Transcript 10a Reproductive System

Male Reproductive Anatomy and Physiology
 Overview of the Reproductive System
 Parts of the Male Reproductive System
 Testes and Epididymis
 Ductus Deferens and Urethra
 Accessory Glands
 External Genitalia
 Spermatogenesis and Mature Sperm
 Testosterone Production
The Reproductive System
 Gonads – primary sex organs
• Testes in males
• Ovaries in females
 Gonads produce gametes
(sex cells) and secrete
hormones
• Sperm – male gametes
• Ova (eggs) – female
gametes
Male Reproductive System
 Testes
 Duct system
• Epididymis
• Ductus deferens
• Urethra
 Accessory organs
• Seminal vesicle
• Prostate gland
• Bulbourethral gland
 External genitalia
• Penis
• Scrotum
Coverings of the Testes
 Coverings of the testes
(internal to the scrotum)
• Tunica vaginalis
o
Serous membrane
derived from
peritoneum; parietal
and visceral layers
• Tunica albuginea
– capsule that
surrounds each
testis
• Septa – extensions
of the capsule that
extend into the
testis and divide it
into lobules
Tunica
vaginalis
Testes
 Each lobule contains one to
four seminiferous tubules
• Tightly coiled structures
• Function as spermforming factories
• Empty sperm into the
rete testis
 Sperm travels through the rete
testis to the epididymis
 Sertoli (sustenacular) cells
provide nourishment for
developing sperm and protect
them from the body’s immune
system by housing them inside
their membranes.
 Interstitial (Leydig) cells
produce androgens such as
testosterone
Cross section of
seminiferous
tubule
Figure 16.1
Epididymis
 Comma-shaped, tightly
coiled tube
 Found on the superior part
of the testis and along the
posterior lateral side
 Functions to mature and
store sperm cells (at least
20 days)
 Sperm become motile
during their stay in the
epididymis
 Expels sperm with the
contraction of muscles in
the epididymis walls to the
vas deferens
Ductus Deferens, Ejaculatory Duct, Urethra
 Ductus (Vas) Deferens
•
Carries sperm from the epididymis to
the ejaculatory duct
•
Passes through the inguinal canal and
over the bladder
•
Moves sperm by peristalsis
•
Coated with microvilli-like stereocilia
that reabsorb some of the fluid
produced with the sperm
•
Spermatic cord – ductus deferens,
blood vessels, and nerves in a
connective tissue sheath
•
Ends in the ejaculatory duct which
unites with the urethra
 Vasectomy – cutting of the ductus
deferens on both sides, at the level of
the testes, to prevent transportation of
sperm. Sperm are reabsorbed.
Seminal Vesicles: Energy Source for Sperm
 Located at the base of the bladder
 Produces a thick, yellowish
secretion (60% of semen)
• Fructose (sugar)
• Vitamin C
• Prostaglandins
• Other substances that nourish
and activate sperm
Prostate Gland
 Encircles the upper part
of the urethra
 Secretes a milky fluid
• Helps to activate
sperm
• Alkaline fluid
added to neutralize
vaginal secretions.
• Adds ~ 30% of
total semen fluid
• Enters the urethra
through several
small ducts
• Easily palpated
through rectum
(check for cancer);
important in men
over 50.
Bulbourethral (Cowper's) Glands
 Pea-sized gland inferior to
the prostate
 Produces a thick, clear
mucus
• Cleanses the urethra
of acidic urine
• Adds a lubricant for
sperm during
ejaculation
• Secreted into the
penile urethra
Male Urethra
 Urethra
•
Extends from the base of the urinary
bladder to the tip of the penis
•
Carries both urine and sperm
•
Sperm enters from the ejaculatory
duct
 Regions of the urethra
• Prostatic urethra –
surrounded by prostate
• Membranous urethra –
from prostatic urethra to
penis
• Spongy (penile) urethra –
runs the length of the penis
External Genitalia
 Scrotum
• Divided sac of skin outside the
abdomen
• Maintains testes at 3°C lower than
normal body temperature to
protect sperm viability
 Penis
• Delivers sperm into the female
reproductive tract
• Regions of the penis
o
Shaft
o
Glans penis (enlarged tip)
o
Prepuce (foreskin)
 Folded cuff of skin
around proximal end
 Often removed by
circumcision
Semen Composition and Analysis
 Mixture of sperm and
accessory gland secretions
 Advantages of accessory
gland secretions
• Fructose from prostate
provides energy for
sperm cells
• Alkalinity of semen
(from seminal
vesicles) helps
neutralize the acidic
environment of vagina
• Semen inhibits
bacterial
multiplication
• Elements of semen
enhance sperm
motility
Source
Volume
Characteristics
Urethral and
bulbourethral
glands
0.1-0.2cc
Viscous, clear
Testes,
epididymides,vas
a deferentia
0.1-0.2cc
Sperm present
Prostate
0.5-1.0cc
Acidic,watery
Seminal vesicles
1.0-3.0cc
Gelatinous,
fructose positive
Complete
ejaculate
2.0-5.0cc
Liquefies in 2025min
Parameters of Normal, Fertile Semen
VOLUME
>2.0 ML
pH
7.2-7.8
CONCENTRATION
>20x106/ML
MOTILITY
>50%
MORPHOLOGY
>30% NORMAL MORPHOLOGY
WBC
< 1x106/ML
Regulation of Male Androgens (Sex Hormones)
Acts directly on
spermatogonia
Acts on Interstitial cells, called Interstitial Cell
Stimulating Hormone
Figure 16.6
Spermiogenesis (64-72 days)
Lumen
Inhibin
GnRH
-
+
testosterone
+
testosterone
Maturation
sequence
+
LH
(ICSH)
GnRH
Lumen
FSH
Testosterone
 Testosterone Production
• The most important hormone of the
testes
• Produced in interstitial cells
 Functions of testosterone
• Stimulates reproductive organ
development
• Facilitates spermatogenesis and
promotes the maturation of sperm
• Influences sexual desire and related
behaviours
• Causes secondary sex characteristics
o
Deepening of voice
o
Increased hair growth
o
Enlargement of skeletal muscles
o
Thickening of bones
Anatomy of a Mature Sperm Cell
Acrosome Reaction
(in sea urchins)
Acrosomal enzymes of
many sperm digesting
follicle cells around ovum
Diseases and Conditions of the Male Reproductive System

Cryptorchidism (undescended testicle)
•

Phimosis
•

External urethral meatus is below the tip
Variocele
•

Fluid-filled sac surrounding the testes
Hypospadias (literally “below the fleshy spike”)
•

Penis cannot be extruded from the prepuce (foreskin)
Hydrocele
•

Can lead to sterility and testicular cancer
Dialated and twisted veins of the testes, causes swelling
Orchitis and Epididymitis
•
Infections of the testicles and epididymus; may lead to sterility

Cancer (penile, prostate, testicular)

Balanitis

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Inflammation of the foreskin and head of penis due to
•
infection (old reason for circumcision)
Priapism
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
Constant state of erection due to neurological defect or damage
Peyronie’s Disease
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Hard lump forms on the penis in erectile tissue layers
MALE REPRODUCTIVE SYSTEM OVERVIEW ANIMATION
Reproduction II - Female Anatomy and Physiology
 Structures of the Female Reproductive System
• Ovaries
• Fallopian Tubes
• Uterus and Vagina
• External Genitalia
 Oogenesis
 Menstrual Cycle
 Female Sex Hormones
 Mammary Glands
Overview of Female Reproductive System
 Ovaries
 Duct System
• Uterine tubes
(fallopian
tubes)
• Uterus
• Vagina
 External genitalia
Ovaries
 Composed of ovarian follicles (sac-like
structures)
 Structure of an ovarian follicle
•
Oocyte
•
Follicular cells
 Primary follicle – contains an
immature oocyte. All primary oocytes
formed by birth, suspended in Prophase
I.
 Graafian (vesicular) follicle –
growing follicle with a maturing oocyte
and an antrum
 Ovulation – when the egg is mature the
follicle ruptures
•
Occurs about every 28 days
 The ruptured follicle is transformed
into a corpus luteum
Support for Ovaries
Support Structures
• Suspensory ligaments – secure ovary to lateral walls of the pelvis
• Ovarian ligaments – attach to uterus
• Broad ligament – a fold of the peritoneum, encloses suspensory ligament
Uterine (Fallopian) Tubes/Oviducts


Features of the Oviducts
•
Receive the ovulated oocyte
•
Provide a site for fertilization
•
Attaches to the uterus
•
Does not physically attach to the
ovary
•
Supported by the broad ligament
Functionality
•
Fimbriae – finger-like projections at
the distal end that receive the oocyte
•
Cilia inside the uterine tube slowly
move the oocyte towards the uterus
(takes 3–4 days)
•
Fertilization occurs inside the
uterine tube
Uterus




Features
•
Located between the urinary bladder and rectum
•
Hollow organ
Functions of the uterus
•
Receives a fertilized egg
•
Retains the fertilized egg
•
Nourishes the fertilized egg
Landmarks
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Body – main portion
•
Fundus – area where uterine tube enters
•
Cervix – narrow outlet that protrudes into the vagina
Uterine Walls
•
Endometrium
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Inner layer
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Allows for implantation of a fertilized egg
o
Sloughs off if no pregnancy occurs (menses)
•
Myometrium – middle layer of smooth muscle
•
Serous layer – outer visceral peritoneum (perimetrium)
Vagina
 Vagina extends from cervix
to exterior of body
 Behind bladder and in front
of rectum
 Serves as the birth canal
 Receives the penis during
sexual intercourse
 Hymen – partially closes the
exit of the vagina until it is
ruptured
Various forms taken by the normal hymen
External Genitalia
 Mons pubis
•
Fatty area overlying the pubic
symphysis
•
Covered with pubic hair after
puberty
 Labia – skin folds
•
Labia majora
•
Labia minora (hairless, pink)
 Vestibule
•
Area enclosed by labia majora
•
Contains opening of the urethra
and the greater vestibular glands
(produce mucus)
 Clitoris
•
Contains erectile tissue
•
Corresponds to the male penis
Oogenesis

Steps of Oogenesis
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Oocytes are matured in developing ovarian follicles
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Oogonia – female stem cells found in developing fetus,
divide mitotically-> 1o oocytes
•
Primary oocytes are surrounded by cells that form
primary follicles in the ovary
•
Oogonia no longer exist by the time of birth
•
Primary oocytes are inactive until puberty
•
Follicle stimulating hormone (FSH) causes some
primary follicles to mature
o
Meiosis starts inside maturing follicle producing a
secondary oocyte and the first polar body
o
Meiosis is completed after ovulation only if sperm
penetrates and two additional polar bodies are produced
Ovarian and Menstrual (Uterine) Cycle
 Cyclic changes of the endometrium
 Regulated by cyclic production of
estrogens and progesterone
 Stages of the menstrual cycle
•
Menstrual stage – functional
layer of the endometrium is
sloughed when progesterone
levels fall (corpus luteum
degenerates)
•
Proliferative stage – buidling
functional endometrial layer
coordinated with follicular
maturation, (stimulated by
follicles producing estrogen)
o
•
Ovulation occurs in this
phase, estrogen levels fall as
progesterone levels rise
Secretory stage – endometrium
increases in size and readies for
implantation, maintained by
progesterone from corpus luteum
Hormone Production by the Ovaries
 Estrogens
• Produced by follicle cells
• Cause secondary sex characteristics
o
Enlargement of accessory organs
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Development of breasts
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Appearance of pubic hair
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Increase in fat beneath the skin
o
Widening and lightening of the pelvis
o
Onset of menses
 Progesterone
• Produced by the corpus luteum
• Production continues until LH diminishes
in the blood
• Helps maintain pregnancy, endometrial
lining
FEMALE REPRODUCTIVE SYSTEM OVERVIEW ANIMATION
Mammary Glands
 Features
•
Present in both sexes, but only function in
females
o
Modified sweat glands
•
Function is to produce milk
•
Stimulated by sex hormones (mostly
estrogens) to increase in size
 Anatomy
•
Areola – central pigmented area
•
Nipple – protruding central area of areola
•
Lobules – internal structures that radiate
around nipple
•
Alveolar glands – clusters of milk producing
glands within lobules
•
Lactiferous ducts – connect alveolar glands
to nipple
Reproduction II - Female Anatomy and Physiology
 Structures of the Female Reproductive System
• Ovaries
• Fallopian Tubes
• Uterus and Vagina
• External Genitalia
 Oogenesis
 Menstrual Cycle
 Female Sex Hormones
 Mammary Glands