Embryo

Question 1

Where frrtilization occur and What are 1st 2 of the 3 phases of fertilization

Answer 1

At ampulla
Phase1- entrance:200-500m sperm are released hundreds go to fallopian tube and capacitation occur
Phase2-attachment and penetration throgh zona pellucida: sperm glycosyltansferase attach to ZP3 receptor of ZP. And acrosomal reaction(fusion of sperm outer n inner membranes & release of enzymes(hyaluronidases and acrosin*)start
Sperm head touches secondary oocyte in metaphase of m-II and cortical reaction occurs(release of lysosomal enzymes block zp3 nd polyspermy block occurs 2nd meiotic division completes)

Question 2

3rd phase of fertilization
What occurs next
What the part of cell that comes only from mother which one from father only

Answer 2

Phase 3-Fusion of nuclei: sperm nucleus and pair of centrioles enter secondary oocyte hence all mitochondria are maternal and because oocyte loses its centrioles during mitosis therefore only source remains is sperm centrioles of making microtubule organizing center MTOC

Then secondary oocyte completes its second meiotic division and female pronucleus form
Syngamy occurs
Zygote is formed yohoo!

Question 3

How can we measure age of conceptus

Answer 3

The age of a developing conceptus can be measured either from the estimated day of fertilization (fertilization age) or from the day of the last normal menstrual period

Question 4

What are phases of mentrual cycle and their other names and major hormones during each of them
When ovulation occur

Answer 4

2 phases
1-pre-ovulatory phase- also called follicular phase(proliferative and menstrual phase)
Major hormone are FSH LH and estrogen
2- post ovulatory phase- also called luteal phase( secretory phase)
major hormone is progesterone

14th day

Question 5

What occurs during pre-ovulatory phase

Answer 5

Growing follicle consist of thica cells and granulosa cells
Thica cells bear receptors for LH and release androgen which is converted to estrogen with the help of granulose cells.
Granulosa cells bear receptors for FSH and convert androgen into estrogen
i) growing follicle estrogen acts as -ve feedback and ! Fsh
ii) dominant follicle estrogen act as +ve feedback and î fsh and Î LH and thus ovulation occur

Question 6

Function of estrogen

Answer 6

i) thicken endometrium
ii) grow endometrial glands
iii) make spiral arteries
iv) increase consistency (less thicken) of cervical mucus which is sign for ovulation

Question 7

What occurs in Post ovulatory phase(luteal phase)

Answer 7

After ovulation remnant of follicle becomes corpus luteum which release progesterone —> thicken cervical mucus and decrease FSH and LH and thus estrogen level decrease as well make endometrium secretory
With time corpus luteum is converted to corpus albicans which does not release any hormone at all and hence i) spiral arteries collapse
ii) functional layer sloughs off -> menstruation

Question 8

Different stages of conceptus with their days upto 3rd day

Which cells are totipotent
Which are pleuripotent

Answer 8

Fertilazation,zygote—> 1st day-at ampula……….2nd and 4th celled stage—> 2nd day-at fallopian tube with zp……..8 and, 16-celled-stage(morula), (each cell is called blastomere)-at fallopian tube……… division occurs+ fluid is secreted within morula-> blastocyst cavity formed and inner cell mass is called embryoblast The outer cell mass of the blastocyst is called the trophoblast—>3rd day-at fallopian tube

Blastomeres are totipotent while embryoblast cells are pleuripotent

Question 9

implantation occur 1)where 2)which layer 3) when 4) which phase

Answer 9

Posterior wall of uterus
Functional layer of endometrium
At the start of 4th day blastocyst is transferred to uterus……implant by day 7
In secretory phase(progesteronal phase)

Question 10

After implantation Trophoblast blast cells convert into ____ and what’s the difference between them.
Why failure of implantation may occur

Answer 10

The trophoblast proliferates and differentiates into the cytotrophoblast(monunucleatid and do mitosis) and syncytiotrophoblast(multinucleated and mitosis does not occur and they come from cytotrophoblast cells)
Failure of implantation may involve immune rejection (graft-versus-host reaction) of the antigenic conceptus by the mother.

Question 11

What is etp and its cause and site**

Answer 11

ETP occurs when the blastocyst implants within the uterine tube due to delayed transport.

2. The ampulla of the uterine tube is the most common site of an ectopic pregnancy. The rectouterine pouch (pouch of Douglas) is a common site for an ectopic abdominal pregnancy

Question 12

which women are more vulnerable to etp. Etp leads to ___ .. symptoms

Answer 12

ETP is most commonly seen in women with endometriosis or pelvic inflammatory disease.
4. ETP leads to uterine tube rupture and hemorrhage if surgical intervention (i.e., salpingectomy) is not performed.

5. ETP presents with abnormal uterine bleeding, unilateral pelvic pain, increased levels of human chorionic gonadotropin (hCG) (but lower than originally expected with uterine implantation pregnancy), and a massive first-trimester bleed.

Question 13

Which are similar problems like etp

Answer 13

appendicitis, an aborting intrauterine pregnancy, or a bleeding corpus luteum of a normal intrauterine pregnancy.

Question 14

By which day zona pellucida degenerate

Answer 14

Zona pellucida degeneration occurs by day 4 after conception. The zona pellucida must degenerate for implantation to occur.

Question 15

What happens by day 7 or 8, 9,11,12,14

Answer 15

By day 7 or 8—>blastocyst implants to decidua……..by day 9–>synciotrophoblast is pushed deeper to decidua bacillus……….bt day 11–>completely burried into decidua……..by day 12—>decidual reaction occurs+epithelium regenerated+EEM begins to form,………,,day 14–>syncytiotrophoblast cells protrude out called primary villi

Question 16

During 2nd week what happens to embryoblast cells .

tell all differences between layers

Answer 16

They form bilaminar embryonic disc.
Hypoblast:-1)ventral 2)cuboid cells 3)form yolk sac(initially primitive which is then converted to definitive yolk sac) 4) at the future site of the mouth, hypoblast cells become columnar shaped and fuse with epiblast cells to form a circular, midline thickening called the prochordal plate.
Epiblast:- 1)dorsal 2)columnar cells 3)forms amniotic cavity 4)becomes germ layers later

Question 17

Extraembryonic mesoderm (EEM) is formed by what and when does it form

Answer 17

Extraembryonic mesoderm (EEM) is form by cells of epiblast between cytotrophoblast and bilaminar embryonic disc

Question 18

What is decidual reaction, when it occurs

Answer 18

High progesterone—>decidual cells enlarged and coated in sugar rich fatty acids
Occurs at day 12

Question 19

What’s extraembryonic mesoderm ,from where it develops and what it generates

Answer 19

EEM is formed by epiblast between exocoelomic membrane and cytotrophoblast,,large spaces are generated which combine to form extraembryonic coelom which differentiate EEM into extraembryonic somatic mesoderm and extraembryonic visceral mesoderm

Question 20

what are EESM and EEVM.what chorion and chorionic cavity

What the relation here between conceptus and chorion

Answer 20

EESM covers cytotrophoblast and forms connecting stalk and cover amnion, EEVM covers yolk sac… chorion is seen here it consists of EESM+cytotrophoblast+synctiotrophoblast .EEC is then called chorionic cavity. Conceptus is suspended in chorionic cavity by connecting stalk

Question 21

What is HcG ,when and from where it is produced, it stimulates the production of______ which does the _______ function

Answer 21

Human chorionic gonadotropin is a glycoprotein produced by syncytiotrophoblast at day 8 and it stimulates production of progesterone which is important for maintenance of pregnancy until week 8. The placenta then takes over progesterone production

Question 22

How and when we can detect pregnancy.

What different values suggest

Answer 22

We can detect pregnancy at day 8 from blood or day 10 from urine by watching hcG . Low level suggest an ectopic pregnancy or spontaneous abortion while high level suggest multiple pregnancy ,hydatidiform mole, or gestational trophoblastic neoplasia.

Question 23

Medication to stop pregnancy untill ___

Answer 23

RU-486 (mifepristone; Mifeprex) initiates m tion when taken within 8–10 weeks of the start of the last menstrual period. If implantation of a conceptus has occurred, the conceptus will be sloughed along with the endometrium. RU-486 is a progesterone-receptor antagonist (blocker) used in conjunction with misoprostol (Cytotec; a prostaglandin E1 [PgE1 ] analogue) and is 96% effective at terminating pregnancy.

Question 24

What forms in gastrulation by day

Cells are ______potent

Answer 24

Gastrulation is the process that establishes the three definitive germ layers of the embryo (ectoderm, intraembryonic mesoderm, and endoderm), forming a trilaminar embryonic disk by day 21 of development. Cells are totipotent

Question 25

How ectoderm ,endoderm and mesoderm are formed

Answer 25

cells of epiblast separate and start migrating through the primitive streak Some of these migrating epiblast cells displace the hypoblast to form the definitive endoderm. The remainder of the epiblast cells migrates laterally, cranially, and along the midline to form the definitive intraembryonic mesoderm (e.g., cardiogenic area, notochord). After the formation of the endoderm and intraembryonic mesoderm, the epiblast is called the definitive ectoderm

Question 26

Primitive streak consists of

Axis determination is caused by ____ n ____ on which side . Which thing suppresses them

Answer 26

The primitive streak consists of the primitive groove, primitive node, and primitive pit.

As early as the bilaminar and trilaminar stages of embryogenesis, the left side/right side (L/R) axis determination begins with the asymmetric activity of sonic hedgehog protein (Shh) only on the future left side since Shh activity is suppressed on the future right side by activin. In addition, the neurotransmitter serotonin (5HT) plays an important role in L/R axis determination.
Shh is released by notochord and makes cells aware of where they are

Question 27

Paraxial mesoderm and it organizes into

Answer 27

Paraxial mesoderm is a thick plate of mesoderm located on each side of the midline. Paraxial mesoderm becomes organized into segments known as somitomeres, which form in a craniocaudal sequence. Somitomeres 1–7 do not form somites but contribute mesoderm to the pharyngeal arches. The remaining somitomeres further condense in a craniocaudal sequence to form 42–44 pairs of somites by week 5

Question 28

Somites(the day when they start ,their rate ,their final number ,differentiate into)

Answer 28

The first pair of somites forms on day 20, and new somites appear at a rate of 3 per day. The caudal-most somites eventually disappear to give a final count of approximately 35 pairs of somites. The number of somites is one of the criteria for determining the age of the embryo. Somites further differentiate into the following components:
. Sclerotome forms the cartilage and bone components of the vertebral column.
b. Myotome forms epimeric and hypomeric muscles.
c. Dermatome forms dermis and subcutaneous area of skin.

Question 29

Intermediate mesoderm

Answer 29

Intermediate mesoderm is a longitudinal dorsal ridge of mesoderm located between the paraxial mesoderm and lateral mesoderm. This ridge develops into the urogenital ridge, which forms the future kidneys and gonads.

Question 30

Lateral mesoderm

Answer 30

Lateral mesoderm is a thin plate of mesoderm located along the lateral sides of the embryo.
Large spaces develop in the lateral mesoderm and coalesce to form the intraembryonic coelom. The intraembryonic coelom divides the lateral mesoderm into two layers:

a. Intraembryonic somatic mesoderm (also called somatopleure)
b. Intraembryonic visceral mesoderm (also called visceropleure or splanchnopleure)

Question 31

Notochord

Answer 31

Notochord is a solid cylinder of mesoderm extending in the midline of the trilaminar embryonic disk from the primitive node to the prochordal plate. It has a number of important functions, which include the following:

a. The notochord induces the overlying ectoderm to differentiate into neuroectoderm to form the neural plate.
b. The notochord induces the formation of the vertebral body of each of the vertebrae.
c. The notochord forms the nucleus pulposus of each intervertebral disk.

Question 32

Cardiogenic area

Answer 32

Cardiogenic region is a horseshoe-shaped region of mesoderm located at the cranial end of the trilaminar embryonic disk rostral to the prochordal plate. This region forms the future heart.

Question 33

Ectoderm…. and which portion of body they make

Answer 33

The major change involving a specific portion of ectoderm is its induction by the underlying notochord to differentiate into neuroectoderm and neural crest .neural crest cells may be called as unofficial fourth layer because the cells of it migrate and form many structures…. CNS, PNS, sensory epithelium of ear, nose ,eyes ,mouth melanocytes of skin, sweat glands, mammary glands, pituitary gland also help making Chromaffin cells of adrenal gland,facial bones and parafollicular cells of thyroid, hair ,teeth