HS 130 Anatomy & Physiology II Unit 9 Seminar Chapters 20 & 21 Reproduction, Growth and Development Male Reproductive System • Structural plan Reproductive organs are classified as essential or accessory Essential organs of reproduction are the gonads (testes in males), which produce sex cells called sperm Testes • Testes: the gonads of men Structure and location Testes in scrotum—lower temperature Covered by tunica albuginea, which divides testis into lobules containing seminiferous tubules Interstitial cells produce testosterone What is the importance of the lower temperature of the scrotum? Tubules of the Testis and Epididymis the testicle is the darker sphere in the center Spermatozoa Spermatogenesis What are the steps in the process of spermatogenesis? Female Reproductive System How does the location of the female gonads differ from the location of the male gonads? Ovaries • Microscopic structure Ovarian follicles—contain oocyte, an immature sex cell (about 1 million at birth) Primary follicles—are covered with granulosa cells (about 400,000 at puberty) Secondary follicles have a hollow chamber called the antrum Corpus luteum forms after ovulation from ruptured follicle Ovaries What is the role of the corpus luteum if fertilization occurs? Ovaries Menstrual Cycle Menstrual Cycle Summary of Male and Female Reproductive Systems • Male organs Designed to produce, store, and introduce mature sperm into the female reproductive tract • Female organs Designed to produce ova, receive the sperm, permit fertilization, facilitate fetal development and birth, and perform lactation Prenatal Period • Prenatal period begins at conception and continues until birth • Science of fetal growth and development is called embryology Approximately how long does pregnancy last? Why is prenatal care so important? Fertilization and Implantation •Fertilization is a specific biological event •occurs when the male and female sex cells fuse •after union between a sperm cell and the ovum has occurred, the cycle of life begins. •scanning electron micrograph shows spermatozoa attaching themselves to the surface of an ovum •only one will penetrate and fertilize the ovum. • After three days of cell division, the zygote has developed into a solid cell mass called a morula • Continued cell division of the morula produces a hollow ball of cells called a blastocyst • The blastocyst implants in the uterine wall about 10 days after fertilization • The blastocyst forms the amniotic cavity and chorion of the placenta Implantation and Early Development How does the embryo receive nutrients before the placenta is functional? Primary Germ Layers The Placenta What are the functions of the placenta? Birth Defects • Any structural or functional abnormality present at birth May be caused by genetic factors Abnormal genes Abnormal number of chromosomes May be caused by environmental factors Environmental factors are called teratogens Especially harmful during the first trimester Postnatal Period • Postnatal period begins at birth and lasts until death • Divisions of postnatal period into isolated time frames can be misleading • Life, growth, and development are continuous • Obvious changes in the physical appearance occur between birth and maturity Infancy • First four weeks is called neonatal period • Cardiovascular and respiratory changes occur at birth Fetus is totally dependent on mother Newborn must immediately become totally self-supporting Childhood • Extends from end of infancy to puberty • Overall rate of growth remains rapid but decelerates • Continuing development of motor and coordination skills • Loss of deciduous or baby teeth and eruption of permanent teeth Adolescence • Average age range of adolescence varies from 13 to 19 years • Period of rapid growth results in sexual maturity (adolescence) • Appearance of secondary sex characteristics regulated by secretion of sex hormones • Growth spurt typical of adolescence; begins in girls at age 10 and in boys at age 12 Adulthood • Bones’ growth plates are fully closed in adult • Other structures such as the sinuses acquire adult placement • Adulthood characterized by maintenance of existing body tissues • Older adulthood Every organ system of the body undergoes degenerative changes Effects of Aging • Skeletal system Aging causes changes in the texture, calcification, and shape of bones Bone spurs develop around joints Bones become porous and fracture easily Effects of Aging • Integumentary system (skin) With age, skin sags and becomes Thin Dry Wrinkled Effects of Aging • Urinary system Nephron units decrease in number by 50% between ages 30 and 75 Blood flow to kidney and ability to form urine decrease Effects of Aging • Respiratory system Calcification of costal cartilages makes it difficult for rib cage to expand and contract normally Wasting of respiratory muscles decreases respiratory efficiency Respiratory membrane thickens; movement of oxygen from alveoli to blood is slowed Effects of Aging • Cardiovascular system Degenerative heart and blood vessel disease is among the most common and serious effects of aging Hardening of arteries (arteriosclerosis) may result in rupture of blood vessels Hypertension or high blood pressure is common in older adulthood Effects of Aging • Special senses Eye lenses become hard and cannot accommodate for near vision Decreased transmission of sound waves caused by loss of elasticity of eardrum and fixing of the bony ear ossicles is common Some degree of hearing impairment is universally present in the aged Thanks for attending! I’ll “see” everyone on the discussion boards!