Transcript The Reproductive Systems

The Reproductive Systems
Chapter 23
Male Reproductive System
• Organs: testes, ducts, glands & supporting
structures
• Ducts: epdidymis, ductus deferens,
ejaculatory ducts & urethra
• Glands: seminal vesicles, prostate,
bulbourethral glands
• Supporting structures include scrotum &
penis
Figure 23.1
Scrotum
• Pouch that supports the testes
• Septum separates into separate sections for
each testis
• Sperm requires temperatures 2-3oC below
body temperature
• allows raising and lowering testes to adjust
temperature
Testes
• Paired oval glands
• Develop on embryo’s posterior wall and
descend into scrotum
– Starts in 7th month
• 200-300 lobules containing seminiferous
tubules
• Lined with spermatogenic cells:
spermatagonia & sertoli cells
Figure 23.2a
Figure 23.2b
Spermatogenesis
• Stages: meiosis I, Meiosis II,
spermiogenesis
• Occurs in seminiferous tubules
• Cell types involved: spermatagonia, sertoli
cells & interstitial cells (leydig cells)
• move through rete testes
• ->epididymis
Meiosis
• Cells have 23 pairs of chromosomes
– diploid= paired homologous chromosomes
• Gametes are Haploid:
– Unpaired chromosomes
• Meisosis is the process by which this can
happen
• Required for gamete production
Spermatogenesis stages
• Takes ~65-75 days from first division to release
• Spermatogonium divides: mitosis
– One cell is stem cell other differentiates into primary (1o)
spermatocyte
• 1. Meiosis I. chromosomes replicate
– Line up as pairs of homologous chromosomes
– Chromosomes twist and some exchange of material between
chromosomes can occur
– Each homologous pair separates and a member moves to
opposite end of cell
– After cell division each cell is haploid
Stages (cont.)
• The cells from meiosis I are : secondary
spermatocytes
– Each cell is haploid- has two copies of each
chromatid
• Meiosis II: divide again– One copy of each chromatid in each new cell
• Cells are: spermatids
Stages (cont.)
• Spermiogenesis- each spermatid develops
into a sperm cell
• Process requires support of Sertoli cell
– Often called “nurse cell”
Figure 23.3
Spermatozoa Structure
• ~300 million /day
– Life time ~ 48 hrs in female tract
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Structure: Head, middle, tail
tail- flagellum = motility
Middle - mitochondria = energy
Head-chromosomes + acrosomal cap
acrosome-enzymes-> penetrating egg
Figure 23.4
Hormonal Control
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At Puberty- hypothalamus GnRH
Pituitary LH & FSH
LH Leydig cells  testosterone
Negative feedback to suppress LH & GnRH
FSH + testosterone stimulate spermatogenesis
Sertoli cells  inhibin inhibits FSH
release optimum sperm production
Figure 23.5
Androgen Effects
• Prenatal- male pattern of development:
– Male ducts, descent of testes, external genitals &
brain regions
• Puberty: enlargement of organs, secondary
characteristics:
– Muscular & skeletal growth, hair patterns,
thickening of skin
• Sexual function: sexual behavior,
spermatogenesis & libido
• Stimulation of anabolism: stimulate protein
synthesis & muscle & bone growth
Ducts- Sperm route
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Epdidymis vas (ductus) deferens
 ejaculatory duct (by seminal vesicles)
 urethra in prostate
pass bulbourethral glands (alkaline + mucus fluid)
 penis and ejaculation
Figure 23.6
Accessory Glands
• Seminal vesicles- seminal fluid– Fructose (sperm ATP production
– + alkalinity (neutralize acid in tracts)
– + prostaglandins-activation of sperm
• Prostate- surrounds upper urethra
– Increases volume + adds antibiotics
• Bulbourethral glands:
– More alkalinity + mucus fluid
Penis
• Contains urethra- root, body & glans penis
– Passage for semen & urine
• Root- attached portion
• Body- 3 cylindrical masses erectile
– Dorsal – Corpora Cavernosa Penis
– Midventral- Corpus Spongiosum penis- contains
urethra
• Glans penis has external urethral oriface
• Uncircumcised glans covered by prepuce
Arousal & Ejaculation
• Parasympathetic impulses erection
– Dilation of penile arteries
– Volume compresses veins so outflow is slowed
• Ejaculation is a Sympathetic reflex
– Peristaltic contractions in ductus deferens, seminal
vesicles, ejaculatory ducts & prostate emission
– Sphincter at urinary bladder closes
– Forceful release of semen from urethra
Female Reproductive System
• Ovaries: paired organs- produce
– secondary oocytes ova (after fertilization)
– Hormones: progesterone & estrogens
– From same embryonic tissue as testes
• uterine (fallopian) tubes & uterus
• vagina
• External organs (vulva or pudendum)
Figure 23.6
Histological Structure
• Germinal epithelium- covers surface
• Ovarian cortex: connective tissue containing
follicles
• Follicle; oocyte + surrounding cells
– Surrounding cells nourish oocyte & produce
hormones
– Grows during maturation 
• Graafian follicle ovulation
• Post ovulation  corpus luteum
– Progesterone, relaxin & inhibin
Figure 23.7
Oogenesis
• Begins before birth– Oocytes not continually produced
• Meiosis I- start before birth & finish at puberty
– during fetal development form oogonia
– Before birth some  primary oocytes
– Monthly hormones  some to complete meiosis I
• Two uneven haploid cells=
• secondary oocyte & polar body (discarded)
Oogenesis (cont.)
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Secondary oocyte has most of cytosol
Then begins meiosis 2 & stops
Then ovulation into uterine tube
If fertilization then meiosis II is
completed ovum + 2nd polar body
• Nuclei of sperm & ovum unite
• Diploid zygote
Figure 23.8
Uterine Tubes
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Two tubes- extend laterally from uterus
End in fringe  Fimbriae
Fimbriae sweep secondary oocyte into tube
Oocyte moved by cilia lining wall
Zygote reaches uterus in ~7 days
Uterus
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Pathway for sperm & site of implantation
Fundus -Dome-shaped area above tubes=
Body – tapering central portion
Cervix- narrow opening into vagina
Uterine cavity- interior of body
Vagina
• extends from exterior to cervix
• Receptacles for penis and outlet for menstrual
flow
• Fornix- recess surrounds cervix
• Acid environment- prevents bacterial growth
• Smooth muscular layer- adjusts for intercourse or
birth
• Thin membrane fold can cover vaginal orifice =
hymen
Figure 23.9
Perineum & vulva
• Perineum: Diamond-shaped area between
thigh & buttocks of both males & females
• Vulva or pudendum = external genitalia
• Mons pubis- elevation of adipose tissue
• labia majora- extends back from mons
pubis
– Same fetal tissue as scrotum
• Labia minora- internal to majora
Perineum & vulva (cont.)
• Clitoris- small cylindrical mass of erectile tissue &
nerves
– Also contains prepuce & glans
• Vestibule: between labia minora
• External urethral oriface- anterior to vaginal oriface
• Paraurethral glands- either side of urethra
– Same embryonic tissue as prostate
– Secretes mucus
• Greater vestibular glands- adds to mucus
– Camparable to bulbourethral glands
Figure 23.10
Mammary Glands
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Modified suduriferous glands
Nipple- pigmented projection with openings
Areola- surrounds nipple
Internally-15-20 lobes lobules alveoli = milk
secreting glands
– Matures at puberty
• Lactation = synthesis, secretion & ejection of
milk
Figure 23.11
Female Reproductive Cycle
• 24-34 days- cycles in both ovaries & uterus
• Ovarian cycle= maturation of follicle, ovulation
& corpus luteum formation
• Uterine Cycle= menstrual cycle
– controlled by hormones from ovary
– Estrogens growth of endometrium
Progesterone supports endometrium for
implantation
• Combine cycles = Reproductive cycle
Figure 23.12
Hormonal Regulation
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GnRH (hypothalamus) controls
GnRH FSH & LH
FSH follicle growth & estrogen secretion
High estrogen  LH surge  ovulation
LH supports corpus luteum  progesterone
& estrogen secretion + relaxin & inhibin
• Inhibin  decreased FSH release
Hormones
• Estrogen:
– Development & maintenance of reproductive
structures & secondary characteristics
–  protein synthesis & growth
– Lower blood cholesterol level
• Progesterone maintains myometrium for
implantation
• Relaxin= relaxes uterus- inhibits myometrium
• Inhibin- inhibits FSH release
Phases of Cycle
• Menstrual phase: ~1st 5 days of cycle
– Several Ovarian follicles enlarge
– Decreased progesterone & estrogen uterine arteries
constrict endometrium sloughs off
• Preovulatory- between menstruation & ovulation
– Ovaries: follicles grow & secrete estrogen & inhibin
one dominates
– Uterus: growth of new endometrium
Phases of Cycle (cont.)
• Ovulation
– Release of 2o oocyte with LH surge
• Postovulatory– Ovaries: follicle collapses corpus luteum
(luteal phase)
– If no fertilization  FSH & LH  corpus
albicans & decreased Progesterone 
menstruation
Phases of Cycle (cont.)
• If fertilization & division human
chorionic Gonadotrophin (hCG)
stimulates corpus luteum secretion
• Uterus: Progesterone & estrogens
complete development of uterus for
implantation
Figure 23.13
Birth Control Methods
• Surgical: vasectomy in males
– ductus deferens segment removed
• Tubal ligation in females
– Close uterine tubes
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Chemical interference
– oral hormones, implants, injections, spermicide
• Blocking physically
– IUD, condoms, cervical cap
• Timing
– temperature, mucus charting, calendar
• Abortion
Aging
• Puberty- pulses of LH & FSH
• Rise in sex steroids
– Growth & secondary characteristics
– start of female reproductive cycle
• follicles become exhausted Menopause
– estrogen secretion declines
– lose feedback on pituitary  high FSH & LH
– Decline in estrogen supported functions
• In males- slower decline of function