1. Anatomy and Physiology
Biology 2401
Chapter-28
The Reproductive System

2. Introduction
Male and female reproductive systems are made of: Gonads – produce gametes and hormones Ducts – transport gametes and/or developing embryo Accessory structures – secrete fluid, support embryo/newborn

3. Male Reproductive System
Made of: Gonads - Testes – produce sperms and hormones Ducts – Epididymis , Vas deferens, Ejaculatory duct & Urethra – ducts that transports semen (sperms + seminal fluid)
Accessory Structures - Seminal vesicle, prostate, and bulbourethral glands – produce seminal fluid to support the sperms

4. Male Reproductive System
Scrotum:
Pouch formed by the abdominal wall divided into two sacs by a septum
Skin with dartos muscle  contraction during sexual arousal  causes tightening and wrinkling of the skin
Closer to birth  testes descend into the scrotum through the inguinal canal  inguinal canal then closes  testes are suspended in the scrotal sac by a spermatic cord and cremaster muscles Cryptorchidism: Testes fail to descend into the scrotum  testes remain in the abdomen  temperature same as the body temperature  no sperms are formed and greater risk of testicular cancer

5. Male Reproductive System
Temperature regulation of testes:
Sperm formation requires a temperature 2-3° lower than the body temperature
Testicular temperature drops  cremaster muscles contract  testes are pulled closer to the abdomen  testes temperature rises
Testicular temperature rises  cremaster muscles relax  testes are pulled away from the abdomen  testes temperature drops

6. Male Reproductive System
Testes:
Tunica vaginalis – parietal and visceral layer.
Tunica albuginea - a dense connective tissue capsule surrounding the testes
Seminiferous tubules – long, coiled tubes packed inside the testes where spermatogenesis (sperm formation) takes place

7. Male Reproductive System

8. Male Reproductive System
Seminiferous tubules has
Developing germ cells - begin their development near the periphery of the tubules - get released as spermatozoa in the lumen of the tubule
Sertoli or sustentacular or nurse cells that - support developing germ cells- nourish, protect - phagocytize germ cell debris - secrete hormone (inhibin) to regulate FSH release - secrete androgen binding protein (ABP) that concentrates testosterone
Between seminiferous tubules are Leydig or interstitial cells - endocrine cells  secrete hormones  help regulate spermatogenesis

9. Male Reproductive System
44XY
44XY
44XY
22X
22Y
Spermatogenesis: sperm formation Diploid spermatogonia in the periphery of seminiferous tubules  divide by mitosis to form diploid primary spermatocytes  divide by meiosis to form 4 haploid spermatids
Spermiogenesis: Spermatids transform  spermatozoa/sperm
Spermiation: Release of spermatozoa in the lumen of seminiferous tubules
22X
22X
22Y
22Y
22X
22X
22Y
22Y

10. Male Reproductive System
Sperms
Consist of: Head – has the haploid nucleus (with 22X or 22Y chromosomes) – has a membrane sac containing hydrolytic enzymes that aid fertilization Midpiece – contains mitochondria that provide ATP for motility of the sperm Tail – is the flagellum that provides movement to the sperm

11. Male Reproductive System
Sperms
About 300 million sperms are produced per day.
Sperms are made in seminiferous tubules in the testes  released and mature in epididymis  as they are released, they are mixed with seminal fluid, secretions from 3 exocrine glands: Seminal vesicle Prostate gland Bulbourethral / Cowper’s gland
Semen: sperms + seminal fluid : 2.5 – 5.0 ml per ejaculate : Slightly alkaline – pH 7.2 – 7.7 : About 50 – 150 million sperms/ml : Less than 20 million sperms/ml may be a cause for infertility

12. Epididymis
Sperms are made in the seminiferous tubule --> travel through the rete tesis --> efferent ductules in the testes --> reach the epididymis.
Epididymis is a coiled tube on the posterior side of testes.  
Three Functions of the Epididymis
Monitors and adjusts fluid produced by seminiferous tubules
Recycles damaged spermatozoa
Stores and protects spermatozoa
Facilitates functional maturation
Sperms remain in epididymis for days, mature (gain motility, ability to fertilize - in a process called capacitation) if not ejaculated: sperms break down and get reabsorbed by the body
if ejaculated: sperms move towards the next part of the male reproductive structure.

13. Male Reproductive System
 if ejaculated: sperms move with the help of peristalsis  to vas deferens that goes through the spermatic cord and enters the abdomen  to the ampula of the vas deferens  mix with the secretion of seminal vesicle  enter ejaculatory duct that passes through the prostate gland  released into the prostatic urethra  mix with the secretion of prostate gland  pass through the membranous urethra  enter spongy urethra  mix with the secretion of Cowper’s gland  pass through the spongy urethra of the penis  ejaculated at the urethral orifice

14. The Accessory Glands
Produce semen, which is a mixture of secretions from many glands
Each with distinctive biochemical characteristics
Important glands include:
Seminal glands
Prostate gland
Bulbo-urethral glands

15. 28-2 Male Reproductive Functions
Four Major Functions of Male Glands
Activating spermatozoa - capacitation
Providing nutrients spermatozoa need for motility
Propelling spermatozoa and fluids along reproductive tract
Mainly by peristaltic contractions
Producing buffers
To counteract acidity of urethral and vaginal environments

16. Male Reproductive System
Penis
Common passage for urine and semen
Has corpus spongiosum – a mid-ventral, sinus rich tissue surrounding the spongy urethra: Expands at the tip of the penis to form glans penis (which is surrounded by prepuce- the foreskin) Forms the bulb to anchor the penis to the abdomen
Has corpora cavernosa - two dorso-lateral, sinus-rich masses of tissues

17. Male Reproductive System
Erection: Sexual arousal  nerve impulses to blood sinuses in erectile tissue (corpora cavernosa and corpus spongiosum)  dilatation  blood fills in the sinuses  penis expands
Ejaculation: Peristalsis in vas deferens and urethra  sperms ejected : Closing of smooth muscle sphincter at the base of urinary bladder  preventing the release of urine

18. Male Reproductive System – Hormonal Control

19. Male Reproductive System – Hormonal Control
Hypothalamus secretes gonadotropin releasing hormone (GnRH)  stimulates anterior pituitary to secrete: A. Follicle stimulating hormone (FSH) that stimulates Sertoli/sustentacular cells to make - Androgen binding protein (ABP), for concentrating testosterone for germ cells - Inhibin, a hormone that inhibits hypothalamus and anterior pituitary to inhibit LH and FSH secretion - Activin, a hormone that activates hypothalamus and anterior pituitary to activate LH and FSH secretion B. Luteinizing hormone (LH) stimulates Leydig cells  secrete testosterone (T)  stimulates spermatogenesis, development of secondary male characteristics, metabolism and bone and muscle growth

20. Male Reproductive System - Disorder
Circumcision: Surgical removal of prepuce
Erectile dysfunction: Inability to maintain erection : Due to - Reduced testosterone level (hypothalamus, pituitary or testes disorder) - Nerve disorder (unable to stimulate blood sinuses in erectile tissue) - Blood vessel disorder (nerve impulses  stimulate endothelial cells  release of nitric oxide – *Viagra increases NO levels  relaxation of smooth muscle in the wall of blood sinuses  vasodilation  erection)
Prostate enlargement and cancer: Enlargement  causes constriction of urethra  difficulty in urination : Cancer  PSA levels increase in blood
Inguinal hernia: Due to sudden stress (lifting weight)  a portion of small intestine gets pushed into the inguinal canal  swelling, severe pain and affect on digestive and reproductive functions

21. Male Reproductive System – Aging
After 50 years of age
Gradual decrease in the size of the testes and number of Leydig cells  gradual decrease in T levels  decreased sperm production and muscles
Increased chances of prostate enlargement and cancer
Increased fibrous connective tissue development in the erectile tissue of penis  decreased capacity to develop and maintain for erection