1. Chapter 27 Male Reproductive System Lecture 18
Marieb’s Human
Anatomy and Physiology
Marieb w Hoehn
Chapter 27
Male Reproductive System
Lecture 18
Slides 1-15; 80 min (with review of syllabus and Web sites) [Lecture 1]
Slides 16 – 38; 50 min [Lecture 2]
118 min (38 slides plus review of course Web sites and syllabus)

2. Overview of the Reproductive System
We can sum up the reproductive system in just a few words…

3. Lecture Overview Function of the male reproductive system
Overview of the anatomy of the male reproductive system
Descent of the testes
Structure of the testes
Formation of sperm cells
Structure of sperm cells
Male internal accessory organs
Male external accessory organs
Erection, orgasm, and ejaculation
Hormonal control of the male reproductive system

4. Male Reproductive System
There are three main functions of the male reproductive system
Produce and maintain sex cells (sperm)
Transport sperm and supplemental fluids to the female reproductive tract
Secrete male sex hormones
Sex organs can be divided into
Primary sex organs (gonads) = testes (sperm, hormones)
Accessory (secondary) sex organs = internal and external reproductive organs
In order for sexual reproduction to take place, we need: 1) mobile cells, 2) cells that are nutrient laden. These two things are impractical to combine into one cell, so males have sperm (DNA with propellers!!), and females have large, nutrient-laden eggs as their sex cells (gametes).

5. Male Reproductive System
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Testis → Epididymis → Vas (ductus) deferens → Ejaculatory duct → Urethra

6. Male Reproductive Organs
posterior view
Figure from: Hole’s Human A&P, 12th edition, 2010

7. Descent of Testes
Figure from: Hole’s Human A&P, 12th edition, 2010
Descent begins 1-2 months before birth under the influence of testosterone
Descent is necessary for sperm production
Failure of testes to descend = cryptorchidism

8. Structure of the Testis
Figure from: Hole’s Human A&P, 12th edition, 2010
Surrounded by the tunica albuginea – a tough, white, fibrous capsule that encloses each testicle
Septa divide each testicle into about 250 lobules
Each lobule contains 1-4 highly coiled seminiferous tubules that give rise to sperm
Interstitial cells (of Leydig) lie in between seminiferous tubules and secrete male sex hormones
Rete Testis

9. Review of Mitosis and Meiosis
Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Major differences between mitosis and meiosis: 1) mitosis produces identical daughter cells, meiosis produces cells with recombined DNA; 2) daughter cells in mitosis have a diploid number of chromosomes whereas in meiosis gametes contain the haploid chromosome number; 3) two daughter cells are produced as a result of mitosis, whereas four cells are produced after meiosis.
Mitosis – production of two identical diploid daughter cells
Meiosis – production of four genetically varied, haploid gametes

10. Chromosome Crossing Over
Figure from: Hole’s Human A&P, 12th edition, 2010
mixes up traits
different colors represent the fact that one homologous chromosome comes from the individual’s father (paternal) and one from the mother (maternal)
Tetrad
the genetic information in sperm cells and egg cells varies from cell to cell

11. Seminiferous Tubules and Sperm Maturation
Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001
It takes about 75 days for a spermatogonium to become mature spermatazoon.
Spermatogonium = stem cell

12. Spermatogenesis Spermatogonium (2n) Primary spermatocyte (2n)
Know the order of events below!
Spermatogonium (2n)
Primary spermatocyte (2n)
Meiosis I
Secondary spermatocyte (n)
Meiosis II
Spermatid (n)
Spermiogenesis
Spermatozoan (n)

13. Formation of Sperm Cells
Figure from: Hole’s Human A&P, 12th edition, 2010
Supporting cells are sustentacular cells
They:
are important in regulating and supporting spermatogenesis
help maintain the blood-testis barrier

14. Structure of a Sperm Cell
Figure from: Hole’s Human A&P, 12th edition, 2010
Only flagellum in human body
Mitochondria
Young men produce about 300,000 sperm per MINUTE, or about 4 million sperm cells per day.
Enzymes used to penetrate the egg during fertilization

15. Male Internal Accessory Organs
Figure from: Hole’s Human A&P, 12th edition, 2010

16. Epididymis
Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001
Takes about 2 weeks for sperm to travel through the epididymis
- Maintains fluid produced in the seminiferous tubules - Recycles damaged sperm and cellular debris - Store and protects sperm, and aids in their maturation

17. Ductus (Vas) Deferens
muscular tube about 45 cm long; transports sperm ( can store sperm for several months)
extends from epididymis to ejaculatory duct
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

18. Seminal Vesicles attached to ductus deferens near base of bladder
secretes alkaline fluid (60% of the volume of semen)
secretes fructose, prostaglandins, and proseminogelin
begins capacitation of sperm
contents empty into ejaculatory duct
Newly made sperm contain a thick layer of cholesterol over their acrosomal cap. This prevents premature release of enzymes and damage to male reproductive system. (This cholesterol is later leached away by fluids in the female reproductive tract. This allows more Ca2+ to enter the sperm and causes more powerful lashing of the flagellum.) This process is capacitation.
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

19. Prostate Gland surrounds beginning of urethra
ducts of gland open into urethra
secretes a thin, milky, slightly acidic fluid (20-30% of semen volume)
secretion enhances fluid mobility
contains seminalplasmin
secretes Prostate-specific Antigen (PSA)
composed of tubular glands in connective tissue
also contains smooth muscle
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

20. Clinical Application - Prostate Enlargement
benign prostatic hyperplasia occurs in most men over 50
BPH causes frequent urination
risk factors include a fatty diet, having had a vasectomy(?), or exposure to certain environmental factors
treatments include
surgical removal
drugs
insertion of balloon into urethra
freezing of tumor
insertion of stent between lobes of prostate to relieve pressure on urethra

21. Bulbourethral (Cowper’s) Gland
inferior to the prostate gland
secretes thick, alkaline mucus - helps lubricate the tip of the penis (glans) and neutralize any urinary acids in urethra
fluid released in response to sexual stimulation
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

22. Semen
sperm cells
secretions of seminal vesicles, prostate gland, and bulbourethral glands (seminal fluid)
slightly alkaline (offsets acidity of ♀ reproductive tract)
prostaglandins (stimulates contraction in ♀ reproductive tract)
nutrients
enzymes (protease, seminalplasmin, fibrinolysin)
million sperm cells per milliliter
usually about 2-5 ml of fluid per ejaculate
Sperm count below about mil/ml is associated with infertility.

23. Male External Reproductive Organs
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

24. Scrotum pouch of skin and subcutaneous tissue
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001
pouch of skin and subcutaneous tissue
dartos muscle – smooth muscle in dermis; contracts to cause wrinkling of the scrotum (traps heat)
medial septum divides scrotum into two chambers
each chamber lined with a serous membrane
each chamber houses a testis and epididymis
Cremaster muscle can retract testes

25. Penis
Connection of penis to body wall (root)

26. Penis
Figure from: Hole’s Human A&P, 12th edition, 2010

27. Penis
Figure from: Hole’s Human A&P, 12th edition, 2010
Preputial glands in the prepuce (foreskin) produce a waxy material called smegma. This can be a source of bacterial growth if hygiene is poor.
Circumcision is the surgical removal of the prepuce.

28. Erection, Orgasm, and Ejaculation
parasympathetic nerve impulses
blood accumulates in erectile tissues
Orgasm
culmination of sexual stimulation
accompanied by emission and ejaculation
Emission and Ejaculation
emission is the movement of semen into urethra
ejaculation is the movement of semen out of the urethra
largely dependent on sympathetic nerve impulses

29. Mechanism of Penile Erection
Bulbospongiosus m.
Ischiocavernosus m.

30. How Does Viagra ™ (Sildenafil) Work?
Erotic stimuli
Nitric Oxide (NO)
Parasympathetic stimulation
(Required to start cascade)
GTP
Guanyl cyclase
Interior of smooth muscle cell
Smooth muscle relaxation, dilation of blood vessels
cGMP
Phosphodiesterase 5 (PDE5)
VIAGRA
(Also Cialis, Levitra)
GMP

31. Mechanism of Emission and Ejaculation
Figure from: Hole’s Human A&P, 12th edition, 2010

32. Hormonal Control of Male Reproductive Functions
Figure from: Hole’s Human A&P, 12th edition, 2010
hypothalamus controls maturation of sperm cells and development of male secondary sex characteristics
negative feedback controls concentration of testosterone

33. Actions of Testosterone
increased growth of body hair
sometimes decreased growth of scalp hair
enlargement of larynx and thickening of vocal cords
thickening of skin
increased muscular growth
thickening and strengthening of the bones
Know these actions

34. Review Spermatogenesis Spermatozoa
Spermatogonia, 1o spermatocyte, 2o spermatocyte, spermatid, spermatozoan
Is a result of meiotic division
Under the control of FSH
Is guided and regulated by sustentacular cells
Produces 4 haploid gametes (spermatozoa)
Spermatozoa
Head, midpiece, and tail
Acrosomal cap – enzymes use for fertilization
Non-motile when produced – must undergo capacitation

35. Review Male Accessory Organs Epididymis
Maintains fluid produced in the seminiferous tubules
Recycles damaged sperm and cellular debris
Store and protects sperm, and aids in their maturation
Vas (ductus) deferens – muscular tube for sperm transport and storage
Seminal vesicle
Alkaline fluid with fructose, prostaglandin, and fibrinogen
About 60% of semen volume in ejaculate

36. Review Male Accessory Organs (cont’d) Prostate gland
Thin, milky fluid
20-30% of semen volume in ejaculate
Seminalplasmin
Bulbourethral glands
Cowper’s glands
Thick, mucus-like substance
Lubricates glans of penis
Neutralizes acids in urethra

37. Review Semen External Reproductive Organs Sperm + seminal fluid
million sperm per ml in ejaculate (2-5 ml)
Contains enzymes
External Reproductive Organs
Scrotum
Contains and separates testes
Cremaster and dartos muscles regulate temperature of testes
Penis
Root, body (shaft), and glans; prepuce (foreskin)
Erectile tissues (c. cavernosum, c. spongiosum)
Urethra (common pathway for urine and sperm)
Prepuce

38. Review Erection, orgasm, emission, and ejaculation Erection
Filling of erectile tissues with blood; venous drainage is blocked
Controlled by parasympathetic NS (nitric oxide)
Orgasm - highly pleasurable culmination of the sexual experience, accompanied by emission and ejaculation
Emission - movement of semen into urethra
Ejaculation - movement of semen out of urethra
Orgasm, emission, and ejaculation are controlled by the sympathetic NS

39. Review Hormonal control of male reproductive system FSH LH (ICSH)
Meiosis in primary spermatocytes
Secretion of inhibin by sustentacular cells
LH (ICSH)
Secretion of androgens (testosterone) by interstitial cells
Levels of FSH and LH inhibit release of GnRH and FSH/LH
Effects of androgens