17 - Reproductive Systems Flashcards
What are the three generic structures of a reproductive system?
- gonads (testes/ovaries)
- produce gametes + hormones
- ducts
- transport & store gametes
- accessory glands
- produce secretions that support gametes
Describe the male gonads
gonads = testes
- located within the scrotum (skin + CT)
- surrounded by 2 tunics:
a) tunica vaginalis
- outer serous membrane
- derived from peritoneum
b) tunica albuginea
- inner fibrous capsule of CT
- extends inward to divide testis into lobules - each lobule contains:
a) seminiferous tubules
- produce sperm by spermatogenesis
- tubules unite to form rete testis (rete = network)
- walls contain:
i) germ cells in various stages of development
ii) Sertoli cells (sustentocytes)
- surround developing gametes
- extend from basement membrane to lumen
- support and nourish germ cells
- have tight junctions - form blood-testis barrier
- protects sperm from immune system, toxins, drugs etc
- produce testicular fluid
- for transport of sperm in lumen
- respond to follicle-stimulating hormone (FSH)b) Leydig cells (interstitial cells)
- in CT between seminiferous tubules
- secrete testosterone (hormone)
Describe the male ducts
- sperm from seminiferous tubules into rete testis
- then into duct system:
a) Epididymis- posterior border of testis
- stores sperm
- sperm mature (develop ability to swim)
b) Vas (ductus) deferens - enters pelvic cavity
- loops over posterior bladder
- vasectomy = vas deferens cut & tied off
- Spermatic Cord - contains vas deferens, nerves (ANS) veins, artery, lymph vessels, muscle (skeletal)
c) Ejaculatory Duct - formed by union of vas deferens and duct from seminal vesicle
d) Urethra - 3 regions:
i) prostatic - through prostate
ii) membranous - through urogenital diaphragm
iii) ) penile (spongy) - through corpus spongiosum of penis - opens on the glans penis
Describe the penis
- parts:
a) root
b) body (shaft)
c) glans penis (enlarged tip) - 3 bodies of erectile tissue - contains blood sinuses, bound by CT
→ 2 corpora cavernosa (dorsal portion of root and shaft)
→ 1 corpus spongiosum (the glans and the midventral portion of the root and shaft, surrounding the urethra)
Describe the male accessory glands
~ 95% of semen
a) Seminal vesicles (2)
- posterior to bladder
- secrete alkaline fluid that contains fructose to nourish sperm
~ 60% of volume of semen
b) Prostate Gland (1)
- inferior to bladder and encircles prostatic urethra
- secretes milky, alkaline fluid - nourishes sperm
~ 30% of volume of semen
c) Bulbourethral glands (2)
- below prostate in urogenital diaphragm (in contact with external urethral sphincter)
- secrete thick alkaline mucus – helps neutralize acidic urine in urethra, lubricates
~ 5% of volume of semen
Describe the process of spermatogenesis
- sperm production (within seminiferous tubules)
Spermatogonia (2n) ↙ ↘ ↙ mitosis ↘ ↙ ↘ differentiate ↙ ↘ 1 1⁰ spermatocyte (2n) spermatogonia (2n) ↓ meiosis I maintains cell line ↓ 2 2⁰ spermatocytes (n) ↓ meiosis II ↓ 4 spermatids (n) ↓ Spermiogenesis (final stage) ↓ 4 spermatozoa (n)
Define spermiogenesis
- differentiation of a spermatid = spermiogenesis:
- develop acrosome + flagellum
- lose most cytoplasm
Describe the structure of a spermatozoon
1) Head
- nucleus (23 chromosomes (n))
- at tip of nucleus = acrosome
- contains digestive enzymes (to penetrate oocyte)
2) Body (midpiece)
- large # mitochondria
- produce ATP for movement
3) Tail = flagellum
- propel sperm
- made of microtubules
Describe semen
- sperm, testicular fluid + accessory gland secretions
- 2 - 5 mL released at ejaculation
- contains 20-150 million sperm/mL
- pH 7.2- 7.6
- provides sperm with transportation medium, nutrients + protection
Describe the female gonads
gonads = ovaries
- located in pelvic cavity on lateral sides of uterus
- histology:
- 4 layers
a) superficial/germinal epithelium
b) tunica albuginea - CT
c) ovarian cortex
- contains ovarian follicles + CT
- follicles = layers of cells surrounding immature egg (support + protect)
d) ovarian medulla
- blood + lymph vessels, nerves, CT
- held in place by:
a) ovarian ligament
- to uterus
b) suspensory ligament
- to pelvic wall
a) mesovarium
- superior membrane
→ NOTE: suspensory ligament + mesovarium = parts of broad ligament = parietal peritoneumDescribe the uterine tubes
Uterine (Fallopian) Tubes
- 3 sections:
a) infundibulum- suspended over ovary
- has finger-like projections = fimbriae
b) ampulla = middle - fertilization occurs here
c) isthmus - connects to uterus
- histology:
a) mucosa- simple columnar epithelium with cilia or microvilli
- moves oocyte or cell mass along tube
- secretes nutrient fluid
b) muscularis externa - smooth muscle - helps movement
c) serosa - visceral peritoneum
Describe the uterus
- hollow organ
- 3 parts:
a) fundus- above level of uterine tubes
b) body - main portion
- space within = uterine cavity
c) cervix - inferior, narrow portion - opens into vagina
- above level of uterine tubes
- supportive membranes (attach uterus to abdominal wall)
a) broad ligaments - peritoneum
b) round ligaments- fibrous CT - attach uterus to anterior body wall
c) uterosacral ligaments - peritoneum - attach to sacrum
- fibrous CT - attach uterus to anterior body wall
- histology:
- 3 layers:
a) perimetrium- outer layer
- visceral peritoneum
b) myometrium - 3 layers of smooth muscle (muscularis externa)
c) endometrium - mucous membrane
- contains endometrial glands – secrete a nutritive fluid
- 2 layers:
i) stratum functionalis
- faces uterine cavity
- shed monthly (menstruation)
ii) stratum basalis
- permanent
- undergoes mitosis to replace functionalis
Describe the vagina
- birth canal, passageway for sperm + menstrual flow
- histology:
a) mucosa- stratified squamous epithelium
- rugae
b) muscularis externa - 2 layers of smooth muscle
c) adventitia - fibroelastic CT
- no serosa
Describe oogenesis
- gamete production (within ovarian follicles)
Oogonia (2n) ↓ mitosis ↓ many oogonia ↓ differentiate ↓ 1⁰ oocyte (2n) ↙ meiosis I ↘ 2⁰ oocyte (n) - ovulated 1st polar body (n) ↓ if fertilized ↙ meiosis II ↘ 1 ovum (n) 2nd polar body (n)
- 1 1⁰ oocyte forms 1 ovum and 2 or 3 polar bodies
- polar bodies = discarded nuclear material
- oogonia: ~ 5 million present in 6 month fetus
- 1⁰ oocytes (2n): ~ 1 million in ovaries at birth (no oogonia)
- enter meiosis I before birth, but arrest in prophase I
- at puberty (~400,000 oocytes remain), LH (luteinizing hormone) stimulates completion of meiosis I
- 2⁰ oocyte (n):
- begins meiosis II and arrests in metaphase II
- this is ovulated (usually 1/month)
- ~ 500 ovulated from puberty to menopause
Describe the stages of female follicular developement
1) Primordial follicle
- in ovary at birth
- 1⁰ oocyte surrounded by a single layer of flat cells
2) Primary follicle
- single layer become cuboidal – cells now called granulosa cells
- granulosa cells proliferate (become stratified)
- secrete zona pellucida around oocyte
- theca cells (endocrine) form from surrounding tissue
- can reach this stage any time from before birth to menopause
3) Secondary follicle
- at puberty, ovarian cycles begin
- under influence of rising FSH:
- granulosa cells proliferate more and start to secrete fluid (accumulates between cells)
- estrogen secretion begins
4) Vesicular follicle
- on surface of ovary
- fluid filled spaces unite into single large antrum
- granulosa cells that still surround oocyte = corona radiate
- continues secreting estrogen
- estrogen triggers release of luteinizing hormone (LH) causing:
a) completion of meiosis I
- enters meiosis II and arrests in metaphase II
b) ovulation – release of 2⁰ oocyte from follicle into peritoneal cavity (egg sheds follicle)
5) Corpus luteum
- follicle that remains after ovulation
- produces high levels of estrogen and progesterone to support fetal development
- if no pregnancy, degenerates into…
6) corpus albicans
- scar tissue
- no more hormones released
