ALHT106 Lecture Notes - Lecture 5: Female Reproductive System, Seminiferous Tubule, Vas Deferens
Reproductive system functions:
-Only body system not vital for survival of individual; however it is vital for continuation of the
species
-Function of reproductive system: produce offspring (i.e next generation), via producing, storing,
nourishing and transporting gametes
-Reproductive organs and structures mature after onset of puberty
Male and female reproductive system functions:
Males: to make gametes/sex cells/sperm and deliver them to the female reproductive tract;
produce secretions to assist sperm survival in female reproductive tract
Female: to amen female gametes/ova; deliver an ovum to a fallopian tube each month; accept
male gametes; provide a protective environment for the developing foetus until birth; produce milk
for the newborn
Male reproductive system:
-Primary sex organs = gonads = testes
-Testes: produce gametes; produce reproductive hormones to
maintain normal sexual function
-Ducts: vas deferens, ejaculatory duct and urethra: receive
and transport gametes; urethra transports both urine and
semen
-Accessory glands= prostate and bulbourethral glands plus
seminal vesicles: secrete fluids- ducts- urethra to form
semen with sperm
-Perineal structures= penis and scrotum: form external
genetalia
-Penis delivers sperm to female reproductive tract
Penis:
-Tubular organ through which both urine and semen pass through via the urethra
-Root: attaches penis to body wall
-Shaft: tubular, moveable portion
-Glans: expanded distal end that surrounds the opening of the urethra; a prepuce/foreskin
surrounds and protects the glans unless removed by circumcision
-Majority of penis consists of three cylindrical columns of erectile tissue: 2 corpora cavernosa and
1 corpus spongiosum surrounding the urethra
Scrotum:
-Loose-fitting pouch holding testes; hangs outside torso at base of abdomiopelvic cavity
-Keeps sperm 2-3 degrees lower than normal body temperature for optimal viability
-Smooth muscle (dartos); in superficial dermis; resting muscle tone elevates testes and wrinkles
scrotal surface
-Skeletal muscle (Cremaster); deep in dermis; contraction during sexual arousal or drop in
temperature pulls testes closer to the body
Structure of the testes:
-Sperm formed in seminiferous tubules
-Testosterone produced in interstitial/leydig cells which lie between tubules
-Nurse/Sertoli/Sustentactular cells: support spermatogenesis; speriogenesis; bind FSH and
testosterone; secrete inhibit and androgen-binding protein (ADP); maintain blood-testis barrier
Spermatogenesis:
-Begins at puberty and continues for life; around 400 million sperm produced per day
-4 haploid spermatozoa (23 chromosomes) produced from each diploid stem cell (46
chromosomes)
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-Process takes about 70-80 days to complete; final maturation of sperm takes place in
epididymides
-Capacitation:
-sperm become motile with seminal vesicle secretions (fructose) and
-by having glycoprotein coat brushed off via contact with female reproductive tract
Spermiogenesis and spermatozoa:
-Sperm consists of: a head with an acrosome “cap” containing digestive enzymes; a “collar’ of
mitochondria; and a flagellum (tail)
Epididmis and Vas/Ductus Deferens:
-Epididymis
-comma shaped;
-where sperm mature
-Sperm can be stored for months in epididymides
-Vas deferens transports sperm to urethra with secretion from epididymis and seminiferous
tubules
Accessory glands:
-semen= mix of sperm and fluids from epididymis, seminiferous tubules and accessory glands
-2-5mL semen per ejaculation = 50-150 million sperm/mL = 100-750 million sperm
-Accessory gland secretions activate sperm, provide nutrients for motility, propel semen within
peristaltic contractions, and provide alkaline buffers
-Epididymides and seminiferous tubules provide 5% of semen fluid volume
-Seminal vesicles add 60% of semen fluid volume
-Seminal vesicles/gland secretions enter urethra via ejaculatory duct
-Fluid slightly alkaline (helps neutralise acidity)
-Fluids provide:
1. Fructose for mitochondria in sperm
2. Prostaglandins to stimulate smooth muscle contractions in male and female tracts
3. Fibrinogen to form temporary semen clot in vagina
-Prostate gland adds 20-30% of semen fluid volume
-Prostate fland secretion contain seminalplasmin, an antibiotic protein which may reduce UTI risk
-Also contains prostate-specific antigen (PSA) in low levels; levels increase in prostate cancer
-Bulbourethral gland (Cowper’s glands) adds remainder of semen fluids
-Bulbourethral gland adds thick, alkaline mucus preceding remainder of semen to
1. lubricate and neutralise traces of acidic urine in male urethra and female vagina
2. Lubricate glans peins
Female reproductive system:
-Primary sex organs: ovaries
-Ovary: produces gametes; produces reproductive hormones (oestrogen, progesterone and
inhibit) which maintain normal sexual function
-Ducts: fallopian tubes receive and transport ova
-Perineal structure: vulva; form external genitalia; sexual arousal; urination, menstruation; exit of
birth canal
-Accessory organs: uterus, vagina, mammary glands
Ovaries:
-Outer region= cortex: contains follicles (immature ovum)
-Inner region = medulla: contains nerves, blood and lymphatic
vessels
-Oogenesis begins in female foetus: lifetime supply of primary
oocytes (up to a million) at birth
-At puberty: small number activated each month- usually one
functional gamete (ovum)
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Uterus:
-Pear shaped organ; funds, body and cervix
-3 layers of uterine wall: endometrium, myometrium, perimetric
-Endometrium sloughed off and regrown each menstrual cycle
Sex hormones:
Male hormones:
-Testosterone production starts from week 7 of foetal development- development of a male duct
systems, accessory organs and CNS priming (programs hypothalamus for male sexual
behaviours and secretion go GnRH at puberty)
-From puberty: GnHR from hypothalamus in small regular pulses at 60-90 min intervals- LH and
FSH from anterior pituitary (hormone secretion maximum at different pulse rate for each)
-LH- release of testosterone; high testosterone acts as negative feedback to stop release of
GnRH- stops release of further LH
-FSH- initiation of spermatogenesis when nurse cells bind FSH
-Testosterone transported bound to carrier proteins- cells; in some target tissues testosterone
converted to dihydrotestosterone (DHT)
-Approx. 10% of circulating testosterone as DHT; external genitalia and prostate respond more to
dHT than testosterone
-Inhibin released by nurse cells as sperm count rises- negative feedback to stop FSH release
-Oestradiol/oestrogen in males synthesised by Lydia and germ cells: play major role in male
foetal reproductive tract development; play major role in regulating proteins involved in fluid
movement in efferent ductules; needed for Spermatogenesis and closure of epiphyses. Lack of
oestrogen- fertility problems
Role of testosterone:
-Functions of testosterone and DHT before birth include sex determination, masculinisation of
reproductive tract and external genitalia, testes descent
-After birth in sex-specific tissues e.g. bone and muscle, growth and maturation of reproductive
tract and organs, spermatogenesis, maintenance of reproductive tract in adulthood, develops
sex drive/libido, develops and maintains secondary sexual characteristics, aggression,
competitiveness
-Male secondary sexual characteristics include male pattern hair growth, vocal cord thickening-
deeper voice, muscle growth, thick skin
Female hormones:
-GnRH: released in pulses; - FSH secretion and LH production from anterior pituitary; pulses
increase with oestrogen and decrease with progesterone
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Document Summary
Only body system not vital for survival of individual; however it is vital for continuation of the species. Function of reproductive system: produce offspring (i. e next generation), via producing, storing, nourishing and transporting gametes. Reproductive organs and structures mature after onset of puberty. Males: to make gametes/sex cells/sperm and deliver them to the female reproductive tract; produce secretions to assist sperm survival in female reproductive tract. Female: to amen female gametes/ova; deliver an ovum to a fallopian tube each month; accept male gametes; provide a protective environment for the developing foetus until birth; produce milk for the newborn. Primary sex organs = gonads = testes. Testes: produce gametes; produce reproductive hormones to maintain normal sexual function. Ducts: vas deferens, ejaculatory duct and urethra: receive and transport gametes; urethra transports both urine and semen. Accessory glands= prostate and bulbourethral glands plus seminal vesicles: secrete uids- ducts- urethra to form semen with sperm. Perineal structures= penis and scrotum: form external genetalia.
