urogenital development SDL

Question 1

what is sex determination

Answer 1

• developmental decision that directs the “bipotential” gonad to develop as a testis or ovary
• in mammals it is genetically controlled by sex determining region Y gene on Y chromosome
• in some species it is an environmental process

Question 2

what is sexual differentiation

Answer 2

induced by products of the gonad and internal and external development of the genitalia

Question 3

which hormones are produced by the gonads

Answer 3

males: testosterone
females: oestrogen and progesterone

Question 4

what is the difference between genotype and phenotype

Answer 4

genotype: genetic composition of the organism
phenotype: observable characteristic encoded for in the genotype

Question 5

what are the phases of normal morphological sexual development

Answer 5

1. the pregonadal phase
2. the bipotential gonad (development of gonadal precursor tissue)
3. primary sexual differentiation of reproductive tissues
4. secondary sexual differentiation = development of secondary sexual characteristics

Question 6

where do the pregonadal phase germ cells start to migrate from

Answer 6

yolk sac

Question 7

what are the 3 levels of sexual dimorphism

Answer 7

• genetic (sex determination)
• gonadal (sexual differentiation)
• phenotypic (sexual differentiation)

Question 8

discuss the importance of SRY gene in sexual differentiation

Answer 8

Question 9

discuss sexual differentiation in the brain

Answer 9

Question 10

map out the migration route of germ cells

Answer 10

1. Epiblast: Origin of PGCs.
2. Yolk Sac: Initial migration and proliferation.
3. Hindgut: Migration through the wall of the developing gut.
4. Dorsal Mesentery: Pathway towards the genital ridges.
5. Genital Ridges: Arrival and integration into future gonads.
6. Gonads: Final differentiation into germ cells (eggs or sperm).

Question 11

how do male germ cells differentiate

Answer 11

XY germ cells undergo mitosis during migration. When they reach the gonad, their growth becomes arrested and they remain within the testis in the Go phase of the cell cycle until after birth. This is induced by a meiosis inhibitory factor which is secreted by either Sertoli or myoid cells. After birth the male germ cell resumes the cell cycle and undergoes meiotic division to form haploid spermatozoa. The Sertoli cells nurture the germ cells and spermatogenesis is complete at puberty under the influence of FSH and LH.

Question 12

how do female germ cells differ

Answer 12

XX germ cells undergo mitosis as they migrate to the female genital ridge and enter the ovary. The cells then undergo the initial stages of the first meiotic division becoming arrested at prophase 1 by birth. At this point they become surrounded by a single layer of granulosa cells to form primordial follicles. Although follicle development continues, the oocytes remain arrested until they are stimulated by FSH and LH at puberty

Question 13

what are sertoli cells

Answer 13

specialized cells found within the seminiferous tubules of the testes. They play a crucial role in supporting and nurturing the development of sperm cells (spermatogenesis), respond to FSH and secretion of inhibin

Question 14

what are leydig cells

Answer 14

Leydig cells are specialized cells located in the interstitial tissue of the testes, which is the connective tissue surrounding the seminiferous tubules where sperm are produced. These cells produce testosterone. regulated by LH

Question 15

what are thecal cells

Answer 15

• located in ovarian follicles
• produce androgens which are later converted into estradiol
• support oocyte maturation

Question 16

what are follicular cells

Answer 16

• line ovarian follicle
• support and nourish oocyte
• produce inhibin and estrogens
• interact with thecal cells
• respond to FSH and LH