embryology

Question 1

what is embryology?

Answer 1

development of the embryo and the journey from fertilisation of the egg to the formation of a baby

Question 2

what is gestational age?

Answer 2

calculated from the mother’s last menstrual period

Question 3

what is embryological age?

Answer 3

embryological age is calculated from fertilisation

Question 4

embryogenesis

Answer 4

first 8 weeks

Question 5

foetal period

Answer 5

9-40 weeks

Question 6

where in the fallopian tubes do the sperm and egg meet?

Answer 6

ampulla

Question 7

summary of week 1

Answer 7

Fertilisation

Divisions into the morula (16 cells)

Divisions into the blastocyst (~100 cells)

blastocyst turns into the trophoblast (implantation and placenta form) and embryoblast (development of embryo)

Hatching from the Zona Pellucida.

Question 8

summary of week 2

Answer 8

Trophoblast differentiates to form the syncytiotrophoblast and the cytotrophoblast.

Embryoblast differentiates to form the epiblast and the hypoblast, which form the bilaminar disk.

Syncytiotrophoblast invades the endometrium to form the start of the placenta.

Hypoblast differentiates to form the yolk sac and the chorion.

Question 9

summary of week 3

Answer 9

Gastrulation begins and the primitive streak forms.

Epiblast differentiates into the endoderm, mesoderm, and ectoderm.

Mesoderm spreads to surrounding structures, forming the connecting stalk and the notochord.

Question 10

what process does the bilaminar disk undergo?

Answer 10

gastrulation

reorganises to start to develop the precursors to recognisable organ systems

Question 11

what is the primitive streak?

Answer 11

establishes orientation; cephalo-caudal (head to tail) and antero-posterior (front to back).

establishes symmetry

cranial end forms primitive node leads to neuralation (formation of CNS)

Question 12

what does the epiblast differentiate into?

Answer 12

ectoderm, the mesoderm, and the endoderm

known is trilaminar disk

Question 13

what is the endoderm?

Answer 13

innermost layer

lines internal organ systems - respiratory, urinary, reproductive, GI

Question 14

what is the ectoderm?

Answer 14

outermost layer

gives rise to epidermis (skin cells) and nerve tissue (neurons,, brain, spinal cord), pigmented cells (iris, retina)

Question 15

what is the mesoderm?

Answer 15

supportive tissue of internal structures - muscle, RBCs, bone

produces notochord (drives neuralation) and connecting stalk (umbilical chord)

Question 16

What are the extra-embryonic features and what are they differiated from?

Answer 16

hypoblast

yolk sac

chorion

amnion

Question 17

what does the bilaminar disk consist of?

Answer 17

epiblast and hypoblast

Question 18

what is a germ layer?

Answer 18

layer from which other developed tissues originate from

Question 19

what are the axes observed in and adult and what determines them?

Answer 19

determined by trilaminar disc

axes are anterior/posterior, dorsal/ventral, right/left

starts w/ appearance of primitive streak

Question 20

what is the cellular arrangement that occurs in primitive streak?

Answer 20

migration

invagination

Question 21

where does the primitive streak appear?

Answer 21

dorsal surface of epiblast

primitive pit is at centre of node

primitive node is at cranial end of streak

Question 22

describe migration/invagination through primitive streak

Answer 22

cells of epiblast migrate towards streak

invaginate into epiblast, pushing out hypoblast (create mesoderm)

form trilaminar disc

more cells migrating spread laterally and towards head

mesoderm forms two holes - future mouth/anus

Question 23

what is the function of notochord?

Answer 23

the notochord defines the phylum chordata

basis for axial skeleton

formation of nervous system

Question 24

how does the nucleus pulpous form?

Answer 24

prenotochordal cells of epiblast migrate through cranial part

form solid rod of cells in midline

axial skeleton forms around it from somites

regresses forms nucleus pulpous and intervertebral discs