Chapter 28, part 2
The Reproductive System
Spermatogenesis
Seminiferous tubules
Contain spermatogonia
Stem cells involved in spermatogenesis
Contain sustentacular cells
Sustain and promote development of sperm
Figure 28.5 The Seminiferous Tubules
Figure 28.5 The Seminiferous Tubules
Figure 28.6 Chromosomes in Mitosis and Meiosis
Spermatogenesis
Spermatogenesis involves three processes
Mitosis
Meiosis
Spermiogenesis
Figure 28.7 Spermatogenesis
Anatomy of spermatozoon
Each spermatozoon has:
Head
Nucleus and densely packed chromosomes
Middle piece
Mitochondria that produce the ATP needed to move the tail
Tail
The only flagellum in the human body
Figure 28.8 Spermiogenesis and Spermatozoon Structure
Male reproductive tract
Testes produce mature spermatozoa
Sperm enter epididymus
Elongated tubule with head, body and tail regions
Monitors and adjusts fluid in seminiferous tubules
Stores and protects spermatozoa
Facilitates functional maturation of spermatozoa
Figure 28.9 The Epididymus
Ductus deferens AKA vas deferens
Begins at epididymus
Passes through inguinal canal
Enlarges to form ampulla
Ejaculatory duct at base of seminal vesicle and ampulla
Empties into urethra
Urethra
Urinary bladder to tip of penis
Three regions
Prostatic
Membranous
Penile
Accessory glands
Seminal vesicles
Active secretory gland
Contributes ~60% total volume of semen
Secretions contain fructose, prostaglandins, fibrinogen
Accessory glands
Prostate gland
Secretes slightly acidic prostate fluid
Bulbourethral glands
Secrete alkaline mucus with lubricating properties
Figure 28.10 The Ductus Deferens and Accessory Glands
Contents of Semen
Typical ejaculate = 2-5 ml fluid
Contains between 20 – 100 million spermatozoa per ml
Seminal fluid
A distinct ionic and nutritive glandular secretion
External genitalia
Male external genitalia consist of the scrotum and the penis
Skin overlying penis resembles scrotum
Penis
Contains three masses of erectile tissue
2 corpora cavernosa beneath fascia
1 corpus spongiosum surrounding urethra
Dilation of erectile tissue produces erection
Figure 28.11 The Penis
Hormones and male reproductive function
FSH (Follicle stimulating hormone)
Targets sustentacular cells to promote spermatogenesis
LH (leutinizing hormone)
Causes secretion of testosterone and other androgens
GnRH (Gonadotropin releasing hormone)
Testosterone
Most important androgen
Figure 28.12 Hormonal Feedback and the Regulation of the Male Reproductive Function
