Chapter 28 The Reproductive System Lecture Outline
Gonads
Gametes = sex cells = ovum & sperm
Haploid (N): 23 chromosomes
Somatic cells
Diploid (2N): 46 chromosomes
Homologus chromosomes: 23 pair
Ovum (N) + Sperm (N) = Zygote (2N)
Gametogenesis
Mitosis: 2N → 2N (Somatic cells)
Duplicate chromosomes → sister chromatids
Sister chromatids separate
Meiosis: 2N → 1N (Sex cells)
Duplicate chromosomes → sister chromatids
Synapsis of homologus chromosomes
Tetrad → crossing over
Meiosis I: 2N → 1N
Homologus chromosomes separate
Meiosis II: 1N → 1N
Sister chromatids separate
Male Reproductive System
1. Scrotum
Raphae
Dartos muscle
Smooth muscle
Cremaster muscle
Internal oblique
2. Testes (Gonads)
Functions:
A. Gametes: sperm
B. Sex hormones: androgens (testosterone)
C. Inhibin
Development:
Descent
Inguinal canal
Cryptorchidism
Inguinal hernia
Structure:
Tunica vaginalis (peritoneum)
Tunica albuginea (capsule)
Lobules
Seminiferous tubules
Rete testis
Efferent ductules
Epididymis
Ductus / Vas deference
Spermatic cords
Vasectomy
Functional regions:
A. Interstitial cells
Androgens
B. Seminiferous tubules
Spermatogonia → Spermatozoa
Sustentacular cells
Spermatogenesis (64-72 days)
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1. Mitosis
A. Spermatogonium
B. Primary spermatocyte
2. Meiosis
Meiosis I
Primary spermatocyte →
Secondary spermatocyte
Meiosis II
Secondary spermatocyte →
Spermatids
3. Spermiogenesis
Spermatid → Spermatozoa / Sperm
Flagella
Compact chromosomes
Shed cytoplasm
Sperm / Spermatozoa
A. Head (genetic part)
DNA
Acrosome
Hydrolytic enzymes
B. Midpiece (metabolic part)
Mitochondria
C. Tail (locomoter region)
Flagellum
Sustentacular cell function:
1. blood-testis barrier
tight junctions
2. support cell division
3. support spermiogenesis
4. inhibin
block FSH & GnRH
5. Androgen binding protein (ABP)
6. Mullerian inhibiting factor
block uterus & uterine tubes
3. Reproductive tract
A. Epididymis
1. monitor / adjust testicular fluid
2. recycle spermatozoa
3. protect, store, facilitate maturation
B. Ductus deferens
Inguinal canal
Ampulla
Seminal vesicles & prostate gland
Ejaculatory duct
Urethra
C. Urethra (shared: urinary & reproductive)
1. Prostatic urethra
Prostate gland
2. Membranous urethra
Urogenital diaphragm
3. Spongy / Penile urethra
External urethral orifice
4. Accessory glands
Semen = sperm + gland secretions
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SCCC BIO132 Chapter 28 Handout
A. Seminal vesicles
Seminal fluid
1. fructose
2. prostaglandins
3. fibrinogen
4. vesiculase
5. alkaline buffers
B. Prostate gland
Prostatic fluid
1. enzymes
2. fibrinolysin
3. seminal plasmin
C. Bulbourethral glands
Urogenital diaphragm
Alkaline mucus
Semen: 2-5ml / ejaculation
60% seminal fluid
30% prostatic fluid
10% testicular fluid + spermatozoa
50-130 million sperm / mL
< 60 million total = sterile
5. External genitalia
A. Scrotum
B. Penis
1. Root
2. Shaft
3. Glans
Prepuce
Preputial glands
Smegma
Circumcision
Erectile tissue
1. Corpora cavernosa
2. Corpus spongiosum
urethra
glans
Male sexual function
1. Erection
Parsympathetic
NO
arteriole dilation
Bulbourethral glands
2. Ejaculation
Sympathetic
Spinal Reflex
3. Detumescence
Sympathetic
arteriole constriction
Latent period
Impotence
Hormones and male reproductive function
1. GnRH (60-90min) → FSH, LH
2. FSH → Sustentacular cells:
-spermatogenesis
-ABP
-inhibin
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block FSH, LH, GnRH
3. LH → Interstital cells
-androgens
4. Testosterone effects
-spermatogenesis
-libido
-metabolism
-sex characteristics
-accessory organ function
-negative feedback
Male age related changes
-male climacteric: ↓ testosterone
-benign prostatic hypertrophy
-impotence
-↓ sperm motility
Female reproductive system
1. Ovaries (gonads)
Functions:
A. Gametes: ova
B. Sex hormones
Estrogen
Progesterone
C. Inhibin
Structure:
Germinal epithelium (peritoneum)
Tunica albuginea (capsule)
Cortex
Ovarian follicles
1. Oocyte
2. Follicle cells / Granulosa cells
Medulla
vessels & nerves
Oogenesis
Fetus
Primary oocyte in primodial follicle
Puberty - Menopause
Primary oocyte → secondary oocyte
Polar body
Ovulation
Secondary oocyte in Meiosis II
Fertilization
Ovum (completes meiosis)
Ovarian cycle
1. Follicular phase
A. Formation of 1° follicle (day 1-8)
Primordial → Primary
Granulosa cells
Zona pellucida
Thecal cells
Estrogens
B. Formation of 2° follicle (day 8-10)
Primary → Secondary
Follicular fluid
Antrum
C. Formation of 3° follicle (day 10-14)
Secondary → Tertiary
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SCCC BIO132 Chapter 28 Handout
Corona radiata
1° oocyte → 2° oocyte +polar body
2. Ovulation (day 14)
3. Luteal phase
Corpus luteum
Progesterone & estrogens
Corpus albicans
Birth: 2 million primordial follicles
Puberty: 200,000
500 ovulated
2. Uterine tubes
Cilia
A. Infundibulum
Fimbriae
B. Ampulla
Fertilization
C. Isthmus
Ectopic pregnacy
Pelvic inflammatory disease
Neisseria gonorrhoeae
Chlamydia species
3. Uterus
Structure:
A. Body
1. Perimetrium (peritoneum)
2. Myometrium
Smooth muscle
3. Endometrium
Simple columanr epithelium
Lamina propria
Endometrial glands
a. Functional zone
b. Basilar zone
B. Cervix
Cervical canal
External os
Cervical glands
Mucus
Prolapse of the uterus
Uterine cycle
1. Mensus (day 1-5)
Menstruation
Functional zone
Necrosis
2. Proliferative phase (day 6-14)
Basilar zone
3. Secretory phase (day 15-28)
Endometrial glands
Glycogen
Endometriosis
Menache
Menopause
Amenorrhea
4. Vagina
A. Adventitia
B. Muscularis
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C. Mucosa
Stratified squamous epithelium
Rugae
Glycogen
Lactic acid
5. External genitalia
Vulva
A. Mons pubis
B. Labia majora
C. Labia minora
D. Vestibule
Urethral orifice
Vaginal orifice
Greater vestibular glands
E. Clitoris
Prepuce
6. Mammary glands
Function:
Lactation
Structure:
Areola
Nipple
Lobe
Lobule
Alveoli
Lactiferous duct
Lactiferous sinus
Hormones and female reproductive cycle
1. Follicular phase
↑ GnRH → ↑FSH & LH
LH → Thecal cells
Androstenedione
FSH → Granulosa cells
Estrogen
↑ Estrogen:
-↑ follicle growth
-new functional layer
progesterone recpetors
-block FSH & LH release
-↑ Inhibin
block FSH
2. Ovulation
Max estrogen:
-LH surge
-thin cervical mucus
LH surge:
-1° oocyte → 2° oocyte
-ovulation
-corpus luteum formation
3. Luteal phase
Corpus luteum:
Progesterone, Estrogen, Inhibin
↑ Progesterone:
-uterine secretion
-thick cervical mucus
Block LH, FSH, GnRH
SCCC BIO132 Chapter 28 Handout
↓ LH:
-Corpus luteum → corpus albicans
↓ Progesterone, estrogen, inhibin:
-mensus
-↑ GnRH → ↑FSH & LH
Estrogen effects
-bone & muscle growth
-sex characteristics
-libido
-maintain accessory organs
-grow endometrium
Female sexual function
Parasympathetic
arteriole dilation
???
Female age related changes
Menopause
↓ estrogen & progesterone
↑ GnRH, FSH & LH
-↓ uterus & breast
-osteopenia
-cardiovascular disorders
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SCCC BIO132 Chapter 28 Handout
Male
The Reproductive System
Female
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SCCC BIO132 Chapter 28 Handout
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SCCC BIO132 Chapter 28 Handout
2n (duplicated)
2n
(sister chromatids)
2n
- one 2n cell duplicates its DNA: each duplicated
chromosome consists of two sister chromatids
- sister chromatids are separated equally (now
chromosomes)
- two identical diploid daughter cells result
- process of cell division used by all somatic cells
2n
1n
1n
1n (duplicated)
(sister chromatids)
2n
1n
1n
1n (duplicated)
2n (duplicated)
sister chromatids
- homologus chromosomes undergo synapsis: pair up forming tetrads (four sister
chomatids / 2 duplicated chromosomes)
- homologus chromosomes exchange genes by cross-over
- in Meiosis I homologus chromosomes separate (cells now haploid with
duplicated chromosomes)
- in Meiosis II sister chromatids separate(now chromosomes) producing four
haploid cells, all genetically different
-process of cell division only used for sex cell production
Mitosis 2n(duplicated) cell → two 2n daughter cells Meiosis: 2n(duplicated) cell →four 1n daughter cells, all cells different
- one 2n cell duplicates its DNA: each duplicated chromosome consists of two
all cells are identical
Spermatogenesis = sperm formation
-occurs in seminiferous tubules, aided by sustentacular cells
-begins with stem cells = spermatogoinum: outer most tubule cell, contacts basement membrane
-as cells divide and differentiate they migrate toward lumen of tubule
1. Mitosis (spermatogonium → primary spermatocyte)
-spermatogonia divide producing daughter cells
-daughter cell A remains at basement membrane as a spermatogonium
-daughter cell B differentiates into a primary spermatocyte and moves toward the lumen
2. Meiosis (primary spermatocyte → spermatid)
-the diploid primary spermatocyte undergoes meiosis I to generate two haploid secondary spermatocytes
-the secondary spermatocytes complete meiosis II producing four spermatids
3. Spermiogenesis (spermatid → sperm/spermatozoa)
-the round spermatids differentiate into small, streamlined motile cells at the lumen:
-a long flagellum is formed
-the chromosomes are compacted
-excess cytoplasm (cytosol and organelles) is shed
-complete cellular transformation takes ~5 weeks
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SCCC BIO132 Chapter 28 Handout
Hormones and Male Reproductive Function
1. GnRH is released consistently in 60-90 minutes intervals from the hypothalmus
-this triggers release of FSH and LH from the anterior pituitary
2. FSH targets sustentacular cells to:
-promote spermatogenesis
-promote secretion of androgen binding protein
-as spermatogenesis increases it triggers release of inhibin
-inhibin decreases GnRH and FSH by negative feedback
3. LH targets interstitial cells:
-LH promotes the secretion of androgens (testosterone)
4. Testosterone:
-stimulates spermatogenesis (binds to antigen binding protien)
-promotes sex drive in CNS
-simulates metabolism (especially skeletal muscle growth)
-establishes and maintains male secondary sex characteristics
-maintains accessory organs of the reproductive tract
-as levels increase, testosterone inhibits GnRH release by negative feedback
-the consistent release of GnRH insures that the circulating levels of all the hormones (FSH, LH, and
testosterone) remain relatively constant
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SCCC BIO132 Chapter 28 Handout
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SCCC BIO132 Chapter 28 Handout
- begins prior to birth and ends at menopause
- during fetal development primary oocytes suspended in Meiosis I are
formed in primordial follicles
- from puberty to menopause primary oocytes are activated on a 28 day
cycle (the ovarian cycle) to complete Meiosis I to produce
one large secondary oocyte and one small polar body
- at ovulation the secondary oocyte is released from the ovary suspended in
Meiosis II
- the secondary oocyte will not complete Meiosis to produce a mature ovum
until fertilized by a sperm
Oogenesis = oocyte formation
The Ovarian Cycle (~28 days)
1. Follicular Phase
-period of follicle growth (day 1-14)
A. Formation of Primary Follicles (day 1-8)
-squamous follicular cells of many primordial follicles enlarge into cuboidal cells and begin dividing resulting in
primary follicles
-the follicular cells produce stratified layers: now called granulosa cells
-microvilli from the innermost granulosa cells are connected to the primary oocyte via gap junctions to support
and stimulate the growth of the oocyte
-the granulosa cells secrete glycoproteins which form a thick membrane around the primary oocyte called the
zona pellucida
-cells from the ovarian cortex form a layer of thecal cells around the outside of the primary follicle
-thecal cells and granulosa cells together begin producing estrogens
B. Formation of Secondary Follicles (day 8-10)
-only a few primary follicles continue development to become secondary follicles
-granulosa cells begin to secrete follicular fluid
-the fluid accumulates between the stratified layers of the granulosa cells creating a space called the antrum, this
is now called a secondary follicle
C. Formation of one Tertiary Follicle (day 10-14)
-the primary oocyte becomes restricted to one side of the follicle attached by a stalk and surrounded by a layer of
granulosa cells called the corona radiata
-the antrum continues to expand until the follicle spans the width of the cortex, this is now called a tertiary
follicle
-one tertiary or vesicular follicle usually forms (99% of the time)
-the primary oocyte completes meiosis I forming a secondary oocyte and a small polar body
2. Ovulation (day 14)
-the tertiary follicle ruptures through the ovarian wall releasing the secondary oocyte surrounded by the zona pellucida
and corona radiata into the pelvic cavity
3. Luteal Phase (day 14-28)
-the ruptured tertiary follicle collapses and fills with blood
-the granulosa cells and thecal cells proliferate an reorganize into the corpus luteum
-the corpus luteum secretes progesterone and some estrogens
-if pregnancy does not occur the corpus luteum degenerates and is invaded by fibroblasts
-the fibroblasts create scar tissue called the corpus albicans
-if pregnancy occurs, the corpus luteum remains active for 3+ months until the placenta takes over progesterone secretion
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SCCC BIO132 Chapter 28 Handout
Uterine Cycle (Menstrual Cycle)
-corresponds with ovarian cycle; same hormones regulate both
1. Mensus (day 1-5)
-correlates with beginning of follicular phase at ovary
-arteries constrict, tissues and glands of functional zone deteriorate
-necrotic vessels rupture, blood flushes necrotic endometrial tissue out of uterus to vagina = menstruation
(menstruation = loss of functional zone of endometrium)
2. Proliferative phase (day 6-14)
-correlates with follicular enlargement and oocyte maturation
-cells of basilar zone of endometrium multiply to restore the mucosa, glands, and vessels of the functional
zone
3. Secretory phase (day 15-28)
-correlates with ovulation and duration of luteal phase
-endometrial glands enlarge and secrete mucus rich in glycogen to nourish potential embryo
-secretion peaks 12 days post ovulation then declines as corpus luteum ceases hormone production
-if pregnancy occurs, secretion will continue and mensus will be inhibited
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SCCC BIO132 Chapter 28 Handout
Hormones and the Female Reproductive Cycle
- ovarian and uterine cycles must be coordinated to allow fertilization and implantation of an embryo
- GnRH levels changes over the duration of the cycles to alter the levels of FSH and LH which control the secretion of the female
sex hormones estrogen and progesterone. Sex hormone levels drive oocyte maturation and uterus development.
1. Follicular phase
- GnRH levels begin to rise triggering release of FSH and LH
- FSH and LH stimulate follicle growth and maturation and production of estrogen:
LH targets thecal cells to produce androstenedione
FSH targets granulosa cells to convert this to estrogens
- increasing estrogen levels trigger:
- continued oocyte and follicle development
- growth of new functional layer in the uterus and expression of progesterone receptors on the endometrial tissue
-negative feedback inhibition on the release of FSH and LH (both are still produced but are stored in the anterior
pituitary)
- granulosa cells of secondary follicles secrete inhibin which provides further negative feedback on FSH
2. Ovulation
- tertiary follicles are producing peak levels of estrogen which triggers:
- a burst of LH to be released (along with some FSH)
- thinning of the cervical mucus
- the LH surge triggers:
- primary oocyte to complete meiosis I forming the secondary oocyte
- ovulation: rupture of the secondary oocyte through the ovary wall
- formation of the corpus luteum from the damaged tertiary follicle
3. Luteal phase
- the corpus luteum secretes progesterone, estrogen, and inhibin
- increasing levels of progesterone trigger glandular secretion in the uterus and thickening of the cervical mucus
- all three luteum hormones (progesterone, estrogen, inhibin) act to provide negative feedback inhibition on LH, FSH and
GnRH production and release
- as LH levels decline, the corpus luteum begins to degrade forming the corpus albicans and luteum hormone secretion
ceases
- declining levels progesterone and estrogen trigger the initiation of mensus
- decreased levels of all three luteum hormones no longer provide negative feedback: GnRH levels increase and a new
cycle begins
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SCCC BIO132 Chapter 28 Handout