THE MALE REPRODUCTIVE SYSTEM

THE MALE REPRODUCTIVE SYSTEM

HOMEOSTASIS

male & female reproductive organs work together to produce offspring

female reproductive organs also contribute to sustaining the growth of embryos and fetuses

Sexual Reproduction

process by which organisms produce offspring by making germ cells (gametes)

fertilization: when male gamete (sperm) unites with female gamete (secondary oocyte) fertilized egg

males & females have anatomically distinct reproductive organs that function to

1. produce gametes2. facilitate fertilization3. sustain growth of embryo & fetus (female)

Males Females

Gonads: testesDucts

store & transport gametes

Accessory Sex Glands Supporting

Structures Penis

Gonads: ovariesDucts

transport gametesAccessory Sex

GlandsSupporting

Structures: Uterus

Reproductive Organs

Male Reproductive System

Organs:1. Testes2. system of ducts3. accessory sex glands4. supporting structures:

scrotum penis

Functions of the Male Reproductive System

1. Testes produces sperm & the male sex hormone Testosterone (T)

2. Ducts transport, store, & assist in maturation of sperm

3. Accessory sex glands secrete most of liquid portion of semen

4. Penis contains the urethra, passageway for ejaculation of semen & excretion of urine

5. Scrotum protects temperature-sensitive testes from temperature fluctuations

Scrotum

a supporting structure for the testesfeatures:loose skin & superficial fascia attached from

root of penisexternally:

raphe: median ridge that separates scrotum into right & left sides

internally: scrotal septum: divides scrotum into 2 sacs,

each with 1 testes

Scrotum - 2

features continued:dartos muscle: smooth muscle fibers

contraction causes wrinkled appearance (reduces heat loss)

cremaster muscle: skeletal muscle2 features regulate temp of testes:1. location outside trunk keeps temp 2 – 3 °C lower

than core body temp2. in response to cold temps, both muscles

contract moving testes closer to body so can absorb body heat

Testes (plural)/ Testis (singular)

aka testiclespaired oval glands develop near kidneys

begin descent into scrotum thru inguinal canals during latter half 7th month gestational age

leading edge covered with peritoneum called tunica vaginalis Hydrocele: serous fluid collects between this

& testis (injury or inflammation of epididymis)

Hydrocele

Testes - 2

tunica albuginea: internal to tunica vaginalis dense irregular CT extends inward into testis forming septa:

divide testis into series of 200 – 300 lobules (internal compartments)

each lobule contains 1 – 3 coiled seminiferous tubules : *site of production of semen

spermatogenesis: process by which seminiferous tubules produce sperm

Testes

Seminiferous Tubules

2 types of cells:1. spermatogenic cells

sperm-forming cells: spermatogonia: stem cells primordial germ

cells arise in yolk sac & enter testes during 5th wk of

development: remain dormant until puberty 1° spermatocytes, 2° spermatocytes, spermatids,

sperm cells (layers of progressively more mature cells)

2. Sertoli cells function in supporting spermatogenesis

Spermatogenesis

Sertoli Cells

aka sustentacular cells extend from basement membrane lumen of

tubuleheld together by tight junctions

form obstruction known as the blood-testis barrier: all substances must pass thru Sertoli cells to reach developing sperm cells (after spermatogonia)

Sertoli Cell

Functions of the Sertoli Cells

1. nourish spermatocytes, spermatids, & sperm

2. phagocytoze excess spermatid cytoplasm as they develop into sperm

3. control movements of spermatogenic cells & release of sperm into lumen of seminiferous tubules

4. produce fluid for sperm transport5. secrete hormone inhibin6. mediate effects of T & FSH

Leydig Cells

interstitial cells (between seminiferous tubules)

*secrete T

Sperm

~300 million sperm complete spermatogenesis/d

~60 μm longonce ejaculated last ~48 hours w/in female

reproductive tract

Hormonal Control of the Testes

Ducts of the Male Reproductive System

fluid secreted by Sertoli cells generates pressure which pushes sperm & fluid along lumen of seminiferous tubule eventually released as ejaculate

Epididymis

epi = over or above / didymis = testisaka: ductus epididymisplural:epididymidescomma-shaped organlies along posterior border of each testis1. ductus epididymis2. head3. body4. tail

Ductus Epididymis

~6 m in lengthpseudostratified columnar epithelium lined with

microvilli called stereocilia increase surface area for reabsorbing

degenerated spermsurrounded by smooth muscleFunction of epididymis:

*sperm maturation (acquire motility & ability to fertilize an ovum)

smooth muscle contraction propels sperm into ductus deferens

sperm storage (viable up to several months)

Ductus Deferens/ Vas Deferens

ascends along posterior border of epididymis inguinal canal entering pelvic cavity loops over ureter passes down posterior surface of urinary bladder

terminal end is dilated = ampullapseudostratified columnar epithelium3 layers smooth muscle (inner & outer layers

longitudinal, middle layer circular)

Function of Vas Deferens

Function: 1. conveys sperm from epididymis urethra by

peristaltic contractions2. sperm storage (several months)

sperm not ejaculated are reabsorbed

Vasectomy

main method for sterilization of malesportion of each vas deferens is cut out & ends

ligatedsperm

production continues but do not reach exterior

degenerate & destroyed by phagocytes

Ejaculatory Ducts

formed by union of duct from seminal vesicle & ampulla of ductus deferens

pass inferiorly & anteriorly thru prostate gland

terminate in prostatic urethra where they eject sperm & seminal vesicle secretions just before the release of semen from urethra to exterior

Urethra

shared terminal duct of reproductive & urinary systems

passes thru: prostate deep muscles of perineum penis

Urethra

3 parts:1. Prostatic Urethra2. Membranous Urethra

portion thru deep perineal muscles3. Spongy (penile) Urethra

portion thru corpus spongiosum of penis ends at external urethral orifice

Parts of Male Urethra

Accessory Sex Glands

secrete most of liquid portion of semenInclude:1. Seminal Vesicles2. Prostate3. Bulbourethral Glands

Seminal Vesicles

aka seminal glandspaired, convoluted, pouchlike structuresposterior to base of urinary bladder (superior

surface) & anterior to rectum*secrete alkaline, viscous fluid: (~60% of vol

of semen) fructose prostaglandins clotting proteins (different from those in

blood)

Seminal Vesicles Fluid

alkaline to neutralize acidic environment of male urethra & female vagina (acids inactivate or kill sperm)

fructose:used for ATP production in spermprostaglandins contribute to sperm motility &

viabilityclotting proteins help semen clot after

ejaculation

Prostate

single, donut-shaped gland~size of a golf ballinferior to urinary bladdersurrounds prostatic urethraincreases in size from birth to puberty when

it expands rapidly until ~ age 30, remains stable ~ age 45, further enlargement may occur after that

Prostatic Fluid

milky, slightly acidic~25% of vol of semen empties urethra thru many prostatic ductscontains:1. citric acid (ATP production in sperm)2. several proteolytic enzymes

PSA: prostate-specific-antigen3. acid phosphatase (function unknown)4. seminalplasmin: bacteriocidal

Bulbourethral Glands

aka Cowper’s glandspea sized, inferior to prostate gland on either

side of membranous urethraducts open into spongy urethrasecrete 1. alkaline fluid (protects sperm from acidic

environment of spongy urethra)2. mucus lubricates end of penis & lining of

urethra (decreases # of sperm damaged during ejaculation)

Semen

mixture of sperm & seminal fluid

(secretions of seminiferous tubules, seminal vesicles, prostate, & Cowper’s glands)

average vol: 2.5 – 5 mL with 50 – 150 million sperm/mL

<20 million sperm per mL probably infertile pH: 7.2 – 7.7 provides sperm with:1. transportation medium2. nutrients3. protection from hostile acidic environment of

male urethra & female vagina

Penis

contains urethrapassageway for urine & semenParts:1. Body2. Glans Penis3. Root

Body of the Penis

Corpora Cavernosa: 2 dorsolateral

massesCorpus

Spongiosum: midventral mass spongy urethra

w/in

Circumcision

portion of prepuce (fore skin)surgical excised 3 – 4 days after delivery or 8th day for Jewish rite