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Endocrine System Brain Pop Endocrine System General Characteristics: 1. composed of glands that produce chemical messengers (hormones) which affect and influence body functions 2. important in maintaining homeostasis Hormones: 1. chemicals released in one part of the body which travel through the blood and bind to specific receptors on specific cells (called target cells), where a cell reaction or function is changed Endocrine glands: 1. Pituitary gland – often called the master gland a. Hangs from the hypothalamus under the middle of the brain b. Provides brain to body c. Hormones include: i. Growth hormone ii. Follicle stimulating hormone (FSH) – necessary for egg or sperm production iii. Luteinizing hormone (LH) – prepares lining of uterus for fertilized egg to implant iv. Thyroid stimulating hormone (TSH) – promotes release of thyroxin from thyroid Endocrine glands (con’t): 2. Hypothalamus – controls secretions of pituitary gland a. The close connection between the hypothalamus & the pituitary gland means that the nervous & endocrine systems can act together to help coordinate body activities 3. Thyroid gland – produces thyroxin which regulates body metabolism 4. Parathyroid glands – parathyroid hormone helps maintain homeostasis of calcium levels in blood 5. Adrenal glands – has 2 parts a. Cortex (outer part) – produces corticosteroids which help control such things as metabolic rates and sodium/potassium uptake by the kidney b. Medulla (inner part) – produces epinephrine (adrenalin) and norepinephrine (noradrenalin) which are responsible for the “fight or flight” responses to stress Endocrine glands (con’t): 6. Pancreas – produces insulin and glucagon to control blood sugar levels a. Lack of insulin results in diabetes mellitus or high sugar in blood and urine. If untreated, can result in death Endocrine Glands (con’t) 7. Thymus - During childhood, the thymus releases thymosin, which stimulates T-cell development • Butterfly shaped gland in middle of chest Endocrine glands (con’t): 8. Reproductive glands – produce sex hormones a. Ovary – produces…. i. Estrogen - produces female secondary sex characteristics and eggs ii. Progesterone – prepares the uterus for implantation Endocrine glands (con’t): b. Testis – produces… i. Testosterone – is responsible for male secondary sex characteristics and sperm production Review • Hormones are important parts of feedback mechanisms which maintain homeostasis in the body • Remember: feedback inhibition occurs when an increase in any substance “feeds back” to inhibit the process that produced the substance in the first place • Sometimes 2 hormones with opposite effects act to regulate part of the body’s internal environment • For example….. The Endocrine System regulates Growth Water balance Reproduction Metabolism Calcium and glucose levels Response to stress by means of the by means of the by means of the by means of the by means of the by means of the Testes Thyroid Pituitary Ovaries Pancreas Parathyroids Adrenals Reproductive- Maturity Required • Brain Pop- Reproductive System Reproductive System • Reproduction is the formation of new individuals – It is the only system NOT functional at birth! – It is the only system you can live without!! • Failure of the reproductive system to function is not fatal, but it is the single most important system for the continuation of a species • The reproductive system produces, stores, and releases specialized sex cells known as gametes • Male & female gametes fuse together to form a zygote, the single cell from which all cells of the human body develop Puberty • Puberty is a period of rapid growth & sexual maturation during which the reproductive system becomes fully functional • Onset of puberty usually occurs between the ages of 9 and 15 & begins about one year earlier in females than in males • Puberty begins when hypothalamus signals pituitary to produce increased levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Male Reproductive System • FSH and LH stimulate cells in the testes to produce testosterone • FSH and testosterone stimulates the development of sperm • The main function of the male reproductive system is to produce & deliver sperm Structures of the Male Reproductive System • The testes develop within the abdominal cavity & descend into the scrotum just before birth – The scrotum is an external sac that keeps the testes about 1 to 3 degrees lower than normal body temperature, which is important for sperm development • Within each testis are tiny tubules called seminiferous tubules where sperm are produced by meiosis Sperm Development • Sperm produced in the seminiferous tubules then move into the epididymis where they are stored until they are fully mature • From the epididymis, some sperm are moved into a tube called the vas deferens, which extends upward from the scrotum into the abdominal cavity • The vas deferens merges with the urethra, the tube leading to the outside of the body through the penis • Glands lining the reproductive tract (seminal vesicles, Cowper’s glands, & prostate) produce seminal fluid which nourishes & protects sperm. • The combination of sperm & seminal fluid produces semen Female Reproductive System • The main function of the female reproductive system is to produce ova & prepare the female’s body to nourish a developing embryo • The primary reproductive organs in the female are the ovaries, located in the abdominal cavity • Each ovary contains about 400,000 primary follicles, clusters of cells surrounding a single egg – The follicle helps an egg mature for release into the reproductive tract where it can be fertilized – Only about 400 eggs will actually be released Ovulation • When a follicle has completely matured, it breaks open and the egg is swept from the ovary surface into a Fallopian tube • The egg moves through the Fallopian tube, pushed along by cilia lining the walls – This is when the egg can be fertilized if sperm are present • After a few days, the egg passes from the Fallopian tube into the uterus, where the fertilized egg can implant & grow Menstrual Cycle • The interaction of the reproductive system & endocrine system in females is a complex series of periodic events called the menstrual cycle • The cycle takes an average of 28 days & is regulated by hormones made by the hypothalamus, pituitary gland, and ovaries • It is controlled by internal feedback mechanisms The Menstrual Cycle • An egg develops & is released from the ovary • The uterus is prepared to receive a fertilized egg – If fertilization occurs, the zygote implants in the uterus & begins embryonic development – If fertilization does not occur, the egg is discharged along with the lining of the uterus • There are 4 phases in the menstrual cycle: follicular phase, ovulation, luteal phase, & menstruation The Menstrual Cycle Sexually Transmitted Diseases • Diseases that spread from one person to another during sexual contact • STDs are a serious health problem in the US • Common bacterial STDs include chlamydia, syphilis, & gonorrhea • Viral STDs include hepatitis B, genital herpes, genital warts, and AIDS • STDs can cause infertility and, in some cases, death • Most importantly, STDs can be avoided – Any sexual contact carries chance of infection – Abstinence from sexual contact is the safest way to avoid STDs as well as unwanted pregnancy