Costanzo Ch. 10 Flashcards Preview

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Flashcards in Costanzo Ch. 10 Deck (60):
1

How long during gestation are the gonads indifferent?

the first 5 weeks

2

When do the testes begin to develop? the ovaries?

The testes begin to develop at gestational weeks 6-7 while the ovaries begin to develop at week 9

3

What are the cell types of the male gonads?

germ cells, Sertoli cells, and Leydig cells 

4

What are the cell types of the ovaries?

the germ cells (produce oogonia), granulosa cells, and theca cells

5

What structure gives rise to the epididymis, vas deferens, seminal vesicles, and ejaculatory ducts?

Wolffian ducts

6

What stimulates the growth and differentiation of the wolffian ducts?

testosterone. This testosterone from rach testis acts ipsilaterally (same side) on its own wolffian duct

7

T or F. Testosterone has to be converted to DHT to act on the wolffian ducts

F.

8

What causes atrophy of the mullerian ducts?

AMH from the Sertoli cells (this mullerian ducts would have become the female genital tract if they had not been suppressed by AMH)

9

When do the external male genitalia, the penis and scrotum, differentiate during gestation?

weeks 9-10

10

Growth and development of the external male gentialia depend on what?

covnersion of testosterone to DHT 

11

Why do the mullerian ducts develop into the interal female tract (fallopain tubes, uterus, and the upper one third of the vagina) in women?

Because women lack AMH so the mullerian ducts develop by default

12

What happens if a gonadal female is exposed to high levels of androgens in utero (e.g. from excessive production by the adrenal cortex) when the external genitalia are differenitating?

a male phenotype will develop. If such exposure occurs AFTER differentiation of the external genitalia, the female phenotype is retained, but possibly with enlargement of the clitoris

13

In both males and females, gonadal function is driven by what?

the hypothalamic-pituitary axis

14

When does secretion of GnRH begin during gestation?

gestational week 4, but its levels remain low until puberty

15

When does secretion of LH and FSH begin during gestation?

between gestational weeks 10-12 (these too remain low until puberty)

16

T or F. During childhood, FSH levels are relatively higher than LH levels

T.

17

Q image thumb

18

What happens to the secretion of GnRH, FSH, and LH after puberty?

it increases and becomes pulsatile, with the relative rates of LH becoming higher than FSH levels and the establishment of a 28-day cycle of gonadotropin secretion called the menstrual cycle

19

What happens to levels of GnRH, FSH, and LH in senescence?

gonadotropin levels increase further, with FSH levels becoming higher tahn LH levels again 

20

What is one of the earliest events of puberty?

the appearance of large nocturnal pulses of LH during REM sleep and an increased sensitivity of the GnRH receptor in the anterior pituitary (thus, at puberty GnRH up-regulates its own receptor in the anterior pituitary and a given conc of GnRH produces a greater stimulation of FSH and LH secretion).

21

Pulsatile secretion of FSH and LH at puberty then stimulate what?

secretion of the gonadal steroid hormones, testosterone and estradiol, which then drive appearance of the secondary sex characteristics

22

T or F. The onset of maturational processes in men and women are genetic and programmed

T. For example, the age at menarche is similar between mothers and daughters (however, the mechanisms underlying the onset of pulsatile GnRH secretion remains a mystery)

23

What are the suggested thoughts on what causes the pulsatile increase of GnRH at puberty?

-Melatonin could inhibit GnRH (melatonin is high during childhood and decreases during adolescence, and removal of the pineal gland has been shown to precipitate early puberty)

24

Is the pulsatile nature of GnRH required to produce puberty and secondary growth or can the same effects be seen if you just give a long acting GnRH analogue?

It's required! Puberty will NOT be initiated using a long-acting GnRH analogue in a GnRH deficient person

25

What causes growth of the testes during puberty?

largely increases in the number of seminiferous tubules

26

What else occurs during male puberty?

-increased growth of sex accessory organs such as the prostate

-linear growth spurt and closure of the epiphyses

-appearance of facial, pubic, and axillary hair as testosterone increases

-growth of the penis

-initiation of spermatogenesis

27

What changes occur in pregnancy in females?

-first sign is budding of the breasts, which is following in approx. 2 yrs by menarche

-growth spurts and epiphysis closure occuring faster and earlier than in boys

28

The appearance of pubic and axillary hair precedes menarche in girls and is dependent on increased secretion of _____

adrenal androgens (called adrenarche)

29

Describe the temperature of the testes

They are maintained at 1-2C below body temp. which is essential for normal spermatogenesis and is maintained by a countercurrent arrangement of testicular arteries and veins, which facilitate heat exchange

30

80% of the adult testis is composed of what?

seminiferious tubules, oriented in lobules, which produce sperm 

the remaining 20% is composed of CT interspersed with Leydig cells

31

The epithelium lining the seminiferous tubules consists of what three cell types?

spermatogonia, the stem cells

spermatocytes, which are cells in the process of becoming sperm

Sertoli cells, which support developing sperm

32

What are the roles of Sertoli cells?

-providing nutrients to the differentiating sperm (which are isolated from the bloodstream)

-forming tight junctions with each other, creating the blood-testes barrier (which still allows testosterone to pass)

-secreting an aqueous fluid into the lumen of the seminiferous tubules, which helps to transport sperm through the tubules into the epididymis

secrete AMH

33

What are the roles of Leydig cells?

-synthesis and secretion of testosterone, which has both local (paracrine) effects that support spermatogenesis in the testicular Sertoli cells and endocrine effects on skeletal muscle and the prostate

34

T or F. Spermatogeneis occurs continuously throughout the reproductive life of the male, from puberty to senescence

T. Occurring along the length of the seminiferous tubules

35

Describe spermatogenesis

1) Mitotic divisions of spermatogonia to produce spermatocytes

2) Meiotic divisions to produce haploid spermatids

3) Spermiogenesis, in which spermatides lose cytoplasma and develop flagella to transform into mature sperm

36

What occurs in the epididymis?

This is the primary location for the maturation and storage of sperm once it leaves the seminiferous ducts. They remain viable in the epididymis for several months

37

What causes movement of sperm through the epididymis?

During sexual arousal, contractions of the smooth muscle around the ducts advance sperm and at ejaculation, sperm are excelled into the vas deferens and then into the urethra

38

What do the seminal vesicles secrete?

a fluid rich in fructose, citrate, prostaglandins, and fibrinogen. As the vas deferens empties its sperm into the ejaculatory duct, each seminal vesicle contributes its secretions, which also will be nutritive for the ejaculated sperm 

39

What do the prostaglandins in sperm aid in?

1) They react with cervical mucus to make it more pentrable by sperm

2) Prostaglandins induce perstaltic contractions in the female tract to propel sperm forward

40

What does the prostate gland add to sperm?

a milky, slightly alkaline aqeuous solution rich in citrate, calcium, and enzymes

41

What is the advantage of the alkaline fluid from the prostate gland in sperm?

it increases sperm motility and aids in fertilization by neutralizing acidic secretions from the vas deferens and the vagina

42

Collectively, the combined secretions of the male sex accessory glands compose 90% of the volume of semen, and sperm compose the remaining 10%

43

T or F. Ejaculated sperm can immediately fertilize an ovum

F. It must reside in the female reproductive tract for 4-6 hrs for capacitation to occur

44

What is capacitation?

Capacitation is a process in which inhibitory factors in the seminal fluid are washed free, cholesterol is withdrawm from the sperm membrane, and surface proteins are redistributed. Calcium influx into the sperm increases their motility, and the motion of the sperm becomes whiplike.It also results in the acrosomal rxn in which the acrosomal membrane fuses with the outer sperm membrane, creating pores through which hydrolytic and proteolytic enzymes can escape from the acrosome, creating a path for sperm to penetrate the ovum

45

Where is testosterone made?

Leydig cells

A image thumb
46

Note that testosterone is the main hormonal product of the testes, but testosterone is not active in all adrogenic target tissues. How is T converted to DHT?

5a-reductase

47

Where is GnRH made?

neurons in the arcuate nuclei

48

Describe the secretion patterns of GnRH, FSH, and LH

They are all pulsatile. (Note that if GnRH is administered continuously, it inhibits FSH and LH secretion)

49

What does FSH stimulate in males?

spermatogenesis and Sertoli cell function

50

What does LH stimulate in males?

Stimulates Leydig cells to synthesize testosterone by increasing cholesterol desmolase

51

How does testosterone act in the testes (paracrine)?

It diffuses from the Leydig cells to the nearby Sertoli cells, where it reinforces the spermatogenic action of FSH

52

Describe the feedback of testosterone

Testosterone inhibits both GnRH and LH and Sertoli cells secrete inhibin, a glycoprotein which inhibits FSH production when sperm production is adequate

53

What would happen to GnRH, FSH, and LH pulses if the testes were removed?

No testosterone leads to increased pulses 

54

DHT is involved in what processes?

-differentiation of external male genitalia (penis, scrotum)

-stimulation of hair follicles, male pattern baldness

-sebaceous gland activity

-prostate growth

55

What processes are mediated by testosterone?

-differentiation of internal male genital tract (epididymis, vas deferens, etc.)

-development of muscle mass

-pubertal growth spurt and epiphyseal closure

-penis growth and seminal vesicles

-deepening of the voice

-libido

-spermatogenesis

56

What determines if a person has testes?

Y chromosome (SRY region)

57

What hormones do the testes secrete?

AMH and testosterone

58

What does AMH do?

suppresses development of the mullerian ducts into the interal female genital tract, so no fallopian tubes, uterus, or upper third of the vagina will develop

59

What does testosterone cause in the developing fetus?

differentiation of the wolffian ducts into the internal male genital tract (epididymis, vas deferens, and seminal vesicles). Thus, this will occur even in a 5a-reductase deficiency

60