Development and inheritance
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Development and Inheritance. Chapter 19. Development Involves: The division and differentiation of cells The changes that produce and modify anatomical structures. Begins at fertilization (conception) Occurs among several periods: Embryological Fetal Prenatal Postnatal.

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Intro development

  • Development

  • Involves:

    • The division and differentiation of cells

    • The changes that produce and modify anatomical structures.

  • Begins at fertilization (conception)

  • Occurs among several periods:

    • Embryological

    • Fetal

    • Prenatal

    • Postnatal


Intro development1

  • Development

  • QUESTION: Why might the science of development important to us as Christians?


Intro inheritance

  • Inheritance

  • The transfer of genetically determined characteristics from generation to generation.

  • Taken to the extreme, this would reference evolutionary biology.

  • At minimum, we can account for adaptation (aka microevolution).

  • Genetics is the study of the mechanisms responsible for inheritance.



  • Fusion of 2 haploid gametes:

  • Spermatazoon

    • Paternal genetic information

    • Takes ½-2 hours to go from vagina to upper uterine tube

    • 10,000 of 200,000,000 get to upper uterine tube

    • <100 reach the ovum.

    • Multiple spermatozoa required to breach corona radiata

  • Ovum

    • Nourishment

    • Genetic programming

    • 2x diameter of spermatozoon

    • 2000x volume of spermatozoon

  • Produce a zygote of 46 chromosomes

    • Pop culture references:

      • Tool – 46 & 2



  • Activation of the oocyte

  • Ovulation happens before the oocyte is completely mature.

  • It’s development is on pause: fertilization or death

  • The corona radiatamust be affected by multiple sperm.

    • The collective pool of the enzumehyaluronidase from the acrosomal body of the spermatozoa breaks the bonds between adjacent follicle cells of the corona radiata.

  • Activation occurs when a spermatozoon contacts the zonapellucida. This membrane is broken by additional acrosomal enzymes to breach the oocyte membrane. This is fertilization.




The first trimester


  • Period of embryological and early fetal development, also the most dangerous.

  • The basic components of each major organ systems appear.

  • Only about 40% of embryos survive this trimester.

  • 4 general processes occur:

    • Cleavage & blastocyst formation

    • Implantation

    • Placentation

    • Embryogenesis

The First Trimester

The first trimester1


  • Cleavage: a series of cell divisions that begins immediately after fertilization.

    • 1st cleavage is 30 hours after fertilization.

    • Every other cleavage is 10-12 hours after the previous.

The First Trimester

The first trimester2


  • Blasto-meres: (blast – precursor; meros – part): the products of cleavage; genetically identical daughter cells.

    • The blastomeres form a blastocyst.

  • Blasto-cyst: (precursor cell) a hollow ball with an inner cavity called a blastocoele.

  • Blasto-coele: (koiloma – cavity).

  • Tropho-blast: (tropho – food): food for embryo.

The First Trimester

The first trimester3


When it’s fully formed, the blastocyst contacts the endometrium. At that point, cleavage ends and implantation begins. These structures form:

  • Amniotic cavity

  • Gastrulation and germ layer

  • Extraembryonic membranes

    • Yolk sac

    • Amnion

    • Allantois

    • Chorion

      hCG – human chorionic gonadotropin appears in bloodstream after implantation.

The First Trimester

The first trimester4

PLACENTATIONPlacenta formation

Placenta – temporary structure in uterine wall.

  • Provides a site for diffusion between the fetal and maternal circulatory systems.

  • Functions as a temporary endocrine organ for the mother.

    EMBRYOGENESISMaking an embryo

The First Trimester

The second and third trimester

  • End of week 12 is the end of the first trimester

  • At this point the basic elements of all the major organ systems have formed.

  • 2ND TRIMESTER: Mostly development of organs and completing organ systems. Body proportions change and at the end of the 2nd trimester, the baby looks more familiar as a human.

  • Amnion:

    • baby’s growth is faster than the amnion’s

    • Once it touches the chorion, they fuse.

The Second and Third Trimester

The second and third trimester1

  • 3rd TRIMESTER:

  • Very rapid fetal growth.

  • The baby is fully functional at the beginning of this trimester.

  • A baby born 1-2 months premature has a decent chance of survival.

The Second and Third Trimester

Effects of pregnancy on maternal systems


  • Respiratory rate

  • Tidal volume

  • Blood volume

  • Nutritional requirements climb 10-30%

  • GFR increases by 50%

  • Mammary gland size (and secretory activity starts)

  • Uterus size

Effects of pregnancy on Maternal Systems

Effects of pregnancy on maternal systems1


  • Increase occurs mostly from enlargement of existing smooth muscle cells rather than by the increase in the total number of cells.

  • Estrogen

  • Stimulating hormone

  • Contraction increaser

  • Progesterone

  • Inhibiting hormone

  • Contraction decreaser

  • Also present: prostaglandins and relaxin

Effects of pregnancy on Maternal Systems

Labor and delivery

  • The goal of labor is parturition: forcibly expelling the baby from the uterus.

  • 3 Stages of Labor

    • Dilation

    • Expulsion

    • Placental

  • Dilation: references the opening of the cervix.

    • Beginning of labor.

    • Baby slides down cervical canal.

    • Varies greatly, but typically lasts 8+ hours.

    • Contractions sweep from top of uterus toward cervix.

      • Occur every 10-30 minutes and steadily increase in frequency and strength

    • Amnion rupture: “water breaks”

Labor and Delivery

Labor and delivery1

  • Expulsion: occurs until baby is out of vagina.

    • Complete dilation of cervix, pushed open by baby.

    • Normally takes less than 2 hours.

  • Newborn arrival is delivery, or birth.

  • Procedures for complications in first 2 stages:

  • Episiotomy

    • If vaginal canal is too small, it poses a danger to perineal tearing.

    • Perineum sometimes intentionally cut (episiotomy) to ensure a clean break in the skin versus jagged edges.

  • C-section (cesarean section)

    • Incision made through abdominal wall

    • Uterus opened just enough to allow delivery.

Labor and Delivery

Labor and delivery2

  • Placental Stage

    • Once baby is delivered, placenta still in uterus

    • Contraction of uterus tears the connection between the endometrium and the placenta.

    • Ejection of placenta (afterbirth) normally occurs within 1 hour of delivery

    • Ejection accompanied by blood loss.

Labor and Delivery

Labor and delivery3

  • Premature Labor

    • Contractions occur prior to full development.

    • Survivability dependent largely on birth weight

      • <14 oz. will not survive – organs cannot support life.

      • 17.6 oz. is the threshold.

    • 25-27 weeks increases developmental abnormality risk.

    • 28-36 weeks is called prematuredelivery

      • High rate of survivability and low chance of developmental abnormalities.

Labor and Delivery

Labor and delivery4

  • Multiple Births

    • 1:89 births are twins

    • 1:892 births are triplets

    • Fraternal – dizygotic; “2-zygotes”

      • 2 eggs fertilized simultaneously

      • Can be of the same or different sex

      • 70% of all twin births

    • Identical – monozygotic; “1 zygote”

      • Happens 2 ways:

        • 1. Blastomeres split early in cleavage

        • 2. Inner cell mass splits before gastrulation

        • If the split is not complete, conjoined twins develop

      • Same sex

      • 30% of all twin births

Labor and Delivery

Postnatal development

  • Life stages:

    • Neonatal

    • Infancy

    • Childhood

    • Adolescence

    • Maturity

Postnatal Development

Postnatal development1

  • Neonatal period

    • 0-1 month after birth

    • Blood flow changes

    • Heart rate decreases

    • Body temperature control limited

    • Urine can’t really be concentrated yet

    • From the mom, mammary glands first produce colostrum for a few days, then milk.

    • Colostrum

      • High protein concentration (many are antibodies)

      • Low fat

    • Milk

      • Water, proteins, amino acids, lipids, sugars, salts, lysozymes (enzymes with antibiotic properties.

Postnatal development

Genetics development and inheritance

  • Phenotype: physical display

  • Genotype: genetic information

  • Allele: all the forms of a particular gene: A/a

  • i.e. the letter of the alphabet.

    • Upper-case letter (A): dominant

    • Lower-case letter (a): recessive

  • Homozygous: same case

  • Heterozygous: different case

  • 2 members of a pair are homologous

  • 22 autosomal chromosomes

  • 1 sex chromosome pair

Genetics, Development, and Inheritance

Genetics development and inheritance1

  • Types of inheritance:

    • Simple – single pair of alleles

    • Polygenetic – interactions among >1 pair of alleles

  • Males: XY

  • Females: XX

Genetics, Development, and Inheritance