the endometrium and prevent menstruation
74
whats amnion
extra-embryonic membrane that forms a transparent sac that encloses and protects the embryo and fetus
75
define implantation
the process of attachment of the embryo to the endometrium
76
what are the extry-embryonic membranes responsible for
protection, nutrition, respiration and excretion of the embryo and fetus
77
define fertilization
the joining of male and female gametes to form a single cell that contains 23 chromosomes from each parent for a total of 46 chromosomes
78
when is the embryonic period/how long is it
takes place over the first eight weeks of pregnancy (2/3 of 1st trimester)
79
whats chorion
membrane developed from the trophoblast layer of the blastocyst
80
what are the key developmental events in the 6th week (3)
- brain continues rapid development
- limbs lengthen and flex slightly
- gonads are starting to produce hormones that will influnce development of external genitalia
81
when is breathing required
when the baby emerges from the uterus
82
whats the corona radiata
several jelly-like layers of follicle cells that loosely adhere to one another and surround the egg
83
whats the zona pellucida
a thin, clever layer of protein and carbohydrates surrounding the plasma membrane of the egg
84
how many layers does the embryonic disk initially consist of and what are they called
2 (ectoderm and endoderm)
85
what are the key developmental events in the 4th week (4)
- blood cells start to form and fill blood vessels
- lungs and kidneys take shape
- small buds appear that will develop into limbs
- a distinct head is visible with eveidence of eyes, ears and nose
86
whats trophoblast
the outer cell layer of the blastocyst
87
whats the excretory function of the placenta (1)
- transports wastes from the fetal blood to the mothers blood
88
what does gastrulation mark
the start of morphogenesis
89
whats the yok sac
one of the extra-embryonic membranes suspended from the abdominal area of the area
90
whats the chorion
membrane developed from the trophoblast layer of the blastocyst
91
what develops from the mesoderm (8)
- dermis of skin
- cellular lining of blood vessels, lymphatic vessels and body cavities
- muscle tissue
connective tissue including bone cartilage nad blood
- adrenal cortex
- heart
- internal reproductive organs
- kidneys and ureters
- spleen
92
what are the general types of changes that take place in the embryonic period of development (3)
- cells divide and become redistributed
- tissues and organs form
- the structures that support and nourish the developing embryo form
93
what are the common bacterial STIs (3)
chlamydia, gonorrhea and syphilis
94
what are the steps of neurulation (4)
1. cells along the sruface above the notochord begin to thicken
2. folds develop oln each side of a groove along this surface
3. the folds fuse to become a tube (called the neural tube)
4. the neural tube eventually develops into the brain and spinal cord
95
whats the embryonic disk
a flattened disk-shaped structure formed from the inner cell mass of the blastocyst during the second week after fertilization
96
whats embryogenesis
the formation and development of an embryo
97
whats another term for the inner cell mass
embryoblast
98
whats morphogenesis
the series of ebvents that form distinct structures of a developing organism
99
what happens to the inner cell mass as the amniotic cavity forms
it flattens into a disk-shaped structure
