Lecture 8 - The Gonads 1 Flashcards

1
Q

How do the gonads develop in males and females?

A

Males - testes Females - ovaries

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2
Q

What differentiates the ovaries from testes in embryogenesis?

A

The SRY gene on Y chromosome makes gonad develop into testes

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3
Q

When does spermatogenesis begin?

A

In puberty

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4
Q

When does oogenesis begin?

A

Reach 6-7 million oogonia at 24 weeks and cells begin deteriorating (atresia) and when puberty is reached 400,000 and by the time menopause is reached, 300-400

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5
Q

What are the functions of the gonads?

A

Production of gametes - gametogenesis Steroidogenesis - Androgens (MALES, females) and Oestrogens/Progesterones (FEMALES males)

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6
Q

Describe the process of Spermatogenesis:

A

Germ cell (diploid) > spermatogonia (mitotic, ^ testosterone) > 1ry spermatocytes (1st meiotic) > 2ry spermatocytes (2nd meiotic/HAPLOID) > Spermatids > Spermatozoa

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7
Q

How long does spermatogenesis take?

A

Around 70 days

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8
Q

How do males retain some spermatogenic capability throughout life?

A

A pool of spermatogonia remain for subsequent cycles

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9
Q

At what rate is sperm produced?

A

300-600 sperm/gm in testis/second

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10
Q

Describe the process of oogenesis:

A

Germ cell (diploid) > Oogonia (mitotic) > 1ry oocyte (1st meiotic) > 2ry oocyte (HAPLOID, 2ry meiotic and takes both cytoplasms, so 1st polar body dies - occurs during ovulation) > Ovum (with 2nd polar body)

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11
Q

What happens to primordial follicles?

A

They are arrested in development and enter atresia - cell degradation then death

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12
Q

Key features of testes:

A

Coiled seminiferous tubules - spermatogenesis Rete testis, Vasa efferentia Epididymis - stores sperm and sperm gain motility Vas deferens - surrounded by smooth muscle, propels sperm to urethra and other secretions added

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13
Q

Key features of seminiferous tubules:

A

Leydig cells - close to ST Sertoli cells - Sperm develop in folds of sertoli cells, where they then move into tubule lumen - connected very tightly leading to blood-testes barrier

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14
Q

What are Sertoli cells?

A

Form seminiferous tubules Synthesise FSH and androgen receptors (ABG) In response to FSH - INHIBIN produced Associated with developing spermatocytes

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15
Q

What are Leydig cells?

A

Lie outside ST Synthesise LH receptors In response to LH are the main source of testicular androgens - testosterone (testosterone in testicles is 1000x higher than in blood)

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16
Q

Key features of ovaries:

A

GRAFFIAN FOLLICLE: Ovum, Follicular fluid, Granulosa cells, Thecal cells

Ovarian stroma

Follicles undergoing atresia

Remnants of last corpus luteum

17
Q

What is the precursor molecules to steroids?

A

Cholesterol

18
Q

How do we differentiate between which steroid produced?

A

Different enzymes present in each target tissue

19
Q

How is Dihydrotestosterone formed?

A

Chol > preg > prog > 17 OH prog > androstenedione > testosterone > DHT

20
Q

How is 17 beta oestradiol formed?

A

Chol > preg > prog > 17 OH prog > androstenedione > EITHER a) testosterone > oestrone > 17BO OR b) Oestrone > 17BO

21
Q

How long does the menstrual cycle last?

A

Between 20-35 days, usually 28

22
Q

When does MC begin?

A

On first day of menstruation

23
Q

What is menstruation?

A

Loss of blood and cellular debris from necrotic uterine epithelium

24
Q

When does ovulation occur?

A

Around day 14

25
Q

What does the menstrual cycle consist of?

A

Ovarian cycle and Endometrial cycle

26
Q

What is the process of the menstrual cycle?

A

Follicular phase (OC) > 17BO > Proliferative phase (EC) (thickening of endometrium) & Ovulation (OC) > Luteal phase (OC) > Prog (stimulates secreation of hormones) and 17BO > Secretory phase (EC)

27
Q

When does 17BO secretion begin?

A

When follicles increase in growth and when dominant follicle secretes ^ oestrogen levels - maintaining it for 36 hrs where -ve feedback turns to +ve feedback, surging LH and FSH causing ovulation

28
Q

What is the ovarian cycle?

A

Pre-antral follicle > Early antral follicle > late antral follicle > Graffian follicle > OVULATION + LUTEAL PHASE (release of ovum and corpus luteum)

29
Q

How is the ovum chosen?

A

They’re selected sporadically for development and the most highly developed can then survive on its own, so the others undergo atresia

30
Q

What hormones are produced during the ovarian cycle by the follicle?

A

The late antral follicle produces 17BO in granulosa cells from androgens (contain aromatase) FSH and LH are secreted to the follicle Thecal cells have LH receptors and synthesise androgens from LH, which then diffuse to granulosa cells

31
Q

What hormones are produced during ovarian cycle by the corpus luteum?

A

Androgens converted into 17BO and progesterone under LH and FSH influence

32
Q

What is the dominant hormone in the proliferative phase?

A

Oestrogen

33
Q

What happens to the endometrium during the early and late phase of the proliferative phase?

A

Early: thin Late: thickens - mitosis

34
Q

What happens to the glands during early and late phases of proliferative phase?

A

Early: Straight Late: Enlarge, coil, increased blood supply to endomentrium

35
Q

What happens to endometrium and glands during secretory phase?

A

Endom: becomes secretory Glands: secrete glycogen, mucopolysaccharides; mucosa engorged with blood

36
Q

What is the dominant hormone in the secretory phase?

A

Progesterone (small oestrogen influence)

37
Q

What days correspond to each part of the cycle?

A

1-5 = Menstruation 6-14 = Proliferative phase 14-15 = Ovulation 15-28 = Secretory phase