Biology 233
Human Anatomy and Physiology
Chapter 28 Lecture Outline
REPRODUCTIVE SYSTEM
Functions of Reproductive System
production of offspring – continuation of species
genetic recombination – individual variation, adaptation
SEXUAL REPRODUCTION
gametogenesis – production of gametes (reproductive cells)
female – oogenesis produces oocytes (eggs)
male – spermatogenesis produces spermatozoa (sperm)
fertilization – male and female gametes united
coitus (sexual intercourse) – male gametes transmitted to female
prenatal development – development of fetus in uterus
GAMETOGENESIS
gonads – site of gamete production
female – ovaries
male – testes
Distribution of Genetic Material
somatic (body) cells
diploid (2N) – contain 23 pairs of chromosomes (total 46)
homologous pairs (1 homlog from each parent)
gametes (reproductive cells) – oocytes and spermatozoa
haploid (1N) – contain 23 unpaired chromosomes
zygote – cell produced by fertilization
diploid – 23 pairs of chromosomes (total 46)
23 chromosomes from female gamete
23 chromosomes from male gamete
Mitosis – cell division which produces 2 identical, diploid daughter cells
Interphase – chromosomes replicate to form sister chromatids
Prophase – chromosomes condense and become visible
Metaphase – chromosomes line up at equatorial plate
Anaphase – sister chromatids separate and migrate to opposite poles
Telophase – cytoplasm divides to form 2 identical, diploid daughter cells
MEIOSIS – 2 stage cell division which produces 4 haploid gametes
occurs in gonads
gametes produced are not genetically identical to parent cell
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STAGES OF MEIOSIS:
Meiosis I – a diploid cell divides and forms 2 haploid cells
Interphase I - chromosomes replicate
each chromosome is joined to an identical sister chromatid
Prophase I – chromosomes condense, genetic recombination occurs
synapsis – pairing of homologous chromosomes
tetrad – 4 chromosomes (homologous pair + their
sister chromatids)
crossing-over – exchange of genes between homologous pairs
Metaphase I – homologous chromosomes line up at center
Anaphase I – homologous chromosomes separate
Telophase I – 2 haploid daughter cells formed
each has only one homolog with its sister chromatid
Meiosis II – the 2 haploid cells divide again, forming 4 haploid cells
Prophase II – chromosomes condense
Metaphase II – chromosomes line up
Anaphase II – sister chromatids separate
Telophase II – 4 haploid daughter cells formed
none are identical due to crossing-over
MALE REPRODUCTIVE SYSTEM
TESTES – male gonads
site of spermatogenesis – production of spermatozoa
produce male hormones (androgens)
develop in abdominal cavity near kidneys
Descent of the Testes – testes move out of abdomen and into scrotum
begins at about 7th month of fetal development
inguinal canals – tunnels through anterior abdominal wall
inguinal rings – openings at either end of canal
spermatic cord – ductus deferens, blood vessels, and nerves
running through inguinal canal to supply testes
also surrounded by fascia and muscle
scrotum – sac of integument and superficial fascia
suspends testes at root of penis
scrotal septum divides into 2 halves
Purpose of Descent – cools testes
normal sperm production requires temperature below body temp
regulation of temperature – testes elevated in response to cold
dartos muscle – smooth muscle in scrotum
cremaster muscle – skeletal muscle in spermatic cord
and surrounding testis
inguinal hernia – abdominal contents slip through inguinal canal
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ANATOMY OF TESTES
tunica vaginalis – superficial layer; serous membrane covering testis
derived from peritoneum
tunica albuginea – deep layer; dense irregular connective tissue
covers surface of testes and divides it into lobules
seminiferous tubules – coiled tubules within lobules
sites of spermatogenesis
2 types of cells:
spermatogenic cells – form spermatozoa
sustentacular (Sertoli) cells – support spermatogenesis
secretions – nutrients, chemical stimuli, hormones
blood-testis barrier – regulates environment, protects
spermatogenic cells from immune destruction
phagocytosis
Leydig (interstitial)cells – lie between seminiferous tubules
secrete androgens – mainly testosterone
SPERMATOGENESIS – in seminiferous tubules
spermatogonia (stem cells) – diploid
attached to basement membrane
undergo mitosis – produce many primary spermatocytes
1) primary spermatocyte – diploid
undergoes meiosis I
2) 2 secondary spermatocytes – haploid
1 of each homolog + its sister chromatid
undergoes meiosis II
3) 4 spermatids – haploid
1 copy of each chromosome
spermiogenesis – spermatids differentiate (grow flagellum, etc.)
4) 4 spermatozoa (sperm) – 300mil/day, 65-75 days for development
released into lumen of seminiferous tubule
sustentacular cell secretions wash sperm out of tubule
Anatomy of Spermatozoa
head
acrosome – tip containing lysosome-like vesicle
contains enzymes to penetrate oocyte
nucleus – genetic material; haploid
midpiece
mitochondria – produce ATP for movement
centrioles in neck
tail
flagellum (microtubules) – propels sperm
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REGULATION OF SPERMATOGENESIS
Hypothalamus – Gonadotropin Releasing Hormone (GnRH)
released regularly in pulses; stimulates anterior pituitary
Anterior Pituitary – gonadotropins (normal blood levels maintained)
Luteinizing Hormone (LH) – targets Leydig cells
Leydig cells produce testosterone
Follicle Stimulating Hormone (FSH) – targets sustentacular cells
sustentacular cells secrete androgen-binding protein (ABP)
ABP binds testosterone from Leydig cells
synergism of FSH and testosterone stimulates spermatogenesis
Negative Feedback
high testosterone inhibits GnRH release
high spermatogenesis rate
sustentacular cells secrete inhibin
inhibin inhibits FSH release
Other Functions of Testosterone
prenatal – male reproductive development
puberty – maturation of testes and genitals
secondary sexual characteristics
hair growth pattern, deep voice
anabolic – stimulate protein synthesis
increase mass of tissues (bone, muscle)
behavior and libido (sex drive)
MALE REPRODUCTIVE TRACT
EPIDIDYMIS – long (20ft) comma-shaped, coiled tube on posterior testis
collects sperm from testis
site of sperm maturation (10-14 days) – maintain environment that
favors development; secretes nutrients, reabsorbs wastes
Anatomy of Epididymis:
head – superior portion
body
tail – inferior portion
Histology of Epididymis:
pseudostratified columnar epithelium
stereocilia (long microvilli) – increase surface for
secretion and absorption
smooth muscle – peristalsis moves sperm forward
DUCTUS (VAS) DEFERENS – 18 inch tubule, conducts sperm from epididymis
through inguinal canal and pelvic cavity to prostate
ampulla – dilated distal end
stores sperm – up to several months
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Histology of Ductus Deferens
pseudostratified columnar epithelium
3 layers of smooth muscle – peristalsis moves sperm into urethra
EJACULATORY DUCT – 1 inch duct
union of ductus deferens and duct from seminal vesicle
lies within prostate
conducts sperm and seminal secretions to urethra
URETHRA – 8 inch duct; carries semen and urine to exterior
prostatic urethra
membranous urethra
spongy (penile) urethra
external urethral orifice
MALE ACCESSORY GLANDS – secrete seminal fluid (liquid portion of semen)
Seminal Vesicles
posterior to bladder
secretion – alkaline, viscous fluid (60% of semen)
neutralizes acidity that is harmful to sperm
fructose – ATP source for sperm motility
prostaglandins – stimulate sperm motility and smooth muscle
contractions in male & female repro. tracts
clotting proteins – semen clots after ejaculation
Prostate
round gland; surrounds superior urethra
secretion – milky (30% of semen)
seminalplasmin – antibiotic enzyme
citric acid – ATP source for sperm
proteolytic agents – break down clotting agents
Bulbourethral Glands
2 small, round glands in urogenital diaphragm
inferior to prostate
secretion – alkaline mucus (5% of semen)
neutralizes acid in urethra
lubricates urethra and end of penis
SEMEN
sperm + seminal fluid
2-5 ml / ejaculation
50-100 million sperm (<20 mil = likely infertile)
slightly alkaline – pH 7.2-7.7; buffers acidity in female repro. tract
coagulates within 5 minutes
reliquifies after 15-30 minutes
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PENIS – organ of sexual intercourse
transmits sperm to female for fertilization
External Anatomy of Penis
root – proximal attachment
body – main, central portion
glans – expanded distal end
prepuce (foreskin) – protective skin flap covering glans
smegma – waxy secretion from glands of prepuce
circumcision – removal of prepuce
Cross-Sectional Anatomy of Penis (body)
integument - superficial
fascia and fibrous connective tissue – middle
erectile tissues – deep; contain extensive blood sinuses
erection – sexual stimulation dilates arteries to penis
blood sinuses of erectile tissues fill
expansion of erectile tissues compresses veins
penis enlarges and stiffens (vasocongestion)
corpora cavernosa – 2 large, dorsolateral columns of erectile
tissue; cause erection
crura of penis – extensions of cavernosa into root of penis
corpus spongiosum – ventral tube of erectile tissue
surrounds and prevents collapse of spongy urethra
glans – distal enlargement of spongiosum
Male Sexual Function
arousal – physical and psychological stimuli
parasympathetic reflex – vasodilation in penis leads to erection
continued stimulation:
stimulates glandular secretions and peristalsis in ductus deferens
emission – sympathetic reflex triggers contraction of glands
discharge of small amount of semen before ejaculation
peak stimulation (orgasm) – somatic reflex
rhythmic contractions of bulbospongiosus and ischiocavernosus
muscles of penis
ejaculation – semen propelled from ductus deferens and urethra
into vagina
FEMALE REPRODUCTIVE SYSTEM
OVARIES – female gonads
site of oogenesis
produce female hormones (estrogens, progestins)
lateral to uterus; superior to pelvic brim
suspended by ligaments derived from peritoneum
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ANATOMY OF OVARIES
almond-shaped
hilus – blood vessels and nerves enter and exit
suspensory ligament anchors to pelvic wall
germinal epithelium – visceral peritoneum lining surface
usually appears cuboidal
tunica albuginea – dense irregular CT layer deep to germinal epithelium
Ovarian Cortex – outer region
ovarian follicles
developing oocytes in center of follicle
surrounding cells – nourish oocytes and secrete hormones
follicular cells – single layer of squamous cells around
undeveloped primary oocytes
granulosa cells – 1 or more layers of cuboidal cells around
developing oocytes; produce secretions
dense irregular CT and smooth muscle
Ovarian Medulla – inner region
loose CT, vessels and nerves
OOGENESIS AND FOLLICULAR DEVELOPMENT
oogonia (stem cells) – diploid
before birth – undergo mitosis; form millions of primary oocytes
atresia – most degenerate (about 400 reach maturity)
1) primary oocytes (diploid) – begin meiosis I before birth
arrested development – don’t complete meiosis I
primordial follicles – single layer of follicular cells around a
primary oocyte; found near tunica albuginea
OVARIAN CYCLE – begins at puberty
hormones activate a group of primordial follicles each month
primary follicles
follicular cells divide, forming multiple layers of granulosa cells
zona pellucida – clear, glycoprotein layer around oocyte
thecal cells – CT surrounding follicle; nourishes follicle and helps
it produce hormones
secondary follicles – a few primary follicles mature to this stage
pockets of secretions from granulosa cells surround primary oocyte
tertiary follicle – normally only 1 secondary follicle matures to this stage
antrum – fluid-filled pocket in center of follicle
2) secondary oocyte – as tertiary follicle develops, the primary oocyte it contains
completes meiosis I, forming haploid cells
secondary oocyte – 1large cell; receives most of cytoplasm during division
first polar body – 1 small, discarded cell with no cytoplasm
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secondary oocyte begins meiosis II
arrested at metaphase II (not completed unless fertilized)
corona radiata – crown of granulosa cells around oocyte
ovulation – mature follicle ruptures and releases secondary oocyte and its
corona radiata into the pelvic cavity
normally release 1 oocyte/cycle
FATE OF SECONDARY OOCYTE
1) sperm in uterine tube (within 24 hr of ovulation)
fertilization – sperm penetrates secondary oocyte
oocyte resumes meiosis II – unequal cytokinesis
ovum (haploid) – mature egg; large cell
second polar body – small, discarded cell
nuclei of sperm and ovum unite
zygote (diploid) – divides and differentiates to
form fetus
2) no sperm in uterine tube
degeneration of secondary oocyte and all related structures
UTERINE TUBES (oviducts, Fallopian tubes)
site of fertilization
4 inch tubes; conduct sperm to secondary oocyte and zygote to uterus
Anatomy of Uterine Tubes
infundibulum – superior, funnel-shaped portion
fimbriae – fringe on border; sweep oocyte into infundibulum
ampulla – wide, lateral portion of tube
isthmus – narrow, medial portion of tube; connected to uterus
Histology of Uterine Tubes
mucosa
ciliated columnar epithelium – sweeps oocyte through tube
secretory cells – nourish oocyte, sperm, and zygote
muscularis
smooth muscle – peristalsis helps move oocyte
serosa – peritoneum
UTERUS (womb) – supports the zygote during prenatal development
between urinary bladder and rectum
size and shape of an inverted pear
size depends on sex hormone levels
supported by broad ligaments and round ligaments
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Anatomy of Uterus
fundus – broad, superior portion
body – central portion
cervix – narrow, inferior portion; opens into vagina
uterine cavity – interior of uterus
Histology of Uterus
1) perimetrium (outer layer) – visceral peritoneum
2) myometrium (middle layer)
3 layers of smooth muscle
contracts during childbirth and menstruation
3) endometrium (inner layer) - highly vascular; supports developing fetus
simple columnar e. w/ cilia and secretory cells
thick lamina propria (endometrial stroma) – areolar CT
endometrial glands
2 functional layers:
functional zone – lines uterine space
develops to support fetus; sloughs during menstruation
basal zone – deep layer
permanent stem cell layer
VAGINA
3-4 inch canal from cervix to exterior of body
site of sexual intercourse
birth canal
outlet for menstrual flow
fornix – recessed area surrounding cervical os
vaginal orifice – opening to exterior
hymen – fold of mucous membrane that partially or completely closes the
vaginal orifice in childhood
Histology of Vagina
1) mucosa – stratified squamous e./lamina propria
rugae – transverse folds
normal bacterial flora – create an acidic environment
inhibits other microbes (eg. yeast)
harmful to sperm – semen buffers acid
2) muscularis – smooth muscle
3) adventitia – loose, fibrous CT
VULVA (pudendum) – external genitals
mons pubis – bulge due to adipose tissue cushioning pubic symphysis
covered by integument and pubic hair
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labia majora – outer skin folds around vaginal orifice
homologous to scrotum
labia minora – inner skin folds w/hair around vaginal orifice
homologous to spongy urethra – contains erectile tissue
clitorus – erectile tissue anterior to vaginal orifice
homologous to corpus cavernosum – erectile tissue
prepuce covers most of clitorus
glans – exposed portion
vestibule – region between labia minora
vaginal orifice
external urethral orifice – between vaginal orifice and clitorus
openings of glands – lubricate vestibule and vagina
PERINEUM – diamond-shaped area between thighs and buttocks of male or female
region of pelvic outlet
contains external genitalia and anus
boundaries – pubic symphysis, ischial tuberosities, coccyx
FEMALE REPRODUCTIVE CYCLE
HORMONAL REGULATION
Hypothalamus
Gonadotropin Releasing Hormone (GnRH)
stimulates anterior pituitary
Anterior Pituitary
Follicle Stimulating Hormone (FSH)
stimulates follicle growth
stimulates estrogen secretion by follicle cells
Luteinizing Hormone (LH) – secreted as estrogens increase
stimulates follicle maturation (synergistic with FSH)
LH peak triggers ovulation
promotes differentiation of follicle after ovulation
corpus luteum – granulosa cells differentiate
secrete progesterone, estrogens, inhibin
Estrogens – synthesized by ovarian follicles from cholesterol
functions:
development of female reproductive organs in fetus
secondary sexual characteristics after puberty
fat distribution, breast development, wide pelvis
anabolic – promote bone and muscle growth
stimulate development of the endometrium
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Progesterone – secreted by corpus luteum after ovulation
acts synergistically with estrogens to build and maintain endometrium
supports pregnancy (implantation and nourishment of fetus)
prepares mammary glands for milk production
feedback inhibition of GnRH = less FSH secretion
prevents further follicle development during pregnancy
Inhibin – from developing follicles and corpus luteum
inhibits FSH secretion
delays development of more follicles during ovulation and pregnancy
PHASES OF REPRODUCTIVE CYCLE
24-35 days (average 28)
4 phases:
1) Menstrual Phase (day 1-5)
no fertilization of oocyte
corpus luteum degenerates – becomes corpus albicans (scar)
progesterone level declines
uterus sloughs functional zone of endometrium
menstruation – blood, epithelial cells, mucus
low progesterone stimulates GnRH and FSH secretion
FSH > LH = follicular development in ovaries
2) Proliferative (Preovulatory) Phase (day 6-13 / variable length)
developing follicles secrete estrogens
dominant follicle matures
others inhibited by inhibin and < FSH
(fraternal twins – development of 2 mature follicles)
estrogen stimulates growth of functional zone of endometrium
maturing follicle produces increasing estrogen level
3) Ovulation (day 14)
estrogen peak stimulates GnRH and LH secretion
LH peak causes ovulation
primary oocyte resumes meiosis – forms secondary oocyte
mature follicle ruptures
secondary oocyte released
(LH level can be used to predict ovulation)
4) Secretory (Postovulatory) Phase (day 15-28)
LH stimulates formation of corpus luteum
corpus luteum secretes progesterone and estrogen
progesterone and estrogens promote secretions of endometrium
endometrial glands grow – secrete glycogen (ATP source)
endometrial vasculature increases
LH > FSH, and inhibin from corpus luteum inhibit follicle development
No Fertilization – corpus luteum degenerates to corpus albicans after 2 weeks
progesterone, and inhibin levels decline
new cycle begins
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Fertilization
human chorionic gonadotropin (hCG) – produced by embryo
maintains corpus luteum
maintains progesterone and estrogens
maintains endometrium to nourish embryo
(hCG is detected by early pregnancy tests)
Oral Contraceptives
synthetic estrogens and progestins
feedback inhibition of GnRH and FSH
inhibit follicle development
MAMMARY GLANDS
modified sweat glands
within subcutaneous tissue overlying pectoral muscles
lactation – secretion of milk following parturition (giving birth)
Anatomy of Mammary Gland
irregular connective tissue containing adipose
suspensory ligaments within CT support breast
15-20 lobes – grape-like clusters of glands
lactiferous glands – glands that produce milk
stimulated by prolactin + correct levels of progesterone,
estrogens, growth hormone, thyroid hormone, etc.
regular nursing required to maintain hormone levels
lobes drain into lactiferous ducts ---->
lactiferous sinuses (expansions that store some milk) ---->
lactiferous ducts -----> open in nipple
areola – pigmented area around nipple
myoepithelial cells – contractile cells in ducts and sinuses
contraction expels milk
stimulated by oxytocin in response to suckling
SEXUALLY TRANSMITTED DISEASES
Bacterial
Chlamydia – inflammation, pain, sterility
Gonorrhea (clap) – inflammation, pus, sterility, blindness in newborn
Syphilis
primary stage – open sore (chancre)
secondary stage – systemic; rash, fever, joint and muscle pain
tertiary stage – organ degeneration; may affect nervous system
Viral
AIDS – immune suppression
Genital Herpes – genital blisters and sores; no cure
Genital Warts – warts on genitals; may predispose to cancer
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