A&P Lab: Embryology & Genetics Lab

Fertilization

• fusing of spermatic nucleus with that of oocyte

• conception

Zygote

• fertilized egg

• called an embryo until end of week 8

• called a fetus from week 9 until birth

Blastomeres

daughter cells

Blastocyst

blastula in humans (chorionic vesicle)

Blastocele

blastocyst cavity

Inner cell mass (ICM)

• embryoblast

• will become embryo

Trophoblast

rest of cells, which will become extraembryonic membrane called the chorion, which will form fetal part of placenta

Ectoderm

males epidermis of skin and nervous system

Endoderm

mucosa of digestive and respiratory tract and urogenital system as well as associated glands

Mesoderm

everything else

Gastrulation

formation of 3 primary germ layers

Primary germ layers

• ectoderm

• endoderm

• mesoderm

Allantois

structural basis on which mesoderm forms body stalk (umbilical cord)

Human Chorionic Gonadotropin (hCG)

• produced by trophoblast cells to prevent menses

• like LH, maintains corpus luteum = estrogen and progesterone levels

Trophoblast cells

develop into the chorion which carries on the hCG production

Placenta

takes over estrogen and progesterone production and corpus luteum degenerates

Decidua basalis

maternal portion of placenta

Amnion

protects embryo from physical trauma and temp changes

Yolk sac

first blood cells and primordial germ cells develop here

Breech position

feet first

Vernix

cheesy white substance secreted by fetal sebaceous glands around week 20 to protect its skin

Epiblast

surface cells of embryonic disk

Epiblast cells

• migrate medially and down into primitive streak and push hypoblast cells laterally to form the endoderm

• continue migrating and for the mesoderm layer on top of the endoderm

Neural tube

becomes CNS (brain and spinal cord)

Neural crest

cells migrate widely and become PNS (cranial, spinal and sympathetic ganglia and nerves, as well as adrenal medulla, pigment cells and come connective tissues)

Notochord

forms nucleus pulposus of intervertebral disks

Somites

40 pairs of mesodermal blocks

Splanchic mesoderm

forms heart and blood vessels as well as visceral serosa, connective tissue and smooth muscle

Brown adipose tissue (BAT)

• brown fat

• heat generating fat tissue (5% body mass in neonates) mainly found around upper half of spine

Surfactant

levels checked for in amniotic fluid to see if ready to breathe

Genome

• codes for all traits, “code book”

• complete set of chromosomes

Gene

portion of DNA that codes for a single protein (a single trait)

Alleles

the pair of genes from the same location of homologous chromosomes and code for the same protein

Gametes

sex cells (sperm and ovum)

Chromosomes

• long molecules of DNA that carry genetic information, tightly coiled (chromatin when not coiled)

• sex chromosomes, autosomes

Sex chromosomes

• X and Y

• determine gender of the offspring, X is way bigger than Y

Autosomes

all the other chromosomes that come in pairs and code for most traits

Homologous

• 2 chromosomes or body parts similar in structure

• 22 pairs of autosomes and 1 pair of sex chromosomes

Diploid

• 46, referred to as 2n

• having a pair of all autosomes and 2 sex chromosomes

• the state of all cells except the gametes

Haploid

• 23, referred to as n

• having one of each autosome and 1 sex chromosome

Dominant

allele that is always expressed (represented by capital letter)

Recessive

allele that is only expressed if it is paired with another recessive allele (represented by lower case letter)

Homozygous

having 2 of the same alleles (both dominant or both recessive) (AA or aa)

Heterozygous

having 2 different alleles for the same gene (Aa)

Genotype

the codes of the alleles (Dd or DD for dimples)

Phenotype

the trait that is expressed. What you can see as a result of the proteins produced (dimples)

Punnett square

• predict the percentage of offspring with a particular trait

• both genotype and phenotype

Incomplete dominance

• both genes are expressed and measurable

• heterozygous is in between both homozygous individuals