Males and females have sex organs for making new organisms {reproduction, animal}.
day length
In some birds and small mammals, reproduction cycles depend on number of daylight hours.
sex among humans
Only human females are always ready for sex, have permanent breasts, have continuous ability to have orgasms, have active roles in sexual activities, and are similar in size to males. Human sex can be face to face. Humans have wide territories. Humans have foreknowledge of children. Humans typically do not allow incest, so no old males can dominate female groups. Humans do not have estrus and so do not know exactly when they ovulate. People can have more children almost immediately after having a child, whereas apes wait five to six years between births.
People can have characteristics of both sexes {androgyny}|. Hermaphrodism can cause androgyny.
People have fathers {paternity}.
People conceive more boys than girls {sex ratio, birth}, perhaps from lighter XY sperm compared to XX sperm.
People can study sexual behavior and physiology {sexology}|.
interracial marriage or sexual intercourse {miscegenation}|.
Women can have one man {monandry}|.
Men can have one woman {monogyny}|.
People can dislike marriage {misogamy}|.
People can dislike women {misogyny}|.
Erect penis enters similarly blood-engorged vagina and ejects semen, four milliliters with 3 x 10^8 sperm, by epididymis, vas deferens, and urethra involuntary-muscle orgasm contractions {copulation} {intercourse}|. Only human females can have orgasms in clitoris and/or vagina and uterus. Sperm travel {motile} by tail movements and uterus contractions to oviduct tops. Sperm live 24 to 48 hours. Eggs live 24 to 78 hours.
sexual intercourse {coition}|.
sexual intercourse {coitus}|.
sexual intercourse {coupling}|.
Intercourse can cause pain {dyspareunia} in both men and women.
Fathers can have sexual intercourse with daughters, or mothers can have sexual intercourse with sons {incest}|.
Increased blood flow causes vasocongestion, which creates penis erections in males and vaginal lubrication {transudorific reaction, vagina} in females.
Glans penis or clitoris stimulation builds to muscle contractions {orgasm}|.
physiology
Men and women sexual physiologies are essentially the same. First, physical or psychological sexual stimulation causes more blood flow, as heart rate increases. Increased blood flow causes vasocongestion, which creates male penis erection and female vaginal lubrication {transudorific reaction, orgasm}. Then vagina lengthens and increases diameter, especially inner third. Penis increases diameter and length. Vasocongestion causes clitoris and breast nipples to become erect. Then involuntary muscular contractions trigger, causing male orgasm and seminal-fluid ejaculation. In males, glans penis has orgasm. In females, orgasm can be in clitoris and/or vagina.
female
Female sexual stimulation is an autonomic process and happens at clitoris and other body areas. Female orgasm has involuntary contractions of pubococcygeal muscles surrounding last third of vagina. Clitoral stimulation must spread, and this depends on personality and socially conditioned inhibitions. Orgasms differ in completeness and emotional satisfaction.
Females do not have equivalent of ejaculation.
Females can have orgasms by coitus but not by masturbation {masturbatory orgasmic dysfunction}, orgasms by masturbation but not by coitus {coital orgasmic dysfunction}, or only sporadic orgasms {random orgasmic dysfunction}.
male
Males can have primary or secondary impotence, premature ejaculation, and inability to ejaculate. Squeezing glans penis can temporarily inhibit ejaculation.
Inserting penis into anus {sodomy}| can be for sexual pleasure.
Spanish fly comes from beetles, stimulates GI tract, and increases blood flow {aphrodisiac}|.
People can like to display sexual organs in public {exhibitionism}|.
People can believe that objects {fetish}| can have magic or sexual power.
During sexual play, people can bite neck or shoulder {hickey}.
Men can wear women's clothes {transvestism}|.
People can stimulate themselves sexually {autoeroticism}|.
masturbation {onanism}|.
masturbation {self-abuse}.
Mouth and tongue can stimulate female sex organs {cunnilingus}|.
Mouth and tongue can stimulate penis {fellatio}|.
Man can perform cunnilingus while woman performs fellatio {sixty-nine}.
Males and females can use various methods {contraception}| to prevent egg fertilization or implantation and thus pregnancy. Females can use estrogen-progesterone chemicals, vaginal spermicides, intrauterine devices, cervical covers, and tubal ligation. Males can use testosterone chemicals, condoms, and vasectomy surgery.
Cotton-seeds phenols {gossypol} can inhibit dehydrogenase reactions and can reduce sperm count but cause low blood potassium and are poison.
Germ cells {gamete}| are haploid sperm or eggs.
Male and female gamete union {syngamy}| makes one somatic cell.
Corona radiata cells cover eggs, and hyaluronic acid holds them together. Many sperm attack corona radiata with enzymes, until one sperm breaks through {fertilization, process}|. Fertilizing sperm causes fertilization membrane formation, to block other sperm. Fertilized egg begins to divide. Eggs implant in uterus walls five to ten days after fertilization.
Women can be pregnant {maternity}.
after birth {post partum}|.
before birth {prenatal}|.
Cervix dilation and breaking water happen twelve hours before birth {birth, reproduction}| {nativity}. Fetus comes out head first, with face toward spine, taking 20 to 60 minutes. After cutting umbilical cord, umbilical arteries and veins close. Carbon-dioxide buildup causes first breath to start. At birth, heart blood flow changes direction. Head pressure can cause brain blood-vessel hemorrhage, and little breathing and low oxygen are dangers.
Cervix dilation and amnion breaking {breaking water}| happen twelve hours before birth.
Fetus comes out {parturition}| head first, with face toward spine, taking 20 to 60 minutes.
Surgically removing baby from uterus {Caesarean}| can be necessary.
Placenta {afterbirth}| expulsion happens 15 minutes after birth.
If oval window fails to close, blood is low in oxygen {blue baby}|.
Baby hearts have an opening {oval window, heart} between atria.
Birth weight can be less than 2.5 kilograms {premature birth}.
Female animals can have more than one baby in litters {multiparous}.
Female mammals can have one child each sexual period {uniparous}.
Twins {twin}| can be fraternal twins or identical twins.
Twins {fraternal twin} can come from two different eggs.
Twins {identical twin} can come from one egg that splits into two eggs.
Identical twins {Siamese twin} can share tissue.
People have external sex organs {genitals}|.
Fetal umbilical cords, cut after birth, leave remnants {navel}|.
Hairy skin {pubes}| is over pubic bone.
Primary sexual characteristics {sexual characteristic} are sexual organs. Secondary sexual characteristics are body-hair distribution, breast shapes, muscle sizes, and arm and leg carrying angles. Tertiary sexual characteristics are behaviors associated with being masculine and feminine. Male and female sex roles differ in different cultures.
Females {female reproductive organs} have ovaries, Graafian follicles, oogonia, Fallopian tubes, uterus, cervix, vagina, vulva, mons veneris, labia majora, labia minora, clitoris, and hymen.
Before birth, woman can lie in bed {lying-in}|.
Absorbent pads {sanitary napkin} can retain menstrual blood.
lesbianism {sapphism}.
female gonad {ovary, gonad}|.
Ovaries have follicles {Graafian follicle}|, which store oogonia. Ovaries produce eggs, one at a time in humans, and release mature ova into abdomen.
Ovum passes into tubes {oviduct} {Fallopian tube}|, for fertilization.
Oviducts lead to womb {uterus}|, where fertilized ovum attaches to wall and starts to develop.
uterus {womb}|.
Uteri have muscle rings {cervix}| at bottom openings.
From cervix, a tube {vagina}| leads to outside.
Thin membrane {hymen}| can cover vagina opening. Only three species have hymen.
hymen {maidenhead}.
At vagina opening are female sex organs {vulva}|.
Large flaps {labia}| {labia majora} with hair are around opening. Small flaps {labia minora} with no hair are over vagina.
A small penis-like organ {clitoris}| is in front of urethra.
Vulva top front {mons veneris} {mount of Venus} has fatty tissue covered by hair.
Ovaries have Graafian follicles, which store immature eggs {oogonium}.
Oogonia develop {oogenesis} to make oocytes.
Oogonia develop to make immature eggs {oocyte} {primary oocyte}.
If follicle matures, egg divides into main cell {secondary oocyte} and cell {polar body} with little cytoplasm.
One secondary oocyte divides into one large cell {ootid} and one polar body.
Polar bodies disintegrate, and ootid matures into egg cell {ovum} {ova}, with much yolk. Follicle cells kill bad eggs.
Cells {corona radiata} cover eggs. Hyaluronic acid carbohydrate holds cells together.
After sperm enters egg, membrane {fertilization membrane} forms, to block other sperm.
If egg has no fertilization, no egg implants, and uterus internal lining sloughs off {menstruation}| {menses}. Menstrual bleeding is greater in women than in other primates.
In most sexual animals, females have periods {estrus}| {heat, sex} {sexual readiness} {estrous cycle} when they are receptive to males, during which uterine glands secrete.
First-menstruation age {menarche}| is from 14 to 19 years old and decreases with city life, high-protein diet, and more exposure to males.
Menstruation typically ceases {menopause}| at 40 to 45 years old.
Females can have regular sex-receptive periods {rut, sex}|.
Males {male reproductive organs} have testis, seminiferous tubule, interstitial cell, epididymis, vas deferens, inguinal canal, prostate gland, and penis.
sperm and seminal fluid {semen}|.
Skin sacs {scrotum}| hold testes.
male gonads {testis, organ}|.
Testis makes sperm in tubules {seminiferous tubule}.
Testis makes hormones in cells {interstitial cell}.
Sperm pass into tubes {epididymis} for storage.
Tubes {vas deferens}| go through inguinal canal, over bladder, to urethra top.
Vas deferens goes through connective-tissue passageways between leg and pelvis {inguinal canal}|, over bladder, to urethra top.
At urethra, a gland {prostate gland}| {seminal vesicle} makes fluid and secretes it into vas deferens.
Urethra leads into fleshy organ {penis}|, which has erectile tissue.
bull penis {pizzle}.
Penis has three spongy-tissue {erectile tissue} columns that can fill with blood to become hard.
Glands {Cowper's gland} {Cowper gland} can secrete into urethra.
In males, penis tip {glans}| has orgasm.
Testes make small cells {sperm}| with nuclei and tails and many mitochondria. Male potency peaks in late adolescence. Sertoli cells kill bad sperm.
Fish spread sperm {milt}| over laid eggs.
Male germ cells develop to make spherical cells {spermatid} {spermatogenesis}. Spermatids mature into sperm having head with cell nucleus, neck with mitochondria for energy, and tail.
Spermatids mature into sperm, with enzyme pouches {acrosome} at tips. Acrosomes break corona radiata.
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0225