Human Endocrine & Reproductive System

1. Human Endocrine & Reproductive System Unit 19 Chapter 39

2. Endocrine System • Made up of glands that release their products into the bloodstream. The products deliver messages throughout the body. • Glands release “chemicals” called hormones • Cells that have receptors for a particular hormone are called target cells • Body’s response to hormones are slower and longer-lasting than the response to nerve impulses. • Several minutes to several days (nerve within fractions of a second)

3. Glands • A gland is an organ that produces and releases a substance (or secretion) • Exocrine – release their secretion through tubelike structures (ducts) – sweat glands, tear glands, secretion of digestive juices • Endocrine – release their secretions (hormones) directly into the bloodstream

5. Glandular Function

6. Reproductive Glands (Gonads) Ovaries • Produce Sex Hormones • Estrogen • Egg Development • Secondary Sex Characteristics • Development of Reproductive system, widening of hips, breast development • Progesterone • Prepares uterus for the arrival of developing embryo • Produce Eggs

7. Reproductive Glands (Gonads) Testes • Produces Testosterone • Normal sperm production • Male Secondary Sex Characteristics • Facial Hair, Increase in Body Size, Deepening of Voice • Produce Sperm

8. Name That Gland! Pineal Pituitary Thyroid Thymus Adrenal Pancreas Ovary Testis

9. Endocrine Control • Endocrine system is controlled by feedback mechanisms that function to maintain homeostasis. • Feedback Inhibition – occurs when an increase in any substance “feeds back” to inhibit the process that produced the substance in the first place • Hypothalamus acts like a thermostat by regulating the feedback mechanisms

10. Thyroxine Example Hypothalamus TRH Anterior Pituitary Inhibition TSH Thyroid Thyroxine

11. 39.3 The Reproductive System • Reproductive system produces, stores and releases specialized cells (gametes). • When gametes fuse (sperm & egg) a zygote is formed • From this single celled zygote a human body develops

12. Sexual Development • 1st 6 weeks human male and female embryos are identical • During 7th week, major changes occur • Testes develop in males & ovaries develop in females • Testes start to produce testosterone – make male reproductive organs • Ovaries start to produce estrogen – embryo develops female reproductive organs • Continue to produce small amounts of hormones up until puberty when active reproductive cells are produced

13. Puberty & the Pituitary • Puberty is a period of rapid growth and sexual maturation – reproductive system becomes fully functional • Occurs between the ages of 9 and 15 • Begins when hypothalamus signals pituitary gland to produce increased levels of two hormones • FSH • LH

14. Male Reproductive System • FSH & LH stimulate cells in testes to produce testosterone • FSH and testosterone stimulate the production of sperm *** Main function of male reproductive system is to produce and deliver sperm ***

15. Male Reproductive System • Testes – inside abdominal cavity; produce sperm • Scrotum – external sac where testes reside • Seminiferous tubules – where sperm are produced • Epididymis – where sperm mature and are stored • Vas deferens – tube that moves sperm from epididymis to urethra • Urethra – tube that allows sperm to travel outside of the body through the penis. • Glands – produce seminal fluid

16. Sperm Development • Sperm consist of a head (nucleus/DNA), midpiece (mitochondria), and a tail (propels sperm forward); Tip of sperm has a cap that contains an enzyme vital for allowing fertilization to occur. • Seminal fluid and sperm make up semen. • There are between 50 – 130 million sperm in 1 milliliter of semen. (2.5 mil sperm/drop) • 2 to 6 milliliter of semen are released in an average ejaculate

17. Female Reproductive System • Hypothalamus signals pituitary to produce FSH & LH • FSH stimulates ovaries to produce estrogen • *** Main function of male reproductive system is to produce ova and nourish a developing embryo *** • Ovaries usually only produce one mature ovum (egg) per month

18. Female Reproductive System • Ovaries – located inside abdomen and produce eggs • Fallopian tube – tube carries egg from ovary to uterus (it is here the egg gets fertilized) • Uterus – lining is prepared to receive fertilized egg w/in a couple days of release • Cervix – outer end of uterus • Vagina – beyond cervix; canal that leads to the outside of the body

19. Egg Development • Every ovary contains about 400,000 primary follicles (clusters of cells surrounding a single egg). • Follicle helps an egg mature • Eggs develop within their follicles • Females are born with thousands of primary follicles • Only 400 eggs are usually released approximately every 28 days (due to FSH allowing the egg to get larger and meiotically dividing) • Remember in meiosis 4 haploid cells are produced (3 polar bodies and 1 large haploid egg) • Ovulation – release of egg from matured follicle

20. Menstrual Cycle • Menstrual cycle is regulated by hormones made by the hypothalamus, pituitary gland and ovaries and is controlled by internal feedback mechanisms. • Begins at puberty and continues until a woman reaches her mid-forties. • Menopause – permanent stopping of menstrual cycle (about age 51) • Has four phases (course of apx 28 days) • Follicular • Ovulation • Luteal • Menstruation

22. Follicular Phase • Begins when • Estrogen level is low and hypothalamus reacts to this low level • Pituitary releases FSH and LH • Causes follicle to develop to maturity • Cells surrounding egg enlarge and produce increased estrogen • Follicle produces more and more estrogen • Estrogen causes uterine lining to thicken (preparing for fertilized egg) • Egg development takes about 10 days

23. Ovulation • Occurs midway through the cycle and lasts 3 – 4 days • Hypothalamus sends a large amount of releasing hormone to the pituitary gland • Pituitary produces high levels of FSH and LH (a spike in these hormone levels is apparent) • Release of these hormones causes follicle to rupture releasing the mature egg into the Fallopian tubes

24. Luteal Phase • Begins once egg has been released • Cells of ruptured follicle change and the follicle turns yellow (now known as corpus luteum) • Corpus luteum secretes estrogen but also progesterone • Added progesterone continues growth and development of the blood supply and surrounding tissue • Within the first 2 days of the luteal phase the highest chances of fertilization occurs • 10 -14 days after the completion of last menstrual cycle • If egg is fertilized it will mitotically divide • After several divisions a ball of cells will implant into the lining of the uterus • Embryo will continue to grow by mitoitic divisions and will release hormones that keep the corpus luteum functioning for a few weeks (allows for uterine lining to nourish and protect embryo)

25. Menstruation • If fertilization does not occur • Within 2-3 days the egg will pass through the uterus without implanting • Corpus luteum will disintegrate • Old follicle breaks down • Less estrogen and progesterone are produced • Lower levels of these hormones in blood • When level of estrogen falls below a certain point, the lining of the uterus begins to detach from uterine wall – menstruation (lasts 3 – 7 days) • A new cycle begins on the 1st day of menstruation! • Cycle begins again with hypothalamus signaling pituitary to release LH and FSH

27. Fertilization and Development

28. Fertilization in a Nut Shell • Sperm and Egg joining = Fertilization • Millions of sperm are released per ejaculation but only one sperm will break down the layer and the sperm nucleus joins with the egg nucleus (due to granules being released by egg which prevents other sperm from entering the egg). • Forms Diploid cell = Zygote

29. Development • Zygote begins to divide (mitosis) • Cell number doubles (2-4-8-16-32-etc) • After 4 days the embryo is about 64 cells = morula • Early stages of development • Implantation • Gastrulation • Neurulation

31. Implantation • Morula grows and cavity forms in the center = blastocyst • 6-7 days after fertilization the blastocyst attaches to the uterus = implantation • Cells start to differentiate • Inner cell mass • Surrounding tissue Implantation

32. Gastrulation • Inner cell mass of blastocyst becomes 2 layers – which give rise to a 3rd = Gastrulation • 3 Layers (Primary germ layers) • Ectoderm = skin/nervous • Mesoderm = internal tissues & organs • Endoderm = digestive

34. Neurulation • Neurulation follows gastrulation • Development of nervous system • Mesodermal tissue differentiates into a notochord (chordate characteristic) • Neural groove changes producing ridges (neural folds) – forms neural tube

35. Extraembryonic Membranes • Membranes start to form to protect and nourish the embryo • Amnion • Develops fluid-filled amniotic sac which cushions and protects the embryo • Chorion • End of third week the chorion has formed • Chronic villi form on chorion and help form the placenta (provides embryo with nutrients and Oxygen)

37. Day 1:fertilization: all human chromosomes are present; unique human life begins. Day 6:  embryo begins implantation in the uterus. Day 22:  heart begins to beat with the child’s own blood, often a different type than the mothers’. Week 3:  By the end of third week the child’s backbone spinal column and nervous system are forming.  The liver, kidneys and intestines begin to take shape. Week 4:  By the end of week four the child is ten thousand times larger than the fertilized egg.  Week 5:  Eyes, legs, and hands begin to develop. Week 6:  Brain waves are detectable; mouth and lips are present; fingernails are forming.Week 7:  Eyelids, and toes form, nose distinct.  The baby is kicking and swimming. Week 8:  Every organ is in place, bones begin to replace cartilage, and fingerprints begin to form.  By the 8th week the baby can begin to hear. (FETUS)      Weeks 9 and 10:  Teeth begin to form, fingernails develop.  The baby can turn his head, and frown.  The baby can hiccup.  Weeks 10 and 11:  The baby can “breathe” amniotic fluid and urinate.  Week 11 the baby can grasp objects placed in its hand; all organ systems are functioning.  The baby has a skeletal structure, nerves, and circulation.  Week 12:  The baby has all of the parts necessary to experience pain, including nerves, spinal cord, and thalamus.  Vocal cords are complete.  The baby can suck its thumb.  6-8 wks 1st Trimester Development

38. 2nd Trimester • Week 14:  At this age, the heart pumps several quarts ofblood through the body every day. • Week 15:  The baby has an adult’s taste buds. • Month 4:  Bone Marrow is now beginning to form.  The heart is pumping 25 quarts of blood a day.  By the end of month 4 the baby will be 8-10 inches in length and will be one half of its birth weight. • Week 17:  The baby can have dream (REM) sleep.  • Week 19:  Babies can routinely be saved at 21 to 22 weeks after fertilization, and sometimes they can be saved even younger. • Week 20:  The earliest stage at which Partial birth abortions are performed.  At 20 weeks the baby recognizes its’ mothers voice. 12-14 wks 17-19 wks

39. 5-6 mos Third Trimester •  Months 5 and 6:  The baby practices breathing by inhaling amniotic fluid into its developing lungs. The baby will grasp at the umbilical cord when it feels it.  Most mothers feel an increase in movement, kicking, and hiccups from the baby.  Oil and sweat glands are now functioning.  The baby is now twelve inches long or more, and weighs up to one and a half pounds.   • Months 7 through 9:  Eyeteeth are present.  The baby opens and closes his eyes.  The baby is using four of the five senses (vision, hearing, taste, and touch.)  He knows the difference between waking and sleeping, and can relate to the moods of the mother.  The baby’s skin begins to thicken, and a layer of fat is produced and stored beneath the skin.  Antibodies are built up, and the baby’s heart begins to pump 300 gallons of blood per day.  Approximately one week before the birth the baby stops growing, and “drops” usually head down into the pelvic cavity. 

40. Childbirth • Oxytocin released from pituitary allows for contraction to occur • Contractions become more frequent and powerful • Cervix expands to 10 cm • Amniotic sac will rupture • Baby is born • Afterbirth

41. Multiple Births • Identical • Single zygote splits apart to produce two embryos • Single zygote from one egg and one sperm • Fraternal • 2 eggs fertilized by 2 sperm • Now don’t ask someone that has a boy and girl set of twins if they are identical, you’ll look stupid! 