embryology

Question 1

when is the pre-embryonic period

Answer 1

concpetion-week 2

Question 2

when is the embryonic period

Answer 2

week 2-week 8

Question 3

what are the stages f the pre-embryonic period

Answer 3

Fertilization, formation of morula and blastocyst, blastocyst implantation

Question 4

when is the foetal period

Answer 4

week 8- birth

Question 5

what are the stages of the embryonic period

Answer 5

Germ layer development, placenta development, body systems develop from trilaminar germ layers

Question 6

what are the stages of the foeatal period

Answer 6

Growth and visceral development, musculoskeletal system is functional

Question 7

what happens during fertilisation

Answer 7

1. Male spermatozoon enters the female oocyte (ovum)
2. the nuclei fuse forming a pronuclei

Question 8

what is a blastomere

Answer 8

when a fertilised oocyte splits into two cells of equal sizes

Question 9

what is a morula

Answer 9

when a blastomere divides 3 more times into 16 cells

Question 10

what is a blastocyst

Answer 10

morula reorganise to form a cavity, known as the blastocyst cavity (blastocoel). From this point, the morula is known as the blastocyst

Question 11

what are the 2 parts of a blastocyst

Answer 11

trophoblast
embyroblast

Question 12

what is a trophoblast

Answer 12

Outer cell mass (trophoblast)– contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta.

Question 13

what is an embryoblast

Answer 13

Inner cell mass (embryoblast) – responsible for the formation of the embryo itself.

Question 14

what are the overall stages of the pre-embryonic period

Answer 14

1. unfertalised oocyte
2. fertilised oocyte
3. two cell stage- blastomere
4. continual mitosis
5. morula
6. blastocyst
7. embryo hatches
8. blastocyst rotates and impplants into the endometrium

Question 15

when does the bilaminar disc form

Answer 15

week 2

Question 16

how does the bilaminar disc form

Answer 16

• the trophoblast and embryoblast divide
• The trophoblast divides into the syncytiotrophoblast and cytotrophoblast.
• The embryoblast divides into the epiblast and hypoblast, forming a two-layered structure; the bilaminar disk.

Question 17

where does the aminiotic cavity form from

Answer 17

epiblast

Question 18

when does the trilaminar disc form

Answer 18

week 3

Question 19

how does the trilaminar disk form

Answer 19

when the bilaminar disk undergoes gastrulation

Question 20

what controls gastrulation

Answer 20

the primitive streak

Question 21

what is the primitive streak

Answer 21

a groove in the midline of the epiblast

Question 22

when does the primitive streak form

Answer 22

week 3

Question 23

where is the primitive node

Answer 23

the cranial end of the primitive streak

Question 24

what is in the primitive node

Answer 24

the primitive pit

Question 25

what happens during gastrulation

Answer 25

Cells of the epiblast layer break off and migrate toward the primitive pit and form 3 new germ layers

Question 26

what are the 3 layers of the trilaminar disk

Answer 26

endoderm
mesoderm
ectoderm

Question 27

how is the endoderm formed

Answer 27

formed by epiblast cells that migrate through the primitive pit and displace the hypoblast cells.

Question 28

how is the mesoderm formed?

Answer 28

formed by epiblast cells that migrate through the primitive pit and lie between the epiblast layer and the newly created endoderm.

Question 29

how is the ectoderm formed

Answer 29

by epiblast cells that remain in position

Question 30

when does the mesoderm differentiate

Answer 30

day 20

Question 31

what does the paraxial mesoderm form

Answer 31

• forms dermatome which makes dermis layer of skin
• forms myotome which makes muscles
• forms sclerotome which makes bones and cartilage

Question 32

what does the intermediate mesoderm form

Answer 32

urogenital organs and adrenal cortex and reproductive organs

Question 33

what does the lateral plate mesoderm form?

Answer 33

• forms parietal mesoderm- parietal plura- soft tissues of arms and legs
• visceral mesoderm- visceral plura- muscle walls of gut heart and circularitory system
• intraembryonic coelom- thoracic and abdominal cavities

Question 34

what happens during week 4 fo embryo development

Answer 34

folding of the embryo

Question 35

what happens during the longitudinal folding of the embryo

Answer 35

Enlargement cranial end(vesicles of braindevelopment)

Question 36

what happens during the lateral folding of the mebryo

Answer 36

somite development

Question 37

what happens during the lateral folding of the embryo

Answer 37

somite development

Question 38

what happens during the lateral folding of the embryo

Answer 38

somite development

Question 39

what body systems develop from the endoderm?

Answer 39

epithelium
alimentary tract
parenchymal cells
mucosa of bladder, lungs

Question 40

when does neuralation occur

Answer 40

day 20

Question 41

what happens during neuralation

Answer 41

the lateral edges of the neural plate rise to form neural folds

the neural folds move towards each other and meet in the midline forming the neural tube

the mesoderm differentiates into the notochord which is a plate of cartilage

this stimulates neuralation which causes the ectoderm to thicken

this forms the central and peripheral nervous system

Question 42

what is the notochord

Answer 42

a grove within the mesoderm which stimulates neurlation

Question 43

what body systems form from the mesoderm

Answer 43

Notochord
Musculoskeletal system
Muscular layer of stomach, intestine etc
Circulatory system

Question 44

what body systems form from the ectoderm

Answer 44

Notochord
Musculoskeletal system
Muscular layer of stomach, intestine etc
Circulatory system