Transcript Reproductive Systems, Pregnancy, and Development

Meiosis

Division of cells (in ovaries and testes)
forming haploid gametes
 Haploid: ½ number of chromosomes
○ Humans: 23 chromos in gametes
 Gametes: Sex cells (sperm and egg)

Occurs in two divisions (Meiosis I and
Meiosis II) which leads to new four cells
Testes
Ovoid structures located within the scrotum
 Covered in connective tissue

 Connective tissue also divided internal area into
lobules
 Each lobule has 1-4 seminiferous tubules
○ Function in spermatogenesis

Other cells surrounding tubules are
interstitial cells
 Function in production of male hormones
Spermatogenesis

During embryonic development:
 Spermatogonia in testes go through mitosis
and some enlarge to become primary
spermatocytes

Starting at puberty:
 Primary spermatocytes go through meiosis
becoming secondary spermaocytes (2) and
then spermatids (4)
 Review animation
Sperm cells

Acrosome
 Covering to head of sperm,
helps penetrate egg cell

Head
 Contains the nucleus

Midpiece
 Many mitochondria to supply energy to
support motion

Tail
 Flagellum that provides movement
Epididymis
Tightly coiled tube
 Starts on top of the testes and runs
along the posterior surface of the testes
 Receives immature sperms cells from
seminiferous tubules
 Matures sperm cells as peristalsis
moves them along

Vas Deferens
Muscular tube that enters abdominal
cavity
 Receives sperm from epididymis
 Combines with seminal vesicle near
prostate gland to become ejaculatory
duct

Seminal vesicle
Sac-like structure attached to vas deferens
near prostate gland
 Fluid is alkaline and contains fructose and
prostaglandins

 Alkaline- controls pH
 Fructose- provides energy for sperm
 Prostaglandins- stimulates contractions of female
reproductive system to move sperm towards egg
Prostate Gland
Surrounds urethra just under the urinary
bladder
 Secretes a thin, milky alkaline fluid

 Balances pH and enhances motility of sperm
Bulbourethral Gland
Within muscle fibers of external urethral
sphincter
 Secretes a mucous like fluid that lubricates
the glans penis

Semen
Fluid that leaves the male body
 Contains secretions from several gland
(as well as the sperm)
 One ejaculation:

 2-5 ml of fluid
 120 million sperm PER ml = 250-500 million
sperm per ejaculation
Scrotum
Sac enclosing testis
 Divided into two chambers by septum
 Move towards or away from body
depending upon temperature
 Optimal temperature is about 36°C

Penis
Transfers urine and semen to outside
 Body (shaft)

 Contains 2 corpus cavernosa and 1 corpus
spongiosum
 Where blood accumulates during erection

Glans penis
 Enlarged, sensitive area at the end of the penis
 Covered by the prepuce (foreskin)
○ Can be removed by circumcision
Erection
 Parasympathetic
system releases NO
(nitric oxide) during sexual stimulation
 NO cause arteries in penis to dilate and
veins to be compressed (blood collects
in penis)
 Emission- movement of sperm into
urethra
 Ejaculation- movement of semen to
outside
 Bulbourethral gland  Prostate gland 
Sperm  Seminal vesicle
How can you remember???
P-
Point= Erection
(Parasympathetic)
S- Shoot= Ejaculation
(Sympathetic)
Hormonal Control
Hypothalamus secrete Gonadotropinreleasing hormone
 Pituitary gland releases FSH and ICSH

 ICSH
○ Stimulates production of testosterone
 FSH
○ Stimulates seminiferous tubules to respond to
testosterone
Testosterone





Increases growth of
body hair
Enlargement of larynx
and thickening of vocal
cords
Thickening of skin
Increased muscular
growth
Thickening and
strengthening of bones
Ovaries
Two ovoid structures in the pelvic cavity
 Two regions:

 1) Medulla- inner area, loose connective
tissue, blood vessels, lymphatic vessels,
and nerves
 2) Cortex- compact tissue with a glandular
appearance due to follicles
Oogenesis

During embryonic development, several
million primordial follicles develop in cortex
 Each follicle contains a primary oocyte and
surrounding follicular cells
 Primary oocytes begin meiosis
 Stopped (until puberty – when they complete
Meiosis)

Many of the primary oocytes will
degenerate and only 400 to 500 will be
released during a lifetime
Oogenesis (cont)
During each cycle after puberty, primary
oocyte finishes Meiosis I dividing into
large secondary oocyte and very small
first polar body
 After fertilization, secondary oocyte will
undergo Meiosis II to form the zygote
and a second polar body

Comparison: Spermatogenesis
vs. Oogenesis
Male
Female
Can occur before
birth, occurs
everyday until death
Before birth, egg
development
continues during
puberty, halts during
menopause (~50 yo)
Timing
Testis
Ovary
Location
4 haploid sperm cells
Produced
1 haploid egg cell, 3
polar bodies
Spermatogenesis
Oogenesis
Follicular maturation and
Ovulation
Follicular maturation leads to secondary
oocyte and organized layers of follicle cells
 Follicle cells bath oocyte in follicular fluid
and enventually pushes oocyte against the
ovary wall to form a blister
 Ovulation occurs when the ovary wall
ruptures releasing the secondary oocyte

Uterine Tubes
Also called fallopian tubes
 Tube expands near the ovary in an area
called infundibulum with finger-like
extensions called fimbriae
 Cilia and peristalsis move the oocyte
down the tube

Uterus
Hollow organ that protects and supports
developing embryo
 Uterine tube connects at the dome of the
uterus
 Neck, or cervix, of the uterus opens into the
vagina
 Three layers:

 1) Endometrium- inner mucous layer
 2) Myometrium- thick, muscular layer
 3) Perimetrium- outer serous layer
Vagina
Fibrous, muscular tube connecting uterus to
the outside
 Hymen

 Epithelium and connective tissue that partially
covers the vaginal opening

Three layers:
 1) Mucosal layer- no mucous glands
 2) Muscular layer
 3) Fibrous layer
Vulva

Labia Majora
 Outer folds protecting openings to urethra and vagina met
together anteriorly at the mons pubis

Labia Minora
 Inner folds with pinkish color met anteriorly to form clitoris
hood

Clitoris
 Small projection rich in nerves

Vestibule
 Space enclosed by labia minora

Vestibular glands
 Located on either side of the vagina, secrete mucous
Mammary Glands
Adipose and glandular tissue
 Responsible for lactation after birth
 Milk moves from the alveolar ducts to
lactiferous ducts to the nipple which is
surrounded by the areola

Changes during Sexual
Stimulation
Release of NO (nitric oxide)
 Release of mucous to lubricate the
vestibule and vagina

Female Sex Hormones
Hypothalamus releases gonadotropin
releasing hormone
 Pituitary gland releases FSH and LH

 FSH: stimulates maturation of the follicle
○ Maturing follicle produces estrogens
 LH: stimulates ovulation, promotes formation of
corpus luteum

Corpus luteum secretes progesterone and
estrogen
Climacteric

Males:
 Decrease in
testosterone as age

Females:
 Decrease in estrogen
and lack of
progesterone
 Menses cease
(menopause)
Birth Control

Types:
 1) Timing
○ Ex: Withdrawal before ejaculation, abstinence
 2) Mechanical
○ Ex: male condom, intrauterine device, female
diaphragm
 3) Chemical
○ Ex: creams, foam, jellies with spermicidal
properties
○ Create unfavorable conditions for sperm to live
Birth Control

Types:
 4) Hormonal
○ Ex: birth control pill (injection, oral pills, patch)
○ If used correctly, can be 100% effective
○ Cause: nausea, breast tenderness, skin
pigmentation
 5) Surgical
○ Ex: vasectomy (males) – remove small section of
vas deferens; tubal ligation (females) – uterine
tubes are cut and ligated
Pregnancy
Gestation: 38 weeks
 Divided into three trimesters
 Changes in circulatory system:

 Developing fetus is nourished by umbilical cord
 Two arteries carrying deoxygenated blood, one
vein carrying oxygenated blood
 Some blood goes to liver while the rest
bypasses it using the ductus venosus
 Foramen ovale- opening between the atria that
allows decreased blood flow to the lungs during
fetal development
Disorders and Diseases

PCOS: Polycystic ovarian syndrome
 Cysts grow on external layers of ovary
 Prevent ovulation and hormone production

Endometrious
 Tumors on lining of uterus
 Can cause infertility

Prostate and Breast Cancer
 Rapidly dividing cells inside prostate and mammary gland
tissue

Pelvic inflammatory disease
 Usually caused by STD
 Infection of uterus, fallopian tubes and/or vagina in women
 Can cause infertility