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Anatomy YR1 > Introduction to embryology > Flashcards

Introduction to embryology Flashcards

1
Q

Anatomical terms in embryology

A

Ventral (front) and dorsal (back)
Cranial (superior) and caudal (inferior)
Rostral (superior) and caudal (inferior)

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2
Q

What are Teratogens

A

Substances that may produce physical or functional defects in the human embryo or fetid after pregnant woman is exposed to the substance

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3
Q

Gametogenesis

A

Process that converts the PGCs into mature male and female gametes

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4
Q

What is spermatogenesis

A

PGCs from week 6 of development remain dormant until puberty
At puberty, the testes mature and the PGCs differentiate into spermatogonia
Spermatogonia then undergo meiosis
Then mature to spermatozoa
This is produced from puberty till death

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5
Q

What is oogenesis

A

PGCs undergo mitosis and differentiate into oogonia in ovaries
By 5th month of development, all oogonia begun mitosis and are primary oocytes
Primary oocytes remain dormant in mitotic arrest until puberty
When puberty starts, each month a primary oocyte will mature and continue meiosis but not finish it, becoming a secondary oocyte and is ovulated
Oocyte then gets fertilised and completes meiosis

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6
Q

What is ovulation

A

Process in which an oocyte is expulsed from the ovary onto its surface

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7
Q

After how long does oocyte lose its capacity to be fertilised

A

After 24 hours

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8
Q

What are the steps from fertilisation to blastocyst

A

Sperm penetrates oocyte, the nuclei swell within the zygote and are called male and female pronuclei
Within 24 hours of fertilisation, the zygote carry out a series of mitotic cell divisions to become a morula
Zygote splits into many daughter cells (blastomeres) but does not increase in size

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9
Q

What does compaction result in

A

Morula forms 2 groups of blastomere cells

1) inner cell mass (embryo blast)
2) trophoblast

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10
Q

What is embryoblast

A

Compact mass of cells at one end of the blastocyst

Give rise to the embryo

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11
Q

What is trophoblast

A

Cells at the periphery from an epithelium

Gives rise to the feral part of placenta

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12
Q

What happens on day 5

A

Blastocyst hatches from the zona pellucida (Thick transparent membrane surrounding it)
Blastocyst can now interact with the uterine endometrium

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13
Q

What happens at the end of week 1

A

Blastocyst adhered to uterine wall
Trophoblast at the embryonic pole of the embryo proliferates
Some of these cells lose their membrane and combine forming syncytiotrophoblast
The remaining trophoblast cells that line the wall of the blastocyst are now known as cytotrophoblast
The syncytiotrophoblast fully envelopes the blastocyst

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14
Q

What is the syncytium formed when trophoblast divides

A

Syncytiotrophoblast

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15
Q

What does the inner cell mass differentiate into

A

Two epithelial layers

1) epiblast
2) hypoblast

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16
Q

Which of the epithlial layers is dorsal and which is ventral

A

Epiblast is dorsal

Hypoblast is ventral

17
Q

What is the amniotic cavity

A

Appears on the eighth day
Fluid starts to collect between the epiblast and the underlying cytotrophoblast
A layer of epiblast cells form a thin membrane that lines the cytotrophoblast and is called the amnion

18
Q

How is primary yolk sac formed

A

Hypoblast cells proliferate and migrate into blastocyst cavity

19
Q

Why is yolk sac important

A

Extraembryonic mesoderm that forms outer layer is importsnt site of haemstopoiesis in development
PGCs are first identified in the wall of yolk sac

20
Q

What happened at the end of the second week

A

Definitive yolk sac no longer with remnants of primary yolk sac
The bilaminar embryonic disc, the yolk sac and the amniotic cavity are surrounded by the chrionic cavity
The embryonic disc is connected to the cytotrophoblast by the connecting stalk

21
Q

What is ectopic pregnancy

A 
Implantation of blastocyst into abnormal sites results in an ectopic pregnancy like
Peritoneal cavity
On the surface of the ovary
Within the uterine tube
Abnormal site within the uterus
22
Q

What does gastrulation result in

A

3 primary germ layer -> foetal tissues
Bilaminar -> trilaminar. Embryonic disc
Establishment of major body axis

23
Q

What does the appearance of the primitive streak in epiblast layer do

A

Has cranial and caudal end
Divides the embryo into right and left
The bilaminar/trilaminar disc also forms the dorsal-ventral axis
Migration of epiblast cells through the primitive streak form a layer called the endoderm that replaces hypoblast
Migration of more epiblast cells through the primitive streak forms the intraembryonic mesoderm
Remaining epiblast cells now ectoderm

24
Q

What is the ectoderm

A

Germ layer that forms the covering of the body (skin) as well as the nervous systems

25
Q

What is the endoderm

A

Germ layer that forms the lining of the gastrointestinal and respiratory systems and urogenital systems and associated glands

26
Q

What is the mesoderm

A

Germ layer forms the skeletal, connective and muscle tissues of the body and some organs and glands

27
Q

How is notochord formed

A

Mesodermal cells ventral to the primitive streak form the notochord
Transient embryonic structure required to help determine the fate of the surrounding tissue
Runs the length of the embryo ventral to the ectoderm
Will become the axial skeleton

28
Q

Neurulation

A

Ectoderm differentiates into brain and spinal chord
Ectoderm overlying the notochord thickens, then folds to form a neural groove with neural folds either side
Neural folds fuse, forming a neural tube, which separates from the surface ectoderm

29
Q

What are the 3 distinct areas formed by proliferation of lateral mesoderm

A

Para-axial mesoderm
Intermediate mesoderm
Lateral plate mesoderm

30
Q

What are the two parts of the lateral plate mesoderm

A

Somatic mesoderm

Splanchnic mesoderm

31
Q

What does intermediate mesoderm formed

A

Kidneys and gonads

32
Q

What will the Somatic mesoderm form

A

Will form parietal serosa of the peritoneum, pericardium and pleura

33
Q

What will the Splanchnic mesoderm form

A

Will form the visceral serosa of the peritoneum,pericardium and pleura
Will form the layers of the GI tract wall except the inner epithelial lining

34
Q

Why does the embryonic disc get pushed into the amniotic cavity

A

Rapid development and growth of the brain and lengthening of the neural tube

35
Q

What forms the epithelial wall of gut tube

A

Endoderm layer

36
Q

What forms rest of gut tube

A

Visceral mesoderm

Anatomy YR1 (29 decks)

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