L34

Question 1

How long is the human gestation period from fertilization? What about from last menstrual cycle?

Answer 1

266 days from fertilization

280 days menstrual cycle
2 week different

Question 2

what is the 3 stage of prenatal ?

Answer 2

pre-embryonic 0 to 2 week
embryonic 2 to 8 week
fetal periods 9 to birth

Question 3

Obstetricians commonly split the gestation period into what?

Answer 3

trimerster

they divide the 9-month period of gestation into three trimesters.

Question 4

what is the most critical stages of development

Answer 4

the first

trimester when embryonic and early fetal development is occurring

Question 5

Where specifically does fertilization occur?

Answer 5

The ampula of the Fallopian tube

Question 6

morula [ 12-16 cells ] form at which day ?

Answer 6

3 day after fertilazation

Question 7

what happen at day 4 ?

Answer 7

Early blastocyst is formed (Morula hollows out, fills with fluid, and “hatches” from the
zona pellucida ZP)

Question 8

what happen at day 7 ?

Answer 8

implanting blastocyst that consist of inner mass[ embryoblast ] and outer mass [ trophoblast]
and the The fertilization membrane (zona pellucida) has degenerated and disappeared in order for the trophoblast to implant into the uterus

Question 9

during implantation the uterus is in which phase ?

Answer 9

secretory phase [ progesterone phase ]

Question 10

Where exactly does the blastocyst implant?

Answer 10

On the posterior wall of the body of the uterus

Question 11

what happen in day 8?

Answer 11

• The trophoblast at the embryonic pole differentiates into 2 layers:- Cytotrophoblast - Syncytiotrophoblast
•
cells of the inner cell mass (embryoblast) also differentiate into two layers: - Epiblast - Hypoblast
• At the same time, a small cavity appears in the epiblast called the amniotic cavity.

Question 12

true or false

amniotic cavity apeers in hypoblast

Answer 12

false it appere in the epiblast

Question 13

What happens at day 9?

Answer 13

Amniotic cavity expands
embryo is now a bilaminar disk (Epiblast and Hypoblast thicken)
Exocoloemic cavity (primary yolk sac) forms, and the Exocoelomic membrane, made from the Hypoblast, surrounds it (it is continuous with the Hypoblast)

Question 14

What happens at days 11 and 12?

Answer 14

By the 11th- 12th day, the blastocyst is completely embedded in the endometrial stroma and uteroplacental circulation has been established.
- Extraembryonic mesoderm has been developed; soon large cavities formed in it then
become confluent to form extraembryonic coelom (chorionic cavity)………

Question 15

the extraembryonic coelom [ chorionic cavity ] sorrounds?

Answer 15

the primary yolc sack and aminotic cavity

Question 16

The somatic layer with cyto and syncytiotrophoblast form a membrane called ?

Answer 16

chorion

Question 17

what is connecting stalk ?

Answer 17

the part where it does not cover by chrionic

Question 18

This separates the extraembryonic mesoderm into 2 layers?

Answer 18

somatic layer (lining the cytotrophoblast from outside) and splamthic layer (or visceral layer) which spurrounds the primary yolk sac

Question 19

etal blood vessels develop in the?

Answer 19

horionic villi which his sorrounded by intervillous space

​^ the chorionic villi which remains form the placenta

Question 20

what is the rule of 2?

Answer 20

A way to memorize in week 2 that

the trophoblast differentiates into 2 lyres [ cyto/syncytio - trophoblast ]
the embryoblast differentiates into 2 layers[ hypoblast / epiblast]
the extrareaByronic mesoderm splits into 2 layers [ somatic layer / splamthic layer]
there are 2 yolk sacs (prim and sec)
2 new cavities form[ aminotic and chronic]

Question 21

Becoming trilaminar and establishing body axes happen in which week ?

Answer 21

third week

Question 22

What is the first major event of week 3- and arguably the MOST important part of human development?

Answer 22

Gastrulation- meaning the formation of the gut
Formation of the 3 germ layers (Endo, meso, ecto)
Provides changes in the fate of the germ layers (differentiation) and start organogenesis
Establishing body axis (cranial- caudal left-right, etc)

Question 23

Formation of x defined for the first time the major body axes.
What is x, and what body axes are they?

Answer 23

The primitive streak
Cranial caudal (head-tail)
Dorsal ventral (back belly)
Medial lateral (left right)

Question 24

what is the longitudinal midline structure in the epiblast ear the caudal end of the bilaminar disk?

Answer 24

primative streak

Question 25

the X represent area where cells are leaving the Pramative streak and moving into the interior of the embryonic disc

Answer 25

primative groove

Question 26

Epiblast cells migrate through the primitive streak by movement called ?

Answer 26

ingression

Question 27

true or false in week 2 PS moves through the midline of the Epiblast, (from caudal end - cranial) which makes the Epiblast cells migrate from the midline down towards the Hypoblast cells, and towards the lateral ends creating a primitive groove where they migrate. The Hypoblast cells are displaced and the first layer is now the Endoderm 14 -15 days . Afterwords, the Epiblast form another layer while migration creating the Mesoderrm The Epiblast that remain, are now termed Ectoderm.

Answer 27

false | week 3

Question 28

Thus the X through the process of gastrulation becomes the source of all three germ layers WHAT IS X

Answer 28

epiblast is the source of 3 germ layers

Question 29

What are the 2 membranes that have no mesoderm layers during the process of gastrulation?

Answer 29

``` The oropharyngeal membrane (cranial end and will become opening of mouth) Cloacal membrane (caudal end and will become opening of anal canal) ```

Question 30

Notochord will form from the x and is on the y

Answer 30

``` x= primative node y= midline ```

Question 31

What is the function of the notochord?

Answer 31

Primordial longitudinal axis of the embryo and gives it some rigidity. 2- Signals for the development of CNS.

Question 32

What is the fate[ مصير] of the primitive streak?

Answer 32

The primitive streak diminishes in size and becomes an insignificant structure in the sacrococygeal regionof the embryo. Normally the primitive streak undergoes degenerative changes and disappears by the end of week 4

Question 33

What is sacrococygeal teratoma?

Answer 33

A disease caused by the remanence of the primitive streak Causes a tumor to be formed which contains tissues from all germ layers as the primitive streak is remaint of Epiblast (pluripotent) Only occurs in the sacrococygeal region Good prognosis

Question 34

In extreme cases, the deficiency in caudal development leads to fusion of the lower limb buds during early development resulting in a condition called ?.

Answer 34

Sirenomelia

Question 35

What is caudal dysgenesis?

Answer 35

A group of syndromes that occur because of INSUFFICIENT mesoderm formation in the caudal region of the embryo.

Question 36

What are some characteristics of caudal dysgenesis?

Answer 36

Hypoplasia (poor formation of tissues and organs) and fusion of lower limbs Anomalies of the lumber and sacral vertebrae Agenesis of the kidney and urinary tract Agenesis or internal genital organs EXCEPT GONADS Imperforated anus In EXTREME CASES - Sirenomelia (deficiency in caudal development leads to fusion of lower limb buds during early development