The Reproductive Systems includes
Primary sex organs (gonads)
- produce gametes and sex hormones
Accessory structures
- ducts, glands and external genitalia
Dartos Muscle
- smooth muscle in scrotum
- Cold = contracts = winkling skin
- Hot = releaxes = loose skin
Cremaster Muscle
- skeletal muscle at scrotum
- Cold = contracts = testes move closer
- Hot = releaxes = testes hang lower
tunica albuginea
- fibrous capsule surrounding the testes
- divides the testes into > 250 lobules
- each lobule contains 1-4 highly coiled seminiferous tubules where sperm are produced
2 types of cells in seminiferous tubules:
- Spermatogenic cells – give rise to sperm
* Sertoli (sustentacular) cells – nourish, protect and support spermatogenic cells
Sertoli (Sustentacular) Cells
- Form blood – testis barrier
- Substances from blood must pass thru Sertoli cells before they reach developing sperm
- Nourish spermatocytes, spermatids + sperm
- Phagocytize excess spermatid cytoplasm
- Control movements of spermatogenic cells
- Control release of sperm into lumen
- Produce fluid for sperm transport
- Regulate effects of FSH and testosterone
- Secrete hormone – inhibin (inhibits FSH release)
- Secrete androgen – binding protein into lumen → binds testosterone therefore keep it high for final stages of spermatogenesis
Spermatogenesis
• Occurs in seminiferous tubules
• 64-72 days
• Spermatogonia (stem cells that are 2N and remain dormant until puberty) divide by mitosis giving rise to type A and B spermatogonia
> Type A cells remain at basement membrane as a reservoir of cells for future cell division
> Type B cells grow and move toward lumen, called primary spermatocytes
spermiogenesis
haploid spermatids into spermatozoa (become elongated sperm)
Spermatozoa has 3 parts:
head – has nucleus and acrosome
midpiece – contains mitochondria
tail – is a flagellum
Pathway of Sperm
Seminiferous tubules–>Straight tubules –> rete testis –> efferent ducts –> epididymis –> ductus deferens –>ampulla–>ejaculatory duct–>prostatic urethra –> intermediate urethra–>spongy urethra
Internal Penis
corpora cavernosa (two lateral masses)
corpus spongiosum (midventral mass containing the spongy urethra)
Male Accessory Glands
Produce seminal fluid and include: Seminal Vesicles (2): 60% vol, released into ejaculatory ducts
Prostate Gland (1): 35% vol, empties into prostatic urethra
Bulbourethral Glands (2): 5% vol, released into urethra
Semen Function
- provide sperm with a transport medium
- provide sperm with nutrients
- neutralizes acidity of male urethra and female vagina
- contains an antibiotic to destroy bacteria in semen and lower female reproductive tract
Ovaries
• Surrounded by tunica albuginea
• cortex and medulla
> outer cortex: ovarian follicles
> inner medulla: loose CT, blood vessels, lymph vessels and nerves
Uterus
• has a fundus, body, cervix
• receives fertilized ovum
• protects and nourishes embryo
• wall has 3 layers:
> outer perimetrium
> middle myometrium
> inner endometrium (functional layer + basal layer)
- Functional: sloughs off during menstruation
- Basal: that gives rise to a new functional layer after menstruation
Vagina
- passageway for infant, discharge of menstrual fluid and receives semen
- lined with non-keratinized stratified squamous epithelium for protection from abrasion
cervix mucosal cells produce mucus
- at ovulation, mucus is less viscous
- mucus can block cervical canal when not fertile (impedes sperm)
- blocks spread of bacteria (vagina → uterus)
Pathway of Oocyte
Secondary oocyte: Ovary–>infundibulum–>fimbriae–>(4 days later)oviduct–> FERTILIZATION OCCURS–> (6-7 days later) Uterus
Oogenesis
- BEGINS BEFORE BIRTH!!
- Occurs in ovarian follicles in cortex of ovary
- Ovarianfolliclesare the basic units of female reproductive biology. Each of them contains a singleoocyte
- Oogonia (2N) –> [mitosis] primary oocytes (2N)–> [meiosis I] secondary oocyte (n) + first polar body
Puberty:
• FSH releases: primordial follicle –> primary follicle –> granulosa cells (produce estrogen)
• primary follicle –> secondary follicle –> a mature Graafian follicle
• Graafian follicle migrates to ovary surface
• LH triggers ovulation –> follicle ruptures –> secondart oocyte moves to oviduct –> fertilization –> [meiosis II] –> ovum + second polar body
- Remainder of ruptured follicle becomes corpus luteum (secrete progesterone and estrogen)
- If NO fertilization: corpus luteum –> corpus albicans
Hormonal Ctrl of Testes
Hypothalamus is in charge, just know gonadotropin GNRH (a releasing hormone from thalamus)
GNRH goes from capiliary bed in hypothalamus –>capiliary bed in anterior pituitary –> releases FSH LH
Role of FSH in Testes
FSH –> Sertoli (in seminiferous tubules) release androgen binding protein (can bind testosterone)
Role of LH in Testes
LH–> Leydid release testosterone
Inhibin
hormone released by the Sertoli cells which suppresses the production of FSH once spermatogenesis has progressed
2 Female Reproductive Cycle
Ovarian cycle – events involved in maturation of an oocyte
Menstrual (Uterine) cycle – events that prepare uterine endometrium to receive a fertilized ovum
Cycle is about 28 days
