Reproductive System

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Reproductive System

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Cell Cycle

• Produces gametes by meiosis

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Cell Cycle

• Meiosis reduces the number of chromosomes in half

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Cell Cycle

• Gametes have only 23 chromosomes

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Homologous Chromosomes

• 2 chromosomes that make up a chromosome pair in
  cells

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Homologous Chromosomes

• Contain similar genes

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Homologous Chromosomes

• The exception is the sex chromosomes

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Homologous Chromosomes

• The female contains two X chromosomes

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Homologous Chromosomes

• The male has an X and a Y chromosome

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Homologous Chromosomes

• The other 22 pairs of chromosomes are called
  autosomes

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Diploid Cell

• A cell with a full set of chromosomes

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Haploid Cell

• One with only one chromosome from each pair

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Haploid Cell

• Gametes are the only haploid cells

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Haploid Cell

• Eggs and spermatoza

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Male Reproductive System

• Testes
• A system of ducts
• Several supporting structures
• Penis

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Scrotum

• Cutaneous outpouching of the abdomen that
  supports the testes

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Scrotum

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

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Testes

• Paired oval-shaped glands in the scrotum

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Testes

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

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Testes

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

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Sertoli Cells

• Nourish spermatocytes, spermatids, and spermatozoa

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Sertoli Cells

• Control movements of spermatogenic cells

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Sertoli Cells

• Controls the release of spermatozoa into the
  lumen of the seminiferous tubule

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Sertoli Cells

• Secretes fluid for sperm transport and the
  hormone inhibin

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Sertoli Cells

• Inhibin decreases FSH when the rate of
  spermatogenesis is too high

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Testes

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

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Spermatogenesis

• Process by which seminiferous tubules of the
  testes produce sperm

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Spermatogenesis

• Spermatogonia stem cells

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Spermatogenesis

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

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Spermatogenesis

• Diploid primary spermatocytes undergo meiosis I
  forming haploid secondary spermatocytes

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Spermatogenesis

• Meiosis II results in haploid spermatids

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Spermatogenesis

• Spermiogenesis maturation of the spermatids
  into spermatozoa

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Mature Sperm

• Consist of a head, midpiece, and tail

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Mature Sperm

• The head contains a specialized lysosome called
  an acrosome

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Mature Sperm

• The acrosome has an enzyme that helps penetrate
  the egg

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Mature Sperm

• The midpiece is rich in mitochondria for ATP
  production

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Mature Sperm

• ATP is essential for the motility of flagellum

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Mature Sperm

• They are produced at the rate of about 100-300
  million per day

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Mature Sperm

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

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Hormonal Control of Spermatogenesis

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

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Hormonal Control of Spermatogenesis

• FSH initiates spermatogenesis

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Hormonal Control of Spermatogenesis

• LH assists spermatogenesis and stimulates the
  production of testosterone by the Leydig cells

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Testosterone

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

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Testosterone

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

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Testosterone

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

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Testosterone

• It reduces LH secretion, which decreases
  testosterone production

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Secondary Male Sex Characteristics

• Wide shoulders

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Secondary Male Sex Characteristics

• Narrow hips

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Secondary Male Sex Characteristics

• Male hair patters

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Secondary Male Sex Characteristics

• Thick and oily skin

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Secondary Male Sex Characteristics

• Enlarged larynx with a deeper voice

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Ducts

• The duct system of the testes includes the
• Seminiferous tubules
• Straight tubules
• Rete Testis
• Epididymis
• Ductus Deferens
• Ejaculatory Duct
• Urethra

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Epididymis

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

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Epididymis

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

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Ductus Epididymis

• Lined by stereocilia

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Ductus Epididymis

• Site of sperm maturation and storage

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Ductus Epididymis

• Sperm may remain in storage here for at least a
  month

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Vas Deferens

• Stores sperm and propels them toward the urethra
  during ejaculation

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Ejaculatory Ducts

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

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Ejaculatory Ducts

• Function to eject spermatozoa into the prostatic
  urethra

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Male urethra

• Serves as a passageway for semen and urine

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Seminal Vesicles

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

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Seminal Vesicles

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

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Seminal Vesicles

• The fructose is for ATP production by sperm

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Prostate Gland

• Secretes a milky, slightly acidic fluid

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Bulbourethral Glands

• Secretes mucus for lubrication and an alkaline
  substance that neutralizes acid

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Semen

• Average volume 2.75 ml

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Semen

• Contains 50-150 million spermatozoa/ml

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Semen

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

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Semen

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

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Penis

• Male organ of copulation that consists of a
• Root
• Body
• Glans penis
• foreskin

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Penis

• Spongy tissue in shaft composed of
• Two dorsal corpora cavernosa
• Ventral corpos spongiosum

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Penis

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

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Penis

• The blood sinuses become filled with blood during
  erection

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Erection

• Mediated by a parasympathetic reflex

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Erection

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

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Erection

• This vasodilation increases blood flow into the
  penis

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Ejaculation

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

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Female Reproductive System

• Ovaries
• Uterine tubes
• Uterus
• Vagina
• Vulva
• Mammary Glands

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Ovaries

• Paired glands that are homologous to the testes

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Ovaries

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

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Ovarian Cortex

• Contain ovarian follicles and consists of oocytes
  in various stages of development

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Primordial follicles

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

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Primordial follicles

• Contain 46 chromosomes stuck in prophase of
  meiosis 1

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Primordial follicles

• A woman is born with 2 million primordial
  follicles

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Primordial follicles

• During childhood, most undergo atresia

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Primordial follicles

• By puberty, only 400,000 are left

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Primordial follicles

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

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Primary follicles

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

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Primary follicles

• These epithelial cells are called granulosa cells

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Primary follicles

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

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Primary follicles

• Outside the granulosa cells are two layers of
  connective tissue called
• Theca externa
• Theca interna

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Primary follicles

• Many primaries undergo atresia

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Primary follicles

• Some become secondary follicles

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Secondary Follicles

• Have a fluid filled antrum

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Secondary follicles

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

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Secondary follicles

• One follicle will become the dominant follicle-
  the Graafian follicle

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Graafian Follicle

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

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Graafian Follicle

• Its now called the secondary oocyte

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Graafian Follicle

• The follicle expel the secondary oocyte by a
  process called ovulation

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Immature ovum

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

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Corpus luteum

• Contains the remnants of an ovulated follicle and
  produces
• Progesterone
• Estrogen
• Relaxin
• Inhibin

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Corpus luteum

• It eventually degenerates into a corpus albicans

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Oogenesis

• Occurs in the ovaries

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Oogenesis

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

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Oogenesis

• Meisosis II is not complete until fertilization

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Ovarian Medulla

• Contains
• Blood vessels
• Lymphatics
• Nerves

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Uterine Tube

• Transport ova from the ovaries to the uterus

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Uterine Tube

• Normal sites of fertilizaiton

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Uterine Tube

• Fimbriae are projections of the tubes that help
  capture the ovulated immature ovum

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Uterine Tube

• The fallopian tube is the usually the site of
  fertilization

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Uterine Tube

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

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Uterus

• An organ the size and shape of an inverted pear

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Uterus

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

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Uterus

• Cervix connects the vaginal cavity to the
  uterine cavity

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Uterus

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

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Histology of the Uterus

1. Perimetrium
2. Myometrium
3. Endometrium

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Perimetrium

• Part of the visceral peritoneum

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Myometrium

• Consists of three muscle layers and has oxytocin
  receptors

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Endometrium

• Divided into the
• Stratum Functionalis
• Stratum Basalis

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Endometrium

• Spiral arteries supply the endometrium

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Cervix

• Secretory cells of the cervix produce a cervical
  mucus

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Cervix

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

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Cervix

• During most of the menstrual cycle the mucus is
  thick

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Vagina

• 10 cm in the adult

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Vagina

• Functions as a passageway for spermatozoa and the
  menstrual flow

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Vagina

• It is acidic in order to inhibit microorganisms
  and sperm

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Vagina

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

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Vulva

• External genitalia of the female

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Vulva

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

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Vulva

• 2. Labia majora covered with hair

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Vulva

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

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Vulva

• 4. Clitoris homologous to the penis

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Vulva

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

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Vulva

• 6. Vaginal orifice

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Vulva

• 7. Urethral orifices between the clitoris and
  the vaginal orifice

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Vulva

• 8. Hymen

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Mammary Glands

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

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Mammary Glands

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

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Mammary Glands

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

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Mammary Glands

• Function to synthesize milk and secretion and
  ejection of milk (lactation)

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Mammary Glands

• Areola is the pigmented skin that surrounds the
  nipple

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Mammary Glands

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

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Phases of the Female Reproductive Cycle

1. Menstrual cycle
2. Preovulatory phase
3. Ovulation
4. Postovulatory phase

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Menstrual Cycle

• First five days of cycle

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Menstrual Cycle

• About 20 small follicles in each ovary begin to
  develop

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Menstrual Cycle

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

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Menstrual Cycle

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

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Preovulatory phase

• Between menstruation and ovulation

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Preovulatory phase

• Lasting from days 6-13 in a 28 day cycle

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Preovulatory phase

• Primary follicles develop into secondary follicles

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Preovulatory phase

• A single secondary follicle develops into a
  Graafian or mature follicle

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Preovulatory phase

• Maturing follicles secrete estrogen

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Preovulatory phase

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

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Preovulatory phase

• Estrogen stimulates endometrial repair a new
  stratum functionalis is formed

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Ovulation

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

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Ovulatation

• LH transforms the ruptured follicle into the
  corpus luteum

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Ovulation

• Occurs on day 14

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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

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Ovulation

• GnRH promotes release of FSH and LH

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Ovulation

• LH surge brings about the ovulation

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Ovulation

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

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Ovulation

• Clear cervical mucus due to high estrogen

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Ovulation

• Corpus luteum secretes estrogens and progesterone
  due to LH

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Postovulatory phase

• Days 15-28

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Postovulatory phase

• Time between ovulation and the onset of the next
  menstrual period

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Postovulatory phase

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

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Postovulatory phase

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

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Postovulatory phase

• So Corpus luteum loses its support

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Postovulatory phase

• The copus luteum degenerates and becomes the
  corpus albicans

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Postovulatory phase

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

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Postovulatory phase

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

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Postovulatory phase

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

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Postovulatory phase

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

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Postovulatory phase

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

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Postovulatory phase

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

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Postovulatory phase

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

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Postovulatory phase

• Endometrium thickens in anticipation of
  implantation