- 1.Introduction to Comparative Anatomy Lectured byBien Nillos,
MD Reference: George C. Kents Comparative Anatomy of the
Vertebrates
2. Comparative Anatomy
- Study of the structure of vertebrates, of the functional
significance of structure and of the variation in structure and
function in geological time.
- It is a study of historyof the speicies that preceded us on
this planet, of the effects of mutations, of adaptations, of the
struggle for compatibility with an ever-changing environment, of
the invasion of new territory and of the extinction of aging
species
3. The Phylum Chordata
- King Philip Came Over From Great Spain
Subphylum Urochordata, Cephalochordata, Vertebrata 4.
Characteristics of the Vertebrates
- THE NOTOCHORD and VETERBRAL COLUMN
- NOTOCHORD - flexible rodlike structure ofmesodermalcells that
is the principal longitudinal structural element of chordates and
of the early embryo of vertebrates, in both of which it plays an
organizational role innervous system development . In later
vertebrate development, it becomes part of thevertebral column
5. 6.
- Nucleus Pulposus vestige/remnant of the notochord in mammals,
found within the interverebral disks
7. 8.
- 2. PHARYNX: pouches, slits and arches
- The pharynx is the region of the alimentary canal exhibiting
pharyyngeal pouches in the embryo
- Pharyngeal slits are permanent in adults that live in water and
breathe by gills (maximum number is 8)
9. 10. 11. 12.
- 3. DORSAL Hollow Central nervous System
- - Consists of brain and spinal cord.
13. 14. 15. 16. Vertebrate Body Plan
- TAIL persistent vs. vestigial
- APPENDAGES pectoral and pelvic, bilaterally symmetrical
17. 18. Concepts and Premises
- Phylogeny evolutionary history of a taxon (speciation)
- Ontogeny history of an individual (embryo development)
- "ontogeny recapitulates phylogeny,"- biogenetic law,Ernst
Haeckel (1834-1919)
- Many scientists are now questioning and in fact already saying
that this theory is false and inaccurate.
19. 20.
- English philosopherHerbert Spencerwas one of the most energetic
promoters of evolutionary ideas to explain many phenomena. He
compactly expressed the basis for a cultural recapitulation theory
ofeducationin the following claim, published in 1861, five years
before Haeckel first published on the subject
21.
- The maturationist theory of G. Stanley Hall was based on the
premise that growing children would recapitulate evolutionary
stages of development as they grew up and that there was a
one-to-one correspondence between childhood stages and evolutionary
history, and that it was counterproductive to push a child ahead of
its development stage
22.
- The Austrian neurologistSigmund Freudalso held a favorable
position towards Haeckel's doctrine. He was trained as a biologist
under the influence of recapitulation theory at the time of its
domination, and retained aLamarckianoutlook with justification from
the recapitulation theory. He also distinguished between physical
and mental recapitulation, in which the differences would become an
essential argument for histheory of neuroses
23. Taxonomy
- the science which deals with the study of identifying,
grouping, and naming organisms according to their established
natural relationship.
- Systematics taxonomy and the study of the evolutionary
processes that give rise to new taxa
24. 25. Convergent and Parallel Evolution
- Convergent applied when two or more unrelated species occupying
the same kind of environment, concurrently or millions of years
apart, develop a similiar adaptive morphologic trait.
26. 27.
- Parallel development of similar structures in recently related
but isolated taxa whose common ancestor lacked such traits.
28. 29. Natural Selection 30. Promise yourself to live your life
as a revolution and not just a process of evolution. - Anthony J.
D'AngeloEND OF PART ONE 31. Early Verterbrate Morphogenesis Part
twoLecture on Introduction to Comparative Anatomy 32. 33. Egg
Types
- Microlecithal very little yolk (e.g. placental mammal)
- Mesolecithal moderate amounts of yolk (e.g. amphibians)
- Macrolecithal massive amounts of yolk (e.g. reptiles,
birds)
- Isolecithal yolk is evenly distributed
- Telolecithal cytoplasm and yolk tend to accumulate at opposite
poles
34. Review of the Animal Cell 35. Review of Mitosis 36. 37. 38.
Review of Genetics
39.
40. DNA is the template for Protein Synthesis
-
- Structural Purposes (muscle, bone, etc)
-
- Regulatory Purposes (hormones)
41. Step 1: Transcription 42. STEP 2: Initiation 43. STEP 3:
ELONGATION/TRANSLATION 44. STEP 4: TERMINATION 45. 46. Oviparity
vs. Viviparity
- Oviparous animals that spawn or lay their eggs
- Viviparous animals that retain their eggs within the mothers
body during embryonic development
- Histotrophic nutrition nutrition by glandular secretions from
maternal tissues
47. Fertilization 48.
- At fertilization, enzymes in the acrosome of the sperm help to
penetrate the egg
-
- requires that the sperm break through the plasma and vitelline
membrane surrounding the egg
-
- to prevent more than one sperm from penetrating the egg
(polyspermy), the egg undergoes a cortical reaction to bring the
sperm head into the interior of the egg and change the vitelline
envelope to form the fertilization membrane
49.
- Just after fertilization the zygote (fertilized egg) undergoes
cleavage (mitotic cell divisions) and becomes subdivided into
smaller cells - the gross arrangement of cells differs greatly
among vertebrates, depending on the amount of yolk in the egg
50.
- Holoblastic cleavage occurs when the cleavage furrows pass
through the entire egg
-
- cleavage can either be equal, where the resulting cells contain
the same amount of yolk, or unequal, in which some cells contain
more yolk than others:
-
-
- - equal cleavage occurs in microlecithal eggs
-
-
- - unequal cleavage occurs in mesolecithal eggs
-
- cleavage results in the formation of a ball of cells
(blastomeres) surrounding an internal cavity (blastocoel)
51.
- Meroblastic cleavage occurs more in macrolecithal eggs
-
- cleavage takes place only in a disk at the animal pole
-
- the cleavage furrows do not extend into the yolk
-
- results in the formation of the blastodisk that lies on the top
of the yolk
52. 53. Morula
- a collection of around 30 cells (blastomere), is created at
about 96 hours. Because these cells arise only through the cleavage
of the zygote and all are found inside the pellucid zone, which
cannot expand, no growth is seen
54.
- On the 4th day after insemination the outermost cells of the
morula that are still enclosed within the pellucid zone begin to
join up with each other (so-called compaction). An epithelial
cellular layer forms, thicker towards the outside, and its cells
flatten out and become smaller.
55.
- The cells contact one another by means of tight junctions and
gap junctions. A cavity forms in the interior of the blastocyst
into which fluid flows (the so-called blastocyst cavity). The two
to four innermost cells of the preceding morula develop into the
so-called inner cell mass of the blastocyst. The actual embryo will
develop solely from these cells (embryoblast). These cells are
concentrated at one pole, the embryonic pole of the
blastocyst.
56.
- What has thus been formed is an outer cell mass (the
trophoblast), consisting of many flat cells, and the embryoblast,
formed from just a few rounded cells. The ratio between the number
of embryoblast cells to those making up the trophoblast amounts to
roughly 1:10. From the trophoblast the infantile part of the
placenta and the fetal membranes will arise
57. HATCHING
- Around the end of the fifth day the embryo frees itself from
the enveloping pellucid zone. Through a series of
expansion-contraction cycles the embryo bursts the covering. This
is supported by enzymes that dissolve the pellucid zone at the
abembryonic pole.
- The rhythmic expansions and contractions result in the embryo
bulging out of and emerging from the rigid envelope.
58.
- Trophoblast (outer cell mass)
- Hypoblast (part of the inner cell mass)
- Epiblast (part of the inner cell mass)
59. Migration of the Embryo of the Fallopian Tube
- Spermatozoon penetrates into the oocyte (conception), day
0
- Morula (16-32 cells), day 4
- Free blastocyst (following hatching), day 6
60.
- While the fertilized oocyte develops into a morula and
blastocyst and then hatches from the pellucid zone, it wanders from
the ampulla through the fallopian tube into the uterine cavity,
where it embeds itself in the endometrium at the end of the sixth
day. The fertilized oocyte / embryo is transported via the movement
of the cilia of the tubal epithelium and the contractions of its
muscular layer.
61. Gastrulation
- characterized by cell movement and reorganization within the
embryo (morphogenetic movements) to the interior of the embryo,
forming three primary germ layers:
- ectoderm, mesoderm, and endoderm.
62. 63. Neurulation
- the chordamesoderm that will go to form the notochord induces
neural plate formation, which is the first stage in the formation
of the neural tube
64.
- characterized in most vertebrates by three stages
- - during the neural plate stage, the ectoderm on the dorsal
side of the embryo overlying the notochord thickens to form the
neural plate
- - at the neural fold stage, the thickened ectoderm folds,
leaving an elevated area along the neural groove. The neural fold
is wider in the anterior portion of the vertebrate embryo, which is
the region that will form the brain.
- - during the neural tube stage, the neural folds move closer
together and fuse - the neural groove becomes the cavity within the
neural tube, which will later be capable of circulating
cerebrospinal fluid that aids in the function of the central
nervous system.
65.
- One derived characteristic found in vertebrates is the
formation of neural crest cells
-
- develop along the top of the neural tube as the neural folds
close
-
- most neural crest cells change into mesenchyme, an embryonic
tissue that consists of star-shaped cells from all three germ
layers
-
- develop into the visceral skeleton (i.e. gill arches, some of
which will develop into jaws), pigment cells, sensory and
postganglionic neurons, the dentine-producing cells of teeth,
Schwann cells that help protect neurons, and bony scales
66. Organogenesis
- After the production of the nerve tube, differentiation of the
germ layers occurs rapidly, and organogenesis begins, in which the
primary tissues differentiate into specific organs and tissues
67.
- Endoderm - gives rise to the epithelium of the alimentary
tract, to structures derived from the pharyngeal pouches such as
parathyroid glands, thymus gland, Eustachian tube and middle ear
cavity (not the ossicles), and to structures that develop as an
evagination of the gut, such as the thyroid gland, lungs or swim
bladder, liver, gall bladder, pancreas, and urinary bladder.
68.
- Mesoderm - becomes organized into three regions: the epimere
(dorsal mesoderm), mesomere (intermediate mesoderm), and hypomere
(lateral mesoderm).
-
- - Epimere: The somites constitute most of the dorsal mesoderm
and have three regions:
-
-
- dermatome - forms the dermis of the mid-dorsal skin
-
-
- sclerotome gives rise to the vertebrae
-
-
- myotome forms skeletal muscles other than those of the gill
arches
69.
- - Mesomere: gives rise to the kidney tubules, excretory organs,
and reproductive ducts.
- - Hypomere: lateral-plate mesoderm is confined to the trunk and
is divided into somatic mesoderm (parietal peritoneum) and
splanchnic mesoderm (visceral peritoneum, mesenteries, heart and
associated structures, lymphatic system, gonads and visceral
muscles)
70.
- Ectoderm - gives rise to Neural tube
-
- Epidermis and associated glands
-
- Neural crest and its derivatives: migrate through the embryo,
giving rise to a diversity of structures
-
- Ectodermal placodes: localized thickenings that sink below the
surface and give rise to sensory neurons and sensory structures:
olfactory placodes, forming the olfactory sacs; lens placodes, for
the lens of the eye; otic placodes, to become the membranous
labyrinth; a group of placodes that contributes neurons to the
sensory ganglia of cranial nerves V, VII, VIII, IX, and X; and
last, placodes that form the neuromasts of the cephalic and lateral
line canals
71. The Mammalian Egg
- the mammalian egg does contain some yolk, but it is
microlecithal and isolecithal - requires that the embryo implant
quickly in order to obtain more nutrients from the mother.
72. 73.
- The endometrium consists of a single-layered prismatic
epithelium with or without cilia (depending on how far along the
menstruation cycle is) and its basal lamina, uterine glands, and a
specialized, cell-rich connective tissue (stroma) containing a rich
supply of blood vessels.
74.
75.
- Epithelium of the uterine mucosa
76.
77.
- Hypoblast growing ventrally
- Eroded maternal capillaries
- Lacunae, filled with blood
78. 79. Overview of Human Development
- Gametogenesis formation of Sperm (male) and Ovum (Female)
-
- primordial germ cellspermatogonia primary spermatocyte
secondary spermatocytes spermatid spermatozoa
-
- Sertoli cells (support cells) Interstitial cells or Leydig
cells (produce hormone)
80. 81.
- Ovarian Follicle Stage:primordial follicleprimary
folliclesecondary follicletertiary folliclepreovulatory
follicle
82. Fertilization
- Fertilization usually occurs in first 1/3 of uterine tube
(oviduct, Fallopian tube)
- Fertilization can also occur outside uterine tube associated
with In Vitro Fertilization (IVF, GIFT, ZIFT...) and ectopic
pregnancy
- The majority of fertilized eggs do not go on to form an
embryo
83. 84.
- Sperm Binding - zona pellucida protein ZP3 acts as receptor for
sperm
- Acrosome Reaction - exyocytosis of acrosome contents (Calcium
mediated) MBoC - Figure 20-31. The acrosome reaction that occurs
when a mammalian sperm fertilizes an egg
-
- enzymes to digest the zona pellucida
-
- exposes sperm surface proteins to bind ZP2
-
- Membrane Fusion - between sperm and egg, allows sperm nuclei
passage into egg cytoplasm
85.
- Membrane Depolarization - caused by sperm membrane fusion,
primary block to polyspermy
- Cortical Reaction - IP3 pathway elevates intracellular Calcium,
exocytosis of cortical granules MBoC - Figure 20-32. How the
cortical reaction in a mouse egg is thought to prevent additional
sperm from entering the egg
-
- enzyme alters ZP3 so it will no longer bind sperm plasma
membrane
- Meiosis 2 - completion of 2nd meiotic division
-
- forms second polar body (a third polar body may be formed by
meiotic division of the first polar body)
86. 87.
88. 89. 90.
- http://embryology.med.unsw.edu.au/
- http://www.shsu.edu/~bio_mlt/Chap5.html
- http://www.embryology.ch/indexen.html
91. END OF LECTURE
- "Let us so live that when we come to die even the undertaker
will be sorry. Mark Twain