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The MALE Reproductive System

Dr. P. A. Hernandez, Belen Jesuit Prep School
by

Dr. Pedro A. Hernandez

on 25 April 2013

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Transcript of The MALE Reproductive System

PowerPoint® Lecture Slides

Prepared by Dr. Pedro A. Hernandez,
Belen Jesuit Preparatory School
Miami, Florida C H A P T E R 16 The Reproductive System The Reproductive System Gonads—primary sex organs
Testes in males
Ovaries in females

Gonads produce gametes (sex cells) and secrete hormones
Sperm—male gametes
Ova (eggs)—female gametes Testes
Duct system
Epididymis
Ductus (vas) deferens
Urethra Accessory organs
Seminal vesicles
Prostate
Bulbourethral glands
External genitalia
Penis
Scrotum (a) Rectum Testis Ureter Pubis Figure 16.2b Urinary
bladder Prostate Prostatic
urethra Orifices of
prostatic ducts Membranous
urethra Root of
penis Shaft (body)
of penis (b) Ureter Ampulla
of ductus
deferens Seminal
vesicle Ejaculatory
duct Bulbourethral
gland Ductus
deferens Erectile
tissue
of penis Epididymis Testis Spongy
urethra Glans penis Prepuce External
urethral
orifice Testes Coverings of the testes
Tunica albuginea—capsule that surrounds each testis
Septa—extensions of the capsule that extend into the testis and divide it into lobules Each lobule contains one to four seminiferous tubules
Tightly coiled structures
Function as sperm-forming factories
Empty sperm into the rete testis (first part of the duct system)
Sperm travels through the rete testis to the epididymis
Interstitial cells in the seminiferous tubules produce androgens such as testosterone Figure 16.1 Rete testis Ductus (vas)
deferens Epididymis Blood vessels
and nerves Septum Spermatic cord Seminiferous
tubule Tunica
albuginea Lobule Duct System Epididymis
Ductus (vas) deferens
Urethra Epididymis Comma-shaped, tightly coiled tube
Found on the superior part of the testis and along the posterior lateral side
Functions to mature and store sperm cells (at least 20 days)
Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens Ductus Deferens (Vas Deferens) Terminates in the ejaculatory duct which unites with the urethra
Expanded end of the ductus deferens is called the ampulla
Ejaculation—smooth muscle in the walls of the ductus deferens create peristaltic waves to squeeze sperm forward
Vasectomy—cutting of the ductus deferens at the level of the testes to prevent transportation of sperm (form of birth control) Urethra Extends from the base of the urinary bladder to the tip of the penis
Carries both urine and sperm
Sperm enters from the ejaculatory duct Regions of the urethra
Prostatic urethra—surrounded by prostate
Membranous urethra—travels from prostatic urethra to penis
Spongy (penile) urethra—runs the length of the penis Seminal Vesicles Located at the base of the bladder
Produces a thick, yellowish secretion (60 percent of semen)
Fructose (sugar)
Vitamin C
Prostaglandins
Other substances that nourish and activate sperm Accessory Organs Seminal vesicles
Prostate
Bulbourethral glands Prostate Encircles the upper part of the urethra
Secretes a milky fluid
Helps to activate sperm
Enters the urethra through several small ducts
Prostatitis–inflammation of the prostate
Prostate cancer–third most common cancer in males Bulbourethral Glands Pea-sized gland inferior to the prostate
Produces a thick, clear mucus
Cleanses the urethra of acidic urine prior to ejaculation
Serves as a lubricant during sexual intercourse
Secreted into the penile urethra Semen Mixture of sperm and accessory gland secretions
Advantages of accessory gland secretions
Fructose provides energy for sperm cells
Alkalinity of semen helps neutralize the acidic environment of vagina
Semen inhibits bacterial multiplication
Elements of semen enhance sperm motility External Genitalia Scrotum
Divided sac of skin outside the abdomen
Maintains testes at 3°C lower than normal body temperature to protect sperm viability Penis
Delivers sperm into the female reproductive tract
Regions of the penis
Shaft
Glans penis (enlarged tip)
Prepuce (foreskin)
Folded cuff of skin around proximal end
Often removed by circumcision External Genitalia Internally there are three areas of spongy erectile tissue around the urethra
Erections occur when this erectile tissue fills with blood during sexual excitement Spermatogenesis Spermatogonia (stem cells) undergo rapid mitosis to produce more stem cells before puberty
Follicle-stimulating hormone (FSH) modifies spermatogonia division
One cell produced is a stem cell, called a type A daughter cell
The other cell produced becomes a primary spermatocyte, called a type B daughter cell Primary spermatocytes undergo meiosis
One primary spermatocyte produces four haploid spermatids
Spermatids—23 chromosomes (half as much material as other body cells) Human Life Cycle Union of a sperm (23 chromosomes) with an egg (23 chromosomes) creates a zygote (2n or 46 chromosomes) Spermiogenesis Late spermatids are produced with distinct regions
Head
Midpiece
Tail
Sperm cells result after maturing of spermatids
Spermatogenesis (entire process, including spermiogenesis) takes 64 to 72 days Anatomy of a Mature Sperm Cell The only human flagellated cell
Head
Contains DNA
Acrosome—“helmet” on the nucleus, similar to a large lysosome
Breaks down and releases enzymes to help the sperm penetrate an egg
Midpiece
Wrapped by mitochondria for ATP generation Testosterone Production The most important hormone of the testes
Produced in interstitial cells
During puberty, luteinizing hormone (LH) activate the interstitial cells
In turn, testosterone is produced Testosterone Production Functions of testosterone
Stimulates reproductive organ development
Underlies sex drive
Causes secondary sex characteristics
Deepening of voice
Increased hair growth
Enlargement of skeletal muscles
Thickening of bones
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