Fertilization and Gastrulation and Neurulation Flashcards
(109 cards)
1
Q
What is the difference between the obstetrical (clinical) calendar and the ovulatory calendar?
A
The ovulatory calendar ignores the first two weeks, where as the obstetrical calendar starts at the last menstrual period (LMP)
2
Q
How long does fertilization (embryonic stage) last?
A
8 weeks
3
Q
What is the corona radiata?
A
follicular cells around the ovum
4
Q
What is the zona pellucida and whats it important for?
A
it is the glycoprotein mesh work between the perivitelline space and corona radiata, important for fertilization
5
Q
What does the nucleus of an ovum contain?
A
The DNA egg cell, containing 23X (haploid)
6
Q
What are included in the head of a sperm and what do the components do?
A
acrosome: has enzymes to get through layers of egg acrosome-covered nucleus: Contains 23X haploid DNA
7
Q
What is important of the neck in sperm?
A
It joins the head and tail
8
Q
What does the tail of sperm do ?
A
middle piece: contains mitochondria sheath which gives sperm ATP to move
Flagella like- allows for movement
9
Q
Week 1 is the ovulatory stage, what important events occur during this?
A
Fertilization, Cleavage, Blastocyst formation, Inner cell mass (embryoblast), and implantation
10
Q
Where does fertilization occur?
A
In the ampulla
11
Q
Where does capacitation (step 1) occur and what happens?
A
it occurs in the uterus and uterine tube (takes 7 hours) glycoprotein coat and plasma proteins removed from sperm membrane allowing acrosome to react and release enzymes
12
Q
What does hyaluronidase do?
A
Released from acrosome, helps move sperm through corona radiata
13
Q
How do sperm penetrate the zona pellucida (step 2)?
A
Using esterases, acrosin, and neuraminidase
14
Q
What happens during the zona reaction?
A
Once one sperm gets into zona pellucida, a conformational change in gylcop occurs, trapping and blocking sperm from getting in (preventing polyspermy
15
Q
What happens when the sperm meets the plasma membrane of an oocyte (step 3)?
A
Sperm fuses with membrane, the head and tail enter, ***however the mitochondrial sheath does not!!
16
Q
What happens during step 4 of fertilization (3 things) ?
A
Second meiotic division complete male pronucleus forms male and femal pronuclei fuse (Zygote)
17
Q
What are the main results of fertilization (4) ?
A
1 restores diploid chromosomes (46)
2 know sex of embryo
3 activates oocyte
4 starts cleavage
18
Q
What is cleavage and when and where does it occur?
A
Cleavage increases cell #, decreases cell size, makes 2 cells to 4, to 8, forming morula occurs 30 hours after fertilization in uterine (fallopian) tube and uterus
19
Q
what is made by day 3 of cleavage and where does it go?
A
a morula with cells inside is formed, goes into uterus
20
Q
What happens on day 5 of cleavage?
A
fluid is brought into the morula, some degeneration zona pellucida to form the (early) blastocyst in the uterus
21
Q
what occurs on day 6/7 of cleavage?
A
(late) blastocyst; zona pellucida is gone, inner cell mass more defined, contained inside trophoblast, implantation to uterine wall
22
Q
What does the trophoblast become?
A
The palcenta
23
Q
Why is fertilization the most important process?
A
because assisted reporductive technologies can be used
24
Q
What occurs in vitro fertilization and embryo transfer?
A
stimulate moms ovaries, collect sperm, add to eggs, watch fertlization under microscope and then transfer 1-3 fertilized eggs and implant into mom.
25
What is cryopreservation of embryos?
take fertilized eggs and freeze them in liquid nitrogen, last for 21 years
26
What is intracytoplasmic sperm injection?
take egg cell and sperm, and inject into egg and watch in petri dish and then implant once eggs are fertilized
27
Where are embryonic stem cells retreived from and what can they become?
Retreived from the inner cell mass and can become any cell or tissue type
28
What does the trophoblast (day 7) produce to protect the embryo?
Early pregnancy factor, which is an immunosupressant produced in the first 10 days (early preg tests)
29
What does the trophoblast become and what does that do?
Becomes the cytotrophoblast, which is a stem cell layer that is mitotically active
30
What does the cytotrophoblast become and what does that do (2) ?
becomes the syncytiotrophoblast 1. releases proteolytic enzymes, responsible for implantation 2. releases chorionic gonadotropin (hCG): signal for pregnancy
31
What is a hydatidiform mole?
abnormal trophoblastic proliferation causing excessive hCG
32
How does a complete hydatidiform mole form (2)?
1. fert of an empty oocyte, duplication of the sperm 2. fert of an empty oocyte by two sperm
33
How does a partial hydatidiform mole form?
fertilization of a normal oocyte by two sperm (polyspermy block didnt work)
34
What are the clincal presentations for hydatidiform mole(4)?
Vaginal bleeding pelvic pain enlarged uterus hyperemesis gravidarum (morning sickness)
35
What is a choriocarcinoma and where can it metastasize to?
A malignant tumor which develops from hydatidiform mole (3-5% of the time), metastasizes to liver, lung, intestine, bone and brain
36
What occurs (2) during week two of development?
Bilaminar disk is formed, implantation continues (end week 2: late missed period)
37
What are the two cell types that are formed by the inner cell mass?
1. Epiblast
2. Hypoblast
38
What does the epiblast give rise to (4)?
Gives rise to the embryo, as well as ectoderm, amnion (roof) and amnion cavity
39
What does the hypoblast give rise to and what does it do? (only present during week 2!)
gives rise to extraembryonic endoderm (outside), and serves as a place holder for bilaminar disk
40
What does the hypoblast give rise to (2) and what do they do?
1. Prechordal plate: fuse to cells of epiblast, future site of the mouth (help organize head)
2. Primary and secondary yoke sac (umbilical vessicle)
41
How does the hypoblast become the primary yolk sac (umbilical vessile) and eventually the secondary yolk sac?
Hypoblast goes down and around, lining cytotrophoblast creating a loop (primary) and extraembryonic mesoderm
42
What is the difference between the primary and secondary yoke sac?
Primary yoke sac will pinch off, leading to secondary yoke sac attached to epiblast
43
When is extraembryonic mesoderm made and where is it located?
During week two, located lining the cytotrophoblast and yoke sace (different types)
44
What is the extraembryonic coelom?
the hollow cavity outside of the embryo, (empty space)
45
What does extraembryonic somatic (soma means body) mesoderm do?
Lines the trophoblast and covers the amnion, next to ectoderm
46
What does extraembryonic splanchnic (means of organs/vicera) mesoderm do?
lines the yoke sac, next to endoderm
47
What does the connecting stock do and where is it derived from?
Comes from the extraembryonic somatic mesoderm, becomes umbilical cord, forms embryonic pole, position changes
48
Where does primitive blood come from and where is it formed?
Derived from extraembryonic splanchnic mesoderm, forms in the wall of the yolk sac
49
What is the chorion derived from and what does it do?
Derived from extramebryonic somatic mesoderm, cytotrophoblast, and syncytiotrophoblast
is a layer of the palcenta
50
What is an ectopic pregnancy and what are the most common areas affected?
When the egg gets stuck in the fallopian tube
causes pain and if lets stay in fallopian tube, will rupture and cause hemorage
Commonly 'stuck' in ampullary and isthmic
51
What is placenta previa and what are the different types (3)?
when the placenta impants in the internal os of the cervix.
1. marginal placenta (minimal vaginal bleeding)
2. Partial placenta ( vaginal bleeding)
3. Total placenta previa (heavy vaginal bleeding)
52
What is important to remember if a pregnant patient presents with vaginal bleeding beyond 20 weeks gestation?
To do an ultrasound before digital exam, digital exam can cause puncture of placenta and hemorrhage
53
What happens during week 3 of development?
Gastrulation: form the 3 germ layers (all tissues, all from epiblast)
54
What does gastrulation give rise to?
Neurulation (CNS development), heart circulatory system, and brain function
55
What does ectoderm become?
hair, skin, nails, CNS, brain, spinal cord
56
what does mesoderm become?
connective tissue, muscle, bone, blood, heart & spleen
57
What does endoderm become?
Lungs, GI organs, bladder, glands (parathyroid, thyroid, tonsils)
58
When the epiblast is cut in half looking down, what is the top and what is the bottom?
The top is the head, rostral
The bottom is the tail, caudal
59
Where does the primitive streak form and what does it do?
The primitive streak forms at the caudal side and has a primitive node/ knot at top, with the primitive groove
60
What occurs in the primitive groove in caudal region?
Cells in the epiblast get proliferated, and migrate and run into eachother and push down, and encounter signals to become true endoderm (replacing hypoblast) /mesoderm, and epiblast is now ectoderm
61
What does the septum trasnversum and cardiogenic area at the most rostral end form?
The diaphram and heart
62
What are the prechordal plate and cloacal membrane made of ?
Endoderm and ectoderm
precordal (mouth n more) and cloacal (urinary/repro) will rupture to form multiple things
63
What is the notochordal tube made of?
mesoderm
64
What is sacrococcygeal teratoma and how does it occur?
A benign proliferation of cells, caused by reminance of the primitive streak, (has all 3 germ layers)
65
What is oral pharyngeal teratoma and how does it occur?
3 types of germ cells are sent to rostral part, so they migrate abnormally and or reminance of primitive streak
66
What are the three things the notochord does?
1. Longtidunal access for the embryo
2. Provides template for vertebral column (does not become)
\*\*\*\*3. Induce formation of the neural plate and formation of CNS\*\*\*\*
67
What is the start of the formation of the notochord?
Starts in primitive pit and node, mesodermal cells migrate from primitive pit to prechordal plate.
68
What happpens once the mesoderm migrate to prechordal plate to form notochordal canal?
Lined between ectoderm and endoderm (notochordal process). Notochordal canal = notochordal process will fuse with endoderm and notochordal plate, (amniotic cavity is connected to yoke sac), connection will degenrate and round back up, forming notochord proper
69
What occurs after notochord connects to endoderm?
The notochord will round up and form the notochord proper
70
What are chordomas, how do they form and where?
Form from remnants of notochord, slow growing and aggressive, occur in axial skeleton in spheno-occipital region
71
What is allantois, what is it made of, what does it do?
1. Posterior midline structure, pouch (diverticulum) from umbilical vessicle (yoke sac)
2. Made up of endoderm (because from yoke sac)
3. becomes urachus (FORMS BLADDER)
Template for the umbilical arteries and veins (does not become!)
72
What are the three other types of mesoderm, besides the notochord?
Paraxial
Intermediate
Lateral plate
73
Where is the paraxial mesoderm and what does it form?
Paraxial is on either side of the notochord, forms somites.
74
What do somites become and how?
Muscle via myotome
Skeleton via schlerotome
Dermis vis dermatome
75
Where is the intermediate mesoderm and what does it become?
it is next to the paraxial mesoderm and becomes the urogentials (kidneys and gonads)
76
Where is the lateral plate and what are the two components of the lateral plate (above intraembryonic coelom and below)?
the lateral plate is next to intermediate, above (near ectoderm) is somatic layer of the plate, below (near endoderm) is splanchnic later of plate
77
What does the somatic and splanchnic layers of the lateral plate of the mesoderm become?
blood, lymph, mesenteries and cardiovascular system
78
After the notochord is produced, how is the neural plate signaled to make neuroectoderm?
The notochord releases sonic hedge hog (SHH) to the ectoderm to induce the neural plate
79
What does the neural plate consist of?
The neural plate is the top or ectoderm layer, and consists of the neural crest and neural folds
80
What occurs in order to form the separate neural crest from the neural tube (2)?
1. The neural plate will envaginate downwards to form folds and a neural groove, as well as pronounced neural crests.
2. The neural folds with fuse and form the neural tube and canal, neural crest will be released and will migrate away
81
What is the product post- neuralation, pre-neural tube closure?
There is an ectoderm top layer (skin/hair), a neuroectoderm layer (neural tube: CNS/brain), and the migrated neural crest which migrate away (spinal ganglion)
82
Once the neural tube is formed, how is the neural tube closed?
Around the 4-5th somite, the tube fuses close in the middle, and then continues to zipper close going towards the head and tail.
83
when are the rostral neuropore and caudal neuropore closed?
day 25 rostral will close, Day 28 caudal will close, finishing primary neurulation (the closing of the brain cervical thoracic and lumbar regions)
84
What is secondary neurulation (sacral and coccyx region)?
Caudal eminence will fuse with caudal neuropore to give rise to sacrum and coccyx region
85
Where are neural crest cells mainly found and what do they give rise to?
Found in the abdomen and cranium, give rise to sensory neurons only
86
What are some examples of derivatives of neural crest cells?
Autonomic ganglia, cranial ganglia, neurilemma (schwann cells), Leptomeninges (pia mater and arachnoid mater), melanocytes, bones and cartilage of the face, walls of the aortic arteries
87
What causes Hirschprung's disease (aganglionic (megalcolon) colon)?
nueral crest cells do not migrate to the trunk/abdomen, so the infant cannot poop and colon expands
88
What causes heart defects, cleft lip/palate, DiGeorge, and dental abnormalities?
Cranial neural crest cell migration abonormalities, never received nueral crest to grow.
89
What is neuroblastoma and how does it occur?
Tumor of the adrenal medulla/ autonomic ganglia, due to migration errors of neural crest cells
90
How can albinism occur?
incorrect migration of the neural crest cells to the pigment cells (melanocytes)
91
What are the four different types of spina bifida (4)?
1. Spinal bifida occulta
2. Meningocele
3. Meningomyelocele
4. Myelocele (myeloschisis)
92
What causes the different array of spinal bifidas?
Failure of caudal neuralpore to close on time (lack of nueral arch processes?)
93
What spinal bifida causes the meningies (dura mater)/cerebral spinal fluid to be displaced out to make a sac due to lack of formation of vertebral arches? (spinal cord not in sac)
Meningocele
94
What spinal bifida causes the spinal cord to be displaced in the dura mater/ meningies cyst and causing motor problems?
Meningomyelocele
95
What spinal bifida causes a tuft of hair or dimple in 10% of people, due to an unfused vertebral arch?
Spinal bidia occulta
96
What spinal bifida causes an open spinal cord on top of the back and leading to motor & sensory deficits?
Myelocele (myeloschisis)
97
What suppliment can be taken to prevent neural tube defects such as the different spinal bifidas?
Folate
98
What is alpha-feto protein and what does it mean when the levels are increased?
made by fetus normally, when levels are increased due to meningocele, meningomyelcele, and myelocele, means there is an open nueral tube defect, which releases the fetoprotein into the amniotic fluid
99
What are the different types of congential neural tube defects (cranial)?
Anencephaly, encephalocele with briain tissue, Encephalocele without brain tissue
100
What is anencephaly and what causes it?
missing the neocortex (top of the brain) due to failure of rostral neuralpore closing at the normal time... leading to death
101
What are the differences between encephalocele with or without brain tissue?
If the encephalocele has brain tissue, child will most likely have mental issues and problems. Without brain tissue, patients can be normal
102
What consists of the miningies?
Dura mater (hard layer outside SC), pia mater (small layer covering SC), and arachnoid mater (cerebral spinal fluid between dura and pia)
103
What are the meningies derived from?
Derived from sclerotome of mesoderm, and some neural crest cells
104
What does the meninx primitiva divide into (2)?
Pachymeninx and Leptomeninges
105
What does the pachymeninx form?
The dura mater-mesoderm
106
What do the leptomeningies form?
the arachnoid and pia mater from neural crest cells
107
What can endoderm give rise to?
Thyroid gland, tonsils, Organs of GI (intestine liver pancreas bladder), lungs and trachea
108
What can the two subpopulations of ectoderm give rise to? (surface ectoderm and neuroectoderm)
Surface ectoderm: Epidermis, hair, nails, sweat glands, enamel of teeth
Neuroectoderm: (neural tube) CNS, brain, spinal cord, pituitary
Neuroectoderm (neural crest): sensory neurons (ganglia), medulla renal, pigment cells, head and neck, heart tubes
109
What happens in week 4 of development?
Everything! embyro folds, every symtem is built besides reporductive system
