Embryology (Organogenesis)

Question 1

The key events in cardiac development are:

Answer 1

folding of embryo and heart tube fusion

heart looping

septation and division of outflow tracts.

Question 2

cardiogenic cells developp where and it what manner

Answer 2

Cardiogenic cells develop in a horseshoe shape outside the embryo.

Question 3

how is the sinle heart tube formed and when

Answer 3

pair of
heart tubes which fuse to form a single heart tube by 21 days fertilisation;

the tube is able
to pump blood uni-directionally.

Question 4

what gives rise to the 4-

chambered structure of the normal human heart.

Answer 4

Looping of the heart tube and septation

Question 5

what are 2 unique features of the heart in development

Answer 5

foramen ovale and ductus arterious

Question 6

what does forman ovale do

Answer 6

allows blood returning to the heart (relatively high oxygen) to pass form the
RA to the LA, then to LV, then pumped though aorta to the rest of the body.

Question 7

what does ductus arterious do

Answer 7

conects Main artery
from RV to aorta

(diverts blood that would
normally go to the lungs.)

Question 8

what happens at birth to these structures

Answer 8

foramen ovale and ductus arteriosus should close, diverting blood to the lungs.

Question 9

what succesive phases are involved in kidney development

Answer 9

Pronephros= most immature form of kidney

 Mesonephros= intermediate phase

 Metanephros= most developed, persists as the definitive adult kidney.

Question 10

when does the metanephros appear

Answer 10

appears by the fifth week.

Question 11

where do the excretory units develop from

Answer 11

mesonephric mesoderm;

Question 12

where does collecting duct develop from

Answer 12

ureteric bud.

Question 13

what else does the uteric bud give rise to

Answer 13

penetrates the metanephric tissue and gives rise to the ureter, renal pelvis, major and minor
calyces and the collecting tubules.

Question 14

how do the kidneys move through development

Answer 14

initially form near the tail of the embryo but migrate upwards through the developing body to their
final place;

sending out a new and slightly more cranial branch of blood supply.

Question 15

what is the consequence of kidney movement to vasculature

Answer 15

form new connections with the developing arterial system as they move, so that renal arteries break down and re-form during this process.

Question 16

describe face developmet

Answer 16

Initially, eyes are on the side of the heads by then move inwards.

The two sides of the face
form separately at either side of the head.

Question 17

how does facial tissue move to its correct place in development

Answer 17

repeated formation of clefts in the face, and then filling in of the clefts,

leads to sequential loss of tissue from the centre of the face, and the movement of tissues to the correct places.

Question 18

what are 2 periods of lung development and what time frames do they occur

Answer 18

Saccular period= 26 weeks to birth

alveolar period= 8 months to
childhood

Question 19

when does surfactant production begin

Answer 19

early in the

third trimester and gradually increases.

Question 20

what is the clinical significance of surfactant production

Answer 20

essential for normal lung function; reduces the surface tension in
alveoli; produced by type II cells (pneumocytes).

Question 21

what happens in Respiratory distress syndrome

Answer 21

surfactant levels are low or absent so the alveoli are
unable to function.

RDS declines in incidence as amount of surfactant increases.

Question 22

give a treatment option for RDS

Answer 22

Artificial

surfactant is a good treatment as it works very quickly.

Question 23

where do they gonads initally arise from

Answer 23

intermediate mesoderm within the urogenital ridges of the embryo.

Question 24

where do they geneticl ducts arise from

Answer 24

from paired mesonephric (male) and paramesonephric (female) ducts;

Question 25

mesonephric ducts give rise to ….. which turns into reproductive tract tissue

Answer 25

wolffian (male) ducts

Question 26

paramesonephric ducts give rise to ….. which turns into reproductive tract tissue

Answer 26

mullerian (female) ducts

Question 27

when do gonadal and reproductive tracts begin to change into male/female

Answer 27

Gonads and reproductive tracts are indifferent up to 7 weeks of development

i.e. after 7 weeks

Question 28

what is gonadal/reproductive tract differentiation dependent on

Answer 28

SRY presence or absence

Question 29

what are the implications of SRY positive

Answer 29

development
proceeds towards male (7 weeks onwards)

SRY converts gonads to testes… mullerian duct breaks down and the wolffian duct is
integrated into the developing gonad. (MALES).

Question 30

what are the implications of absence of SRY

Answer 30

gonad develops into and ovary with oogonia and stromal cells.
Wolffian ducts regress

Mullerian ducts persist giving rise to the oviducts, uterus, and upper third of the vagina.

Question 31

what do leydig cells produce

Answer 31

testosterone

Question 32

what do sertoli cells produce

Answer 32

anti-

mullerian hormone.

Question 33

what is significanct about these hormones in female tract development

Answer 33

Mullerian ducts persist as there
is not anti-MH present;

Wolffian ducts regress as there is no testosterone present.

Question 34

what affect will testosterone and AMH have

Answer 34

cause male development

Question 35

what gives rise togametes in gem cells

Answer 35

Primordial germ

Question 36

where do PGC originate and migrate

Answer 36

originate in the

epiblast, but then migrate to the caudal part of the yolk sac.

Question 37

Once the main caudal

structures of the embryo have developed, the PGC migrate…..

Answer 37

through the hind gut and dorsal

mesentery to the mesonephros and then the developing gonads.

Question 38

by week 7 embryo has

Answer 38

indifferent reproductive system.

Question 39

how long does it take for SRY to cause conversion of the

indifferent system to the male tract,

Answer 39

during next 3 weeks.

Question 40

femaletract development starts later or earlier

Answer 40

later

Question 41

SRY influences

Answer 41

tract, gonadal and genital pattern

Question 42

what hormone is a key regulator of male development and what is it under the influence of

Answer 42

Testosterone under influence of hCG