Session 1 Reproduction

Question 1

Where are the primordial germ cells from ?

Answer 1

They arise from the yolk sac and they migrate into the retroperitoneum along the dorsal mesentry

Question 2

What determines the differentiation into male/ female?

Answer 2

Genotype (karyotype)

Y chromosome SRY genes (a set of SHOX transcription factors)

Question 3

How do the gonads differentiate?

Answer 3

Testis : 
Medullary cords develops 
No cortical cords
Thick tunica albuginea 
PGC -> into gonadal medulla 

Ovaries 
No medullary cords 
Cortical cord development 
No tunica albuginea 
PGC -> into gonadal cortex

Question 4

What happens to Wolffian and Müllerian duct in females?

Answer 4

Wolffian - mesonephric duct , this will regress as there is no androgen secretion from the testis

Müllerian duct - paramseonephric duct will remain as there is no Müllerian inhibiting substance

Question 5

What happens to the Wolfian and Müllerian ducts in male ?

Answer 5

Müllerian duct- degenerates as there is secretion of MIH.

Wolffian duct - persists as there is androgen secretion from the testis.

Question 6

What are parmeosneohric ducts ?

Answer 6

Invagination of the urogenital ridge
Caudally -connect with the cloaca
Cranially - open into the abdominal cavity

Derivative of future : uterus, Fallopian tube, cervix, posterior fornix and upper 1/3 of vagina

Question 7

What is the future derivative of the mesonephric duct ?

Answer 7

Mesonephric duct - vas deferens & epidydmis

Mesonephric tubules - ductus efferentes

Question 8

What are the three basic components of the external genetals?

Answer 8

Genital tubercle
Genital folds
Genital swellings

Question 9

What happens to external genetila in males?

Answer 9

Genital tubercle elongates - will ultimately be the glans penis
Genital folds come together to form the spongey urethra and the shaft of the penis
Genital swelling will form the scrotum .

This is under the influence of the dihydrotestosterone (from the testis)

Question 10

What happens to the external genitals in females.

Answer 10

Genital tubercle reverses but is the future clitoris
Genital folds do not fuse they become the labia Minora and open into the vestibule.
Genital swellings will become the future Labia majora.

Question 11

What does the gubernaculum connect in males and females?

Answer 11

Males- testis to the labioscrotal folds ( future scrotum )

Females - ovaries to the labioscrotal folds

Question 12

What is the future of the gubernaculum in females ?

Answer 12

Round ligament : this connects the labia to the uterus

Ovarian ligament : ovary to the uterus

Question 13

Why can the ovaries not descend as far?

Answer 13

This is because of the presence of the paramesonephric ducts which limits the trajectory.

Question 14

What happens in the descent of the testis ?

Answer 14

25-28 weeks testis migrate over the pubic bone behind the processus vaginalis into the future scrotum.
This migration is in the inguinal canal.

Question 15

What are the derivatives of the spermatic cord?

Answer 15

The fascia layers of the anterolateral abdominal wall , peritoneum,vas deferens , testicular nerves and vessels.

Question 16

How does variation occur in meiosis ?

Answer 16

Crossing over in P1 at chiasma
Random segregation of chromosomes
Independent assortment of homologous chromosomes

Question 17

Which cells in the testis Make testosterone?

Answer 17

Leydig cells

Question 18

What is the trajectory of sperm ?

Answer 18

Seminiferous tubules 
Rete testis (concentrate sperm) 
Ductus efferentes 
Epididymis 
Vas deferens

Question 19

What is the significance of the Barrier in the testis?

Answer 19

To prevent the immune reactions of autoimmunity

Question 20

What is the basic process of spermatogenesis?

Answer 20

Spermatogonia (Ap - destined for meiosis, Ad - for mitosis) 
Primary spermatocyte passes the Barrier
Secondary spermatocyte (Meiosis 1) 
Spermatid (Meiosis 2)
This is an immobile form of sperm 
Spermatozoa (mobile form) 

The entire process takes 70 days

Question 21

What is spermiogenesis & spermiation?

Answer 21

Spermiogenesis : the formation of spermatozoa from the spermatids. This is aided by the Sertoli cells.
Spermiation : when spermatids are released into seminiferous tubules

Question 22

What is the constituents of semen ?

Answer 22

Semen (~2ml per ejaculate)
• Seminal vesicle secretions (~70%) Amino acids, citrate, fructose,prostaglandins
• Secretions of Prostate (~25%) Proteolytic enzymes, zinc
• Sperm (via vas deferens) (2-5%) ~200-500 million per ejaculate
• Bulbourethral gland secretions Also called Cowper gland. Mucoproteins help lubricate and neutralise acidic urine in distal urethra (<1% total vol)

Question 23

What is the spermatogenic wave and cycle ?

Answer 23

The spermatogenic wave - the stages of spermiogenesis are differentiated by time along the length of the tubule
The spermatogenic cycle - the time taken for the same cells to reappear in the same place. In males this is 16 days.

Question 24

What is sperm capacitation ?

Answer 24

The removal of the glycoproteins and cholesterol in the femal genital tract so that it is able to permanent the egg.

Question 25

Outline the stages of oogeneis in utero?

Answer 25

Oogonia replicate till 3 months (mitosis)
3 months -> oogonia are surrounded by flat epithelial cells , some replicate to form primary oocytes (meiosis 1) ,Primary oocytes are arrested in P1.
Mid gestation - > Death of oogonia.
7th month -> majority of oogonia are dead only primary oocytes survive.

Primary oocytes with follicular cell surrounding are the primordial follicle.

Question 26

What happens prior to puberty in oogensis?

Answer 26

Prior to puberty the number of viable cells die and decrease from 2 million to 40,000

Question 27

Post puberty what is the pre antral stage?

Answer 27

The follicular cells around the primordial follicle -> more cuboidal -> stratified epithelium called granulosa cells.

Granulosa cells make glycoprotein called zona pelucida

Question 28

Post puberty what is the antral stage?

Answer 28

Fluid filled spaces form making the Antrum.
Theca externa -> fibrous
Theca interna -> secretory
Granulosa cells around and in front of the secondary follicle are called cumulus oophorus.

Question 29

In the antral stage which hormones do the granulosa and theca cells respond to?

Answer 29

LH - theca cells
FSH - granulosa cells

Theca cells make androgen which the granulosa make into oestrogen

Question 30

Post puberty what happens in the preovulatory stage?

Answer 30

LH surge cause meiosis 1 to be completed and the cells enter into meiosis 2 but do not complete it. (Only completed if fertilised)

During ovulation LH & FSH Surge causes the mature follicle to become a Graafian follicle (2.5cm)

Question 31

What happens in ovulation?

Answer 31

LH surge increases the collegnease activity so that oocyte can break free from ovary.
Progesterone increase the response to LH.
Fimbriae sweep over the ovary and the uterine tube contracte rhymically to draw out the oocyte and sweep it into the uterine tube.

Question 32

What happens to the remaining cells post ovulation ? (Non oocyte cells)

Answer 32

The theca and granulosa cells under the influence of LH become the corpus lute up . They become the lutein cells (yellow).
They secrete oestrogen and progesterone to stimulate the embryo for embryo implantation.

Question 33

What happens to the corpus luteum if there is no successful fertilisation in female?

Answer 33

Corpus luteum will degrade to form the corpus albicans (fibrotic)
The decrease in progesterone will cause menstural bleeding to start.

Question 34

What happens to the corpus luteum if there is fertilisation?

Answer 34

Human chorionic gonadotropin will prevent degeneration of corpus luteum.
CL will continue to make progesterone until the placenta takes over in the 4th month.

Question 35

What are the main differences in spermatogenesis and oogenesis?

Answer 35

(S) -> 200 million made a day, 4 spermatids from each division with equal cytoplasm, motile gametes, starts at puberty and continues throughout life, meiosis is completed in the testis.
(O) -> 1 every 28 days, one egg with three polar bodies and an uneven distribution of cytoplasm, non-motile gametes, starts in utero and will end when female goes through menopause, meiosis completed upon fertilisation.

Question 36

What are the key features of fertilisation ?

Answer 36

Meiosis 2 of the egg is completed

Acrosome reaction with a calcium wave to prevent polyspermy