Reproductive SystemMale - PowerPoint PPT Presentation
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Reproductive SystemMale
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Egg shaped structure found within the scrotum ... This muscle raises the testes and gives the scrotum the wrinkled appearance ... Scrotum and penis ... – PowerPoint PPT presentation
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Title: Reproductive SystemMale
1
Chapter 22
- Reproductive System-Male
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Basic reproductive structures
- Gametes-functional male and female reproductive
cells - Gonads-reproductive organs that produce gametes
and hormones - Ducts-receive and transport gametes
- Accessory organs and glands-secrete fluids into
ducts of reproductive system - External genitalia
3
Pathway sperm travels
- Spermatozoa are created in testis
- Travel to epididymis, then ductus (vas) deferens,
ejaculatory duct, and urethra - Accessory organs that assist spermatozoa on this
journey include seminal vesicles, prostate
gland, and bulbo-urethral (Cowpers) gland - External genitalia include scrotum (house the
testis) and penis (erectile organ)
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Male
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Testes
- Egg shaped structure found within the scrotum
- Cryptorchidism-one or both testes fail to descend
into the scrotum by the time the fetus is born - Usually occurs in a few weeks, if not can be
surgically corrected - Spermatozoa require about 2 degrees cooler
temperature for proper development
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Scrotum
- Divided internally into two chambers
- Partition in between is called the raphe
- The dermis contains a smooth muscle layer called
the dartos muscle - This muscle raises the testes and gives the
scrotum the wrinkled appearance - A skeletal muscle layer called the cremaster
muscle pulls the testes closer to the body during
cold or sexual arousal
7
Structure of Testes
- Fibrous partitions called septa subdivide the
testis into a series of lobules - Seminiferous tubules are distributed among the
lobules - Males typically average ½ mile of seminiferous
tubule (800 per testis) - Sperm production occurs within the ST
- Interstitial cells surround tubules and produce
androgens (testosterone for example)
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Spermatogenesis
- 3 processes
- 1. mitosis (spermatogonia undergo cell division
throughout adult life) - 1 daughter cell remains in place while the other
is pushed toward the lumen of the ST and this
primary spermatocyte will undergo meiosis - 2. Meiosis-special cell division which produces
the haploid number of chromosomes found in sperm
(23) - 3. spermiogenesis-maturation of spermatozoa
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Meiosis
- Occurs in 2 division cycles Meiosis I (reduction
division) and Meiosis II (equatorial division) - DNA replication occurs during interphase prior to
Meiosis I - Chromosomes pair up (synapsis) during later
prophase I - Pairs line up during Metaphase I
- Pairs separate during Anaphase I
- Two daughter cells form with half the number of
chromosomes in Telophase I (these are secondary
spermatocytes)
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Meiosis II
- Short resting period (interphase)
- Prophase II-chromosomes thicken
- Metaphase II-chromosomes line up at equatorial
plane - Anaphase II-sister chromatids separate
- Telophase II-produce 4 haploid spermatids (23
chromosomes in each) - All 4 spermatids become viable sperm
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spermiogenesis
- Spermatids mature into spermatozoa
- Nurse cells surround the spermatids until they
are more mature - At spermiation the spermatozoan loses its
attachment to the nurse cell and enters the
seminiferous tubule - The entire process (all 3 steps) takes 9 weeks
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Anatomy of a spermatozoan
- Head, mid-piece, tail
- Tip of head contains an acrosomal cap containing
enzymes necessary for fertilization - Mid-piece contains mitochondria for ATP
production - Tail-only flagellum in the human
- This makes the sperm motile
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sperm
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Reproductive Tract of Male
- Epididymis-immature sperm leave the lumen of the
seminiferous tubules after leaving nurse cells
and enter epididymis - This structure recycles damaged spermatozoa and
stores and protects undamaged spermatozoa while
they mature (takes 2 weeks)
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Sperm storage
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Reproductive Tract continued
- Ductus deferens-16-18 inch long tube that is part
of the spermatic cord - It begins at the tail of the epididymis and
ascends through inguinal canal, passes urinary
bladder. - Just before reaching prostate the lumen enlarges
into an ampulla - Smooth muscle in wall of ductus deferens allows
peristaltic contractions to move sperm - Can store sperm for several months (vasectomy
fool proof?)
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Continued
- Ejaculatory duct is a short passage that
penetrates wall of prostate and empties into the
urethra - Urethra-7-8 inches long
- Divided into prostatic, membranous, and spongy
regions - Shared by reproductive and urinary systems
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Accessory Glands
- Fluids contributed by seminiferous tubules and
epididymis account for only 5 of semen volume - Seminal vesicles -contribute 60 of semen volume
(slightly alkaline) - Contains high fructose, prostaglandins that
stimulate smooth muscle contractions, and
fibrinogen which clots temporarily after
ejaculation - Contractions during emission are under the
sympathetic nervous systems control
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Accessory continued
- Prostate gland-produces prostate fluid
- This fluid is slightly acidic and contributes
20-30 of semen volume - Contains antibiotic substance (seminalplasmin)
- Prostatitis-lower back pain, rectal or perineum
pain, mucous discharge, painful and frequent
urination
21
Accessory continued
- Bulbo-urethral glands (Cowper glands)
- Found at base of penis
- Thick, alkaline mucus that lubricates the glans
or tip of the penis
22
Semen
- Typical ejaculate contains 2-5 mL of semen
- Low volume may indicate prostate or seminal gland
problems - Normal sperm count is 20 million to 100 million
per milliliter of semen - Includes fluid from seminal glands (60).
Prostate (30), nurse cells and epididymis (5 ),
and bulbo-urethral glands (5)
23
External genitalia
- Scrotum and penis
- Penis is tubular organ that conducts both urine
and sperm to the outside (through the urethra) - Divided into root, body, and glans
- Fold of skin over glans is the prepuce or
foreskin (circumcision removes this) - Smegma is a waxy secretion secreted by preputial
glands in prepuce
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External continued
- Penis contains erectile tissue in 3 columns
- Parasympathetic innervatiaon of the penile
arteries involve neurons that release Nitrous
oxide (NO) - NO causes atrial walls to relax, vessels dilate,
blood enters erectile tissue and an erection
occurs - Corpora cavernosa (2 columns)-surrounds a central
artery - Corpus spongiosum (1 column)-surround urethra
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Erectile tissue
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Male Hormones
- FSH targets nurse cells in seminiferous tubules
(promotes spermatogenesis) and (secretes androgen
binding protein) - Spermatogenesis is under negative feedback
control - Inhibin from nurse cells inhibits FSH from
anterior pituitary and maybe GnRH at hypothalamus
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Male hormones continued
- LH induces the secretion of testosterone and
other androgens by the interstitial cells of the
testes - Testosterone is responsible for male secondary
sex characteristics, sexual drive, stimulates
spermatogenesis, and maintains accessory glands
and organs of male reproductive tract
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