Male Reproductive System

Gonads -

organs where gametes are produced

The scrotum: Supporting

structure for testes

scrotum: Sac

of skin and superficial fascia

scrotum: Its external positioning

keeps the testes lower than core body temperature

The Scrotal Septum

divides the scrotum into two sacs interiorly, each contains one testis

Dartos muscle:

is found in subcutaneous tissue and in septum, bundles of smooth m. fibers, contraction gives skin wrinkled appearance

Cremaster muscle is

a band of skeletal muscle that is a continuation of internal oblique muscle

Contraction of Dartos muscle and cremaster

muscles brings testes closer to body for warmth

Descent of testes: Develop

near kidney on posterior abdominal wall

Descent of testes: Descends

into scrotum by passing through inguinal canal

Descends into scrotum by passing through inguinal canal TAKES PLACE…

during 7th month of fetal development

Testes: tunica vaginalis,

derived from peritoneum

Testes: tunica albuginea,

the fibrous capsule of the testis

Septa

(extensions of tunica albuginea) divide the testis into 250-300 lobules, each containing 1-4 seminiferous tubules

Spermatogenesis:

The sequence of events that produces sperm in the seminiferous tubules of the testes

Spermatogenesis starts with

diploid spermatogonia which are stem cells for sperm.

Spermatogenesis begins at

puberty in males

spermatogenesis: Mitosis of the spermatogonia to

maintain a stem cell line for life

spermatogenesis: each mitotic division of spermatogonia results in

type A or type B daughter cells

Spermatogenesis: Type A cells

remain and maintain the germ line

Spermatogenesis: Type B cells

move toward the lumen and differentiate into primary spermatocytes that will undergo meiosis

Primary spermatocytes

undergo meiosis I, forming two haploid cells called secondary spermatocytes

Secondary spermatocytes

undergo meiosis II and their daughter (4) cells are called spermatids

Spermatids

are small round cells seen close to the lumen of the tubule

Late in spermatogenesis,

spermatids are haploid but nonmotile

Spermiogenesis –

spermatids lose excess cytoplasm and form a tail, becoming sperm

Sertoli Cells

Support and protect the developing spermatogenic cells in several ways

Sertoli Cells: Nourish

developing sperm

Sertoli Cells: Phagocytize

excess cytoplasm

Sertoli Cells: Control

movements of spermatogenic cells and release sperm into lumen

Sertoli Cells: Joined by

tight junctions to form the Blood-Testis Barrier

Sertoli Cells: Joined by tight junctions to form the Blood-Testis Barrier

Isolates the developing gametes from the blood preventing an immune response against the spermatogenic cell’s surface antigens which are recognized as foreign by immune system

Sertoli Cells: Produce

fluid for sperm transport, secrete hormone inhibin

Leydig (Interstitial) Cells

Clusters of cells in between adjacent seminiferous tubules

Leydig Cells: Secrete

testosterone

Sperm Major Regions: Head

contains DNA and has a helmetlike acrosome containing hydrolytic enzymes that allow the sperm to penetrate and enter the egg

Sperm major regions: Midpiece

contains mitochondria spiraled around the tail filaments

Sperm major regions: tail

a typical flagellum produced by a centriole

Each day _______ complete spermatogenesis

300 million sperm

Hormonal control of the Testes

GnRH stimulates anterior pituitary secretion of FSH and LH.

Hormonal control of testes: FSH

initiates spermatogenesis

Hormonal Control of testes: LH

assists spermatogenesis and stimulates production of testosterone.

Effect inhibin: sertoli cells release 

inhibin

Sperm production is sufficient: inhibits FSH

secretion by the anterior pituitary

Sperm production is sufficient: decreases

sperm production

Sperm production is proceeding too slowly: less inhibin

is released by the sertoli cells

Sperm production is proceeding too slowly: more

FSH will be secreted

Sperm production is proceeding too slowly: sperm production

will be increased

Testosterone

controls the growth, development, functioning, and maintenance of sex organs

testosterone: stimulates

bone growth, protein anabolism, and sperm maturation

testosterone: stimulates development

of male secondary sex characteristics.

testosterone stimulates final

steps spermatogenesis

testosterone: Negative feedback

systems regulate testosterone production.

Seminiferous tubules

converge to form the tubulus rectus conveys sperm to rete testis to efferent ductules to epididymis

Spermatic cord –

encloses PNS and SNS nerve fibers, blood vessels, and lymphatics that supply the testes

Pathway of sperm flow

1. Seminiferous tubules

2. Straight tubules

3. Rete testis

4. Efferent ducts

5. Ductus epididymis

6. Ductus (vas) deferens

Epididymis

1.5in long along posterior border of each testis

epididymis: has

Head, body and tail region

epididymis: multiple

efferent ducts become a single ductus epididymis in the head region (20 feet if uncoiled)

edpi

epididymis: site of

sperm maturation

• Sperm may remain in storage here for at least a month, after which they are either expelled or degenerated and reabsorbed

The ductus epididymis is lined by

stereocilia that increase surface area for absorption

Ductus Deferens

18 inches-Runs from the epididymis through the inguinal canal into the pelvic cavity

ductus deferens: Propels

sperm from the epididymis to the urethra

ductus deferens: lined by

mucosal membrane of pseudostratified columnar epithelium and lamina propria, 3 layers of smooth muscle in muscularis

ductus deferens: conveys

sperm during sexual arousal from epididymis to urethra by peristalsis

ductus deferens: Can store

sperm for several months or reabsorb

ejaculatory ducts

are formed by the union of the ducts from the seminal vesicles and ducti deferens; their function is to eject spermatozoa into the prostatic urethra.

The male urethra

is the shared duct of the reproductive and urinary systems which serves as a passageway for semen and urine.

urethra (8 inch long passageway)

• Prostatic urethra

• Membranous urethra

• Penile (spongy) urethra

3 Accessory Glands: Seminal Vesicles: Lie on

the posterior wall of the bladder and secrete 60% of the volume of semen

Semen –

viscous alkaline fluid containing fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins

3 Accessory Glands: Seminal Vesicles: Join

the ductus deferens to form the ejaculatory duct

3 Accessory Glands: Seminal Vesicles: Sperm and seminal fluid

mix in the ejaculatory duct and enter the prostatic urethra during ejaculation

Alkaline, viscous fluid

• neutralizes vaginal acid & male urethra

• fructose

• prostaglandins

• coagulation proteins

Accessory Glands: Prostate Gland

Doughnut-shaped gland that encircles part of the urethra inferior to the bladder

Accessory Glands: Prostate Gland: milky

slightly acid fluid, which contains citrate, enzymes, and prostate-specific antigen (PSA), accounts for one-third of the semen volume

Accessory Glands: Prostate Gland: plays role in

activation of sperm

Accessory Glands: Prostate Gland: enters the

postatic urethra during ejaculation

Prostrate Gland: Single organ

• size of chestnut

• inferior to bladder

• pH 6.5 fluid

• citric acid

• enzymes for seminal liquefaction

Prostate gland: many

duct openings p

prostate gland: enlarges

with age

Accessory Glands: Bulbourethral Glands

Paired Pea-sized glands inferior to the prostate

Accessory Glands: Bulbourethral Glands: Produce thick,

clear mucus prior to ejaculation that neutralizes traces of acidic urine in the urethra

Accessory Glands: Bulbourethral Glands: mucus

for lubrication

Accessory Glands: Bulbourethral Glands: Ducts

open into spongy urethra

semen: provides

transport medium and nutrients (fructose), protects and activates sperm, and facilitates their movement

Prostaglandins in semen:

• Decrease the viscosity of mucus in the cervix

• Stimulate reverse peristalsis in the uterus

• Facilitate the movement of sperm through the female reproductive tract

semen: realtive

alkalinity of semen neutralizes the acid environment found in the male urethra and female vagina

Seminalplasmin –

antibiotic chemical that destroys certain bacterias

semen: clotting

factors coagulate semen immediately after ejaculation, then fibrinolysin liquefies the sticky mass

semen: only

2-5 ml of semen are ejaculated, but it contains 50-130 million sperm/ml

Penis

contains the urethra and is a passageway for the ejaculation of semen and excretion of urine

penis: body composed

of three erectile tissue masses filled with blood sinuses

Body composed of three erectile tissue masses filled with blood sinuses

• paired corpora cavernosa penis

• unpaired corpus spongiosum penis

corpora cavernosa

upper paired, erectile tissue masses

corpus spongiosum

lower erectile tissue mass, surrounds urethra, ends at glans penis

corpus sponginosum and corpora cavernosa surrounded by

tunica lbuginea

Erection –

during sexual excitement, the erectile tissue fills with blood causing the penis to enlarge and become rigid

Corpus spongiosum –

surrounds the urethra and expands to form the glans and bulb of the penis