Embryology, sexual differentiation and defining reproductive tracts

Question 1

Is there any differences in reproductive development in the first 5 weeks in males and females?

Answer 1

• no

- development is the same

Question 2

At 5 weeks the embryo is composed of 3 primitive germline layers. Label them in the image below using the labels below:

endoderm
ectoderm
mesoderm

Answer 2

1 = ectoderm 
2 = mesoderm
3 = endoderm

Question 3

At 5 weeks the embryo is composed of 3 primitive germline layers, then endoderm, ectoderm and mesoderm. The mesoderm has 3 separate parts, using the labels below, label them:

paraaxial mesoderm
intermediate mesoderm
lateral plate mesoderm

Answer 3

1 = paraaxial mesoderm flanking the embryo’s future vertebral column
2 = intermediate mesoderm which is just lateral to it
3 = lateral plate mesoderm which is the most lateral of all

Question 4

What is formed from the mesoderm which is how the urinary tract and reproductive system forms?

Answer 4

• urogenital ridge

Question 5

The urinary tract and reproductive system forms from the mesoderm, specially the urogenital ridge. The ridges run parallel to embryo’s future vertebral column. These then organise into a cylinder of mesoderm called what, and what are the ducts within this area called?

Answer 5

• nephrogenic cord

- nephrogenic duct

Question 6

The urinary tract and reproductive system forms from the mesoderm, specially the urogenital ridge. The ridges run parallel to embryo’s future vertebral column. These then organise into a cylinder of mesoderm called the nephrogenic cord. The majority of the nephrogenic cord will form the urinary. tract, but there is a part that will go on to form the reproductive systems, what is this called?

Answer 6

• genital/gonadal ridge

Question 7

The reproductive develops the same way in the first 5 weeks for males and females. At week 6 what happens that determines if a baby will become male or female?

Answer 7

• primordial germ cells from the wall of the yolk sac to the the gonadal ridge
• in the gonadal ridge they proliferate

Question 8

At week 6 primordial germ cells from the wall of the yolk sac to the the gonadal ridge occurs where they proliferate. In addition to this, what other important duct is formed at week 6 that will then go on to form the female reproductive tract?

Answer 8

• paramesonephric ducts

Question 9

At what week do we get the development of the male testes or the female ovaries?

Answer 9

• week 7

Question 10

What gene is responsible for providing the instructions for making the sex determining region Y protein?

Answer 10

• sex-determining region Y (SRY) gene

Question 11

The SRY gene on the Y chromosome (sex determining chromosome) is responsible for providing the instructions for making the sex determining region Y protein. What protein does the SRY gene then go onto produce, that if present determines if the embryo will develop into male or female?

Answer 11

• testis-determining factor (TFD), also referred to as the SRY protein
• if TDF is present we develop into males

Question 12

The SRY gene on the Y chromosome (sex determining chromosome) is responsible for providing the instructions for making the sex determining region Y protein. The SRY gene provides instruction for producing the protein testis-determining factor (TDF), also referred to as the SRY protein. If this protein is not present, when does the female reproductive system begin to develop?

Answer 12

• week 12

Question 13

At week 6 primordial germ cells from the wall of the yolk sac to the the gonadal ridge occurs where they proliferate and the paramesonephric ducts (female reproductive system) forms. If there is an absence of Testis-determining factor (TDF) protein the female reproductive system does not develop any further until week 12. What are the 2 processes that then take place (one of which quickly degenerates)?

Answer 13

• in the undifferentiated gonads primitive sex cords are formed (later degenerate)
• corticol cords form

Question 14

At week 6 primordial germ cells from the wall of the yolk sac to the the gonadal ridge occurs where they proliferate and the paramesonephric ducts (female reproductive system) forms. If there is an absence of Testis-determining factor (TDF) protein the female reproductive system does not develop any further until week 12. At week 12 the following occurs:

• in the undifferentiated gonads primitive sex cords are formed (later degenerate)
• cortical cords form

The female reproductive tract continues to develop between weeks 12-16. What happens to the cortical cords during this time period?

Answer 14

• cortical cords cluster together and form primordial follicles
• these then become ovarian follicles

Question 15

At what time point does the development female eggs stop until puberty?

Answer 15

• 5 months

Question 16

At birth there will be thick connective tissue capsule surrounding the ovary, what is this called?

Answer 16

• tunica albuginea

Question 17

There are two layers of the peritoneum, what are these called?

Answer 17

• parietal peritoneum = outer layer attached to the abdominal wall
• visceral peritoneum = inner layer wrapped around the internal organs

Question 18

The peritoneum is a tissue that lines your abdominal wall and covers most of the organs in your abdomen. This can be further subdivided into the parietal peritoneum (outer layer attached to the abdominal wall) and visceral peritoneum (inner layer wrapped around the internal organs). These folds can create to areas within the abdomen, placing some organs at the front and some at the back, what are these 2 areas called?

Answer 18

• intraperitoneal = situated in the intraperitoneal space lined by the peritoneum
• retroperitoneal = behind the intraperitoneal space and not lined by the peritoneum

Question 19

The peritoneum is a tissue that lines your abdominal wall and covers most of the organs in your abdomen. This can be further subdivided into the parietal peritoneum (outer layer attached to the abdominal wall) and visceral peritoneum (inner layer wrapped around the internal organs). These folds can create to areas within the abdomen, placing some organs at the front and some at the back. These are called:

• intraperitoneal = situated in the intraperitoneal space lined by the peritoneum
• retroperitoneal = behind the intraperitoneal space and not lined by the peritoneum

Are both the intra and retroperitoneal organs freely moveable?

Answer 19

• no
• intraperitoneal organs = usually mobile
• retroperitoneum organs = usually fixed to the posterior abdominal wall

Question 20

The peritoneum is a tissue that lines your abdominal wall and covers most of the organs in your abdomen. This can be further subdivided into the parietal peritoneum (outer layer attached to the abdominal wall) and visceral peritoneum (inner layer wrapped around the internal organs). These folds can create to areas within the abdomen, placing some organs at the front and some at the back, these are called:

• intraperitoneal = situated in the intraperitoneal space lined by the peritoneum
• retroperitoneal = behind the intraperitoneal space and not lined by the peritoneum

The location of the uterus means that is is also covered by the peritoneum. Is the uterus intro or retroperitoneal?

Answer 20

• body of the uterus is surrounded by peritoneum, hence it lies intraperitoneal
• rectum is posterior to the peritoneum, hence it is retroperitoneal

Question 21

The peritoneum creates a double fold over the fundus and body of the uterus, creating a false ligament, stabilising their position and anchoring them to the walls and floor of the pelvic cavity. What is this ligament called?

Answer 21

• broad ligament

Question 22

What is a mesentary?

Answer 22

• a double fold of peritoneal tissue that suspends an organ

- allows blood vessels, nerves and lymphatics to pass through

Question 23

A mesentery is a double fold of peritoneal tissue that suspends an organ. There are generally 2 key functions of the mesentery, what are they?

Answer 23

1 = suspends organs from the posterior abdominal wall, providing support and some movement
2 = provides a conduit (passage) for blood vessels, nerves and lymphatic vessels

Question 24

The peritoneum creates a double fold over the fundus and body of the uterus, creating a false ligament, stabilising their position and anchoring them to the walls and floor of the pelvic cavity, this ligament is called the broad ligament. The double fold also creates a mesentery over the fundus and body of the uterus, fallopian tubes and ovaries, providing support and a conduit for blood vessels, nerves and lymphatics. This double fold over these female reproductive system can be further subdivided into 3 sections. Using the labels below label the image:

mesovarium
mesosalpinx
mesometrium

Answer 24

1 = mesosalpinx (salinx is greek for trumpet) covers the uterine tubes
2 = mesometrium which covers the uterus 
3 = mesovarium cover the ovaries

Question 25

There are 3 main layers within each ovary, what are they?

Answer 25

1 - central zone = medulla: vascularised, hilus cells 2 - peripheral zone = cortex 3 - superficial zone = tunica albuginea

Question 26

Which cells in the ovary produces the hormones?

Answer 26

- hilus cells

Question 27

At week 6 primordial germ cells from the wall of the yolk sac to the the gonadal ridge occurs where they proliferate. In addition to this, paramesonephric ducts are formed at week 6 that will then go on to form the female reproductive tract. What hormone, when present will inhibit the development of the female reproductive tract?

Answer 27

- anti-mullerian hormone

Question 28

There are 2 major ducts that develop in male and female reproduction embryology: = paramesonephric (Mullerian) ducts = mesonephric duct Which of these ducts goes on to develop male and female reproductive organs?

Answer 28

- paramesonephric (Mullerian) ducts = female | - mesonephric duct = male

Question 29

As the paramesonephric duct develops, what happens at the cranial end of this duct?

Answer 29

- does not fuse and produces the fallopian tubes (figure B) | - opens into the peritoneal cavity (hence why covered by peritoneum)

Question 30

As the paramesonephric duct develops, the cranial end of this duct does not fuse and produces the fallopian tubes (figure B) that open into the peritoneal cavity (hence why covered by peritoneum). What happens at the caudal end of the paramesonephric ducts?

Answer 30

- they fuse and form uterus and superior vagina | - merges with the urogenital tube (will become the bladder and genital tract)

Question 31

As the paramesonephric duct develops, the cranial end of this duct does not fuse and produces the fallopian tubes (figure B) that open into the peritoneal cavity (hence why covered by peritoneum). At the caudal end of the paramesonephric ducts they fuse, forming the uterus and superior vagina. The paramesonephric duct will then fuse with the urogenital tube (will become the bladder and genital tract). What is the point at where the paramesonephric duct and urogenital tube fuse called?

Answer 31

- sinovaginal bulb

Question 32

At week 7 there is a protein present that is sequenced by a specific gene that triggers the switch from female to male reproductive development. What is the gene called and the protein that determines this distinction?

Answer 32

- SRY gene | - Testis-determining factor (TDF) is produced. If present then male gonads develop

Question 33

At week 7 primordial germ cells from the wall of the yolk sac to the the gonadal ridge occurs where they proliferate. In addition to this, what other important duct is formed at week 6 that will then go on to form the male reproductive tract?

Answer 33

- mesonephric duct

Question 34

At week 6 primordial germ cells from the wall of the yolk sac to the the gonadal ridge occurs where they proliferate and the mesonephric ducts (male reproductive system) forms. The mesonephric duct then lead to the development of sex cords into what cord?

Answer 34

- testicular cords | - will eventually become the vas deferens

Question 35

At week 6 primordial germ cells from the wall of the yolk sac to the the gonadal ridge occurs where they proliferate and the mesonephric ducts (male reproductive system) forms. The mesonephric duct then lead to the development of sex cords into testicular cords, which will eventually become the vas deferens. What then happens to the testicular cords?

Answer 35

- detachment from outer mesothelium where tunica albuginea develops - septum begins to develop

Question 36

At week 7 the testicular cords detach from the mesothelium, which will then form the tunica albuginea, followed by the development of the septum. further development leads to the formation of the following structures, label them on the image below using the labels: ``` rete testis seminiferous tubules efferent tubule mesonephric duct tunica albuginea septa ```

Answer 36

``` 1 = tunica albuginea 2 = seminiferous tubules 3 = rete testis 4 = efferent tubule 5 = mesonephric duct 6 = septa (divides testes into lobules) ```

Question 37

Seminiferous tubules develop from the primordial sex cords and are located within the testes. What is the function of the seminiferous tubules?

Answer 37

- location where meiosis takes place, and subsequent creation of male gametes

Question 38

As the testes develop, seminiferous tubules form, which is the location where meiosis and male gametes (sperm) are formed and the efferent tubules form that are thin parallel delicate tubules that connect to the epididymis. In between the seminiferous and efferent tubules a plexus forms that acts as a reservoir and collects sperm. What is this 'reservoir' called?

Answer 38

- rete testes

Question 39

Seminiferous tubules develop from the primordial sex cords and are located within the testes, and are the location where meiosis takes place, and subsequent creation of male gametes. What are the 2 key cells we need to be aware of within the seminiferous tubules?

Answer 39

1 - leydig cells | 2 - sertoli cells

Question 40

Leydig cells are one of the key cells that are present in the testes. What is the function of these cells?

Answer 40

- secrete testosterone and androgen

Question 41

Leydig cells are one of the key cells that are present in the testes and secrete testosterone, which is essential for the development of spermatozoa. What hormone are the leydig cells reliant on in order to secrete testosterone?

Answer 41

- luteinizing hormone (LH) | - secreted by anterior pituitary gland

Question 42

Sertoli cells are one of the key cells that are present in the testes. What are the 2 key function of these cells?

Answer 42

1 - provide nutrients to developing spermatogonia | 2 - contribute to testes blood barrier

Question 43

Sertoli cells are one of the key cells that are present in the testes that provide nutrients to developing spermatogonia and contribute to testes blood barrier. In addition they are also crucial for secreting what 2 things?

Answer 43

1 - Anti-Müllerian hormone (AMH) inhibits female reproduction development 2 - androgen binding protein (Follicle-Stimulating Hormone (FSH))

Question 44

Sertoli cells are one of the key cells that are present in the testes that provide nutrients to developing spermatogonia and contribute to testes blood barrier. In addition they are also crucial for secreting androgen binding protein which is dependent on the levels of Follicle-Stimulating Hormone (FSH)). What is the important role of androgen binding protein in the testes?

Answer 44

- binds to testosterone | - ensure it remains in the seminiferous tubules

Question 45

The testes once developed will descend from the posterior abdominal wall into where by weeks 9-12, which is before it reaches the scrotum?

Answer 45

- inguinal canal via the deep inguinal ring

Question 46

The testes once developed will descend from the posterior abdominal wall into where by weeks 9-12, into the deep inguinal ring. By aprox week 32 to term, where will the testes then move to?

Answer 46

- scrotum

Question 47

The mesonephric duct is what forms the male testes. During development what does the mesonephric duct go on to develop caudally and cranially?

Answer 47

- caudally = thickens and forms ductus deferens/vas deferens | - cranially = becomes convoluted forming the epididymis

Question 48

As the female reproductive system develops we can have abnormalities. What is double uterus?

Answer 48

- instead of 1 uterus, 2 form | - patient will have 2 uterus and 2 cervix, but 1 vagina

Question 49

As the female reproductive system develops we can have abnormalities. What is bicornuate uterus?

Answer 49

- uterus has abnormality at fundus, which separates

Question 50

As the female reproductive system develops we can have abnormalities. What is septate uterus?

Answer 50

- wall has formed in uterus | - creates separation in the uterus

Question 51

As the female reproductive system develops we can have abnormalities. What is unicornuate uterus?

Answer 51

- half of the uterus develops

Question 52

As the male reproductive system develops we can have abnormalities. What is cryptorchidism?

Answer 52

- cryptos = greek for "hidden" - orchis =greek for meaning "testis" - when one or two testes do not descend into the scrotum

Question 53

As the male reproductive system develops we can have abnormalities. What are ectopic testes?

Answer 53

- testes descends as normal but not to scrotum

Question 54

As the male reproductive system develops we can have abnormalities. What is hydrocele?

Answer 54

- swelling in the scrotum | - occurs when fluid collects in the thin sheath surrounding a testicle

Question 55

As the male reproductive system develops we can have abnormalities. What is congenital inguinal hernia?

Answer 55

- a sac-like projection of the abdominal cavity extends down the groin on one or both sides toward the scrotum

Question 56

What is oogenesis?

Answer 56

- the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilised - it is developed from the primary oocyte by maturation - oogenesis is initiated in the embryonic stage

Question 57

What is the origin of the gametes which will ultimately become oocytes and spermatozoa?

Answer 57

- primordial germ cells | - developed from the bilaminer disk (epiblasts)

Question 58

Once the primordial cells have migrated to the genital ridge they determine if the embryo will develop into a male or female. What do the primordial cells then become as part of oogenesis?

Answer 58

- oogonia which then enlarges | - oogonia cells undergo meiosis to increase in number

Question 59

Once the oogonia increase in number due to meiosis they will then develop into primary oocytes. Each cell then becomes wrapped up in what?

Answer 59

- epithelial cells, called follicular cells | - this cell is referred to as a primordial follicle

Question 60

Once the oogonia increase in number due to meiosis they will then develop into primary oocytes. Each cell then becomes wrapped up in what?

Answer 60

- epithelial cells, called follicular cells | - this cell is referred to as a primordial follicle

Question 61

Once we have our primordial follicles, this remains at this stage at birth and will not change until what point?

Answer 61

- puberty

Question 62

Once a female reaches puberty the primordial follicle will begin what cycle?

Answer 62

- ovarian cycle

Question 63

Once a female reaches puberty the primordial follicle will begin what ovarian cycle. The follicular cells surrounding the gamete will then change from squamous epithelial cells into what type of cells?

Answer 63

- increase in size resembling cuboidal cells

Question 64

Once a female reaches puberty the primordial follicle will begin what ovarian cycle. The follicular cells surrounding the gamete will then change from squamous epithelial cells, increasing in size and resembling cuboidal cells. This process will lead to the formation of what, and what hormone drives this development?

Answer 64

- forms primary follicle | - Follicle-Stimulating Hormone (FSH) drives the development

Question 65

Once the primary follicle has been formed, driven by Follicle-Stimulating Hormone (FSH), we are left with a gamete in the middle surrounded by cuboidal epithelial cells. There is a layer between the gamete and cuboidal cells, what is this called?

Answer 65

- zona pellucida

Question 66

Once we have formed the primary follicle this will continue to develop into a secondary follicle, also driven by the hormone Follicle-Stimulating Hormone (FSH). What is the major difference between the primary and secondary follicle?

Answer 66

- secondary follicle continue to develop with fluid filled space - fluid filled space is called follicular antrum

Question 67

Once we have formed the secondary follicle that contains the fluid filled space called the follicular antrum, what does the secondary follicle develop within?

Answer 67

- a graafian follicle | - follicular antrum increases in size

Question 68

Once we have formed the secondary follicle that contains the fluid filled space called the follicular antrum. The secondary follicle then develops within a graafian follicle and the follicular antrum increases in size. At this point there is a layer of cells surrounding the zone pelucida. What is this layer called?

Answer 68

- corona radiata

Question 69

What is ovulation?

Answer 69

- release of a mature oocyte from the ovaries | - will remain in the fallopian tubes for 12-24 hours

Question 70

What happens to the graafian follicle during ovulation?

Answer 70

- oocyte is released from the ovaries into the fallopian tubes - oocyte is surrounded by zona pelucida and the corona radiata

Question 71

What hormone is ovulation dependent on?

Answer 71

- Luteinizing Hormone (LH)

Question 72

What are granulosa cells?

Answer 72

- cells that form a single layer around the oocyte in the primordial ovarian follicle

Question 73

Granulosa cells form a single layer around the oocyte in the primordial ovarian follicle. What do these cells secrete that is involved in ovulation?

Answer 73

- estrogen - increased estrogen level inhibit Follicle-Stimulating Hormone (FSH) - reduced FSH causes increased Luteinizing Hormone (LH) causing ovulation

Question 74

Ovulation is the release of a mature oocyte into the fallopian tubes from the Graafian follicle within the ovaries. This causes the cortex of the ovaries to rupture causing a haemorrhage. The cells surrounding the haemorrhage, which will include the cells of the Graafian follicle then do what?

Answer 74

- collapse and forms the corpus luteum

Question 75

Ovulation is the release of a mature oocyte into the fallopian tubes from the Graafian follicle within the ovaries. This causes the cortex of the ovaries to rupture causing a haemorrhage. The cells surrounding the haemorrhage, which will include the cells of the Graafian follicle then collapse and forms the corpus luteum. What hormone stimulates the formation of the corpus luteum?

Answer 75

- luteinizing hormone (LH)

Question 76

Ovulation is the release of a mature oocyte into the fallopian tubes from the Graafian follicle within the ovaries. This causes the cortex of the ovaries to rupture causing a haemorrhage. The cells surrounding the haemorrhage, which will include the cells of the Graafian follicle then collapse and forms the corpus luteum. Luteinizing hormone (LH) stimulates the formation of the corpus luteum and also signals the release of what other hormone that is important in preparing the uterus for pregnancy?

Answer 76

- progesterone

Question 77

Once progesterone levels increase to prepare the uterus for pregnancy following the release of the oocyte into the fallopian tubes, what 2 hormones does progesterone also provide a negative feedback loop for and the phagocytosis of what?

Answer 77

- luteinizing hormone (LH) - follicle-stimulating hormone (FSH) - phagocytosis of corpus luteum

Question 78

Once progesterone levels increase to prepare the uterus for pregnancy following the release of the oocyte into the fallopian tubes, progesterone provides a negative feedback loop for luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This also results in the phagocytosis of the corpus luteum, leaving what?

Answer 78

- corpus albicans | - fibrotic scar that will remain in the ovaries

Question 79

What is a primitive sperm cell called?

Answer 79

- spermatogonia | - small number prior to sexual maturity

Question 80

What happens to the spermatogonia during puberty in males?

Answer 80

- mitotic division of spermatogonia (spermatocytes) | - spermatocytes then undergo meiosis to form gametes (spermatids/spermatozoa)

Question 81

Where does the majority of the spermatogenic series take place in males?

Answer 81

- seminiferous tubules of the testes | - final stage occurs in the epididymis

Question 82

Which hormone is the whole spermatogenic series dependent on?

Answer 82

- testosterone

Question 83

Testosterone is crucial for the whole spermatogenic series. However, what 2 hormones released by the anterior pituitary gland modulate the levels testosterone?

Answer 83

1 - luteinizing hormone (LH) | 2 - follicle-stimulating hormone (FSH)

Question 84

The spermatogonia, which are primitive germ cells are located where in the seminiferous tubules of the testes?

Answer 84

- outer wall | - during the spermatogenic series they migrate towards centre of lumen

Question 85

The spermatogonia, which are primitive germ cells are located in the outer wall of the seminiferous tubules, where they will migrate towards centre of lumen during the spermatogenic series. This cell will undergo mitosis and form type A and B cells. What is the role of the type A and B cells?

Answer 85

- type A = continually undergo mitosis to maintain germ pool | - type B = undergo mitosis and form primary spermatocytes

Question 86

Once the type B spermatocyes have been formed, they undergo meiosis 1 and become secondary spermatocyes. How many copies of chromosomes do they possess at this stage?

Answer 86

- start of meiosis cells contain 2 lots of chromosome (n=4) - end of meiosis I cells contain 1 lot of chromosomes (n=2) - which is the normal amount in an adult cell = DIPLOID

Question 87

Once the type B spermatocyes have been formed, they undergo meiosis 1 and become secondary spermatocyes. At the end of meiosis 1 the 2 cells are diploid, meaning they possess 1 pair of homologous chromosomes (n=2), which is the normal amount in an adult cell. The secondary spermatocyes then undergo meiosis 2 leaving 4 cells, which are immature sperm cells called spermatids. How many chromosomes do the spermatids have?

Answer 87

- 1 copy of chromosomes in each cell - HAPLOID - 23 chromosomes, but not pairs

Question 88

What is Spermiogenesis?

Answer 88

- maturation of a spermatid into spermatozoon

Question 89

Spermiogenesis is the maturation of a spermatid into spermatozoon. There are 4 stages of this process. Using the labels below label them: Tail phase Maturation phase Cap phase Golgi phase

Answer 89

``` 1 = Golgi phase (Golgi apparatus form large vesicle) 2 = Cap phase (large vesicle placed on head of nucleus) 3 = Tail phase (opposite side to cap) 4 = Maturation phase ```

Question 90

What is Spermiation?

Answer 90

- mature spermatids are released from Sertoli cells into the seminiferous tubule lumen prior to their passage to the epididymis

Question 91

What is capacitation?

Answer 91

- sperm are altered in in the female reproductive tract | - enables increased speed and to penetrate and fertilise an egg