1. REPRODUCTIVE SYSTEM: MALE

2. Common Elements of the Two Systems
Both females and males have primary reproductive organs, gonads
Ovaries in females; testes in males
Produce sex cells called gametes
Unite at fertilization to initiate formation of new individual
Produce large amounts of sex hormones
Affect maturation, development, activity of reproductive organs
Both sexes also have accessory reproductive organs
E.g., ducts to carry gametes away from gonads
Toward site of fertilization (females)
Toward outside of body (males)

3. Common Elements of the Two Systems
Sexual union—copulation, coitus, sexual intercourse
If fertilization occurs, female reproductive tract provides
Support
Protection
Nourishment

4. Sexual Maturation in Females and Males
Puberty
Onset during adolescence
External sex characteristics develop
E.g., breast enlargement in females
E.g., pubic hair growth
Gametes begin to mature
Gonads start to secrete sex hormones

5. Hormones initiating puberty
Hypothalamus begins to secrete gonadotropin- releasing hormone (GnRH)
Stimulates anterior pituitary to release two hormones
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Gonads begin to produce significant levels of sex hormones
Start process of gamete and sexual maturation

6. Gametes Produced by males and females
Female produces and releases single gamete monthly
Oocyte
Male produces large numbers of gametes
100 million/day
Stored for short time only
If not expelled from body, resorbed

7. 28.1c Anatomy of the Perineum 1
Diamond-shaped area between thighs
Boundaries
Pubic symphysis anteriorly
Ischial tuberosities laterally
Coccyx posteriorly
May be partially torn during childbirth

8. Gametogenesis Gametogenesis: Process of forming human sex cells
Sex cells = gametes
Female gametes, secondary oocytes (“eggs”)
Male gametes, sperm
Begins with cell division, meiosis
Similar process in females and males, a few differences

9. A Brief Review of Heredity
Hereditary information
Carried on 23 pairs of chromosomes in human body cells
22 pairs of autosomes, 1 pair of sex chromosomes
Autosomes
Contain genes that code for cellular functions
Determine most human characteristics
E.g., eye and hair color, height, skin pigmentation
A pair of matching autosomes, homologous chromosomes

10. Hereditary information (continued)
Sex chromosomes
Two X chromosomes or one X and one Y
Female (XX) or male (XY)
Also, some genes code for other functions
One member of chromosome pair inherited from each parent

11. Genetic Versus Phenotypic Sex
Genetic sex
Genotypic sex based on sex chromosomes inherited
Determined at fertilization
XX, genetic female
XY, genetic male
Phenotypic sex
Refers to the appearance of an individual’s internal and external genitalia
Ovaries and female external genitalia, phenotypic female
Testes and male external genitalia, phenotypic male
Apparent seventh week of development

12. Sex-determining region Y (SRY) gene
Located within larger testis-determining factor (TDF) region on Y chromosome
In genetic male with Y chromosome
SRY gene expressed
Produces proteins to stimulate androgens
Androgens initiate male phenotypic development
If Y chromosome is absent, or lacks or has an abnormal SRY gene, female phenotypic sex results

13. Hereditary information (continued)
Diploid cell
23 pairs of chromosomes
2n chromosomes
(n, unpaired chromosome number)
Haploid cell
23 chromosomes (not 23 pairs)
Chromosome number is n
Gametes from either sex
Ensures offspring do not receive 4n total chromosomes

14. An Overview of Meiosis Meiosis Starts with diploid parent cell
Produces haploid daughter cells, gametes
Begins with diploid parent cell in gonad (ovary or testis)
23 chromosomes from organism’s mother
23 chromosomes from organism’s father
Must undergo meiosis to produce haploid gametes

15. Mitosis Meiosis Somatic cell division
Produces 2 daughter cells genetically identical to parent cell
Diploid daughter cells
No crossing over
Meiosis
Sex cell division
4 daughter cells genetically different from parent cell
Haploid daughter cells
Includes crossing over
Genetic material exchanged between homologous chromosomes
Get genes from both parents on one chromosome

16. Meiosis I
Figure 28.2

17. Meiosis II
Figure 28.2

18. Male Reproductive System
Primary reproductive organs
Testes
Accessory reproductive organs
Ducts and tubules leading from testes to penis
Male accessory glands
Penis

19. Scrotum characteristics
Skin-covered sac between thighs
Provides cooler environment
Needed for sperm development and maturation
Homologous to labia majora in female
Scrotum wall
External layer of skin
Thin layer of superficial fascia internal to skin
Layer of smooth muscle, dartos muscle, internal to fascia

20. Scrotum characteristics (continued)
Spermatic cord
Multilayered structure traveling from abdomen to testis
Blood vessels and nerves supplying each testis
Originates in inguinal canal
Tubelike passageway through inferior abdominal wall
Spermatic cord wall consists of three layers

21. Scrotum characteristics (continued)
Testicular artery
Branch from abdominal aorta
Resides within spermatic cord
Pampiniform plexus
Plexus of veins surrounding testicular artery
Pre-cools arterial blood prior to reaching testes

22. Scrotum response to temperature changes
With elevated temperature
Relaxation of dartos muscle
Testes move inferiorly (away from body), cools testes
Cremaster muscle relaxes to allow testes to move inferiorly
With decreased temperature
Contraction of dartos and cremaster muscles
Testes and scrotum pulled closer to body
Helps conserve heat

23. ©McGraw-Hill Education/Christine Eckel
Scrotum and Testes
Figure 28.15
©McGraw-Hill Education/Christine Eckel

24. Male Pelvic Region
Figure 28.14

25. Testes and Spermatogenesis
Relatively small organs housed within the scrotum
Produce sperm and androgens
Covered anteriorly and laterally by a serous membrane
Tunica vaginalis
Derived from abdominal peritoneum
Outer parietal layer and inner visceral layer
Separated by cavity filled with serous fluid

26. 28.4b Testes and Spermatogenesis 2
Testes (continued)
Tunica albuginea
Thick fibrous capsule covering the testis
Deep to visceral layer of tunica vaginalis
Mediastinum testis
Thickening of tunica albuginea projecting into interior testis
Blood vessels, ducts, lymph vessels, nerves enter or leave through here
Septa
Internal projections of tunica albuginea
Subdivide internal space into 250 lobules

27. Testis
Figure 28.16a

28. Testes (continued) Seminiferous tubules
Extremely convoluted and elongated
Up to 4 per lobule
Nondividing support cells, sustentacular cells
Nourish developing sperm
Release hormone inhibin when sperm count high
Inhibits FSH secretion and regulates sperm production
Contain dividing germ cells continuously producing sperm

29. Testes (continued) Blood-testis barrier Interstitial spaces
Protects developing sperm from material in blood
Protects sperm from body’s leukocytes
Formed from tight junctions between sustentacular cells
Interstitial spaces
Spaces surrounding seminiferous tubules
Interstitial cells
Reside in interstitial spaces
Stimulated to produce androgens by luteinizing hormone
Most common androgen, testosterone
Majority released from interstitial cells; small amounts secreted by adrenal cortex

30. Hormonal regulation Hypothalamus secretes GnRH
Stimulates anterior pituitary to secrete FSH and LH
FSH and LH stimulate spermatogenesis and androgen production.
LH stimulates interstitial cells to secrete testosterone
FSH stimulates sustentacular cells to secrete androgen-binding protein (ABP)
Binds to testosterone, ensures high levels in testes

31. Hormonal regulation (continued)
3) Increased testosterone has multiple effects
Facilitates spermatogenesis
Also inhibits GnRH secretion and pituitary sensitivity to GnRH
Has negative feedback effect
4) Sustentacular cells release inhibin
Respond to rising sperm count levels
Causes inhibition of FSH secretion from anterior pituitary
Additional negative feedback mechanism

32. Hormonal regulation (continued)
Testosterone stimulates libido and development of secondary sex characteristics.
Hair growth in axillary and pubic regions, deeper voice, facial hair

33. Hormonal Regulation of Spermatogenesis and Androgen Production
Figure 28.17
(inset) ©Dr. Thomas Caceci, Virginia-Maryland Regional College of Veterinary Medicine

34. Spermatogenesis and spermiogenesis
Process of sperm development
Occurs within seminiferous tubule
Begins during puberty with significant levels of FSH and LH
Spermatogonia
Primordial germ cells from which all sperm develop
Diploid cells near base of seminiferous tubule
Surrounded by cytoplasm of sustentacular cell
Divide by mitosis into new spermatogonium and primary spermatocyte

35. Spermatogenesis and spermiogenesis (continued)
Primary spermatocyte
Diploid cells that undergo meiosis
Secondary spermatocytes
Two cells produced by primary spermatocyte from meiosis I
Haploid cells, 23 chromosomes only
Relatively closer to seminiferous tubule lumen
Spermatid
Formed when secondary spermatocytes complete meiosis II
Haploid cell near seminiferous tubule lumen
Circular appearance

36. Spermatogenesis and spermiogenesis (continued)
Final stage of spermatogenesis
Spermatid becomes mature spermatozoa, sperm
Excess cytoplasm shed and nucleus elongates
Acrosome cap forms over nucleus
Digestive enzymes to help penetrate secondary oocyte
Tail forms from organized microtubules in cell
Attached to midpiece region containing mitochondria and centriole
Mitochondria provide energy to move tail

37. Spermato-genesis and Spermio-genesis
Figure 28.18
(inset) ©Dr. Thomas Caceci, Virginia-Maryland Regional College of Veterinary Medicine

38. Duct System in the Male Reproductive Tract
Ducts within the testis
Right and left testes each with their own set of ducts
Transport and store sperm as they mature
Rete testis
Meshwork of interconnected channels in mediastinum testis
Receive sperm from seminiferous tubules
Lined by simple cuboidal epithelial
Short microvilli covering luminal surface
Merge to form efferent ductules

39. Ducts within the testis (continued)
Efferent ductules
Connect rete testis to epididymis
Lined with
Ciliated columnar epithelia— propel sperm toward epididymis
Nonciliated columnar epithelia— absorb excess fluid secreted by seminiferous tubules
Drain into epididymis

40. Epididymis Comma-shaped structure
Composed of internal duct and external covering of connective tissue
Head on superior testis surface
Body and tail on posterior surface of testis
Internally contains long duct of the epididymis
Lined with pseudostratified columnar epithelium with stereocilia
Stores sperm until they are fully mature and motile

41. Ductus deferens (vas deferens)
Sperm enter after leaving epididymis
Location
Within spermatic cord, extends through the inguinal canal, into pelvic cavity
Extends posteriorly along superolateral surface of the bladder
Travels inferiorly and ends close to where the bladder and prostate gland meet
Enlarges and forms ampulla
Unites with proximal seminal vesicle to form ejaculatory duct

42. Ductus deferens (continued)
Ductus deferens wall composition
Inner mucosa lined by pseudostratified ciliated columnar epithelium
Middle muscularis with three layers of smooth muscle
Inner longitudinal
Middle circular
Outer longitudinal
Necessary for moving sperm through ductus deferens
Sperm not motile until ejaculation from penis
Outer adventitia

44. Seminal fluid Alkaline secretion needed to neutralize vaginal acidity
Gives nutrients to sperm traveling in female reproductive tract
Produced by accessory glands
Seminal vesicles Prostate gland
Bulbourethral glands

45. Seminal vesicles
On posterior urinary bladder lateral to ampulla of ductus deferens
Wall contains mucosal folds of pseudostratified columnar epithelium
Medial portion merges with ductus deferens, forms ejaculatory duct
Secretes alkaline fluid with fructose and prostaglandins
Fructose nourishes sperm
Prostaglandins promote widening of external os of cervix

46. Prostate gland
Compact, walnut-shaped encapsulated organ immediately inferior to bladder
Submucosal glands produce mucin
Tubuloalveolar glands open into prostatic urethra
Together, contribute to seminal fluid
Secretes milky fluid rich in citric acid, seminalplasmin, prostate- specific antigen (PSA)
Citric acid, nutrient for sperm health
Seminalplasmin, antibiotic that combats urinary tract infection
PSA, enzyme to liquefy semen following ejaculation

47. Bulbourethral glands Paired glands located within urogenital diaphragm
Each with short duct projecting into base of penis
Enters spongy urethra
Tubuloalveolar glands
Produce clear, viscous mucin that forms mucus
Coats and lubricates urethra during intercourse

48. Ejaculatory duct Each duct is between 1 and 2 cm long
Epithelium of pseudostratified ciliated columnar epithelium
Conducts sperm and a component of seminal fluid toward urethra
Opens into prostatic urethra

49. Duct System and Accessory Glands in Male Reproductive Tract
Figure 28.19a

50. Urethra Transports semen from ejaculatory ducts to outside of body
3 components
Prostatic urethra extending from bladder through prostate gland
Membranous urethra continuing through urogenital diaphragm
Spongy urethra extending through penis

51. Semen Formed from seminal fluid and sperm
Called ejaculate when released during intercourse
200 to 500 million spermatozoa
Transit time from seminiferous tubules to ejaculate is about 2 weeks

52. Penis Forms external genitalia with scrotum Root Body
Internally attached portion of penis
Dilated internal to body surface
Forms bulb and crus of penis
Bulb attaching penis to bulbospongiosus muscle
Crus attaching penis to pubic arch
Body
Elongated movable portion

53. Penis (continued) Glans Prepuce (foreskin) Tip of penis
Contains external urethral orifice
Prepuce (foreskin)
Circular fold of skin
Skin attached to raised edge of the glans

54. Anatomy of the Penis: Anterolateral View
Figure 28.20a

55. Anatomy of the Penis: Cross Section
Figure 28.20b,c

56. Male Sexual Response Phases of male sexual response Excitement phase
Erectile bodies of penis composed of venous spaces surrounding artery
Blood fills venous spaces during excitement
Erectile body becomes rigid, erection
Compress veins draining blood from venous spaces
Blood unable to leave erectile bodies until excitement over
Parasympathetic innervation causes local release of nitric oxide
Responsible for increased blood flow and penis erection
Near the end of this phase, heart rate, blood pressure, and respiratory rate increase

57. Phases of male sexual response (continued)
Orgasm
Intense pleasure, tension release, expulsion of semen
Ductus deferens moves sperm toward urethra
Accessory glands secrete seminal fluid components
Combine with sperm to form semen
Internal urethral sphincter of bladder contracted
Ensures no urine enters urethra
Ejaculation at end of orgasm
Semen expelled from penis with contractions of muscles in urethra
Occurs due to sympathetic innervation

58. Phases of male sexual response (continued)
Resolution phase
Intense relaxation
Sympathetic division stimulated to contract central artery of penis
Stimulated to contract small muscles around erectile tissue
Both help expel engorged blood
Penis now soft and flaccid again
Followed by refractory period
No erection possible
Minutes to hours; longer with age

59. Formation of Indifferent Gonads and Genital Ducts
Duct and gonad development
Genital ridges
Form in fifth week of embryonic development
Form from intermediate mesoderm
Will form gonads
Medial to developing kidneys
Primordial germ cells
Migrate from yolk sac to genital ridges between weeks 5 and 6
Will form future gametes

60. Duct and gonad development (continued)
Mesonephric “Wolffian” ducts
Form most of male duct system
Connect mesonephros to developing urinary bladder
Paramesonephric “Mullerian” ducts
Form most of female duct system
Include uterine tubes, uterus, superior vagina
Appear lateral to mesonephric ducts

61. Duct and gonad development (continued)
Both duct systems developed in human embryos
Only one remaining in fetus
Female
Development of paramesonephric ducts
Degeneration of mesonephric ducts
Male
Development of mesonephric ducts
Degeneration of paramesonephric ducts

62. Internal Genitalia Development
Male development
About week 7, SRY gene
Begins influencing indifferent gonad to become testis
Forms sustentacular cells and interstitial cells
Anti-Müllerian hormone secreted by sustentacular cells
Inhibits development of paramesonephric ducts, which then degenerate
Development of mesonephric ducts
Weeks 8–12, begin to form male duct system
Efferent ductules, epididymis, vasa deferens, seminal vesicles, ejaculatory ducts

63. Male development (continued)
Prostate gland and bulbourethral glands
Form as endodermal “bud” from developing urethra
Gonad origination
Descend inferiorly from abdomen toward developing scrotum
Gubernaculum
Thin band of connective tissue attaching to testis
Assists in testis descent from abdomen to scrotum
Testis passively pulled into scrotum
Not completed until ninth month

64. Clinical View: Intersex Conditions (Disorders of Sex Development)
Discrepancy between genotype and external genitalia
True gonadal intersex, very rare
Individual with both ovarian and testicular structures
Ambiguous external genitalia
Genetic male or genetic female
Pseudohermaphroditism
Genetic sex and phenotypic sex do not match

65. 46 XY intersex 46 XX intersex
Genetic male with external genitalia resembling a female
From reduction or lack of male hormones during development
46 XX intersex
Genetic female with external genitalia resembling male
Clitoris enlarged and labia partially fused
May result if fetus exposed to excessive androgens
May result from congenital adrenal hyperplasia
Fetus’s adrenal glands producing excessive androgens

66. External Genitalia Development
Early genital structures
Male and female genitalia develop from same primordial structures
Appear by 6th week

67. Later genital structures
Appear similar until about week 12; differentiated around week 20
In absence of testosterone, female genitalia develop
Genital tubercle becomes clitoris
Urogenital folds do not fuse and become labia minora
Labioscrotal folds remain unfused and become labia majora
In presence of testosterone, male genitalia develop
Genital tubercle elongates and enlarges
Forms glans and dorsal side of penis
Urogenital folds fuse around urethra and form body of penis
Labioscrotal folds fuse forming scrotum

68. Development of External Genitalia: Week 20
Figure 28.22c

69. Puberty
Puberty
Period in adolescence where reproductive organs becoming fully functional
External sex characteristics becoming more prominent
E.g., breast enlargement and pubic hair growth
Timing affected by genetics, environmental factors, health of individual

70. Puberty initiation Hypothalamus beginning to secrete GnRH
Stimulates anterior pituitary to release FSH and LH
Levels very low until then
Stimulate significant levels of sex hormones
Start process of gamete and sexual maturation

71. Early signs of puberty development
Breast development in girls
Pubic and axillary hair in boys and girls
Menarche, about 2 years after first signs of puberty
Boys with testicle and penis growth
Rapid growth of laryngeal structures in boys
Causes voice to change and become lower in pitch

72. Puberty timing Precocious puberty Girls 2 years prior to boys
African American girls about 1 year earlier than Caucasians
Onset has dropped with better nutrition and health care
About 8–12 for girls and 9–14 boys
Precocious puberty
Signs of puberty developing much earlier than normal
May be without known cause
May be due to brain injury, pituitary or gonad tumor

73. Male Climacteric Male climacteric
Men with decreased testosterone levels in 50s
Due to decreased number of interstitial cells
Decline more gradually than women’s hormone drop
Most men with few symptoms
Some with mood swings, decreased sex drive, hot flashes
Prostate enlargement
Experienced by most men with age
Interferes with sexual and urinary functions
Erectile dysfunction and impotence
Inability to achieve or maintain erection
Associated with aging, other risk factors