male reproductive system anatomy
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gonads (testes) produce sperm & secrete hormones
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system of ducts (ductus epididymis, ductus deferens, ejaculatory duct, urethra) transport & stores sperm, assists in their maturation, conveys them to the exterior
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accessory sex glands (Seminal vesicles, prostate gland, bulbourethral glands) adds secretions to semen
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supporting structures scrotum supports testes, penis delivers sperm into female reproductive tract
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scrotum a cutaneous outpouching of the abdomen that supports the testes, normal sperm production & survival requires a temperature 2-3 degrees below core body temperature
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testes/testicles paired oval glands that descend from the abdomen to the scrotum during the 7th month of fetal development, covered by a fibrous tissue called tunica albuginea, invaginations form 200-300 compartments called lobules, each lobule is filled with 2 or 3 seminiferous tubules (spermatogenesis)
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perineum
- Diamond-shaped area medial to thighs and buttocks of males and females
- Contains external genitalia and anus
- During childbirth the emerging fetus may cause excessive stretching and tearing of the perineum. A physician may make a surgical incision (episiotomy) in this region to prevent excessive, jagged tears |
accessory sex glands
seminal vesicles (60% of vol) |
viscous alkaline fluid that helps neutralise acid environment |
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contains fructose for ATP production by sperm |
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& prostaglandins contribute to perm motility & viability |
prostate glans (25% of vol) |
single donut shaped gland that secretes milky, slightly acid fluid |
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it contains 1) citric acid (ATP production via Krebs) |
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2) several proteolytic enzymes |
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3) PSA - prostate specific antigen |
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4) seminalplasmin (antibiotic) |
paired bulbourethral (cowper's) glands |
secrete alkaline fluid that protects passing sperm by neutralising acids from urine in urethra |
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mucus lubricates end of penis & lining of urethra |
vagina
Fibromuscular canal extending from exterior of body to uterine cervix |
Mucosa continuous with uterine mucosa |
Decomposition of glycogen makes acidic environment hostile to microbes and sperm |
Alkaline components of semen raise pH |
functions as a passageway for spermatozoa & the menstrual flow, the receptacle of the penis during sexual intercourse, and the lower portion of the birth canal
4 inch long fibromuscular organ ending at cervix
- mucosal layer
- muscularis layer is smooth muscle allows considerable stretch
- adventitia is loose connective tissue that binds it to other organs
fallopian tubes
provide route for sperm to reach an ovum |
site of fertilisation |
transport secondary oocytes & fertilised ova from ovaries to uterus |
Infundibulum ends in finger-like fimbriae; Produce currents to sweep secondary oocyte into tube |
Ampulla – widest longest portion |
Isthmus – joins uterus |
Three layers:
1) Mucosa – ciliary conveyor belt,
peg cells provide nutrition to ovum
2) Muscularis – peristaltic contractions
3) Serosa – outer layer
oogenesis & follicular development
- results in formation of a single haploid secondary oocyte
- during early foetal development, primordial primitive germ cells migrate from yolk sac to ovaries
- differentiate into oogonia - diploid 2n stem cells
- before birth, most germ cells degenerate - atresia
- a few develop into primary oocytes that enter meiosis I during foetal development
- Each covered by single layer of flat follicular cells – primordial follicle
- About 200,000 to 2,000,000 at birth in each ovary, 40,000 remain at puberty, and around 400 will mature and ovulate during a lifetime |
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Testes cells
leydig cells (interstitial endocrinocytes) |
found in spaces between adjacent seminiferous tubules secrete the male hormone testosteone |
sertoli cells |
embedded among spermatogenic cells in tubules , form blood testes barrier, nourish spermatocytes, mediate effects of testosterone & FSH on spermatogenesis, phagocytose excess spermatids, secrete inhibin hormone which helps regulate sperm production by inhibiting production of FSH |
mammary glands
modified sudoriferous (sweat) glands that produce milk (lactation)
15-20 lobes divided into lobules composed of alveoli (milk-secreting glands)
Milk secreting glands open by lactiferous ducts at the nipple
Areola – pigmented area around nipple |
external female genitalia
Mons pubis |
fatty pad cushions pubic symphysis |
Labia majora |
homologous to scrotum |
Labia minora |
homologous to spongy (penile) urethra |
Clitoris |
small mass of erectile tissue and numerous nerves/blood vessels homologous to glans penis |
Vestibule |
region between labia minora |
Bulb of the vestibule |
2 elongated masses of erectile tissue on either side of vaginal orifice |
secretions & functions
Secretory cells of the mucosa of the cervix produce a cervical mucus (a mixture of water, glycoprotein, serum-type proteins, lipids, enzymes, and inorganic salts)
- when thin, is more receptive to sperm
- when thick, forms a cervical plug that physically impedes sperm penetration
- mucus supplements the energy needs of the sperm
The cervix and the mucus also play a role in capacitation - renders them competent to fertilise an oocyte |
oogenesis
- Once secondary oocyte is formed it begins meiosis II but stops at metaphase
- At ovulation, secondary oocyte expelled with first polar body
- If fertilisation does not occur, cells degenerate
- If a sperm penetrates secondary oocyte, meiosis II resumes
- Secondary oocyte splits into 2 cells of unequal size -second polar body (discarded), ovum or mature egg
- Nuclei of sperm cell and ovum unite to form diploid zygote- fertilisation |
follicular development
Each month from puberty to menopause, FSH and LH stimulate the development of several primordial follicles (one reaches ovulation)
Just before ovulation, diploid primary oocyte completes meiosis I
Produces 2 unequal sized haploid (n) cells – secondary oocyte
and first polar body (discarded) |
female reproductive system
ganads (ovaries) |
produce secondary oocytes & hormones |
uterine fallopian tubes or oviducts |
transport fertilised ova |
uterus |
where foetal development occurs |
vagina |
external organs |
vulva or pudendum |
mammary glands |
produce milk |
penis
- passageway for ejaculation of semen
- body composed of 3 erectile tissue masses filled with blood sinuses surrounded by smooth muscle & elastic connective tissue |
erection: parasympathetic fibers release/cause local production of nitric oxide, dilates arterial smooth muscle, large amounts of blood enter blood sinuses, compresses veins draining the penis
sperm morphology
adapted for reaching & penetrating a secondary oocyte |
head contains DNA (23 Chromosomes) & acrosome |
acrosome has enzymes that help sperm penetrate secondary cycle (hyaluronidase & proteinase) |
midpiece contains mitochondria to form ATP |
produced at rate of 300 million/day |
life expectancy = 48hrs in female reproductive tract |
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ovaries
- paired glands homologous to testes
- produce: gametes (secondary oocytes that develop into mature ova after fertilisation, & hormones including progesterone, estrogens, inhibin & relaxin
ligaments hold ovaries in place:
1. broad ligament - a fold of parietal peritoneum
2. ovarian ligament - anchors ovaries to uterus
3. suspensory ligament - attaches ovaries to pelvic wall |
histology:
- germinal epithelium covers surface of ovary
- tunica albuginea located underneath epithelium
- ovarian cortex = ovarian follicles & stromal cells
- ovarian medulla contains blood vessels, lymphatic vessels & nerves
- ovarian follicles in cortex consist of oocytes in various stages of development
- mature graafian follicle is a large, fluid-filled follicle ready to expel secondary oocyte during ovulation
- corpus luteum - remnants of mature follicle after ovulation
uterus (womb)
Functions
- the transport of spermatozoa, menstruation, implantation of fertilised ovum, development of foetus during in pregnancy and labour
Anatomically – can be subdivided into:
- Fundus
- Body
- Isthmus
- Cervix (opens into vagina)
blood supply:
Uterine arteries branch as arcuate arteries and radial arteries that supply the myometrium
Straight & spiral branches penetrate to the endometrium
- spiral arteries supply the stratum functionalis
- their constriction due to hormonal changes starts menstrual cycle |
histology: 3 layers
(1) Perimetrium – outer layer
(2) Myometrium
- 3 layers of smooth muscle
- contractions in response to oxytocin from posterior pituitary
(3) Endometrium – inner layer
- highly vascularized
Stratum functionalis
- lines cavity, sloughs off during menstruation
Stratum basalis
- permanent, gives rise to new stratum functionalis after each menstruation
male reproductive ducts
ducts of testis |
series of coiled efferent ducts that empty into epiididymis |
epididymis |
site of sperm maturation & storage |
ductus (vas) deferens |
conveys sperm during sexual arousal through peristaltic contractions |
spermatic cord |
ductus deferens ascends out of scrotum with arteries/veins, autonomic nerves, lymphatic vessels & cremaster muscle |
ejaculatory ducts |
formed by union of ducts from seminal vesicle & ductus deferens, terminating in the prostatic urethra |
urethra |
shared terminal duct of reproductive & urinary systems, subdivided into: prostatic urethra, membranous urethra, spongy penile urethra |
spermatogenesis
produces haploid sperm (n) = one set of 23 chromosomes from diploid spermatogonia (2n) |
takes approx. 74 days |
meiosis I - process = reduction division, homologous pairs line up to form a tetrad (4 chromatids from each homologous pair) & the two cells formed by this nuclear division are called secondary spermatocytes (haploid) |
each of 23 chromosomes is still made up of 2 chromatids attached at centromere |
goes through meiosis II = equatorial division, 2 chromatids separate (no DNA replication) |
results in 4 spermatids - each haploid & unique, 50% X chromosome & 50% Y. |
spermiogenesis = development of spermatids into sperm, acrosome & flagella (tail) form, mitochondria multiply
spermiation = release from connections to sertoli cells
female reproductive cycle
Encompasses ovarian and uterine cycle, hormonal changes that regulate them, and related changes in breast and cervix |
controlled by monthly hormone cycle of anterior pituitary, hypothalamus and ovary |
ovarian cycle: changes in ovaries that occur during and after maturation of oocyte
Uterine (menstrual) cycle: concurrent series of changes in uterine endometrium preparing it for arrival of fertilized ovum. if implantation does not occur the stratum functionalis is shed during menstruation
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