ADVANCED PHYSIOLOGY REPRODUCTION Instructor Terry Wiseth.

ADVANCED PHYSIOLOGY

REPRODUCTION

Instructor Terry Wiseth

Male System

Testespaired oval bodiesabout 1.5 in long

Tunica Albuginea

Outer coveringwhite fibrous

connective tissue

Tunica Vaginalis

Inner coveringvisceral peritoneum

Testes Development

Develop in the abdominal cavity

descend through the inguinal canal into the scrotum before birth

lower temperature necessary for spermatogenesis

TemperatureNormal body

temperature is too hot thus is lethal to spermso the testes are

outside of the abdominal cavity

where the temperature is about 2° C (3.6° F) lower

Temperaturea woman’s body

temperature is lowest around the time of ovulationto help insure sperm

live longer to reach the egg

If a man takes too many long, very hot bathssperm count can be

reduced

Scrotal Sac

Divided into lobulescontaining coiled

seminiferous tubulesempty into a central

network of tubules called the rete testis

Cellular Components

Interstitial CellsSertoli Cells

Interstitial Cells

Leydig Cellslie between seminiferous tubules Secrete testosterone

Sertoli Cells

in lower epithelial layers within seminiferous tubules

Form blood-testes barriercells joined by tight junctions

Sertoli Cells

Supply nutrients to spermatids Secrete inhibin

depresses FSH production Secrete androgen-binding protein (ABP)

concentrates androgens in tubules Secrete Müllerian-inhibiting factor (MIF)

involved in testes descent

Spermatogenesis

production of spermrequires 9 weeks

Spermatogonia

2N stem cells form basal layer of the seminiferous tubule

Separated by blood-testis barrier from spermatocytes which contain different membrane antigens

Mitotically divide toform primaryspermatocytes

Primary Spermatocytes

1N cells Undergo meiosis I

(reduction division) to form two haploid secondary spermatocytes

Secondary Spermatocytes

1N cells Complete meiosis II to form

four haploid spermatids connected by cytoplasmic bridges

Spermatids

1N Undergo structural change

(spermiogenesis) to form spermatozoa

Sperm1N Head contains nucleus and

acrosomal cap containing enzymes

Midpiece contains two centrioles + microtubules, mitochondrial spiral

Tail contains flagellum surrounded by fibrous sheath

Spermatogenesis

Epididymis

long coiled tubeabout 18-20 ft longComposed of head, body and tail Receives sperm from the rete testis

Epididymis Functions

Sperm storage and maturation

Recycles damaged sperm

Prevents premature capacitation

Ductus Deferens

vas deferenstube continuous

with the epididymisCarries sperm to

the seminal vesicle from the testes

Vasectomy

involves making a small slit in each scrotum

cutting the vas deferensnear where they begin

tying off the cut ends toprevent sperm fromleaving the scrotum

not designed to be areversible operation

Vasectomy

Spermatic Cord

composed of:ductus deferenstesticular artery

testicular veinlymphaticsnerves wrapped

with connective tissue

Spermatic Cord

extends from testes to the deep inguinal ring

In abdominal cavity the ductus deferens curves posterior to the bladder

Expands to form the ampulla and joins the duct of the seminal vesicle

Seminal Vesicles

pouch-like glands that empty into the ductus deferens at the ejaculatory duct

Secrete viscous alkaline fluid that constitutes about 60% of semen

Seminal Fluid

Fluid contains: Fructose

for ATP production for sperm Alkaline

Neutralizesacid in femalereproductivesystem

Seminal Fluid Fluid contains:

ProstaglandinsIncreases sperm motility and viabilitydecrease mucous viscosity at cervixstimulate female uterine contractions to

move the semen up into the uterusSemenogelin

causes spermcoagulation afterejaculation

Capacitation

Sperm become motile when mixed with seminal fluid

Secretions of female tract make sperm capable of fertilization

Ejaculatory Duct

short duct extends from the ductus deferens to urethra

Prostate Gland

large gland surrounds prostatic urethra and ejaculatory ducts

Secretes thin white slightly acidic fluidabout 25% of semen

Prostate Enlargement

The prostate needs a lot of zinc to function properly

insufficient dietary zinc can lead to enlargementpotentially can

constrict the urethra to the point of interfering with urination

Prostate Surgery

Mild cases of prostate hypertrophy can often be treated by adding supplemental zinc to the man’s diet

severe cases require surgical removal of portions of the prostate if not done very carefully

can lead to problems with urination or sexual performance

Prostate Fluid Fluid contains:

Citratefor ATP production in Kreb's cycle

Proteolytic enzymesliquefy coagulated semen after

15-20 minutes in vagina Acid phosphatase

function unknown Seminal plasmin

antibiotic, destroys bacteria

Prostate Fluid

Prostate secretions are alkaline to buffer:residual urine which tends to be

acidicthe acidity of the

woman’s vagina

Bulbourethral Glands

Cowper's glandpea-sizeposterior and lateral to membranous

urethra

Bulbourethral Fluid

bulbourethral fluid is secreted just before emission of the semen

alkaline mucoidneutralizes acidcoats and lubricates

urethra prior tosemen passage

Urethra

conducts urine or sperm away from the body

Urethra leads the length of the penis

Penis

3 cylindrical columns of erectile tissueIn relaxed state the central arteries are

constricted reducing inflow

Penis

In excited state the central arteries dilate (PNS)

blood fills the vascular channels causing an erection and compresses the veins reducingvenous outflow

Arousal

arteries become filled with blood from the arteries that supply them and the pressure seals off the veins that drain these areas causing an erectionnecessary for insertion of the penis

into the woman’s vagina

Glans Penis

The head of the penisvery sensitive to stimulationcovered by the foreskin or prepuce

Circumcision

Removal of prepuceMedically, circumcision is not a

necessityrather a cultural “tradition”

Circumcision

Males who have not been circumcised need to keep the area between the glans and the prepuce clean

Prevents microorganism growth on accumulated secretions

Circumcision

evidence that uncircumcised males who do not keep the glans/prepuce area cleanslightly more prone to penile cancer

Ejaculation

Ejaculation is a sympathetic reflex causing peristaltic wavesextending from the ductus deferens to

the penisthe bladder sphincter

is closed

Male Sexual Development

GeneticXX chromosomes are femaleXY are male, male determines

offspring sex in humans


Before 6 weeks gonadal development is same for male and female

At 6-7 weeks the SRY gene becomes activeSex-determining Region of Y-

chromosome


interstitial cells form and secrete testosteronecauses the gonads

to differentiate intotestes and formprimary sexualcharacteristics

Testosterone

Affects brain development

Sexual behaviorSexual drive

Testosterone

If no testosterone is secreted the gonads form ovariesfemale is default

Puberty

At puberty hypothalamus secretes GnRHstimulates the anterior pituitary to secrete

FSHwhich stimulates the seminiferous tubule

to develop and sperm production to occur

Puberty

The anterior pituitary releases LHwhich

stimulates interstitial cells to secrete testosterone

Testosterone

promotes skeletal and muscular growthincreases BMR 5-10%responsible for secondary sexual

characteristicshair, voice, muscle

essential for spermproduction

Female Reproductive System

Female System

OvariesAbout 2 inches

long

Ovaries

Medullacentral portion containing loose connective

tissue, vessels and nerves

Ovaries

Cortexdense connective tissue and ovarian

follicles

Ovaries

Tunica albugineawhite fibrous connective tissue layer outer surface layer of simple cuboidal

epithelium

Oviducts

Also called Fallopian tubesabout 4 inches long Extends from ovary to uterus

Infundibulum

fimbriated mouthnear but not in direct contact with ovaryproduces local currents that sweep the

ovulated oocyte into the uterine tube

Oviduct Mucosa

inner layer of ciliated columnar epithelium and secretory cells with microvilli

Oviduct Muscularis

3 layers of smooth muscleproduces peristaltic action that carries ova

Uterus

thick, muscular wallsThe lining of the uterus is called the

endometrium

Uterus

has a rich capillary supply to bring food to any embryo that might implant there

Fundus

portion above the uterine tube entrance

Body

tapering central portion

Cervix

The bottom end of the uterus is called the cervix

Cervix

The cervix secretes mucus, the consistency of which varies with the stages in the menstrual cycle

Cervical Mucous

At ovulationthis cervical mucus is clear, runny, and

conducive to spermPost-ovulation

the mucus getsthick and pastyto block sperm

Cervical Mucous

If a woman becomes pregnantthe cervical mucus

forms a plug to seal off the uterus and protect the developing baby

Cervical Mucous

removal of cervical plug carries the risk of introducing pathogens into the nearly-sterile uterine environment

Myometrium

thick muscular wall containing 3 layers of smooth muscle

Myometrium

Contains arteries with radial branches to endometrium

Endometrium

inner glandular epithelium and underlying connective tissueStratum basalisStratum functionalis

Stratum Basalis

permanent layergives rise to stratum functionalis

each monthsupplied by branching arterioles

Stratum Functionalis

temporary layer lost each monthsupplied by arterioles branching from the

radial arteries

Vagina

thin-walled fibromuscular tube leading from the cervix to the external genitalia serves as a repository for spermserves as the birth canal

Vagina

Acidic environment that reduces microbial growthneutralized by

alkaline semen

Vagina

the openings of the vagina and urethra are susceptible to bacterial infectionsif fecal bacteria are wiped towards them

Vagina

parents who are toilet-training a toddler usually wipe her from back to frontthus “imprinting”

that sensation as feeling “right” to her

Vagina

little girls should be taught to wipe themselves from the front to the backhelp prevent vaginal

and bladder infections

Labia Minor

2 thin foldscover the separate

vaginal and urethral openings

unlike the male, the female has separate opening for the urinary tract and reproductive system

Clitoris

at the anterior end of labia minor

erectile tissue homologous to the penis change shape when a

female is sexually aroused

contains many nerve endings in a sensitive glans covered by a prepuce

Clitoris

This is the most sensitive point for female sexual stimulation

Some cultures do a procedure, similar to circumcisiona puberty ritual in teenage

girls in which the prepuce is cut

exposing the extremely-sensitive clitoris

Labia Major

2 outer thicker folds covered by pubic hair

Hymen

a membrane that partially covers the opening of the vagina

This is torn by the woman’s first sexual intercourseor other causes like

injury or vigorous physical activity

Hormonal Regulationof Female System

Monthly Cycle

Female Sexual Development

When fetal gonads differentiate into ovaries the oogonia are formedthese are not true eggs, yet, and will never

complete meiosis and become such unless/until first fertilized by a sperm

Female Sexual Development

mitotic proliferation of the oogonia is complete well before birthAbout 2,000,000 oogonia per ovary

Only severalhundred ofthese “eggs”will actuallybe releasedduring awoman’sreproductiveyears

Puberty

By puberty the oogonia have developed into primary oocytes that undergo prophase I and are arrested

Virtually no sexual hormone activity between birth and puberty

Puberty

After puberty each month a group of primary oocytes are stimulated to reach metaphase II just prior to ovulation

If sperm penetration occurs meiosis is completed

Oogenesis

Production of active ovaoccurs monthly in ovarian cycle Primary oocyte is surrounded by a primordial

follicle which grows and matures each month

Oogenesis

Cytokinesis is unequal, secondary oocytes are haploid (1N)

Ovulation

after the onset of puberty, due to the stimulation of follicle-stimulating hormone (FSH) one “egg” per cycle matures and is released from its ovary

Follicle

a follicle consists of one precursor egg cell (oogonia) surrounded by special cells to nourish and protect it

Graffian Follicle

a follicle consists of one precursor egg cell (oogonia) surrounded by special cells to nourish and protect it

Ovulation

Ovulation is the release of a mature “egg” due to the stimulation of leutenizing hormone (LH)

Ovulation

Leutenizing hormone (LH)stimulates the remaining follicle cells to

turn into a corpus luteum

Ovulation

Corpus luteumsecretes progesterone to prepare the

uterus for possible implantation

Corpus Luteum

If an egg is not fertilized and does not implant, the corpus luteum disintegrates

when it stops producing progesterone, the lining of the uterus breaks down and is shed

Menstrual Cycle

Menstrual Cycle

Estrogen

Progesterone

Menstrual Cycle

EstrogenProgesterone

Oviducts

Each “egg” is released into the abdominal cavity near the opening of one of the oviducts or Fallopian tubes

Cilia in the oviduct set up currents that draw the egg in

Feritilization

If sperm are present in the oviduct the egg: will be fertilized near the far end of the

Fallopian tube

Feritilization

After fertilization the embryo will start to divide and grow as

it travels to the uterus

Oviduct

The trip down the Fallopian tube takes about a week as the cilia in the tube propel the unfertilized “egg” or the embryo down to the uterus

Progesterone

progesterone secreted by the corpus luteum has been stimulating the endometrium to thickenin preparation for possible implantation

Implantation

when a growing embryo reaches the uterusit will implant in the endometrium and begin to

secrete its own hormones to maintain the endometrium

Sloughing

If the “egg” was not fertilized

it dies and disintegratesas the corpus luteum

also disintegrates, its progesterone production falls, and the unneeded, built-up endometrium is shed

Hormonal Regulation of

Monthly Ovarian Cycle Day 1 Rising levels of GnRH stimulate release of FSH and production of LH by anterior pituitary

FSH stimulates proliferation of granulosa cells and the follicle grows Granulosa cells secrete follicular fluid producing small fluid-filled cavities which merge to form the fluid-filled antrum Increasing numbers of granulosa cells release estrogens and inhibin

6-8 Inhibin and estrogen decrease GnRH release and FSH releaseHigher levels of estrogen stimulate production and release of LH (positive feedback) LH accelerates growth and maturation of follicle (1 dominant ovum)

12-14 While follicle migrates to ovarian surface, estrogen level increases sharply causing a surge of LH and 1 follicle ruptures and releases ovum. Other follicles degenerate forming atretic follicles. Estrogen levels fall.

15 LH levels are elevated for 2 days, cause follicle cells to be filled with lipid and yellow pigment (luteinized) forming a corpus luteum. The corpus luteum secretes progesterones and estrogens which inhibit the hypothalamus production of GnRH and decrease FSH and LH levels

26 Corpus luteum degenerates and forms the corpus albicans if there is no pregnancy. Decreasing levels of progesterone and estrogen result in renewed production of GnRH


Monthly Ovarian Cycle Day 1 Rising levels of GnRH stimulate release of

FSH and production of LH by anterior pituitary FSH stimulates proliferation of granulosa cells and the follicle grows Granulosa cells secrete follicular fluid producing small fluid-filled cavities which merge to form the fluid-filled antrum Increasing numbers of granulosa cells release estrogens and inhibin


Monthly Ovarian Cycle

Day 6-8 Inhibin and estrogen decrease GnRH release and FSH release

Higher levels of estrogen stimulate production and release of LH (positive feedback) LH accelerates growth and maturation of follicle (1 dominant ovum)



Day 12-14 While follicle migrates to ovarian surface, estrogen level increases sharply causing a surge of LH and 1 follicle ruptures and releases ovum

Other follicles degenerate forming atretic follicles

Estrogen levels fall



Day 15 LH levels are elevated for 2 days

Cause follicle cells to be filled with lipid and yellow pigment (luteinized) forming a corpus luteum

The corpus luteum secretes progesterones and estrogens which inhibit the hypothalamus production of GnRH and decrease FSH and LH levels


Monthly Ovarian Cycle Day 26 Corpus luteum degenerates and forms

the corpus albicans if there is no pregnancy

Decreasing levels of progesterone and estrogen result in renewed production of GnRH

Uterine Cycle

Day 1 Menses: degeneration and loss of the functional layer. Decrease in progesterones and estrogens stimulates the release of prostaglandins which cause the spiral arterioles to constrict. O2 and nutrient deprivation causes endometrial necrosis,

desquamation and bleeding. Only the stratum basalis remains.

5-14 Proliferation: restoration of the functional layer. Follicular cells secrete increasing amounts of estrogen. Stratum basalis cells proliferate producing the s. functionalis. Short straight endometrial glands form, spiral arterioles regrow.

15-26 Secretion: increased growth and secretion prepares uterus for implantation. Levels of progesterones and estrogens produced by the corpus luteum increase. Glands enlarge, coil into corkscrew shapes and secrete glycogen. Vascularization of the s. functionalis increases.

26-28 If fertilization does not occur, the corpus luteum degenerates and progesterone and estrogen levels decline.

Uterine Cycle

Day 1 Menses: degeneration and loss of the functional layer

Decrease in progesterones and estrogens stimulates the release of prostaglandins which cause the spiral arterioles to constrict

O2 and nutrient deprivation causes endometrial

necrosis, desquamation and bleeding

Only the stratum basalis remains

Uterine Cycle

Day5-14

Proliferation: restoration of the functional layer

Follicular cells secrete increasing amounts of estrogen

Stratum basalis cells proliferate producing the s. functionalis

Short straight endometrial glands form, spiral arterioles regrow

Uterine Cycle

Day15-26

Secretion: increased growth and secretion prepares uterus for implantation

Levels of progesterones and estrogens produced by the corpus luteum increase

Glands enlarge, coil into corkscrew shapes and secrete glycogen

Vascularization of the stratum functionalis increases

Uterine Cycle

Day26-28

If fertilization does not occur, the corpus luteum degenerates and progesterone and estrogen levels decline

EndReproduction

ADVANCED PHYSIOLOGY REPRODUCTION Instructor Terry Wiseth.

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