1. Human Biology: Reproductive System
Lesson 2:Functional Inter-relationships of the Male Reproductive Sytem
(Inquiry into Life pg )

2. Today’s Objectives
Analyse the functional inter-relationships of the structures of the male reproductive system, including:
Describe the path of sperm from the seminiferous tubules to the urethral opening
List the components of seminal fluid (as contributed by the Cowper’s glands, prostate gland, and seminal vesicles), and describe the functions of each component
Identify the tail (flagellum), midpiece, head, and acrosome of a mature sperm and state their functions
Describe the functions of testosterone
Describe the homeostatic regulation of testosterone levels by the hypothalamus, anterior pituitary, and testes

3. Spermatogenesis (Sperm Development)
Sperm cells are derived from undifferentiated cells called spermatogonia (sing. Spermatogonium)
Lie just on the outside wall of a tubule
Divide mitotically (dividing into copies)
Constantly producing new spermatogonia

4. Spermatogenesis
Some of the newly formed spermatogonia move away from the walls to increase in size and become primary spermatocytes
These then undergo meiosis, a type of cell division
Primary spermatocytes, with 46 chromosomes, divide to give 2 secondary spermatocytes, each with 23 chromosomes

5. Secondary spermatocytes divide to produce 4 spermatids, also with 23 chromosomes.
(see video)

6. Spermatids then differentiate into sperm (spermatozoa).
Also present in the tubules are the sertoli, which support, nourish and regulate the spermatogenic cells.

7. Parts of Sperm Head: 23 chromosomes
Acrosome: attached type of lysosome
Contains hydrolytic enzymes
Digests in outer layer of egg so sperm can penetrate
Middle piece: contains mitochondria for energy
Tail: flagellum used for locomotion

9. Path of Sperm 1) Formed in the seminiferous tubules of the testes
2) Mature and stored in the epididymus
3) Stored in and conducted through the Vas Deferens
4) Enters the urethra just prior to ejaculation
5) Accessory glands (prostate, Cowper’s glands, and seminal vesicles add secretions to semen
6) Semen and sperm exit through the penis

10. Seminal Fluid
SOURCES: 1. Seminal Vesicle
2. Prostate Gland
3. Cowper’s Gland

11. Functions of Seminal Fluid
1) Seminal fluid produces slightly basic pH
7.5 preferred pH of sperm (basic) to counteract the acidity level of the vagina
2) Provides fructose for energy for sperm
3) Contains prostaglandins – chemicals which cause the uterus to contract
4) Aids in the movement of the sperm to the egg
5) Lubrication

12. Functions of Testosterone
1) Essential for development of primary sex organs
2) Essential for the development of sperm
Spermatogenic cells take up testosterone which stimulate their activity
3) Increased testosterone concentration at puberty causes maturation of penis and testes

13. Functions of Testosterone
4) Secondary sex characteristics
Facial hair
Body hair – armpit, chest, legs, etc
Pubic hair
Oil and sweat glands secrete (smelly!)
Larynx expands (voice changes)
Increased muscular strength
Aggression
Sex drive

14. Hormonal Control of Testosterone
Hypothalamus releases GnRH
(Gonadotropic releasing hormone)
GnRH causes anterior pituitary to release 2
gonadotropic hormones:

15. Hormonal Control of Testosterone
FSH (Folicle stimulating hormone)
Promotes spermatogenesis in the seminiferous tubules
LH (Leutenizing hormone)
Promotes production of testosterone in interstitial cells
Produced in the Anterior Pituitary gland

16. Negative Feedback
Increased testosterone concentration in the blood causes the anterior pituitary to make less LH, therefore less testosterone is produced.
Decreased testosterone concentration in the blood causes the anterior pituitary to make more LH and therefore more testosterone is produced.

17. Negative Feedback
Increased concentration of stored sperm causes an increase in production of inhibin and decreases production of FSH, therefore production of sperm decreases.
Decreased concentration of stored sperm causes a decrease in production of inhibin and more FSH, therefore more sperm is produced.