Ch 27 The Reproductive System

what is the function of the reproductive system?

for the production of offspring

what are the 4 processes that allow for the production of offspring?

1. gamete formation

2. copulation

3. fertilization

4. gestation and parturition

what is gamete formation?

sperm and ova (egg)

what is copulation?

sperm and egg must be brought together

what is fertilization?

combining genetic content of the sperm and the egg

what is gestation and parturition?

development and birth of the fetus

what is meiosis?

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

what is the important features of meiosis?

1. they reduce the number of chromosomes in gametes by one half

2. produces genetic variability

what happens before meiosis begins?

chromosomes in diploid (2n) parent cells replicate

what do we call replicate chromosomes?

sister chromatids

meiosis I

• homologous chromosomes synapse to form tetrads

• crossing over occurs

• tetrads align randomly on spindle plate

• homologous chromosomes separate & move to opposite poles

• cleavage occurs

do sister chromatids separate when homologous chromosomes separate and move to opposite poles?

they do not

what is the result of meiosis I?

the formation of 2 genetically distinct, haploid (n) daughter cells from a single diploid (2n) parent cell.

what does crossing over mean?

the exchange of genetic material between homologous chromosomes during prophase I of meiosis I

what is meiosis II

Formation of new spindle

• Chromosomes line up at equator

• Sister chromatids separate & move to opposite poles

• Cleavage occurs

what is the result of meiosis II?

production of 4 unique haploid (n) daughter cells

hypothalamic-pituitary gonadal (HPG) axis

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

what are the structures of the HPG axis?

1. hypothalamus

2. anterior pituitary gland

3. gonads

what does the hypothalamus do

it releases gonadotropin-releasing hormone (GnRH)

what does the anterior pituitary gland do

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

what do gonads do

they release sex hormones and produce gametes in response to LH and FSH

what are the male gonads?

testes

what are the testes enclosed and protected by?

the scrotum

why is the scrotum important for the testes?

it allows the testes to be about 3 degrees lower than internal body temp (specifically the musculature does this)

• this is necessary so there is a larger amount of sperm to be produced

what is dartos muscle?

it changes the surface area of scrotal tissue by changing how much heat is lost

what is cremaster muscle?

it changes position of testes, it is relative to abdominal pelvic cavity so it increases/decreases temp of testes

what supplies each testis?

testicular arteries

what drains the testes of blood?

testicular veins

what do nerve fibers, blood vessels, ductus deferens, and lymphatics form?

the spermatic cord

what is the function of seminiferous tubules?

sperm production, immature sperm move thru rete testis to epididymis

what is testicular cancer

formation of malignant tumor in one or both testes

• can be seminoma (grow slowly, highly radiation sensitive)

• or non-seminomas (grow and spread fast, requires diff chemotherapy)

what are the symptoms of testicular cancer?

painless lump or swelling of testis, dull pain in lower pelvis and/or lower back

what is testicular cancer caused by?

genetics & family history, Klinefelter syndrome, persistent/chronic inflammation

what is the treatment for testicular cancer?

chemotherapy & radiation, surgery

what does the epididymis store?

immature sperm, sperm travels thru duct and develops the ability to swim

what happens to sperm that does not leave the epididymis?

it is naturally broken down by macrophages (cleanup cells) and reabsorbed into the epididymis, takes 7 months

what transports sperm out of epididymis during ejaculation?

ductus deferens (vas deferens)

where does ductus deferens end at?

the ampulla

where does ampulla end at?

the ejaculatory duct, where it then empties into the urethra

what is it called when the ductus deferens is cut or cauterized?

vasectomy

what is the urethra?

the terminal portion of male duct system

what are the 3 divisions that the urethra is broken down into?

1. prostatic urethra

2. intermediate part

3. spongy urethra

what is the prostatic urethra?

portion surrounded by prostate gland

what is the intermediate part of urethra?

connects prostatic urethra to spongy urethra

what is the spongy urethra?

runs thru penis and opens to exterior of body

what is the male copulatory organ?

the penis

what is the function of the penis?

to deliver sperm to female reproductive tract during copulation

where does the penis end in?

the glans, it is surrounded by the prepuce

what is erectile tissue?

it contains connective tissue, smooth muscle, and vascular space (these spaces are filled w blood)

what are the 2 erectile bodies?

1. corpus spongiosum

2. corpora cavernosa

what is the corpus spongiosum?

it immediately surrounds the urethra

• distal portion of it forms glans

what is the corpora cavernosa?

paired structures that make up most of penile tissue

what are the accessory glands of male reproductive system?

1. seminal glands

2. prostate

3. bulbo-urethral glands

what are the seminal glands?

they empty into ejaculatory duct

what are the secretions produced by the seminal glands?

fructose, prostaglandins, proteins

what is the prostate?

composed of 20-30 glands, produces citrate, prostate-specific antigen, and substances that help activate sperm

• smooth muscle walls contract during ejaculation to release contents

what are the bulbo-urethral glands?

it produces alkaline mucus, this is important bc it is acidic

what is semen?

the combo of sperm with accessory gland secretions

what is function of prostaglandins in semen?

they decrease viscosity of mucus in female cervix, stimulate reverse peristalsis in uterus

what is function of relaxin in semen?

to promote & enhance sperm motility

what is the function of fructose in semen?

catabolized for sperm ATP synthesis

what is the function of antibiotic components of semen?

they destroy bacteria that could harm sperm

what is the function of clotting factors of semen?

coagulate semen after ejaculation

what is spermatogenesis?

production of male gametes

what are the important cell types of seminiferous tubules?

1. sustenocytes

2. spermatogenic cells

what are sustenocytes?

they surround, support, and nourish developing sperm

what prevents sperm from escaping?

adjacent sustenocytes joined by tight junctions

what are spermatogenic cells?

sperm-forming cells

what are myoid cells?

contract to move immature sperm from tubules→epididymis

what are interstitial endocrine cells?

secrete testosterone (with small amount of estrogen)

what is spermatogenesis?

• spermatogonia is divided by mitosis

• after puberty is when some spermatogonia become Type A daughter cells while others become Type B daughter cells

what type of cell becomes the primary spermatocytes?

Type B cells

• Type A instead renews thru mitosis

what do primary spermatocytes undergo?

meiosis I to form secondary spermatocytes

what do secondary spermatocytes undergo?

meiosis II to form spermatids

what do spermatids undergo?

spermatogenesis, where it produces functional but still immature sperm

what are the 3 general areas of sperm?

1. head

2. midpiece

3. tail

what does the head of sperm hold?

genetic material

what is the acrosome?

part of the sperm head, it is a helmetlike structure that holds hydrolytic enzymes

what does the midpiece of the sperm hold?

mitochondria, it is the metabolic area of sperm

what does the tail of sperm do?

it is the locomotor region with flagellum

what do we already know about the HPG axis?

1. hypothalamus releases GnRH

2. GnRH stimulates anterior pituitary to release FSH and LH

what is specific only to males regarding the HPG axis?

1. LH stimulates interstitial endocrine cells of testes to secrete

testosterone

2. FSH stimulates sustenocytes to release androgen-binding protein (ABP)

does ABP keep local testosterone levels in testes high or low?

high

during an erection, what happens when a male is not aroused?

arterioles supplying erectile tissue are not constricted

during an erection, what happens when a male is aroused?

parasympathetic system stimulates release of nitric oxide (NO)

what is ejaculation?

propulsion of semen from the duct system

what is ejaculation caused by?

the initiation of spinal reflex

what happens during ejaculation?

1) Accessory glands contract & release contents to prostatic urethra

2) Internal sphincter of bladder closes

3) Bulbospongiosus muscles of pelvis contract rapidly to propel

semen out of the body

what are the female gonads?

ovaries

what are the ovaries supported by?

1. ovarian ligament

2. suspensory ligament

3. broad ligament

what does the ovarian ligament anchor?

ovary to uterus

what does the suspensory ligament anchor?

ovary to pelvic wall

what does the broad ligament enclose?

the ovarian ligaments and supports uterine tubes, uterus, and vagina

what does each ovary have?

a outer cortex and inner medulla

what is found in the outer cortex of an ovary?

its where forming gametes are found

what is found in the inner medulla of an ovary?

contains blood vessels and nerves that serve ovaries

what is polycystic ovarian syndrome (PCOS)?

the ovaries & adrenal glands produce and release a higher-than-normal amount of testosterone

• ovaries have multiple cysts

• ovulation does not occur regularly at all=fertility issues

• cause is unknown but maybe genetics or lifestyle?

is there a cure or treatment for PCOS?

no cure but treatment is to change diet/exercise, medications to stimulate ovulation, birth control

many people with PCOS…

have insulin resistance leading to increased insulin production

what do the uterine tubes/fallopian tubes receive?

receive ovulated oocyte from ovary and is the site of fertilization