lab quiz 4

unfertilized egg

has nucleus and nucleolus(germinal vesicle)

fertilized egg

no nucleus, has fertilization membrane

cleavage

rapid mitotic cell divisions after fertilization

zygote

diploid cell formed by the fusion of a haploid sperm and egg during fertilization

unicellular; right after they meet

blastula

When cleavage process transforms the large single-celled zygote into a multicellular structure

blastomeres

smaller cells that makes blastula

blastocoel

fluid-filled cavity that develops within the mass of blastomeres in the blastula.

gastrula

after blastula

embryo starts taking shape and laying down the foundation for all future tissues and organs. In triploblasts, it’s characterized by extensive cell movement and the formation of the three primary germ layers:

blastopore

first opening that forms in an early animal embryo during the gastrulation stage

It is crucial for defining the embryo's body axis and forming germ layers (endoderm, mesoderm).

The blastopore determines the animal's classification. In protostomes (e.g., mollusks, worms), the blastopore becomes the mouth, while in deuterostomes (e.g., humans, starfish), it becomes the anus.

archenteron

primitive gut, is the internal cavity formed during the gastrulation stage of embryonic development. It forms via the inward folding (invagination) of cells, developing into the animal's digestive tract (lumen)

late cleavage

The unequal cleavage sets up the animal-vegetal polarity, which influences where the body axes and germ layers will form.

gastrulation

It creates the primary germ layers—ectoderm, mesoderm, and endoderm—which are essential for organogenesis

The process of gastrulation begins at the blastula stage, which has:

• A blastocoel (fluid-filled cavity).

• An animal pole (pigmented, less yolk, smaller cells).

• A vegetal pole (larger cells, more yolk).

blastula stage

stage in early animal embryonic development that produces the blastula

blastoderm

the cells that surround a fluid-filled cavity known as the blastocoel

blastocyst

Specific to placental mammals. It represents a more advanced stage than a simple blastula, having differentiated into the trophoblast (outer layer) and the inner cell mass (embryoblast).

animal-vegetal polarity,

a fundamental asymmetry in animal eggs and blastula-stage embryos, dividing them into two distinct hemispheres: the animal pole and vegetal pole.

This polarity determines early developmental axes, with the animal pole forming the embryo proper (ectoderm) and the vegetal pole forming inner structures (endoderm/mesoderm), often defined by uneven yolk distribution

the nervous system

neural plate

thickened layer of ectodermal cells

the precursor to/becomes brain and spinal cord

neural folds

ridges of ectoderm that arise from the side edges of the neural plate

They elevate, converge, and fuse at the midline to form the neural tube, Help shape the tube

neural tube.

It forms from the folding of the neural plate into a cylinder, which seals itself shut to create a hollow structure

becomes CNS (brain + spinal cord)

neurulation

the process right after gastrulation that forms the nervous system!

makes neural places, tube and folds.

notochord

a cartilaginous skeletal rod supporting the body in all embryonic and some adult chordate animals.

gut

formed from endoderm lining the yolk sac which is enveloped by the developing coelom

somites

acting as essential segmentation units for developing vertebrae, ribs, skeletal muscles, and the dermis

hensons node

It acts as a specialized signaling center that initiates, organizes, and patterns the embryonic axis, equivalent to Spemann’s organizer in amphibians.

As it regresses caudally, it leaves behind the notochord and neural tissue.

head fold

It involves a crescent-shaped anterior folding of the blastoderm

forming the foregut, and establishing the heart region.

cranial neuropore

the final rostral opening of the neural tube,

crucial for proper brain development.

primative streak

marks the start of gastrulation, establishing the embryo’s cranial-caudal (head-tail) and bilateral symmetry

conduit for cells to migrate inward and form the three primary germ layers (ectoderm, mesoderm, endoderm)

neural fold

transient, paired ridges of ectoderm that arise from the lateral edges of the neural plate during embryonic development.

They elevate, converge, and fuse at the midline to form the neural tube, which serves as the precursor to the brain and spinal cord

neural tube

from the folding of the ectoderm to form a cylinder

heart

brain

lens vesicle

a transient, hollow sphere of surface ectodermal cells formed during embryonic eye development

otic vesicles

a hollow, pear-shaped structure formed during embryonic development from the invagination of the otic placode, serving as the precursor for the entire membranous labyrinth of the inner ear

tailbud

mesenchymal cells at the posterior end of vertebrate embryos that drives the development of the caudal body, including the tail, posterior neural tube, and somites

spinal cord

wing bud

small protrusions on the flank, developing into wings through signaling centers

leg bud

appear around 72 hours (Day 3) of incubation, emerging as mesenchymal swellings from the lateral plate mesoderm

guide the development from limb bud to functional leg