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Flashcards in Repro 1 Deck (49)
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Describe the sexual dimorphism between the sexes.

Male - Internal
- testis
- duct system - epididymis, vas deferens, urethra.
- seminal vesicles
- prostate gland
- bulbourethral glands.

Female - Internal
- ovaries
- duct system - Fallopian tubes,uterus, cervix, vagina

Male - external
- penis
- scrotum

Female - external
- vagina
- vestibule
- labia minora/majora
- clitoris


Name two different structures the intermediate mesoderm gives rise to

Urogenital ridge
Embryonic kidney


What is the mechanism behind retroperitoneal gonadal tumours?

Primordial germ cells arise in the yolk sac and migrate along the dorsal mesentry into the retroperitoneum.
If one or a few of them get left behind, then we can see the tumour (potentially).


Give one key gene that is present on the Y chromosome, that is not present on the X chromosome, and what does the expression of this gene drive?

SRY gene on the Y chromosome.
Drives the development of:
- testis
- internal and external genitalia (male).


Is the SRY gene carried on the Y chromosome?
In its absence, what development occurs?
What must the sex of the baby be?

Yes it's carried on the Y chromosome.
In its absence, there is development of:
- ovaries
- internal and external female genitalia.


What type of tissue is the urogenital ridge derived from?

Intermediate mesoderm.


Read the following and decide whether the baby would be male or female.
-degeneration of the medullary cords
-no tunica albuginea
-cortical cords develop.

These are the developments seen in the absence of the SRY gene (hence no Y chromosome, must be 44, XX - note could have trisomies etc)


Describe the location of the paramesonephric ducts, and where do the mesonephric and paramesonephric ducts end?

The paramesonephric ducts are located near the mesonephric ducts. There don't serve any particular purpose.
They both end at the cloaca.


What two structures constitute the embryonic kidney?

Mesonephric ducts AND mesonephric tubules.


What is another name for the mesonephric ducts?

Wolffian ducts.


What maintains the presence of the mesonephric ducts?

The SRY gene.


From where do the ureteric buds sprout from?
Into which structure will these buds ultimately make their own opening?

They sprout from the mesonephric ducts and eventually they will make their own opening into the urogenital sinus.


What is the key difference in the males and females when thinking about the ureteric buds and the mesonephric ducts?

The ureteric buds still sprout from the mesonephric ducts, however the mesonephric ducts begin to regress eventually in the absence of the SRY gene.
The ureteric buds still continue to grow and make their own opening in the urogenital sinus.


What are Müllerian ducts?
Where do they appear?

These are the paramesonephric ducts
They appear as invaginations of the epithelium of the urogenital ridge.


Describe the difference between the cranial and caudal regions of the Müllerian ducts

Caudally they make contact with the cloaca
Cranial they open up into the abdominal cavity, and can be involved in PID.


From what structures is the uterus derived from?
Name an abnormality with the uterus in terms of fusion etc.

Derived from the Müllerian ducts growing towards each other and fusing.
If there is a problem with the fusion of the Müllerian ducts, can end up with a Bicornate uterus.


What exactly is a Bicornate uterus?

During fusion of the Müllerian ducts to form the uterus, there should be no septum dividing the uterus. However, if there is an abnormality with this fusion, a septum can exist that divides the uterus into two.
This is called Bicornate uterus.


What substance is secreted from the which structure that causes regression of the paramesonephric ducts?

Müllerian Inhibiting Substance is released from the Testis.
This ensures the Müllerian ducts regress.


What structures do the wolffian ducts become in man?
What is the fate of these ducts in the absence of the Y chromosome?

They become the prostate in man, and in the absence of the Y chromosome, they regress - the SRY gene keeps them but no Y chromosome = no SRY.


What are the basic components of the external genitalia at the indifferent stage?

Genital tubercle (GT)
Genital folds
Genital swellings


In terms of the external male genitalia, describe how the spongy urethra is formed.
Under what influence is this driven?

The genital tubercle elongates and the genital folds fuse together.
Influenced by the testis derived androgen hormones.


What is the fate of the genital tubercle in man and woman?

In man, it becomes the glans penis and in females it becomes the clitoris. Differentiation is normally seen around week 12.


Why do you think men get can get hernias that enter the scrotum?

The testes descend through the deep and superficial inguinal ring/canal. This means if there is an inguinal hernia, this can follow the path the testes take and end up in the scrotum.


What is cryptorchidism?

This is when the testes, on their descent into the scrotum (the future genital swelling), remain in the abdominal cavity or in the inguinal canal.
This can occur due to hormonal insufficiencies - IE androgens.


What is the fate of the part of the gubernaculum between the ovary and the uterus?

This becomes the proper ovarian ligament.


What is the fate of the gubernaculum between the labia majora and the uterus?

This becomes the round ligament of the uterus.


The prostate develops from the urogenital sinus in men.
Into what structure (s) does the urogenital sinus develop in women?

The lower 2/3 of the vagina.


If germ cells are male, where do the sex cords grow into?

Into the medullary region of the gonads. They meet the mesopheric ducts and form the definitive testis cords.


In the adult, what do the definitive sex cords develop into?

The seminiferous tubules - within which spermatogenesis occurs.


Which region of the primordial gonads do the female germ cells colonise?

The cortical region of the gonad.
Primordial follicles develop when the germ cells become surrounded by the mesenchymal cells.


Which cells secrete Müllerian inhibiting substance ?

The Sertoli cells.


Which cells produce testosterone?

The leydig cells.


Describe from which basic components at the indifferent stage, the following structures develop from in the female:
a) labia minora
b) labia majora
c) clitoria

A) labia minora - urethral folds.
B) labia majora - genital swelling
C) clitoris - genital tubercle (elongation)


Describe the abnormality in male hypospadia and the most common location

Fusion of the urethral folds is incomplete (this is the genital swelling and genital folds). The common site for this to occur is usually the inferior aspect of the penis, near the glans penis.


What are OOGONIA

These are simply primordial germ cells when they have colonised the cortex of the primordial gonad (and then proliferate)


What stimulates the OOGONIA to enter meiosis I ?

Mesonephric cells, which are known as follicular cells.


What constitutes 'primordial follicles'

Follicular cells surrounding primary oocytes.


What are OOGONIA known as, after they enter meiosis I?

Primary oocytes.


Why does meiosis I stop? Where does this substance come from?

Oocyte Maturation Inhibitor.
This is released from follicular cells.


What are the 3 stages of the mature gamete development (female)

Pre-Ovulatory Phase


Describe the 3 stages of female gamete development

1. Pre-Antral
OOGONIA enter meiosis I
- follicular cells, which surround the primary oocyte, become cuboidal and form a Granulosa layer, which secretes glycoproteins -> forms the zona pellucida.
- there is a connective tissue surrounding this called the Theca, of which there is an interna (vascular/hormone) and externa (fibrous).

2. Anthral Transition
-fluid fills in between follicular cells, forming an Antrum. This fluid filled oocyte is known them as Graafian follicles.

3. Pre Ovulatory Phase
- 37 hours before ovulation, LH receptors appear on the theca externa. - stimulation of these receptors occurs due to increase of LH.
- meiosis I completes, but only one cell gets all the cytoplasm.
- second Graafian follicle enters meiosis II but arrests in metaphase.
- meiosis II only completes if fertilisation occurs.


What enzymes causes the rupture of the follicle ?



Describe the cell types involved in converting androgens to oestrogens.

Theca interna releases androgens, due to the action of LH.
The androgens are then converted into oestrogens by the Granulosa cells, which is under the action of FSH.


Why does the corpus luteum form?

Post ovulation, the remaining follicles reorganise and form the corpus luteum. The CL secretes oestrogen and progesterone in the anticipation of a fertilised egg being implanted. This prepares the uterus.


Roughly how many NEW oocytes are made per month?

There are no new oocytes made per month. A female is born with all the eggs she will have in her lifetime. This number is roughly 400.


Which part of the primordial gonads do the germ cells proliferate in the male?

In the medulla, more specifically the seminiferous cords.


What is the fate of the seminiferous cords.

They become the seminiferous tubules, that drain into the rete testes, and then from there into the epididymis.
- there are roughly 250-750 tubules in each testes.


What are spermatogonia?

Proliferated germ cells in the male.


Outline the process of spermatogenesis

- A1 spermatogonia emerge from the stem cells.
- A1 forms more A1 and also type B spermatogonia.
- Type B cells are committed to become spermatocytes (64, after successive mitotic divisions)
- spermatocytes migrate down the seminiferous tubules where they enter meiosis, producing 256 spermatids. (64 x type B undergoing 2 meiosis = 256).
- spermiogenesis occurs when spermatids are remodelled before being washed down the rete testes by Sertoli cells.
- at some point, there is new sperm being released, producing a wave which is known as 'spermatic wave'.