Reproductive system functions in gamete Production Storage Nourishment Transport

Fertilization Fusion of male and female gametes to

form a zygote

Cellular Reproduction

Mitosis – exact duplication of genetic material to produce daughter cells which are genetically identical to parent cell.

Mitosis produces all the somatic cells of the body (non-gametes),

Diploid Cell – 46 Chromosomes

Gametes (sperm and eggs).

Sexual ReproductionMeiosis – division which reduces the

number of chromosomes to produce haploid (half the number of chromosomes) gametes.

Two division phases: produces 4 sperm in males and 1 egg in females

Crossover magnifies the genetic variability.

MALE REPRODUCTIVE SYSTEM

COMPONENTS testes: produce spermatozoa (male

reproductive cells) and androgens (male hormones)

ducts: epididymis, vas (ductus) deferens, urethra (prostatic, membranous, spongy)

accessory glands: prostate, seminal vesicles, bulbourethral (Cowper’s)

supporting structures: scrotum, penis

Figure 28.1

Figure 28.3

DEVELOPMENT testes develop inside the

abdominal cavity; descend and exit via the inguinal canals prior to birth

need to exit the abdominal cavity due to high temperature that prevents sperm formation

failure to descend: cryptorchidism, causes sterility

high temperature causes infertility; pampiniform plexus of testicular vein cools testis

LOCATION AFTER BIRTH

located in the scrotum (sac attached to the perineum)

cradled by cremaster muscle (extension of the internal oblique muscle)

connected via spermatic cord: made of testicular artery and vein, vas deferens, nerves

TESTICULAR STRUCTURE

fibrous tunica albuginea covers the outside; inward extensions, called septa, create lobules within the testes

seminiferous tubules within the lobules produce spermatozoa (s. spermatozoon)

interstitial cells of Leydig are found in the spaces between the seminiferous tubules

Figure 28.4

Seminiferous tubules

Contain spermatogonia Stem cells involved in spermatogenesis

Contain sustentacular cells Sustain and promote development of sperm

Figure 28.5a, b

Figure 28.5c

SPERMATOGENESIS

process of sperm formation-spermatogonium - primary

spermatocyte (first meiotic division) -two secondary spermatocytes (second

meiotic division) -four spermatids - four spermatozoa

Spermiogenesis: the process of differentiation of spermatids into spermatozoa

Figure 28.8

PATH FOLLOWED BY SPERMATOZOA1. produced by cells inside the walls of the seminiferous

tubules 2. move outside the testis in the epididymis (very long,

thin, highly coiled tube) where they complete maturation in a few days

3. expelled into the vas deferens during ejaculation 4. travel out of scrotum via the inguinal canal into the

pelvic cavity to the posterior side of the urinary bladder 5. joined by secretions via duct from the seminal vesicle 6. pass through prostate gland via ejaculatory duct which

opens in the prostatic urethra (are joined by prostatic secretions)

7. now part of semen pass through the membranous urethra

8. then spongy urethra (joined by secretions of bulbourethral glands)

9. exit through the urethral meatus 10. then through the urethral orifice to the outside.

Figure 28.9

PRODUCTION OF ANDROGENS (MAINLY TESTOSTERONE)testosterone is produced by the interstitial cells of

Leydigtestosterone production, almost nil before puberty, increases dramatically at puberty

Some of the functions of testosterone:- activates anabolic processes -prior to birth, and after, controls development of male sexual structures- controls behavior in both sexes- supports sperm formation- controls development of male secondary sex characteristics:

- widening of shoulders- increased musculature- growth of facial hair, pubic and axillary

hair- enlargement of larynx and vocal cords

FSH (Follicle stimulating hormone) Targets sustentacular cells to promote

spermatogenesis LH (leutinizing hormone)

Causes secretion of testosterone and other androgens

GnRH (Gonadotropin releasing hormone) Testosterone

Most important androgen

Figure 28.12

ACCESSORY GLANDS

Seminal Vesicles:- located on the posterior surface of the urinary bladder adjacent to the ampulla of the ductus deferens-elongated, pouch-like hollow organ approximately 5-8cm long-proximal end merges with the ductus deferens to form the ejaculatory duct-secrete a viscous, whitish-yellow alkaline fluid containing both fructose and prostaglandins-fructose nourishes the sperm as they travel through the female reproductive tract-prostaglandins promote the widening and slight dilation of the external orifice of the cervix

Prostate Gland-compact encapsulated organ that weighs about 20g and is shaped like a walnut, measuring approximately 2x3x4cm-located immediately inferior to the bladder-secretes a slightly milky fluid that is weakly

acidic and rich in citric acid, seminalplasmin, and prostate-specific antigen (PSA)

-citric acid is nutrient for sperm health

-seminalplasmin is an antobiotic that combats urinary tract infections-PSA acts as an enzyme to help liquefy

semen following ejaculation

Bulbourethral Glands (Cowper’s gland)

-paired, pea-shaped, located within the urogenital diaphragm on each side of the

memranous urethra-each gland has a short duct that projects into the base of the penis and enters the spongy urethra-secretes a clear, viscous mucin that forms

mucus when mixed with water-mucin protects the urethra and serves as a lubricant during sexual intercourse

Figure 28.10a-e

STRUCTURE OF PENIS

corpus spongiosum around the urethra

two corpora cavernosa on dorsal side

glans penis: enlargement at distal end covered by prepuce (skin fold)

Figure 28.11

Erection: filling the corpora cavernosa and corpus spongiosum with blood by increased blood flow in the supply arterioles and decreased drainage through the venules.

Controlled by parasympathetic system.

Ejaculation: peristaltic contractions in the walls of ducts (epididymis, vas deferens) propelspermatozoa and contractions of smooth muscle fibers in the walls of accessory glands squeezeout secretions.

Controlled by sympathetic system.

Infertility: < 20,000,000 spermatozoa/ml (normal 20,000,000 - 50,000,000)

Primary sex organs called gonads-Ovaries in females-Testes in males

Produce gametes which unite to form a new Produce gametes which unite to form a new individualindividual

-Oocytes-Oocytes-Sperm-SpermGonads produce large amounts of sex hormones

which affect maturation, development, and changes in the activity of the reproductive system organs.

-estrogen and progesterone in females

-androgens in the male

1. Primarily nonfunctional and dormant until puberty.

2. At puberty, external sex characteristics become more prominent.

1. Breast development in females2. Pubic hair in both sexes3. Reproductive organs becomes fully functional4. Gametes mature5. Gonads secrete sex hormones

3. Both reproductive systems produce gametes

4. Female typically produces and releases a single oocyte monthly.

5. Male produces 100,000,000’s of sperm daily.-Male gametes are stored for a short

time.-If they are not expelled from the body within that period, they are reabsorbed.

Reproductive System HomologousReproductive System Homologous

Female Female OrgansOrgans

Male organ Male organ homologoushomologous

Common FunctionsCommon Functions

OvaryOvary TestisTestis Produce gametes and sex Produce gametes and sex hormoneshormones

ClitorisClitoris Glans of Glans of PenisPenis

Contains autonomic Contains autonomic nervous system axons that nervous system axons that stimulate arousal and stimulate arousal and sexual climax feelingssexual climax feelings

Labia majoraLabia majora ScrotumScrotum Protect and cover some Protect and cover some reproductive structuresreproductive structures

Vestibular Vestibular glandsglands

BulbourethraBulbourethral glandsl glands

Secretes mucus for Secretes mucus for lubricationlubrication

1. Diamond shaped area between the thighs that is circumscribed anteriorly by the pubic symphysis, laterally by the ischial tuberosities, and posteriorly by the coccyx.

2. 2 distinct triangle bases are formed by an imaginary horizontal line extending between the ischial tuberosities of the ossa coxae.

3. Anterior triangle, called the urogenital triangle, contains the urethral and vaginal orifices in females and the base of the penis and the scrotum in males.

4. Posterior triangle, called the anal triangle, is the location of the anus in both sexes.

COMPONENTS

ovaries: produce precursors of ova (female reproductive cells )

Fallopian tubes (uterine tubes, oviducts): carry female reproductive cells/zygote/mass of embryonic cells toward uterus

uterus: holds, nourishes and protects developing embryo/fetus

vagina: tubular structure connecting the uterus to the outside

vulva (pudendum): external genitalia

Figure 28.13

OVARIES

almond sized and shaped, located against the lateral walls of the upper pelvic cavity

supporting ligaments:- suspensory ligament: between

ovary and lateral wall of pelvic cavity- ovarian ligament: between ovary

and fundus of uterus- part of the sheet-like broad

ligament (mesovarium)

Figure 28.14a, b

OVARIAN STRUCTURE covered by germinal epithelium: layer of simple cuboidal

epithelium surrounded by fibrous tunica albuginea (same as testes) two regions:

- outer cortex- inner medulla

- ovarian follicles are found in the cortex:- follicle: central cell called oocyte surrounded by supporting

granulosa cells- types of follicles (based on developmental stage):

- primordial: primary oocyte surrounded by one layer of squamous cells

- primary: primary oocyte surrounded by one layer of cuboidal cells

- secondary: primary oocyte surrounded by two or more

layers of cells- Graafian: very large with fluid filled space in the

center; secondary oocyte pushed at the edge

OOGENESIS

Prior to birth- oogonia multiply mitotically (about 3/4

million)- oogonia - become primary oocytes - start

first meiotic div., stop at prophase

Primordial follicles - Primary follicles

Birth- female is born with ~ 3/4million primary

follicles containing primary oocytes that have started the first meiotic division but have stopped at the prophase

OOGENESISPuberty- each month ~24 follicles get activated, one

survives (most follicles die by atresia); the primary oocyte completes the first meiotic division

- primary oocyte - secondary oocyte (and tiny, first polar body) - second meiotic div. starts but stops at metaphase

Primary follicle - Secondary follicle - Graafian follicle

- Graafian follicle ruptures at ovulation releasing the secondary oocyte in the pelvic cavity; the secondary oocyte is directed inside the Fallopian tube by the fimbriae and moves toward the uterus.

OOGENESISPossible outcomes:- secondary oocyte is contacted by spermatozoa:

the oocyte is activated and completes the second meiotic division forming an ovum (and a tiny, second polar body); the ovum and one of the spermatozoa unite (fertilization) to form the zygote (first cell of the new organism). The zygote starts to divide right away and by the time it reaches the uterine cavity it is a mass of cells that undergo implantation (attach to the uterine wall)

- secondary oocyte does not come in contact with spermatozoa: it will disintegrate on its way to the uterus

FALLOPIAN TUBES (UTERINE TUBES, OVIDUCTS)

- have fimbriae (finger-like) surrounding funnel shaped opening next to the ovary

- attach to the fundus of the uterus

UTERUS

Muscular organ Mechanical protection Nutritional support Waste removal for the developing embryo

and fetus Supported by the broad ligament and 3

pairs of suspensory ligaments

UTERUSParts:- fundus (bottom): back (deep, proximal) part- corpus (body): central part- cervix (neck): end part that attaches to the

vaginaWall structure:- perimetrium: thin outer layer- myometrium: thick, middle muscular layer- endometrium: thin inner lining

- has two layers:- endometrium basalis: permanent,

against the myometrium- endometrium functionalis: shed

during menstruation; faces the uterine cavity

Figure 28.19b

UTERUS

Supporting ligaments:- part of sheet-like broad ligament (mesometrium)- round ligament- cardinal ligaments: lateral, main support- utero-sacral ligamentBlood supply:- uterine arteries branch from the internal iliac

arteries- the endometrium basalis is penetrated by

straight arterioles - from the straight arterioles branch spiral

arterioles that enter the endometrium functionalis; the spiral arterioles break during menstruation causing bleeding

HORMONAL FACTORS THAT CONTROL THE MENSTRUAL CYCLE:Follicle stimulating hormone (FSH): -starting at puberty, activates a couple of dozens of

primary follicles each month causing them to continue development

Luteinizing hormone (LH): -triggers ovulation and, following that, it maintains

the corpus luteum

Progesterone:- when at high levels in the blood, together with

estrogen, inhibits the release of gonadotropic hormones by the pituitary gland and prevents the start of a new menstrual cycle

- maintains the endometrium functionalis and prevents its shedding

HORMONAL FACTORS THAT CONTROL THE MENSTRUAL CYCLE:

Estrogen:- promotes tissue growth- activates osteoblasts- promotes the development of the female secondary

sex characteristics:- distribution of adipose tissue on the body with:

- enlargement of the breasts- widening of the hips

- distribution of hair: axillary and pubic hair- when at high levels in the blood, together with

progesterone, inhibits the release of gonadotropic hormones by the pituitary gland and prevents the start of a new menstrual cycle

Figure 28.25

MENSTRUAL CYCLE: CONSISTS OF TWO CYCLESuterine cycle: - a series of monthly changes in the wall of the uterus

of a nonpregnant female that prepare the endometrium functionalis for implantation

- if there is no implantation, the shedding of the endometrium functionalis

ovarian cycle: - monthly activation and the continued development

into secondary follicles of about two dozens ovarian follicles, usually with only one surviving, completing development into a Graafian follicle and then rupturing releasing a secondary oocyte in the pelvic cavity.

Figure 28.26a-c

Figure 28.26d-f

Animation: Regulation of the Female Reproductive CyclePLAY

PHASES OF THE MENSTRUAL CYCLE

Menstrual phase: - last about 5 days

- uterine cycle: - small patches of the endometrium functionalis get sloughed off from the uterine wall, one a time,

with spiral arterioles rupturing and causing bleeding.

- By the end of the fifth day only a thin, smooth layer of endometrium, the endometrium basalis, is left.

- ovarian cycle: - at this time the levels of progesterone and estrogen

in the blood are low allowing the pituitary to release follicle stimulating hormone (FSH). - The FSH activates over twenty four primary follicles in

the ovaries causing them to continue development. All but one follicle fail to complete development, undergo atresia, with the surviving follicle acquiring additional layers of supporting cells thus becoming a secondary follicle.

Preovulatory (postmenstrual) phase: - variable in length; lasts from day 5 to about day 13

- uterine cycle: - a new endometrium functionalis starts to grow out of the basalis

layer.

- ovarian cycle: - the surviving follicle becomes a Graafian follicle. - The primary oocyte, within the follicle, completes the first meiotic division and produces two daughter cells, a tiny first polar body, which will be lost and a large secondary oocyte. - The secondary oocyte starts the second meiotic division but stops at metaphase. - Toward the end of this period there is a sudden increase in the

production of luteinizing hormone (LH) by the pituitary gland causing the Graafian follicle to complete its maturation and to rupture.

Ovulation: - occurs around day 14.

- The Graafian follicle ruptures releasing the secondary oocyte in the pelvic cavity.

- The secondary oocyte, in most instances, is directed inside the Fallopian tube (with help from the fimbriae) and starts traveling toward the uterus.

Postovulatory (premenstrual) phase:- ovarian cycle:

- under the influence of the luteinizing hormone (LH) the mass of tissue of the former Graafian follicle that remained in the ovary is transformed into a yellow body called the corpus luteum. - The corpus luteum starts producing large amounts of progesterone and estrogen causing their blood levels to increase dramatically.

- uterine cycle: - under the influence of progesterone the endometrium functionalis layer continues its

preparation for implantation: - becomes thicker and accumulates large

deposits of glycogen while numerous spiral arterioles grow into it from the endometrium basalis layer.

Postovulatory (premenstrual) phase:

- if the secondary oocyte, while traveling toward the uterus, is met and contacted by spermatozoa then it will complete the second meiotic division and will form a second polar body and an ovum (egg).

- Following fertilization the egg will form a zygote (first cell of the new organism), the zygote will start dividing mitotically right away and upon reaching the uterus the mass of cells will attach itself to the endometrium functionalis layer that lines the uterine cavity (implantation).

Postovulatory (premenstrual) phase:

-At the site of contact between the embryonic mass and the uterine wall a new structure, called the placenta, will start growing immediately.

-The placenta will start producing human chorionic gonadotropic hormone (HCGH) which mimics in its effects the luteinizing hormone.

-HCGH will maintain the corpus luteum functional allowing it to continue to produce large amounts of progesterone and estrogen for several months.

Postovulatory (premenstrual) phase cont…:

- The high levels of progesterone and estrogen in the blood will inhibit the pituitary gland preventing it from releasing gonadotropic hormones (FSH and LH) thus the production and following that the blood level of LH will decrease.

- However, since the HCGH is assuming the function of LH the corpus luteum will continue to function producing large amounts of progesterone and estrogen.

- The high levels of progesterone in the blood will maintain the endometrium functionalis layer in place preventing its shedding.

Postovulatory (premenstrual) phase:

-The lack of FSH production due to the inhibition of the pituitary prevents the start of a new ovarian cycle.

-The high levels of progesterone help maintain the endometrium functionalis layer thus preventing the start of a new uterine cycle.

-Thus, the high blood levels of progesterone and estrogen prevent the start of a new menstrual cycle during pregnancy.

-The corpus luteum stops functioning during the second half of pregnancy, at that time the production of estrogen and progesterone is taken over by the placenta.

Postovulatory (premenstrual) phase cont…:

- if the secondary oocyte is not met by spermatozoa it will soon disintegrate while traveling toward the uterus.

- The high levels of progesterone and estrogen in the blood will inhibit the pituitary gland and prevent the release of LH.

- Without LH the corpus luteum can not continue to function and it starts to degenerate.

- It stops producing the progesterone and estrogen, changes to a whitish color, it is now called the corpus albicans, and shrinks to a small scar that is left in the mass of the ovary.

Postovulatory (premenstrual) phase cont…:

-The levels of progesterone and estrogen in the blood decline with the following consequences:

- the endometrium functionalis layer can not be sustained, due to lack of progesterone, and

starts to shed one piece at a time: a new uterine cycle begins.

- the low blood levels of estrogen and progesterone allow the pituitary to become disinhibited and to start releasing FSH.

- The FSH activates a couple of dozens of ovarian follicle thus starting a new ovarian cycle.

- this way a new menstrual cycle begins.

Figure 28.20

- climacteric : period of irregular menstrual cycling that precedes menopause.

- menopause: complete cessation of menstrual cycles; associated with aging.

- amenorrhea: lack of menstrual cycles; often caused by insufficient adipose tissue in the body resulting from starvation or excessive physical exercise.

VAGINA- tubular structure that connects the uterus

to the outside.

- Attaches to the cervix of the uterus at the proximal end.

- Forms an attachment fold called the fornix.

- The vaginal mucosa has folds (rugae).

- The mucosa stores significant amounts of glycogen which, following processing, produces lactic acid.

- The lactic acid makes the vaginal environment acidic this way preventing the growth of pathogens.

- The acidic environment is inhospitable, however, to the spermatozoa and has to be neutralized by the alkaline semen.

- The distal end of the vagina opens, through the vaginal orifice in the vestibule of the vulva (pudendum).

VULVA (PUDENDUM): EXTERNAL FEMALE GENITALIA

Structure:- mons pubis (mons veneris):

- pad of adipose tissue located anterior to the symphysis pubis. - two pairs of folds:

- labia majora: lateral, large, filled with adipose tissue, covered with hair

- labia minora: medial, thin, hairless - clitoris:

- small, penis-like structure containing two corpora cavernosa, covered

by a prepuce-like skin fold.- Located at the anterior end of the labia minora. - The urethra does not pass through it and it has no corpus spongiosum.

- vestibule:- space bordered by the labia minora; its walls contain glands that produce lubricating secretions:

- many small, lesser vestibular glands - a couple of large, greater vestibular glands (Bartholin’s glands)

Figure 28.22

MAMMARY GLANDS

- located in the pectoral region superficial to the pectoralis major muscles.

- supported by strands of connective tissue called suspensory ligaments (Cooper’s ligaments; ‘Cooper’s droop’: sagging of the breasts due to stretching of the Cooper’s ligaments.

- made of 15 - 20 functional masses of milk producing tissue (lobes) separated by masses of adipose tissue.

- inside the lobes there are lobules that contain grape-like masses of secretory cells called alveoli which produce milk.

- the milk flows to wide ducts, lactiferous ducts (sinuses), where it is stored before release.

- the lactiferous ducts open through the papilla (nipple) to the outside; the papilla is surrounded by the areola, a dark, pigmented area.

Figure 28.23a-c

LACTATION

production and release of milk- milk production is controlled by the

hormone prolactin - milk release from the lactiferous ducts is controlled by the hormone oxytocin; - when there is tactile stimulation of the breast by the infant trying to feed, the stimulation causes the release of oxytocin from the neurohypophysis; -the oxytocin travels via the blood the walls of the lactiferous ducts causing their constriction thus expelling the milk (milk let down) from the breast.