Repro- Embryology

Question 1

What is embryogenesis

Answer 1

the first 8 weeks of embyro development after fertilisation

day 5 - blastocyte
week 2-3 - bilaminar disc
week 3-4 - trilaminar (3 germ layers)
week 5-8 - organoenesis

Question 2

When does the fertilised egg form a blastocyst?

Answer 2

day 5

Question 3

How is the blastocyst organised?

Answer 3

Two cell groups

1. inner cell mass - embyroblast (develop to form baby)
2. trophoblast (develops to form the placenta)

Question 4

What does the inner cell mass of the blastocyst become?

Answer 4

Bilaminar disc (columnar epithelial cells - epiblast) and hypoblast cells

Question 5

What are the two layers of the bilaminar disc called?

Answer 5

Epiblast -> (becomes 3 germ layers after gastrulation)

Hypoblast -> (becomes extraembryonic mesoderm)

Question 6

cytotrophoblasts (outer cells of trophoblast) for what?

Answer 6

Chorionic villi (invades endometrium during implantation)

Question 7

The inner cell mass of blastocyst differientiates into the bilaminar disc

a. true
b. false

Answer 7

a. true

• epiblasts
• hypoblasts

Question 8

Two cavities form either side of the bilaminar disc, what are they called?

Answer 8

cytotrophoblasts/syncytiotrophoblasts cells (form placenta)

Epiblast cells
Hypoblast cells
——————
Yok Sac

Question 9

the inner cell mass of blastocyt forms the bilaminar disc

a. true
b. false

Answer 9

a. true

Question 10

what do epiblast cells differieniate into?

Answer 10

3 germ layers via gastrulation (trilaminar disc)

(begins with primitive streak appearing in the caudal end of the epiblast).

through this streak, cells migrate to form the
1. endoderm (displace hypoblasts)
2. mesoderm
3. remaining epiblast cells (ectoderm) do not migrate

Question 11

Ectoderm forms?

Answer 11

CNS, PNS, neuroendocrine organs , (adrenal medulla, pituitary gland)

Question 12

Which part of the mesoderm form the kidneys, utreter and gonads?

Answer 12

intermediate mesoderm

Question 13

How are diyzgotic twins formed?

Answer 13

two or more eggs are fertilised

and implanted

non-identical - genetically distinct

more common

Question 14

How are monozygotic twins formed?

Answer 14

1 embyro is split!!

identical twins

splitting of embryo determines nature of the pregnancy

Question 15

What does dichorionic diamniotic mean?

how does it occur

Answer 15

have a seperate placenta and seperate amniotic sac

THE EARLY EMBRYO SPLITS before implanting in the womb

20% of monozygotic twins

Question 16

What does monochorionic diamniotic mean?

how does it occur?

Answer 16

Share placenta and have seperate amniotic sac

Early embyro implants in the womb and then splits

75% of monozygotic twins

Question 17

What does monochorionic monoamniotic sacs?

Answer 17

Share placenta and share amniotic sac

Early embyro implants in the womb and then splits LATER ON (the later splits after implantation - the more likely to share both)

5% of monozygotic twins - BOTH are shared - high risk

Question 18

The inner cell mass of the blastocyst called the embyroblast goes through differientation into a bilaminar disc followed by a trilaminar disc through a process callled?

Answer 18

gastrulation

Question 19

beyond 8 weeks the embyronic period ends and the fetal period begins

a.true
b. false

Answer 19

a. true

embyrogenesis is the 1st eight weeks of embyro development post fertilisation

Question 20

Reproductive and renal systems have a common origin and develop from the ?

Answer 20

intermediate mesoderm

Question 21

The intermediate mesoderm develops into

Answer 21

urogenital ridge

which develops into

1. nephrogenic cord (laterally)-> kidney/ureters
2. gonadal ridge (medially)-> gonads

Question 22

Horseshoe kidney

Answer 22

fused kidney

Question 23

duplex kidney

Answer 23

two kidneys at one side

Question 24

pelvic kidney

Answer 24

kidney not ascended from pelvis during development

Question 25

The caudal end of the yok sac develops into

Answer 25

the cloaca

Question 26

the cloaca is divided by the urorectal septum to form

Answer 26

1. urogential sinus -> bladder/urethra 2. anal canal -> rectum and hindgut

Question 27

What region of the Y chromosome determines sex

Answer 27

SRY gene (SYR gene produces testes determining factor - SRY protein) SRY protein produces the testis protein acts on indifferent gonad to promote the formation of the testes

Question 28

cryptorchidism

Answer 28

undescended testicle

Question 29

what develops from the nephrogenic cord

Answer 29

kidney and ureter

Question 30

what develops from the urogenital part of the cloaca

Answer 30

bladder and urethra

Question 31

urinary system and gonads have a common origin?

Answer 31

urogenital ridge of the intermediate mesoderm

Question 32

gonads develop from the gonadal ridge a. true b. false

Answer 32

a. true

Question 33

Differientiation into testis or ovary is dictated by the presence of Y chromosome and AMH a. true b. false

Answer 33

a. True Anti-Mullerian hormone - The AMH gene provides instructions for making a protein that is involved in male sex differentiation. During development of male fetuses, the AMH protein is produced and released (secreted) by cells of the testes.

Question 34

There are two sets of genital ducts? which are undifferentiated in the embyro

Answer 34

1. mesonephric duct 2. paramesonephric duct (female duct development) in men - AMH causes Mesonephric to continue to develop (M for Men)

Question 35

the mesonephric duct forms the epididymis , vas deferns and seminal vesicles in men a. true b. false

Answer 35

a. true under effect of testosterone

Question 36

in women the paramesonephric duct continues to develop and the mesonephric duct regresses a. true b. false

Answer 36

a. true in the absence of AMH ducts grow medially and fuse -> canalise to form uterus and upper 2/3 vagina

Question 37

urogential folds form what in 1. male 2. female

Answer 37

1. spongy urethra in men 2. labia minora

Question 38

genital tubercle forms what in 1. female 2. male

Answer 38

1.clitorus 2. penis

Question 39

labioscrotal swelling forms what in 1. men 2. women

Answer 39

1. scrotum 2. labia majora

Question 40

what causes a micro-penis?

Answer 40

genital tubercle does not elongate fully

Question 41

crytochordism

Answer 41

undescended testicle

Question 42

absence of the vas deferens is common in what disease?

Answer 42

cystic fibrosis

Question 43

if the paramesonephric duct doesnt develop - there will be uterine agenesis a. true b. false

Answer 43

a. true underdevelopment or absence uterus

Question 44

why might uterine not develop

Answer 44

1. paramesonephric ducts dont develop or are underdeveloped 2. ducts do not fuse in the middle 3. ducts fuse but do not undergo cannalisation (stay as band instead)

Question 45

a rare congenital condition where the hymen membrane doesn't develop properly in the fetus, blocking the vaginal opening

Answer 45

imperforate hymen

Question 46

AMH in males causes the paramesonephric ducts to regress a. true b. false

Answer 46

a. true

Question 47

In males, paramesonephric duct develops under the effect of testosterone to form the epididymis, vas deferens and seminal vesicles a. true b. false

Answer 47

b. false the mesonephric duct!! - wolffian

Question 48

In females, the paramesonephric duct fuse to form the uterus, upper 2/3 vagina a. true b. false

Answer 48

a. true | lower 2/3 vagina is formed from the urogenital sinus

Question 49

What 3 structures form the male and female external genitilia

Answer 49

1. genital tubercle 2. urogenital folds 3. labioscrotal swelling

Question 50

Reproductive tract abnormalities are associted with renal abnormalities a. true b. false

Answer 50

a. true they can be due to common origin of intermediate mesoderm