1 table 27.1. 2 fig. 27.2 x x spermegg xx = female xy = male y x copyright © mcgraw-hill education....

1

Table 27.1

2

Fig. 27.2

XX

Sperm Egg

XX = female

XY = maleY

X

Copyright © McGraw-Hill Education. Permission required for reproduction or display.

3

Fig. 27.3 Copyright © McGraw-Hill Education. Permission required for reproduction or display.

Mesonephros

Gonadal ridge

Kidney

Mesonephric duct

Paramesonephric(müllerian) duct

Cloaca

5- to 6-week embryo;sexually indifferent stage

FemaleMale

Testes

Efferent ductules

Epididymis

Mesonephric ductforming theductus deferens

Urinary bladder

Seminal vesicle

Urogenital sinusforming the urethra

7 to 8 weeks

Urinarybladder

SeminalvesicleProstate gland

Ductus deferens

Epididymis

Testis

Urethra

Penis

At birth At birth

Vestibule

Hymen

Urethra

Vagina

Urinary bladder(moved aside)

Uterus

Ovary

Uterinetube

Urogenital sinusforming the urethraand lower vagina

Urinary bladder(moved aside)

Fused paramesonephricducts formingthe uterus

Mesonephric duct(degenerating)

Paramesonephricduct forming theuterine tube

Ovaries

8 to 9 weeks

Bulbourethalgland

Paramesonephricduct (degenerating)

4

Fig. 27.4Copyright © McGraw-Hill Education. Permission required for reproduction or display.

Genital tubercle

Urogenital fold

Labioscrotal fold

Tail

6 weeks

8 weeks

Male

Phallus:

Developing glansof penis

Urethral groove

Anus

Urethral orifice

Glans of penis

Prepuce

Scrotum

Perineal raphe

Anus

Female

Developing glansof clitoris

Labia minora

Urethral groove

Labia majora

Anus

Prepuce

Glans of clitoris

Urethral orifice

Vaginal orifice

Perineal raphe

Anus

12 weeks 12 weeks

10 weeks 10 weeks

5


3-month fetus 8-month fetus 1-month-old infant

ParietalperitoneumEpididymis

Testis

Ductus deferens

Pubic symphysisVaginal process

Gubernaculum

Scrotal swelling Penis

Vaginal process

Muscular wallof abdomen

Inguinal canal

Closed proximalportion ofvaginal process

Spermatic cord

Tunica vaginalis

Scrotum

Gubernaculum

Fig. 27.5

6

Fig. 27.6


Location of pubicsymphysis

Perineal raphe

Urogenital triangle

Anal triangle

Location ofcoccyx

Anus

Location of ischialtuberosity

7


External inguinal ring

Spermatic cord:Cremaster muscle

Testicular artery

Ductus deferens

Pampiniform plexus

Epididymis

Tunica vaginalis

Testis

Fascia of spermatic cordSuperficial fascia of penisDeep fascia of penis

Prepuce (foreskin)

Glans

Median septum of scrotum

Cremaster muscle

Dartos muscle

Scrotal skin

8

Fig. 27.8


Pelvic cavity

Testicular artery

37°C

Blood flow

Arterial blood coolsas it descends

35°C

Testis

Pampiniform plexus

Blood flow

Heat transfer

Venous blood carriesaway heat as it ascends

Coolestblood

Warmestblood

Key

9

Ductus deferens

Head ofepididymis

Testis, coveredby tunicaalbuginea

Tail of epididymis

Scrotum(folded down)

Interstitial cells

Blood vessel

Germ cells

Sustentacular cell

Tails ofspermatozoa

(a) 2 cm

Head ofepididymis

Ductusdeferens

Efferentductule

Body ofepididymis

Spermaticcord

Blood vesselsand nerves

Seminiferoustubule

Septum

Lobule

Tunicavaginalis

Tunicaalbuginea

Tail ofepididymis

Blood vessel

Seminiferoustubule

Spermatids

Sustentacularcell nuclei

Tubule lumenGerm cells

Connective tissuewall of tubule

Interstitial cells

(c)

(d) 50 µm

(b)

Spermatic cord

Rete testis

Fig. 27.9

a: ©McGraw-Hill Education/Dennis Strete; c: ©Dr. Kessel & Dr. Kardon/Tissues and Organs/Visuals Unlimited, Inc.; d: ©Ed Reschke


10

Fig. 27.10

Urinarybladder

Pubicsymphysis

Root ofpenis

Ductus (vas) deferens

Shaft of penis

Corpus cavernosum

Corpus spongiosum

Epididymis

Glans of penis

Prepuce

Testis

Scrotum

Rectum

Ampulla of ductus deferens

Seminal vesicle

Ejaculatory duct

Prostate gland

Bulbourethralgland

Bulbospongiosusmuscle

Urethra

Ureter

(a) Sagittal section

Urinarybladder

Prostategland

Prostaticurethra

Membranousurethra

Ductus deferens

Ampulla

Seminalvesicle

Ejaculatoryduct

Bulbourethralgland

Bulb

Crus

Corpusspongiosum

Corpuscavernosum

Testis

Efferentductules

Epididymis

Spongy (penile)urethra

Glans of penis

(b) Posterior view Penis


11

Fig. 27.11


Dorsal vein

Dorsal artery

Dorsal nerve

Dorsal

Corpus spongiosum

Corpus cavernosum

Deep fascia

Superficial fascia

Skin

Urethra

Deep artery

Tunicaalbuginea

Lacunae

Median septumCorpus spongiosum

PrepuceVentral

(b)

Glans of penis

External urethral orifice(a)

12

Fig. 27.12

1 GnRH from hypothalamus stimulates theanterior pituitary to secrete FSH and LH.

2 FSH stimulates sustentacularcells to secrete androgen-bindingprotein (ABP).

3 LH stimulates interstitial cells tosecrete testosterone (androgen).

4 In the presence of ABP,testosterone stimulatesspermatogenesis.

Hypothalamus Libido

InhibinFSHLH

Secondarysex organs

Secondary sexcharacteristics

GnRH

Pituitary gland

Testis Sustentacularcells

ABP

Interstitialcells

1

Testosterone also stimulates thelibido and the development ofsecondary sex organs andcharacteristics.

Testosterone has negativefeedback effects that reduce GnRHsecretion and pituitary sensitivityto GnRH.

5

5

6

7

6

7

2

4

Sustentacular cells also secreteinhibin, which selectively inhibitsFSH secretion and thus reducessperm production without reducingtestosterone secretion.

+

++

+

+

+

+

+

+

3

Inhibition

Stimulation

Key

Testosterone

Spermatogenesis


13

Meiosis I (first division) Meiosis II (second division)

Early prophase IChromatin condenses toform visible chromosomes;each chromosome has 2chromatids joined by acentromere.

Mid- to late prophase IHomologous chromosomesform pairs called tetrads.Chromatids often breakand exchange segments(crossing-over). Centriolesproduce spindle fibers.Nuclear envelopedisintegrates.

Metaphase ITetrads align onequatorial plane ofcell with centromeresattached to spindlefibers.

Anaphase IHomologouschromosomesseparate andmigrate to oppositepoles of the cell.

Telophase INew nuclearenvelopesform aroundchromosomes;cell undergoescytoplasmicdivision(cytokinesis).Each cell isnow haploid.

Chromosome

Nucleus

Centromere

Centrioles

Tetrad

Crossing-over

Spindlefibers

Centromere

Chromatid

Equatorialplane

Cleavage furrow

Final product is 4haploid cells withsingle-strandedchromosomes.

Telophase IINew nuclear envelopesform around chromosomes;chromosomes uncoil andbecome less visible;cytoplasm divides.

Anaphase IICentromeres divide;sister chromatidsmigrate to oppositepoles of cell. Eachchromatid now constitutesa single-strandedchromosome.

Metaphase IIChromosomes align onequatorial plane.

Prophase IINuclear envelopesdisintegrate again;chromosomes stillconsist of 2 chromatids.New spindle forms.


14


Cross section ofseminiferous tubules

Lumen ofseminiferous tubule

Sperm

Secondary spermatocyte

Blood–testis barrier

Primaryspermatocyte

Sustentacular cell

Type B spermatogonium

Tight junction

Type A spermatogonium

Basement membraneof seminiferous tubule

Spermiogenesis

Meiosis II

Meiosis I

nn

n

n

n

n

2n

2

5

4

3

1

2n

2n

Spermatid

15

Fig. 27.15

Golgi complexAcrosomalvesicle

Nucleus

Bridge toadjacent

spermatid

Acrosome

Head

Axoneme

Mitochondria

Midpieceof tail

Basalbody

Flagellum ExcesscytoplasmAppearance of

acrosomal vesicleand flagellum inspermatid Growth of

acrosomeand flagellum

Shedding ofexcesscytoplasm

Mature sperm

1

2

3

4


16


Head

Acrosome

Nucleus

Basal body

Mitochondrion

Axoneme

Midpieceof tail

Principalpiece oftail

Endpieceof tail

2 µm

(b)(a)a: ©David Phillips/Visuals Unlimited

17

Fig. 27.17 Copyright © McGraw-Hill Education. Permission required for reproduction or display.

Excitement

Stimulationof genitalregion,especiallyglans

Visual,mental,and otherstimuli

Internalpudendalnerve

Pelvic nerve

Efferentparasympathetic

signalsSpinal cord (sacral)

Spinal cord (L1–L2)

Efferentsympathetic

signals

Deep artery of penis dilates; erectiletissues engorge with blood; penisbecomes erect

Trabecular muscle of erectile tissuesrelaxes; allows engorgement oferectile tissues; penis becomes erect

Bulbourethral gland secretesbulbourethral fluid

Orgasm — emission stage

Ductus deferens exhibits peristalsis;sperm are moved into ampulla; ampullacontracts; sperm are moved into urethra

Prostate secretes components of theseminal fluid

Seminal vesicles secrete components ofthe seminal fluid

Afferentsignals

Semen in urethra

Prostate releases additional secretion

Seminal vesicles release additionalsecretion

Efferentsympathetic

signals

Spinal cord (L1–S4) Efferentsomaticsignals

Bulbocavernosus muscle contracts, andrhythmically compresses bulb and root ofpenis; semen is expelled (ejaculationoccurs)

Internal urethral sphincter contracts;urine is retained in bladder

Resolution

Spinal cord (L1–L2)

Efferentsympathetic

signals Penis becomes flaccid (detumescent)

Trabecular muscles contract;squeeze blood from erectile tissues

Internal pudendal artery constricts;reduces blood flow into penis

Orgasm — expulsion stage

18

Fig. 27.18


Phosphodiesteraseinhibitors

Sexualstimulation

Nitric oxide

Inactiveguanylatecyclase

GTP

Activeguanylatecyclase

cGMPVasodilationand erection

Loss oferection

Degradedby PDE5

1 table 27.1. 2 fig. 27.2 x x spermegg xx = female xy = male y x copyright © mcgraw-hill education....

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