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MBBS IASM > Embryology > Flashcards

Embryology Flashcards

1
Q

When is considered the first day of pregnancy

A

The first day of the last period

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2
Q

What is in the head of sperm

A

Acrosome and nucleus

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3
Q

What is in the mid-piece of sperm

A

Mitochondrion (around 100)

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4
Q

What is in the tail of sperm

A

Fragella (9+2 arrangement of microtubule)

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5
Q

What is the secondary oocyte locked at

A

Metaphase II

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6
Q

Name the 2 layers the sperm has to penetrate to fertilize the ovum

A

Corona Radiata and Zona Pellucida

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7
Q

Name the 2 reactions to prevent multiple fertilzation of a single ovum

A

Cortical reaction and Zona reaction

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8
Q

What is the Cortical reaction caused by. And the effect?

A

By release of secretory granule to make the surface, or accurately, perivitelline space inpenetrable

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9
Q

What is the Zona reaction caused by and the effect

A

By hydrolytic enzyme and to remove the ligand on Zona pellucida to make it inpenentrable

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10
Q

What happens to the nuclei of the fertilized Oocyte

A

It continues the meiosis II

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11
Q

Where are the remaining nuclei formed by meiosis II of oocyte

A

They become polar body

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12
Q

What will happen after formation of oocyte nuclei

A

Approximation of pronuclei (from sperm and ovum)

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13
Q

On 8th hour, what important event happens.
What is it about
Why is it important

A

cleavage.
Forming new daughter cells (blastomeres) with little or no growth in early embryo

To restore normal cytoplasm:nucleus ratio
Active transcription and protein synthesis
Maternal recognition of pregnancy
Cell fate determination

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14
Q

What is the names when the early embryo contains 16 blastomeres and ~100 respectively

A

Morula; Blastocyst

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15
Q

What is compaction

A

Forming tight junctions betwen blastomeres to maximize cell-to-cell contact

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16
Q

What is blastogenesis
What is observable change
When does it take place

A

It means formation of blastocyst

At morula stage, cavity starts to appear

–> forming blastocyst with a well-defined inner cell mass (embryoblast) and outer cell mass which has flattened cells forming the epithelial wall of blastocyst (trophoblast)

–> On day 5,The blastocyst hatches from zona pellucida and can implant on uterus endometrium on day 6

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17
Q

Name 3 cases for monozygous twins to occur

A
  1. division of the early embryo to form 2 embryo
  2. Division of 2 inner cell mass without dividing trophoblast
  3. Incomplete division of inner cell mass to form the co-joined twins
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18
Q

What does hatching means.
What is the fate if it fails
What is the fate if it takes place too early

A

It means the blastocyst will hatch from the Zona Pellucida to get prepared for implantation.

Failure causes infertility

Too early causes ectopic implantation

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19
Q

Where should implantation take place. Where does it mostly take place in ecotopic implantation
When does it take place

A

Uterus
Tubal pregnancy (Mostly Ampulary, ie site of fertilization)
Day 6

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20
Q

What is the characterisitic of syncytiotrophoblast.
What hormone does it create

What is it’s origin

A

Syncytiotrophoblast is multinucleated, and is cancer-like and invades the endometrium of uterus

Human Chorionic Gonadotrophin (HCG)

It is by cytotrophoblast

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21
Q

What are bilaminar layer and the cavities formed

A

Epiblast –> Amniontic cavity
Hypoblast –> Yolk sac

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22
Q

What is surrounding the primitive yolk sac

A

Heuser’s membrane

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23
Q

What is formed in the syncytiotrophoblast and anastomose with maternal blood sinusoids

A

trophoblastic lacunae

24
Q

Due to a reason, there is space between the cytotrophoblast and the bilaminar disc. What is the reason and what fills up the space

A

The cytotrophoblast grows faster than the inner cell mass.

Extraembryonic mesoderm

25
Q

Within the extraembryonic mesoderm, a cavity forms. What is that cavity and what are the 2 layers forming that cavity

A

Chorionic cavity

Somatic mesoderm and splanchnic mesoderm

26
Q

What are the fate of the somatic mesoderm and splanchnic mesoderm respectively

A

Somatic mesoderm forms the chorion, the precursor of placenta

Splanchnic mesoderm: Wrap around the amniotic caivty and yolk sac

27
Q

How does the primitive yolk sac becomes definite yolk sac.

What is the fate of the primitive yolk sac

When will the 2 yolk sacs completely lose contact

A

The hypotrophoblast undergoes a second wave of proliferation to form a new membrane to push the primitive yolk sac away.

The primitive yolk sac eventually degrade into several vesicles

By the end of second week

28
Q

At the end of second week, what suspends the yolk sac and the amnion

A

Connecting stalk.

29
Q

During the embryonic period, what is formed by the movement of the epiblast .

What is the axis it is growing along and from where to where.

Which end does it elongate

What is formed by the proliferation at an end

It also forms a depression, what is it called

A

Primitive streak

Cranial-Causadal axis

It elongate at the causadal end

It forms the primitive node at the cranial end

Primitive Pit

30
Q

What is gestrulation

A

It is the migration of cells

31
Q

How is the 3 germ layers formed

A

The epiblast ingress along the primitive streak to displace some of the hypoblast cells to form the endoderm

Some epiblast ingress to the space between the endoderm and the epiblast, and becomes the mesoderm

The pre-existing epiblast becomes the ectoderm

32
Q

What will the mesoderm becomes after migation

A

To future oropharyngeal membrane
–> Cranial mesoderm

Moving slightly lateral from midline
–>Paraxial mesoderm
—-> Form somite in the future

Moving to a more caudal part
–>Intermediate mesoderm
—-> Form Urogenital mesoderm

Move laterally from caudal end of Pirmitive streak
–> Lateral plate mesoderm

33
Q

A mesoderm is split into 2 layers. Name the mesoderm, the stuff splitting that and the spilted layers

A

Lateral plate mesoderm’

Coelomic vesicle

Somatic mesoderm and Splanchnic mesoderm

34
Q

What are the fate of somatic and splanchnic mesoderm

A

They will grow and eventually meet the extraembryonic mesoderm

Where the somatic mesoderm develops into body walls

The splanchnic mesoderm forms body cavity and lining of internal organs

35
Q

Where is the notochordal process happening and what is it about.

A

Some cells ingress and go downwards to between ectoderm and endoderm in the central midline from the primitive node and pit (Notochordal process)

36
Q

Name the 2 sites that the ecoderm and endoderm are fused

A

The oropharyngeal membrane (future mouth) and the cloacal membrane (future anus)

37
Q

What is the prechordal mesoderm

A

The first group of mesoderm that arrives at oropharyngeal membrane

38
Q

What happens after the notochordal process (day 17)

A

The cells are the central undergoes apoptosis and make it hollow

39
Q

At day 18, what is formed at the base of notochordal chord

A

Notochordal plate (opening at the base of notochordal chord)

40
Q

At day 19, what will happen

A

the notochordal process and the endoderm fuses and degenerate to form a connection between the amnionic cavity and the yolk sac.

Note that as the ectoderm is the precursor of nervous system while the endoderm is the precursor of GI tract, the canal formed is alos called neuroenteric canal

41
Q

What is the fate of the remnant of the notochord

A

nucleus pulposus of interverbral disc

42
Q

What body parts are derived from the ecoderm

A

The outerlining, which includes the epidermis
And the nervous system

43
Q

What body parts does the endoderm forms

A

Majority of epithelial linings of the body, most have connections with external world

GI tract, respiratory tract, urethra

44
Q

What body parts are formed by the mesoderm

A

Bones, muscles, bone marrow, blood, blood vessel,lympathic vessel, internal reproductive organ, kidney and epithelial linings of body cavities ( pleural and peritoneal linings)

45
Q

What is neurulation

A

Both the notochord and prechordal mesoderm are able to induce part of the ectoderm to become a neural plate.

The notochord then further induces the neural plate invaginates along its central axis to form a longitudinal median neural groove, which has neural folds on each side.

So this is the neural fold, and this is the neural groove.

Eventually the neural groove will deepen more and completely detach from the ectoderm above to form the neural tube.

46
Q

What are the derivatives of the neural tube

A
  • Sensory and postganglionic
    portions of PNS
  • Adrenal medulla
  • Melanocytes of the skin
  • Connective tissues of the head
47
Q

What wil somite be divided into

A

medial part (Sclerotome): Vertbebrate and ribs

Middle part (Myotome): skeletal muscle

Lateral part (dermatome): Dermis of skin

48
Q

Where does somite grows

A

Along neural tube

49
Q

What are the derivatives of endoderm and how are they formed

A
  1. At week 3-4, it grows rapidly and foldsa around the yolk sac (cranial-caudal fold) to become a cylindral form

–> Internalizing the endoderm and is iniitated by the rapid growth of somite and lateral plate mesoderm)

During further development, endoderm gives rise to pharyngeal pouches, epithelial
lining of the lung buds and trachea, liver, gallbladder, and pancreas

50
Q

What is the origin of gametes and where are they formed.

What is the time and where will they migrate to

A

Primordial Germ Cell (PGC) in epiblast at 2nd week

They will migrate to the wall of YOLK SAC

51
Q

After migrating to yolk sac, where will the PGC move (4-6 weeeks)

A

It will migrate to the wall of gut tube and then dorsal body wall

Most populate at the level of gonads.

52
Q

In male gametogenesis, when will the PGC remain dormant till

A

From 6th week to puberty

53
Q

What are the phases of Sperm development

A

PGC derives into Spermatogonia

Spermatogonia grows and increase in size to form primary spermatocyte

Primary spermatocyte undergoes meiosis I to form secondary spermatocyte

Secondary spermatocyte undergoes meiosis II to form spermatid

Spermatid undergoes Spermiogenesis to form spermatozoa

54
Q

What does spermiogenensis involve

A

Adding acrosome
Condensation of nucleus
Forming head neck tail
Shedding most cytoplasm as Residual Body

55
Q

What is the path of PGCs before birth

A

PGC differientates to form Oogonia

Oogonia and some PGC enters prophase of meiosis I to become primary oocyte (Around month 7 most oogonia are converted)

At this stage there is a flat follicular epithelial cell surrounding the primary oocyte

Newborn babies will have primordial follicles (flat epithelial cell surrounding primary oocyte)

56
Q

What will happen to the oocyte during puberty

A

It develops into the primary follicle which has cuboidal follicular cell and well-developed ZOna pellucida
The connective tissue of ovary also becomes more organised

It then complete first meiosis to form secondary follicle.

At the secondary follicle, the Secondary oocyte has the first meiosis completed and a follicular antrium is found within the follicle

At last, a Graafian Follicle forms, which has a large space inside
The secondary oocyte is locked at metaphaseII 3h before ovulation

MBBS IASM (24 decks)

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