Introduction Part 2 Flashcards
(23 cards)
Three major approaches to studying embryology:
Anatomical approaches
Experimental approaches
Genetic approaches
4 Anatomical approach:
1._____ Study of how anatomy changes during development of different organisms
2._____ Study of how changes in development may cause evolutionary change
3.____ The study of birth defects
4.____ Seeks to describe developmental phenomena in terms of equations
Comparative embryology
Evolutionary embryology
Teratology
Mathematical modeling of development
___________- observed different ways animals are born:
____ Eggs hatch outside the mother
____ Growth in placenta live brith
____ Eggs hatch inside the mother
ARISTOTLE:
Oviparity (chicken)
Viviparity (live birth)
Ovoviviparity (shark)
ANATOMICAL APPROACH
An application of _____________:
_____ identified the two major cell division patterns by which embryos are formed:
1. _____
The entire egg is divided into smaller cells like in frogs and mammals
2. _____
Part of the egg becomes the embryo and the other serves as nutrition like reptiles and birds
Comparative Embryology
ARISTOTLE
- Holoblastic pattern of cleavage
- Meroblastic pattern of cleavage
EVOLUTIONARY EMBRYOLOGY:
______:
_____ Share a close evolutionary relative with similar structure, like a human and seal limb.
____ Similar purpose but not necessarily same structure. Like a butterfly and a bird both flying. Or like a Shark(fish) and dolphin (mammal)
Embryonic homologies
Homologous
Analogous
TERATOLOGY:
ex: ______
- Caused by a dominant mutation in a ___ on the long arm of the chromosome.
- Causes the proliferation and migration of neural crest cells, germ cell precursors, and blood cell precursors
Piebaldism
gene (KIT)
TERATOLOGY:
_____
- Abnormalities caused by exogenous agents
- Agents responsible for it are called ____
Disruptions
Teratogen
study of how environmental agents disrupt normal development
teratology
TERATOLOGY:
ex: _____
- Hypnotic agent widely used in Europe
- Caused 7000 infants to be born with ____ or ____
- Limb abnormalities
Thalidomide
Thalidomide syndrome or Phocomelia
TERATOLOGY
- _____ and ____ made observations for Thalidomide
- ____ Documented the period of susceptibility which is ___ - ___ days postconception and ____-_____ days past menstruation
- ____ Grammy nominated german singer with Phocomelia
McBride and Lenz
Nowack; 20-36 days and 34-50 days
Thomas Quasthoff
HISTORICAL BACKGROUNDS:
_____ in 5th century bc
- He tried to explain development in terms of the principles of heat, wetness, and solidification
- Believed embryo began development by extracting moisture and breath from mother.
- Condensations and fires responsible for the development of bones, belly, and circulation in the embryo and fetus.
- Supported the view that human fetus gained nourishment by sucking blood
Hippocrates
HISTORICAL BACKGROUNDS:
_____
Established “Embryology” as an independent field
Figured out the functions of ____ and the ____
Defined ____ and ____
Aristotle
Placenta and the Umbilical cord
Epigenesis and Preformation
HISTORICAL BACKGROUNDS:
_____
Concluded that all animals originate from eggs (even mammals)
First to see the ___ (layer of cells that develop on the surface of the yolk which gives rise to the disk where the embryo develops) of the chick embryo
___________: Motto on the frontpiece of his On the Generation of Living Creatures
William Harvey (1651)
Blastoderm
Ex ovo omnia! ( all from eggs)
HISTORICAL BACKGROUNDS:
_____ (1672)
Drew first micrograph of developing chick embryos and published the first microscopic account of chick development
Identified the neural groove (precursor of the neural tube), the muscle-forming somites, and the first circulation of the arteries and veins – to and from the yolk.
Ignited debate within preformationist vs epigenesist
Marcello Malphigi (1672)
How debate between epigenesis and preformation
1._____
The body is already patterned in miniature, within the early embryo
2._____
The structures of the body arise de novo (from scratch) at each generation during embryogenesis
Embryo develops progressively from an undifferentiated egg cell
Preformationism
Epigenesis
Preformation or Epigenesis?
- no evolution
- all creations are created at the same time
- Adam contained all human within him
- _____________, 1694
- No external force needed for embryonic development
- fertilization had never been observed
- no cell theory (1600s) to provide lower limit to the size of organisms
Preformation
- Homunculus Hartsoeker
DESCRIPTIVE EMBRYOLOGY
______
The first embryologist
Visualized epigenesis of embryonic germ layer
He also discovered _____
Christian Pander
Tissue Interactions (Induction)
Embryonic germ layer (3)
______: epidermis, forms the brain nervous system
______: digestive system, lungs
______: muscle, bone, connective tissue, heart, kidney, gonad
Ectoderm: outer layer
Endoderm: inner layer
Mesoderm: middle layer
DESCRIPTIVE EMBRYOLOGY:
_____
- the first embryologist
- Observed the development of frogs, salamanders, fish, turtles, birds, and mammals
Discovered ____ in fishes it forms ____ in humans it forms ____, ____, and ____
Heinrich Rathke
Pharyngeal arches
- fish: Gill Apparatus
- human: Jaw, Ears, Vertebrate Skull
DESCRIPTIVE EMBRYOLOGY:
____
Found by Heinrich Rathke for the development of the pituitary gland
Rathke’s pouch
DESCRIPTIVE EMBRYOLOGY
_____
“Father” of developmental biology
Expanded Pander’s studies on chick embryos
Idnetifies ________ - rod of dorsal - most mesoderm tissue. It divides embryo in right and left sides and instruct ectoderm above it to differentiate into nerve tissue.
discovered Mammalian egg
And differences among different vertebrate embryos
Karl Ernst Von Baer
- notochord
Principles of Karl Ernst von Baer:
_____
Example: vertebrates appear very similar shortly after gastrulation
_____
Example: All vertebrates initially have the same kind of skin
_____
Example: human embryo does not turn into a lizard
_____
Embryo of a human is similar to embryos of lower animals
Principles of Karl Ernst von Baer (summarized):
- GENERAL FEATURES of a large group of animals appear EARLIER IN DEVELOPMENT than the specialized features.
- LESS GENERAL CHARACTERS develop FROM THE MORE GENERAL, until the most specialized appear
- EMBRYO of a given species, instead of passing through the adult stages of lower animals, DEPARTS more and more FROM LOWER ANIMALS
- The EARLY EMBRYO of a higher animal is NEVER LIKE A FULLY FORMED LOWER ANIMAL, but only like its early embryo
All vertebrate embryos have (4)
Pharyngeal arches
Notochord
Spinal cord
Primitive kidneys
