Reproduction Chapter 21

1

Chapter 21Reproductive

System

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Reproduction

• Asexual reproduction

– One parent produces genetically identical

offspring

– Very rapid reproduction

– Can proceed via

– Budding

– Fission

– Fragmentation/regeneration

Reproduction

• Sexual reproduction involves thefusion of gametes from two parents

–Resulting in genetic variation amongoffspring

–Increased reproductive success inchanging environments

• Some organisms can reproduce

–Asexually or

–Sexually

Eggs

Human Reproduction

• Both sexes in humans have

– A set of gonads (testes or ovaries) where

gametes (sperm or eggs) are produced

– Ducts for gamete transport

– Structures for copulation

The Male Reproductive System

urinary bladder

vas deferens

pubic bone

urethra

penis

glans penis

foreskin

scrotum

seminal vesicle

ureter (cut)

ejaculatory duct

prostate gland

bulbourethral gland

anus

epididymis

testis

vas deferens

erectile tissue

of penis


21.1 Male Reproductive System

• Genital Tract

– Sperm are produced by seminiferous tubules of testes

– Undergo maturation in the epididymis

– Sperm pass through vas deferens where products are

secreted by glands that contribute to semen

• Seminal vesicles

• Prostate gland

• Bulbourethral gland

– Semen is alkaline and contains fructose

– Over 400 million sperm cells in one ejaculation

21.1 Male Reproductive System

• Male Gonads, the Testes

– Produce sperm and hormones

– Located outside of the body cavity in scrotum

• Internal body temperature is too high for sperm production

A Testis

• Spermatogenesis occurs

in the seminiferous

tubules

• Interstitial cells produce

testosterone

vas deferens

epididymis

testis

lobule

scrotal sac

uncoiled

seminiferous

tubule

a. Testis, cut to show lobules


A Sperm Cell

• Three Main Parts

– Head

• The acrosome contains

enzymes needed to

penetrate an egg

– Middle Piece

• Many mitochondria

– Tail

• Flagellum

acrosome

head

middle piece

tail

end piece

d.


140 !m

tails of sperm in lumen of seminiferous tubule

Sertoli cell

vas deferens

epididymis

testis

lobule

scrotal sac

MEIOSIS I MEIOSIS II

acrosome

head

middle piece

tail

end piece

b. Seminiferous tubules

c. Spermatogenesis d.

100 !m

uncoiled

seminiferous

tubule

MITOSIS

spermatogonium

(diploid)

primary

spermatocyte

secondary

spermatocyte

early

spermatid

late

spermatid

immature sperm

(haploid)

a. Testis, cut to show lobules

nucleus of

Sertoli cell


interstitial cell

b(top): © CNRI/Photo Researchers, Inc. b(bottom): © Ed Reschke

MEIOSIS I MEIOSIS IIMITOSIS

spermatogonium

(diploid)

primary

spermatocyte

secondary

spermatocyte

early

spermatid

late

spermatid

sperm

(haploid)

Spermatogenesis21.2 Female Reproductive System

vagina

uterus

ovaryoviduct


cervix

21.2 Female Reproductive System

oviduct

ovary

uterus

urinary bladder

pubic bone

urethra

glans clitoris

labium minora

labium majora

vaginal orifice

fimbriae

cervix

rectum

vagina

anus


21.2 Female Reproductive System

• Oogenesis

– production of an egg (oocyte)

– begins before birth—diploid cells start meiosis

and stop

– each month about one primary oocyte

resumes meiosis

– a secondary oocyte arrested at metaphase

of meiosis II is ovulated

– meiosis of the ovum is completed after

fertilization (in oviduct)

2n

2n

Differentiationand onset of

Meiosis I

Diploid cellin embryo

Firstpolar body

n

n

Completionof Meiosis I

and onset ofMeiosis II

n

n

Entry of spermtriggers completion

of Meiosis II

Secondpolar body

Ovum

(haploid) Sperm

Corpusluteum

Ovulation Ruptured follicle

Mature follicle

Growingfollicle

Ovary

(arrested in prophaseof Meiosis I; presentat birth)

Primary oocyte

Secondary oocyte

(arrested at meta-phase of Meiosis II;released from ovary)

Ovarian Cycle

Oogenesis Spermatogenesis

Primaryoocyte

Primaryspermatocyte2n 2n

n

nn n

nnnn

n

Secondaryspermatocyte

Secondaryoocyte

Polar body

Sperm

Once permonth

Fertilization

Polar body

ZygoteOvum 2nn

n

Hormonal Control of the Ovaries

• The hypothalamus,

anterior pituitary and

ovaries all function to

control female

hormone levels. Like

other hormones,

female hormones are

regulated by feedback

mechanisms.


LH

FSH

GnRH

oocyte

hypothalamus

anterior

pituitary

follicle

estrogen

corpus

luteum

progesterone

Ovarian and Uterine Cycles

FSH LH

1 3 5 7 9 11 13 15 17 19 21 23 25 27 1Days

Ovarian cycle ovulation

early

corpus luteum

regressing

corpus luteum

maturefollicledeveloping follicle

Follicular Phase Ovulation Luteal Phase

Ov

ari

an

Ev

en

tsH

orm

on

e

Le

ve

lsE

nd

om

etr

ium

1 3 5 7 9 11 13 15 17 19 21 23 25 27 30

Ho

rmo

ne

Le

ve

ls

Menstruation Proliferative Phase Secretory Phase

Days

ovulationUterine cycle

estrogen

menstruation

progesterone

21.3 Female Hormone Levels

• Menstruation

– Arteries that supply the endometrium (uterine lining)

constrict thereby weakening the capillaries

– The endometrium detaches in random patches

– Tissue, blood, and mucus are lost in the menstrual

flow

– Menstruation lasts 3!10 days


• Fertilization and Pregnancy

– An embryo begins development in the oviduct

– Implantation occurs when embryo migrates into uterus

– Embryo begins to produce human chorionic

gonadotropin (hCG)

• hCG maintains the corpus luteum to prevent a drop in levels

and estrogen and progesterone

• Pregnancy tests detect hCG

– Later, the placenta will secrete estrogen and

progesterone

– Estrogen and progesterone prevent ovulation and help

to maintain the endometrium

Implantation

oviduct

a.

ovary

embryo(not drawn

to scale)



• Estrogen and Progesterone

– Both have effects other than those in the ovarian and

uterine cycles

– Estrogen

• Maintains female secondary sex characteristics

– Breast development, axillary and pubic hair, subcutaneous fat

deposition

– Wider pelvis

– Progesterone

• Also needed for breast development


• Menopause

– Generally occurs between the ages of 45!55

– Ovaries become unresponsive to FSH and LH

– At the onset of menopause, the menstrual cycle

becomes irregular. Other characteristics include hot

flashes, dizziness, headaches, insomnia, and

depression.

– Menopause is complete when menstruation has not

occurred for one year

– Hormone replacement therapy has advantages and

disadvantages

21.5 Disorders of the Reproductive

System

• AIDS (Acquired Immunodeficiency Syndrome)– Caused by HIV (human immunodeficiency virus)

– Transmission

• Sexual Contact

• Intravenous drug use

• Birthing process

• Breast feeding

– Primary host cells are immune cells

– Patients are usually given multiple drugs

• Treatment, not a cure


System

• Genital Herpes– Two types of Herpes Simplex Virus

• Type 1: Colds sores and blisters (oral)

• Type 2: Genital herpes

– Symptoms• Tingling, itching occur first

• Then blisters appear (2!20 days later)

• Fever, painful urination, swollen lymph nodes

– Later, the virus lies dormant• May be reactivated by environmental factors

– Infection of newborn babies can occur with serioushealth issues


System

• Human Papillomaviruses (HPV)

– Cause genital warts

– Some HPV’s can cause cervical cancer

– Early detection of cervical cancer is possible

by means of a Pap smear

– No cure, treatments include removal of the

warts by freezing, burning, acids, or lasers

– A vaccine is available


System (STDs)

• Hepatitis B

– Hepatitis B Virus

– Highly contagious

• About 50% of infected people have symptoms that include:

fever, headache, nausea, muscle aches, abdominal pain,

jaundice

• Can lead to liver failure

– Vaccination with HBV vaccine can prevent infection


System (STDs)

• Bacterial Infections

– Treated with antibiotics

• Gonorrhea

• Syphilis

• Chlamydia– More new chlamydial infections diagnosed than any

other STD

– Mild lower urinary tract signs are common!painful

urination, burning, mucus discharge


System

• In Males

– Erectile Dysfunction (impotence)

• Inability to produce or maintain an erection

• Causes may include diseases, medications,

alcohol consumption, and psychological factors

• Drugs that increase blood flow to the penis are a

common treatment


System (Males)

• Disorders of the Prostate

– Benign Prostatic Hyperplasia (BPH)

• Enlargement of the prostate

• May constrict the urethra resulting in bladder or

kidney damage

• Treated with medications and/or surgery

– Prostate Cancer

• Most common diagnosed cancer in American

males

• Treatable if detected early


System (Males)

• Testicular Cancer

– Most common cancer in males aged 15!35

– Highly treatable if detected early

– Self-examinations are highly recommended


System (Females)

• Endometriosis

– Presence of endometrial

tissue outside of the uterine

cavity

– Pain, abnormal menstrual

cycles and infertility may

result

– Treatments include pain

management, drugs, and

surgery


System (Females)

• Ovarian Cancer

– Typically occurs in women over the age of 40

– 50% five-year survival rate

– Symptoms may not appear until the cancer is

in later stages

– Women who have not had children are at a

higher risk


System (Females)

• Disorders of Menstruation

– Too little bleeding

– Too much bleeding

– Dysmenorrhea (painful menstruation)

• Half of all women may experience this

– Premenstrual Syndrome (PMS)

• Characteristics include mood swings, headaches,

joint pains, digestive upsets, and sore breasts


System (Infertility)

• Infertility is the failure to conceive after one year

of regular, unprotected intercourse

– 15% of couples are infertile

• 40% due to male, 40% due to female, 20% due to both

– Causes

• Low sperm count or sperm abnormalities

– Sedentary life style, smoking, alcohol consumption all

contribute

• Body weight in women

– Obesity is linked to ovulation failure

• Pelvic inflammatory disease in women (blocks oviducts)

• Endometriosis


System (Infertility)

• Assisted Reproductive Technologies (ART)– Artificial Insemination by Donor (AID)

• Sperm are placed in the vagina

• Donor may be the woman’s partner or a donor

– In Vitro Fertilization (IVF)• Immature eggs are harvested and maturity occurs in vitro

• Sperm are added and fertilization takes place

• Embryos are then implanted

– Surrogate Mothers• Embryos from a couple are implanted into another woman

– Gamete Intrafallopian Transfer (GIFT)• Eggs and sperm are placed in the oviducts

– Intracytoplasmic Sperm Injection (ICSI)• A single sperm is injected into an egg and implanted

Reproduction Chapter 21

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