Exam 3 - Development Anatomy Lab

Main stages of development

Fertilization → Cleavage → Blastulation → Gastrulation → Neurulation → Organogenesis.

Primitive streak vs. dorsal lip

Chicks and pigs form a primitive streak; frogs form the dorsal lip of the blastopore. Both start gastrulation.

Chick yolk & cleavage

dense yolk concentrated at one end with partial division.

Telolecithal yolk; meroblastic (partial) cleavage.

Frog yolk & cleavage

moderate amount of yolk that unevenly distributed (heavy on vegetal pole), the entire egg completely develops but the yolk slows down the furrow

Mesolecithal yolk; holoblastic (complete) cleavage.

Pig yolk & cleavage

very little yolk and complete whole cleavage

Microlecithal yolk; holoblastic cleavage.

Blastodisc

A disc of cells on top of the yolk where the chick embryo develops.

Research models

Chicks, frogs, and pigs are all good models because they develop quickly and are similar to humans in key ways.

Neurulation structures

Neural plate, notochord, and neural folds.

Notochord

Signals neural plate formation and helps form the body axis.

Neural plate

Becomes the brain and spinal cord.

Neural folds

Fold together to form the neural tube.

Gastrulation

Forms the three germ layers: ectoderm, mesoderm, and endoderm.

Purpose of gastrulation

Prepares the embryo for organ development.

Development types

Chick = external/direct; Frog = external/indirect; Pig = internal/direct.

Animal pole

Upper part of the egg; less yolk; cells divide faster.

Vegetal pole

Lower part of the egg; more yolk; cells divide slower.

Frog blastula

Know the blastocoel, animal pole, and vegetal pole.

Frog gastrula

Know the blastopore, archenteron, and yolk plug.

Organogenesis

Formation of organs from the three germ layers.

Stage before organogenesis

Gastrulation.

Coelom

forms main body cavity.

Frog notochord

Forms the body axis and helps develop the nervous system.

Germ layer for nervous system

Ectoderm.

Neural tube

Develops into the brain and spinal cord.

Chick advantages

Easy to observe, develops outside the mother, similar early development to mammals.

Frog advantages

Many eggs, develops externally, easy to manipulate.

Pig advantages

Very similar to humans in genes, organs, and physiology.

Pig disadvantages

Expensive, need special housing, reproduce slowly.

Why pigs are good for transplants

Organs are similar in size and function to human organs.

Prevent pig organ rejection

Genetically modify pigs to reduce immune rejection.