Transcript Chapter 16 The Reproductive System

Chapter 16 The Reproductive
System
Biology 110
Tri-County Technical College
Pendleton, SC
Functions
• System insures continual existence of
human species
• ONLY system NOT essential to survival of
the individual
• Produces, stores, nourishes, and transports
functional female and male reproductive
cells called gametes
Male Reproductive System
• Identify and/or label the following
components of the male reproductive
system:
• Penis (shaft, glans, prepuce), testes,
epididymis, ductus deferens, seminal
vesicles, bulbourethral gland, prostate
gland, urethra, and ejaculatory duct
Male Visual
Male Visual, II
Products of Testes…and more
• Endocrine products are androgens (most
important is testosterone)
• Exocrine products are sperm
• Semen is mixture of sperm and accessory
gland secretions
• Secretions supply liquid for transport and
nutrition, and contains chemicals that
protect sperm and aid their movement
More, cont.
• Semen is alkaline (pH 7.2-7.6) which helps
neutralize acid environment (3.5-4) of
female’s vagina
• Also contains chemicals that inhibit
bacterial multiplication
• Dilutes sperm to assist their motility
• Ejaculation contains ~ 2-5 mls of semen
with 50-130 million sperm per ml
More, III
• Seminal vesicles located at base of bladder
produce ~60% of fluid volume of semen
– Thick, yellowish fluid rich in fructose, vitamin C,
prostaglandins, & other stuff which nourish & activate
sperm passing through tract
• Prostate gland (almond) encircles upper prostatic
part of urethra just below bladder
– secretes milky fluid that helps activates sperm
– During ejaculation, fluid enters urethra through several
small ducts
Last of the More, IV
• Bulbourethral glands (pea size), inferior to
prostate gland, produce thick, clear mucus
that drains into penile urethra
• This secretion first to pass down urethra
when man becomes sexually excited
• Believed to cleanse the urethra of traces of
acidic urine and serve as lubricant during
sexual intercourse
Directions…what are directions?
• Seminiferous tubulesrete testis epididymis
(20 days, mature and gain ability to
swim)ductus deferens ejaculatory duct
(passes through prostate) urethra
• Main function of ductus deferens to propel sperm
from storage sites (epididymis/distal part of ductus
deferens into urethra
• Ejaculation: thick layers of smooth muscle in DD
walls create perisaltic waves that propel sperm
• At ejaculation, sperm exit body via urethra
Definitions
• Penis is male copulatory organ for delivery
of sperm into female reproductive tract
• Spongy urethra surrounded by 3 areas of
erectile tissue that fills with blood during
arousal causing penis to enlarge and become
erect
• Events result in an erection which helps
penis serve as penetrating organ to deliver
sperm
Definitions II
• Ejaculation is sudden ejection of semen from the
penis
• In males, urethra carries both urine and sperm but
they never pass at same time
• When ejaculation occurs, bladder sphincter
constricts
• Prevents urine from passing into urethra and also
prevents sperm from entering urinary bladder
• Circumcision: removal of prepuce (foreskin)
from the penis
Female Reproductive System
• Paired ovaries responsible for
manufacturing ova (egg)
• Uterine tubes, uterus, & vagina form duct
system of female reproductive tract
• Uterine (fallopian) tubes receive oocyte and
provide site for fertilization
– No contact between ovaries & uterine tubes
(fimbriae)
Female R. S., cont.
• Uterus (womb) is hollow organ for receiving,
retaining, and nourishing fertilized egg
– Body, fundus, and cervix
• Vagina (birth canal) provides passageway for
delivery of infant, menstrual flow to leave body,
and receiving of penis and semen during sexual
intercourse (female copulation organ)
• External genitalia often called the vulva
– mons pubis, libia, clitoris, urethral/vaginal orifices, and
greater vestibular glands
Female Visual
Graafian Follicle/Corpus Luteum
• Mature follicle called graafian follicle
– Occurs when fluid-filled spaces of secondary follicle
fuse to form single fluid-filled antrum
– Increases in size, fills with additional fluid forming
lump on ovary surfaceblister
• Usually only one graafian follicle reaches most
advanced development stage and is ovulated
• Expands and ruptures forcing small amount of
blood and follicular fluid out of vesicle
• Secondary oocyte surrounded by cumulus mass
and zona pelucide escape from follicle=ovulation
Following the Follicle…
• After ovulation, ruptured follicle transformed into
corpus luteum
• Granulosa cells/theca interna (luteal cells) enlarge
and begin to secrete progesterone and small
amount of estrogen
• Will eventually degenerate
• If pregnancy occurs, becomes corpus luteum of
pregnancy and remains throughout pregnancy
• Its progesterone essential for maintaining the
placenta until it can begin to make and secrete its
own progesterone
Ovary Visual
The Uterus and its linings
 Uterus wall composed of 3 layers
 Endometrium is inner layer (mucosa)
 Fertilization occurs, embryo burrows into this
layer in process called implantation
 Embryo/fetus resides there for rest of
development
 If woman not pregnant, layer sloughs off
periodially (~28 days) in process called menses
 Occurs in response to changes in levels of
ovarian hormones
Uterus, cont.
• Myometrium is bulky middle layer of
interlacing bundles of smooth muscle
– Plays active role in delivery of baby by
contracting rhythmically
• Epimetrium (visceral peritoneum) is
outermost serous layer of uterus
• Ovulation defined (enough already) as
release of ovum (egg) from graafian follicle
of the ovary
Uterus Visual
Regions of the Uterus
• Major portion called the body
• Superior, rounded portion above entrance of
uterine tubes called the fundus
• Narrow outlet which protrudes into vagina
called the cervix
– Cancer of cervix common in women 30-50
– risk factors include frequent cervical
inflammations, multiple pregnancies, STDs,
active sex life with multiple partners, and age at
onset of sexual activity (yearly Pap Smear)
Uterus Visual
Making Sex Cells…so to speak
• Meiosis; somatic cells and sex cells, diploid
and haploid, 2N and N
• Spermatogenesis: production of sperm from
primitive stem cells called spermatogonia
• FSH (anterior pituitary) stimulates
spermatogonia to divide into Type A (stem)
and Type B (primary spermatocyte) cells
• Type B cells will undergo meiosis and form
4 sperm
Sex Cells, cont.
• In spermatogenesis, gametes are called
spermatids (sperm)
• In last stage of formation, all excess
cytoplasm discarded and remaining “stuff”
compacted into 3 regions of mature sperm:
head, midpiece, and tail
• Acrosome located on very tip of head
• Entire process takes 64-72 days
Spermatogenesis Visual
Oogenesis
• Oogonia (female stem cells) formed during
female fetus development
• Daughter cells (primary oocytes) push into ovary
connective tissue where they become surrounded
by single layer of cells=primary follicles
• By time female baby born, oogonia no longer
exists, and female’s lifetime supply of primary
oocytes already in place in ovarian follicles
(~700,000)
Oogenesis, cont.
• FSH controls ovarian cycle
• Follicle grows larger, accumulating fluid in
central chamber called antrum
• Primary oocyte begins meiosis=2 cells very
dissimilar in size
• Larger one is secondary oocyte, smaller one
is a polar body
• LH causes release of secondary oocyte from
ovary
Oogenesis, cont.
• Ovulated secondary oocyte surrounded by its
follicle cell capsule now called corona radiata
• If secondary fertilized, its nucleus undergoes
second meiotic division that produces another
polar body and the ovum nucleus
• If not fertilized, secondary deteriorates w/o
completing meiosis II to form functional egg
Oogenesis Visual
Sperm Structure
• Sperm head contains DNA (essentially the
nucleus of the sperm)
• Acrosome positioned on tip of head;
contains enzymes to help penetrate the egg
• Midpiece contains centrioles from which
tail (flagellum) arises; mitochondria also
located here
• Tail (flagellum) for propelling sperm long
distance in very short amount of time
Hormones are Flowing…
• FSH responsible for spermatogenesis in males and
maturation of primary follicles in females
• LH responsible for testosterone production in
males and ovulation in females
• Testosterone most important hormonal product of
testes
• Responsible for development of reproductive
organs to adult size, male sex drive, and male
secondary sexual characteristics
– deepening voice, growth of body hair, enlargement of
skeletal muscles, increased heaviness of skeleton
Menstrual Cycle Phases
• Divided into 3 stages
• Menses (1-5): endometrial lining sloughed
off and detaches from uterine wall
• Accompanied by bleeding for 3-5 days
• Detached tissues and blood pass through
vagina as menstrual flow
• Average blood loss is 50-150 ml (1/4 to ½
cup)
Cycles, cont.
• Proliferative stage(6-14) endometrium
repaired, glands formed in it, and
endomertial blood supply is >ing
• Stimulated by rising estrogen levels
produced by glowing follicles of ovary
• Endometrium becomes velvety and thick
• Ovulation occurs at end of this stage in
response to sudden surge of LH in blood
Cycles, cont.
• Secretory stage (15-28): rising levels of
progesterone (corpus luteum) act on
estrogen primed endometrium and > its
blood supply even more
• Progesterone causes endometrial glands to >
in size and begin secreting nutrients into
uterine cavity
– These nutrients will sustain developing embryo
until it can implant
Cycles, cont.
• Fertilization occurs, embryo produces hormone
similar to LH which causes corpus luteum to
continue its hormone production
• If fertilization does NOT occur, CL begins to
degenerate toward end of this period (stage) as LH
blood levels begin to decline
• Lack of hormones causes blood vessels supplying
endometrium to spasm and kink
• Deprived of oxygen and nutrients, endometrial
cells begin to die which sets stage for menses
More definitions, yeah!!!!
• Females reach peak reproductive age in late 20s
and its downhill from there
• Eventually ovulation and menses cease entirely
• This event, menopause, considered to have
occurred when whole year passes w/o
menstruation
• Fertilization occurs at moment genetic material
from sperm combines with that of ovum to form
fertilized egg called a zygote; restores diploid
count and forms single cell representing first cell
of new individual
Definitions, cont.
• Embryo: from zygote through 8 weeks
– by end, looks human and all organ systems
present in rudimentary form
• Fetus: from 9 weeks until delivery
• Major activities NOW growth and organ
specialization accompanied by changes in
body proportions
Functions of the Placenta
• Implantation completed and uterine mucosa grown
over burrowed-in embryo by day 14 after
ovulation
• Trophoblast part of blastocyst develops
projections called chorionic villi which cooperate
with uterine tissues to form placenta
• By 3rd week, placenta functioning to deliver
nutrients and oxygen and remove wastes from
embryonic blood
Functions, cont.
• ALL exchanges made through the placental
barrier
• By end of second month, placenta becomes
endocrine organ and is producing estrogen,
progesterone, and other hormones to
maintain the pregnancy
• At this time, corpus luteum of ovary
becomes inactive