Reproductive System

BIOL347 Chapter 27

gamete formation

copulation

fertilization

gestation and parturition

what 4 processes are required for the production of offspring?

gamete formation

the production of sperm (the smallest cell produced by the body) and ova (the largest cell produced by the body)

copulation

sexual intercourse, sperm and egg must be brought together

fertilization

combining genetic content of the sperm and egg

gestation

pregnancy and development of the fetus

parturition

labor and delivery, the birth of the fetus

46

diploid number of humans?

23

haploid number of humans?

meiosis

nuclear division that occurs only in the gonads and results in the formation of gametes

testes

ovaries

what are the 2 gonads?

reduces the number of chromosomes in gametes by one half

produces genetic variability

importance of meiosis? (2)

genetic variability allows for differential survival when in contact with pathogens

why would meiosis increase species survival?

sperm and egg must be haploid so the offspring has the correct diploid number

why is meiosis absolutely necessary?

Trisomy 21 (Down Syndrome)

well known condition where individuals do not have the correct diploid number?

chromosomes replicate, forming sister chromatids

before meiosis begins, what occurs in the parent cell?

homologous chromosomes synapse to form tetrads

crossing over occurs

step 1 of meiosis I (2 parts)?

homologous chromosomes

share the same set of genetic info but are one copy from each parent

crossing over

the source of genetic variability in our population- genes get flip flopped between chromosomes

tetrads align randomly on spindle plate

step 2 of meiosis I?

Homologous chromosomes separate & move to opposite poles

step 3 of meiosis I?

sister chromatids

what does NOT get separated during step 3 of meiosis I?

cleavage occurs

step 4 of meiosis I?

production of two daughter cells that are genetically distinct but still diploid

what is the result of meiosis I?

formation of a new spindle

step 1 of meiosis II?

chromosomes line up at the equator

step 2 of meiosis II?

sister chromatids separate and move to opposite poles

step 3 of meiosis II?

cleavage occurs

step 4 of meiosis II?

4 daughter cells that are haploid

what is the result of meiosis II?

Hypothalamic-Pituitary-Gonadal (HPG) axis

the interaction of hormones released by the hypothalamus, anterior pituitary, and gonads

regulates hormonal release by gonads, so regulates gamete formation, reproductive organ function, etc.

what is the function of the HPG axis?

releases gonadotropin-releasing hormone (GnRH), which circulates to pituitary to activate

Hypothalamus’s role in the HPG axis

releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in response to GnRH release

Anterior Pituitary gland’s role in the HPG axis

release sex hormones (testosterone, estrogen, progesterone) and produce gametes in response to FSH and LH release

Gonads’ role in HPG axis

scrotum

enclose and protect testes

composed of skin and superficial fascia (connective tissue)

allows testes to be 3 degrees lower than internal body temperature

importance of scrotum?

optimal temperature for spermatogenesis, warmer temp would slow sperm production and/or result in abnormal sperm

why do the testes need to be 3 degrees cooler than body?

Dartos muscle

Cremaster muscle

2 muscles that allow testes to maintain their optimal temperature?

Dartos muscle

changes surface area of scrotal tissue; less surface area= less heat loss

decreases surface area of the testes

contraction of the dartos muscle?

Cremaster muscle

changes position of the testes

testes are brought closer to the body

contraction of the cremaster muscle?

testicular arteries

supply each testis with O2 and nutrients needed for spermatogenesis

testicular veins

drain testis of waste

help temperature control: absorbs heat from arterial blood to prevent the testes from becoming too warm

decrease sperm production (bc not necessary for survival)

sympathetic innervation of the testes will

increase sperm production

parasympathetic innervation of the testes will

spermatic cord (bundle of everything the testes need)

nerve fibers, blood vessels, ductus deferens, and lymphatics all travel together, forming the …

seminiferous tubules

location of sperm production: sperm producted in the walls of the _____

rete testis

immature sperm move through the ________ to get to the epididymis

rete testis

a set of smaller tubes off to the side of the seminiferous tubules, lead into the epididymis

testicular cancer

formation of a malignant tumor in one or both testes (usually just one)

can effect ages 20-50, most common in 30s

seminoma

non seminoma

two types of testicular cancer

seminoma testicular cancer

more common, less threatening, less aggressive, easily treated with chemotherapy and radiation

non-seminoma testicular cancer

more dangerous and aggressive, more likely to become metastatic, can use chemo and radiation but may need testicle removed

painless lump or swelling of testis

dull pain in lower pelvis/ lower back (as the tumor pushes on other structures)

symptoms of testicular cancer

genetics and family history

Klinefelter syndrome

persistent/chronic inflammation

causes of testicular cancer

a mutation of chromosome 12 is heavily linked to testicular cancer

genetic influence of testicular cancer

Klinefelter syndrome

sex chromosomes are XXY

individuals have male reproductive organs but have a complicated hormone balance and reproductive function, increasing cancer rates

increases chance of all forms of cancer

a bacterial/ viral infection in testes left untreated can cause cancer

persistent/ chronic inflammation role in TC

95%

testicular cancer survival rate

human chorionic gonadotropin (hCG) (can turn pregnancy tests positive)

some testicular cancers cause men to release

epididymis

accessory duct to testes

stores immature sperm

as sperm travel through, they develop their ability to swim

what happens to sperm that do not leave the epididymis?

sperm can remain here for months, but older sperm don’t function as well→ they will be phagocytized and destroyed so they arent a ‘waste of space’

ductus (vas) deferens

accessory duct to the testes

transports sperm out of epididymis during ejaculation

ends at ampulla

ampulla ends at ejaculatory duct

ejaculatory duct empties into urethra

vasectomy

ductus deferens is cut of cauterized

can take 2-3 months to be completely effective

testes still produce the normal amount of sperm, but they are unable to leave the body

can be reversed but not in 100% of cases

seminiferous tubules

rete testis

epididymis

ductus deferens

ampulla (of ductus deferens)

ejaculatory duct

urethra

path of sperm from production to ejaculation? (7)

urethra

accessory duct to the testes

terminal portion of male duct system

3 parts: prostatic, intermediate, spongy

prostatic urethra

portion surrounded by prostate gland

intermediate urethra

connects prostatic to spongy

spongy urethra

runs through penis (corpus SPONGiosum) and opens to the exterior of the body

penis

delivers sperm to female reproductive tract during copulation

glans

end (head) of penis

prepuce

foreskin surrounding glans

circumcision

removes prepuce

entirely cultural: 80% of US is circumcised but only 20% of the rest of the world

some reduction in the likelihood of infection, especially in infants

erectile tissue

contains connective tissue, smooth muscle, and vascular space

vascular spaces fill with blood during arousal

2: corpus spongiosum, corpora cavernosa

corpus spongiosum

immediately surrounds urethra, forms a circle to help keep urethra open (so semen can exit)

distal portion forms glans

corpus spongiosum

what tissue forms the glans?

corpora cavernosa

paired structures that make up most of penile tissue, mostly responsible for erection

seminal glands

secrete fructose, prostaglandins, and proteins (esp. relaxin) into the ejaculatory duct, form the fluid portion of sperm

relaxin

protein secreted by seminal glands that enhances sperm motility, smaller role in regulating testicular function

sperm will begin to swim harder and faster, their cue to get moving

prostate gland

composed of 20-30 glands

produces citrate, useful for ATP production

produces prostate-specific antigen, makes semen more liquid and breaks down some of its content

other substances help activate sperm

its smooth muscle will contract during ejaculation to release its contents

prostate-specific antigen

makes semen more liquid and breaks down some of its contents

prostate cancer

affects 1 in 6 men

usually devlops in 50s

can be slow growing or highly aggressive

men will usually die with it, but not because of it

difficulty urinating (tumor constricts prostatic urethra)

blood in urine/ semen

erectile dysfunction (tumor impairs blood supply to erectile tissues)

usually symptomless in earlier stages

symptoms of prostate cancer (4)

benign prostatic hyperplasia

benign growth on prostate

composed of normal (noncancerous) prostate cells, just too many of them

constricts prostatic urethra → makes urination difficult and painful, can have many of the same symptoms as prostate cancer

bulbourethral glands

produces an alkaline mucus

sperm are especially sensitive to acidic conditions: acidic urine can be left in urethra and the vagina is highly acidic, helps sperm survive

importance of the alkaline mucus from bulbourethral glands ?

semen

sperm + accessory gland secretions

secretions: prostaglandins, relaxin, fructose, antibiotic components, clotting factors, immune sectretions that supress the female immune system

prostaglandins

relaxin

fructose

antibiotic components

clotting factors

5 specific seminal secretions?

prostaglandins

decrease the viscosity of mucus in the female cervix

stimulate reverse peristalsis in uterus- faster transport of sperm → egg

fructose

catabolized for sperm ATP synthesis

antibiotic components (semen)

destroy bacteria that could harm sperm

clotting factors (semen)

coagulate sperm after ejaculation so it doesnt leave the vagina as easily

‘other’ seminal secretions

suppress the female immune system; females are still primed to kill anything that doesn’t belong

spermatogenesis

production of male gametes

occurs in the walls of seminiferous tubules

sustenocytes

spermatogenic cells (spermatogonia and spermatogoa)

myoid cells

interstitial endocrine cells

4 cell types of seminiferous tubules

sustenocytes

surround, support, and nourish developing sperm, ensure sperm develop normally

adjacent cells form tight junctions to prevent sperm from escaping → increases sperm count

sustenocytes

what makes up the bulk of the walls of seminiferous tubules?

spermatogenic cells

sperm forming cells

spermatogonia (diploid stem cells) undergo meiosis to form spermatogoa (actual sperm)

myoid cells

contract similar to peristalsis to move immature sperm from tubules to epididymis (immature sperm cannot yet swim)

interstitial endocrine cells

secrete testosterone and a small amount of estrogen

spermatogenesis depends on testosterone being around other cell types