reproductive embryology

Question 1

How long can sperm survive

Answer 1

5 days

Question 2

describe the journey of an egg

Answer 2

1 - egg leaves ovary and enters fallopian tube
2 - sperm enters egg and nucleus fuses together
3 - fertilised egg divides
4 - cells attach to the uterus

Question 3

What are the steps of implantation

Answer 3

Hatching

Apposition

Adhesion

Invasion

Question 4

Describe hatching

Answer 4

The trophoectoderm cells produce protease which dissolves the zona in preparation for implantation

Question 5

Describe apposition

Answer 5

First connection between blastocyst and endometrium, apposes to microvilli like structure called pinopodes expressed on receptive endometrium

Question 6

Describe adhesion

Answer 6

The blastocyst attaches itself to the endothelial layer of the maternal endometrium - hCG begins to be secreted

Question 7

Describe invasion

Answer 7

The trophoblast proliferates, differentiates and crosses the epithelial basement membrane and invades the endometrial stroma to form the placenta - the uterine spiral arteries are remodelled by the invasive trophoblast

Question 8

What is the changes done to the endometrium prior to implantation - decidualisation

Answer 8

Stromal cell differentiation - elongated fibroblast like cells converted into decidual rounded epithelial cells

Angiogenesis

Increased inflammatory response e.g macrophages, lymphocytes and decidual leukocytes for maternal immune tolerance

Question 9

Describe gastrulation

Answer 9

-Groove appears in caudal end of the epiblast called the primitive streak
- The epiblast cells migrate into the hypoblast which displaces them, forming the endoderm
- The epiblast cells continue through the primitive streak which forms the mesoderm
- the remaining epiblast forms the endoderm

Question 10

What does the ectoderm become

Answer 10

Epidermis, CNS, PNS, hair, nails, neuroendocrine organs like the pituitary gland and enamel of teeth

Question 11

What does the mesoderm become

Answer 11

Dermis, MSK, CVS, kidneys, ureters, trigone of bladder, gonads, adrenal cortex, visceral and parietal linings e.g peritoneum

Question 12

What does the endoderm become

Answer 12

Lining of GI tract, liver parenchyma, pancreas, thyroid gland, parathyroid gland, tonsils, thymus, bladder (not trigone) and the urethra

Question 13

Describe dizygotic multiple pregnancy

Answer 13

Two or more eggs fertilising and implanting - non identical

Question 14

Describe monozygotic multiple pregnancy

Answer 14

One embryo splitting - identical twins

Question 15

What does the kidney and ureter form from

Answer 15

nephrogenic cord

Question 16

What does the ureteric duct form

Answer 16

Ureter

Question 16

What does the metanephric mesenchyme form

Answer 16

kidney

Question 16

What does the gonad form from

Answer 16

The gonadal ridge

Question 16

Where does the kidney develop

Answer 16

The pelvis and then ascends into the abdomen with the final position in the 12th week

Question 17

What does the urogenital sinus form

Answer 17

Bladder and the urethra

Question 18

What protein acts on the indifferent gonad to promote formation of testes

Answer 18

SRY protein - contained in the Y chromosome

Question 19

What does the fused portion of the paramesonephric duct form

Answer 19

the uterus and the upper 2/3rd of the vagina

Question 20

What does the unfused portions of the paramesonephric duct form

Answer 20

The fallopian tube

Question 21

What forms the lower 1/3rd of the vagina

Answer 21

urogenital sinus

Question 22

What structure elongates to form the penis

Answer 22

The genital tubercle

Question 23

What folds to form the spongy urethra

Answer 23

The urogenital folds fold anteriorly

Question 24

What do the urogenital folds form in the women

Answer 24

The albia minora

Question 25

What forms the labia majora

Answer 25

Labioscrotal folds

Question 26

What forms the clitoris

Answer 26

Genital tubercle