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The
Reproductive
System
Riverside City College
Cellular Reproduction - Mitosis
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Review what you know!
Cell division – commonly occurs
1 parent cell forms 2 daughter cells
Daughter cells have same number of
chromosomes as parent; diploid (2n)
Active stages: prophase, metaphase,
anaphase, telophase
2
Cellular Reproduction - Meiosis
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Reduction division; chromosome # reduced
1 parent cell forms 4 daughter cells
Daughter cells have ½ the chromosomes of the
parent; haploid (n); 46 > 23
Occurs in gametes only (sperm,ova)
What is the significance of meiosis?
Ploidy??
3
Cellular Reproduction - Meiosis
4
Cellular Reproduction - Meiosis
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Stages:
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Meiosis I and Meiosis II
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Each has prophase, metaphase, anaphase, telophase
Reduction of chromosomes occurs in meiosis I
 Metaphase I – chromosomes line up in pairs
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Compare to mitosis metaphase
Meiosis II is a “normal” cycle
5
Cellular Reproduction - Meiosis
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Know how mitosis & meiosis are different:
# of cells formed
 Chromosome # of daughter cells
 # of cycles
 “Lining up” of chromosomes in metaphase
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6
Mitosis vs. Meiosis – p. 1030
7
Gametogenesis
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Formation of gametes by meiosis in testes
and ovaries
Spermatogenesis in males
Oogenesis in females
8
Spermatogenesis
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Occurs in seminiferous tubules of testes
70 days to form immature sperm
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From primary spermatocyte
9
Spermatogenesis – p. 1031
•nourish
•inhibin
•ABP
10
Sperm - p. 1032
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Sperm mature (spermiogenesis) in epididymis
11
Sperm
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Life span of 72 hours
Contribute to semen
100 million/ml of semen
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300-500 million per average ejaculate
< 20 million/ml = sterility
Past 50 years:
Decrease of ejaculate by 20%
 Sperm count/ml decreased by 50%
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12
Oogenesis
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Occurs in the ovary
Process begins before birth
Not completed until conception
All of the potential eggs for future are present
at birth
2 million primary oocytes (prophase 1) at birth
 Attrition occurs = 300-400 thousand at puberty
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1 primary oocyte begins to develop each
month post puberty
13
Oogenesis – p. 1044
14
Male Anatomy - testes
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4 cm by 2.5 cm
In scrotum
Outpocketing of abdominal cavity
 2 parts
 Dartos muscle in wall
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Develop in abdominal cavity
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Move into scrotum through inguinal canal
Cryptorchidism – failure to descend
15
Relationships
of the
abdominal
wall and
scrotal
structures
16
Male Anatomy – testes – p. 1020
17
Male Anatomy - testes
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Tunics:
 T. vaginalis – from peritoneum; outer
 T. albuginea – fibrous capsule; inner
 Septa (walls) extend from t.a.
 Septa form compartments =
lobules (300)
 Seminiferous tubules
in lobules
p. 1021
18
Male Anatomy – testes – p. 1021
19
Male Anatomy – epididymis
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Coiled tube – 20 feet
Sperm maturation
Some sperm storage
Head, body tail
p. 1021
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NOTE: sperm move from seminiferous
tubules > rete testis > efferent ductules >
epididymis
20
MALE
HISTOLOGY
21
Male Anatomy – vas deferens
p. 1064
22
Male Anatomy – vas deferens
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Between epididymis and ejaculatory ducts
Passes from epididymis in scrotum through
the inguinal canal
Passes over bladder and down posterior side
Distal end expanded = ampulla
Joins with duct from seminal vesicle =
ejaculatory duct
Sperm stored here
Part of spermatic cord
23
Male Anatomy – spermatic cord
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Composite
structure:
Vas deferens
 Arteries, veins,
nerves
 Cremaster muscle
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24
Male Anatomy – seminal vesicles
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Small pouches
Base of bladder;
anterior to rectum
Joins with vas deferens
Contribute 60% of
semen volume
Fructose and
prostaglandins
25
Male Anatomy – prostate gland
26
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Male Anatomy – prostate
gland
Inferior to bladder
Donut shaped with urethra through center
Contributes 20%-30% of semen volume
Alkaline secretions
Buffers acidic sperm
 Increases sperm motility
 Protects sperm from vaginal acidity
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Contains:
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Citrate, enzymes, PSA
27
Male Anatomy - Cowper’s
glands
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Bulbourethral gl.
2 pea sized
Duct opens to
urethra
Alkaline fluid
28
Male Anatomy - penis
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Root, shaft,
head (glans)
Prepuce
Erectile tissue:
C. cavernosa
 C. spongiosum
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p. 1023
29
Male Physiology - testosterone
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From interstitial cells
Stimulates descent of testes into scrotum, plus...
Regulated by gonadotropins
GnRH > ICSH > testosterone
Testosterone inhibits GnRH
FSH – spermatogenesis (through ABP)
Negative feedback
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+ sperm = + inhibin (sustentacular cells) = (-)
hypothalamus/ant. pituitary = (-) GnRH/FSH
Stimulates growth; inhibits breakdown
Remember relationship to CNS
30
Male Physiology - semen
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Mixture
Transport, protection, nourishment
Contains:
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Sperm
Fructose (sv) - energy
Prostaglandins (sv)– peristalsis, decrease viscosity
Relaxin (t) – a hormone that increases motility
Seminalplasmin (sv?) – antibiotic
Enzymes (p)
pH = 7.2-7.6
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31
Male Physiology
P. 1034
32
Male Physiology – sexual
response

Erection
Corpora cavernosa
 Parasympathetic reflex
 Nitric oxide – vasodilation
 Consider interaction with CNS
 Impotence – ED – erectile dysfunction
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33
Male Physiology – sexual
response
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Ejaculation
Propulsion of semen
 Sympathetic – spinal reflex
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34
Female Anatomy - ovaries
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Produce:
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Held in place by
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ova
estrogen
progesterone
p. 1037
Part of broad ligament (mesovarium)
Ovarian ligament – ovary to uterus
Suspensory ligament – ovary to lateral pelvic wall
Regions
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Cortex – ovarian follicle with ooocytes
Medulla - vessels
35
Female Anatomy - ovaries
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Follicles
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Oocyte surrounded by
 follicle cells (1 layer of cells)
 granulosa cells (2+ layers of cells)
Stages:
p. 1046
 Primordial f. - 1 layer of cells with “resting” oocyte
 Primary f. - 2+ layers of cells with developing oocyte
 Secondary f. – fluid filled spaces
 Cavity = antrum
 Graafian f. – mature f. with secondary oocyte (ready
for ovulation)
 After ovulation f. becomes corpus luteum
 Later – corpus luteum becomes corpus albicans
36
FEMALE
HISTOLOGY
C
M
37
FEMALE HISTOLOGY –
egg and follicle
development
primordial follicle
primary follicle
secondary follicle
Graafian follicle
corpus luteum
corpus albicans
38
FEMALE HISTOLOGY – Graafian follicle
antrum
oocyte
zona pellucida – clear zone
corona radiata
cumulus oophorous
39
Female Anatomy - uterus
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3” x 2”
Parts:
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p. 1037
Wall:
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Body
Fundus
Cervix
Endo-, myo-, peri-, metrium
Ligaments:
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p. 1035
Broad (2) – to walls
Uterosacral (2) – to sacrum
Posterior (1) – to rectum
Anterior (1) – to bladder
Round (2) – to ext. genitalia (similar path to vas deferens
40
Female Anatomy - uterus
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Implantation & development site
Endometrium sloughs off in menstruation
p. 1037
41
Female Anatomy - uterine tubes
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Fallopian tubes, oviducts –
Site of fertilization
Close but not attached to ovary
Parts:
Attached to/in part of
broad ligament
Many cells are ciliated
Open to pelvic cavity
Relationship to ovulation
p. 1037
42
Female Anatomy - vagina
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Anterior to rectum
Posterior to bladder
Extends upward and back
Distension
Rugae – transverse folds
Stratified squamous ep.
Hymen
Intercourse, menstruation,
childbirth
43
Female Anatomy - vulva
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External genitalia
Includes:
p. 1085
Mons pubis
 Labia majora & minora
 Clitoris
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Erectile tissue
 Homologous to penis
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Vestibule
Urogenital triangle
Anal triangle
Vaginal & urethral orifices
 Bartholin’s glands – greater vestibular glands
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Associated area = perineum (anatomical/clinical)
44
Female Physiology - 1
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Hypothalamus secretes GnRH
GnRH stimulates release of:
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FSH
 follicle development
 estrogen production
LH
 maturation of follicles
 Progesterone production
 Ovulation
 Corpus luteum development
45
Female Physiology - 2

Estrogen
 A group including estrone, estriol, estradiol
 Secreted by :
 Follicles
 Corpus luteum
 Adrenal cortex
 General Function:
 Growth of sex organs
 Secondary sexual characteristics
 Function in cycle:
 Enhances follicle growth
 Stimulates endometrial growth
 Increases peristalsis of endometrium makes cervical
mucus thinner and more alkaline
46
Female Physiology - 3
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Progesterone
 Secreted by:
 Corpus luteum
 Placenta
 Functions:
 Prepares endometrium
 Inhibits contractions of uterus and oviducts
 Stimulates changes in vaginal/cervical lining
 Promotes mammary gland development
 Precursor for androgens and estrogens
 Causes slight temperature change
47
Female Physiology - 4
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Monthly maturation/preparation of:
 egg
= ovarian cycle
 Follicular phase – follicle development
 Luteal phase – corpus luteum development
 uterus
= uterine cycle
 Menstrual phase
 Proliferative phase
 Secretory phase
1st day of menses
= 1st day of cycle
 Typical cycle = 28 days
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48
Female Physiology - 5
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Ovarian cycle
 Prepares oocyte for ovulation
 Ovulation typically at day 14
 Ovulation separates phases
 Relationship to hormone changes
–Stages:
•Primordial f. - 1 layer
•Primary f. - 2+ layers
•Secondary f. – antrum
•Graafian f. – mature
• Corpus luteum
49
Female Physiology - 6
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Uterine cycle/menstrual phase:
Typically 5-7 days
 Endometrium sloughed
 FSH is the principal hormone
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50
Female Physiology - 7
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Uterine cycle/Proliferative phase:
 As follicles develop
 Increase in estrogen
 Increased endometrium
 FSH & LH high at end
 caused by estrogen
51
Female Physiology - 8
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Uterine cycle/Secretory phase:
 14 days
 LH stimulates corpus luteum
 CL produces progesterone
 Progesterone:
 Thickens endometrium
 Thickens cervical mucus
 Inhibits LH
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52
Female Physiology - 9
If fertilization:
 CL produces progesterone
 Placenta develops
 Placenta produces:
 HCG
 Progesterone
 CL > corpus albicans
 No fertilization:
 CL degenerates
 Menstruation begins
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53
Female Physiology - 10
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Signs of ovulation:
 Mittleschmerz – pain from ovarian wall
 Slight temperature elevation
 Change in cervical mucus
Menarche – onset
Menopause - cessation
 Ovaries become less responsive to hormones
 Ovaries begin to “degenerate”
 Vaginal lining thins
 Hot flashes – related to hypothalamus
 Breast atrophy
54
Female Physiology - 11
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Birth control pills & female physiology
Method of action:
 Estrogens & progesterone inhibit
FSH/LH
 Pills contain small amounts of
estrogen & “progesterone” =
Hypothalamic/pituitary axis
is“fooled” (inhibited) =
 Decreased FSH/LH production =
 no eggs formed
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55
FERTILIZATION
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Vagina generally hostile to sperm = acidic
Few reach oviduct (hundreds to thousands)
Sperm propel themselves with tail; only 1 fertilizes oocyte
& excludes others (capacitation)
Fertilization forms zygote
Zygote undergoes cleavage
 leads to stages (blastula, gastrula, etc.
Basic embryonic layers formed – endoderm, mesoderm,
ectoderm
Embryo = conception to 8th week
Fetus = 9th week to conception
56
Clinical Terms – Female - P.
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Amenorrhea
Dysmenorrhea
Endometriosis
Gynecology
Hysterectomy
Laparoscopy
Oophorectomy
Ovarian cysts
Salpingitis
57
58
59
60
61
62
Similarities and differences between males
and females, but same goal: new life
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Primary sex organs: gonads
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These produce the gametes (sex cells)
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Testes in males
Ovaries in females
Sperm in males
Ovum (egg) in females
Endocrine function also: secretion of hormones
Accessory sex organs
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Internal glands and ducts
External genitalia
63
Male reproductive system
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Testes (singular testis) or testicles: the gonads
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In embryo, first develop in posterior abdominal wall, then migrate
Internal body temp too hot for viable sperm
Temp cooler in the scrotum because of superficial position
64
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Scrotum (=pouch) has septum dividing it
Each testis is about 2.5cm x 4 cm in size, within scrotum
Dartos and cremaster muscles move testes in response to hot or cold
Serous sac partially encloses each testis: the tunica vaginalis*
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Develops as outpocketing of peritoneal cavity
Just deep to tunica vaginalis is tunica albuginea* - fibrous capsule
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Septal extensions of it divide testis into 250-300 lobules
Each lobule contains 1-4 coiled seminiferous tubules: make sperm
*
*
65
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Just deep to tunica vaginalis is tunica albuginea* - fibrous capsule
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Each lobule contains 1-4 coiled seminiferous tubules*: make sperm
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Septal extensions of it divide testis into 250-300 lobules*
Converge to form straight tube (tubulus rectus), then conveys sperm into rete testis
Sperm leave testis through efferent ductules which enter epididymis*
Blood supply: pampiniform plexus: from L2 not pelvic level, since descended from
abdomen
Pampiniform
plexus
epididymis
*
*
*
*
*
*
*
*
(lateral views)
66
Epididymis is
comma-shaped
Spermatogenesis:
sperm formation
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Cross section of seminiferous tubule
Begins at puberty
400 million sperm/day
For baby not to end up with twice
as many chromosomes as the
parents, the sperm (as well as the
egg) needs to have only half (1n)
the # of chromosomes (1 of each
of the 23)
(2n means 2 of each
chromosome, one from each
parent, totaling 23 pairs = 46
chromosomes)

Three stages:
 Formation of spermatocytes
 Meiosis
 Spermiogenesis
67
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1st stage: formation of
spermatocytes
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Spermatogonia are stem cells
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Cross section of seminiferous tubule
Least differentiated (earliest in
the process)
Lie in basal lamina
Divide continuously by mitosis
(result 2n or diploid): daughter
cells A (remains a stem cell) or B
(goes on)
When start to undergo meiosis
are by definition called
spermatocytes
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2nd stage: meiosis I
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Each primary spermatocytes
(2n) undergoes meiosis I to
become 2 secondary
spermatocytes:
Each secondary spermatocyte
undergoes meiosis II to become
2 spermatids
Therefore 4 total spermatids
from each spermatogonium
3rd stage: spermiogenesis

Spermatids differentiate into
sperm
68
Stage 3: Spermiogenesis: spermatid streamlined to sperm
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Head contains
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Nucleus with chromatid (genetic material)
Acrosome with enzymes for penetrating egg
Midpiece: mitochondria spiraled around the core of the tail
Tail is an elaborate flagellum (allows sperm to swim)
69
know
these
parts
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Sperm can swim only after they have left the testis
Process of spermatogenesis is controlled by two
hormones
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FSH (follicle stimulating hormones) from anterior pituitary
Testosterone
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Sperm surrounded by Sertoli* (sustenacular) cells:
tight junctions
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primary male hormone
produces by testes
Prevents escape of unique antigens seen as foreign
These would activate the immune system
Autoimmune response would cause sterility
Other functions as well
Interstitial or Leydig cells: secrete androgens
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Male sex hormones
Main one is testosterone
Into blood, sustain all male sex characteristic and sex organs
70
*
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Sperm leave testis though efferent ductules
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Lined by simple columnar epithelium
Cilia and smooth muscle in wall help move sperm along
Sperm mature in epididymus (20 days)
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Head of epididymus contains the efferent ductules which empty into duct
of the epididymus
Sperm gain ability to swim
Sperm can be stored in epididymus for several months
(reabsorbs fluid)
Duct of epididymis: highly
coiled 6m long duct (pic left
is multiple coils of same duct)
*Note pseudostratified columnar
epithelium
*
Ductus (vas)
deferens:
note thick layers of
smooth muscle
71

Sperm are ejaculated from the epididymus
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Not directly from the testes
Vas deferens* (or ductus deferens) 45cm (18”)
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Stores and transports sperm during ejaculation
Runs superiorly from scrotum within spermatic cord, through inguinal
canal and enters pelvis
Histo: see previous slide
•Vas* arches medially
*
72
over ureter
•Descends along
posterior wall of
bladder
•Ends in ampulla
which joins duct of
seminal vesicle to
form short
ejaculatory duct
•Each ejaculatory
duct runs within
prostate where
empties into prostatic
urethra
Inguinal hernia
Spermatic cord:
• Vas deference is the largest
component
• Is a tube of fascia also
containing nerves and
vessels
• Runs in inguinal canal
Inguinal canal has 2 rings:
1. Superficial (medial)
2. Deep
73
Posterior view
Lateral view
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Seminal vesicles
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Sperm and seminal fluid mix in
ejaculatory duct
Prostate: note here and next slide
Bulbourethral glands

74
On posterior bladder
Secrete fluids and substances which
constitute 60% of semen
Their ducts join vas deferens
Secrete mucus during sexual
excitement and ejaculation (lubricant)
The Prostate
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Size & shape of a chestnut
Encircles 1st part of urethra
3 types of glands
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Contribute to semen (milky fluid
and enzymes)
PSA measured as indicator of
prostate cancer (“prostate specific
antigen”)
Fibro muscular stroma
75
Posterior view
Male external genitalia
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Scrotum
Penis
Penis: 3 parts
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Root (attached)
Free shaft or body
Enlarged tip called glans penis
Skin of penis is loose
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Prepuce or foreskin

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Cuff around glans
Removed if circumcision
See cross section, penis

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Urethra (called spongy or penile urethra here)
3 erectile bodies (parasympathetic stimulation
during sexual excitation causes engorgement
with blood allowing erection):
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Corpus spongiosum
Pair of corpora cavernosa
Vessels and nerves
Ejaculation caused by sympathetic nerves
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76
Contraction of smooth muscle of ducts and
penis
Review pics
77
The Female Reproductive System
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Production of gametes (ova, or eggs)
Preparation for support of developing embryo
during pregnancy
Cyclic changes: menstrual cycle
Averages 28 days
 Complex interplay between hormones and organs: at
level of brain, ovaries and uterus

78
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Gonads: the ovaries
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Paired, almond-shaped,
flanking the uterus in lateral
wall of true pelvis
3 x 1.5 x 1 cm in size
79
Posterior view
Anterior view
Ovaries are
retroperitoneal,
but surrounded by
peritoneal cavity
Held in place by
mesentery and
ligaments:
•Broad ligament
•Suspensory
ligament of the
ovary
•Ovarian ligament
Innervation:
•Sympathetic and
parasympathetic
80
Structure of ovary
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Fibrous capsule is called tunica albuginea
Outer cortex houses developing gametes the oocytes,
within follicles
Inner medulla is loose connective tissue with largest vessels
and nerves
81
The Ovarian Cycle
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Follicular phase
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Ovulation
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1st approx. 14 days but variable
Egg develops in a follicle
Stimulated by FSH (see next slide)
Estrogen produced
Egg released from follicle (LH
surge)
Egg in abdominal cavity
Picked up by fimbria of fallopian
tube
Not necessarily halfway point
Luteal phase
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Postovulatory phase 14 days (more
constant)
Corpus luteum develops from
exploded follicle
Produces progesterone as well as
estrogen
 Progesterone stimulates uterus
to be ready for baby
If no pregnancy, corpus luteum
degenerates into corpus albicans
82
Nearly mature follicle

Oocyte develops the zona pellucida
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Glycoprotein coat
Protective shell (egg shell)
Sperm must penetrate to fertilize the oocyte
Thecal cells stimulated by LH to secrete androgens
Granulosa cells (with FSH influence) convert androgens to estrogen
(follicular cells called Granulosa cells now)
Clear liquid gathers to form fluid-filled antrum: now a secondary
follicle
Surrounding coat of Granulosa cells: corona radiata
Fully mature, ready to ovulate, called: ”Graafian follicle”
83
Ovulation
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Signal for ovulation is
LH surge
Ovarian wall ruptures
and egg released,
surrounded by its corona
radiata
84
Oogenesis
Generation of eggs

Starts in fetal period



6-12 primordial oocytes each
cycle selected to develop for
ovulation (most die)




Only then is meiosis I
completed
Secondary oocyte is then
arrested in meiosis II
Meiosis II not completed (now
an ovum) unless sperm
penetrates its plasma membrane
Of the 4 daughter cells, only one
becomes ovum (needs a lot of
cytoplasm)

85
No more oocytes made after
about 7th month
Developed only to early stage
of meiosis I by birth and stops
(called primary oocyte)
The other 3 become “polar
bodies”
Fallopian (uterine) tubes, AKA oviducts
Fimbriae (fingers) pick up
egg
____Fallopian tubes__
Fimbriae
*
Beating cilia and muscular
peristalsis propel egg to
uterus
Empties into superior
part of uterus*
Enlargement of
mucosa layer showing
ciliated columnar
epithelium
Cross section
through entire
tube
PID
86
The Uterus (womb)


In pelvis anterior to rectum and posterosuperior to bladder
Hollow, thick-walled organ



Receives
Retains
Nourishes fertilized egg=embryo
87
Uterus is pear-shaped
(before babies)
Usually anteverted, can
be retroverted
Parts of uterus:
Body (major part)
Fundus
Isthmus
Cervix
Cavity of uterus
small (except in
pregnancy)
Cervical canal
•Internal os
•External os
Vagina
Cervix
•Tough, fibrous ring
•Inferior tip projects
into vagina
•Produces mucus
88
The Uterine Wall*

Three basic layers



Perimetrium: outer serous membrane
Myometrium: middle muscle
Endometrium: inner mucosal lining
Uterine
supports:
•Mesometrium
(largest division
of broad lig) –
main support
•Cardinal
ligament
•Round ligament
(Prolapse)
*
89
Endometrium (inner mucosal lining of uterine cavity)


Simple columnar epithelium containing secretory and
ciliated cells
Note:
Lamina propria of connective tissue
Uterine glands
Uterine arteries
2 main layers (Strata)
1. Functionalis (functional layer)
2. Basalis (basal layer)
(shed if no implantation of
baby)
(not shed)
90
Time: one cycle (approx 28 d.)
ovulation
*

Pituitary hormones
FSH: follicle stimulating
hormone
 LH: luteinizing hormone

Follicular phase
Luteal phase

Ovarian hormones
Estrogen
 Progesterone

91
The cyclic changes of uterine wall and follicle
(hormone graphs should be above)
If no baby, decreasing
progesterone - slough
Proliferative phase:
rebuilds itself after
slough
Secretory phase: vascular rich
glands enlarge: will sustain baby
(needs progesterone: corpus
luteum initially then placenta)
92
(inhibin: inhibits pituitary
secretion of FSH)
93
The
Vagina






Thin-walled tube
Inferior to
uterus
Anterior to
rectum
Posterior to
urethra &
bladder
“Birth canal”
Highly
distensible wall:
3 layers



Adventitia
Muscularis
mucosa
94
External female genitalia aka vulva or pudendum




Mons pubis: fatty pad over pubic symphysis, with hair after puberty
Labia (lips) majora: long fatty hair-covered skin folds
Labia minora: thin, hairless, folds enclosing vestibule
Vestibule: houses external openings of urethra and vagina




Urethra is anterior (drains urine from bladder)
Baby comes out through vagina (vaginal orifice in pic)
Clitoris: anterior, homolog of penis (sensitive erectile tissue)
Perineum: diamond shaped region
95
Mammary glands (breasts)







Modified sweat glands
Both sexes but function (normally) only in lactating female
Produce milk to nourish baby
Respond to hormonal stimulation
Lymph drains into parasternal and axillary lymph nodes
Nipple surrounded by pigmented ring of skin, the areola
Muscles underneath: pectoralis major and minor, parts of serratus anterior and external
oblique
96




Mammary glands consist of 15-25 lobes
Each a distinct compound alveolar gland opening at the nipple
Separated by adipose and suspensory ligaments
Smaller lobules composed of tiny alveoli or acini




Like bunches of grapes
Walls: simple cuboidal epithelium of milk-secreting cells
Don’t develop until half-way through pregnancy (ducts grow during puberty)
Milk passes from alveoli through progressively larger ducts

Largest: lactiferous ducts, collect milk into sinuses
97
Conception

After ejaculation into the vagina, sperm swim to meet an egg



Sperm live 5-7 days (need cervical mucus)
Eggs live about 12-24 hours, so conception only occurs during this short window
Fertilization occurs in the fallopian tube
Events leading to fertilization:
•Sperm binds to receptors on
zona pellucida
•Acrosomal reaction – enzymes
digest a slit
•Sperm passes through zona
•Fusion of a single sperm’s
plasma membrane with oocyte’s
plasma membrane
•Cortical reaction: sperm
receptors destroyed in zona so no
more enter; sperm nucleus
engulfed by egg’s cytoplasm
Fertilization occurs at
the moment the
chromosomes from the
male and female
gametes unite
98
Initial days


Cleavage (cell division)
Blastocyst stage by day 4: now in uterus
99
Implantation
Blastocyst floats for 2
days: “hatches” by
digesting zona enough
to squeeze out
6-9 days post
conception burrows into
endometrium
100
Formation of Placenta
Both contribute:
•Trophoblast from embryo
•Endometrial tissue from mother
Not called placenta until 4th month
Embryonic
blood circulates
within chorionic
villi, close to but
not mixing with
mother’s blood
•Nutrients
to baby
•Wastes to
mom
101
The “Placental Barrier”



Sugars, fats and oxygen diffuse from mother’s blood to fetus
Urea and CO2 diffuse from fetus to mother
Maternal antibodies actively transported across placenta





Some resistance to disease (passive immunity)
Most bacteria are blocked
Many viruses can pass including rubella, chickenpox, mono,
sometimes HIV
Many drugs and toxins pass including alcohol, heroin, mercury
Placental secretion of hormones


Progesterone and HCG (human chorionic gonadotropin, the hormone
tested for pregnancy): maintain the uterus
Estrogens and CRH (corticotropin releasing hormone): promote labor
102
Childbirth

Gestational period: averages 266 days
(this is time post conception; 280 days post LMP)

Parturition: the act of giving birth: 3 stages of labor
1.
2.
3.
Dilation: 6-12h (or more in first child); begins with regular uterine
contractions and ends with full dilation of cervix (10cm)
Expulsion: full dilation to delivery – minutes up to 2 hours
Placental delivery: 15 minutes
Dilation of cervis; head enters true pelvis
Expulsion: head first safest as is largest part
Delivery of the placenta
Late dilation with head rotation to AP position
103
Stages of Life

Embryologically, males and females start out “sexually
indifferent”



Gonads, ducts and externally identical structures
At 5 weeks gestation changes start to take place
Puberty: reproductive organs grow to adult size and
reproduction becomes possible


Between 10 and 15
Influence of rising levels of gonadal hormones



Testosterone in males
Estrogen in females
Female menopause (between 46 and 54):

Loss of ovulation and fertility
104