Embryology Flashcards
Homologous
Arises from the same evolutionary path, from a common ancestor
Analogous
Arises from convergent evolution, a structure that performs the same function in two different organisms
Homoplastic
Two structures that look similar
Cleavage
Rapid cell division - no growth between division - until a solid ball of cells form called a morula. First step in embryo development.
Blastula formation
Formation of a blastula. Second step in embryo development.
Blastula
Hollow ball of cells (means “bud”)
Blastocoel
The empty space within a blastula. Round and even in microlecithal organisms, slightly squished in mesolecithal ones, flattened in macrolecithals.
Gastrulation
Rearrangement of cells within embryo, with outside migrating inside and differentiation of the three germ layers
Blastopore
The hole formed in blastula (the first hole), through which ectoderm cells migrate to the inside of the cell to form the endoderm.
Morula
Solid ball of cells formed from cleavage. Means “little berry”
Protostome
An organism where the blastopore becomes its mouth
Deuterostome
An organism where the blastopore becomes its butt-hole
Archenteron
“First gut”, becomes the gut lumen, formed as ectoderm migrates in the blastopore to form the endoderm, squishes up the blastocoel until the blastocoel disappears
Mesoderm
“Middle skin” - middle layer of embryonic cells
Ectoderm
“Outer skin” - outside layer of embryonic cells
Endoderm
“Inside skin” - inner layer of embryonic cells
Yolk plug
The slow division and movement of large yolk-filled cells in mesolecithal organisms create a “plug”-like structure as gastrulation occurs
Vegetal pole
In mesolecithals, the yolk-laden, slightly fatter end of the embryo
Animal pole
In mesolecithals, the smaller, pointer end of the embryo
Embryonic origin of notochord
Mesoderm
Neurulation
Formation of neural tube. Neural plate ectoderm sinks down and forms a neural groove surrounded by neural folds. The folds then come together to form a neural tube. Anterior end of neural tube swells to become brain
Neural plate ectoderm location?
Dorsal side of ectoderm
Neural crest cells origin
Neural plate ectoderm – forms off of neural folds, highly mobile cells
Which end of the neural tube swells to become the brain?
Anterior (front)
Embryonic origin of brain
Neural tube, from neural plate ectoderm
Embryonic origin of epidermis
Somatic ectoderm
Embryonic origin of (anterior) mouth
Somatic ectoderm
Embryonic origin of olfactory organs
Somatic ectoderm
Embryonic origin of cloacal opening
Somatic ectoderm
Embryonic origin of anterior pituatary
Somatic ectoderm
Embryonic origin of splanchnocranium
Neural crest ectoderm
Embryonic origin of peripheral nervous system
Neural crest ectoderm
Embryonic origin of teeth (in part)
Neural crest ectoderm
Embryonic origin of cranial muscles
Neural crest ectoderm
Embryonic origin of some chondrocranium
Neural crest ectoderm
Embryonic origin of brain
Neural plate ectoderm
Embryonic origin of spine
Neural plate ectoderm
Embryonic origin of cranial/spinal motor nerves
Neural plate ectoderm
Embryonic origin of posterior pituatary
Neural plate ectoderm
Embryonic origin of anterior pituatary
Somatic ectoderm
Three types of ectoderm
Somatic, neural crest, neural plate
Embryonic origin of gut lining
Archenteron, endoderm
Embryonic origin of liver, gallbladder, pancreas
Endoderm
Embryonic origin of mouth (posterior)
Endoderm
Embryonic origin of urinary bladder
Endoderm
Embryonic origin of respiratory tract (including lungs)
Endoderm
Cloaca
Endoderm
Mesoderm germ layers
Epimere, mesomere, hypomere
Embryonic origin of nephric and reproductive ducts
Mesomere mesoderm
Epimere layers
Dermatome, scleratome, myotome
Embryonic origin of dermis
Dermatome epimere mesoderm
Embryonic origin of vertebra column and ribs
Scleratome epimere mesoderm
Embryonic origin of limb and axial muscles
Myotome epimere mesoderm
Embryonic origin of kidney
Mesomere mesoderm
Embryonic origin of limb skeleton
Somatic hypomere mesoderm
Parts of the hypomere
Somatic, splanchnic, coelom
Coelom forms the …
… body cavity
Embryonic origin of the heart
Splanchnic hypomere mesoderm
Embryonic origin of smooth muscle in digestive tract
Splanchnic hypomere mesoderm
Embryonic origin of the gonads
Somatic hypomere mesoderm
Mesenchyme
Mobile mesoderm cells
Microlecithal
Little yolk
Mesolecithal
Medium yolk
Macrolecithal
Lots o’ yolk
Epiblast
A layer of cells above the yolk, all cells differentiate from here in macrolecithals
Hypoblast
Scaffolding formed on the yolk, will eventually be lost during development
Koller’s sickle
A bulge of cells from which the primitive streak is formed as it migrates
Primitive streak
A “zipper” line through which macrolecithal gastrulation takes place. Development takes place in a “wave” because of the quicker development of the anterior end
Hensen’s node
The end of the primitive streak
Gastrulation (macrolecithals)
Epiblast cells move in to blastocoel through primitive streak and differentiate into mesoderm and ectoderm
Neurulation (macrolecithals) begins where?
Anterior end
Embryonic origin of somites
Epimere mesoderm
Pericardial cavity
Contains the heart
Pleuroperitoneal cavity
Contains lungs + rest of internal organs
Pleural cavity
Contains lungs
Peritoneal cavity
Contains viscera, lined by peritoneum
Embryonic origin of peritoneum
Somatic hypomere mesoderm
Neurocoel
Hollow space in neural tube, a hollow canal containing spinal fluid in adults
Extra-embryonic membranes
Membranes that develop outside the embryo
Yolk sac
Grows around and contains the yolk, produces vitelline vessels that carry nutrients to embryo
Embryonic origin of yolk sac
Mesoderm
Allantois
Sequesters nitrogenous waste and takes the place of a placenta
Embryonic origin of allantois
Endoderm
Chorion
Linked with allantois, use for gas exchange in eggs
Embryonic origin of chorion
Ectoderm
Amnion
Water-tight seal around the embryo that provides cushioning and prevents drying out