Male Reproductive System

Front 1

Male Gross Anatomy

Back 1

*Scrotum
*Penis
- Urethra
- Corpus cavernosa
- Corpus spongiosum
- Glans penis
- Prepuce (foreskin)
*Testes
*Epididymis- sperm passes thru here to become activated
*Vas deferens (the sperm duct)

Front 2

Semen

Back 2

-approx 3.5 mL ejaculated during sexual climax. Consists of about 200 million sperm cells suspended in the secretions of accessory glands

Front 3

Seminal vesicles (paired)

Back 3

- secrete a nutritive fluid rich in fructose and prostaglandins. Provide energy for sperm after ejaculation.

Front 4

The prostate gland

Back 4

-secretes an alkaine fluid that may be important in neutralizing the acidic environment of the vagina and in increasing sperm cell motility.
- common site of cancer in men over age 50
- prostate cancer is thought to be hormone-related.

Front 5

Bulbourethral glands (aka Cowper's glands)

Back 5

- release a mucous secretion
- lubricates the penis and facilitates penetration into the vagina

Front 6

Engorgement of the penis during sexual excitement is due to activation of the reflex pathways for erection. Nitric oxide is an important vasodilator in this reflex

Back 6

Descending CNS pathways triggered by thoughts, emotions and sensory inputs such as sight and smell + input from penis mechanoreceptors -->
Neurons to penis: increased activity of neurons that release nitric oxide. Decreased activity of sympathetic neurons -->
Penis: dilation of arteries --> erection --> compression of veins

Front 7

In response to FSH and testosterone, the _______ cells support spermatogenesis

Back 7

Sertoli cells

Front 8

In response to LH, the _____ cells produce steroids, including testosterone

Back 8

Leydig cells

Front 9

Movemetn of spermatozoa

Back 9

seminiferous tubules --> rete testis --> epididymis --> efferent ductules --> vas deferens

Front 10

Sperm count and fertility

Back 10

- in 1970 the avg sperm count was 100 million per mL of semen
- today the avg is 60 million per ml semen.
- Causes? environmental factors, alcohol, marijuana, cigarettes, industrial toxins. Use of anabolic steroids can also cause sterility.
- Men with less than 20 million per ml or less are sterile

Front 11

Spermatogenesis is the testicular process in adult males that generates haploid gametes capable of fertilizing ova.
The overall result is that the set of 23 pairs of homologous chromosomes is reduced to a set of 23 chromosomes per sperm- the corresponding 23 pairs are present in ova.

Back 11

spermatogenesis --> (mitosis and differentiation) --> primary spermatocytes --> (1st meiotic division)--> secondary spermatocytes --> (2nd meiotic division) --> spermatids--> (differentiation) --> spermatozoa

Front 12

After its release in the female reproductive tract, a spermatozoan is propelled by the thrashing movements of its flagellum

Back 12

At the time of fertilization, the acrosome at the head of an individual spermatozoan releases enzymes that allow it to gain access to the interior of the ova and accomplish the union of genetic material.

Front 13

Leydig (interstitial) cells

Back 13

- produce testosterone
- are stimulated to produce testosterone by LH from the anterior pituitary
- in the male LH is also known as Interstitial Cell Stimulating Hormone or ICSH
(LH and ICSH are same hormone, just diff names in male and female)

Front 14

Testosterone

Back 14

- stimulates spermatogenesis
- affects muscle and bone
- growth spurt in adolescent males
- responsible for growth of reproductive organs (primary sex characteristics)
- responsible for secondary sex characteristics (facial and body hair, muscle development, deepening of voice)

Front 15

The Sertoli Cells

Back 15

- provide a barrier to chemicals (blood-testis barrier). Similar to blood-brain barrier
- nourish developing sperm
- secrete luminal fluid, including androgen-binding protein
- receive stimulation by testosterone and FSH to secrete paracrine agents that stimulate sperm proliferation and differentiation
- Secrete the protein inhibin, which inhibits FSH secretion
- secrete paracrine agents that influence the function of Leydig cells
- secrete, during embryonic life, Muellarian inhibiting substance which causes the primordial female duct system to regress

Front 16

Hormonal Control of Sperm Production

Back 16

- Gonadotropin-releasing hormone (GnRH) from neurosecretory cells of the hypothalamus causes stimulation of pituitary
- Lutenizing hormone (aka ICSH) stimulates Leydig cells to produce testosterone
- FSH from the pituitary (stimulated by GnRH) will promote production of sperm (spermatogenesis)

Front 17

Summary of hormonal control of male reproductive system

Back 17

hypothalamus secretes GnRH --> Anterior pituitary secretes FSH and LH --> FSH: stimulates sertoli cells to start spermatogenesis and also secrete inhibin (negative feedback to FSH). LH: stimulates Leydig cells to produce testosterone, and reproductive tract and other organs respond to testosterone.