Reproduction one property of a living thing great variety of methods

Sexual reproduction each offspring has 2 parents and receives genetic

material from both provides genetic diversity foundation for survival and evolution of species

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Male and female gametes (sex cells) combine their genes to form a fertilized egg (zygote) one gamete has motility (sperm)

parent producing sperm considered male has Y chromosome in most mammals

other gamete (egg or ovum) contains nutrients for developing zygote parent producing eggs considered female in mammals the female also provides shelter for the

developing fetus (uterus and placenta)

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Primary sex organs produce gametes (testes or ovaries)

Secondary sex organs male - ducts, glands, penis deliver sperm cells female - uterine tubes, uterus and vagina receive sperm

and nourish developing fetus Secondary sex characteristics

develop at puberty to attract a mate pubic, axillary and facial hair, scent glands, body morphology

and low-pitched voice in males

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Our cells contain 23 pairs of chromosomes 22 pairs of autosomes 1 pair of sex chromosomes (XY males: XX females)

males produce 50% Y carrying sperm and 50% X carrying all eggs carry the X chromosome

Sex of child determined by type of sperm that fertilizes mother’s egg

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Gonads begin to develop at 6 weeks

The male and female reproductive systems have different embryological origins mesonephric ducts

develop into male reproductive system

paramesonephric ducts (müllerian ducts) develop into female reproductive tract

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SRY gene (Sex-determining Region of Y gene) in males, codes for a protein that causes development of

testes testes secrete testosterone testes secrete müllerian-inhibiting factor which

degenerates paramesonephric ducts In absence of hormones, fetus becomes

phenotypically ‘female’

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External genitals of both sexes begin as a genital tubercle

becomes glans of penis or clitoris

pair of urogenital folds enclose urethra of male or form labia minora

a pair of labioscrotal folds scrotum or labia majora

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All 8 week old fetuses have same 3 structures by end of week 9, begin to

show sexual differentiation distinctly male or female by

end of week 12

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Begin development near kidney gubernaculum (cordlike structure containing muscle) extends

from gonad to abdominopelvic floor it shortens, guides testes to scrotum

Descent begins in weeks 6-10, finished by 28 3% born with undescended testes (cryptorchidism)

Location outside pelvic cavity essential for low temperatures needed for sperm production

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Impotence – Inability to sustain an erection sufficient for sexual intercourse, or inability to ejaculate

Male Sterility – Infertility caused by disorders of the male reproductive system

BPH – Benign Prostatic Hypertrophy Cryptorchidism – Undescended testicle(s)

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Pouch holding testes divided into 2

compartments by median septum

Spermatic cord travels up from scrotum to pass through inguinal canal contains testicular

artery, vein, nerve and lymphatics

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Circumcision

Muscular control Cremaster muscle Dartos muscle

Counter-current exchange Pampiniform plexus

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Oval organs, 4 cm long x 2.5 cm in diameter covered anteriorly by tunica vaginalis

Tunica albuginea white fibrous capsule on testes

Septa divide testes into compartments containing seminiferous tubules each tubule lined with a thick

germinal epithelium for sperm interstitial cells between tubules -

testosterone Rete testis

seminiferous tubules drain here

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Efferent ductules 12 small ciliated ducts collecting sperm

from rete testes and transporting it to epididymis

Epididymis (head, body and tail) 6 m long coiled duct adhering to

posterior of testis site of sperm maturation and storage

(fertile for 60 days) Ductus deferens (peristalsis during

orgasm) muscular tube 45 cm long passing up

from scrotum through inguinal canal to posterior surface of bladder

Ejaculatory duct 2 cm duct formed from ductus

deferens and seminal vesicle and passing through prostate to empty into urethra

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Vasectomy

Regions: prostatic, membranous and penile --- totals 20 cm long

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Seminal vesicles - pair posterior to bladder empty into ejaculatory duct

Prostate gland - single below bladder, surrounds urethra

and ejaculatory duct 2 x 4 x 3 cm

Bulbourethral glands - pair near bulb of penis empty into penile urethra lubricating fluid

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Internal root, shaft, and glans external portion 4 in. long when flaccid

The foreskin is termed the prepuce 3 cylindrical bodies of erectile tissue

corpus spongiosum along ventral side of penis encloses penile urethra

corpora cavernosa diverge like arms of a Y Erection

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Hypothalamus produces GnRH Stimulates anterior pituitary (gonadotrope

cells) to secrete LH

stimulates interstitial cells to produce testosterone FSH

stimulates sustentacular cells (Sertoli cells) to secrete androgen-binding protein (ABP) that interacts with testosterone to stimulate spermatogenesis

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Reproductive system remains dormant for years after birth surge of pituitary gonadotropins begins development

10-12 in most boys; 8-10 in most girls

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Puberty period from onset of

gonadotropin secretion until first menstrual period or first ejaculation of viable sperm

Adolescence ends when person

attains full adult height

Enlargement of secondary sexual organs penis, testes, scrotum, ducts, glands

Development of secondary sexual characteristics hair, scent and sebaceous glands develop muscle mass, vocal quality stimulates erythropoiesis and libido

During adulthood, testosterone sustains libido, spermatogenesis and reproductive tract

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Enlargement of secondary sexual organs penis, testes, scrotum, ducts, glands

Development of secondary sexual characteristics hair, scent and sebaceous glands develop muscle mass, vocal quality stimulates erythropoiesis and libido

During adulthood, testosterone sustains libido, spermatogenesis and reproductive tract

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Mitosis produces two genetically identical daughter cells (for tissue repair, embryonic growth)

Meiosis produces gametes for sexual reproduction 2 cell divisions (only one

replication of DNA) meiosis I separates

homologous chromosome pairs into 2 haploid cells

meiosis II separates duplicated sister chromatids into 4 haploid cells

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Blood-testis barrier is formed by tight junctions between and basement membrane under sustentacular cells (Sertoli cells)

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1 basal lamina, 2 spermatogonia, 3 spermatocyte 1st order, 4 spermatocyte 2nd order, 5 spermatid, 6 mature spermatid, 7 Sertoli cell, 8 tight junction (blood testis barrier)

Spermatogonia produce 2 kinds of daughter cells type A remain outside blood-testis

barrier and produce more daughter cells until death

type B differentiate into primary spermatocytes cells must pass through

BTB to move inward toward lumen - new tight junctions form behind these cells

meiosis I 2 secondary spermatocytes

meiosis II 4 spermatids

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Changes that transform spermatids into spermatozoa discarding excess cytoplasm and growing tails

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Head is pear-shaped front end 4 to 5 microns long structure

containing the nucleus, acrosome and basal body of the tail flagella nucleus contains haploid set of

chromosomes acrosome contains enzymes that

penetrate the egg basal body

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Tail is divided into 3 regions midpiece contains mitochondria

around axoneme of the flagella (produce ATP for flagellar movement)

principal piece is axoneme surrounded by fibers

endpiece is very narrow tip of flagella

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2-5 mL of fluid expelled during orgasm 60% seminal vesicle fluid, 30% prostatic, 10% sperm normal sperm count 50-120 million/mL

Other components of semen fructose - energy for sperm motility fibrinogen causes clotting

enzymes convert fibrinogen to fibrin fibrinolysin liquefies semen within 30 minutes prostaglandins stimulate female peristaltic contractions spermine is a base stabilizing sperm pH at 7.2 to 7.6

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Arteries of penis dorsal and deep arteries (branches of internal pudendal) deep artery supplies lacunae of corpora cavernosa

dilation fills lacunae causing an erection normal penile blood supply comes from dorsal artery

Nerves of penis abundance of tactile, pressure and temperature receptors dorsal nerve of penis and internal pudendal nerves lead to

integrating center in sacral spinal cord both autonomic and somatic motor fibers carry impulses

from integrating center to penis

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Excitement is characterized by vasocongestion of genitals, myotonia, and increases in heart rate, blood pressure and pulmonary ventilation

Initiated by many different erotic stimuli Erection of penis is due to parasympathetic triggering

of nitric oxide (NO) secretion dilation of deep arteries and filling of lacunae with blood

Erection is maintained during plateau phase

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Climax (orgasm) is 15 second reaction that typically includes the discharge of semen (ejaculation)

Ejaculation has two stages emission = sympathetic nervous system propels sperm

through ducts as glandular secretions are added expulsion = semen in urethra activates muscular

contractions that lead to expulsion

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Sympathetic signals constrict internal pudendal artery and reduce blood flow to penis penis becomes soft and flaccid (detumescence)

Cardiovascular and respiratory responses return to normal

Refractory period (10 minutes to few hours)

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