Physiology 2130 Lecture Notes - Lecture 9: Vas Deferens, Male Reproductive System, Seminiferous Tubule
5 May 2018
School
Department
Course
Professor
Reproductive Physiology –Dr. Beye
Male Reproductive System
▪ The function of the male reproductive system is to produce hormones and sperm
▪ Reproductive system is not essential in maintaining homeostasis but is crucial for
producing offspring
o Hysterectomy- remove uterus and ovaries but can still live
o Castration – removal of testes
o Pets get spayed or neutered
▪ All can still live a normal life
▪ Site of hormone and sperm production is the testis
o Testes are located inside the scrotum- found externally in humans
o Testes must have a temperature that is approximately 2° C below normal body
temperature to produce viable, healthy sperm
▪ Being on the exterior of the body allows for cooling
▪ Cremaster muscles can elevate position of the testes for temperature
regulation
▪ Testes
o Where sperm is made
▪ Does’t produe ell at 37° C
▪ Best at 34° C
▪ Muscles surrounding testes
will raise or lower the temp.
o Seminiferous tubules
▪ Sperm and fluid are produced
▪ Over 100 million spermatozoa
made/day
o Epididymis
▪ Sperm storage and maturation
▪ Takes ~70 days for sperm to reach this area
o Vas deferens
▪ Important for sperm and fluid release via urethra into female
▪ Seminiferous tubule
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▪ Spermatogenesis
o Process is initiated at puberty where sufficient testosterone is produced to
enable spermatogenesis
o Leydig cells produce testosterone that diffuses to Sertoli cells to support
spermatogenesis
o Spermatogonia
▪ Cells at the outermost edge
▪ Kind of like stem cells
• Can continuously divide via
mitosis
o 1° spermatocytes
▪ Have 46 chromosomes
▪ Undergo meiosis I to generate 2
genetically unique cells (2°
spermatocytes)
o 2° spermatocytes
▪ Have 23 chromosomes
▪ Undergo meiosis II to generate 4 spermatids
o Spermatids
▪ Have 23 chromosomes
o Spermatozoa
▪ Immature sperm
▪ Ca’t si
▪ Close to lumen so it can be released
▪ Hormonal Regulation of Testosterone
o Gonadotropin Releasing Hormone (GnRH)
controls the release of the gonadotropins
Luteinizing Hormone (LH) and Follicle
Stimulating Hormone (FSH)
o FSH signals Sertoli Cells which support
spermatogenesis
o LH singles Leydig cells which stimulates
increased testosterone production
▪ Increased testosterone supports
spermatogenesis
▪ Increased testosterone also inhibits LH and FSH as well as GnRH
production via negative feedback
▪ Other Functions of Testosterone
o Testosterone binds androgen receptors inside the cell
o Causes anabolic reactions (muscle mass increase)
▪ Using anabolic steroids
• Makes more RBC thicker blood
• In males, causes shrinking of testes due to under stimulation (no
GnRH, FSH and LH production)
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find more resources at oneclass.com
o (-) feedback loop shuts off the hypothalamus and the anterior pituitary
(endocrine effects)
o Leydig cells Testosterone signals Sertoli Cells (paracrine effect)
o Secondary sex characteristics (hair growth, deep voice)
▪ Male Reproductive System
o Sperm is made in the testes
o Stored in the epididymis
o Travels up the vas deferens
o Travels through the seminal vesicles
through the prostate via the
ejaculatory ducts
o Leaves through the urethra
▪ Vasectomy = cutting the vas deferens
▪ Benign Prostate Hyperplasia
o Enlarged prostate due to too much testosterone
o Symptoms
▪ Urinary problems
• Caused by squished urethra
• Ca’t uriate/ a’t epty ladder opletely
▪ Secretions Found in Semen
o Semen = sperm + secretions
o 1. Seminal vesicles: 60% of volume of semen comes from here
▪ Secretions include: fructose, clotting proteins (alkaline)
o 2. Prostate Gland: 30% of volume
▪ Citric acid, enzymes (slightly acidic)
o 3. Bulbourethral Gland: minor contributes
▪ Mainly mucus (alkaline)
o Composition is important for sperm survival to optimize pregnancy
Female Reproductive System
▪ Function varies over lifespan
▪ Two ovaries are located inside the pelvis, suspended on either side of the uterus
▪ Reproductive cells called oocytes are produced through the process of oogenesis
o Starts with cells called oogonia – are produced prior to birth
▪ ~5-10 million oogonia are produced in
each ovary
o Up to 1 million oogonia progress to the primary
oocyte stage around the time of birth
o During puberty, primary oocytes undergo
reruitet, stiulated y horoal hages,
where a small pool of oocytes will develop into
secondary oocytes – can be ovulated
Secretion is alkaline
since female
reproductive organs are
aidi ad sper a’t
survive in acidic
environments
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Important for sperm and fluid release via urethra into female: seminiferous tubule, spermatogenesis, process is initiated at puberty where sufficient testosterone is produced to enable spermatogenesis, leydig cells produce testosterone that diffuses to sertoli cells to support spermatogenesis. Immature sperm: ca(cid:374)"t s(cid:449)i(cid:373, close to lumen so it can be released, hormonal regulation of testosterone, gonadotropin releasing hormone (gnrh) controls the release of the gonadotropins. Stimulating hormone (fsh: fsh signals sertoli cells which support spermatogenesis, lh singles leydig cells which stimulates increased testosterone production. In males, causes shrinking of testes due to under stimulation (no. Seminal vesicles: 60% of volume of semen comes from here: secretions include: fructose, clotting proteins (alkaline, 2. Prostate gland: 30% of volume: citric acid, enzymes (slightly acidic, 3. Bulbourethral gland: minor contributes: mainly mucus (alkaline) Secretion is alkaline since female reproductive organs are a(cid:272)idi(cid:272) a(cid:374)d sper(cid:373) (cid:272)a(cid:374)"t survive in acidic environments: composition is important for sperm survival to optimize pregnancy.
