ANAT 3001 reproductive system (internal pelvic anatomy)

male pelvic structures

ductus deferens and seminal vesicle

• ductus (vas) deferens enters pelvic cavity through inguinal canal

• ductus deferens joined by seminal vesicle to create ejaculatory duct within prostate gland

• seminal vesicles release into semen

  • fructose - energy supply for sperm cells

  • prostaglandins - promote dilation of cervical canal and contraction of uterus

clotting proteins - coagulates semen after ejaculation

prostate gland

• prostate gland located inferior to bladder

• ejaculatory duct joins the urethra within the prostate gland

  • seminalplasmin - antibiotic to combat urinary tract infections

  • prostate specific antigen (PSA) - liquefies semen after ejaculation

urethra

• carries urine and semen to exit the penis

• has specific regions

  • prostatic urethra - through prostate, joined by ejaculatory ducts

  • penile (spongy) urethra - through penis

bulbourethral gland

• produces mucus like substance that conditions penile urethra before ejaculation

  • neutralizes acidic urine and lubricates urethra

female pelvic structures

• bladder sits behind pubic bone

• vagina and uterus between bladder and rectum

• uterus arches anteriorly 

• uterine (fallopian) tube located anterior to ovary

pouches in the pelvis

peritoneum drapes over pelvic structures to form pouches

vagina and uterus

• vagina - muscular canal

  • stratified squamous epithelium

  • fornix - circular area surrounding the cervix

• uterus - hollow organ where embryo/fetus develops

  • cervix - inferior “donut shaped” projection into vaginal canal

uterine wall - 3 layers

• perimetrium

  • outer serous membrane (peritoneum)

• myometrium 

  • thick muscular layer

  • produces contractions during childbirth

• endometrium 

  • mucosal lining of uterine cavity, simple columnar epithelium with connective tissue

  • highly vascularized

  • functional layer - thick inner layer, shed during menstruation 

  • basal layer - thinner, not shed, forms new functional layer

uterus and adnexa

adnexa - 3 structures that hand from the uterus

1. uterine (fallopian tube

   1. transports oocytes from ovaries to uterine cavity 

   2. fimbriae - finger like projections that draw oocyte

2. ovary and ovarian ligament

   1. ovaries - gonads, produce gametes (oocytes)

3. round ligament

   1. travels anteriorly through inguinal canal on each side and attach to labia majori 

   2. positional support and anchor for uterus

homologous to the gubernaculum…

broad ligament

• draping of peritoneum over the uterus and adnexa 

• has three parts

  • mesometrium

  • mesosalpinx

  • mesovarium

3 parts of broad ligament

• mesometrium - covers uterus

• mesosalpinx - covers uterine tube

• mesovarium - covers ovarian ligament and ovaries 

blood supply to pelvic structures

• internal iliac artery gives off many branches to supply blood to pelvic structures 

  • vesical artery - to bladder (and prostates)

  • uterine artery - to uterus

  • vaginal artery - to vagina

  • middle rectal artery - to rectum

• each has corresponding veins that drain into the IVC

• ovarian (gonadal) artery - from abdominal aorta, supply ovaries

• ovarian (gonadal) vein 

  • left joins left renal vein

  • right joins IVC

• similar pattern to testicular arteries and veins but stay inside pelvis

• when ovarian arteries and veins covered in peritoneum, called suspensory ligament

blood supply to external genitalia

• internal pudendal artery - branch from internal iliac artery

  • main artery of perineum and external genitalia, also rectum

  • inferior rectal arteries

  • dorsal arteries of the penis/clitoris

  • deep arteries of the penis/clitoris

innervation to pelvic structures

• inferior hypogastric plexus - visceral sensory and motor innervation to pelvic structures and external genitalia

  • sympathetics via sympathetic trunk

  • parasympathetics via pelvic splanchnic nerves (S2-S4)

• pudendal nerve - from S2-S4, innervation of external genitalia 

  • dorsal nerve of clitoris/penis (sensory)

  • somatic motor branches to

    • muscles of pelvic floor

    • external anal/urethral sphincters

    • bulbospongiousis, ischiocavernosus

spermatogenesis

• formation of sperm within testes

  • spermatogonia (stem cells) differentiate into sperm, takes ~75 days

• occurs in seminiferous tubules of testes

• produce 400 million sperm per day

• starts at puberty and continues until death (declines with old age)

• 3 stages

stage 1

 formation of spermatocytes 

• spermatogonia (stem cells) located in outer region of seminiferous tubules

• spermatogonia undergo continuous mitosis (cell division) that results in 2 daughter cells:

  • type A - remain in outer region to maintain germ cell line

  • type B - move toward lemur as primary spermatocyte

stage 2

meiosis

• spermatocytes undergo meiosis

  • a process of 2 subsequent divisions

  • 1 diploid cell → 4 haploid cells (spermatids)

stage 3

spermiogenesis 

• spermatids differentiate into sperm

  • sperm have 3 parts

    • head - with nucleus

    • midpiece - with mitochondria to produce energy for tail

    • tail - flagellum that whips around to proper sperm

• sperm detaches from epithelium of seminiferous tubule and enters lumen

supporting cells - interstitial (leydig) cells

• located in connective tissue between seminiferous tubules 

• produce androgens (testosterone)

supporting cells - sustentacular (sertoli) cells

• with seminiferous tubules 

• sperm cells pass towards the lumen between sustentacular cells

• nutritional support of sperm cells

• produce inhibin (prevent spermatogenesis when sperm count is too high)

ovaries

• produce oocytes (oogenesis) in cortex

• produce estrogen and progesterone (sex hormones)

menstrual cycle

• approximately monthly hormone induces cycling of the ovary (ovarian cycle) and uterus (uterine cycle)

• ovarian cycle - stimulates development of ovarian follicles and the production of oocytes

• uterine cycle - prepares the uterine wall for implantation and nourishment of a fertilized ovum

oogenesis

• formation and development of oocytes

• starts in ovary, finishes in uterine tube

• 1 oocyte → 1 ovum + 2-3 polar bodies

  • ovum retains most of cytoplasm, polar bodies have primarily DNA and degenerate

• takes many years to complete (many steps)

spermatogenesis

• formation and development of sperm

• starts in testes, finishes in epididymis 

• 1 spermatocyte → 4 sperm cells

• occurs continuously, takes ~75 days

process of oogenesis

• process that begins before birth and stalls until puberty 

• in fetus 

  • oogonium (stem cell) → primary oocyte 

  • primary oocytes stalls before first division until puberty

• after puberty during ovarian cycle

  • primary oocyte → secondary oocyte

  • secondary oocyte arrests before second division until after ovulation, and will only produce an ovum when sperm attaches to oocyte 

ovarian cycle

3 phases

1. follicular phase (~day 1-13)

2. ovulation (~on day 14)

3. luteal phase (on ~day 15-28)

1. follicular phase

(~day 1-13)

• about 1.5 million primordial follicles (w/primary oocytes) present at birth, about 300-400 thousand at puberty 

1. follicle stimulating hormone (FSH) - stimulates release of 6-12 primordial follicles 

2. one primordial follicle continues to develop into tertiary follicle

2. ovulation

(~on day 14)

• mature follicle ruptures and releases secondary oocyte from the one of the persons two ovaries 

• secondary oocyte is swept into the uterine tube by the fimbriae 

• secondary oocyte does not complete secondary division unless sperm attaches

3. luteal phase

(on ~day 15-28)

• after ovulation, remaining part of the follicle collapses, called corpus luteum

• corpus luteum persists as an endocrine gland, secretes estrogen and progesterone

  • stimulate build up of endometrium in preparation for pregnancy

• if there is no implantation, corpus luteum dies after 2 weeks and becomes scar like tissue (corpus albicans)

menstrual cycle (review)

• uterine phases are closely coordinated with phases of ovarian cycle

• at puberty, pituitary gland releases follicle stimulating hormone (FSH) and luteinizing hormone (LH) to initiate ovarian cycle

• FSH and LH initiate changes in the ovaries during oogenesis

• FSH stimulates growth of primordial follicles

• cells in follicles release estrogen to rebuild functional layer of endometrium

• LH increases fluid and pressure in tertiary follicle until rupture (ovulation)

• corpus luteum releases estrogen and progesterone to prepare endometrium for implantation

uterine cycle coordination

fertilization

• secondary oocyte swept into uterine tube by fimbriae 

• sperm cells deposited at the cervix travel through uterus to uterine tube

• oocyte can remain in reproductive tract for 24 hours, sperm for 4 days

• fertilization - one sperm cell fuses with oocyte to form new diploid cell

  • occurs in ampulla typically

• fertilized ovum (zygote) moves toward uterine cavity and divides

implantation

• after 6 days, zygote implants in uterine wall (pregnancy)

  • corpus luteum keeps producing progesterone to stabilize uterine lining (placenta at 3 months)

• if no implantation, menstruation occurs

  • corpus luteum regresses, stops producing progesterone and estrogen