The Reproductive Systems

Reproductive organs are grouped by function

Gonads - testes and ovaries

produce gametes and secrete hormones

produce gametes and fluid; then discharge into duct system indicates exocrine function

production of hormones indicates endocrine function

Ducts receive, store, transport gametes

Accessory sex glands support gametes

Supporting structures - various reproductive functions

Males

Male Reproductive System

Testes, a system of ducts, accessory sex glands, and several supporting structures (including the

penis)

Scrotum

2 fibrous sacs which support and protect the testes

Muscle

cremaster muscle

dartos muscle

Location and temperature due to muscle contraction

sperm production requires temp 3 C below body temp

involuntary muscle contraction raises the testes

Testes - testicles

paired oval glands 5 cm x 2.5 cm

development influenced by Y sex chromosome and by maternal hormonal levels

develop in abdomen

begin descent during the 7th month of development

Surrounded by dense connective tissue

covered by tunica vaginalis (serous membrane) from peritoneum

internal fibrous capsule = tunica albuginea

also forms septa creating lobules

200-300 lobules/testicle

3 seminiferous tubules in each lobule (typical)

Each seminiferous tubule is lined with spermatogenic cells in various developmental stages

Blood-Testis Barrier prevents immune system response to sperm antigens

Sustentacular (Sertoli) cells

create blood-testis barrier with tight junctions

respond to FSH and testosterone

phagocytize shed excess spermatid cytoplasm

control sperm movement and release into the tubule lumen

secrete some nutrients for sperm

secrete some fluid for sperm transport

Male Reproductive System

Interstitial endocrinocytes (interstitial cells of Leydig)

located between tubules

secrete testosterone in response to LH (= ICTH)

Spermatogonia undergo meiosis to give rise to spermatazoa

Spermatogenesis

meiosis occurs in the seminiferous tubules

produces haploid spermatozoa

64-72 days in humans

Spermatogonia

Diploid stem cells

by mitosis, some remain as viable stem cells through out life

others undergo developmental changes to become primary spermatocytes and undergo

meiosis

Reduction division

primary spermatocytes undergo meiosis I to become secondary spermatocytes (haploid)

secondary spermatocytes undergo meiosis II to become immature spermatids (haploid)

Spermatids mature morphologically into spermatozoa = sperm cells

spermatid do not separate their cytoplasm completely

they maintain cytoplasmic bridges until released into the tubule lumen

Spermatogenesis

spermatids mature physiologically into spermatozoa

Requires 10-14 days for migration to and 3-4 days for maturation in the ductus

epididymus

Older sperms are removed gradually by phagocytes within the epididymus

Many sperms are abnormal, either morpholically, physiologically, or genetically

30% abnormal is considered normal

Spermatozoa

300 million/day mature

survive about 48 hrs following ejaculation in the female reproductive tract

structure

head

nuclear material

acrosome - enzymes for penetration into egg

midpiece - site of ATP production to power tail

tail - flagellum

Hormones of brain-testicular axis

anterior pituitary drives changes during puberty

controlled by GnRH from hypothalamus

begins to secrete FSH, LH

LH targets Interstitial endocrinocytes

testosterone

dihydrotestosterone (DHT)

FSH - Sustentacular cells

Androgen-Binding Protein (ABP) concentrates androgens for spermatids

Inhibin negative feedback to the pituitary and hypothalamus

Development

testosterone stimulates pattern development before birth (internal ducts)

DHT external genitals

estrogens from testes brain development

Puberty testosterone & DHT stimulate enlargement of male sex organs and secondary sexual

characteristics

Testosterone -

secondary sex characteristics:

muscular, skeletal growth

heavier, thicker muscles and bones in men than in women

also triggers epiphyseal closure

pubic, axillary, facial and chest hair

oil gland secretion

larynx enlargement deepening the voice

sexual functions

male sexual behavior and aggressive behaviors

spermatogenesis

sex drive in both male and female

metabolism - stimulates protein synthesis

anabolic steroids are often misused and abused

Ducts

sperm move slowly from the lumen of seminiferous tubules straight tubules rete

testis epididymis

continuous sperm and testicular fluid production move sperms along

fluid contains: H2O, androgens, estrogens, K+, glutamic acid, aspartic acid

Epididymis

posterior border of testes

tightly coiled tube - head, body, tail

6 m long if uncoiled

pseudostratified columnar epithelium

microvilli provide nutrients

reabsorb testicular fluid

phagocytize degenerating older sperm

ductus epididymis

site of sperm maturation (10-14 days) - motility

may remain in storage for a month, then reabsorbed

Ductus (vas) deferens

less convoluted with a larger diameter

ascends, enters pelvic cavity through inguinal canal

loops up, over urinary bladder to end in the ampulla

Ductus (vas) deferens

pseudostratified columnar epithelium with thick muscularis

transports sperm from epididymis to urethra by peristalsis during ejaculation

Spermatic cord: testicular artery, veins, lymphatic vessels, autonomic nerves, vas deferens,

cremaster muscle descend with the testes

Exit the abdominal cavity through the inguinal canal

Vasectomy a portion of each duct is removed

Urethra

terminal tract for urinary and reproductive systems

3 regions:

prostatic urethra

membranous urethra

spongy (cavernous) urethra

Ends at external urethral orifice at the bulb/glans of the penis

Semen - mixture of sperms and secretions

Average volume = 2.5 5.0 mL

50-150 million sperm/mL

below 20 million/mL infertility

Large numbers needed for successful fertilization

Slightly alkaline (pH 7.2-7.6), milky and mucoid

decreases acidity of vagina

fructose is the nutrient for sperm metabolism

prostaglandins decrease mucous viscosity and stimulate reverse peristalsis

Contains natural antibiotic = seminalplasmin

Coagulates after ejaculation into vagina

somewhat different mechanism than blood clotting

breaks down in 5-20 minutes

Penis

root (attachment)

body (shaft)

glans penis (head)

Female Reproductive System

Ovaries, uterine (Fallopian) tubes, uterus, vagina, vulva, mammary glands

Ovaries

Paired, small (pecan-sized) oval organs in the pelvic cavity

Supported by several complex fibrous ligaments

Homologous in embryological development to the testes

Ovary Histology

Germinal epithelium

Tunica albuginea - connective tissue

Ovarian follicles

Stroma fibrous connective tissue

cortex - outer dense layer with ovarian follicles containing eggs = oocytes

medulla - inner loose fibrous connective tissue layer containing blood vessels

Ovary Histology

Germinal epithelium

Primordial follicles

Ovarian follicles

Primary follicles

Secondary follicles with antrum formation

Vesicular (Graafian) follicles with large antrums

After Ovulation:

Corpus luteum (yellow body)

Corpus albicans (white body)

Oogenesis

Formation of haploid ova in the ovary

Steps

Reduction division - meiosis I (haploid)

Equatorial division - meiosis II

Maturation potential for fertilization

Uterine (Fallopian) tubes = oviducts

Extend laterally from uterus to transport ova by peristalsis and cilia-generated current

from the ovaries to the uterus

Structure

(1) infundibulum with fimbriae

(2) ampulla

(3) isthmus

Uterine tube histology - 3 cell layers

internal mucosa - ciliated columnar epithelial cells and secretory cells

middle muscularis

inner thick circular layer of smooth muscle

outer thin longitudinal layer of smooth muscle

peristaltic contractions and cilia-generated current move secondary oocyte

toward uterus

outer serous membrane - perimetrium

Once a month an ovarian follicle ruptures releasing a secondary oocyte (ovulation)

Oocyte drawn into the oviduct by cilia-generated current on the fimbriae and within the

tube by cilia and peristalsis

Fertilization can occur at any time (ideally in 24 hours)

ideally in the ampulla upper third of oviduct

becomes a zygote and then begins mitotic divisions

Unfertilized oocytes disintegrate and are swept out

zygote morula blastocyst with trophoblast membrane implantation

more details on the stages of embryonic development in the next chapter

Uterus

Site of menstruation, implantation, fetal development, labor

Between the urinary bladder and the rectum

Size and shape of an inverted pear

3 parts of Uterus

1) Fundus 2) Body with 3) Isthmus

Female Reproductive System

3 parts of Uterus (cont.)

3) Cervix

narrow portion that opens into vagina

produces cervical mucus; (20-60 mL/day)

more receptive to spermatazoa at or near ovulation

otherwise the mucus plug keeps microbes out

cervix, mucus

protect spermatazoa

provide nutrients

role in capacitation

Uterus bends between its body and cervix

Uterus joins with the vagina at a right angle

Ligaments provide stability important especially during labor

3) broad ligaments

4) uterosacral ligaments

5) cardinal ligaments

6) round ligaments

3 layers

3) Endometrium

stroma (lamina propria) of glandular and connective tissues

divided into 2 layers:

stratum functionalis (functional layer) - shed during menstruation

stratum basalis (basal layer) - gives rise to stratum functionalis

Blood supply from uterine arteries

3) arcuate arteries - circular around the myometrium

4) radial arteries penetrate into the myometrium with smaller branches:

Fetal expulsion = labor and delivery

Oxytocin and prostaglandins regulate labor

ANS controls contractions

Vagina

3) Tubular, fibromuscular organ with mucous membrane

4) Between bladder, rectum

superiorly attached to uterus

recess (fornix) forms around the attachment to the cervix

Vagina histology

3) Mucosa continuous with the uterus

non-keratinized stratified squamous epithelium and connective tissue in folds

(rugae)

mucosal cells have large stores of glycogen

upon decomposition produce organic acids lowers pH

dendritic (APC) cells (source for HIV attachment -- AIDS?)

4) Muscularis

smooth muscle - outer circular, inner longitudinal layers

stretches to receive penis and for accommodating childbirth

5) Adventitia - areolar connective tissue

Vaginal orifice - hymen thin membrane

Mons pubis - anterior, adipose tissue

Labia majora

3) lateral skin folds with sebaceous and sudoriferous glands

4) homologous to scrotum

Labia minora - medial folds with sebaceous glands

Clitoris

3) Anterior junction of labia majora

4) Small cylindrical mass of erectile tissue and nerves

5) Plays a role in sexual excitement

6) Homologous to penis; has prepuce and glans

Vestibule

3) Region between labia minora

4) Mostly the vaginal orifice

External urethral orifice

3) Anterior to vaginal orifice, posterior to clitoris

4) Exterior opening of the urinary tract

5) Proximity to vagina and anus increase risk of UTI

Accessory glands

3) Paraurethral (Skene's) glands

On either side of external urethral orifice in the vulva

Secrete mucus

Homologous to prostate gland

4) Greater vestibular (Bartholin's) glands

Open in the area between hymen and labia minora

Mucus secretion during sexual intercourse

Some lesser vestibular mucous glands also present

Homologous to bulbourethral (Cowper's) gland

General Reproductive System

Perineum

3) Diamond shaped area between thighs, buttocks

4) Contains external genitals, anus

anterior - pubic symphysis

posterior - coccyx

Mammary Glands

3) Modified sudoriferous (sweat) glands that produce milk

4) Anatomy

over pectoralis major and serratus anterior muscles

attached to the deep fascia

surrounded by adipose and fibrous tissue

suspensory ligament of breast

runs between skin and deep fascia

supports breast

Mammary Glands

3) Nipple

exterior pigmented projection

many closely spaced openings - lactiferous ducts

4) Areola

surrounding pigmented area

sebaceous (oil) glands

Mammary Glands

3) 15 - 20 lobes internally separated by adipose tissue (which determines breast size and

shape)

4) separated into lobules with milk-secreting glands = alveoli

milk (when being produced) passes from alveoli secondary ducts

mammary ducts

approaching the nipple, the mammary ducts expand to form lactiferous sinuses

(for storage)

sinuses continue to nipple

Mammary Gland Development

3) Develop at puberty due to estrogen, progesterone

4) Ducts develop, fat deposition occurs

5) Areola and nipple enlarge; become pigmented

6) Further development occurs following ovulation and corpus luteum formation in

menstrual cycle or pregnancy

Mammary Gland Physiology

3) Primary function is milk synthesis

4) Secretion and ejection together = lactation

5) Primary stimulus for milk production is prolactin from the anterior pituitary

6) Stimuli for milk release (letdown) in response to suckling:

oxytocin from posterior pituitary

ANS reflexes

Breast Cancer

3) 12% of women will have breast cancer

4) 3.5% will die of breast cancer

5) Early detection is the most important aspect

6) Each month after a menstrual period, the breasts should be examined for lumps,

puckering of skin or nipple retraction or discharge

7) Genes BRCA1 and BRCA2 linked to the 10% of hereditary breast cancers

8) BR-1 is a new marker (2003), esp. for black women

9) But >70% of breast cancers are not associated with known risks

Breast Cancer

3) Risk factors

family history

early onset menses and late menopause

no child or first child after age 34

previous breast cancer

exposure to ionizing radiation (x-rays)

obesity, alcohol intake, cigarette smoking

4) Detection - mammogram, flattening is the key to a sharp image

5) Treatment

lumpectomy (removal of tumor and surrounding tissue)

radical mastectomy (breast, pectoral muscles, axillary lymph nodes)

Two parts in two different areas

3) Ovarian cycle - events in ovary leading to ovulation

4) Menstrual (uterine) cycle - endometrial changes

Controlled by varying levels of several hormones from several glands

3) Anterior Pituitary

4) Ovarian follicles

5) Corpus luteum

Hormones target several organs

3) Ovaries Uterus Breasts CNS

Female Reproductive Cycle - Hormones

Female Reproductive Cycle

Menstrual Phase

3) 50-150 ml of discharge: tissue fluid, mucus, epithelial cells and a small quantity of blood

from the endometrium

4) levels of estrogen/progesterone - negative feedback

uterine spiral arteries constrict creates ischemic tissue

entire stratum functionalis sloughs off

5) Ovaries

FSH levels rise (from day 25 of cycle) to stimulate a few primordial follicles to

develop into primary follicles

All follicles release low levels of estrogen

By day four, ~20 develop into primary and then secondary (growing) follicles

granulosa cells surround oocyte

zona pellucida forms between oocyte and the granulosa (follicular cells)

cells secretes watery follicular fluid into antrum

fluid forces oocyte to the follicles edge and fills follicular cavity

Preovulatory Phase - lasts 6-13 days

3) Menstrual and Preovulatory phase together are known as the Follicular phase

4) By day 6 of the cycle, one follicle outgrows others

dominant follicle secretes & inhibin

estrogen & inhibin reduce FSH secretion -

all other follicles stop growing and degenerate = atresia

estrogen levels increase due to this single follicle

5) Dominant follicle matures

vesicular ovarian (Graafian) follicle (mature follicle)

forms a blister-like bulge on the surface of the ovary

Preovulatory Phase

3) Follicle continues to secrete estrogen

FSH is dominant early

Close to ovulation, LH becomes important

4) Estrogen stimulates endometrial regrowth

stratum basalis

mitosis creates a new stratum functionalis

endometrial glands redevelop

arterioles coil and lengthen

Ovulation

3) LH pulse causes rupture of vesicular = Graafian follicle and release of oocyte into the

pelvic cavity; occurs approximately day 14

4) Secondary oocyte

surrounded by follicular cells, corona radiata

secondary oocyte in metaphase II

5) Fimbriae become more active; cilia create currents in peritoneal fluid to carry oocyte

into uterine tube

6) Estrogen causes changes in body temperature and cervical mucus becomes less

gelatinous

Ovulation

3) Prior to ovulation

high estrogen exerts positive feedback on FSH, LH

sudden surge of LH causes release of oocyte

LH surge is measurable

4) Following ovulation

follicle collapses becoming corpus hemorrhagicum

follicular cells then enlarge, change character, form the corpus luteum

follicular cells respond to LH by secreting estrogen and now progesterone

Postovulatory Phase

3) Most constant in duration, lasts for 14 days, from ovulation to the next menses

4) LH stimulates corpus luteum development (luteal phase); corpus luteum secretes

increased levels of estrogen and progesterone

5) Progesterone prepares endometrium to receive an embryo (if it has developed

sufficiently)

growth and coiling of endometrial glands

vascularization of surface endometrium

endometrial thickening

increased tissue fluid

secretory phase for the endometrial glands

Postovulatory Phase

3) If no fertilization

estrogen and progesterone inhibit GnRH and LH

corpus luteum degenerates (no LH) corpus albicans

levels of estrogen and progesterone

stop endometrial development

stimulate next menstruation

stimulate anterior pituitary hormones to begin next cycle

4) If fertilization occurs

corpus luteum maintained until the placenta takes over

maintained by hCG (human chorionic gonadotropin)

produced by chorion (outer embryonic membrane which becomes the

bulk of the placenta)

home pregnancy test detects hCG

placenta produces estrogen, progesterone

Physiology of Sexual Intercourse

Male Reproductive Act

3) Erection

may be initiated by anticipation, memory, visual stimulation or as a reflex from

physical stimulation

Parasympathetic stimulation causes vasodilation of capillary sinuses,

compression of veins erection

4) Lubrication

Parasympathetic impulses stimulate bulbourethral and urethral glands

glands secrete mucus for lubrication

Physiology of Sexual Intercourse

3) Orgasm

tactile stimulation causes ejaculation

intense stimulation causes rhythmic sympathetic impulses causing

peristaltic contractions of ducts propelling spermatazoa into ductus

(vas) deferens urethra

simultaneous stimulation of seminal vesicles, prostate and

bulbourethral glands add seminal fluid to the spermatazoa

stimulation of skeletal muscle at the base of the penis triggers rhythmic

contractions to help expel semen ejaculation

sensory input including HR, BP, RR, pleasurable sensations, along with

ejaculation, define male orgasm

followed by a refractory period

Female Reproductive Act

3) Arousal mediated by Parasympathetic Division of ANS

stimulation of breasts, genitalia, especially the clitoris, generates arousal

clitoris, vaginal mucosa and breasts engorge with blood

lubrication - secretion of mucus from epithelium of the cervical mucosa

4) Orgasm (climax) - maximal tactile stimulation of genitalia results in orgasm, mediated by

Sympathetic Division (ANS)

perineal muscles contract rhythmically; general increase in muscle tension;

rhythmic contractions of the uterus

engorgement of clitoris, breasts

HR, RR, BP

intense pleasurable sensations