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The Reproductive System The Male - The scrotum, which contains the testis, is a few degrees cooler than that of the abdominal cavity because sperm cannot develop at body temperature - The vas deferens carries sperm from the testes to the urethra. A vasectomy can be done to prevent this from happening. The ejaculatory duct regulates the movement of semen into the urethra, which is also where urine comes out - A sphincter (circular muscle) regulates the movement of urine from the bladder. At any given time, the urethra conducts either urine or sperm, but never both at the same time - During sexual excitement, the erectile tissue in the penis fills up with blood. The parasympathetic nerve is stimulated, causing arteries leading to the penis to dilate, increasing blood flow. As blood moves into the penis, the sinuses swell, compressing the veins that carry blood away from the penis - Sperm cells have very little cytoplasm. This is good for movement, but it also makes the sperm have limited energy. Sertoli Cells nourish the developing sperm. - At the tip of the sperm, there is an acrosome which is filled with special enzymes that dissolve the outer coating surrounding the egg, allowing it in - Inside the testis, there are seminiferous tubules which are lined with sperm-producing cells called spermatogonia. During meiosis, spermatogonia divide into spermatocytes. Sperm cells then mature in the epididymis (attached to outer edge of the testis) - Fluid is secreted by 3 glands along the vas deferens and the urethra 1. Seminal vesicle 2. Prostate gland 3. Couper’s gland (bulbourethral) 1. Seminal Vesicle – secretes fluid that contains fructose (source of energy for sperm) and contains prostaglandins facilitating the relaxation of the muscle walls that delineate blood vessels, effectively dilating them (act as chemical signal in the female system) 2. Prostate Gland – secretes an alkaline buffer that protects sperm against the vagina’s acidity 3. Couper’s Gland – secretes mucus-rich fluids before ejaculation, which protect sperm from acidity in urethra because of urine, and assist in sperm movement Male Hormones - Androsterone and testosterone are produced in the interstitial cells of the testes. - Testosterone – stimulates spermatogenesis (maturation of sperm cells) - also influences development secondary sex characteristics (facial and body hair), growth of larynx, strengthening of muscles - used in production of anabolic steroids - The hypothalamus and pituitary gland control the production of testosterone, other hormones, and sperm Gonadotropic hormones – regulate function of testes FSH (follicle stimulating hormone) – stimulates production of sperm cells LH (luteinizing hormone) – promotes production of testosterone by the interstitial cells (cells in the testes) GnRH (gonadotropin releasing hormone) – activates pituitary gland to secrete and release FSH and LH Vasectomy Procedure Sperm The Female Zygote – fertilized egg Blastocept – when the fertilized egg reaches the uterus (6 days after fertilization) it has been transformed into a cell mass Implantation – when the blastocept becomes attached to the wall of the endometrium HCG – a hormone (human chorionic gonadotropic hormone) which maintains the corpus luteum (produces progesterone estrogen which maintain the endometrium) for the 1st 3 months of pregnancy - identifiable in urine of pregnant women Chorion – outer membrane of blastocept, produces HCG Amnion – inner membrane of blastocyst, evolves into fluid-filled sac that insulates the embryo Placenta – made up of cells of the fetus and cells of the endometrium Chorionic villi – projections of the placenta which ensure that many blood capillaries of the mother are exposed to a large number of blood capillaries of the fetus Allantois – a membrane that provides blood vessels in the placenta - does not envelop the fetus like the chorion and amnion does Umbilical cord – connects the embryo with the placenta 1st Trimester – from fertilization to the end of the 3rd month - 3 germ layers form (ectoderm, mesoderm, and endoderm) - heart has formed, limb buds have developed 2nd Trimester – from beginning of 4th month to the end of the 6th month - all organs are formed - eyelids and elelashes form 3rd Trimester – from the beginning of the 7th month to birth – baby grows rapidly – organs become more developed Female Hormones Relaxin – hormone produced by the placenta prior to labor - causes ligaments within the pelvis to loosen, providing a more flexible passage-way for the baby during delivery Oxytocin – a hormone from the posterior pituitary gland, causes strong uterine contractions Lactation – elevated levels of estrogen and progesterone prepare the breasts for milk production Prolactin – hormone produced by the pituitary gland, responsible for stimulating glands within the breast to begin producing fluids In Vitro Fertilization – the egg is fertilized outside of the body - Laparoscope – device inserted into the woman’s abdomen, enables the physician to locate the ovary: allows the extraction of eggs form the ovary Diabetes Mellitus Diabetes mellitus is a chronic disease caused by inherited and/or acquired deficiency in production of insulin by the pancreas, or by the ineffectiveness of the insulin produced. Such a deficiency results in increased concentrations of glucose in the blood, which in turn damage many of the body’s systems, in particular the blood vessels and nerves. There are two principle forms of diabetes: - Type 1 diabetes (formerly known as insulin-dependent) in which the pancreas fails to produce the insulin, which is essential for survival. This form develops most frequently in children and adolescents, but is being increasingly noted later in life - Type 2 diabetes (formerly named non-insulin-dependent) results from the body’s inability to respod properly to the action of insulin produced by the pancreas. Thype 2 diabetes is much more common and accounts for around 90% of al diabetes cases worldwide. It occurs most frequently in adults, but is being noted increasingly in adolescents as well. Certain genetic markers have ben shown to increase to risk of developing Type 1 diabetes. Type 2 diabetes is strongly familial, but it is only recently that some genes have been onsistenly associated with increased risk for Type 2 diabetes in certain populations. Both types of diabetes are complex diseases caused by mutations in more than one gene, as well as by environmental factors. Diabetes in pregnancy may give rise to several adverse outcomes, including congenital malformations, increased birth weight and an elevated risk of perinatal mortality. Strict metabolic control may reduce these risks to the level of those of non-diabetic expectant mothers. Impaired glucose tolerance (IGT) and impaired fasting glycaemia (IFG) refer to levels of blood glucose concentration above the normal range, but below those which are diagnostic for diabetes. Subjects with IGT and/or IFG are at substantially higher risk of developing diabetes and cardiovascular disease tan those with normal glucose tolerance. The benefits of clinical intervention in subjects with moderate glucose intolerance is a topic of much current interest Symptoms – The symptoms of diabetes may be pronounced, subdued, or even absent - In Type 1 diabetes, the classic symptoms are excessive secretion of urine (polyuria), thirst (polydipsia), weight loss and tiredness - These symptoms may be less marked in Type 2 diabetes. In this form, it can also happen that no early symptoms appear and the disease is only diagnosed several years after its onset, when complications are already present. Sexual Versus Asexual Reproduction Asexual reproduction does not involve sex cells or gametes (produced through meiosis). Rather, it is reproduction by mitosis allowing a new, genetically identical individual to be produced. Both methods of reproduction have advantages and disadvantages. Sexual reproduction allows genetic variation and allows the development of a population that is specifically adapted to its surrounding (and is therefore more likely to survive). However, when a very desirable combination of traits is found, sexual reproduction risks losing them in the randomness of the process. Asexual reproduction does not allow genetic variation, but guarantees reproduction (no dependence on others). It rapidly increases numbers of an organism and keeps its desired combination of traits. Many plants reproduce use a combination of sexual and asexual reproduction to get the benefits of both methods. The earthworm is a hermaphrodite. A hermaphrodite is an animal that has both the male and female reproductive organs. During mating, both individuals behave as both sexes. Each individual both receives and donates sperm. This greatly increases the number of potential mates by allowing a worm to make with any other worm in the population. Then the worms expel the fertilized eggs into the ground, with a protective membrane surrounding them.