1. Ch 47 Fertilization through organogenesis
Animal Development
Ch 47 Fertilization through organogenesis

2. Stages of Human Development
Fertilization
Zona pellucida
First cell division
Cleavage
Blastomere
Holoblastic cleavage
Meroblastic cleavage
regulation
Morophogenesis
Gastrulation
Organogenesis

3. Fertilization
Female secretions increase sperm motility and change structure to cause fertilization potential (capacitation) Moist environment necessary for sperm First six hours

4. Fertilization
Zona pellucida contain receptor cite and acrosomal reaction which binds sperm to egg Changes cause slow polyspermy to prevent additional sperm from entering egg No fast polyspermy reactions in mammals

5. Zona pellucida Follicle cell Sperm nucleus Cortical granules
Figure 47.5
Zona pellucida
Follicle cell
Figure 47.5 Fertilization in mammals.
Sperm nucleus
Cortical granules
Sperm basal body

6. Fertilization
First Cell Division Mitosis forms true nuclei in daughter cells hours after sperm bonding Each cell is now a blastomere embryonic development

7. Cleavage
Rapid cell division with almost continuous S and M phases of cell cycle Little or no protein synthesis (G1 or G2) Blastula- Hollow ball of cells form with blastocoel cavity

8. (a) Fertilized egg (b) Four-cell stage (c) Early blastula
Figure 47.6
50 m
(a) Fertilized egg
(b) Four-cell stage
(c) Early blastula
(d) Later blastula
Figure 47.6 Cleavage in an echinoderm embryo.

9. Cleavage
In frogs and mammals is holoblastic “holo” means complete Humans have 3 divisions in first three days with little yolk forming Birds and reptiles cleavage is meroblastic (incomplete) to get extensive yolk formation The “ends” of the blastula are called the animal pole and vegetal pole Gray crescent is the area on the opposite side from sperm binding

10. 8-cell stage (viewed from the animal pole)
Figure 47.7
Zygote
2-cell stage forming
Gray crescent
0.25 mm
8-cell stage (viewed from the animal pole)
4-cell stage forming
Animal pole
8-cell stage
Figure 47.7 Cleavage in a frog embryo.
0.25 mm
Blastula (at least 128 cells)
Vegetal pole
Blastocoel
Blastula (cross section)

11. Regulation of Cleavage
The total mass of the structure does not change from zygote to blastula, the cells just get smaller Cells divide until the ratio of material in each nucleus to cytoplasm is sufficiently large Small cells balance the amount of DNA to mRNA for protein synthesis (think surface are to volume ratio)

12. Morphogenesis Transformation of embryo orientation and shape
Important is the cell shape, position and survival
Two important phases:
Gastrulation- establishment of cell layers
Organogenesis- formation of organs

13. Morphogenesis: Gastrulation
During gastrulation there is a mass movement of cells which results in the blastula becoming a gastrula Three germ layers develop ectoderm- outside layer mesoderm- middle layer endoderm- inside layer Some organisms (cniderians) do not have a mesoderm HHMI Differentiation and Cell Fate cells

14. ECTODERM (outer layer of embryo)
Figure 47.8
ECTODERM (outer layer of embryo)
• Epidermis of skin and its derivatives (including sweat glands, hair follicles)
• Nervous and sensory systems
• Pituitary gland, adrenal medulla
• Jaws and teeth
• Germ cells
MESODERM (middle layer of embryo)
• Skeletal and muscular systems
• Circulatory and lymphatic systems
• Excretory and reproductive systems (except germ cells)
• Dermis of skin
• Adrenal cortex
Figure 47.8 Major derivatives of the three embryonic germ layers in vertebrates.
ENDODERM (inner layer of embryo)
• Epithelial lining of digestive tract and associated organs (liver, pancreas)
• Epithelial lining of respiratory, excretory, and reproductive tracts and ducts
• Thymus, thyroid, and parathyroid glands

15. Gastrulation in Sea Urchin
Figure 47.9
Animal pole
Blastocoel
Mesenchyme cells
Gastrulation in Sea Urchin
Vegetal plate
Vegetal pole
Blastocoel
Filopodia
Mesenchyme cells
Archenteron
Blastopore
Figure 47.9 Gastrulation in a sea urchin embryo.
50 m
Blastocoel
Ectoderm
Archenteron
Key
Blastopore
Mouth
Future ectoderm
Mesenchyme (mesoderm forms future skeleton)
Digestive tube (endoderm)
Future mesoderm
Anus (from blastopore)
Future endoderm

16. Gastrulation in Frog SURFACE VIEW CROSS SECTION Animal pole 1
Figure 47.10
SURFACE VIEW
CROSS SECTION
Animal pole 1
Blastocoel
Gastrulation in Frog
Dorsal lip of blasto- pore
Dorsal lip of blastopore
Blastopore
Early gastrula
Vegetal pole 2
Blastocoel shrinking
Archenteron
Figure Gastrulation in a frog embryo.
Ectoderm 3
Blastocoel remnant
Mesoderm
Endoderm
Key
Future ectoderm
Blastopore
Future mesoderm
Late gastrula
Yolk plug
Archenteron
Blastopore
Future endoderm

17. Migrating cells (mesoderm) Endoderm Hypoblast
Figure 47.11
Fertilized egg
Primitive streak
Gastrulation in Chick
Embryo
Yolk
Primitive streak
Epiblast
Future ectoderm
Figure Gastrulation in a chick embryo.
Blastocoel
Migrating cells (mesoderm)
Endoderm
Hypoblast
YOLK

18. Gastrulation in Human Figure 47.12
Blastocyst reaches uterus.
Endometrial epithelium (uterine lining)
Gastrulation in Human
Inner cell mass
Uterus
Trophoblast
Blastocoel 2
Blastocyst implants (7 days after fertilization).
Expanding region of trophoblast
Maternal blood vessel
Epiblast
Hypoblast
Trophoblast
Expanding region of trophoblast 3
Extraembryonic membranes start to form (10–11 days), and gastrulation begins (13 days).
Amniotic cavity
Epiblast
Hypoblast
Yolk sac (from hypoblast)
Extraembryonic mesoderm cells (from epiblast)
Figure Four stages in the early embryonic development of a human.
Chorion (from trophoblast) 4
Gastrulation has produced a three-layered embryo with four extraembryonic membranes.
Amnion
Chorion
Ectoderm
Mesoderm
Endoderm
Yolk sac
Extraembryonic mesoderm
Allantois

19. Morphogenesis: Gastrulation in Humans
1. Blastocyst first 6 days Fertilization occurs in the oviduct Inner cell mass becomes the embryo which is the source for stem cells Little yolk (stored nutrients)
Inner cell mass
Blastocyst reaches uterus.

20. Morphogenesis: Gastrulation in Humans
2. Trophoblast 7 days after fertilization Outer epithelium secretes enzymes for implantation which allows for blood to surround trophoblast Epiblast-upper layer becomes the embryo Hypoblast- lower layer
Maternal blood vessel

21. Morphogenesis: Gastrulation in Humans
3. Extraembryonic membranes days Formed by embryo Enclose special structures outside the embryo Gastrulation begins day 13 when implantation is complete Cell migration occurs as cells move inward from epiblast through primitive streak to form mesoderm and endoderm
Chick gastrulation

22. Expanding region of trophoblast
Figure 47.12c
Expanding region of trophoblast
Amniotic cavity
Epiblast
Hypoblast
Yolk sac (from hypoblast)
Extraembryonic mesoderm cells (from epiblast)
Chorion (from trophoblast)
Figure Four stages in the early embryonic development of a human. 3
Extraembryonic membranes start to form (10–11 days), and gastrulation begins (13 days).

23. Morphogenesis: Gastrulation in Humans
4. End of gastrulation Three germ layers are formed Extraembryonic layers from placenta These layers are an evolutionary necessity in land (dry) environments

24. Extraembryonic mesoderm
Figure 47.12d
Amnion
Chorion
Ectoderm
Mesoderm
Endoderm
Yolk sac
Extraembryonic mesoderm
Allantois
Figure Four stages in the early embryonic development of a human. 4
Gastrulation has produced a three-layered embryo with four extraembryonic membranes.

25. Organogenesis Research brain intestine Spinal cord liver
More localized changes
Research
brain
intestine
Spinal cord
liver
Bones (or specific)
Muscles (or specific)
skin
eyes
heart
ears
HHMI