Chapter 27: Reproductive System

function of the male reproductive system

make gametes & deliver them to the female reproductive tract

function of the female reproductive system

make gametes, receive gametes from male, & support development of a child

primary sex organs

make gametes & secrete sex hormones

male primary sex organs

testes

female primary sex organs

ovaries

accessory sex organs

ducts, glands, & external genitalia

pathway of sperm

made in testes → travel through epididymis → ductus deferns → ejaculatory duct → & urethra which opens to outside of the body at tip of penis

function of the scrotum

testes must be outside of body to keep sperm ~3°C cooler than core body temperature & in the cold testes are pulled in closer to the body by two muscles

2 muscles that move the testes

dartos muscle & cremaster muscles

dartos muscle

wrinkles scrotal skin making sac smaller

cremaster muscle

raise testes

external anatomy of testes

~1.5” by 1” & covered by 2 tunics

tunica vaginalis (testes)

outer layer derived from peritoneum

tunica albuginea (testes)

inner fibrous capsule & gives rise to septa

internal anatomy of testes

divided into lobules by septa, lobules have seminiferous tubules where sperm are made, from seminiferous tubules sperm move through tubules to epididymis, & between seminiferous tubules are interstitial cells or Leydig cells (make testosterone)

anatomy of penis

3 regions & prepuce or foreskin

3 regions of the penis

root, shaft, & glans penis (enlarged tip)

prepuce or foreskin

covers tip of penis unless removed (circumcision)

internal penile anatomy

contains spongy urethra & 3 bodies of erectile tissue

3 bodies of erectile tissue

continuous spongiosum & 2 corpora cavernosa

male duct system

epididymis, ductus deferens, & urethra

epididymis (male)

sperm mature here for ~20 days; once matured sperm are stored for up to several months or until needed

ductus deferens (male)

carries sperm from epididymis into body, after is loops over ureter it joins with seminal vesicle & forms ejaculatory duct

urethra (male)

carries urine & semen

3 regions

urethra (male)

carries urine & semen

3 regions

prostatic urethra (male)

within prostate

membranous urethra (male)

in urogenital diaphragm

spongy (penile) urethra

runs the length of the penis

male accessory glands

seminal vesicles, prostate, & bulbourethal glands

seminal vesicles

secretions contain fructose (sugar), ascorbic acid (vitamin C), a coagulating enzyme, and prostaglandins; these secretions are about 60% of semen volume

prostate gland

surrounds urethra, secretions contain citrate (energy source), several enzymes, & prostate (specific antigen (PSA)); these secretions are about 33% of semen volume

bulbourethral glands

located under prostate gland & secretions are released before ejaculation to neutralize traces of urine in urethra

contents of semen

sperm & seminal plasma

semen

milky white, sticky mixture of sperm & accessory gland secretions

what provides a transport medium and nutrients (fructose and citrate), protects and activates sperm, and facilitates their movement?

semen

prostaglandins (from seminal vesicles) in semen

decrease viscosity of mucus in cervix, & stimulate reverse peristalsis in ureters; both actions facilitate movement of sperm through female reproductive tract

relative alkalinity of semen

pH of 7.3-7.6 neutralizes acid environment found in male urethra and female vagina

clotting factors & semen

coagulate semen immediately after ejaculation, then fibrinolysin liquifies the sticky mass

ejaculation & semen

only 2-5mL of semen are ejaculated, but it contains 50-130 million sperm/mL

erection

enlargement & stiffening of penis from engorgement of erectile tissue with blood

parasympathetic reflex & sexual arousal

promotes nitric oxide release during erection (nitric oxide makes blood vessels dilate & erectile tissue fills with blood)

expansion of corpora cavernosa (male)

compression drainage veins & retards blow outflow & maintain engorgement

corpus spongiosum (erection)

keeps urethra open during ejaculation

erection is initiated by sexual stimuli including:

touch & mechanical stimulation of penis, erotic sights, sounds, & smells

erection can be induced or inhibited solely by:

emotion or higher mental activity

impotence

inability to attain erection

ejaculation

propulsion of semen from male duct system

at ejaculation, sympathetic nerves serving genital organs cause:

reproductive ducts & accessory organs to contract & empty their contents, bladder sphincter muscle to constrict preventing expulsion or urine, & bulbospongiosus muscles to undergo rapid series of contractions causing propulsion of semen from urethra

spermatogenesis

sequence of events that produces sperm in the seminiferous tubules of testes

cells making up walls of seminiferous tubules are in various stages of cell division. these spermatogenic cells give rise to sperm in what series of events?

mitosis of spermatogonia (forming spermatocytes), meosis forms spermatids from soermatocytes, & spermiogenesis (spermatids from sperm)

mitosis of spermatogonia

spermatogenesis begins at puberty as each mitotic division of spermatogonia results in type A or type B daughter cells

type A cells (mitosis of spermatogonia)

remain at basement membrane & maintain germ line

type B cells (mitosis of spermatogonia)

move toward lumen & become primary spermatocytes

spermatocytes to spermatids: primary spermatocytes

undergo meiosis I, forming 2 haploid cells called secondary spermatocytes

spermatocytes to spermatids: secondary spermatocytes

undergo meiosis II & their daughter cells are called spermatids

spermatids

small raw cells seen close to lumen of tubule

spermiogenesis: spermatids to sperm

late in spermiogensis, spermatids are haploid but nonmotile

spermiogenesis

spermatids lose excess cytoplasm and form a tail, becoming sperm

3 major regions of sperm

head, midpiece, & tail

head of sperm

contains DNA & has helmet like acrosome containing enzymes that allow the sperm to penetrate & enter the egg

midpiece of sperm

contains mitochondria that make ATP to power swimming

tail of sperm

flagellum

brain-testicular axis

hormonal regulation of spermatogenesis & testicular androgen production involving hypothalamus, anterior pituitary gland, & testes

hormonal regulation of testicular function

hypothalamus releases gonadotropin releasing hormone (GnRH), GnRH stimulates anterior pituitary to secrete follicle stimulating hormone (FSH) & luteneizing hormone (LH), FSH causes sustentacular cells to release androgen-binding protein (ABP), LH stimulates interstitial cells to release testosterone, & ABP binding of testosterone enhances spermatogenesis

testosterone activity

synthesized from cholesterol & targets all accessory organs & its deficiency causes these organs to atrophy

male secondary sex characteristics

male hormones appear at puberty & induce changes in non-reproductive organs

changes caused by non-reproductive organs when male hormones appear during puberty

pubic, axillary, & facial hair, enhanced growth of chest & deepening of voice, skin gets thick & oily, bones grow & get denser, skeletal muscles increase in size & mass

basis of libido in males & females

testosterone

ovaries

primary female reproductive organs; make female gametes (ova) & secrete female sex hormones (estrogen & progesterone)

accessory ducts (female reproductive system)

uterine tubes, ureters, & vagina

internal genitalia (female reproductive system)

ovaries & internal ducts

external genitalia (female reproductive system)

external sex organs

structure of ovaries

paired by organs on each side of the ureters & held in place by several ligaments (ovarian, suspensory, & mesovarium)

broad ligament of ovaries

contains suspensory ligament & mesovarium

ovaries are surrounded by

fibrous tunica albuginea

ovarian follicles

embedded in ovary cortex

oocyte

immature egg that each follicle consists of

cells around oocyte

follicle cells (1 cell layer thick) & granulosa cells (more than 1 layer present)

follicle stages

primordial follicle, primary follicle, secondary follicle, Graafian follicle, ovulation, corpus luteum

primordial follicle

1 layer of squamouslike follicle cells surrounds the oocyte

primary follicle

2 or more layers of cuboidal granulosa cells enclose the oocyte

secondary follicle

has a fluid-filled space between granulosa cells that coalesces to form central antrum

Graafian follicle

secondary follicle at its most mature stage that bulges from the surface of the ovary

ovulation

ejection of the oocyte from the ripening follicle

corpus luteum

ruptured follicle after ovulation

uterine tubes (fallopian tubes) & oviducts

receive ovulated oocyte & provide a site for fertilization, empty into the superolateral region of the uterus via the isthmus, expand distally around the ovary forming the ampulla, the ampulla ends in the funnel-shaped cilated infundibulum containing finger like projections called fimbriae