REPRODUCTION AND HEREDITY Chapter 18 REPRODUCTION AND HEREDITY

Endocrine System The 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 Glands Endocrine 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.

Hormones A 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 Glands The endocrine glands include Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus gland Adrenal glands Pancreas Reproductive glands

Hypothalamus Hypothalamus: 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 Gland Releasing 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 Glands Reproductive Glands: Males: reproductive glands consist of two testes and in females, two ovaries Puberty: 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 System Structure and Function Reproduction: the process by which organisms produce offspring Reproductive cells are called sperm The 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 System

Fertilization A sperm cell may join with an egg in a process called fertilization A fertilized egg can develop into a baby

Testes Testes: 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

Testes Testes, 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

Testes One 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

Penis The penis is the external sexual organ through which sperm leave the body The tip of the penis is covered with loose skin, called the foreskin In some males the foreskin is removed shortly after birth This procedure is called circumcision Usually decided based on cultural or religious reasons

Sperm Production Millions 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 Sperm Sperm are produced in the testes. They mature and are stored in the epididymis Sperm travel through the vas deferens to the seminal vesicles. Seminal vesicles add a fluid that provides a source of energy for the active sperm The prostate gland adds a fluid that protects the sperm The bulbourethral glands add a fluid that protects sperm from acidic conditions in the urethra.

Pathway of Sperm and Release Sperm 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 Sperm The 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 Sperm Urethra: a tube that passes through the penis to the outside of the body It carries urine as well but not at the same time There is a valve within the urethra the prevents the fluids from mixing Several million sperm cells are released during one ejaculation Sperm stored in the male eventually degenerate, break down, and are disposed of

Erection Ejaculation can only occur when the penis is in an erect state An 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 erection Sexual excitement Tight clothing No apparent reason at all Nocturnal Emissions: wet dream, an erection and ejaculation during sleep

Keeping Healthy Caring for the male reproductive system involves cleanliness, sexual abstinence, protection from trauma, self-exams, and regular medical checkups.

Keeping Healthy Cleanliness: Thoroughly clean all external organs Sexual 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 Healthy Protection from Trauma: protection and prevention Self 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 Conditions Prostrate gland surrounds the urethra In many older man, the prostate becomes enlarges or develops cancer Starting 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.

Infertility 3 causes: Exposure to chemicals Having mumps after puberty Having an undescended testis

Female Reproductive System

Female Reproductive System The female reproductive system is called eggs or ova The 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

Ovaries Reproductive 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 Progesterone Estrogen: 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 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

Vagina Vagina, 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 Cycle Females 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

Menopause Except 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 Cycle Days 1-4: The uterine lining is shed during menstruation Days 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 Discomfort Many 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 Checkups Women should do self exam on themselves of their own bodies A 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 Checkups Starting at age 40, women should get a mammogram A mammogram is an x-ray of the breast that can help detect breast cancer Other detections: Ovarian cyst: growths on the ovary Endometriosis: 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

Heredity Heredity: passing on of biological traits from parent to child Chromosomes: 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)

Genes A 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 Disorder Genetic 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 Advances Genetic 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