Unit 5: A&P - The Reproductive System

When does the reproductive system become active?

At puberty

How are sperm and ova formed?

Meiosis

What 3 hormones are vital in maturations, development and function of reproductive organs, and sexual drives?

Testosterone, estrogens, and progesterone

What hormones stimulates FSH and LH?

GnRH (gonadotropin-releasing hormone) which starts process of gamete and sexual maturation

What is the perineum?

Diamond-shaped area between the thighs

What are the two regions of the perineum?

Urogenital triangle (anterior) and anal triangle (posterior)

What is gametogenesis?

Formation of gametes (sex cells)

Why is meiosis important?

Reduces chromosome number by half to maintain correct zygote number

Haploid (n)?

One set of chromosomes (23 in humans)

Diploid (2n)?

Two sets of chromosomes (46 in humans)

What are homologous chromosomes?

Pair of chromosomes (one from each parent) with same genes

What are sister chromatids?

Identical copies of a chromosome joined by a centromere

What is crossing over?

Exchange of DNA between homologous chromosomes during meiosis I

What happens in meiosis I?

Chromosome number reduces from 2n → n

What happens in prophase I?

Synapsis + crossing over

What happens in metaphase I?

Tetrads line up randomly

What happens in anaphase I?

Homologous chromosomes separate

End result of meiosis I?

2 haploid cells (chromosomes still duplicated)

What happens in meiosis II?

Sister chromatids separate

End result of meiosis II?

4 genetically different haploid cells

Mitosis produces how many cells?

2 identical diploid cells

Meiosis produces how many cells?

4 genetically different haploid cells

Function of ovaries?

Produce ova + estrogen/progesterone

What is ovulation?

Release of oocyte from follicle

Order of follicle development?

Primordial → Primary → Secondary → Antral → Mature → Corpus luteum → Corpus albicans

Primordial follicle?

Primary oocyte + single follicle cell layer

Arrested in first meiotic prophase

Antral follicle?

Fluid-filled antrum appears

Forms from primary follicle

Primary follicle?

Begins estrogen secretion + zona pellucida forms

Oocyte with granulosa cell

Secondary follicle?

Multiple layers + thecal cells present (controls follicle development)

Mature follicle?

Contains secondary oocyte (ready for ovulation)

Completed Meiosis I (arrested in second meiotic metaphase)

Define this:

Secretes progesterone + estrogen

Stimulates buildup of uterine lining and prepares uterus for implantation

Corpus luteum

Define this:

Formed from regressed corpus lutem

Corpus albicans

Define this:

Production of female gametes

Begins during fetal phase

No new oocytes are made

Oogenesis

What is pathway of oogenesis?

Oogonia → Primary oocytes → Secondary oocytes → Ovum

Define this:

Apoptosis (programmed cell death) of oocyte and surrounding cells
99.9% of all follicles are never recruited

Atresia

Define this:

Each month after puberty, a select few primary oocytes are activated

Caused by high hormonal levels (FSH)

Ovulation

What two stages are folliculogenesis divided into?

Preantral stage and antral stage

What is preantral stage regulated by?

Local molecular signals

What is antral stage regulated by?

FSH and LH

Define this ovarian cycle:

Days 1 - 14

Period of vesicular follicle growth

Primary oocyte of dominant follicle completes meiosis I to form secondary oocyte

Follicular phase

Define this ovarian cycle:

Period of corpus luteum activity (14 - 28)

Ruptured follicle collapses and antrum fill with clotted blood

If no pregnancy, then corpus lutem → corpus albicans happen

Shedding of uterine lining

Luteal Phase

When does ovulation occur?

14 of 28 day cycle

14 days before first day of menstruation

Define this phase of ovarian cycle:

Ovary wall ruptures

Induced with peak in LH secretion

14 days before first day of menstruation

Ovulation

Define this:

time near menopause

Irregular or skipped periods

Perimenopause

Define this:

Women cease cycling for 1 year

Onset at 45 - 55

No more ovarian follicles remain

No longer uterine lining no longer growing

Menopause

What does GnRH stimulate?

FSH and LH release from anterior pituitary

Define this hormone:

Stimulates follicle growth and estrogen production

FSH

Define this hormone:

Triggers ovulation + corpus luteum formation

LH

What type of feedback do estrogens usually provide?

Negative feedback (inhibit FSH and LH)

What triggers LH surge?

Positive feedback from high estrogen levels

Why does only one follicle survive?

It is dominant and can withstand low FSH levels

What is the LH surge responsible for?

Ovulation + corpus luteum formation

What hormone is produced after fertilization?

hCG (human chorionic gonadotropin)

What does hCG do?

Maintains corpus luteum

What replaces corpus luteum long-term in pregnancy?

Placenta

Where does fertilization usually occur?

Ampulla of uterine tube

Define this:

Sweep oocyte into uterine tube

Fimbriae

How does oocyte move through tube?

Ciliary action + peristalsis

Order of uterine tube regions?

Infundibulum → Ampulla → Isthmus

Main function of uterus?

Receive, nourish, and retain embryo

Regions of uterus?

Fundus, body, isthmus, cervix

Layers of uterine wall (outer → inner)?

Perimetrium → Myometrium → Endometrium

Function of myometrium?

Smooth muscle contractions (labor)

Function of endometrium?

Implantation + menstrual shedding

What supports the uterus laterally?

Cardinal ligaments

What anchors uterus to sacrum?

Uterosacral ligaments

What attaches uterus to anterior wall?

Round ligaments

Functions of vagina?

Birth canal, copulation, menstrual flow passage

Type of epithelium in vagina?

Stratified squamous epithelium

Why is vaginal environment acidic in adults?

Hormonal changes + microbial environment protection

Name the hormone cycle including phases and hormones:

GnRH → FSH/LH → follicle growth → estrogen → LH surge → ovulation → corpus luteum → progesterone/estrogen → degeneration (if no pregnancy)

Define this menstrual cycle:

Ovarian hormones are at lowest levels

Stratum functionalis detaches from uterine wall and is shed - menstrual flow of blood
and tissue ~ 3–5 days
By day 5, growing ovarian follicles start to produce more estrogen

Menstrual Phase (1-5)

Define this menstrual cycle:

Rising estrogen levels prompt generation of new stratum functionalis layer

Estrogen also increases synthesis of progesterone receptors in endometrium

Proliferative phase (1-14)

Define this menstrual cycle:

Consistent in duration (always 14 days)

Endometrium prepares for embryo to implant

No Fertilization:

Corpus luteum degenerates toward end of secretory phase; progesterone levels
fall

Secretory (postovulatory) phase (15 - 28)

Which of these is not an affect of the rising progesterone levels from corpus luteum?

Triggers the LH surge

Which of these is not an effect of estrogen?

Maintains the uterine lining after ovulation

Which of these is not an effect of progesterone?

Builds up the uterine lining during the proliferative phase

What is the vulva?

External female genitalia

Function of labia majora?

Protect external genital structures

Function of labia minora?

Surround vestibule and protect openings

What is the clitoris homologous to?

Penis

What is the function of vestibular glands?

Lubrication of vaginal opening

Function of mammary glands?

Milk production

What produces milk?

Prolactin (anterior pituitary)

What causes milk ejection?

Oxytocin (posterior pituitary)

What is lactation?

Production and release of breast milk

What happens during excitement phase?

Vasocongestion + lubrication + nipple erection

What is unique about female orgasm?

No refractory period → multiple orgasms possible

(True/False) Orgasm is required for conception.

False

Function of scrotum?

Maintains testes ~3°C below body temp for sperm production

Dartos muscle function?

Wrinkles scrotal skin for temperature control

Cremaster muscle function?

Raises/lowers testes for temperature regulation

Order of sperm pathway?

Seminiferous tubules → straight tubule → rete testis → efferent ductules → epididymis

Where is sperm produced?

Seminiferous tubules

What do sustentacular (Sertoli) cells do?

Support sperm, form blood-testis barrier, release inhibin

What is the blood-testis barrier for?

Protects sperm from immune system

What starts male hormone control?

GnRH from hypothalamus

What does LH do in males?

Stimulates Leydig cells → testosterone production

What does FSH do in males?

Stimulates spermatogenesis via Sertoli cells

What does inhibin do?

Inhibits FSH (negative feedback)