Figure 27.1

Copyright © 2010 Pearson Education, Inc. Figure 27.1

PeritoneumSeminalvesicle Ampulla ofductus deferensEjaculatoryduct

RectumProstateBulbourethralgland

AnusBulb of penis

Epididymis

UreterUrinary bladderProstaticurethra

Pubis

Membranousurethra Urogenitaldiaphragm

Corpuscavernosum Corpusspongiosum

Glans penisPrepuceExternalurethral orifice

Spongy urethra

TestisScrotum

Ductus (vas)deferens

Copyright © 2010 Pearson Education, Inc.

The Scrotum

• Temp kept constant by 2 muscles• Dartos wrinkles scrotal skin

• Cremaster elevate testes


Penis

Internal spermaticfascia

Superficial inguinalring (end of inguinal canal)

Urinary bladder

Spermatic cord Ductus (vas) deferensAutonomicnerve fibers

Testicular artery

Epididymis

Pampiniformvenous plexus

Tunica vaginalis(from peritoneum)Tunica albugineaof testis

Middle septumof scrotumCremaster muscleExternal spermaticfascia

Superficial fasciacontaining dartos muscleSkin

Scrotum


The Testes

• Surrounded by:• Tunica vaginalis, from peritoneum

• Tunica albuginea, fibrous capsule

Copyright © 2010 Pearson Education, Inc. Figure 27.3a

Head of epididymis

Body of epididymis

Tail of epididymis

Efferent ductule

Rete testisStraight tubule

Duct of epididymis

Ductus (vas)deferens

Lobule

Testis

SeptumTunica albugineaTunica vaginalisCavity oftunica vaginalis

Spermatic cord

Seminiferoustubule

Blood vesselsand nerves

(a)


The Testes

• Interstitial (Leydig) cells outside seminiferous tubules produce androgens

Copyright © 2010 Pearson Education, Inc. Figure 27.3c

Spermatogeniccells in tubuleepithelium

Interstitial cells

Areolarconnective tissue

SpermMyoidcells

(c)

Seminiferoustubule


The Penis

• Penis consists of• Root and shaft ends in glans penis• Prepuce, or foreskin—the cuff of loose skin

covering the glans• Circumcision - surgical removal of foreskin • Crura

• Proximal end surrounded by ischiocavernosus muscle; anchors penis to pubic arch


Urinary bladder

Dorsal vesselsand nerves

Skin

Deep arteries (b)

(a)

Bulbourethral gland and ductUrogenital diaphragmBulb of penis

Corpora cavernosa

Corpus spongiosum

Section of (b)Spongy urethra

Glans penisPrepuce (foreskin)External urethral orifice

Corpora cavernosaUrethraTunica albuginea of erectile bodies

Corpus spongiosum

Crus of penisBulbourethral duct openingDuctus deferens

Ampulla of ductus deferens

Prostatic urethraOrifices of prostatic ducts

Prostate

Membranous urethra

Root of penis

Shaft (body) of penis

Ejaculatory ductSeminal vesicle

Epididymis

Testis

Ureter


Accessory Glands: Seminal Vesicles

• Produces viscous alkaline seminal fluid • Fructose, ascorbic acid, coagulating enzyme

(vesiculase), and prostaglandins

• 70% of the volume of semen


Accessory Glands: Prostate

• Encircles urethra inferior to bladder

• Secretes milky, slightly acid fluid:• Contains citrate, enzymes, and prostate-

specific antigen (PSA)

• Activation of sperm


Accessory Glands: Bulbourethral Glands (Cowper’s Glands)• Pea-sized glands

• Prior to ejaculation, produce thick, clear mucus• Lubricates glans penis

• Neutralizes traces of acidic urine in urethra


Semen

• Contains fructose, protects and activates sperm, and facilitates movement (relaxin)

• Prostaglandins• Decrease viscosity of mucus in cervix

• Stimulate reverse peristalsis in uterus

• 2–5 ml of semen ejaculated, containing 20–150 million sperm/ml


Male Sexual Response

• Erection:• Parasympathetic reflex promotes release of

nitric oxide (NO)• NO causes erectile tissue to fill with blood• Expansion of corpora cavernosa

• Compresses drainage veins and maintains engorgement

• Corpus spongiosum keeps the urethra open


Urinary bladder

Dorsal vesselsand nerves

Skin

Deep arteries (b)

(a)

Bulbourethral gland and ductUrogenital diaphragmBulb of penis

Corpora cavernosa

Corpus spongiosum

Section of (b)Spongy urethra

Glans penisPrepuce (foreskin)External urethral orifice

Corpora cavernosaUrethraTunica albuginea of erectile bodies

Corpus spongiosum

Crus of penisBulbourethral duct openingDuctus deferens

Ampulla of ductus deferens

Prostatic urethraOrifices of prostatic ducts

Prostate

Membranous urethra

Root of penis

Shaft (body) of penis

Ejaculatory ductSeminal vesicle

Epididymis

Testis

Ureter


Male Sexual Response

• Ejaculation• Sympathetic reflex

• Ducts and accessory glands contract and empty their contents

• Bladder sphincter muscle constrict,


Meiosis

• Gamete formation involves meiosis• Nuclear division in 2n to n• Produces four daughter cells

• Introduces genetic variation

Copyright © 2010 Pearson Education, Inc. Figure 27.5 (1 of 2)

Mother cell(before chromosome replication)

Chromosomereplication

Chromosomereplication

2n = 4MITOSIS

ReplicatedchromosomeProphase

Chromosomesalign at themetaphase plate

Sister chromatids separate during anaphase

2n 2n

Metaphase

Daughtercells ofmitosis

Tetrad formed bysynapsis of replicated homologouschromosomes

Tetrads align at themetaphase plate

Homologous chromosomesseparate but sister

chromatids remain together during anaphase I

No further chromosomalreplication; sister chromatids

separate duringanaphase II

Daughter cells of meiosis II(usually gametes)

n n n n

Prophase I

Metaphase I

Daughter cellsof meiosis I

Meiosis II

MEIOSIS

Copyright © 2010 Pearson Education, Inc. Figure 27.5 (2 of 2)

MITOSIS MEIOSISOne, consisting of prophase, metaphase,anaphase, and telophase.

Number ofdivisions

Synapsis of homologouschromosomesDaughter cell number and genetic compositionRoles in the body

Two, each consisting of prophase, metaphase, anaphase, and telophase. DNA replication does not occur between the two nuclear divisions.

Does not occur. Occurs during mitosis I; tetrads formed, allowing crossovers.

Two. Each diploid (2n) cell is identical tothe mother cell.

Four. Each haploid (n) cell contains half as many chromosomes as the mother cell and is genetically different from the mother cell.

For development of multicellular adultfrom zygote. Produces cells for growthand tissue repair. Ensures constancy ofgenetic makeup of all body cells.

Produces cells for reproduction (gametes). Introduces genetic variability in the gametes and reduces chromosomal number by half so that when fertilization occurs, the normal diploid chromosomal number is restored (in humans, 2n = 46).


Basal lamina

Spermatogonium(stem cell)

Cytoplasm of adjacentsustentacular cells Sustentacular

cell nucleus

Tight junction betweensustentacular cells

Lumen ofseminifer-ous tubule

Late spermatids

Earlyspermatids

Secondaryspermatocytes

Cytoplasmicbridge

Primaryspermatocyte

Spermatozoa

Type B daughter cell

Type A daughter cellremains at basal laminaas a stem cell

(c) A portion of the seminiferous tublule wall, showing the spermatogenic cells surrounded by sustentacular cells (colored gold)


Spermatogenesis

• Begins at puberty

Type A cells maintain germ cell line at basal laminaType B cells move toward lumen and develop

Copyright © 2010 Pearson Education, Inc. Figure 27.7b

Basal laminaSpermatogonium(stem cell)

Mitosis

Growth

Late spermatids

Early spermatids


Primaryspermatocyte

Spermatozoa


Enters meiosis I and moves toadluminalcompartmentMeiosis IcompletedMeiosis II


(b) Events of spermatogenesis, showing the relative position of various spermatogenic cells


Sperm

• Major regions

1. Head: genetic region; nucleus and helmetlike acrosome containing hydrolytic enzymes that enable the sperm to penetrate an egg

2. Midpiece: metabolic region; mitochondria

3. Tail: locomotor region; flagellum

Copyright © 2010 Pearson Education, Inc. Figure 27.8a, b

CentriolesSpermatidnucleus

GolgiapparatusAcrosomal

vesicleMitochondria

Approximately 24 days

Excesscytoplasm

Nucleus

Acrosome

MicrotubulesFlagellum

Tail

Midpiece Head(a)

(b)

1 2

3

4

5

6 7


Role of Sustentacular Cells

• Provide nutrients

• Dispose of excess cytoplasm during spermiogenesis

• Tight junctions form a blood-testis barrier • Prevents sperm antigens from escaping into

blood no immune system

• Sperm are not formed until puberty, they are absent during immune system development, and would not be recognized as “self”


Basal lamina

Spermatogonium(stem cell)

Cytoplasm of adjacentsustentacular cells Sustentacular

cell nucleus

Tight junction betweensustentacular cells

Lumen ofseminifer-ous tubule

Late spermatids

Earlyspermatids


Cytoplasmicbridge

Primaryspermatocyte

Spermatozoa



(c) A portion of the seminiferous tublule wall, showing the spermatogenic cells surrounded by sustentacular cells (colored gold)

Figure 27.1

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