Chapter 28 Reproductive System

Similarities between male and female systems Gonads are primary sex organs ovaries; testes Gonads produce haploid sex cells called gametes haploid = half the number of chromosomes of the parent cells gametes produced by meiosis ovaries produce oocytes (eggs) testes produce sperm Gonads produce large amounts of sex hormones estrogen and progesterone are most important in females androgens (including testosterone) are most important in males

Similarities between male and female systems Reproductive systems are dormant until puberty Accessory organs carry gametes from gonads to site of fertilization Fertilization = fusion of sperm and egg into zygote

Female anatomy Ovaries are almond-size Ureter Uterine (fallopian) tube Ovary Fimbriae of uterine tube Uterus Ovaries are almond-size Connected to uterus by fallopian (uterine) tubes Fimbraiae are finger-like projections from fallopian tube and catch released eggs

Female anatomy Fig. 28.2 Uterus is thick-walled, muscular organ Usually anteverted (pointed toward the front); may become retroverted in older women Opening to uterus is the cervix Uterus Cervix of uterus Rectum Vagina

Female anatomy Fig. 28.2 Rectum Vagina Clitoris External urethral orifice Vagina is thick-walled, fibromuscular tube that connects orifice to uterus Folds of skin outside vagina are labia minora and labia majora Clitoris is highly sensitive, erectile bulb of skin homologous to penis Vaginal orifice Labium minus Labium majus

(part of broad ligament) Ovarian artery Fig. 28.3 Ovarian vein Suspensory ligament Ovarian ligament Mesosalpinx (part of broad ligament) Uterine tube Infundibulum Fimbriae Ovary Uterus Broad ligament is a drape of peritoneum over uterus Ovaries held in place by ovarian ligaments and suspensory ligaments Ovarian artery and ovarian vein supply each artery Broad ligament Uterine artery Posterior Uterine vein Uterine tube Tunica albuginea Ureter Medulla Mesosalpinx Cortex Cervix Vagina Mesovarium Hilum Germinal epithelium (b) Lateral sectional view

Fig. 28.3(b) Lateral sectional view of ovary Posterior Fig. 28.3(b) Lateral sectional view of ovary (b) Lateral sectional view Uterine tube Ovary is surrounded by germinal epithelium cuboidal epithelium Tunica albuginea is connective tissue capsule Tunica albuginea Medulla Cortex Germinal epithelium Anterior

Fig. 28.3(b) Lateral sectional view of ovary Posterior Fig. 28.3(b) Lateral sectional view of ovary (b) Lateral sectional view Uterine tube Outer portion is cortex contains follicles Inner portion is medulla made of connective tissue, branches of blood vessels, lymph vessels, and nerves Tunica albuginea Medulla Cortex Germinal epithelium Anterior

Fig. 28.4(a) Cross section of ovary Ovarian follicles contain an oocyte and follicle cells Before birth, all oocytes develop and start meiosis, pause in Prophase I of meiosis, called primordial follicles each has 23 pairs of chromosomes at birth 1.5 million primordial follicles Primary oocyte Follicle cells Primordial follicles LM 500x (b) Primordial follicles Medulla Primordial follicles Cortex

(c) Primary follicle Granulosa cells Primary oocyte Primary follicle Primary follicles Fig. 28.4 Beginning at puberty, each month, about 20 primordial follicles mature into primary follicles primary oocyte surrounded by 1+ layer of granulosa cells secretes estrogen as it matures estrogen spurs changes in uterine lining LM 500x

Fig. 28.4 Each primary follicle develops into a secondary follicle Corona radiata Primary oocyte Zona pellucida Each primary follicle develops into a secondary follicle primary oocytes many layers of granulosa cells fluid-filled space called antrum zona pellucida and corona radiata are protective layers Antrum Secondary follicle Granulosa cells LM 50x Secondary follicle Zona pellucida Antrum

Fig. 28.4 One or two secondary follicles develop into mature (vesicular) follicles secondary oocyte has stopped in second half of meiosis two cells produced, each has 23 chromosomes one cell will become egg, one is polar body, degenerates many layers of granulosa cells large antrum; still has zona pellucida and corona radiata Mature follicle Antrum Secondary oocyte Zona pellucida Corona radiata Zona pellucida Ovulated secondary oocyte Antrum LM 100x (e) Mature follicle Secondary oocyte Zona pellucida Corona radiata

Fig. 28.4 Each month, one mature follicle ruptures and expels its oocyte process called ovulation Mature follicle Antrum Secondary oocyte Zona pellucida Corona radiata Zona pellucida Ovulated secondary oocyte

Corpus luteum LM 25x (f) Corpus luteum Developing corpus luteum Fig. 28.4 After ovulation, some of follicle stays in ovary, becomes corpus luteum secretes sex hormones progesterone and estrogen stimulate continued buildup of uterine lining prepare uterus for implantation of zygote

Fig. 28.4 Meiosis completed only if fertilization occurs LM 80x Corpus albicans (g) Corpus albicans Fig. 28.4 Meiosis completed only if fertilization occurs one egg and second polar body formed; polar body degenerates If fertilization does occur, corpus luteum continues producing hormones until 3 months gestation embryo begins to produce own hormones

Fig. 28.4 If fertilization does not occur, corpus luteum degenerates into corpus albicans, usually completely resorbed by ovary production of hormones decreases, menstruation occurs as uterine lining is shed If fertilization does occur Corpus albicans LM 80x (g) Corpus albicans

(arrested in prophase I) (arrested in metaphase II) Fig. 28.5 Before birth (embryonic and fetal period) Oogenesis (development of oocytes) Follicle development Micrograph examples Oogonia are diploid cells (containing 23 pairs of chromosomes, or 46 total) that are the origin of oocytes. Mitotic divisions of oogonia produce primary oocytes, which are diploid cells. 46 Oogonium Primary oocytes Mitosis Oocyte Follicle cells Primary oocytes start the process of meiosis but are arrested in prophase I. Primary oocyte (arrested in prophase I) 46 Primordial follicle LM 500x Childhood Ovary is inactive. It houses primordial follicles. Some atresia of primordial follicles occurs. Meiosis I arrested Monthly, from puberty to menopause Up to about 20 primordial follicles mature into primary follicles every month. Some primary follicles mature into secondary follicles. Primary follicles that do not mature undergo atresia. Primary follicle LM 500x 46 Primary oocyte (arrested in prophase I) Secondary follicle Meiosis II arrested LM 50x Typically only one secondary follicle develops into a mature follicle, where the primary oocyte completes the first meiotic division to produce a polar body and a secondary oocyte. The secondary oocyte is a haploid cell (containing 23 chromosomes only) that is arrested in the second meiotic metaphase. Secondary oocyte (arrested in metaphase II) Mature follicle 23 23 LM 100x First polar body (degenerates) Ovulation Ovulated secondary oocyte Sperm 23 LM 75x 23 Meiosis II completed (if fertilization occurs) If the secondary oocyte is fertilized, it completes the second meiotic division and becomes an ovum. If the secondary oocyte is not fertilized, it degenerates. Corpus luteum LM 25x 23 23 Second polar body (degenerates) Ovum Corpus albicans LM 80x

Fig. 28.6 Ovarian cycle Primary follicle Secondary follicle Mature Ovulation Corpus luteum forms Regression Corpus albicans Days 1 3 5 7 9 11 13 15 17 19 21 23 25 27 1 Follicular phase Ovulation Luteal phase Gonadotropin levels FSH LH Days 1 3 5 7 9 11 13 15 17 19 21 23 25 27 1 Ovulation Ovarian hormone levels Estrogen Progesterone Days 1 3 5 7 9 1 1 13 15 17 19 21 23 25 27 1 Uterine cycle Menstrual flow Functional layer Basal layer Days 1 3 5 7 9 1 1 13 15 17 19 21 23 25 27 1 Menstrual phase Proliferative phase Secretory phase

First menstrual cycle = menarche End of menstrual cycles = menopause, no menstrual period for one year (not pregnant) Usually age 45-55 Perimenopause is time before menopause begins estrogen levels begin to drop irregular or skipped periods

Uterine tube AKA Fallopian tube, oviduct Fig. 28.7 Fimbriae Uterine tube Uterine tube AKA Fallopian tube, oviduct Max. length 10-12 cm by puberty Fimbriae enclose ovary not actually attached to ovary

Ectopic pregnancy Zygote implants in fallopian tube instead of uterus Tube unable to expand to accommodate growing embryo develops for up to 8 weeks Symptoms: severe cramping Tube may burst if embryo not removed

Fig. 28.7 Muscularis Lumen of uterine tube Mucosa Histology Simple ciliated columnar epithelium Mucosa is ciliated columnar epithelium and areolar connective tissue folds in lumen reduce diameter beating of cilia draws egg into tube and carries it toward uterus LM 35x Uterine tube LM 400x Ovarian ligament (a) Posterior view

Fig. 28.7 Muscularis Lumen of uterine tube Mucosa Histology Simple ciliated columnar epithelium Muscularis has inner circular layer and outer longitudinal layer becomes thicker near uterus peristaltic contractions move egg to uterus LM 35x Uterine tube LM 400x Ovarian ligament (a) Posterior view

Fig. 28.7 Fundus is superior region of uterus, between fallopian tubes Lumen of uterus Fundus is superior region of uterus, between fallopian tubes Major part of uterus is body Isthmus is narrow inferior region Body of uterus Broad ligament Isthmus Vagina (a) Posterior view

Fig. 28.7 Cervix is narrow portion of uterus that projects into vagina (a) Posterior view Cervix is narrow portion of uterus that projects into vagina Mucin-secreting glands in cervix create mucus plug at external opening to vagina probably barrier to prevent pathogens from entering uterus plug thins during ovulation to allow sperm entry into uterus NOT thick enough to prevent sperm passage during rest of cycle Cervix

Fig. 28.7 Wall of uterus has 3 tunics (a) Posterior view Wall of uterus has 3 tunics Perimetrium is serosa, continuous with broad ligament Myometrium is muscular layer 3 intertwining layers of muscle thickens during pregnancy Endometrium Myometrium Wall of uterus Perimetrium Epithelium Lumen of uterus Functional layer Uterine glands Endometrium Basal layer Myometrium LM 45x (c) Uterine wall

Fig. 28.7 Endometrium is innermost layer, mucosa (a) Posterior view Endometrium is innermost layer, mucosa simple columnar epithelium lamina propria has uterine glands that enlarge during uterine cycle divided into 2 layers functional layer is superficial, shed during menstruation basal layer is permanent, doesn’t change much during uterine cycle Endometrium Myometrium Wall of uterus Perimetrium Epithelium Lumen of uterus Functional layer Uterine glands Endo-metrium Basal layer Myometrium LM 45x (c) Uterine wall

Cervical cancer detected through Pap smear Speculum inserted in vagina, scraping of cells taken from cervix

Page 852 Normal epithelial cells Normal epithelial cells Dysplastic cells LM 140x LM 160x Normal Pap smear. Abnormal Pap smear. Cells from cervix examined under microscope for abnormal cells, called dysplastic cells May be sign of cervical cancer

Fig. 28.8 Vagina is muscular tube ~10cm long Functions as birth canal Wall is relatively thin, distensible Functions as birth canal Lots of blood and lymph vessels Rugae present, especially in inferior region Formed from mucosal tissue

Vaginal orifice is opening to vagina Mucosal tissue projects into vaginal opening to create hymen Sometimes broken during first sexual intercourse May be broken by masturbation, tampon use, certain activities (horseback riding) Shape, thickness of hymen may differ dramatically

Fig. 28.9 External genitalia = vulva Mons pubis (a) Superficial structures of external genitalia Anus Perineum Labia majora Labia minora Prepuce Glans of clitoris Urethral opening Vestibule Vaginal orifice Openings for greater vestibular glands External genitalia = vulva includes labia majora and minora, clitoris, vestibule vestibule is opening between labia minora Mons pubis is skin and connective tissue anterior to pubic symphysis covered with pubic hair after puberty labia majora also has pubic hair Labia minora are highly vascularized, have sebaceous glands

Fig. 28.9 Bulb of the vestibule is erectile body on either side of vaginal orifice Becomes erect and increasingly sensitive during intercourse Greater vestibular glands secrete mucin forms mucus, acts as lubricant during intercourse Clitoris is erectile body has specialized sensory nerve receptors held to pubic arch by crus Pubic symphysis Body of clitoris Crus of clitoris Bulb of the vestibule Greater vestibular gland (b) Deep structures of external genitalia

Fig. 28.9 Glans is layer of skin over clitoris highly sensitive Prepuce is an external fold of labia minora forms hood over clitoris Mons pubis Glans of clitoris Prepuce Urethral opening Labia minora Vestibule Vaginal orifice Openings for greater vestibular glands Labia majora Perineum Anus (a) Superficial structures of external genitalia

Male hyena Female hyena

Female hyena’s clitoris is extended, looks like penis Labia are fused, look like scrotum Vaginal orifice is at tip of clitoris

Contraception includes barrier, chemical, and surgical methods. Page 856 (a) Condoms (b) Spermicidal foams (c) Diaphragm Each ductus deferens is tied off and cut Uterine tubes are tied off and cut (d) Oral contraceptive (e) Intrauterine device (IUD) (f) Tubal ligation (g) Vasectomy

Male anatomy Fig. 28.11 Ureters Urinary bladder Ampulla of ductus deferens Pubic symphysis Seminal vesicle Ductus (vas) deferens Ejaculatory duct Prostate gland Bulbourethral gland Urethra Anus Penis Epididymis Testis Glans Scrotum

Testes (sing. testis) are primary male sex organ Fig. 28.12 Testes (sing. testis) are primary male sex organ produce sperm and hormones Scrotum holds testes away from body ideal temperature for sperm is 3°C below body temp homologous with female labia majora ridge at center is raphe wall of scrotum has 3 layers skin superficial fascia dartos muscle relaxes at high temps, contracts at low temps to maintain testes at proper temp. Internal spermatic fascia Dartos muscle Raphe Scrotum

Blood vessels and nerves to testes travel through spermatic cord Fig. 28.12 Ductus (vas) deferens Superficial inguinal ring Pampiniform plexus Structures within spermatic cord Spermatic cord External spermatic fascia Testicular artery Cremaster muscle within cremasteric fascia Testicular nerve Layers of spermatic cord wall Epididymis Internal spermatic fascia Blood vessels and nerves to testes travel through spermatic cord originates near inguinal ligament Testis

Fig. 28.12 3 layers of spermatic cord External spermatic fascia Superficial inguinal ring 3 layers of spermatic cord External spermatic fascia formed from aponeurosis of external oblique muscle Cremaster muscle (formed from muscle fiber extensions of internal oblique muscle) and cremasteric fascia (formed from aponeurosis) Internal spermatic fascia formed from fascia deep to abdominal muscles Spermatic cord External spermatic fascia Cremaster muscle within cremasteric fascia Layers of spermatic cord wall Internal spermatic fascia

Fig. 28.12 Within spermatic cord Testicular artery (branches from aorta) Pampiniform plexus is plexus of veins cools blood traveling to testes Testicular nerves Vas deferens Ductus (vas) deferens Pampiniform plexus Structures within spermatic cord Testicular artery Testicular nerve Epididymis Testis

Each testis covered by tunica vaginalis Fig. 28.13 Spermatic cord Each testis covered by tunica vaginalis parietal and visceral layers Tunica albuginea is white, fibrous capsule deep to tunica vaginalis thickens at posterior margin, projects into testis forming mediastinum testis blood vessels, lymph vessels, and nerves exit testis here further projections into testis form septa divide testis into lobules Blood vessels and nerves Head of epididymis Duct of epididymis Ductus deferens Seminiferous tubule Efferent ductule Mediastinum testis (housing rete testis) Septum Lobule Visceral layer of tunica vaginalis Body of epididymis Parietal layer of tunica vaginalis Tail of epididymis Tunica albuginea (a) Testis

Fig. 28.13 Spermatic cord Each lobule contains >4 seminiferous tubules surrounded by interstitial spaces cells in interstitial spaces secrete androgens Blood vessels and nerves Head of epididymis Duct of epididymis Ductus deferens Seminiferous tubule Efferent ductule Mediastinum testis (housing rete testis) Septum Lobule Visceral layer of tunica vaginalis Body of epididymis Parietal layer of tunica vaginalis Tail of epididymis Tunica albuginea (a) Testis

Sperm are formed within seminiferous tubules Fig. 28.13 (b) Seminiferous tubule, cross section LM 250x Interstitial cells Seminiferous tubule Tubule lumen Sustentacular cells Germ cells Sperm Spermatids Spermatogonia Sperm are formed within seminiferous tubules Sustentacular cells assist with sperm development, nourish developing sperm release inhibin when sperm count high to slow sperm production tight junctions between cells create blood-testis barrier to protect developing sperm

Fig. 28.13 Germ cells perform spermatogenesis, creation of sperm cells (b) Seminiferous tubule, cross section LM 250x Interstitial cells Seminiferous tubule Tubule lumen Sustentacular cells Germ cells Sperm Spermatids Spermatogonia Germ cells perform spermatogenesis, creation of sperm cells Spermatogonia are primordial germ cells (diploid) divide by mitosis, produce one new germ cell and one primary spermatocyte (“committed” cell will become sperm)

Fig. 28.14 Spermatogonium produces primary spermatocyte Interstitial cells Spermatogonium produces primary spermatocyte 2. Primary spermatocyte undergoes meiosis I, becomes haploid secondary spermatocyte 3. Secondary spermatocyte undergoes meiosis II, produces 2 haploid spermatids 4. Morphological changes produce sperm Interstitial space Sustentacular cell Spermatogonium 46 1 Mitotic division 46 Primary spermatocyte 46 2 Meiosis I Secondary spermatocyte 23 23 Wall of seminiferous tubule 3 Meiosis II 23 23 23 23 Spermatid 4 23 23 23 23 Spermatids becoming sperm

Fig. 28.14 Development of spermatids Developing acrosome cap Mitochondria Spermatid nucleus Acrosome cap Nucleus Mitochondria Excess cytoplasm Developing acrosome cap Spermatid nucleus Developing flagellum Acrosome cap Spermatid nucleus

Fig. 28.14 Spermatids develop into mature sperm (AKA spermatozoa) Acrosome cap Spermatids develop into mature sperm (AKA spermatozoa) Acrosome cap contains digestive enzymes help penetrate secondary oocyte for fertilization Tail is made of microtubules Mitochondria in midpiece provide energy to move tail Nucleus Head Mitochondria Midpiece Tail (flagellum) Sperm (b) Spermiogenesis

Fig. 28.13 Sperm leave seminiferous tubule not yet mature Travel to epididymis, where they mature structure wraps around testis head on superior surface, tale inferior duct of epididymis 4-5m long Spermatic cord Blood vessels and nerves Head of epididymis Duct of epididymis Ductus deferens Seminiferous tubule Efferent ductule Mediastinum testis (housing rete testis) Septum Lobule Visceral layer of tunica vaginalis Body of epididymis Parietal layer of tunica vaginalis Tail of epididymis Tunica albuginea (a) Testis

Cross-section of epididymis shows many ducts filled with sperm Fig. 28.15 (c) Epididymis LM 50x Sperm in lumen of duct of epididymis Section of duct of epididymis Cross-section of epididymis shows many ducts filled with sperm If not ejaculated, sperm resorbed by lining of duct of epididymis

Sperm leave epididymis, travel to vas deferens (ductus deferens) Fig. 28.13 Sperm leave epididymis, travel to vas deferens (ductus deferens) travel through spermatic cord Sperm moved by sterocilia sperm do not swim prior to ejaculation Spermatic cord Blood vessels and nerves Head of epididymis Duct of epididymis Ductus deferens Seminiferous tubule Efferent ductule Mediastinum testis (housing rete testis) Septum Lobule Visceral layer of tunica vaginalis Body of epididymis Parietal layer of tunica vaginalis Tail of epididymis Tunica albuginea (a) Testis

Vas deferens has thin mucosa, very thick muscularis Fig. 28.15 Adventitia Vas deferens has thin mucosa, very thick muscularis Muscularis is 3 layers longitudinal circular contractions move sperm through duct Mucosa LM 32x Muscularis Mucosa LM 500x (b) Ductus deferens

As it reaches prostate gland, enlarges and forms ampulla Fig. 28.15 Urinary bladder Ureter As it reaches prostate gland, enlarges and forms ampulla Seminal vesicles secrete viscous, whitish fluid containing fructose to nourish sperm prostaglandins to promote widening of cervix bicarbonate to buffer acidic environment of vagina Seminal vesicles merge with vas deferens to create ejaculatory duct (meets with prostatic urethra) Ampulla Seminal vesicle Ejaculatory duct Prostate gland Prostatic urethra Membranous urethra Bulbourethral gland Bulb Urogenital diaphragm Crus Ductus (vas) deferens Corpus cavernosum Epididymis Testis Penis Corpus spongiosum Spongy urethra Glans (a) Posterior view

Many mucosal folds visible in seminal vesicle Fig. 28.16 Many mucosal folds visible in seminal vesicle Mucosal folds in seminal vesicle LM 25x (a) Seminal vesicle

Prostate gland produces mucin, secretes milky fluid with Fig. 28.15 Urinary bladder Ureter Prostate gland produces mucin, secretes milky fluid with citric acid to nourish sperm seminalplasmin, an antibiotic to combat UTIs prostate-specific antigen (PSA) helps liquify semen following ejaculation Ampulla Seminal vesicle Ejaculatory duct Prostate gland Prostatic urethra Membranous urethra Bulbourethral gland Bulb Urogenital diaphragm Crus Ductus (vas) deferens Corpus cavernosum Epididymis Testis Penis Corpus spongiosum Spongy urethra Glans (a) Posterior view

Tubuloalveolar glands produce seminal secretions Fig. 28.16 Tubuloalveolar glands produce seminal secretions If prostatic fluid solidifies, becomes prostatic concretions within gland lumens Prostatic concretions Tubuloalveolar glands in prostate gland LM 80x (b) Prostate gland

Bulbourethral glands are located within urogenital diaphragm Fig. 28.15 Urinary bladder Ureter Bulbourethral glands are located within urogenital diaphragm Produce clear, viscous mucus that lubricates and buffers urethra prior to ejaculation Ampulla Seminal vesicle Ejaculatory duct Prostate gland Prostatic urethra Membranous urethra Bulbourethral gland Bulb Urogenital diaphragm Crus Ductus (vas) deferens Corpus cavernosum Epididymis Testis Penis Corpus spongiosum Spongy urethra Glans (a) Posterior view

When released during intercourse called ejaculate Fig. 28.15 Urinary bladder Ureter Semen contains sperm products of seminal vesicles, prostate gland, bulbourethral glands When released during intercourse called ejaculate usually 3-5 ml 200-500 million sperm per ejaculation 2 weeks from seminiferous tubules to ejaculate Sperm number may decrease with sexual activity, volume won’t Ampulla Seminal vesicle Ejaculatory duct Prostate gland Prostatic urethra Membranous urethra Bulbourethral gland Bulb Urogenital diaphragm Crus Ductus (vas) deferens Corpus cavernosum Epididymis Testis Penis Corpus spongiosum Spongy urethra Glans (a) Posterior view

As it reaches prostate gland, enlarges and forms ampulla Fig. 28.15 Urinary bladder Ureter As it reaches prostate gland, enlarges and forms ampulla Seminal vesicles secrete viscous, whitish fluid containing fructose to nourish sperm prostaglandins to promote widening of cervix bicarbonate to buffer acidic environment of vagina Ampulla Seminal vesicle Ejaculatory duct Prostate gland Prostatic urethra Membranous urethra Bulbourethral gland Bulb Urogenital diaphragm Crus Ductus (vas) deferens Corpus cavernosum Epididymis Testis Penis Corpus spongiosum Spongy urethra Glans (a) Posterior view

Male external genitalia include penis and scrotum Fig. 28.17 Male external genitalia include penis and scrotum Root of penis is internal to body surface Bulb of penis attaches to bulbospongiosus muscle Crus of penis attach to pubic arch Body or shaft of penis is elongated and movable Membranous urethra Pubic symphysis Bulb of penis Right crus of penis Body of penis Root of penis Root of penis Corpora cavernosa Corpus spongiosum Glans Scrotum External urethral orifice (a) Anterolateral view

Glans is tip of penis, contains external urethral orifice Fig. 28.17 Glans is tip of penis, contains external urethral orifice Foreskin is prepuce Average length, pubic symphysis to tip of glans = 13cm (~5 in.) Avg. circumference 11.7 cm Membranous urethra Pubic symphysis Bulb of penis Right crus of penis Body of penis Root of penis Root of penis Corpora cavernosa Corpus spongiosum Glans Scrotum External urethral orifice (a) Anterolateral view

Page 868 (a) Circumcised penis (b) Uncircumcised penis Prepuce

3 erectile bodies within penis Fig. 28.17 Dorsal vein 3 erectile bodies within penis Corpora cavernosa (pl.) terminates in shaft of penis Corpus spongiosum continues to tip of glans contains spongy urethra Dorsal artery Dorsal nerve Deep dorsal vein Tunica albuginea Central artery Corpus cavernosum Venous spaces Deep fascia Corpus spongiosum Superficial fascia Skin Spongy urethra (b) Cross section

Erectile bodies have venous spaces surrounding central artery Fig. 28.17 Dorsal vein Erectile bodies have venous spaces surrounding central artery Sexual excitement causes blood to flow into central artery and venous spaces Erectile bodies compress veins, blood cannot flow out, causes erection Dorsal artery Dorsal nerve Deep dorsal vein Tunica albuginea Central artery Corpus cavernosum Venous spaces Deep fascia Corpus spongiosum Superficial fascia Skin Spongy urethra (b) Cross section

Aging and Reproductive systems “Male menopause” = male climacteric slight decrease in size of testes decreased testosterone levels Prostate enlargement may cause erectile dysfunction (inability to achieve erection) or impotence (inability to maintain erection) Risk factors: age, heart disease, diabetes, smoking, prostate surgery