Female Reproductive System - OVARIES

STD-12      UNIT-6     CHA-3

HUMAN REPRODUCTION

Female Reproductive System - OVARIES 

Female Reproductive System

• The female reproductive system consists of the ovaries , uterine tubes , uterus , vagina , and the external genitalia . Because of their role in nourishing the offspring , the breasts or mammary glands are considered part of the female reproductive system . 

• Ovaries 
• Ovaries are primary sex organs in human female .
• The ovaries are paired stuctures located in the upper pelvic cavity . 
• Each ovary , shaped like an unshelled almond , is about 2 to 4 cm in length.
• The ovarian ligament ( ligment of ovary ) attaches the ovary lo the uterus.
• The broad ligament of the uterus which is itself part of the parietal peritoneum attaches to the ovary by a double layered fold of peritoneum called the mesovarium . 
• As we shall see later , the ovaries are responsible for producing female sex hormones and ova . 

• The ovary consists of the following parts . 

• The ovary is covered by a layer of cubical epithelium called the germinal epithe lium . 
• The germinal epithelium is covered by visceral peritoneum .
• Beneath the epithelium is the tunica albuginea- a layer of connective tissue and underlying it is the ovarian stroma .
• The ovarian stroma consists of a dense outer layer called the cortex and a less dense inner portion called the medulla . 
• No more oogonia are formed and added after birth . 
• Oogonia ( egg mother cells ) divide by mitosis forming primary oocyte . 
• Each primary oocyte then gets surrounded by a layer of granulosa cells called primary follicle . 
• A large number of these follicles degenerate during the phase from birth to puberty . Therefore , at puberty only 60.000-80.000 primary follicles are left in each ovary . 
• The primary follicles are surrounded by mono layers of granulosa cells and called secondary follicles . 
• The secondary follicle soon changes into a tertiary follicle which is characterized by a fluid filled cavity called follicular antrum ( Gr . antron = a cave ) . 
• The tertiary follicle is further converted into mature follicle or Graafian follicle .  
• Interspersed throughout the cortex are many ovarian follicles ( also called Graafian follicles ) in different stages of development . The ovarian follicle comprises the following parts . 
• A follicle consists of an oocyte covered by a homogenous membrane the zona pellucida . 
• When the surrounding cells form a single layer they are called follicular cells . 
• Later in development when they form several layers , they are referred to as granulosa cells . 
• The surrounding cells nourish the developing oocyte and begin to secrete estrogens as the follicle grows larger . 
• The zona pellucida is surrounded by follicular cells called membrana granulosa . 
• The follicle has an eccentric follicular cavity or follicular antrum filled with a fluid , the follicular fluid or liquor folliculi . A solid mass of the follicular cells that surrounds the developing ovarian follicle is called the cumulus oophoricus formed by granulosa cells . 
• It projects into the follicular cavity ( = follicular antrum ) . Later , the granulosa cells lying in close vicinity of the oocyte and zona pellucida , become elongated to form the corona radiata . 
• The membrana granulosa is surrounded by the theca interna ( theca = cover ) and theca externa 
• The total number of follicles in two ovaries of a normal young adult woman is about four lakhs . 
• Many ovarian follicles ( during pri mary oocyte stage ) undergo degeneration . 
• This degenerative process of follicles is called follicular atresia and such follicles are known as atretic follicles . 

• The release of secondary oocyte from the ovary is called ovulation.
• It occurs due to the rupturing of ovarian follicle and the wall of the ovary .
• Generally one secondary oocyte is re leased in each menstrual cycle average du ration 28 days ) by alternate ovaries . 
• Only about 450 secondary oocytes ( ova ) are produced by a human female over the entire span of her reproductive life which lasts about 40-50 years of age ( in some cases 45-55 years ) . 
• In addition to releasing an oocyte , the follicle also produces hormones . While the follicle is maturing , some of the follicular cells produce estrogens , mainly estradiol 
• After ovulation many of the follicular cells remain in the collapsed follicle on the surface of the ovary . 
• The antrum ( cavity ) of the collapsed follicle fills with a partially clotted fluid . 
• The follicular cells enlarge and fill with a yellow pigment , lutein . Such a follicle is called a corpus luteum literally , yellow body . 
• The lutein cells secrete small amount of estradiol hormone and significant amount of the progesterone hormone . 
• Corpus luteum also secretes relaxin hormone .
• Degenerated part of the corpus luteum is called corpus albicans , literally meaning white body Infect it is a white scar - like area . 

Functions of Ovaries . 

• Production of ova and secretion of female sex - hormones . 
• Two Fallopian tubes ( oviducts ) . uterus and vagina constitute the female accessory ducts .

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