Chapter 3 - Embryogenesis and Development

Fertilization is

joining of a sperm and ovum

fertilization occurs in

the ampulla of the fallopian tube

the sperm uses

acrosomal enzymes to penetrate the corona radiata and zone pellucida

once the sperm contacts

the oocyte’s membrane it establishes the acrosomal apparatus and injects its pronucleus

when the first sperm penetrates its causes a release of

calcium ions which prevent additional sperm from entering and increasing metabolic rate of the zygote (cortical reaction)

fraternal twins result from

dizygotic twins results form the fertilization of 2 eggs by 2 different sperm

maternal twins come from

monozygotic result from the splitting of the zygote in 2

cleavage refers to

early division of cell in embryo which result in a larger number of smaller cells

the zygote becomes an embryo when

after the first cleavage as it’s no longer unicellular

indeterminate cleavage results in

cells that are capable of becoming any cell in the organism

determinte cleavage results in

cells that are committed to differentiating into a specific cell type

the morula is a

solid mass of cells early in development

blastula

blastocyst has a fluid filled center called a blastocoel and has the trophoblast and inner cell mass

trophoblast

becomes placental structures

inner cell mass

becomes developing organism

the blastula implants

in the endometrial lining and forms the placenta

the chorion contains

chorionic villi which penetrate the endometrium and create the interface between maternal and fetal blood

before the placenta the embryo is supported by

the yolk sac

the allantois is involved in

early fluid exchnage between embryo and yolk sac

the amnion

lies inside the chorion and produces amniotic fluid

during gastrulation

the archenteron is formed with a blastopore at the end

as the archenteron grows

through the blastocoel it contacts the opposite side establishing 3 primary germ layers

3 primary germ layers

ectoderm, mesoderm, endoderm

ectoderm

becomes epidermis, hair, nails, epithelia of the nose, mouth, anal canal, the nervous system, and the lens of the eye

mesoderm

becomes the musculoskeletal, circulatory, and excretory, gives rise to the gonads and muscular and connective tissue layers of the digestive, respiratory systems, and the adrenal cortex

endoderm

becomes the epithelial lining of the respiratory and digestive tracts, parts of the pancreas, thyroid, bladder, and distal urinary tracts

neurulation

development of the nervous system comes after the formation of the 3 germ layers

development of the nervous system

the notochord induces a group of overlying ectodermal cells to form neural fold surrounding a groove, the folds fuse to form the neural tube which becomes the CNS, the tip of the fold contains neural crest cells which become the PNS

teratogens

substances that interfere with development causing defects of the embryo

cell specialization occur as a result of

determination and differentiation

determination

commitment to a specific cell lineage which may be accomplished by uneven segregation of cellular material during mitosis or with morphogens

morphogens

promote development along a specific cell line

to respond to a specific morphogen a cell must have

competency

differentiations

refers to the changes a cell undergoes due to selective transcription to take on characteristics appropriate to its cell line

stem cells

cells that are capable of developing into various cell types

potency of stem cells

totipotent, pluripotent, multipotent

totipotent

abel to differentiate into all cell types

pluripotent

able to differentiate into all 3 of the germ layers and their derivatives

multipotent

able to differentiate into a specific subset of cell types

cells communicate through

a number of different signaling methods, an inducer releases factors to promote the differentiation of a competent responder

autocrine signals

at on the same cell that released the signal

paracrine signals

act on local cells

juxtacrine signals

act through direct stimulation of adjacent cells

endocrine signals

act on distant tissues after traveling through the blood stream

growth factors

peptides that promotoe differentiation and mitosis

if 2 tissues both induce further differentiation this is

reciprocal induction

apoptosis

programmed cell death via the formation of apoptotic blebs that can be absorbed and digested by other cells

regenerative apacity

ability of an organism to regrow certain parts of the body

senescence

result of multiple molecular and metabolic processes, shortening of telomeres, aging

nutrient, gas, and waste exchange occurs at the

placents

fetal hemoglobin

has a higher affinity for O2 than adult hemoglobin which assits in the transfer of O2

the placental barrier serves as

immune protection against many pathogens, and antibodies are transferred from mother to child

the placenta serves

endocrine functions, secreting estrogen, progesterone, and human chorionic gonadotropin

the umbilical arteries carry

deoxygenated blood from the fetus to placentat

he umbilical vein

carries oxygenated blood form placenta to fetus

the fetal circulatory system differs how

it has 2 shunts: foramen ovale, ductus arteriosus, ductus venosus

foramen ovale

connects the right atrium to the left bypassing lungs

ductus arteriosus

connects the pulmonary artery to the aorta bypassing lungs

ductus venosus

connects umbilical vein to inferior vena cava, bypassing liver

in the 1st trimester

organogenesis occurs

in the 2nd trimester

tremendous growth occurs, movement begins, face becomes distinct, digits elongate

during the third trimester

rapid growth, brain development continues, and transfer of antibodies occurs

during birth

cervix thins and the amniotic sac ruptures, uterine contraction (coordinated by prostaglandins and oxytocin), result in the birth of the fetus.