Female Reproductive System

(Ovaries) Female gonads Produces female sex hormones Produce a limited number of gametes called eggs or ova (ovum) Are connected to the uterus by two tubes known as fallopian tubes

Fallopian Tubes Also known as an oviduct Tubes that connect the ovaries to the uterus Site of fertilization Ends of each tube contain fingerlike projections known as fimbria Fimbria sweep eggs into the oviduct http://www.youtube.com/watch?v=2-VKgdhfNpY&feature=related

Uterus Hollow, upside down, pear-shaped organ Located between bladder and anus Largest organ in female system Site of embryo and fetal development Composed of two types of tissues: Muscular outer lining Glandular inner lining called endometrium

Cervix Muscular band that separates uterus from the vagina

Vagina Connects the uterus to the outside environment Site of sexual intercourse and birth canal Acidity creates a hostile environment for microbes Connected to the uterus by the a muscular band known as the cervix

What is the main difference we see between the female and male reproductive system?

Ovum Egg cell Much larger than male sex cell Packed with nutrients to allow for rapid cell division once fertilized Contains 23 chromosomes

Oogenesis Formation and development of mature ova Occurs in specialized cells in the ovaries called follicles Follicles contain two types of cells Primary oocyte Cells of the Granulosa layer of small cells that form follicle wall Provides nutrients for developing oocytes

Oogenesis Begins when nutrient follicle surrounding primary oocyte begins to divide Primary oocyte divides, cytoplasm and nutrients move to one of the end poles and form a secondary oocyte Secondary oocyte contains 23 chromosomes Remaining cell, first polar body, receives very little cytoplasm and dies

Oogenesis Follicle cells surrounding secondary oocyte grow rapidly, a fluid filled cavity forms Dominant follicle pushes outward trying to escape ovary Constriction of blood vessels weakens ovarian wall Enzymes weaken the follicle wall from the inside Outer surface of ovary wall bursts and secondary oocyte is released, this is called ovulation

Follicle cells that were surrounding the secondary oocyte stay in the ovary and transform into the corpus luteum CL secretes hormones essential for pregnancy If pregnancy doesn’t happen, it degenerates after ~10 days After its release from the ovary, the secondary oocyte is swept into the end of the Fallopian tube by the fimbria Secondary oocyte is moved along the Fallopian tube by cilia If healthy sperm are present, fertilization occurs

After fertilization in the Fallopian tube Secondary oocyte undergoes another uneven division of cytoplasm and nutrients The cells that retain most of the cytoplasm and nutrients becomes the ovum Other cell becomes the second polar body which deteriorates If fertilization doesn’t occur Secondary oocyte will deteriorate within 24 hours and die When this happens the woman has a menstrual cycle

Draw a flow chart comparing oogenesis and spermatogenesis.. Oogonium Secondary Oocyte + follicle cells Ovum Second Polar Body Primary Oocyte + follicle cells Polar Body

Secondary Spermatocyte Primary Spermatocyte Secondary Spermatocyte Spermatid Spermatogonia

Secondary sex characteristics: Puberty initiates development of secondary sex characteristics and menstrual cycle Secondary sex characteristics: Enlarged breasts Hair growth in armpits and pubic area Wider hips Fat deposits around buttocks and hips Angle from thigh to ankle slightly bent

Menstrual Cycle Includes: Lasts an average of 28 days Oogenesis, ovulation, thickening and shedding of endometrium Lasts an average of 28 days 4 distinct phases Flow phase Follicular phase Ovulatory phase Luteal phase

Flow Phase Marked by the shedding of the endometrium, or menstruation Only phase of cycle that can be determined externally ~5 days for uterus to shed endometrium

Follicular Phase Characterized by the development of follicles within the ovary As follicle develops, estrogen is secreted Estrogen activates the development of secondary sex characteristics and causes thickening of the endometrium Takes place between 6 and 13 of female menstrual cycle

Ovulatory Phase The secondary oocyte bursts from the ovary and follicular cells differentiate into the corpus luteum On average, day 14 of cycle

Luteal Phase Begins when corpus luteum starts to develop Occurs between days 15 and 28 Prepares uterus to receive fertilized egg Estrogen levels begin to drop when oocyte leaves the ovary, levels are restored when corpus luteum forms Corpus luteum secretes estrogen and progesterone Progesterone: Stimulates the endometrium and prepares the uterus for an embryo Inhibits further ovulation Inhibits uterine contraction Firms the cervix to prevent expulsion of the fetus

Luteal Phase If fertilization does not occur Concentrations of estrogen and progesterone will decrease The uterus will start to contract Contraction makes the endometrium pull away from the uterine wall Shedding of the endometrium marks the next flow phase

Interesting Info Each ovary contains 400 000 follicles at puberty Between 12-50 years of age, approx. 400 eggs will mature Older follicles have higher chance of genetic damage

Feedback Control of Menstrual Cycle Hypothalamus-Pituitary regulates estrogen and progesterone Female gonadotropins are follicle stimulating hormone (FSH) and leutinizing hormone (LH) Regulate control of hormones produced by the ovaries Estrogen & progesterone

Puberty is signalled by release of GnRH from the hypothalamus GnRH activates the pituitary gland which produces and stores FSH and LH Follicular phase blood carries FSH secretions to the ovary where follicle development is stimulated Follicles in the ovary secrete estrogen, which starts development of the endometrium Increase in estrogen sends a negative feedback message to the pituitary to turn off secretions of FSH Thus ending the follicular stage At the same time, the increase in estrogen stimulates the LH producing cells of the pituitary LH rises and ovulation occurs

After ovulation: Remaining follicular cells are transformed into a working corpus luteum This begins the luteal phase Luteal Phase: Corpus luteum secrets estrogen and progesterone Estrogen and progesterone build up the endometrium, as they build up a second negative feedback system turns on

Progesterone and estrogen both inhibit the release of FSH and LH Without FSH and LH the corpus luteum deteriorates slowing estrogen and progesterone production The drop in ovarian hormones stimulates the beginning of menstruation