Reproductive System

Cell Cycle Produces gametes by meiosis

Cell Cycle Meiosis reduces the number of chromosomes in half

Cell Cycle Gametes have only 23 chromosomes

Homologous Chromosomes 2 chromosomes that make up a chromosome pair in cells

Homologous Chromosomes Contain similar genes

Homologous Chromosomes The exception is the sex chromosomes

Homologous Chromosomes The female contains two X chromosomes

Homologous Chromosomes The male has an X and a Y chromosome

Homologous Chromosomes The other 22 pairs of chromosomes are called autosomes

Diploid Cell A cell with a full set of chromosomes

Haploid Cell One with only one chromosome from each pair

Haploid Cell Gametes are the only haploid cells

Haploid Cell Eggs and spermatoza

Male Reproductive System Testes A system of ducts Several supporting structures Penis

Scrotum Cutaneous outpouching of the abdomen that supports the testes

Scrotum Internally a vertical septum divides it into two sacs, each containing a single testis

Testes Paired oval-shaped glands in the scrotum

Testes Contain seminiferous tubules ( in which sperm cells are made)

Testes Sertoli Cells - Embedded among the spermatogenic cells in the tubules

Sertoli Cells Nourish spermatocytes, spermatids, and spermatozoa

Sertoli Cells Control movements of spermatogenic cells

Sertoli Cells Controls the release of spermatozoa into the lumen of the seminiferous tubule

Sertoli Cells Secretes fluid for sperm transport and the hormone inhibin

Sertoli Cells Inhibin decreases FSH when the rate of spermatogenesis is too high

Testes Leydig cells – found in the spaces between adjacent seminiferous tubules secrete testosterone

Spermatogenesis Process by which seminiferous tubules of the testes produce sperm

Spermatogenesis Spermatogonia – stem cells

Spermatogenesis Spermatogonia undergo mitosis to produce future stem cells and primary spermatocytes

Spermatogenesis Diploid primary spermatocytes undergo meiosis I forming haploid secondary spermatocytes

Spermatogenesis Meiosis II results in haploid spermatids

Spermatogenesis Spermiogenesis – maturation of the spermatids into spermatozoa

Mature Sperm Consist of a head, midpiece, and tail

Mature Sperm The head contains a specialized lysosome called an acrosome

Mature Sperm The acrosome has an enzyme that helps penetrate the egg

Mature Sperm The midpiece is rich in mitochondria for ATP production

Mature Sperm ATP is essential for the motility of flagellum

Mature Sperm They are produced at the rate of about million per day

Mature Sperm Have a life expectancy of 48 hours within the female reproductive tract

Hormonal Control of Spermatogenesis At puberty Gonadotropin releasing hormone increases, which stimulates the A.P. secretion of FSH and LH

Hormonal Control of Spermatogenesis FSH initiates spermatogenesis

Hormonal Control of Spermatogenesis LH assists spermatogenesis and stimulates the production of testosterone by the Leydig cells

Testosterone Controls the growth, development, functioning, and maintenance of sex organs

Testosterone Stimulates bone growth, protein anabolism, increases in muscle size, and sperm maturation

Testosterone It increases libido and stimulates the development of secondary sex characteristics

Testosterone It reduces LH secretion, which decreases testosterone production

Secondary Male Sex Characteristics Wide shoulders

Secondary Male Sex Characteristics Narrow hips

Secondary Male Sex Characteristics Male hair patters

Secondary Male Sex Characteristics Thick and oily skin

Secondary Male Sex Characteristics Enlarged larynx with a deeper voice

Ducts The duct system of the testes includes the 1.Seminiferous tubules 2.Straight tubules 3.Rete Testis 4.Epididymis 5.Ductus Deferens 6.Ejaculatory Duct 7.Urethra

Epididymis Comma-shaped organ that lies along the posterior border of the testis

Epididymis Sperm are transported out of the testes through the ductus epididymis

Ductus Epididymis Lined by stereocilia

Ductus Epididymis Site of sperm maturation and storage

Ductus Epididymis Sperm may remain in storage here for at least a month

Vas Deferens Stores sperm and propels them toward the urethra during ejaculation

Ejaculatory Ducts Formed by the union of the ducts from the seminal vesicles and ducti deferens

Ejaculatory Ducts Function to eject spermatozoa into the prostatic urethra

Male urethra Serves as a passageway for semen and urine

Seminal Vesicles Secretes a viscous alkaline fluid that contains fructose that nourish and promote the fertilizing capability of sperm

Seminal Vesicles The alkaline fluid helps neutralize acid in the male urethra and female reproductive tract

Seminal Vesicles The fructose is for ATP production by sperm

Prostate Gland Secretes a milky, slightly acidic fluid

Bulbourethral Glands Secretes mucus for lubrication and an alkaline substance that neutralizes acid

Semen Average volume 2.75 ml

Semen Contains million spermatozoa/ml

Semen The average sperm count has declined from 113 million/ml to 66 million/ml over the past 44 years

Semen May be due to estrogens in meat, marijuana, environmental toxins, alcohol, and lead exposure

Penis Male organ of copulation that consists of a 1.Root 2.Body 3.Glans penis 4.foreskin

Penis Spongy tissue in shaft composed of 1.Two dorsal corpora cavernosa 2.Ventral corpos spongiosum

Penis Arterioles (which are normally constricted) supply blood to blood sinuses

Penis The blood sinuses become filled with blood during erection

Erection Mediated by a parasympathetic reflex

Erection Neurons and vascular endothelial cells release nitric oxide which leads to arteriolar smooth muscle relaxation

Erection This vasodilation increases blood flow into the penis

Ejaculation Propulsion of semen from the urethra to the exterior is a sympathetic reflex

Female Reproductive System Ovaries Uterine tubes Uterus Vagina Vulva Mammary Glands

Ovaries Paired glands that are homologous to the testes

Ovaries Located in the upper pelvic cavity on either side of the uterus

Ovarian Cortex Contain ovarian follicles and consists of oocytes in various stages of development

Primordial follicles Contain the primary oocyte surrounded by a single layer of flattened epithelial cells

Primordial follicles Contain 46 chromosomes stuck in prophase of meiosis 1

Primordial follicles A woman is born with 2 million primordial follicles

Primordial follicles During childhood, most undergo atresia

Primordial follicles By puberty, only 400,000 are left

Primordial follicles Each month, about 20 primordial follicles mature into primary follicles

Primary follicles Primary oocyte surrounded by one to several layers of cuboidal epithelial cells that make estrogen

Primary follicles These epithelial cells are called granulosa cells

Primary follicles In between the oocyte and granulosa cells is a glycoprotein called the zona pelucida

Primary follicles Outside the granulosa cells are two layers of connective tissue called 1.Theca externa 2.Theca interna

Primary follicles Many primaries undergo atresia

Primary follicles Some become secondary follicles

Secondary Follicles Have a fluid filled antrum

Secondary follicles As the menstrual cycle progresses toward midcycle all of the secondaries undergo atresia except one

Secondary follicles One follicle will become the dominant follicle- the Graafian follicle

Graafian Follicle The primary oocyte will complete meiosis I and go through part of meiosis II, but pause at metaphase II

Graafian Follicle It’s now called the secondary oocyte

Graafian Follicle The follicle expel the secondary oocyte by a process called ovulation

Immature ovum Surrounding it is the zona pelucida and a layer of follicular cells called the corona radiata

Corpus luteum Contains the remnants of an ovulated follicle and produces 1.Progesterone 2.Estrogen 3.Relaxin 4.Inhibin

Corpus luteum It eventually degenerates into a corpus albicans

Oogenesis Occurs in the ovaries

Oogenesis It results in the formation of a single haploid secondary oocyte

Oogenesis Meisosis II is not complete until fertilization

Ovarian Medulla Contains 1.Blood vessels 2.Lymphatics 3.Nerves

Uterine Tube Transport ova from the ovaries to the uterus

Uterine Tube Normal sites of fertilizaiton

Uterine Tube Fimbriae – are projections of the tubes that help capture the ovulated immature ovum

Uterine Tube The fallopian tube is the usually the site of fertilization

Uterine Tube Ciliated cells and peristaltic contractions help move a secondary oocyte toward the uterus

Uterus An organ the size and shape of an inverted pear

Uterus Functions in the transport of spermatozoa, menstruation, implantation of a fertilized ovum, development of a fetus during pregnancy, and labor

Uterus Cervix – connects the vaginal cavity to the uterine cavity

Uterus Cervix – firm unless it is softened by relaxin during labor and delivery

Histology of the Uterus 1.Perimetrium 2.Myometrium 3.Endometrium

Perimetrium Part of the visceral peritoneum

Myometrium Consists of three muscle layers and has oxytocin receptors

Endometrium Divided into the 1.Stratum Functionalis 2.Stratum Basalis

Endometrium Spiral arteries supply the endometrium

Cervix Secretory cells of the cervix produce a cervical mucus

Cervix At mid cycle the mucus is thin and receptive to sperm

Cervix During most of the menstrual cycle the mucus is thick

Vagina 10 cm in the adult

Vagina Functions as a passageway for spermatozoa and the menstrual flow

Vagina It is acidic in order to inhibit microorganisms and sperm

Vagina The vaginal orifice in virgins is partially covered by the hymen

Vulva External genitalia of the female

Vulva It consists of 1. Mons pubs – rounded fatty eminence overlying the pubic symphysis

Vulva 2. Labia majora – covered with hair

Vulva 3. Labia minora – thinner folds that are devoid of hair, they atrophy after menopause

Vulva 4. Clitoris – homologous to the penis

Vulva 5. Vestibule – cleft between labia minora where vaginal orifice opens to the outside

Vulva 6. Vaginal orifice

Vulva 7. Urethral orifices – between the clitoris and the vaginal orifice

Vulva 8. Hymen

Mammary Glands Milk producing glands that lie over the pectoralis major and serratus anterior muscle

Mammary Glands Milk secreting cells (alveoli) are clustered in small compartments (lobules) within the breasts

Mammary Glands 1.Alveoli 2.Mammary ducts 3.Lactiferous ducts 4.Lactiferous sinuses 5.Nipple

Mammary Glands Function to synthesize milk and secretion and ejection of milk (lactation)

Mammary Glands Areola is the pigmented skin that surrounds the nipple

Mammary Glands Develop at puberty under the stimulation of rising estrogen and progesterone levels

Phases of the Female Reproductive Cycle 1.Menstrual cycle 2.Preovulatory phase 3.Ovulation 4.Postovulatory phase

Menstrual Cycle First five days of cycle

Menstrual Cycle About 20 small follicles in each ovary begin to develop

Menstrual Cycle Stratum functionalis layer of the endometrium is shed discharging blood, tissue fluid, mucus, and epithelial cells

Menstrual Cycle It is shed due to declining progesterone at the end of the previous cycle

Preovulatory phase Between menstruation and ovulation

Preovulatory phase Lasting from days 6-13 in a 28 day cycle

Preovulatory phase Primary follicles develop into secondary follicles

Preovulatory phase A single secondary follicle develops into a Graafian or mature follicle

Preovulatory phase Maturing follicles secrete estrogen

Preovulatory phase The mature follicle continues to increase its estrogen production due to increasing levels of LH

Preovulatory phase Estrogen stimulates endometrial repair; a new stratum functionalis is formed

Ovulation Rupture of the Graafian or mature follicle with release of the secondary oocyte into the pelvic cavity

Ovulatation LH transforms the ruptured follicle into the corpus luteum

Ovulation Occurs on day 14

Ovulation The high levels of estrogen during the last part of the preovulatory phase exerts a positive feedback on LH and GnRH to cause ovulation

Ovulation GnRH promotes release of FSH and LH

Ovulation LH surge brings about the ovulation

Ovulation Increased body temperature due to progesterone, which increases just prior to ovulation

Ovulation Clear cervical mucus due to high estrogen

Ovulation Corpus luteum secretes estrogens and progesterone due to LH

Postovulatory phase Days 15-28

Postovulatory phase Time between ovulation and the onset of the next menstrual period

Postovulatory phase Estrogen and progesterone are secreted in large quantities by the corpus luteum

Postovulatory phase If fertilization and implantatin do not occur, estrogen and progesterone secreted by the corpus luteum inhibit LH

Postovulatory phase So Corpus luteum loses its support

Postovulatory phase The copus luteum degenerates and becomes the corpus albicans

Postovulatory phase The decreased levels of estrogen and progesterone initiatates another menstrual phase

Postovulatory phase Because estrogen and progesterone levels drop, there is less negative feedback on the Hyp. and A.P.

Postovulatory phase FSH and LH begin to rise a bit at the end of the cycle, causing another round of follicular development (about 20)

Postovulatory phase If fertilization and implantation do occur, the corpus luteum is maintained until the placenta takes over

Postovulatory phase Corpus luteum is maintained by human chorionic gonadotropin (hCG) from the developing placenta

Postovulatory phase The corpus luteum secretes estrogens and progesterones to support pregnancy and breast development for lactation

Postovulatory phase Once the placenta begins secreting estrogen and progesterone, the role of corpus luteum becomes minor

Postovulatory phase Endometrium thickens in anticipation of implantation