NATS 1675 Lecture Notes - Seminiferous Tubule, Male Reproductive System, Glans Penis

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Lecture 21 Male Reproductive System (Structures, Functions, Spermatogenesis)
- Three main functions for male reproductive organs:
o Produce and maintain male sex cells (sperm)
o Transport sperm to the outside (to the female’s body)
o Secrete male sex hormones
- Components of the male reproductive system
o Testes (primary sex organs)
Called gonads
Form sperm and testosterone
o Penis
o System of ducts
Transportation of sperm and associated fluids
o Accessory glands
Protect and nourish sperm
Provide transport medium to help deliver sperm to outside of male’s body
- Main reproductive organs
o Testes
Primary sex organ
Called gonads (in females, ovaries are gonads)
Form sperm and testosterone
o Epididymis
Store sperm
Where sperm mature
o Bulbourethral gland
Gland that secretes alkaline mucous-like fluid before ejaculation
Neutralize the urethra from previous acidic urine
o Seminal vesicle
Nourish and thicken sperm
Aid the movement of sperm
o Prostate gland
Activate sperm
Produce secretions that decrease the acidity of the male and female
reproductive environments
o Vas deferens
Duct that takes sperm from epididymis to urethra
o Urethra
Urinary and ejaculatory tube
o Erectile tissue
Spongy tissue
Fills with blood during arousal
o Penis
Tool for intercourse
o Glans penis
Sensitive portion at tip of penis
Sexual arousal
o Scrotum
Sac for testes
Made of muscle, skin and fibrous tissue
Outside internal body
Must be kept at 35oC so testes can produce sperm (carry out spermatogenesis)
- Testes are the main organ in the male reproductive system
o Major components of testes
Tunica albuginea
White fibrous capsule on testes
Connective tissue
Divides testes into sections called lobules
Seminiferous tubules
Make up lobules
1-3 tubules in each lobule
Sperm produced in seminiferous tubules
Accessory cells
Interstitial cells
o Also called Leydig cells
o Connective tissue between seminiferous tubules
o Produce testosterone
Sustentacular cells
o Also called Sertoli cells
o Lie among forming sperm
o Protect sperm
o Give nutrients to sperm, take away sperm waste
o Act like nurses to aid sperm development
- Spermatogenesis occurs in testes
o Males have spermatogenic cells
o At puberty, spermatogenic cells stimulated to start making sperm
o Spermatogenic cells divide into spermatogonia
Spermatogonia are in the walls of the seminiferous tubules
o Spermatogonia divide, forming primary spermatocytes
Primary spermatocytes continually form
Push old primary spermatocytes to lumen (cavity in middle of tubule)
o Primary spermatocytes become secondary spermatocytes
o Secondary spermatocytes become spermatids
o Finally, spermatids enter the lumen and are called spermatozoans
- Mature sperm has three regions
o Head
Sac over the head
Contains enzymes to dissolve egg shell
Helps the sperm penetrate the egg
Contains male’s DNA
o Midpiece
Contains mitochondrion
Create energy in the form of ATP so sperm can navigate in the female’s
environment and find and penetrate the egg
o Tail
Whip-like movements to propel sperm through female’s environment
- Ducts in the male reproductive system
o Efferent ductules
12 ducts
Have cilia
Transport sperm from testes and take to epididymis
o Epididymis duct
Site of sperm maturation; they mature as they travel through it
Sperm stay here for 40-60 days and are fertile
6 metre-long duct on posterior (back) of testes
If not ejaculated, sperm disintegrate; get reabsorbed by epididymis
o Vas deferens
45cm long
Takes sperm from testes to urethra
Unites with duct of seminal vesicle
o Ejaculatory duct
2cm long
Vas deferens + seminal vesicle
Passes through prostate
Leads to urethra
Ejaculation through urethra
o Urethra
Where the urine comes out (from bladder)
Where the sperm come out (from the epididymis)
Same tube for urination and ejaculation