male reproductive

Question 1

Primary sex organs and accessory reproductive organs

Answer 1

Primary sex organs (gonads) - testes and ovaries

• Produce gametes (sex cells ) – sperm & ova
• Secrete steroid sex hormones
• Androgens (males)
• Estrogens and progesterone (females)

Accessory reproductive organs - ducts, glands, and external genitalia

Question 2

role of sex hormones

Answer 2

• Development and function of reproductive organs
• Sexual behavior and drives
• Growth and development of many other organs and tissues

Question 3

Testes

Answer 3

w/in scrotum
make sperm
sperm goes thru epididymis –> ductus deferens –> ejaculatory duct –> urethra

Question 4

male accessory glands

Answer 4

seminal glands
prostate
bulbo-urethral

empty secretions into ducts during ejaculation

Question 5

Scrotum

Answer 5

sac of skin and superficial fascia
-hangs outside abdominopelvic cavity

Contains paired testes

• 3 C colder than core body temp
• lower temp necessary for sperm production

Temp kept constant by:

1. dartos muscle = smooth muscle which wrinkles scrotal skin and pulls scrotum close to body
2. cremaster muscles = bands of skeletal muscle that elevate testes

Question 6

Testes tunics and lobules

Answer 6

Each surrounded by two tunics

1. Tunica vaginalis – outer layer derived from peritoneum
2. Tunica albuginea – inner layer; fibrous capsule

Septa divide testis into ~250 lobules, each containing 1–4 seminiferous tubules - site of sperm production—about ½ mile of seminiferous tubules

Question 7

Testicular Torsion

Answer 7

MEDICAL EMERGENCY

Must be corrected within 2 hours to save the testes

Question 8

path of sperm inside the testes

Answer 8

sminiferous tubules –> straight tubule –> rete testis –> efferent ductules –> epididymis

Question 9

Seminiferous tubules: interstitial cells

Answer 9

Interstitial endocrine cells (Leydig cells) in soft tissue surrounding seminiferous tubules

Produce androgens (e.g. testosterone) and secrete it into interstitial fluid

Question 10

Blood supply to the testes

Answer 10

Testicular arteries arise from abdominal aorta

Testicular veins arise from pampiniform venous plexus surrounding each testicular artery

• Cooler; absorb heat from testicular arteries
• Keep testes cool

Spermatic cord encloses nerve fibers, blood vessels, and lymphatics that supply testes

Question 11

external genitalia

Answer 11

scrotum and penis

Question 12

Penis parts

Answer 12

root and shaft that ends in glans penis

prepuce/foreskin = cuff of loose skin covering glans

Crura = proximal ends of corpora cavernosa surrounded by ischiocavernosus muscle; anchors penis to pubic arch

Question 13

Circumcision

Answer 13

Surgical removal of foreskin

60% newborn boys in US circumcised

15% in other parts of world

Some claim medically unnecessary

Studies show

• 60% reduction in HIV risk
• Reduced risk for other reproductive system infections like HPV

Question 14

Penis: Internally

Answer 14

Spongy urethra and three cylindrical bodies of erectile tissue (spongy network of CT and smooth muscle with vascular spaces)

Corpus spongiosum surrounds urethra and expands to form glans and bulb

Corpora cavernosa = paired dorsal erectile bodies

Erection = erectile tissue fills with blood causing penis to enlarge and become rigid

Question 15

Epididymis
head, body, tail
duct
sperm flow

Answer 15

Head - contains efferent ductules; superior aspect of testis; body and tail on posterolateral area of testis

Duct of the epididymis ~ 6 m in length
-Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm

Nonmotile sperm enter, pass slowly through (~ 20 days), become motile; can be stored several months

During ejaculation epididymis contracts, expelling sperm into ductus deferens

Question 16

Ductus Deferens and ejaculatory duct

Answer 16

Ductus deferens (vas deferens) ~ 45 cm

Passes through inguinal canal to pelvic cavity

Expands to form ampulla; joins duct of seminal vesicle to form ejaculatory duct

Smooth muscle in walls propels sperm from epididymis to urethra

Question 17

Vasectomy

Answer 17

cutting and ligating ductus deferens; nearly 100% effective form of birth control. Must give time for any remaining sperm in the ducts to die.

Question 18

urethra

Answer 18

Conveys both urine and semen (at different times)

Has three regions

1. Prostatic urethra – surrounded by prostate
2. Intermediate part of the urethra (membranous urethra) – in urogenital diaphragm
3. Spongy urethra – runs through penis; opens at external urethral orifice

Question 19

Seminal Glands

Answer 19

On posterior bladder surface; smooth muscle contracts during ejaculation

Produces viscous alkaline seminal fluid

• Fructose, citric acid, coagulating enzyme (vesiculase), and prostaglandins
• Yellow pigment fluoresces with UV light
• 70% volume of semen

Duct of seminal gland joins ductus deferens to form ejaculatory duct

Question 20

Prostate

Answer 20

Encircles urethra inferior to bladder; size of peach pit; smooth muscle contracts during ejaculation

Secretes milky, slightly acid fluid

• Contains citrate, enzymes, and prostate-specific antigen (PSA)
• Role in sperm activation
• Enters prostatic urethra during ejaculation

1/3 semen volume

Question 21

Bulbo-urethral glands (cowper’s glands)

Answer 21

pea-sized glands inferior to prostate

make thick, clear mucus during sexual arousal

• lubricate glans penis
• neutralize traces of acidic urine in urethra

Question 22

Semen contents

Answer 22

Milky-white mixture of sperm and accessory gland secretions

2–5 ml semen ejaculated, contains 20–150 million sperm/ml

Contains fructose for ATP production; protects and activates sperm; facilitates sperm movement

Alkaline  neutralizes acidity of male urethra and female vagina  enhanced motility

Question 23

Semen functions

Answer 23

Prostaglandins decrease viscosity of mucus in cervix; stimulate reverse peristalsis in uterus

Contains ATP for energy

Suppresses female immune response

Antibacterial action

Clotting factors coagulate semen initially to prevent draining out; then liquefied by fibrinolysin  sperm begin journey

Question 24

Erection: what happens

Answer 24

Arterioles normally constricted

Sexual excitement causes CNS activation of parasympathetic neurons

nitric oxide (NO) release  local vascular smooth muscle relaxation

arterioles dilate  corpora cavernosa expands, retards venous drainage

engorgement of erectile tissues with blood

enlargement and stiffening of penis

Question 25

Initiation of erection

and protection of penis during

Answer 25

Initiated by sexual stimuli
-Touch; mechanical stimulation of penis; erotic sights, sounds, and smells

Can be induced or inhibited by emotions or higher mental activity

Longitudinal and circular collagen fibers around penis prevent kinking/buckling of erect penis

Corpus spongiosum keeps urethra open

Question 26

Ejaculation

Answer 26

Propulsion of semen from male duct system

Sympathetic spinal reflex

• Bladder sphincter muscle constricts, preventing expulsion of urine
• Ducts and accessory glands contract and empty their contents
• Bulbospongiosus muscles undergo rapid series of contractions  expulsion of semen at ~ 500 cm/s (close to 11 mph)

Ejaculatory event – orgasm

Question 27

HTG axis

Answer 27

Hypothalamus: Gonadotropin releasing hormone (GnRH)

• Simulates release of hormones from anterior pituitary that regulate function of testes
• Pulsatile release to produce stable FSH + LH levels

Anterior pituitary:
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH)

Testes:
Testosterone (T)
Inhibin
-both have negative feedback on hypothalamus and ant. pituit.

Question 28

Actions of FSH and LH

Answer 28

FSH causes sustenocytes (sustenacular cells/ Sertoli cells) to release androgen binding protein (ABP) –> binds testosterone and keeps it near spermatogenic cells for spermatogenesis

LH prods interstitial endocrine cells (Leydig) to secrete testosterone for spermatogenesis

Question 29

Testosterone and Inhibin

• when is inhibin released?

Answer 29

Testosterone = sex organ maturation, development/maintenance secondary sex characteristics, libido

Rising testosterone levels –> feedback inhibition on hypothalamus

Inhibin released when sperm count is high –> inhibits GnRH and FSH

Question 30

Development of HPG axis

Answer 30

takes 3 years to achieve balance, then testosterone and sperm porduction is fairly stable throughout life

Without GnRH and gonadotropins, testes atrophy; sperm and testosterone production cease

Question 31

Male secondary sex characteristics

Answer 31

Features induced in NONREPRODUCTIVE organs by male sex hormones

• pubic, axillary, and facial heair
• chest hair
• deep voice
• skin thickens and becomes oily
• skeletal muscles increase in size and mass
• bones grow and increase in density
• boosts BMR
• basis of sex drive in males

Question 32

Testosterone in embryo

Answer 32

masculinizes embryonic brain

continues to exert effect well into adulthood

adrenal glands produce androgens in small amounts– insufficient to maintain normal testosterone-mediated functions

Question 33

spermatogenesis

Answer 33

sperm (spermatozoa) production in seminiferous tubules

Spermatogenic cells give rise to sperm

• mitosis of spermatogonia (stem cells) forms 2 spermatocytes
• meiosis: spermatocytes –> secondary spermatocytes –> spermatids
• spermiogenesis = spermatids become sperm

Question 34

functions of meiosis

Answer 34

halve the number of chromosomes

introduce genetic diversity

Question 35

Mitosis of spermatogonia

Answer 35

Spermatogenesis begins at puberty

Spermatogonia = stem cells in contact with epithelial basal lamina
-each mitotic division = one type A daughter cell and one type B daughter cell

Type A cells maintain germ cell line at basal lamina

Type B cells move toward lumen and develop into primary spermatocytes

Question 36

Meiosis: spermatocytes to spermatids

Answer 36

Meiosis I
-primary spermatocytes (2n) –> two secondary spermatocytes (n)

Meiosis II

• each secondary spermatocyte (n) –> two spermatids (n)
• Spermatid = small, nonmotile cells close to lumen of tubule

Question 37

Spermatids to sperm

Answer 37

Spermatids
-correct chromosome number (n), but nonmotie

Spermiogenesis
-spermatids elongate; lose excess cytoplasm; form a tail –> spermatozoon (sperm)

Question 38

Sperm major regions

Answer 38

Head = genetic region; nucleus and helmet-like acrosome containing hydrolytic enzymes that enable sperm to penetrate egg

Midpiece = metabolic region; mitochondria –> ATP to move tail

Tail = locomotor region; flagellum

Question 39

Role of sustentocytes (sertoli cells)

Answer 39

Extend through wall of tubule and surround developing cells

Provide nutrients and signals to dividing cells

Move cells along to lumen

Secrete testicular fluid into lumen for sperm transport

Phagocytize faulty germ cells and excess cytoplasm

Produce chemical mediators to regulate spermatogenesis

Question 40

two compartments of sustentocytes

Answer 40

Tight junctions divide tubule into two compartments:

Basal compartment: spermatogonia and early primary spermatocytes

Adluminal compartment: meiotically active cells and tubule lumen

Question 41

Blood testis barrier

Answer 41

tight junction bt sustentocytes form this barrier

• prevents sperm antigens from escaping into blood –> activation of immune system
• important: sperm not formed until puberty - absent during immune system development, would not be recognized as self

Question 42

How long does spermatogenesis take?

What pushes immotile sperm into epididymis?

Answer 42

takes 64-72 days if conditions are hospitible

Pressure of testicular fluid pushes the sperm –> THEN they get their motility and fertilizing power