Transcript Human Anatomy, First Edition McKinley&O'Loughlin

Human Anatomy,
First Edition
McKinley & O'Loughlin
Chapter 28 :
The Reproductive
System
28-1
Reproductive Systems


Main function: propagation of the
species
To achieve this goal:



Must ensure sexual maturation
Produce gametes (n).
Male and female structures are
homologues:

derived from common developmental
tissues
28-2
28-3
Homologous structures
28-4
Comparison of the Female and
Male Reproductive Systems


Primary sex organs called gonads.
 ovaries in females
 testes in males
Produce gametes which unite to form a new individual.
oocytes
 sperm
Gonads produce large amounts of sex hormones which affect
maturation, development, and changes in the activity of the
reproductive system organs.
 estrogen and progesterone in the female
 androgens (esp. testosterone) in the male


28-5
Comparison of the Female and
Male Reproductive Systems

Both have accessory reproductive organs

duct systems




carry gametes away from the gonads
toward the site of fertilization in females
to the outside of the body in males
Fertilization occurs when male and female
gametes meet:


copulation, coitus, sexual intercourse
Restores the diploid number (2n)
28-6
Comparison of the Female and
Male Reproductive Systems


Primarily nonfunctional and “dormant” until
puberty.
At puberty, external sex characteristics
become more prominent.







breast enlargement in females
fat distribution patterns in both sexes
pubic hair in both sexes
reproductive organs become fully functional
gametes mature
gonads secrete sex hormones
Both reproductive systems produce gametes.
28-7
Comparison of the Female and
Male Reproductive Systems

Puberty:

Initiated by hypothalamus


Stimulates release of FSH and LH


Secretes GnRH (gonadotropin-releasing
hormone
Prior to puberty, not present
Stimulate gonads to produce:
Sex hormones
 gametes

28-8
Comparison of the Female and
Male Reproductive Systems


Female typically produces and releases
a single oocyte monthly.
Male produces 100,000,000’s of (sperm)
daily.
 male gametes are stored for a short
time
 if they are not expelled from the body
within that period, they are resorbed
28-9
10
Perineum


Diamond-shaped area between the thighs that is circumscribed
anteriorly by the pubic symphysis, laterally by the ischial
tuberosities, and posteriorly by the coccyx.
2 distinct triangle bases


Anterior triangle, or urogenital triangle



formed by an imaginary horizontal line extending between the
ischial tuberosities of the ossa coxae.
contains the urethral and vaginal orifices in females
contains the base of the penis and the scrotum in males.
Posterior triangle, or anal triangle

location of the anus in both sexes.
28-11
12
Anatomy of the Female
Reproductive System



Peritoneum folds around the various pelvic organs and creates
two major dead-end recesses, or pouches.
 anterior vesicouterine pouch forms the space between the
uterus and the urinary bladder
 posterior rectouterine pouch forms the space between the
uterus anteriorly and the rectum posteriorly
Primary sex organs of the female are the ovaries.
Accessory sex organs include





uterine tubes
uterus,
vagina,
clitoris
mammary glands.
28-13
14

Mesovarium:



Broad ligament



Peritonium
Drapes over the uterus
Ovarian ligament


Double folds of peritoneum
Attaches ovaries to broad ligament
Ovary to uterus
Suspensory ligament

Ovary to pelvic wall
28-15
16
17
Ovarian Follicles


Within the cortex are thousands of ovarian
follicles.
Consist of

Follicle cells





granulosa cells
nurse cells that support the oocyte
a type of oocyte.
Several different kinds of ovarian follicles,
each representing a different stage of
development.
Oogenesis:

maturation of a primary oocyte to a secondary
oocyte.
28-18
19
20
Before Birth




The process of oogenesis occurs in a female fetus before birth.
At this time, the ovary contains primordial germ cells called
oogonia, which are diploid cells, meaning they have 23 pairs of
chromosomes.
During the fetal period, the oogonia start the process of
meiosis, but they are stopped at prophase I. At this point,
the cells are called primary oocytes.
At birth, the ovary of a female child is estimated to contain
approximately 1.5 to 2 million primordial follicles within its
cortex.
The primary oocytes in the primordial follicles remain arrested in
prophase I until after puberty.
28-21
From Puberty to Menopause






During childhood ovaries are inactive, and no follicles develop.
Atresia occurs, in which some primordial follicles regress or
break down.
By the time she reaches puberty only about 400,000 primordial
follicles remain.
At puberty, the hypothalamus releases GnRH (gonadotropinreleasing hormone), which stimulates the anterior pituitary to
release FSH (follicle-stimulating hormone) and LH (luteinizing
hormone).
The levels of FSH and LH vary in a cyclical pattern and produce
a monthly ovarian cycle.
The three phases of the ovarian cycle: are the follicular phase,
ovulation, and the luteal phase.
28-22
The Three Phases of the Ovarian Cycle


Follicular phase occupies days 1–13 of an approximate 28-day
ovarian cycle.
Ovulation occurs on day 14 of a 28-day ovarian cycle and is defined
as the release of the secondary oocyte from a vesicular follicle.


only one ovary ovulates each month
Luteal phase occurs during days 15–28 when the remaining follicle
cells in the ruptured vesicular follicle turn into a corpus luteum.

secretes progesterone and estrogen that stabilize and build up the
uterine lining, and prepare for possible implantation of a fertilized
oocyte

has a life span of about 10–13 days if the secondary oocyte is not
fertilized

it regresses and becomes a corpus albicans

the uterine lining to be shed as menstruation

menarche
28-23
24
After Menopause

The time when a woman is nearing menopause is called
perimenopause.



estrogen levels begin to drop, and
a woman may experience irregular periods, skip some periods, or
have very light periods
When a woman has stopped having monthly menstrual
cycles for 1 year and is not pregnant, she is said to be in
menopause.



The age at onset typically is between 45 and 55 years
follicles stop maturing, and significant amounts of estrogen and
progesterone are no longer being secreted
a woman’s endometrial lining does not grow, and she no longer has
a menstrual period
28-25
26
27
28
Uterine Tubes




The uterine tubes, also called the fallopian tubes or oviducts,
extend laterally from both sides of the uterus toward the
ovaries.
In these tubes, the secondary oocyte is fertilized, and the preembryo begins to develop as it travels toward the uterus.
Usually it takes the pre-embryo about 5 to 6 days to reach the
lumen of the uterus.
Parts: lined with mucosa (simple ciliated columnar ep),
muscularis, serosa




Infundibulum
Ampulla
Isthmus
Interstitial segment
28-29
The Uterus Serves Four
Functions

Site for implantation.
pre-embryo implants into the inner uterine wall and
becomes connected to the uterine lining
Supports, protects, and nourishes the developing embryo/fetus
 forms a vascular connection with the mother’s uterine wall
that later develops into the placenta
Ejects the fetus at birth after maternal oxytocin levels increase
to initiate the uterine contractions of labor.
Site for menstruation.
 if an oocyte is not fertilized or after a baby is expelled, the
muscular wall of the uterus contracts and sheds its inner
lining as menstruation




28-30
Regions of the Uterus




Fundus
Body
Isthmus
Cervix



Cervical canal
Internal os
External os
28-31
Support of the Uterus

Pelvic floor muscles



Round ligaments



Lateral uterus, through inguinal canal, to labia
majora
Maintain anteverted position
Transverse cervical ligaments


Pelvic diaphragm
Urogenital diaphragm
Lateral cervix and vagina to pelvic wall
Uterosacral ligaments

Inferior uterus to sacrum
28-32
Wall of the Uterus



Composed of three concentric tunics:
 Perimetrium
 Myometrium
 Endometrium
The outer tunic of most of the uterus is a serosa called the
perimetrium.
 continuous with the broad ligament
The myometrium is the thick, middle tunic of the uterine wall
formed from three intertwining layers of smooth muscle.
 in the nonpregnant uterus, the muscle cells are less than
0.25 millimeters in length
 during the course of a pregnancy, smooth muscle cells
increase both in size and in number
28-33
Uterine (Menstrual) Cycle and
Menstruation





The menstrual phase occurs approximately during days 1–5
of the cycle. This phase is marked by sloughing of the functional
layer and lasts through the period of menstrual bleeding.
The proliferative phase follows, spanning approximately days
6–14. The initial development of the functional layer of the
endometrium overlaps the time of follicle growth and estrogen
secretion.
The last phase is the secretory phase, which occurs at
approximately days 15–28. During the secretary phase,
increased progesterone secretion from the corpus luteum results
in increased vascularization and development of uterine glands.
If the oocyte is not fertilized, the corpus luteum degenerates,
and the progesterone level drops dramatically.
Without progesterone, the functional layer lining sloughs off,
and the next menstrual phase begins.
28-34
Vagina

The vagina is




The vagina connects the uterus with the outside of the body
anteroventrally





thick-walled, fibromuscular tube
forms the inferior-most region of the female reproductive tract
measures about 10 centimeters in length in an adult female.
functions as the birth canal.
Also the copulatory organ of the female
Serves as the passageway for menstruation.
The vaginal wall is heavily invested with both blood vessels and
lymphatic vessels.
The vagina’s relatively thin, distensible wall consists of three
tunics:

an inner mucosa, a middle muscularis, and an outer adventitia
28-35
External Genitalia


The external sex organs of the female, are collectively called the
vulva.
The mons pubis is an expanse of skin and subcutaneous
connective tissue immediately anterior to the pubic symphysis.
 covered with pubic hair in postpubescent females
 labia majora
 labia minora




Contain the vestibule
Urethral orifice
Vaginal oriface
Clitoris located at the anterior regions of the
labia minora


glans
prepuce−an external fold of the labia minora that
forms a hoodlike covering over the clitoris.
28-36
37
Mammary Glands






Each mammary gland, or breast, is located within the anterior thoracic
wall and is composed of a compound tubuloalveolar exocrine gland.
Breast milk contains proteins, fats, and a sugar to provide nutrition to
infants.
The nipple is a cylindrical projection on the center of the breast. It
contains multiple tiny openings of the excretory ducts that produce
breast milk.
The areola is the pigmented rosy or brownish ring of skin around the
nipple. Its surface often appears uneven and grainy due to the
numerous sebaceous glands immediately internal to the surface.
The color of the areola may vary, depending upon whether or not a
woman has given birth. In a nulliparous woman (a woman who has
never given birth), the areola is rosy or light brown in color.
In a parous woman (a woman who has given birth), the areola may
change to a darker rose or brown color.
28-38
39
40
Anatomy of the Male
Reproductive System


Primary organs: gonads are the testes
Accessory sex organs include:
 a complex set of ducts and tubules leading from the testes
to the penis
 a group of male accessory glands
 the penis, which is the organ of copulation
28-41
42
Scrotum


Skin covered sac
Raphe: external midline seam


Continues on inferior surface of the penis, and to anus.
Components of scrotal wall.







Skin
Fascia
Dartos muscle
External spermatic fascia
Cremaster muscle
Internal spermatic fascia
Tunica vaginalis.

28-43
Scrotum

Male gametes are sensitive to elevated temperatures


often exhibit abnormal or completely curtailed development
Gamete development occurs outside the body

Scrotum: a skin-covered sac that houses:


male gonads
first portion of the duct system


Testes exposed to elevated temperatures

Skin of the scrotal sac becomes thin



result of dartos muscle relaxation.
The cremaster muscle relaxes


site of early sperm maturation and development, reside outside the body
proper.
allows the testes to move inferiorly away from the body
The testes temperature becomes less than normal body
temperature.
The opposite occurs if the testes are exposed to cold.
28-44
45
46
Testes



Small, oval organ
Housed in the scrotum
Produces:



Sperm
androgens.
Coverings

Serous membrane called tunica vaginalis



Parietal layer
Visceral layer.
Tunica albuginea


Forms internal septa
250 lobules per testis


Each lobule has up to 4 seminiferous tubules

Two types of cell

Sustentacular cells

Germ cells
Interior is called mediastinum testis.
28-47
48
Testes

Blood-testis barrier



Tight junctions between sustentacular cells
Spern develop in the semineferous tubules
Interstitial spaces: surround the seminiferous tubules.

Contain interstitial (Leydig) cells


produce hormones called androgens.
Several types of androgens



most common one is testosterone.
the adrenal cortex secretes a small amount of androgens
the vast majority of androgen release is via interstitial cells in the
testis


beginning at puberty.
These hormones cause males to develop the classic characteristics:



axillary and pubic hair
deeper voice
sperm production.
28-49
50
Testes

Series of tubes:






Seminiferous
tubules
Straight ducts
Rete testis
Efferent ductule
Epididymis
Ductus deferens
28-51
Spermatic Cord



The blood vessels and nerves to the testis
travel from within the abdomen to the
scrotum in a multilayered structure called the
spermatic cord.
Layers
Contain



Testicular artery
Pampiniform plexus
Autonomic nerves
28-52
Developmemt of sperm



Called spermatogenesis
Occurs in the seminiferous tubules
Process:





Spermatogonium
Primary spermatocyte
Secondary spermatocyte
Spermatid
Spermiogenesis

Spermatid matures into spermatozoon
28-53
54
55
Epididymis






The epididymis is a comma-shaped structure composed of an
internal duct and an external covering of connective tissue.
Its head lies on the superior surface of the testis, while the body
and tail are posterior to the testis.
Internally, the epididymis contains a long, convoluted duct of
the epididymis, which is approximately 4 to 5 meters in length.
Sperm must reside in the epididymis for a period of time to
become mature and fully motile.
If they are expelled too soon, they lack the motility necessary to
travel through the female reproductive tract and fertilize an
oocyte.
If sperm are not ejected from the male reproductive system in a
timely manner, the old sperm degenerate in the epididymis.
28-56
Ductus Deferens



When sperm leave the epididymis, they enter the ductus
deferens, also called the vas deferens.
The ductus deferens is a thick-walled tube that travels within
the spermatic cord, through the inguinal canal, and within the
pelvic cavity before it reaches the prostate gland.
The ampulla of the ductus deferens unites with the proximal
region of the seminal vesicle to form the terminal portion of the
reproductive duct system, called the ejaculatory duct.
28-57
Urethra



Transports semen from the ejaculatory duct to the outside of
the body.
Subdivided into:
 prostatic urethra that extends through the prostate gland
 membranous urethra that travels through the urogenital
diaphragm
 penile urethra that ends through the penis
Sperm leave the body through the urethra.
28-58
Accessory Glands




The vagina has a highly acidic environment to prevent bacterial
growth.
Sperm cannot survive in this type of environment, so an alkaline
secretion called seminal fluid is needed to lessen the acidity of
the vagina and bring pH values closer to neutral.
As the sperm travel through the reproductive tract (a process
that can take several days), they are nourished by nutrients
within the seminal fluid.
The components of seminal fluid are produced by accessory
glands:
 seminal vesicles
 prostate gland
 bulbourethral glands
28-59
Seminal Vesicles





The paired seminal vesicles are located on the posterior surface
of the urinary bladder adjacent to the ampulla of the ductus
deferens.
Each seminal vesicle is an elongated, pouchlike hollow organ
approximately 5–8 centimeters long.
It is the proximal portion of each seminal vesicle that merges
with a ductus deferens to form the ejaculatory duct.
The seminal vesicles secrete a viscous, whitish-yellow alkaline
fluid containing both fructose and prostaglandins.
The fructose is a sugar that nourishes the sperm as they travel
through the female reproductive tract, while the prostaglandins
promote the widening and slight dilation of the external os of
the cervix.
28-60
Prostate Gland



A compact encapsulated organ that weighs about 20 grams and
is shaped like a walnut, measuring approximately 2 cm by 3 cm
by 4 cm.
Located immediately inferior to the bladder.
Secretes a slightly milky fluid that is weakly acidic and rich in
citric acid, seminalplasmin, and prostate-specific antigen (PSA).
 citric acid is a nutrient for sperm health
 seminalplasmin is an antibiotic that combats urinary tract
infections
 PSA acts as an enzyme to help liquefy semen following
ejaculation
28-61
Bulbourethral Glands



Paired, pea-shaped
Also called Cowper’s glands
Location:



Each gland has a short duct



within the urogenital diaphragm
on each side of the membranous urethra.
projects into the base of the penis
enters the spongy urethra.
secretory product

clear, viscous mucin (forms mucus when mixed with water).


mucin protects the urethra
serves as a lubricant during sexual intercourse.
28-62
63
64
65
Semen


Combination of seminal fluid from the
accessory glands and sperm.
Called the ejaculate (when released during
ejaculation)



Average transit time: about 2 weeks


normally about 3 to 5 milliliters
contains approximately 200 to 500 million
spermatozoa.
from release of sperm into the lumen of the
seminiferous tubules, passage through the duct
system, and appearance in the ejaculate.
Sperm count can vary, spemen amount
usually remains the same.
28-66
67
68
Aging and the Reproductive
Systems






Our reproductive systems are basically nonfunctional for several
years following birth. When we reach puberty, hormonal
changes in the hypothalamus and anterior pituitary gland
stimulate the gonads to begin producing sex hormones.
Thereafter, changes occur in many body structures, the
reproductive organs mature, and gonads begin to produce
gametes.
Gametes stop maturing in females in their 40s or 50s, and
menopause occurs.
A reduction in hormone production that accompanies
menopause causes some atrophy of the reproductive organs
and the breasts.
The vaginal wall thickness decreases, as do glandular secretions
for maintaining a lubricated and moist lining.
The uterus shrinks and atrophies, becoming much smaller than
it was before puberty.
28-69
70
71
72
73
74