31. The anatomy, histology and development of the ovary.

Anatomy of Ovary

* only structure in ab/pelvis cavity that is EXTRA PERITONEAL

General Info:
surface covered w. germinal epithelium, which is modified peritoneal covering from development

Location: in ovarian fossa, in post part of broad ligament, @ lat wall of pelvis, located @ bifurcation point of common iliac a on both sides, @sacro-iliac joint

Topography:

• ant = med umbilical ligament
• post = ureter & int iliac a
• sup extremity = infundibulum of uterine tube, end suspended via suspensory ligament of ovary (contains ovarian a/v) = highest point of broad ligament
• inf extremity = angle of body, uterine tube via proper ligament of ovary (analogous to guberlaculum testis)

Peritoneal relations:

• connects to post side of broad ligament via mesovarium
• NOT covered w/ peritoneum, so ovum can fall into peritoneal cavity –> fallopian tube
• CLINICAL NOTE – if somehow fertilized outside of uterine tube, can cause ectopic pregnancy

• • The ovary is anchored to the posterior aspect of the broad ligament by a peritoneal fold, the mesovary.

  • The suspensory ligament of the ovary extends from the tubal end of ovary to the lateral wall of the pelvis. It contains the ovarian blood vessels and nerves.

• Farre line: a whitish line marking the insertion of the mesovarium at the hilum of the ovary.
  

Blood Supply: ovarian a (contained w/in suspensory ligament of ovary)
has ovarian and tubal br that make anatomosis w/ ovarian br/tubal br of uterine a

Venous drainage:

• veins draining ovary make a pampiniform plexus (like the one around the testis), that run w/in broad ligament
• Ovarian v – R –> IVC
• L –> L renal v

Lymph drainage: vessels follow ovarian a/v and join vessels from uterine tube and fundus of uterus –> lumbar lymph plexus

Nerve Supply:

• SNS and aff fibers –> run w/ ovarian a/v —> make connections w/ pelvic plexus –> ovarian n plexus
• PNS: from pelvis splanchnic n –> same route w/ ovarian vessels

Histology of Ovary

Slide #72 Ovary *H&E

Structures to Identify:

• primoridal follicle
• germinal epithelium
• primary follcile
• secondary follicle
• tertiary (grafiaan) follicle
• corpus luteum
• corpus hemorroidal
• corpus fibricans
• corpus albicans
• cumulus oophorus
• corona radiata
• zona pellucida
• theca internta
• theca externa
• granulosal cells
• stromal tissue (spino cellular tissue)

General Info

• 2 major functions = production of gamete (oocytes), production of hormones (progesterone, estrogen)
• has tubular pole – connected to suspensory ligament
• has uterine pole – connect to uterus via proper ligament of ovary
• External cortex – site of follicular maturation
• Internal medulla – rich in CT, lymph, a/v

Function:Hormone secretion = corpus luteum responsible for Steroidogenesis
1. Estrogen – promotes maturation of internal and externa genitalia, and development of mammary gland
2. Progesterone – prepare uterus for pregnancy, and mammary gland for lactation.
Both hormones play key role in menstrual cycle

Cortex

• Epith = cuboidal germinal epithelium, instead of mesothelium,
  • Therefore,  in case of ovulation, rupture of epith is possible to release oocyte.
  • The epith can grow and cover the rupture hole.
  • Repeated rupturing due to monthly ovulation of a woman leads to a scarred look on the epith.
  • There is  no mesothelium coverage, because ovary is EXTRAperitoneal, though is continuous with mesothelium of visceral peritoneum of surrounding areas.

• Beneath that is a layer of dense CT = tunica albuginea.
• Then is the stromal or spinocellular tissue, in which all the follicles are embedded
  • also just called stroma
  • contains fibrocytes and smooth m cells, that contribute to theca externa

Stages of Follicle Maturation: — find follicles within the cortex.

follicular development

• process beings with premordial follicle and ends with ovulation of oocyte into uterine tube
• occurs under influence of FSH
• In fetal life, oocytes divid mitotically, creating HUGE # of oogonia (not so in life)
• As female goes thru puberty, ovaries begin process of reproductive activity  characterized by  growth and maturation of oocytes and surrounding follicles, meaning that the size of follicles can te4sll how close we are to creating mature oocyte.

Primoridal follicle: – make about 20/month.

• oocyte surrounded by single layer of follicular cells,
• simple squamous epith
• resting in prophase

primordial follicle

1st Primary follicle

• follicular cells enlarge and become cuboidal = now called granulosa cells,these cells later form the corona radiata
• zona pellucida starts to appear – non cellular layer between corona and oocyte itself
  • Glycoprotein rich zone (ZP 1, 2, 3 )
  • Zone of contact and communication between oocyte microvilli and granulosa cell processes.
  • Develop gap junctions
• oocyte itself becomes bigger

primary follicle

2nd primary follicle –

• zona pellucida is present (very eosinophillic, made of carbs, can be stained by PAS)
• follicular epith become stratified and becomes known as stroma granulosum.
• Theca cells from surrounding CT begin to be seen. These are actually stromal cells layering themselves into two layers

Seconday follicle –

secondary follicle

• Clear theca interna and externa seen, zona pellucida seen
• antrum vacuoles start to appear
  • with follicular liquor inside, that contains peptides produced by granulosa cells
  • if u see an antrum = secondary follicle
• granulosa cells on one side of follicle surrounds the oocyte to form = cumulus oophorus
• Between layer of granulosa cells and theca cells is a thin basement membrane
• Theca internata is thicker and very defined inner layer –> produces hormones
• Theca externa is much thinner and interweaves with surrounding CT

Tertiary follicle = Graafian follicle

• Largest ones in slide, usualy closer to center of slide
• theca interna  and theca externa are thicker
• cresent shapen antrum is now seen (formed by merging of previously seen vacuoles)
• corona radiata (communicates with gap junctions)
• oval within inter cavity, with liquid inside
• oocyte accentric within follicle (attached to one side)
• granular cells protrude into cavity to produce the cumulus oophorus.

Remember that the corona radiata accompanies oocytes in ovulation, as well as the zona pellucida.

Within follicle, seconday oocyte has 1 cm diameter.

Maturation of follicles are activated by FSH (Follicular stimulating hormone), EGF (Epidermal Growth Factor), and Ca2+

Oocyte stops growing thanks to OMI (Oocyte Maturation Inhibitor), secreted by the granulosa cells.

Oocyte maturation

• Oocytes stay in primary follicle phase for 15-20 years in prophase I of 1st Meiotic division
• Completion of 1st stage of Meiosis occurs only before the ovulation in the Graafian follicle.
• Primary oocyte (4n) splits into –> Secondary oocyte + 1st polar body
• Secondary oocyte is arrested in metaphase of 2nd meiotic division
• completed only if seconday oocyte is penetrated by spermatogonia, in which case the seondary oocyte –> final oocyte + 2nd polar body

Fertilization (discussed in more detail in another topic)

• Occurs in ampulla of uterine tube – secondary oocyte and sperm meet
• Before this, capacitation occurs to spermatozoa, allowing to bind to receptors on zona pellucida
• By binding to these receptors, acrosomal reaction of spermatozoa occurs, (enzyme release by cap of sperm to enable the sperm to penetrate the oocyte)
• Male pronucleus combine with female pronucleus –> zygote is formed

3 mechanisms to ensure only 1 sperm enters oocyte
Depolarization of Oolema
Cortical reaction
Zonal reaction

Medulla

• dense irregular CT, that is connected to the uterus via meso-ovary.
• has many a/v

Slide # 73 Ovary w/ Corpus Luteum

Unique structures to Identify:

• Granulosa lutein cells
• Theca lutein cells
• Follicular cavity
• CT
• a/v

General Info:

Follicular atresia – at any point of follicular development, it can degenerate and then be absorbed via phagocytosis

• atretric cells can be seen through out cortex
• Early Stage:
  • theca interna and granulosa cells intact
  • some cells are in antrum within the follicular fluid
  • cumulus oophorus maybe be disrupted
  • oocyte starts to degenerate
  • BM is thicker and folded = glassy membrane
• Late Stage:
  • much smaller
  • stroma replaces follicular cells entirely
  • glassy membrane  is even thicker and folded

late follicular atresia

Corpus Luteum – formed after ovulation of a mature follicle and collapse of its wall

After ovulation, hemorrhage into the remains of the follicle usually occurs resulting in a structure called a corpus hemorrhagicum.  This transitory structure develops into a corpus luteum.

In most species LH from the pituitary gland initiates this luteinization and stimulates the granulosa cells to secrete progesterone.    The granulosa cells undergo hyperplasia (proliferation), hypertrophy (enlargement) and are transformed into granulosa lutein cells.   In several species, including the human, the accumulation of a yellow lipid pigment (lutein) and other lipids marks the transition to granulosa lutein cells.  The cells of the theca interna are also transformed into lipid-forming cells called theca lutein cells. The resulting structure is highly vascular.  If fertilization occurs, the corpus luteum persists and secretes progesterone.

If fertilization does not occur, the corpus luteum degenerates and is replaced by connective tissue forming a corpus albicans.

• theca lutein cells – formed from theca interna cells, located in periphery of corpus luteum, and w/it its fold
• granulosa lutein cells – hypertrophic granulosa cells (over grown)
• Theca externa CT pierces the walls of it.
• Later stage of it:
  • lutein cells shrink
  • pyknosis of the nuclei
  • fibrous center
  • CT replaces luteal cells  to form temporary fibrous capsule — eventually forms corpus albicans

Embryology of Ovary

Development of Ovaries:

• Intermediate mesoderm from longitudinal elevation along dorsal body wall = urogenital ridge
• coelomic epith & mesoderm of urogenital ridge proliferate = gonadal ridge
• Primary sex cords develop from gonadal ridge –> and absorb in primordial germ cells from yolk sac
  • Primary sex cords develop into rete ovarii – not there in adult life
• Secondary sex cords develop and absorb in primordial germ cells from yolk sac ,too
• –> break apart  into cell clusters = primordial follicles – that undergo FOLLICULAR DEVELOPMENT (see histo)

Mesoderm origin = primary oocytes, simple squamous lining, CT stroma of ovary

Descent of Ovaries:
all that was listed above occurs in abdominal cavity, and then descent into pelvic cavity
involves gubernaculum – a fibrous tissue that runs from:

• ab wall to end of ovary –> form ovarian ligament,
  
• and to labia majora –> form round ligament of uterus