Anatomy Of Ovaries

Genital ridge

Friends, I am giving you a very important tabls. Many questions can be solvod trom lhis very table.

Male and female derivatives of embryonic urogenital structures.

Also know :

• Germ cells are of endodermal origin and migrate from yolk sac to genital ridge between 20 – 30 days.°
• Until the seventh week of development gonads do not develop male or female characteristic (i.e. are bipotential in nature).°
• SRY gene located on the short arm of Y chromosome, directly control the development of testis from the bipotential gonads.°
• In a XX individual, without the active influence of Y chromosome, the bipotential gonad develops into an ovary two weeks later than testicular development.°

Right handedness is more common in population [Ref: huinrep.oxforcijournal.org/content/12/8/]730full.pdf]

• In the primate it is suggested that ovulations occur with equal _.frequency in the left and right ovary.
• In the humans it there is some controversy about the frequency of ovulation on each side.
• It is believed that in normally menstruating women ovulation was significantly higher in right ovary.
• It is believed that right sided predominance was either genetically determined or due to difference in the  vasculature of the ovaries.
• The anatomical asymmetry between the left and right side are also thought to be the reason.
• The left ovarian vein drains to the left renal vein and the right ovarian vein to the inferior venacava.
• The left renal vein is thought to be under high pressure than the right and therefore drain slower. Because the left ovary drains slower, the collapsed follicle (corpus luteum) takes longer to clean and thereby diminishes the chances that ovulation will occur on that side the _.following month.

– No such condition exists on the right side which is why successive right side ovulation is more common.

The ovaries are paired organs situated close to the wall on either side of the pelvis minor, a little below the brim.

Each measures 2.5–5 cm in length, 1.5–3 cm in breadth, and 0.7–1.5 cm in width, weighing about 4–8 g.

The nerve supply of the ovaries arises from T10.

The ovary is suspended by means of the mesovarium, the suspensory ligament of the ovary, and the ovarian ligament.

C i.e. 10 weeks

C i.e. Yolk Sac

• Umbilical vesicle (Yolk sac) attains full development & is large at 32 days (4-5 weeks). It can be observed sonographically early in 5^th week. By 10 weeks, it shrinks to pear shaped 5 mm diameter and after 20 weeks it is not visible.
• Although umbilical vesicle contains no yolk, its essential due to

– Site of origin of primordial germ cells is endodermal lining of wall of umbilical vesicle (in 3^rd week)

–  In 3^rd week blood first develop in vascularized extraembryonic mesoderm covering the wall of umbilical vesicle, and continues to form there until hemopoietic activity begins in liver during 6^th week

Its endoderm, derived from epiblast, gives rise to epithelium of trachea, bronchi, lungs and digestive tract (form primordial gut in 4^th week)

Transfer nutrients to embryo in 2^nd & 3^rd weeks

Lymph Drainage of ovary

The lymph vessels of the ovary follow the ovarian artery and drain into the pre aortic and para-aortic nodes at the level of the first lumbar vertebra.

Arterial Supply

The ovarian artery arises from the abdominal aorta at the level of the first lumbar vertebra.

Venous drainage.

The ovarian vein drains into the inferior vena cava on the right side and into the left renal vein on the left side. Nerve Supply

The nerve supply to the ovary is derived from the aortic plexus and accompanies the ovarian artery.

Development of ovary

• Coelomic epithelium on medial side of the mesonephros becomes thickened to form genital ridge, the site where ovary develops.
• Genital ridge is covered by germinal epithelium (previous coelomic epithelium). From these germinal epithelium, cords of cells (sex cords or medullary cords) proliferate and grow into the underlying mesoderm.
• Primordial germ cells which are developed from endodermal cells of hindgut (part of yolk sac), migrate to region of developing ovary (genital ridge area) and give rise to oocytes.
• The sex cords become broken up into small masses. The cells of each mass surround one oocyte to form primordial follicle.
• At birth each ovary contains about 2 million primary follicles.

Each ovary lies in ovarian fossa on lateral pelvic wall which is bounded :‑

1. Anteriorly: Obliterated umbilical artery
2. Posteriorly: Ureter and internal iliac artery

Ans. is ‘d’ i.e., Free of ligament attachment

OVARY

The ovaries are female gonads. Each ovary lies in the ovarian fossa on the lateral pelvic wall which is bound anteriorly by obliterated umblical artery and posteriorly by ureter and internal iliac artery. Each ovary has two poles (upper and lower), two borders (anterior and posterior) and two surfaces (medial and lateral).

Upper pole (tubal end) is related to ovarian fimbria of fallopian tube and external iliac artery. Suspensory ligament of ovary (infundibulopelvic ligament) connents it with pelvic brim.

Lower pole (uterine end) is connected with lateral angle of uterus by ligament of the ovary, just posteroinferior to the attachment of fallopian tube.

Lateral surface is related to ovarian fossa and is covered with peritoneum which separates it from Obturator vessels and nerve.

Medial surface is related to fallopian tube and is separated by a peritoneal recess, called ovarian bursa.

Anterior border (mesovarian border) is straight and related to fallopian tube and obliterated umblical artery. It is attached to posterior surface of broad ligament of uterus by mesovarium and forms the hilus of ovary.

Posterior border (free border) is convex and is related to fallopian tube and ureter.

Ans. is ‘c’ i.e., Endoderm

The organ marked in the picture above represents ovary.

Development of ovary

• Coelomic epithelium on medial side of the mesonephros becomes thickened to form genital ridge, the site where ovary develops.
• Genital ridge is covered by germinal epithelium (previous coelomic epithelium). From these germinal epithelium, cords of cells (sex cords or medullary cords) proliferate and grow into the underlying mesoderm.
• Primordial germ cells which are developed from endodermal cells of hindgut (part of yolk sac), migrate to region of developing ovary (genital ridge area) and give rise to oocytes.
• The sex cords become broken up into small masses. The cells of each mass surround one oocyte to form primordial follicle.
• At birth each ovary contains about 2 million primary follicles.

Ans. is ‘a’ i.e., 2 million 

• In humans, no new ova are formed after birth. During fetal development, the ovaries contain over 7 million primordial follicles.
• However, many undergo atresia (involution) before birth and others are lost after birth.
• At the time of birth, there are 2 million ova, but 50% of these are atretic.
• The million that are normal undergo the first part of the first meiotic division at about this time and enter a stage of arrest in prophase in which those that survive persist until adulthood.
• Atresia continues during development, and the number of ova in both of the ovaries at the time of puberty is less than 300,000.
• Only one of these ova per cycle (or about 500 in the course of a normal reproductive life) normally reaches maturity; the remainder degenerate.