Block 1 090212 Embryology Introduction

Front 1

At what day does the heart start beating during human embryonic development?

Back 1

Day 20

Front 2

Before a circulation system is established, how does the embryo get nutrients?

Back 2

Through diffusion

Front 3

What are the three embryonic tissues to which all other tissues and cells are derived from?

Back 3

1. Endoderm
2. Mesoderm
3. Ectoderm

Front 4

Define malformations.

Back 4

Morphological defects resulting from intrinsic causes as in an inherited defect in a gene.

Front 5

Define Disruptions.

Back 5

morphological defect resulting from extrinsic causes such as drugs. These can NOT be inherited but can be predisposed to by inherited factors

Front 6

Define deformations.

Back 6

abnormal form resulting from mechanical forces like intrauterine pressure

Front 7

Define dysplasia.

Back 7

abnormal organization of cells into tissues

Front 8

Give the break down of children born with minor and major defects.

Back 8

14% of newborns have minor anamalies. 3% have clinically signifant (recognizable) anomalies

Front 9

What 5 factors play a role in the incidences of malformations?

Back 9

1. parental age
2. season of the year (mom eats different things, temp)
3. country of residence
4. race
5. familial tendencies

Front 10

What is a sequence and give an example of a disorder?

Back 10

pattern of defects derived form single structural defect or mechanical factor.

Ex) Pierre-robin sequence: abnormally small jaw because infants tongue falls toward back of mouth blocking airway

Front 11

What is a syndrome and give an example.

Back 11

Pattern of defects considered to be pathologically related and not know to represent a single sequence or a polytopic field defect.
Ex) fetal alcohol syndrome

Front 12

What is a polytopic field defect and give an example of a disorder.

Back 12

a pattern of defects derived from disturbance of single developmental field
Ex) DiGeorge Syndrome= a disturbance in a developmental field encompassing neural crest cells causing malformation in craniofacial, cardiac, thymic and parathymic

Front 13

What is an association?

Back 13

nonrandom occurrence in two or more indiviuals of multiple anomalies
ex) facial nerve anomalies in association with congenital hearing loss

Front 14

What are genetic factors that can cause mutations in the developing embryo?

Back 14

1. abnormal chromosome number
2. abnormal chromosome structure
3. genetic mutations (causes major multiple defects)

Front 15

What are environmental factors that can cause mutations in the developing embryo?

Back 15

1. maternal infections
2. chemical teratogens
3. physical factors
4. maternal factors
5. mechanical factors

Front 16

What is a normal birth weight and length of pregnancy?

Back 16

7.3 lbs +/- 1.3 lbs
40 wks +/- 2 wks

Front 17

What is a premature birth weight and length of pregnancy?

Back 17

<5.5 lbs and <37wks

Front 18

What is a postmature birth weight and length of pregnancy?

Back 18

>8.8lbs >42 wks

Front 19

What day does implantation occur?

Back 19

Day 6

Front 20

What 3 events must take place in order for fertilization to take place?

Back 20

1. Capacitation
2. Acrosome rxn
3. Zona rxn

Front 21

Describe capacitation.

Back 21

It prepares the acrosome to release enzymes to breakdown the zona pellucida. The preparation is when the glycoprotein coast and the seminal plasma proteins are removed from the plasma membrane

Front 22

Where does fertilization take place?

Back 22

in the ampulla of the uterine tube

Front 23

Describe the acrosome reaction.

Back 23

After contact with the zona, perforations in acrosomal wall results in the release of the enzyme hydrouronidase to breakdown the matrix around the corona radiata cells. Sperm receptor binds to ZP3 in the zona pellucida which causes the release of acrosin which breaks down the zona pellucia and allows fertillin alpha beta to interact with the oocye plasma membrane. and perivitelline space. The fusion of membranes is Ca++ dependent.

Front 24

Describe the zona reaction.

Back 24

its a change in the properties of the zona pellucida that make it impermeable to other sperm

Front 25

What does the sperm receptor bind to during the acrosme reaction?

Back 25

sperm receptor binds to ZP3 located in the zona pellucia and fertillin alphabeta

Front 26

What enzymes does the acrosome contain to penetrate the corona radiate and zona pellucida?

Back 26

Hyaluronidase and acrosin

Front 27

When is the cell considered a zygote?

Back 27

When the DNA from the egg and sperm fuse

Front 28

What is a morula?

Back 28

16 cell mass

Front 29

What is a blastocyst?

Back 29

58 cell mass

Front 30

What stage is the zygote in during implantation?

Back 30

blastocyst

Front 31

What must degrade before implantation in the uterus?

Back 31

zona pellucida

Front 32

What are the important structures of a blastocyte?

Back 32

1. inner cell mass= will become the embryo, also called embryoblast or embryonic stem cells
2. blastoceole=ECM space
3. trophoblast=

Front 33

How do 1)siamise twins, 2)identical twins sharing the same placenta form 3) identical twins not sharing the same placenta form?

Back 33

1) inner mass cells slightly separate
2) inner mass cells completely separte
3)egg splits in two after fertilization

Front 34

Describe what events take place at implantation.

Back 34

1. Blastocyst attaches to uterus throught the embryonic pole which is by the inner cell mass.
2. Tropoblast cells proliferate -->cytotrophoblast and syncytiotrophoblast layers (the layer that penetrates the endometrial epithelium and starts to invade the stroma. PBL pools in the trophoblasic lacuna for nutrients
3. a new layer of cells called hypoblasts form on top of the inner mass cells

Front 35

When do the primary villus and secondary villus form?

Back 35

The primary chorionic villi from at day 9 from the trophoblast cells and extraembryonic mesoderm appears just below the villi. The 2nd villus occurs at day 11-12.

Front 36

What is the extraembryonic coelom?

Back 36

Large space inside zygote

Front 37

What are epiblasts?

Back 37

ectodermal tissue that forms above the yolk sac and hypoblast

Front 38

What are hypoblasts?

Back 38

endodermal tissue that eventually connects and forms a ring around the yolk sac

Front 39

How can implantation be inhibited?

Back 39

Large dose of progestin: Plan B:
1. inhibit implantation by disrupting estrogen and progesterone so the uterus isn't ready
2. delay ovulation
3. inhibit ovulation
4. prevent fertilization by altering transport of sperm/ova

Front 40

How do ectopic pregnancies occur and how common are they?

Back 40

Less than 1% occurrence, but >95% of them occur in the uterine tube. Causes could be: zona pellucida degrades too quickly, infection

Front 41

What is the difference between transgenic and knockout mice?

Back 41

Transgenic: inject DNA into nuclei of a fertilized egg which will randomly incorporate into the cell genome and implant it into a mouse
knockout= transfect DNA in stem cells and inject the cells into a blastocyte which in transfersed into a mouse--->baby is chimeric which then be crossed again with the wildtype and see if their kin are knockouts

Front 42

What does the inner cell mass differentiate into?

Back 42

Hypoblasts and epiblasts

Front 43

What do the trophoblasts differentiate into?

Back 43

Cytotrophoblasts and Syncytiotrophoblasts

Front 44

What cell type invades the endometrial stroma?

Back 44

syncytiotrophoblasts