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Flashcards in embryology Deck (20):
1

Define the stages of embryology

Pre-embryonic phase 0-3 weeks
embryonic phase 4-8 weeks
foetal phase 9-40 weeks

2

Describe the formation of the gametes and fertilisation

sperm - formed from spermatogonium by spermatogenesis haploid
ovum - formed from oogonium by oogenesis haploid
fertilisation -several sperm surround ovum , one penetrates
pro nucleus of sperm enters and fuses with pronucleus of ovum to give a diploid zygote

3

Describe the formation of the blastocyst

zygote divides by mitosis to form a morula ( solid ball of cells)
as size increases, central cells cant get nutrition by diffusion so a central cavity forms - blastocystic cavity
blastocyst made up of blastocystic cavity, inner cell mass and trophoblast ( outer lining)

4

Outline the formation of the placenta, placental villi

?

5

Describe the formation of the bilaminar disc

some of inner cell mass form a 2 layered disc - epiblast , hypoblast
2 cavities now form - amniotic cavity, yolk sac

6

Describe the formation of the trilaminar disc

epiblast cells migrate into space between epiblast and hypoblast layers
cells then displace hypoblast
forms 3 layers - ectoderm, mesoderm, endoderm

7

Understand the origin of ectoderm, mesoderm and endoderm

gastrulation - formation of 3 germ layers
epiblast cells migrate into space between epiblast and hypoblast layers
cells then displace hypoblast
forms 3 layers - ectoderm, mesoderm, endoderm

8

Describe the main structures derived from ectoderm

epidermis of skin
neural tube

9

Describe the formation of the neural tube

neurulation
primitive streak in trilaminar disc sinks and forms a solid tube = notochord
notochord secretes signals to cells
ectoderm thicknes and forms neural plate
neural plate thickens and sinks to form neural tube

10

Describe folding of the embryo and the formation of the gut tube

part of yolk sac forms cavity of inside gut - midgut
endoderm forms gut
lateral folding gives primitive gut tube
longitudinal folding gives rise to foregut and hind gut

11

Describe the origin of the lung bud

at 4 weeks gestation
forms from ventral wall of foregut
begins as median outgrowth - laryngotracheal groove
laryngotracheal groove gives rise to laryngotracheal diverticulum - this enlarges and become srleated to mesoderm to form lung bud

12

Describe the development of the bronchial tree and the formation of the alveolar sacs.

bronchial tree - pseudoglandular stage - respiration not possible
alveolar sacs - canalicular stage - respiration possible at end of this stage
terminal sac stage - maturation of lungs in utero

13

Describe the implantation of a blastocyst into the uterine wall

blastocyst requires healthy ciliated epithelium in order to reach uterine cavity
blastocyst burrows into uterine wall(endometrium)
chorion is important In burrowing - has finger like processes = chorionic villi

14

what is the result of poorly functioning ciliated epithelium?

ectopic pregnancy

15

what is the function of the chorion?

implantation - chorionic villi
forms part of placenta secretes human chorionic gonadotropin (HCG) - used to detect pregnancy

16

what is the placentas function?

foetal nutrition
transport of waste gases
immunity

17

what is function of neural tube?

goes on to form brain and spinal chord

18

Describe the main structures derived from mesoderm

dermis of skin, muscles, bones
urogenital system - kidneys , reproductive
peritoneum, pleura, body cavities

19

Describe the main structures derived from endoderm

gut
respiratory

20

what does diaphragm develop from?

septum transversum
pleurperitoneal membranes
dorsal mesentry of oesophagus
muscular ingrowth from lateral body walls