Reproduction & Development Chp 21

GAMETE FORMATION Meiotic division produces Haploid Gametes Egg Sperm

Anatomy Of A Sperm Cell Arcosome head Midpiece tail

Anatomy Of Egg Cell Jelly coat Membrane Organelles

Sperm and egg unite: 6-24 hours after intercourse, sperm survives days One sperm fertilizes one egg Acrosome: rich in digestive enzymes Sperm penetrates corona radiata and zona pellucida Sperm proteins lock with egg membrane receptors Zona pellucida made impermeable to other sperm Fertilization

Arcosomal Reaction Arcosome opens & releases digestive enzyme Fertilization tube forms DNA moves into egg & joins w/Egg DNA

Prevention of Polyspermy Wave of depolarization - Fast block to polyspermy Cortical reaction - fertilization membrane

1.Fraternal: more than one oocyte fertilized by different sperm, may be different sex 2.Identical: one oocyte fertilized, split before 16 cell stage, same sex 3.Conjoined twins: separation not complete Twins

Developmental Processes 1.Cell division or mitosis - cell division without cell growth 2.Differentiation - individual cells take on specialized forms and functions 3.Morphogenesis - physical development of organism, ongoing 4.Growth - at implantation, growth in size

1.Cleavage - 2.Blastulation - 3. Gastrulation - 4.Organogenesis/Nerulation - Summary Early Developmental Events

Process Travels through oviduct Implantation into uterine lining Growth, differentiation, and morphogenesis begins Morula to blastocyst to embryonic disk Ectopic pregnancy possible Pre-embryonic Development: The First Two Weeks

Tissues and organs: derived from three germ layers Ectoderm: body covering & neural structures - brain, spinal cord, & nerves. Mesoderm: skeleton, muscles, blood vessels, heart, kidneys, gonads, & dermis. Endoderm: primitive gut, lungs, liver & pancreas [+ most organs] Embryonic Development: Weeks Three to Eight, Embryo

Placenta and Umbilical Cord Figure 21.8

Development Chorion digests into endometrium, creating pool of blood Placenta seals off the pool and projects chorionic villi into blood Villi contain blood capillaries connected through the umbilical vessels to the fetus Placenta

Functions Filters nutrients, waste, and antibodies for fetus without mixing mother or fetal circulations Some toxins or viruses may pass through Hormonal: produce estrogen and progesterone Placenta ( cont.)

Embryo Development: Third and Early Fourth Week Figure 21.9

Day 15 Primitive streak: appears in embryonic disk, elongates along one axis Day Neural groove: brain and spinal cord Somites: bone, muscle, skin Pharyngeal arches: part of face, neck, and mouth Limb buds: arms and legs Rapid Embryo Development

Months three and four: organ development, beginnings of organ function Months five and six: fetal movement begins, responds to external sounds, survival possible outside mother Months seven through nine (third trimester): growth and maturation Fetal Development: Eight Weeks to Birth

Stages of Birth Figure 21.13A

Stages of Birth ( cont.) Figure 21.13B, C

Labor & delivery Stages of labor: Stage 1: dilation Stage 2: expulsion Stage 3: afterbirth Cesarean delivery: surgical delivery of baby Birth

Transition from fetus to newborn Taking the first breath: pulmonary surfactants necessary Changes in cardiovascular system Umbilical circulation cut off Ductus venosus regresses to connective tissue Foramen ovale and ductus arteriosus close in days/weeks All blood from the digestive tract goes to liver Lactation: colostrum to milk Early Postnatal Period

Neonatal period: helpless period, movement by reflex Infancy; rapid development and maturation of organ systems Childhood: continued development and growth Adolescence: transition to adulthood Birth to Adulthood

Causes of aging: theories Internal cellular program that counts finite number of cell divisions, thus determining cell death Cell DNA damaged beyond repair Aging a whole body process; all systems interdependent Aging: Change Over Time

Body systems: age at different rates; musculoskeletal, skin, cardiovascular, respiratory, immune, nervous, sensory, reproductive, endocrine, digestion and nutrition, urinary Aging well: life style, exercise, diet Aging: Change Over Time ( cont.)

Legal and medical criteria Irreversible cessation of circulatory and respiratory functions Irreversible cessation of all functions of the entire brain, including the brain stem Death: Final Transition