Chapter 18Chapter 18REPRODUCTION AND HEREDITY

Endocrine SystemEndocrine SystemThe endocrine system regulates

long-term changes in the body such as growth and development. It also controls many of your body’s daily activities.◦Body’s use of energy from a meal◦Its response to stress

Endocrine GlandsEndocrine GlandsEndocrine gland: produces and

releases chemical substances that signal changes in other parts of the body

Sweat glands release their chemicals into tiny tubes called ducts. The ducts carry the chemicals to the places where they will be used. Endocrine glands do not have ducts.

HormonesHormonesA chemical substance produced by an

endocrine gland is known as a hormone

A hormone travels to its target cells, where it turns on, turns off, speeds up, or slows down the activities of those cells.

Example: targets of the hormone adrenaline include cells in your heart, muscles, and brain. ◦Fight or flight response

Functions of Endocrine Functions of Endocrine GlandsGlandsThe endocrine glands include

◦Hypothalamus◦Pituitary gland◦Thyroid gland◦Parathyroid glands◦Thymus gland◦Adrenal glands◦Pancreas◦Reproductive glands

HypothalamusHypothalamusHypothalamus: an endocrine

gland located in the brain, actually part of both the nervous and the endocrines systems◦Example: Nerve signals from the

hypothalamus control body temperature and feelings of sleep and hunger, and hormones from the hypothalamus control the body’s water levels

Pituitary GlandPituitary GlandReleasing hormones from the

hypothalamus signal the release of hormones from a pea-sized endocrine gland in the brain, called the pituitary gland.

Functions include: growth, reproductions, and metabolism

Metabolism: process by which you obtain energy from food

Other Endocrine GlandsOther Endocrine GlandsReproductive Glands: Males: reproductive glands consist of two

testes and in females, two ovariesPuberty: period of sexual development

during which a person becomes sexually mature and physically able to reproduce

Puberty starts when the hypothalamus signals the pituitary gland to begin producing two hormones

These hormones in turn signal the reproductive glands to produce sex hormones

Sex hormones activate several changes in your outward appearance

The Male Reproductive The Male Reproductive SystemSystemStructure and FunctionReproduction: the process by which

organisms produce offspringReproductive cells are called spermThe functions of the male

reproductive system are to produce sex hormones, to produce and store sperm, and to deliver sperm to the female reproductive system

Male Reproductive SystemMale Reproductive System

FertilizationFertilizationA sperm cell may join with an

egg in a process called fertilization

A fertilized egg can develop into a baby

TestesTestesTestes: male reproductive glands

◦Two functions Production of testosterone production of sperm

Testosterone: affects the production of sperm and signals certain physical changes at puberty, such as growth of facial hair

TestesTestesTestes, also called testicles, hang

outside the main body cavity, within a sac of skin called the scrotum

The temperature of the testes is a few degrees lower than the temperature inside the body

Sperm need this lower temperature to develop properly and survive

TestesTestesOne or both of the testes may not

descend into the scrotum before birth, a condition called undescended testis.

Sperm will not develop properly because the temperature is too high

This condition is also a risk factor for testicular cancer

Surgery is usually performed before age two to correct this condition

PenisPenisThe penis is the external sexual organ

through which sperm leave the bodyThe tip of the penis is covered with

loose skin, called the foreskinIn some males the foreskin is

removed shortly after birthThis procedure is called circumcisionUsually decided based on cultural or

religious reasons

Sperm ProductionSperm ProductionMillions of sperm are produced in

his testes each day.Sperm production begins when

the hypothalamus signals the pituitary gland to release two hormones◦Luteinizing hormone: signal the tests

to begin making testosterone◦Follicle-stimulating hormone: signals

the production of sperm

Pathway of SpermPathway of Sperm1. Sperm are produced in the testes.

They mature and are stored in the epididymis

2. Sperm travel through the vas deferens to the seminal vesicles.

3. Seminal vesicles add a fluid that provides a source of energy for the active sperm

4. The prostate gland adds a fluid that protects the sperm

5. The bulbourethral glands add a fluid that protects sperm from acidic conditions in the urethra.

Pathway of Sperm and Pathway of Sperm and ReleaseReleaseSperm cells mix with fluids

produced by the prostate and two other glands.

The mixture of sperm cells and these fluids is called semen

Release of SpermThe ejection of semen from the

penis is called ejaculation.Ejaculation occurs when muscles in

the male reproductive system and at the base of the bladder contract, forcing semen through the urethra

Release of SpermRelease of SpermUrethra: a tube that passes through

the penis to the outside of the bodyIt carries urine as well but not at

the same timeThere is a valve within the urethra

the prevents the fluids from mixingSeveral million sperm cells are

released during one ejaculationSperm stored in the male

eventually degenerate, break down, and are disposed of

ErectionErectionEjaculation can only occur when

the penis is in an erect stateAn erection is a condition in

which the penis becomes larger and stiffer as blood chambers in the penis become filled with blood

Most erections do not result in an ejaculation

Factors of an erectionFactors of an erectionSexual excitementTight clothingNo apparent reason at all

Nocturnal Emissions: wet dream, an erection and ejaculation during sleep

Keeping HealthyKeeping HealthyCaring for the male reproductive

system involves cleanliness, sexual abstinence, protection from trauma, self-exams, and regular medical checkups.

Keeping HealthyKeeping HealthyCleanliness: Thoroughly clean all

external organsSexual abstinence: healthy

choices can prevent such infections. The only way to eliminate your risk of sexually transmitted infections is to abstain or refrain from sexual activity

Keeping HealthyKeeping HealthyProtection from Trauma:

protection and preventionSelf Exams: monitor your bodies

for any signs of possible medical problems

Pain when urinating, unusual discharges, or sores on the genitals require medical attention

Medical ConditionsMedical ConditionsProstrate gland surrounds the urethraIn many older man, the prostate

becomes enlarges or develops cancerStarting at age 50, men are

encouraged to get screened for prostate cancer

Prostate cancer is the second most common cause of cancer death of older men

Infertility: condition of being unable to reproduce.

InfertilityInfertility3 causes:

◦Exposure to chemicals◦Having mumps after puberty◦Having an undescended testis

Female Reproductive Female Reproductive SystemSystem

Female Reproductive Female Reproductive SystemSystemThe female reproductive system

is called eggs or ovaThe functions of the female

reproductive system are to produce sex hormones, to produce eggs, and to provide a nourishing environment in which a fertilized egg can develop into a baby

OvariesOvariesReproductive glands in which

eggs are produced are called ovaries

Each ovary (2) is the size of an almond

Importance of the ovary:◦They produce the female sex

hormones estrogen and progesterone◦Release mature egg cells

Estrogen and Estrogen and ProgesteroneProgesteroneEstrogen: activate certain physical

changes at puberty such as breast development and controls the maturation of eggs

Progesterone activates changes to a women’s reproductive systems before and during pregnancy

Ovulation: once puberty begins, one of the ovaries releases a ripened egg about once every month in a process

Fallopian TubesFallopian Tubes

Fallopian Tubes: passageways that carry eggs away from the ovaries

Tiny hairlike extension called cilia line the fallopian tube and sweep the egg toward the uterus

Uterus: hollow, muscular pear-shaped organ

The narrow base of the uterus is called the cervix

VaginaVaginaVagina, or birth canal, is a hollow,

muscular passage leading from the uterus to the outside of the body

Sperm enter a female’s body through the vagina

During childbirth, the baby passes out of the mother’s body through the vagina

The walls of the vagina are very elastic, which allows it to expand dramatically during childbirth

Menstrual CycleMenstrual CycleFemales produce only one mature

egg cell each month during a process called the menstrual cycle.

During the cycle, an ovary releases a mature egg. The egg travels to the uterus. If the egg is not fertilized the uterine lining is shed and a new cycle begins.

A cycle usually lasts 28 days

MenopauseMenopauseExcept during pregnancy,

menstrual cycles occur each month from puberty until about the age of 45 to 55.

Menopause: the ovaries slow down their hormone production and no longer release mature eggs

The menstrual cycle stops

Stages of the Menstrual Stages of the Menstrual CycleCycleDays 1-4: The uterine lining is shed

during menstruationDays 5-13: An egg matures in one of

the ovaries, and the uterine lining thickens

Days 14-15: The ovary releases the mature egg during ovulation

Days 16-22: The egg travels through the fallopian tube to the uterus, and the uterine lining continues to thicken

Days 23-28: The unfertilized egg enters the uterus

Menstrual DiscomfortMenstrual DiscomfortMany women experience

abdominal cramps or other discomfort

If you are experiencing cramps, try◦Engaging in moderate exercise◦Take a warm bath◦Apply a heating pad on the abdomen◦Take aspirin or ibuprofen with

doctor’s approval

Self-Exams and Medical Self-Exams and Medical CheckupsCheckupsWomen should do self exam on

themselves of their own bodiesA yearly checkup of the

reproductive system is recommended for all females who have reached puberty

An exam will include a pelvic exam and a pap smear

Pap smear: a sample of cells is taken from the cervix and examined under a microscope

Medical CheckupsMedical CheckupsStarting at age 40, women should get

a mammogramA mammogram is an x-ray of the

breast that can help detect breast cancer

Other detections:Ovarian cyst: growths on the ovaryEndometriosis: condition in which

tissue from the lining of the uterus grows outside the uterus in the pelvic cavity

Infertility: blocked fallopian tubes and problems with ovulation

HeredityHeredityHeredity: passing on of biological

traits from parent to childChromosomes: tiny structures

found within cells that carry information about the characteristics you will inherit

Most of the cells in your body contain 23 pairs of chromosomes

Sex cells (sperm or eggs) contain 23 chromosomes

(23 from each parent)

GenesGenesA gene is a section of a

chromosome that determines or affects a characteristic or trait

Hereditary information passes from one generation to the next through genes contained on the two sets of chromosomes that a person receives from their parents

Genetic DisorderGenetic DisorderGenetic Disorders are caused by

the inheritance of an abnormal gene or chromosome

For most diseases, your environment and your behavior affect your risk as much as or even more than your genes

Medical AdvancesMedical AdvancesGenetic Testing: Analysis of a

blood sample for the presence of abnormalities in specific genes

Gene therapy: scientists are currently researching a technique in which healthy copies of a gene are delivered to the cells of a person who has a defective copy of the gene