Female Repro

Female Reproductive Structures

Overall Functions of the Female Reproductive System

  • Produces sex hormones

  • Produces functional gametes

  • Protects and supports developing embryo

  • Maintains growing fetus

  • Nourishes newborn infant
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Overview of the Female Reproductive System

Female Gonads

  • Ovaries:

    • Produce gametes (oocytes that mature into ova)

    • Produce hormones

Female Reproductive Tract

  • Uterine Tubes:

    • Deliver oocyte or embryo to the uterus

    • Normal sites of fertilization

  • Uterus:

    • Site of embryonic and fetal development

    • Also site of exchange between maternal and embryonic/fetal bloodstream

Additional Structures

  • Vagina:

    • Site of sperm deposition

    • Birth canal during delivery

    • Passageway for fluids during menstruation

External Genitalia

  • Clitoris:

    • Contains erectile tissue

  • Labia:

    • Contain glands that lubricate the entrance to the vagina

  • Mammary Glands:

    • Produce milk to nourish newborn infant

Female Reproductive Organs

Ovary Structure

  • Paired almond-shaped organs near the lateral wall of the pelvic cavity

  • Dimensions:

    • Typically 5 cm long

    • 2.5 cm wide

    • 8 mm thick

    • Weighs 6–8 g

  • Blood vessels enter at the ovarian hilum:

    • Where ovary attaches to the mesovarium

Ovary Function

  • Three main functions:

    • Production of immature female gametes (oocytes)

    • Secretion of female sex hormones (estrogens and progesterone)

    • Secretion of inhibin (inhibits FSH production in the anterior pituitary gland)

Layers of the Ovaries

  • Germinal Epithelium:

    • Layer of squamous or cuboidal cells covering the ovary

    • Continuous with the visceral peritoneum

  • Tunica Albuginea:

    • Dense connective tissue layer just deep to the germinal epithelium

  • Interior of the Ovary:

    • Cortex (superficial layer where oocytes are produced)

    • Medulla (deep to the cortex)

Female Reproductive System Structures

  • Uterine Tube:

    • Expanded funnel (infundibulum) opens into the pelvic cavity along the surface of the ovary

    • Other end opens into the uterine cavity

  • Uterus:

    • Inferior to the ovaries

    • Usually angled anteriorly above the urinary bladder

Additional Structures

  • Vagina:

    • Extends from the uterus base (cervix) to the exterior

  • External Genitalia:

    • Clitoris (stimulation produces pleasurable sensations associated with female orgasm)

    • Labia

Connective Tissues and Ligaments Stabilizing the Ovary

  • Ovarian Ligament:

    • Extends from uterus to medial surface of ovary

  • Mesovarium:

    • Fold of mesentery; supports and stabilizes ovary

  • Suspensory Ligament:

    • Extends from lateral surface of ovary to pelvic wall

  • Broad Ligament:

    • Extensive mesentery enclosing ovaries, uterine tubes, and uterus

    • Attaches to sides and floor of pelvic cavity

Oogenesis and the Ovarian Cycle

Oogenesis

  • The formation and development of the oocyte

  • Stages:

    • Begins before birth, accelerates at puberty, ends at menopause

    • Nuclear events are the same as with spermatogenesis

Oogenesis Process

  • Distribution of cytoplasm is unequal:

    • Produces one functional secondary oocyte and two or three polar bodies (nonfunctional cells that later disintegrate)

  • Ovary releases a secondary oocyte (not a mature ovum):

    • Meiosis does not complete unless fertilization occurs

Steps in Oogenesis

  1. Mitosis of Oogonium (plural, Oogonia):

    • Oogonia are female reproductive stem cells

    • Mitosis completed prior to birth:

      • For each oogonium, produces one oogonium and one primary oocyte

  2. Meiosis I:

    • Begins between third and seventh month of fetal development:

      • Primary oocytes begin meiosis I, but stop at prophase I until puberty

      • Rising FSH levels trigger start of the ovarian cycle:

      • Each month, some of the primary oocytes are stimulated to complete meiosis I, yielding haploid secondary oocyte and a polar body (secondary oocyte gets the majority of cytoplasm)

  3. Meiosis II:

    • Secondary oocyte begins meiosis II:

      • First polar body may or may not complete meiosis II:

      • Suspended in metaphase II at ovulation

      • If fertilization does not occur, meiosis II does not complete

      • If fertilization occurs, the secondary oocyte divides into a second polar body and a mature ovum (both haploid)

Ovarian Cycle

  • Involves changes in ovarian follicles,

    • Specialized structures where oocyte growth and meiosis I occur

    • About 2 million primordial follicles exist at birth (each containing a primary oocyte)

    • By puberty, only about 400,000 primordial follicles remain (others degenerated in a process called atresia)

    • Each month, FSH stimulates the development of several follicles

Stages of the Ovarian Cycle

  1. Primordial Follicle in Egg Nest:

    • Primordial follicle:

    • Inactive primary oocyte surrounded by a simple squamous layer of follicle cells

  2. Formation of Primary Follicles:

    • Follicular cells enlarge, divide, and form several layers around the primary oocyte:

      • Follicular cells now called granulosa cells

      • Zona pellucida: Region that develops around the oocyte

      • Thecal cells: Layer of cells that form around the follicle:

      • Thecal and granulosa cells work together to produce estrogen

  3. Formation of Secondary Follicles:

    • Follicle wall thickens and follicular cells secrete fluid:

      • Fluid-filled pockets expand and separate the inner and outer layers of the follicle

  4. Formation of Tertiary Follicle:

    • Occurs about day 10–14 of cycle:

      • One secondary follicle becomes a tertiary follicle or mature graafian follicle (roughly 15 mm in diameter)

      • Expanded central chamber (antrum) is filled with follicular fluid:

      • Oocyte projects into the antrum

      • Granulosa cells form a protective layer (corona radiata) around the secondary oocyte

  5. Ovulation:

    • Tertiary follicle releases secondary oocyte and corona radiata into the pelvic cavity:

      • Marks follicular phase end and start of luteal phase

  6. Formation of Corpus Luteum:

    • Empty tertiary follicle collapses:

      • Remaining granulosa cells proliferate

      • Secrete progesterone and estrogens:

      • Progesterone stimulates maturation of the uterine lining

  7. Formation of Corpus Albicans:

    • Knot of pale scar tissue produced by fibroblasts:

      • Formed by degeneration of the corpus luteum when fertilization does not occur after 12 days:

      • Marks the end of the ovarian cycle

Uterine Tubes and the Uterus

Uterine Tubes

  • Hollow, muscular structures ~13 cm long:

    • Lined with ciliated epithelium

    • Distal portion connects to the uterus

  • Infundibulum:

    • Funnel-like expansion adjacent to the ovary:

    • Has numerous fingerlike projections (fimbriae) that extend into the pelvic cavity and drape over the surface of the ovary (but no physical connection)

    • Inner surface lined with cilia that beat toward the lumen

Oocyte Transport

  • Involves combination of ciliary movement and peristaltic contraction of smooth muscle in the uterine tube:

    • Takes 3–4 days for a secondary oocyte to travel from infundibulum to the uterine cavity:

    • Fertilization must occur within the first 12–24 hours after ovulation

Uterus

  • Hollow, muscular organ with dimensions (when not pregnant):

    • ~7.5 cm long

    • Maximum diameter of 5 cm

    • Weight 30–40 g

    • Capable of great changes in size and shape:

    • Provides mechanical protection, nutritional support, and waste removal for embryo (weeks 1–8) and fetus (>8 weeks)

    • Contractions in the muscular wall are important in delivering the fetus at birth

Layers of the Uterine Wall

  • Perimetrium:

    • Outer surface

    • Incomplete serosa continuous with the peritoneal lining

  • Myometrium:

    • Thick muscular middle layer:

    • Smooth muscle layer provides force for childbirth

  • Endometrium:

    • Glandular inner lining whose characteristics change with each uterine cycle

The Uterine Cavity and Cervix

  • Uterine Cavity or Uterine Lumen:

    • Large, superior cavity continuous with the isthmus of the uterine tube

  • Internal Os:

    • Opening connecting the uterine cavity to the cervical canal

  • Cervical Canal:

    • Constricted passageway at the inferior end of the uterine cavity:

    • Begins at internal os; ends at external os

  • External Os:

    • Curving vaginal opening into the uterus

Regions of the Uterus

  • Fundus:

    • Rounded portion superior to the openings of the uterine tubes

  • Body:

    • Largest portion of the uterus (2/3 of the organ):

    • Ends at the constriction encircling the internal os

  • Cervix:

    • Inferior portion of the uterus:

    • Surrounds the cervical canal:

    • Projects into the vagina

The Uterine Cycle (Menstrual Cycle)

  • Monthly changes in the functional zone of the uterus in response to sex hormone levels:

    • Averages 28 days in length (range 21–35 days)

    • First cycle (menarche) begins ~11–12 years of age

    • Cycles continue until menopause (~45–55 years of age)

    • Regularity may be interrupted by illness, stress, starvation, or pregnancy

Phases of the Uterine Cycle

  1. Menses:

    • Degeneration of the functional zone of the endometrium:

      • Caused by constricted spiral arteries:

      • Reduces endometrial blood flow:

      • Weakened arterial walls rupture:

        • Blood and degenerating tissues enter the uterine lumen:

        • Process of endometrial sloughing (menstruation): lasts ~1–7 days:

          • ~35–50 mL blood lost

  2. Proliferative Phase:

    • Uterine gland basal cells multiply and spread, restoring uterine epithelium:

      • Stimulated and sustained by estrogens secreted from developing ovarian follicles:

      • Builds the functional zone to several millimeters thick:

        • Uterine glands manufacture glycogen-rich mucus:

        • Can be metabolized by an early embryo

  3. Secretory Phase:

    • Uterine glands enlarge:

      • Increased secretion of glycoproteins to support embryo:

      • Arteries supplying uterine wall elongate and spiral through the functional zone:

        • Stimulated by both progesterone and estrogens from the corpus luteum:

        • Begins at ovulation and lasts until menses

Vagina and External Genitalia

Vagina

  • Elastic, muscular tube extends from the cervix to the vestibule (space bordered by the female external genitalia):

    • Typically 7.5–9 cm (3–3.6 in.) long:

    • Variable diameter (highly distensible)

Functions of the Vagina

  • Passageway for menstrual fluids:

  • Receives penis during sexual intercourse and holds spermatozoa prior to their passage into the uterus:

  • Forms inferior portion of birth canal

Components of the Vagina

  • Vaginal Canal:

    • Internal passageway:

    • Lined by nonkeratinized stratified squamous epithelium

  • Fornix:

    • Shallow recess in the vagina surrounding the tip of the cervix

  • Rugae:

    • Folds formed by the vaginal lining when relaxed

Additional Components

  • Hymen:

    • Elastic epithelial fold that usually partially blocks entrance to the vagina:

    • Frequently absent:

      • Stretched or torn during intercourse, tampon use, or heavy physical exercise

Vulva or Pudendum

  • Area containing the female external genitalia:

  • Vestibule:

    • Central space bounded by small folds called labia minora (singular, labium minorus)

  • Lesser Vestibular Glands:

    • Secrete onto the vestibular surface, keeping it moist

  • Greater Vestibular Glands (Bartholin’s Glands):

    • Activated during sexual arousal:

    • Mucous glands that discharge into the vestibule:

      • Same embryonic origins as the bulbourethral glands of males

External Structures

  • Vestibular Bulbs:

    • Masses of erectile tissue on either side of the vaginal entrance:

    • Have the same embryonic origin as the corpus spongiosum of the penis

  • Mons Pubis:

    • Bulge of adipose tissue deep to the skin and superficial to the pubic symphysis

  • Clitoris:

    • Projects into the vestibule:

    • Contains erectile tissue comparable to the corpora cavernosa and corpus spongiosum of the penis

  • Prepuce or Hood:

    • Extensions of the labia minora encircling the body of the clitoris

  • Labia Majora (singular, labium majus):

    • Prominent folds of skin encircling the labia minora and adjacent structures

Mammary Glands

  • Provide nourishment (milk) for developing infant:

  • Milk production (lactation) controlled by hormones released by the reproductive system and the placenta:

  • Located on the anterior chest, directly over the pectoralis major muscle

Structure of a Mammary Gland

  • Embedded in the subcutaneous tissue of the pectoral fat pad deep to the skin:

    • Suspensory Ligaments of the Breast:

    • Bands of dense connective tissue:

      • Surround the duct system and form partitions between lobes and lobules

  • Glandular Tissue divided into lobes:

    • Each lobe has several secretory lobules:

    • Each lobule is composed of secretory alveoli

Detailed Structure

  • Ducts from the lobules converge into one lactiferous duct per lobe:

    • Each lactiferous duct expands near the nipple to form a lactiferous sinus:

Nipple and Areola

  • Nipple:

    • Conical projection where 15–20 lactiferous sinuses open onto the body surface:

  • Areola:

    • Reddish-brown skin around the nipple:

    • Grainy texture from sebaceous glands deep to the surface

Regulation of Female Reproduction

  1. Production of LH

  2. Production and secretion of FSH

  3. Secretion of LH:

    • After day 10

    • Before day 10:

      • Follicle development

      • Secretion of inhibin

      • Secretion of estrogens

      • Meiosis I completion

      • Ovulation

      • Corpus luteum formation

  4. Secretion of progesterone

  5. Release of Gonadotropin-Releasing Hormone (GnRH):

    • Negative feedback onto anterior lobe of pituitary gland

    • Effects on CNS:

      • Stimulation of bone and muscle growth

      • Establishment and maintenance of female secondary sex characteristics

      • Maintenance of accessory glands and organs

      • Stimulation of endometrial growth and secretion

Clinical Module: Reproductive System Disorders

Prostate Disorders

  • Benign Prostatic Hypertrophy (BPH):

    • Occurs spontaneously in men, typically over age 50:

    • Declining testosterone production and the presence of estrogen may stimulate growth:

      • Can constrict prostatic urethra and affect urination

  • Prostate Cancer:

    • Second most common cause of cancer deaths in males:

    • Can be screened for by blood tests for prostate-specific antigen (PSA):

      • Treatment is radiation or surgical removal of prostate (prostatectomy)

Testicular Cancer

  • Most common cancer among males ages 15–35:

    • Occurs at a relatively low rate (3 cases per 100,000 males per year):

    • More than 95 percent result from abnormal spermatocytes or spermatogonia:

      • Treatment is a combination of orchiectomy (testes removal) and chemotherapy:

      • Survival rate near 95 percent as a result of early diagnosis and improved treatment

Breast Disorders

  • Changing hormone levels can cause inflammation of the mammary gland tissues:

    • Cysts:

    • Formed if inflamed lobules are walled off by scar tissue:

      • Fibrocystic Disease:

      • Condition when clusters of cysts can be felt as discrete masses:

        • Benign condition, but may need biopsy to distinguish masses from breast cancer

  • Breast Cancer:

    • Malignant, metastasizing tumor of mammary gland:

    • Leading cause of death in women ages 35–45:

      • Most common in women over age 50:

      • Notable risk factors include:

        • Family history of breast cancer

        • First pregnancy after age 30

        • Early menarche or late menopause:

        • Treatment includes surgery, radiation, chemotherapy, and hormones:

          • Surgical removal may involve removal of part or all of mammary gland as well as axillary lymph nodes

Ovarian Cancer

  • 3rd most common reproductive cancer among women but most dangerous:

    • Seldom diagnosed in early stages:

    • 1-in-70 chance of developing during female lifetime:

      • Treatment includes chemotherapy, radiation, and surgery:

      • Prognosis:

        • For cancers originating in the general ovarian tissues or abnormal oocytes, relatively good prognosis:

        • For 85 percent of ovarian cancers that are carcinomas (epithelial cancers), sustained remission in only 1/3 of cases

Cervical Cancer

  • Most common cancer of the reproductive system in women ages 15–34:

    • Of ~12,000 diagnosed each year with invasive cervical cancer, 1/3 die from the condition:

    • Another 35,000 cases per year are diagnosed with a less aggressive form:

      • Human Papillomavirus (HPV) is responsible for 75 percent of cervical cancers:

      • Vaccine (Gardasil) protects against four types of HPV

Sexually Transmitted Diseases (STDs) / Sexually Transmitted Infections (STIs)

  • Transferred from person to person primarily or exclusively by sexual intercourse:

    • Consequences range from inconveniences to lethal:

    • Include at least two dozen bacterial, viral, and fungal infections:

    • Examples: Chlamydia, AIDS

  • Incidence increasing in the U.S. since 1984:

    • Estimated 20 million new cases each year:

    • Almost 50 percent in persons aged 15–24:

    • Contributors include poverty, intravenous drug use, prostitution, and drug-resistant pathogens.