Biology Chapter 3 Embryogenesis and Development

Fertilization

occurs in ampulla

Cortical Reaction

release of calcium ions that depolarizes ovum membrane

What does a cortical reaction prevent?

fertilization of one ovum by multiple sperm and increased calcium concentration increasing metabolic rate of newly formed diploid zygote

Fertilization Membrane Type

depolarized and impenetrable membrane

Dizygotic/Fraternal Twins

two sperm fertilize two eggs

What do the zygotes create in a dizygotic pregnancy?

placenta, chorion, amnion

Monozygotic/Identical Twins

zygote splits in half

How are conjoined twins produced?

division is incomplete

What do monochorionic/monoamniotic twins share?

amnion and chorion

What do monochorionic/diamniotic twins share?

chorion

What do dichorionic/diamniotic twins share?

nothing, they have their own amnion and chorion

Cleavage

mitotic cell divisions

What does the first cleavage of a zygote form?

embryo

What does cleavage do in terms of exchanging materials?

increases area for gas and nutrient exchange

Intermediate Cleavage

produces cells that can develop into complete organisms

Determinate Cleavage

cells committed to differentiating into certain type of cell

Morula

solid mass of cells formed after several divisions

Blastulation

hollow ball of cells formed with fluid-filled inner cavity

Blastula

hollow ball of cells

Blastocoel

fluid-filled inner cavity

Trophoblast

surround blastocoel and produces chorion and placenta

Trophoblast Function

create interface between maternal blood supply and embryo

Inner Cell Mass

protrudes into blastocoel and produces organism

Chorion Villi

facilitate maternal-fetal gas exchange

Umbilical Cord

connects placenta to embryo

How many arteries does an umbilical cord have?

two

What is the function of umbilical cord arteries?

carry deoxygenated blood and waste from embryo to placenta

How many veins does an umbilical cord have?

one

What is the function of umbilical cord veins?

carry oxygenated blood with nutrients from placenta to embryo

Yolk Sac Function

supports embryo

What occurs in the yolk sac?

early blood cell development

Allantois Function

fluid exchange between embryo and yolk sac

Amnion Description

thin, tough membrane surrounding allantois and filled with amniotic fluid

What is the function of the fluid in the amnion?

shock absorber

What forms on the outside of the amnion?

chorion

Gastrulation Function

generates three distinct cell layers

What are the layers of gastrulation?

ectoderm, mesoderm, endoderm

Gastrula Description

embryonic stage characterized by three layers

Archenteron Description and Stage

central cavity in gastrula stage

What does the archenteron form?

adult digestive tract

Blastopore Description

opening of archenteron to external environment

What does the blastopore develop into in deuterostomes?

anus

What does the blastopore develop into in protostomes?

mouth

Deuterostomes Examples

humans and mammals

Protosomes Examples

insects

Ectoderm Layer

outermost layer

What does the ectoderm create?

epidermis, hair, nails, epithelia of nose, mouth, lower anal canal, lens of eye, nervous system, inner ear

What does attracto mean for the ectoderm?

cosmetic features and smarts

Mesoderm Layer

middle layer

What does the mesoderm create?

musculoskeletal system, circulatory system, excretory system, gonads, muscle tissue, connective tissue in GI and respiratory system, adrenal cortex

What does means mean for the mesoderm?

means of getting around

Endoderm Layer

innermost layer

What does the endoderm create?

epithelial lining of digestive, respiratory tract, including lungs, pancreas, thyroid, bladder, distal urinary tracts, part of liver

What does end mean for the endoderm?

respiratory, digestive, accessory organs

What occurs in selective transcription?

only the genes needed for particular cell are prescribed

Selective Transcription Induction

ability of one group of cells to influence fate of nearby cells

Selective Transcription Inducers

diffuse from organizing cells to responsive cells

Neurulation

development of nervous system after germ layers form

Notochord Description

rod of mesodermal cells

What does the notochord form along?

long axis organism like spine

Neural Folds Description

group of overlying ectodermal cells that slide together to create a fold

What do the neural folds surround?

neural groove

Where are the neural grooves?

between neural folds

Neural Tube

embryonic hollow tube

What do the neural tubes form?

CNS

What birth defect do those without closed neural tubes have?

spina bifida

Neural Crest Walls Location

tip of neural folds

What do the neural crest walls form?

PNS and specific cell types in other tissues

Organogenesis Function

formation of organs

Teratogens Description

substances that interfere with development causing defects or death of developing embryo

Common Teratogens

alcohol, prescription drugs, viruses, bacteria, environmental chemicals

If a mother is hyperglycemic, what happens to her baby?

hypoglycemia and overweight

If a mother has a folic acid deficiency, what happens to her baby?

may affect closure of neural tube and cause spina bifida or anencephaly

Specification Stage of Development

cell is reversibly designated to specific cell type

Determination Stage of Development

cell commits to having particular function in future

Morphogens Function

cause nearby cells to proceed in specific developmental pathway during embryonic development

Differentiation Stage of Development

undertake changes and cause cell to develop into determined cell

Stem Cells Function

able to differentiate into different cell types

Stem Cell Potency Function

determines how many different cell types stem cell can be

Totipotency

greatest potency

Pluripotent

cells can differentiate into anything except those in placental structures

Multipotent

cells can differentiate into multiple cells of particular group

Multipotent Cell Examples

blood, skin, neurons, muscle cells

Inducer

cell secreting signal

Responder

reduced cell

Growth Factors

peptides promoting differentiation and mitosis in certain tissues

Autocrine Signals

act on same cell that secreted signal

Paracrine Signals

act on cells in local area

Juxtacrine Signals

do not involve diffusion and feature a cell directly stimulating receptors of adjacent cell

Endocrine Signals

involve secreted hormones that travel through bloodstream to distant target tissue

Cell Migration

cells disconnect from adjacent structures and migrate to anatomically correct location

Apoptosis

cell death

Necrosis

cell death due to injury

Complete Regeneration

stem cells migrate for regrowth of identical tissue

What can undergo complete regeneration?

salamanders and human liver

Incomplete Regeneration

newly formed tissue is not identical in structure or function

Senescence

occurs as changes accumulate

Cellular Senescence

failure of cells to divide due to shortened telomeres

Telomerase

reverse transcriptase enzyme

Telomerase Function

synthesize chromosome ends to prevent senescence