Ch 3 Embryogenesis and Development

ampulla

widest part of the fallopian tube

acrosomal apparatus

tube-like structure that forms when the first sperm makes contact with the secondary oocyte

cortical reaction

the release of calcium ions to cause depolarization of the ovum membrane

prevents polyspermy and increases the metabolic rate of the newly formed zygote

What are the 2 purposes for the release of calcium ions?

fertilization membrane

the now depolarized and impenetrable membrane is called this

dizygotic (fraternal) twins

two different eggs released during one ovulatory cycle are fertilized by two different sperm

monozygotic (identical) twins

a single zygote splits into two

conjoined twins

monozygotic (identical) twins that didn’t fully complete division

monochorionic/monoamniotic twins

twins that share the same amnion and chorion

monochorionic/diamniotic twins

twins that share the same chorion, but have their own amnion

When the separation occurred

Monozygotic twins are classified by which structures they share and which they don’t (chorion / amnion). What determines which structures they share?

cleavage

rapid mitotic cell division of the zygote as it moves to the uterus for implantation

indeterminate cleavage

results in cells that can still develop into complete organisms

determinate cleavage

results in cells that are committed to differentiating into a certain type of cell

morula

solid mass of cells that results after the first several divisions

blastula

The thing that is formed after the morula. a hollow ball of cells with a fluid filled inner cavity

blastocoel

fluid filled inner cavity inside the blastula

blastocyst

the mammalian blastula

trophoblast cells

cells that surround the blastocoel and give rise to the chorion and later the placenta

inner cell mass

protrudes into the blastocoel and gives rise to the organism itself

chorion

extraembryonic membrane that develops into the placenta

chorionic villi

microscopic finger-like projections that penetrate the endometrium

umbilical cord

the thing that connects the embryo to the placenta

yolk sac

the site of early blood cell development that supports the embryo until the placenta is functional

allantois

involved in early fluid exchange between the embryo and the yolk sac

amnion

a thin, tough membrane filled with amniotic fluid

gastrulation

the formation of three distinct cell layers

archenteron

the membrane invagination into the blastocoel that later develops into the gut

blastopore

the opening of the archenteron that later develops into the anus (for humans)

“attracto”derm (things that are attractive to us including “smarts”)

What is the mnemonic for what the ectoderm gives rise to?

“means”oderm (means of getting around physically, like bones and muscle) (the means of getting around in the body, like circulatory system) (means of getting around such as the gonads)

Mnemonic for what the mesoderm gives rise to?

induction

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

inducers

the chemicals that facilitate the process of induction

organizing cells

the cells doing the induction

responsive cells (aka responder)

the cells receiving the induction

neurulation

development of the nervous system

notochord

rod of mesodermal cells that forms along the long axis of the organism like a primitive spine

neural folds

formed when notochord induced a group of overlying ectodermal cells to slide inward

neural tube

formed when the neural folds grow toward one another until they fuse together

neural groove

the neural folds surround this

neural crest cells

the cells at the tip of each neural fold that form the peripheral nervous system

teratogens

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

specification

the first stage of cell specialization. a cell is reversibly designated as a specific cell type

determination

the commitment of a cell to a particular function in the future

mRNA and proteins

What molecules cause determination?

morphogens

molecules that are secreted and may cause nearby cells to follow a determination pathway

differentiation

a cell changes its structure, function, and biochemistry to match the cell type

stem cells

cells not yet differentiated or will give rise to other cells that will differentiate

totipotent

cells with the greatest potency.

embryonic stem cells

What is an example of a totipotent cell?

pluripotent

cells that can differentiate into any cell type except for those found in the placental structures

multipotent

cells that can differentiate into multiple types of cells within a certain group

competent

an adjective used to describe a cell that is able to respond to an inducing signal

autocrine signals

signals that act on the same cell that secreted the signal in the first place

paracrine signals

signals that act on cells in the local area

juxtacrine signals

signals that don’t usually use diffusion, but involve a cell directly stimulating receptors of an adjacent cell

endocrine signals

signals that involve secreted hormones that travel through the bloodstream to a distant target tissue

growth factors

peptides that promote differentiation and mitosis in certain tissues

reciprocal development

when two interacting tissues both send signals that influence each other’s differentiation

transforming growth factor beta (TGF-B) sonic hedgehog (Shh) and epidermal growth factor (EGF)

What are common examples of morphogens?

regenerative capacity

the ability of an organism to regrow certain parts of the body

complete regeneration

lost or damaged tissue is replaced with identical tissue

incomplete regeneration

newly formed tissue is not identical in structure or function to the tissue that has been injured or lost

liver has high, kidney has medium, heart has low

What are some organs that have high, medium, and low regenerative capacities?

senescence

biological aging

telomeres

the ends of chromosomes

telomeres have high concentrations of guanine and cytosine

How are telomeres able to “knot off” the end of chromosomes?

telomerase; it synthesizes new ends of the chromosomes

What enzyme prevents senescence? How does it do this?

apoptotic blebs

the many self-contained protrusions formed during apoptosis

apoptotic bodies

What do apoptotic blebs become?

necrosis

a cell dying as a result of injury and cytoplasmic contents may spill

fetal hemoglobin (HbF)

has a greater affinity for oxygen than adult hemoglobin, which helps the transfer of oxygen from maternal to fetal circulation

umbilical arteries

vessels that carry blood away from the fetus toward the placenta

umbilical vein

vessel that carries blood toward the fetus from the placenta

umbilical vein

Does the umbilical vein or arteries carry oxygenated blood?

umbilical arteries

Does the umbilical vein or arteries carry deoxygenated blood?

foramen ovale

one-way valve that connects the right atrium to the left atrium, allowing blood to flow there instead of the right ventricle

ductus arteriosus

shunts leftover blood from the pulmonary artery to the aorta

ductus venosus

shunts blood returning from the placenta via the umbilical vein directly into the inferior vena cava

the eighth week

During what week does the embryo become known as a fetus?

22 days

How many days does it take for the heart to start beating?

second

During what trimester does the fetus take on a face of human appearance?

third

During what trimester do antibodies move from the pregnant person to the fetus via active transport?

parturition

vaginal childbirth

prostaglandins and the peptide hormone oxytocin

What molecules coordinate the contractions of uterine smooth muscle during parturition?

1. cervix thins out and amniotic sac ruptures (water breaking)

2. strong uterine contractions result in birth of fetus

3. placenta and umbilical cord are expelled (afterbirth)

What are the three stages of birth?