final study guide

Intermediate Human Physiology Dr. Brinn Reproductive System Outline

Sexual reproduction - process by which organisms produce offspring from the union of germ cells

called gametes.

• After male gamete (sperm cell) unites with female gamete (oocyte) - an event called

fertilization - the resulting cell contains one set of chromosomes from each parent

• Males and females have distinct reproductive organs that are adapted for producing

gametes; facilitating fertilization; and, in females, sustaining growth of embryo and

fetus during pregnancy.

The organs of the male and female reproductive systems can be grouped by function.

• The gonads—testes in males and ovaries in females—produce gametes and secrete sex

hormones. Various ducts then store and transport the gametes, and accessory sex glands

produce substances that protect the gametes and facilitate their movement.

• Finally, supporting structures, such as the penis in males and the vagina and uterus in females,

assist the delivery of gametes. The uterus is also the site for the development of the embryo

and fetus.

I. Reproductive Cell Division

A. Somatic cells and gametes have different numbers of chromosomes

1. Somatic - include any cell in the body other than a gamete

a. 23 pairs (46 total)

b. Diploid (2n)

2. Gametes

a. 23 only

b. Haploid (1n)

B. There are two stages of meiosis

1. Meiosis I - begins once chromosomal replication is complete

a. Consists of 4 phases

I. Prophase I

• extended phase in which the chromosomes shorten and thicken

• nuclear envelope and nucleoli disappear

• meiotic spindle forms

• in addition, the sister chromatids of each pair of homologous

chromosomes pair off, an event called synapsis

• The resulting four chromatids form a structure called a tetrad.

II. Metaphase I

• tetrads formed by the homologous pairs of chromosomes line up

along the metaphase plate of the cell, with homologous chromosomes

side by side

III. Anaphase I

• members of each homologous pair of chromosomes separate as they

are pulled to opposite poles of the cell by the microtubules attached to

the centromeres.

• Paired sister chromatids, held by a centromere, remain together.

IV. Telophase I and cytokinesis of meiosis are similar to telophase and

cytokinesis of mitosis.

• The net effect of meiosis I is that each resulting cell contains the

haploid number of chromosomes because it contains only one

member of each pair of the homologous chromosomes present in the

starting cell.

2. Meiosis II - similar to those that occur during mitosis; the centromeres split, and the

sister chromatids separate and move toward opposite poles of the cell.

a. Also 4 phases

I. Prophase II

II. Metaphase II

III. Anaphase II

IV. Telophase II

*In summary, meiosis I begins with a diploid starting cell and ends

with two cells, each with the haploid number of chromosomes.

During meiosis II, each of the two haploid cells formed during

meiosis I divides; the net result is four haploid gametes that are

genetically different from the original diploid starting cell.

II. Male Reproductive System

A. The scrotum - protects the testes and regulates their temperature

B. The testes - produce sperm and secrete hormones

C. Seminiferous tubules of testes

1. Contain two cell types:

a. Sertoli (also known as sustentacular cells)

I. Support spermatogenesis

II. Tight junctions join neighboring Sertoli cells to one another, forming

an obstruction known as blood-testis barrier – substances must first

pass through Sertoli cells before they can reach the developing sperm

b. Leydig (also known as interstitial cells)

I. Secrete testosterone

• most prevalent androgen – promotes development of masculine

characteristics

• promotes a man’s libido (sexual drive)

D. Spermatogenesis

1. The process of multiplication and maturation of sperm

E. Sperm - each day about 300 million sperm complete the process of spermatogenesis

Once ejaculated, most sperm do not survive more than three to five days within the

female reproductive tract.

1. Head

a. Nucleus

I. Haploid content of DNA

b. Acrosome

I. Cap-like vesicle filled with enzymes to help sperm penetrate egg

c. Tail

I. Flagella for locomotion

F. The male duct system aids in the maturation, storage, and transport of sperm

1. Duct system includes

a. Epididymis

I. tightly coiled tube that connects the testis to the vas deferens

II. site of sperm maturation, the process by which sperm acquire motility

and the ability to fertilize an egg

III. occurs over a period of about 14 days

IV. helps propel sperm into the vas deferens during sexual arousal by

peristaltic contraction of its smooth muscle

V. stores sperm, which remain viable here for up to several months

b. Vas deferens (or ductus deferens)

I. From the epididymis, the vas deferens ascends out of the scrotum and

enters the pelvic cavity, where it loops over the side and down the back

surface of the urinary bladder

II. conveys sperm during sexual arousal from the epididymis toward the

urethra by peristaltic contractions of its smooth muscle

III. Like the epididymis, the vas deferens can also can store sperm for

several months

c. Ejaculatory duct

I. formed by the union of the vas deferens and the duct from the seminal

vesicle

II. enter the prostate gland and terminate in the urethra, where they eject

sperm and seminal vesicle secretions just before the release of semen

from the urethra to the exterior

d. Urethra

I. In males - shared terminal duct of reproductive and urinary systems

• serves as a passageway for both semen and urine

G. Accessory sex glands add secretions to sperm to form semen

1. Accessory glands

a. Seminal vesicle

I. pouch-like structures located behind urinary bladder and in front of

rectum

II. Secrete alkaline, viscous fluid that helps neutralize the acidic

environment of the male urethra and female reproductive tract that

would otherwise inactivate and kill sperm. Fluid secreted by the

seminal vesicles constitutes about 60% of the volume of semen. It

contains:

• Fructose - used for ATP production by sperm

• Clotting protein fibrinogen - helps semen coagulate (clot) after

ejaculation.

• Prostaglandins - stimulate smooth muscle contractions within the

female reproductive tract, facilitating movement of sperm cells up the

tract.

b. Prostate gland

I. roughly the size and shape of a golf ball, is below the urinary bladder and

surrounds the upper portion of the urethra.

II. Prostatic secretions make up about 25% of the volume of semen and

contribute to sperm motility and viability.

III. It secretes a milky, slightly acidic fluid (pH about 6.5) that contains

several substances:

• Citric acid - used by sperm for ATP production via the Krebs cycle

• Clotting enzymes - act on fibrinogen from the seminal vesicles to clot

semen after ejaculation

• Proteolytic enzymes - such as prostate-specific antigen (PSA),

fibrinolysin, and pepsinogen, eventually break down the clot

• Seminalplasmin (antibiotic) - antibiotic that destroys bacteria that

may be present in semen or in the female reproductive tract

• Acid phosphatase - function is unknown

c. Bulbourethral glands (Also called Cowper’s glands)

I. Located below the prostate gland on either side of the urethra

II. Secrete an alkaline fluid into the urethra that protects the passing

sperm by neutralizing acids from urine in the urethra.

III. They also secrete mucus that lubricates the end of the penis and the

lining of the urethra, decreasing the number of sperm damaged during

ejaculation.

IV. Secretions from the bulbourethral glands constitute about 5% of the

volume of semen.

* Semen is a mixture of sperm and the secretions of the seminal vesicles, prostate gland, and

bulbourethral glands. Despite the slight acidity of prostatic fluid, semen has a slightly alkaline pH of

7.2–7.7 due to the higher pH and larger volume of fluid from the seminal vesicles. Prostatic secretion

gives semen a milky appearance, and fluids from the seminal vesicles and bulbourethral glands give it

a sticky consistency. Seminal fluid provides sperm with a transportation medium, nutrients, and

protection from the hostile acidic environment of the male's urethra and the female's vagina.

*Once ejaculated, liquid semen coagulates within 5 minutes due to the presence of the clotting

protein fibrinogen from the seminal vesicles and clotting enzymes from the prostate gland.

Coagulation of semen occurs in the following way: The clotting enzymes act on fibrinogen to form the

protein fibrin, which clots the semen, trapping mobile sperm cells within the fibrin meshwork. It is

thought that semen coagulation occurs to help keep sperm cells from leaking out of the vagina. After

about 10 to 20 minutes, semen reliquefies because prostate-specific antigen (PSA) and other

proteolytic enzymes produced by the prostate break down the clot. As the clot dissolves, sperm cells

are released and begin their journey to the egg. Abnormal or delayed liquefaction of clotted semen

may cause complete or partial immobilization of sperm, thereby inhibiting their movement through

the female reproductive tract.

H. The penis is the male organ of copulation

1. Deposits semen into the female reproductive tract

2. Consists of two main regions: shaft and glans of penis

3. Two different erectile tissue types: corpus cavernosum and corpus spongiosum

I. Erection reflex

1. Sexual stimulation causes parasympathetic axons extending to smooth muscle in

penile arterioles to release nitric oxide and acetylcholine (ACh).

2. ACh binds to muscarinic receptors on endothelial cells in the penile arterioles

activating nitric oxide synthase to produce nitric oxide.

3. Nitric oxide (NO) released from parasympathetic axons or from nearby endothelial

cells diffuses through the membrane of the vascular smooth muscle cell to bind to

the enzyme guanylyl cyclase. 


4. Binding of NO to guanylyl cyclase activates the enzyme, which produces cGMP from

GTP. 


5. The cGMP, in turn, activates a pathway that results in relaxation of the smooth

muscle cell. Relaxation of smooth muscle causes the penile arteriole to dilate, which

ultimately causes erection to occur.

J. Ejaculation

1. Powerful smooth muscle contractions that result in release of semen

K. Male reproductive function is regulated by many different hormones

1. Main hormones

a. Gonadotropin

releasing hormone

(GnRH)

b. Luteinizing hormone

(LH)

c. Follicle stimulating

hormone (FSH)

d. Testosterone

e. Dihydrotestosterone

f. Inhibin

2. Major role hormones play

a. Prenatal development

b. Development of male

sex characteristics

c. Development of sexual

function

d. Stimulation of

anabolism

e.

III. Female Reproductive System

A. Female reproductive organs

1. Ovaries

2. Fallopian tubes (also known as uterine tubes)

3. Uterus

4. Vagina

5. Vulva

6. Mammary glands

B. The ovaries produce eggs (oocytes) and secrete hormones

1. Paired glands located in the pelvic cavity

2. Homologous to the testes

a. Within ovaries are ovarian follicles – each ovarian follicle consists of one oocyte

and variable number of surrounding cells that nourish developing oocyte

b. It also secretes hormones as the follicle grows larger

I. The ovarian follicle initially begins as a primordial follicle

II. sequentially develops into a primary follicle, a secondary follicle, and a

mature (graafian) follicle.

III. ovulation occurs when mature follicle ruptures, releasing oocyte into

pelvic cavity.

IV. From pelvic cavity, the oocyte is normally swept into the fallopian tube.

V. Within the ovary, the remnants of the ruptured follicle develop into a

structure called the corpus luteum (= yellow body).

VI. If released oocyte is not fertilized, corpus luteum eventually degenerates

into fibrous scar tissue called corpus albicans (=white body)

C. Oogenesis

1. Formation of gametes in the ovaries

2. During fetal development meiosis I begins

3. After puberty, meiosis I is completed, and meiosis II is initiated

4. Ovulation

5. Only after fertilization, meiosis II completed

D. The fallopian tube transports an egg from the ovary to the uterus.

1. Females have two fallopian tubes, also known as uterine tubes or oviducts, that extend from the

upper part of the uterus

2. The funnel-shaped end of each tube is close to an ovary and contains fingerlike projections

called fimbriae

3. Functionally, the fallopian tube transports an egg (oocyte) from the ovary to the uterus. This

occurs in the following way:

a. After ovulation, local currents produced by movements of the fimbriae sweep

the egg into the fallopian tube.

b. The egg is then moved along the tube by cilia in the tube's lining and peristaltic

contractions of the tube's smooth muscle layer.

Summary of Oogenesis and Follicular Development

4. The fallopian tube also serves as the site where fertilization normally takes place.

a. After semen is deposited into the vagina by the penis during sexual

intercourse, sperm move into the uterus and then into the fallopian tubes. If an

egg is present in one of the tubes, it may be fertilized by a sperm cell.

b. The cilia and peristaltic contractions of the fallopian tube move the fertilized

egg into the uterus, where it implants.

c. Fertilization can occur at any time up to about 24 hours after ovulation. If an

egg is not fertilized by that time, it degenerates.

E. The uterus has many reproductive functions

1. Hollow pear-shaped organ between rectum and urinary bladder

2. Made up of

a. Fundus

b. Body

c. Cervix

I. Sperm cells deposited in the vagina during intercourse reach the

fallopian tubes by passing through the cervix and the body of the uterus.

II. The lining of the cervix contains glands that secrete cervical mucus.

Most of the time, the mucous is viscous, forming a cervical plug that

impedes the spread of bacteria and the passage of sperm cells.

III. However, at or near the time of ovulation, cervical mucus is less viscous,

making it easier for sperm cells to pass through.

3. The wall of the uterus is composed of three layers:

a. Endometrium - contains large numbers of blood vessels and consists of

epithelial tissue, connective tissue, and endometrial glands. The endometrium

is further divided into two layers:

I. Stratum functionalis - (functional layer)

• lines the uterine cavity.

• In a nonpregnant woman of reproductive age, this layer sloughs off

every month, a process known as menstruation.

• subsequent release of blood and tissue from the body is referred to as

menstrual flow.

• In a pregnant woman, this layer remains attached to the rest of the

uterus and serves as the site where the fertilized egg has implanted

and develops into a fetus.

II. Stratum basalis (basal layer) is the deeper part of the endometrium.

• It is a permanent layer that gives rise to a new stratum functionalis

after each menstruation.

b. Myometrium - middle layer of the uterus

• consists of smooth muscle and forms the bulk of the uterine wall.

• During labor and childbirth, coordinated contractions of the

myometrium in response to oxytocin from the posterior pituitary help

expel the fetus from the uterus.

c. Perimetrium - outer layer of the uterus

• It consists of epithelium and connective tissue and provides support

to uterus.

*In summary, the uterus performs several functions. It serves as part of pathway for sperm

deposited in vagina to reach fallopian tubes. Also, site of implantation of a fertilized egg,

development of fetus during pregnancy, and contractions that push the fetus out of a woman's

body during childbirth. In addition, the uterus is the source of menstrual flow.

F. The vagina is the female organ of copulation

1. Serves as receptacle for the penis during intercourse

2. Tubular canal that extends from the cervix of the uterus to body exterior

3. Opening of the vagina to the exterior is known as the vaginal orifice

4. Secretions from vaginal walls is acidic preventing microbial growth

a. Damaging to sperm

I. Alkaline secretions in semen help to neutralize

G. The vulva (also called pudendum) refers to the female external genitalia

1. Includes:

a. Mons pubis - rounded, fatty area that covers joint between pubic bones

b. Labia majora - Extends down and back from the mons pubis

I. prominent folds of skin - homologous to the scrotum of the male.

c. Labia minora - The labia majora enclose the labia minora

I. two smaller folds of skin that are homologous to the shaft of the penis

d. Clitoris - small cylindrical mass of erectile tissue located at the front end of the

vulva. It is homologous to the glans penis. Like its male counterpart, the clitoris

fills with blood and enlarges during sexual arousal.

e. Vestibule - space between the labia minora. Within the vestibule are the

external urethral orifice (the opening of the urethra to the exterior) and the

vaginal orifice (the opening of the vagina to the exterior).

f. Paraurethral (Skene's) glands – located near the external urethral orifice,

which secrete mucus into the urethra. These glands are homologous to the

male prostate gland.

g. Greater vestibular (Bartholin's) glands – located on either side of the vaginal

orifice, which secrete a lubricating mucus into the vestibule during sexual

arousal. The greater vestibular glands are homologous to the bulbourethral

glands in males.

H. The mammary glands function in lactation

1. Consists of 15-20 lobes separated by variable amounts of adipose tissue

a. Smaller lobules called alveoli

I. Milk secreting structures

b. Lactation

I. The release of milk through the nipples

I. Female reproductive function is regulated by many hormones

1. Gonadotropin releasing hormone - Beginning at puberty, the hypothalamus

increases secretion of gonadotropin-releasing hormone (GnRH). GnRH in turn

stimulates the release of follicle‐stimulating hormone (FSH) and luteinizing

hormone (LH) from the anterior pituitary.

2. Follicle stimulating hormone - initiates follicular growth

3. Luteinizing hormone - stimulates further development of the ovarian follicles

a. stimulates the theca cells of a developing follicle to produce androgens (the

main thecal androgen is androstenedione).

b. In addition, both FSH and LH stimulate the ovarian follicles to secrete

estrogens.

c. Under the influence of FSH, the androgens are taken up by the granulosa cells

of the follicle and are then converted into estrogens. The enzyme aromatase

catalyzes this reaction.

d. LH also triggers ovulation and then promotes formation of the corpus luteum,

the reason for the name luteinizing hormone.

e. Stimulated by LH, the corpus luteum produces and secretes estrogens,

progesterone, relaxin, and inhibin.

4. Estrogens – secreted by ovarian follicles and the corpus luteum have several

important functions:

a. promotes development and maintenance of female reproductive structures

and secondary sex characteristics, which include:

I. distribution of adipose tissue in breasts, abdomen, mons pubis, and hips

II. a higher voice pitches

III. a broad pelvis

IV. female pattern of hair growth on head and body

b. increases protein anabolism, including the building of strong bones.

c. lowers blood cholesterol level, which is probably the reason that women under

age 50 have a much lower risk of coronary artery disease than do men of

comparable age.

d. Every month, after menstruation occurs, estrogens stimulate proliferation of

the stratum basalis to form a new stratum functionalis that replaces the one

that has sloughed off.

e. Moderate levels of estrogens in the blood inhibit both the release of GnRH by

the hypothalamus and secretion of LH and FSH by the anterior pituitary.

f. At least six different estrogens have been isolated from the plasma of human

females, but only three are present in significant quantities:

I. beta (β)-estradiol – most abundant estrogen in nonpregnant woman,

which is synthesized from cholesterol in ovaries

II. estrone

III. estriol

5. Progesterone - produced by cells of the corpus luteum

a. prepares the endometrium of the uterus for the possible implantation of a

fertilized egg by stimulating the endometrial glands to secrete glycogen and

lipids. These secretions serve as a nutrient source for the embryo during the

early stages of pregnancy until the placenta develops.

b. High levels of progesterone also inhibit secretion of GnRH, FSH, and LH.

6. Relaxin

a. Small quantity:

I. produced by the corpus luteum during each monthly cycle relaxes the

uterus by inhibiting contractions of the myometrium. Presumably,

implantation of a fertilized egg occurs more readily in a “quiet” uterus.

b. Large quantity:

I. during pregnancy, the placenta produces much more relaxin, and it

continues to relax uterine smooth muscle.

II. at the end of pregnancy, relaxin also increases the flexibility of the pubic

symphysis and may help dilate the uterine cervix, both of which ease

delivery of the baby.

7. Inhibin - secreted by granulosa cells of growing follicles and by the corpus luteum

after ovulation.

a. It inhibits secretion of FSH.

J. Female reproductive cycles - encompasses the ovarian and uterine cycles, the hormonal

changes that regulate them, and the related cyclical changes in the breasts and cervix.

1. Uterine - concurrent series of changes in the endometrium of the uterus to prepare

it for the arrival of a fertilized egg that will develop there until birth

a. Menses

b. Proliferative

c. Secretory

2. Ovarian - series of events in the ovaries that occur during and after the maturation

of an egg.

a. Follicular

b. Ovulation

c. Luteal

3. The duration of the female reproductive cycle typically ranges from 24 to 35 days. For this

discussion, it is assumed that the cycle has a duration of 28 days and is divided into four phases:

a. menstrual phase (menstruation) - lasts for roughly the first 5 days of the cycle.

By convention, the first day of menstruation is day 1 of a new cycle.

I. Events in the Ovaries

• Under the influence of FSH, several primordial follicles develop into

primary follicles and then into secondary follicles. This developmental

process may take several months to occur. Therefore, a follicle that

begins to develop at the beginning of a particular menstrual cycle may

not reach maturity and ovulate until several menstrual cycles later.

II. Events in the Uterus

• Menstrual flow from the uterus consists of 50–150 mL of blood, tissue

fluid, mucus, and epithelial cells shed from the stratum functionalis of

the endometrium. This discharge occurs because the declining levels

of estrogens and progesterone stimulate release of prostaglandins

that cause the uterine arteries to constrict. As a result, the cells they

supply become oxygen-deprived and start to die. Eventually, the

entire stratum functionalis sloughs off. At this time the endometrium

is very thin, about 2–5 mm, because only the stratum basalis remains.

The menstrual flow passes from the uterine cavity through the cervix

and vagina to the exterior.

b. preovulatory phase - time between the end of menstruation and the beginning

of ovulation. The preovulatory phase of the cycle is more variable in length

than the other phases and accounts for most of the differences in length of the

cycle. It lasts from day 6 to day 13 in a 28-day cycle.

I. Events in the Ovaries

• Some of the secondary follicles in the ovaries begin to secrete

estrogens and inhibin. By about day 6, a single secondary follicle in

one of the two ovaries has outgrown all of the others to become the

dominant follicle. Estrogens and inhibin secreted by the dominant

follicle decrease the secretion of FSH, which causes other, less well-

developed follicles to stop growing and undergo atresia. Fraternal

(nonidentical) twins or triplets result when two or three secondary

follicles become codominant and later are ovulated and fertilized at

about the same time.

• Normally, the one dominant secondary follicle becomes the mature

(graafian) follicle, which continues to enlarge until it is more than 20

mm in diameter and ready for ovulation. This follicle forms a blister-

like bulge on the surface of the ovary due to the swelling antrum.

During the final maturation process, the mature follicle continues to

increase its production of estrogens.

• With reference to the ovarian cycle, the menstrual and preovulatory

phases together are termed the follicular phase because ovarian

follicles are growing and developing.

II. Events in the Uterus

• Estrogens liberated into the blood by growing ovarian follicles

stimulate the repair of the endometrium; cells of the stratum basalis

undergo mitosis and produce a new stratum functionalis. As the

endometrium thickens, the endometrial glands develop, and blood

vessels coil and lengthen as they penetrate the stratum functionalis.

The thickness of the endometrium approximately doubles, to about

4–10 mm. With reference to the uterine cycle, the preovulatory phase

is also termed the proliferative phase because the endometrium is

proliferating.

c. Ovulation - rupture of the mature (graafian) follicle and the release of the egg

(secondary oocyte) into the pelvic cavity, usually occurs on day 14 in a 28-day

cycle. During ovulation, the secondary oocyte remains surrounded by its zona

pellucida and corona radiata.

• The high levels of estrogens during the last part of the preovulatory

phase exert a positive feedback effect on the cells that secrete LH and

gonadotropin-releasing hormone (GnRH) and cause ovulation, as

follows:

1. A high concentration of estrogens stimulates more frequent

release of GnRH from the hypothalamus. It also directly

stimulates gonadotrophs in the anterior pituitary to secrete LH.

2. GnRH promotes the release of FSH and additional LH by the

anterior pituitary.

3. LH causes rupture of the mature (graafian) follicle and

expulsion of a secondary oocyte about 9 hours after the peak of

the LH surge. The ovulated oocyte and its zona pellucida and

corona radiata cells are usually swept into the fallopian tube.

d. postovulatory phase - time between the end of ovulation and the onset of the

next menses. In duration, it is the most constant part of the female

reproductive cycle. It lasts for 14 days in a 28-day cycle, from day 15 to day 28

I. Events in One Ovary

• After ovulation, the ruptured follicle is transformed into the corpus

luteum under the influence of LH. Stimulated by LH, the corpus luteum

secretes progesterone, estrogen, relaxin, and inhibin. With reference

to the ovarian cycle, this phase is also called the luteal phase.

• Later events in an ovary that has ovulated an oocyte depend on

whether the oocyte is fertilized. If the oocyte is not fertilized, the

corpus luteum has a lifespan of only 2 weeks. After that, its secretory

activity declines, and it degenerates into a corpus albicans. As the

levels of estrogens, progesterone, and inhibin decrease, release of

GnRH, FSH, and LH rises due to loss of negative feedback suppression

by the ovarian hormones. Follicular growth resumes and a new ovarian

cycle begins.

• If the oocyte is fertilized and begins to divide, the corpus luteum

persists past its normal 2-week lifespan. It is “rescued” from

degeneration by human chorionic gonadotropin (hCG). This hormone

is produced by the chorion of the embryo beginning about 8 days after

fertilization. Like LH, hCG stimulates the secretory activity of the

corpus luteum. The presence of hCG in maternal blood or urine is an

indicator of pregnancy and is the hormone detected by home

pregnancy tests.

II. Events in the Uterus

• Estrogens secreted by the corpus luteum cause continued growth of

the stratum functionalis. As a result, the endometrium thickens to

about 12–18 mm (0.48–0.72 in.). Progesterone produced by the

corpus luteum promotes further growth and coiling of the

endometrial glands and vascularization of the superficial

endometrium. In addition, progesterone stimulates the endometrial

glands to secrete glycogen and lipids, which serve as an initial nutrient

source for a fertilized egg if implantation occurs. Because of the

secretory activity of the endometrial glands, this period is called the

secretory phase of the uterine cycle. These preparatory changes peak

about 1 week after ovulation, at the time a fertilized egg might arrive

in the uterus. If a woman is not pregnant, the levels of estrogens and

progesterone decline due to degeneration of the corpus luteum.

Withdrawal of estrogens and progesterone causes menstruation.

IV. The Human Sexual Response

A. Heterosexual intercourse

1. Also referred to as coitus or copulation

2. Penis is inserted into the vagina

B. A similar sequence of physiological and emotional changes that occur in both males and

females is termed the human sexual response.

C. Consists of four phases

1. Excitement

a. Consists of

I. Vasocongestion of genitals

• Engorging with blood

II. Results in erection for both males and females

III. Allows for transudation

• A lubrication of the vaginal walls that occurs once the When the

connective tissue of the vagina becomes engorged with blood

• Lubricating fluid oozes from the capillaries and seeps through

the epithelial lining

IV. Increased heart rate and blood pressure

V. Increased skeletal muscle tone throughout the body

VI. Hyperventilation

2. Plateau

a. Sustained sensations and physiological changes obtained during excitement

b. Lasts for only a few seconds to minutes

c. Can display a sex flush (especially females)

I. Redness in the face

d. Late plateau phase

I. Pronounced vasocongestion of the lower part of the vagina

• Swells the tissue and narrows the opening of the vagina

• Causes increased grip of the penis

3. Orgasm – also known as the climax

a. Briefest phase

b. Both sexes experience several rhythmic muscular contractions

c. Intense pleasurable sensations

d. Further increase in blood pressure, heart rate, breathing rate

e. Sex flush more prominent

f. In males - orgasm usually accompanies ejaculation.

I. Emission

• contraction of smooth muscle in the walls of the epididymis, vas

deferens, and ejaculatory ducts as well as secretion of fluid by the

accessory sex glands cause semen to move into the urethra

II. Ejaculation occurs

• rhythmic contractions of skeletal muscles at the base of the penis

propel semen out of the penis

III. Enter a refractory period

• A second orgasm and ejaculation are physiologically impossible

g. In females - if effective sexual stimulation continues, orgasm may occur

I. associated with 3–12 rhythmic contractions of the skeletal muscles that

underlie the vulva

II. reception of the ejaculate provides little stimulus for a female,

especially if she is not already at the plateau phase

• this is why a female partner does not automatically experience orgasm

simultaneously with her partner

h. refractory period

I. In both males and females, orgasm is a total body response that may

produce milder sensations on some occasions and more intense,

explosive sensations at other times.

II. Whereas females may experience two or more orgasms in rapid

succession, males enter a refractory period

• a recovery time during which a second ejaculation and orgasm is

physiologically impossible

• In some males, the refractory period lasts only a few minutes; in others

it lasts for several hours.

i. A female does not have to experience an orgasm for fertilization to occur

4. Resolution – final phase

a. Begins with a sense of profound relaxation

b. All tissues and physiological parameters return to unaroused state

c. If sexual excitement has been intense but orgasm has not occurred, resolution

takes place more slowly

V. Contraception

A. Various methods of contraception control fertility and prevent conception

a. Refers to the avoidance of pregnancy

b. Only method to be 100% effective is complete abstinence

c. Other methods available:

d. Sterilization

I. procedure that renders an individual incapable of further reproduction.

The principal method for sterilization of males is a vasectomy, in which

a portion of each vas deferens is removed. To gain access to the vas

deferens, an incision is made with a scalpel (conventional procedure) or

a puncture is made with special forceps (nonscalpel vasectomy). Then a

small section of each vas deferens is cut out and the remaining free ends

are tied off or cauterized. Although sperm production continues in the

testes, sperm can no longer reach the exterior. The sperm degenerate

and are destroyed by phagocytosis. Because blood vessels are not cut,

testosterone levels in the blood remain normal, so vasectomy has no

effect on sexual desire, sexual performance, or ejaculation.

II. Sterilization in females is achieved most often by performing a tubal

ligation, in which both fallopian tubes are closed off. This can be

achieved in a few different ways. “Clips” or “clamps” can be placed on

the fallopian tubes, the tubes can be tied off and/or cut, and sometimes

they are cauterized. In any case the result is that the egg cannot pass

through the fallopian tube, and sperm cannot reach the egg.

III. An alternative to tubal ligation is a type of nonincisional sterilization

known as Essure®. In the Essure® procedure, a soft, tiny coil made of

polyester fibers and nickel-titanium alloy is inserted with a catheter

into the vagina, through the uterus, and into each fallopian tube. Over a

3 month period, the coil stimulates growth of scar tissue in and around

itself, blocking fallopian tubes. As with tubal ligation, the egg cannot

pass through the fallopian tubes, and sperm cannot reach the egg.

e. hormonal methods

I. Aside from complete abstinence or sterilization, hormonal methods are

the most effective means of birth control. Oral contraceptives, or birth

control pills, contain various mixtures of synthetic estrogens and

progestin (a chemical with actions similar to progesterone). They

prevent pregnancy by negative feedback inhibition of GnRH release

from the hypothalamus, and FSH and LH release from the anterior

pituitary gland. The low levels of FSH and LH usually prevent the

development of a dominant follicle in the ovary. As a result, levels of

estrogens do not rise, the midcycle LH surge does not occur, and

ovulation does not take place. Even if ovulation does occur, as it does in

some cases, the progestin in oral contraceptives thickens cervical

mucus, making it difficult for sperm to reach the egg, and it also blocks

implantation in the uterus.

II. Among the noncontraceptive benefits of oral contraceptives are

regulation of the length of menstrual cycle and decreased menstrual

flow. However, oral contraceptives may not be advised for women with a

history of blood-clotting disorders, cerebral blood vessel damage,

migraine headaches, hypertension, liver malfunction, or heart disease.

Women who take the pill and smoke face far higher odds of having a

heart attack or stroke than do nonsmoking pill users. Smokers should

quit smoking or use an alternative method of contraception.

III. There are several variations of oral hormonal methods of contraception:

• Combined pill. Contains both estrogens and progestin and is typically

taken once a day for 3 weeks. The pills taken during the fourth week

are inactive (do not contain hormones) and permit menstruation to

occur.

• Seasonale®. Contains both estrogens and progestin and is taken once

a day in 3-month cycles of 12 weeks of hormone-containing pills

followed by 1 week of inactive pills. Menstruation occurs during the

thirteenth week.

• Minipill. Contains progestin only and is taken every day of the month.

• Emergency contraception (EC) pill. Consists of one pill containing

progestin that is used to prevent pregnancy following unprotected

sexual intercourse. The relatively high level of progestin in an EC pill

suppresses ovulation, thickens cervical mucus to prevent sperm from

reaching the egg, and blocks implantation. An EC pill is also known as

the morning after pill. An example is Plan B®, which is available

without a prescription. The pill should be taken as soon as possible but

within 72 hours of unprotected intercourse.

IV. Non-oral hormonal methods of contraception

• Contraceptive skin patch (Ortho Evra®). Contains both estrogens and

progestin delivered in a skin patch placed on the skin (upper outer

arm, back, lower abdomen, or buttocks) once a week for 3 weeks. After

1 week, the patch is removed from one location and then a new one is

placed elsewhere. During the fourth week no patch is used, allowing

menstruation to occur.

• Vaginal contraceptive ring (NuvaRing®). A flexible doughnut- shaped

ring about 5 cm (2 in.) in diameter that contains estrogens and

progestin and is inserted by the female herself into the vagina. It is left

in the vagina for three weeks to prevent conception and then removed

for one week to permit menstruation.

• Hormone injections (Depo-provera®). An injectable progestin given

intramuscularly by a health-care practitioner once every 3 months.

• Hormone implant (Implanon®). A matchstick-sized plastic rod

containing progestin that is surgically implanted under the skin of the

arm using local anesthesia. It slowly and continuously releases

progestin, which inhibits ovulation and thickens cervical mucus. The

effect lasts for 3 years and is even more reliable than sterilization.

Removing the implant restores fertility.

f. intrauterine devices

I. is a small, T-shaped object that is inserted by a health-care professional

into the cavity of the uterus. Two types of IUDs are available in the

United States: the copper IUD and the hormonal IUD. The copper IUD

(ParaGard®) contains a plastic frame that is covered with a copper wire.

The copper causes changes in the uterine lining that prevent

implantation of the fertilized egg. ParaGard is approved for up to 10

years of use and has long-term effectiveness comparable to that of

tubal ligation. The hormonal IUD (Mirena®) has a plastic frame that

surrounds a reservoir containing progestin. The progestin is slowly

released from the IUD and functions like the other progestin-containing

contraceptives: It suppresses ovulation, thickens cervical mucus, and

blocks implantation. Mirena is effective for up to 5 years. Some women

cannot use IUDs because of expulsion, bleeding, or discomfort.

g. Spermicides

I. Various foams, creams, jellies, and suppositories that contain sperm-

killing agents, or spermicides, make the vagina and cervix unfavorable

for sperm survival and are available without prescription. They are

placed in vagina before sexual intercourse. Most widely used spermicide

is nonoxynol-9, which kills sperm by disrupting their plasma

membrane. Spermicide is more effective when used with barrier method

such as a male condom, vaginal pouch, diaphragm, or cervical cap.

h. Barrier methods

I. use a physical barrier and are designed to prevent sperm from gaining

access to the uterine cavity and fallopian tubes. In addition to

preventing pregnancy, certain barrier methods (male condom and

vaginal pouch) may also provide some protection against sexually

transmitted diseases (STDs) such as AIDS. In contrast, oral

contraceptives and IUDs confer no such protection. Among barrier

methods are male condom, vaginal pouch, diaphragm, and cervical cap.

• A male condom is a covering of latex, polyurethane, or animal

membrane that is placed over the penis to prevent deposition of

sperm in the female reproductive tract.

• A vaginal pouch, sometimes called a female condom, is designed to

prevent sperm from entering the uterus. It is made of two flexible

rings connected by a polyurethane sheath. One ring lies inside the

sheath and is inserted to fit over the cervix; the other ring remains

outside the vagina and covers the female external genitalia.

• A diaphragm is a rubber, dome-shaped structure that covers the cervix

and must be fitted by a health-care professional. It is used in

conjunction with a spermicide and can be inserted by the female up to

6 hours before intercourse. The diaphragm stops most sperm from

passing into the cervix and the spermicide kills most sperm that do get

by. Although diaphragm use does decrease the risk of some STDs, it

does not fully protect against HIV infection because the vagina is still

exposed.

• A cervical cap resembles a diaphragm but is smaller and more rigid. It

fits snugly over the cervix and also must be fitted by a health-care

professional. Spermicides should be used with the cervical cap.

i. Periodic abstinence

I. A couple can use their knowledge of the physiological changes that

occur during the female reproductive cycle to decide either to abstain

from intercourse on those days when pregnancy is a likely result or to

plan intercourse on those days if they wish to conceive a child. In

females with normal and regular menstrual cycles, these physiological

events help to predict the day on which ovulation is likely to occur.

II. The first physiologically based method, developed in the 1930s, is

known as the rhythm method. It takes advantage of the fact that the

egg is only viable for up to 24 hours and that sperm can survive 3 to 5

days in the female reproductive tract. Thus, couples using this

contraceptive method should avoid sexual intercourse for several days

before ovulation, the day of ovulation, and several days after ovulation

(just in case ovulation occurs a few days after day 14). The effectiveness

of the rhythm method for birth control is poor in many women due to

the irregularity of the female reproductive cycle.

III. Another system is the symptothermal method, in which couples are

instructed to know and understand certain signs of fertility. The signs of

ovulation include a slight decrease in basal body temperature prior to

ovulation and then a slight increase in basal body temperature just after

ovulation; the production of abundant clear, stretchy cervical mucus;

and pain associated with ovulation (mittelschmerz). If a couple abstains

from sexual intercourse when the signs of ovulation are present, the

chance of pregnancy is decreased. A big problem with this method is

that fertilization can still occur if intercourse takes place a few days

before ovulation.

j. Coitus interruptus

I. is withdrawal of the penis from the vagina just before ejaculation.

Failures with this method are due either to failure to withdraw before

ejaculation or to pre-ejaculatory emission of sperm-containing fluid

from the urethra. In addition, this method offers no protection against

transmission of STDs.

2. Table provides the failure rates for different types of contraceptive methods.