Chapter 24 Development & Inheritance Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fertilization Genetic material from haploid sperm & ovum merge into single diploid nucleus Occurs in Uterine tube= 12-24 hours after ovulation Sperm last ~48 hours Contraction of uterus & uterine tube walls help move sperm Prostaglandins in semen help stimulate Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fertilization Sperm Capacitation- ready for penetration Acrosomal enzymes penetrate outer cell layers and one sperm fuses with ovum meiosis II is completed- polar body discarded Fusion of DNA’s  diploid = zygote Rapid cell division = cleavage Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fertilization Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fertilization Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Early Development Continual division ball of small cells =Morula- enters uterine cavity ~ day 4-5 Reorganizes around fluid filled cavity =blastocyst- about same size as zygote Rearrangement Inner cell mass embryo + Trophoblast fetal part of Placenta Implants after ~2 days ~6 days after fertilization Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Early Development Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Early Development Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 2nd Week of Development Trophoblast synctiotrophoblast + cytotrophoblast  chorion Aids in implantation & secretes hCH Inner cell mass hypoblast & epiblast Cavity in epiblast  amniotic cavity Thin membrane develops to surround embryo = amnion filled with amniotic fluid Hypoblast ceils –cover inner surface= wall of yolk sac (from blastocyst cavity) Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 2nd Week of Development Yolk sac –nutrients for weeks 2 & 3 + source of blood cells (week 3-6) Day 9 – blastocyst embedded in endometrium Lacunae develop in trophoblast Maternal blood and secretions fill Serve as exchange point for embryonic nutrient and waste removal Day 12 - cells from yolk sac + two layers of trophoblast  chorion  surrounds embryo & becomes fetal part of placenta Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 2nd Week of Development Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 2nd Week of Development Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 3rd Week Gastrulation= transformation of disc from 2 -> 3 layers= Primary ectoderm, mesoderm & endoderm Cells of epiblast move inward & detach Push out cells of hypoblast endoderm Become mesoderm Rest of epiblast  ectoderm Mesoderm notocord vertebrae Ectoderm neural plate neural tube neurulation Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 3rd Week Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 3rd Week Copyright 2010, John Wiley & Sons, Inc.

Allantois, Chorionic Villi & Placenta Outpouch of yolk sac  allantois Chorionic villi develop with capillaries end 3rd week - capillaries connect to embyronic heart via umbilical arteries & veins Placenta: chorionic villi & maternal endometrium Exchange organ. Some viruses can get through Copyright 2010, John Wiley & Sons, Inc.

Allantois, Chorionic Villi & Placenta Copyright 2010, John Wiley & Sons, Inc.

Allantois, Chorionic Villi & Placenta Copyright 2010, John Wiley & Sons, Inc.

Allantois, Chorionic Villi & Placenta Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 4th- 8th Weeks All major organs appear at this time Converted from disc to cylinder 22 days- Ear- otic placode & eyes- lens placode 4th week- upper & lower limb buds & heart prominence on surface 5th week- rapid growth of brain & head Neck & trunk straighten, 4 chambered heart, digits appear End of 8th week looks human fetus Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Continual growth & differentiation Few new structures added Last 2 1/2 months – half of weight added Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Fetal Birth Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Hormones hCG- maintains corpus lutem progesterone & estrogen Peaks at week 9 Chorion secretes several hormones: estrogens after 3-4 wks & progesterone by wk 6 Rise through pregnancy Progesterone helps keep myometrium relaxes & cervix closed Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Hormones (cont.) Relaxin- increases flexibility of pubic symphysis & ligaments & relaxes cervix for birth Human placental lactogen (hPL) Rises with fetal mass Prepare mammary glands Support metabolic capacity Corticotrophin-Releasing Hormone (CRH) Helps support birth timing & cortisol production for lung maturation Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Endocrine Support Trophoblast cells secrete hCG hCG maintains corpus luteum corpus luteum continues to secrete relaxin, progesterone and estrogen & Chorion adds hPL, progesterone + estrogen & CRH Estrogen & progesterone promote growth, development and maintenance of the uterine wall hPl supports maternal growth and changes CRH corticoids lung maturation Copyright 2010, John Wiley & Sons, Inc.

Changes During Pregnancy Uterus fills up pelvic cavity-3rd month Further growth into abdominal cavity Pushes on intestines, stomach, liver Skin changes: areola, pigmentation around eyes, stretch marks Increased: maternal C.O., blood volume, nutrient consumption appetite , O2 needs ventilation , renal activity Pressure: diaphragm  dyspnea Stomach acid reflux & nausea Bladder  frequent urination Copyright 2010, John Wiley & Sons, Inc.

Exercise During Pregnancy Major issues: postural changes with weight gain extra Heat production may affect development early on Care to avoid dehydration Moderate exercise doesn’t hurt May be beneficial Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Labor & Delivery Labor = expelling fetus from uterus through vagina= parturition Progesterone inhibits contractions Estrogen rises toward end  overcome inhibition +  prostaglandin production +  oxytocin receptors on myometrium Oxytocin contractions Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Stages of Labor Dilation: onset to complete dilation of cervix Expulsion- dilation to complete delivery Placental- powerful uterine contractions expel placenta Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Positive Feedback Contractions baby’s head against cervix Neural signals  hypothalamus more oxytocin  more pushing Stops after birth when cervix is not stretched True labor shows rhythmic pulses of contraction Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Negative Feedback Systems Interactions Animation Positive Feedback Control of Labor You must be connected to the internet to run this animation. Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Lactation Prolactin(PRL)  milk production PRL increases as pregnancy proceeds Progesterone inhibits milk production Progesterone decreases after delivery Oxytocin milk letdown feedback loop for maintenance Suckling  nerve input to hypothalamus maintain PRL & release oxytocin Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Colostrum Formed during first few days after birth Less lactose & no fat + antibodies Protect infant during first few months of life Good nutrition for infant Oxytocin also speeds maternal recovery Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Inheritance Passage of hereditary traits- genetics 23 pairs of chromosomes- 1 maternal and 1 paternal Each homolog (one of pair) has gene for same traits variant genes for a trait = alleles Genotype= genetic makeup Homozygous = have 2 of same allele Heterozygous= 2 different alleles Phenotype= trait that is visible (brown eyes) Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Inheritance Dominant allele  shows product no matter what the other allele is Recessive allele  masked by other allele Can have incomplete dominance phenotype mixture of allele products Inheritance can be simple (one gene) or multiple allele. Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Inheritance Copyright 2010, John Wiley & Sons, Inc.

Autosomes & Sex Chromosomes Autosomes: chromosomes where members of pair look alike - 22 pairs Sex chromosomes - look different Females have 2 X chromosomes Males have X and Y chromosomes Maleness from SRY of Y chromosome Traits on X but not Y sex linked inheritance Copyright 2010, John Wiley & Sons, Inc.

Autosomes & Sex Chromosomes Copyright 2010, John Wiley & Sons, Inc.

Autosomes & Sex Chromosomes Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. End of Chapter 24 Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein. Copyright 2010, John Wiley & Sons, Inc.