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Functional Anatomy - Lecture 1
Develoment & Anatomy
Embryology – can explain some peculiar anatomical arrangements
ex. Why do the arteries & veins associated w/ the testes originate in the middle of the abdomen?
Start exactly as female ovaries but descend to regulate temperature for sperm production
Development & Evolution
Even though adult morphology may differ embryonic stages are often similar in related species
- Karl erst von Baer – general embryonic similarities noted
- Ernst Haeckel – biogenetic law; “ontogeny recapitulates phylogeny” (it doesn’t!)
*as an embryo of an advanced organism grows it will pass through stages that look similar to the adult phase of a less advanced organism
*animals with common ancestors tend to show more similarities
Developmental Stages
Cleavage Stages:
Zygote – fertilized egg, single-celled beginning of a new organism
* cleavage stages increase # of cells but not the total mass of the organism
2 cell, 4 cell, 8 cell, etc. until too much to count & cell becomes a
Morula – solid ball of cells
Blastula – hollow ball, cavity (blastocoel) forms in center
Patterns of Cleavage:
Holoblastic – equal
Holoblastic – unequal
Meroblastic – Partially
*differences in yolk leads to differences in cleavage patterns because yolk is hard to cleave.
Yolk Characteristics:
Distribution –
Isolecithal – equally distributed
Telolecithal – off to one side
Amount –
Alecithal – no yolk therian mammals
Microlecithal – small amount urochordates
Mesolecithal – moderate amount many fish & amphibians
Macrolecithal – large (most) amount amniotes except therian mammals
Chart:
|
Chordate Ex amount of yolk distribution type of cleavage |
|
Therian mamm alecithal isolecithal holoblastic equ |
|
Urochordates & cephalochordates |
|
microlecithal isolecithal holoblastic equ |
|
Some fish & amphib |
|
Mesolecithal telolecithal, moderate holoblastic uneq |
|
Some fish, rept, birds, monotrem mam |
|
macrolec telolec, extreme meroblastic |
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