- some of largest cells in body - nonmotile, move via smooth muscle contraction or cilia

- quite small - only flagellated cells in body - highly motile - continuously produces after reaching reproductive maturity - sperm and testosterone production dismisses with age but not cease

Repro 2 Flashcards by Kiera Joy

Bipotential parts of external genitalia

Genital tubercle, urethral groove, urethral fold, labioscrotal swelling

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If female genital tubercle

Forms clitoris

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If female urethral folds and grooves

Form labia minora, opening of vagina and urethra

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If female labioscrotal swellings

Form labia Majora

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If male genital tubercle

Forms glans penis

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If male urethral folds and grooves

Form shaft of penis

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If male labioscrotal swellings

Form shaft of penis and scrotum

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External genitalia development is driven by

Presence or absence of androgens (DHT)

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At 10 weeks of female growth (external)

In absence of androgens external genitalia is feminized

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At 10 weeks of male growth (external)

DHT causes development of male external genitalia

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At birth males (external)

Testosterone causes Testes to descend from abdominal cavity into scrotum

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When did importance of DHT come to light

Studies of male pseudohermaphrodites

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What do pseudohermaphrotdites lack

Have defective gene for 5a reductase
Needed for conversion of testosterone to DHT

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What does no DHT cause for pseudohermaphrodites

Despite having testosterone
- failure of male external genitalia and prostate development
- appear female at birth, male internal
- at puberty testes begin to secrete testosterone causing masculinzatin of external genitalia

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Testis and ovaries both produce

Hormones and gametes

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Ovum

some of largest cells in body
nonmotile, move via smooth muscle contraction or cilia

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What are all females born with

All oocytes, cyclically released during reproductive years
After ~40 years in ceases

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Sperm

quite small
only flagellated cells in body
highly motile
continuously produces after reaching reproductive maturity
sperm and testosterone production dismisses with age but not cease

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Gametogenesis

Production of gametes

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What does gametogenesis begin with

Mitosis in utero to increase germ cell numbers

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Female germ cells

Oogonia

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Male germ cells

Spermatogonia

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How many viable gametes does 1 sperm cell produce

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How many viable gametes does 1 female germ cell produce

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Steps of gametogenesis

1. Germ cells in embryonic gonads undergo mitosis divisions to increase number 2. Meiosis: Duplication of chromosomes (92 chromatids) 3. One primary gamete divides into 2 secondary gametes (each with 46 chromosomes) 4. Secondary gametes divide again to produce haploid gametes (23 chromatids)

Female gametogenesis

- significant mitosis in embryonic and fetal development (lots of oogonia) - enter meiosis and create large pool of primary oocytes - stay arrested until reproductive age

At birth ~ how many primary oocytes in each ovary

5000

When does second meiotic division occur for females

Ovary releases egg and it does not until Fertilization

When does mitosis and first stage of meiosis occur by in females

Fifth month of fetal development

When does meiosis resume in females

Puberty

First meiotic division in females

Produces large secondary oocyte and tiny first polar body (46 chromosomes)

What happens when egg begins second meiotic division

Polar bodies break down

How many chromosomes does secondary oocyte contain

Once sperm begins to fertilize secondary oocyte what does it undergo

Meiotic division shedding a polar body containing 23 chromosomes Leaves 23 in ovum and 23 new chromosomes enter sperm

Why dont polar bodies survive

Uneven division Very small with very little cytoplasm and few organelles

In both males and females gametogenesis is under control of

Hormones from brain and from endocrine cells in gonads

When does significant mitosis happen for males

Once reach reproductive age

At birth what do testes contain

Only immature germ cells and remain quiescent

At puberty what happens to germ cells in males

Mitosis resumes producing spermatogonia

What happens to spermatogonia if they do not continue in mitosis

Some enter meiosis producing primary spermatocytes, secondary spermatocytes, spermatid then sperm

What directs resproduction

Brain

For both male and female what doses reproduction begin with

Secretion of peptide hormones from hypothalamus and anterior pituitary that control gonadal secretion of sex hormones - androgens, estrogens, progrestorone

What sex hormones do both sexes produce

Androgens, estrogens, progesterone

Males primarily secrete

Androgens 95% testes, 5% adrenal cortex Most converted in periphery to DHT

Females primarily secrete

Estrogens and progesterone (ovaries)

What is the sex hormone precursor

Cholesterol

What is the main control pathway for the reproductive system

Hypothalamic pituitary gonadal axis

Gonatropin releasing hormone (GnRH)

Produces in hypothalamic neurons Controls secretion of 2 anterior pituitary gonadotropins from gonadotropes

What are the 2 ant. Pit. Gonadotropins

Follicle stimulating hormone (FSH) Luteinizing hormone (LH) Act on gonads

What regulates GnRH

Kisspeptin

What does LH act on

Endocrine cells In females gamete production

What does FSH act on

Gamete production

How does GnRH get to anterior pituitary

Hypophyseal portal system

How does hypophyseal portal system work

GnRH secreted enters capillary bed at base of hypothalamus Travels through portal veins to 2nd capillary bed in ant. Pit. GnRH stimulates gonadotropes LH and FSH enter 2nd capillary bed and travail via blood stream to gonads

What is short loop negative feedback

Involves LH and FSH inhibiting GnRH release from hypothalamus

Low estrogen or androgen(testosterone)

Absence of negative feedback Increases in GnRH, LH and FSH

Moderate estrogen or androgen

Negative feedback Decreases GnRH

High androgen

Negative feedback Decreases

Sustained high estrogen

Positive feedback Increases to drive LH

Why is estrogen negative feedback to a point

Flips to positive driving GnRH and LH even higher Plays role in female reproductive cycle

What does feedback at anterior pituitary affect

Gonadotropes

What does feedback at hypothalamus act on

Directly on GnRH neurons or via kisspeptin

How is GnRH released from hypothalamus

In pulsatile fashion every 1-3 hours in both sexes

Females have a surge of GnRH release

Corresponding with ovulation

Children with GnRH deficiency

Not mature sexually without gonadotropin stimulation Synthetic GnRH must be delivered in pulsatile manner

What does constant delivery of GnRH lead to

Down regulation of receptors in pituitary gonadotropes - receptors internalize - must be pulsatile