Theme 7 Flashcards
What are the Phases of Animal Development?
- Gametogenesis
- Fertilisation
- Cleavage
* Cell division in early embryo - Gastrulation
- Important in whether the pregnancy terminates or not
- Formation of germ layers
- Organogenesis
- Growth
- Birth (or hatching)
- Juvenile phase
- Maturity
- Senescence &death
What are the Early stages of Mammalian Development?
- Fertilisation
- Cleavage
- Blastocyst formation
- Implantation
- Bilaminar embryo
- Gastrulation
- Trilaminar embryo
Stages of Development
- What time period is the Pre-Embryonic period?
- What time period is the Embryonic period?
- What time period is the Foetal period?
- Before birth,*
1. Week 2
2. Week 2 - 8
3. Week 9 - birth
What is Fertilisation?
What is the process of Fertilisation?
As as a result of Fertilisation, what occurs? - Consequences
Start of development
Process:
- Spermatozoa penetrates corona radiata
- Spermatozoa penetrates zona pellucida
- Fusion of oocyte & sperm membranes = zygote
- Cortical and zona reactions -Zona pellucida hardens to prevent more sperm entering Resumption of 2nd meiotic division
- Metabolic activation of the egg
Consequences:
- Restores diploid chromosome number
- Determines the sex
- Cleavage begins
During the Pre-Embyronic period, what events occur?
- Fertilisation
- Cleavage
- Morula= 16 cells
- Blastocyst formation= 4 days
- Zona pellicular breaks down
- Inner cell mass forms the organism
- Outer cells form trophoblast layer
- Implantation
- Formation of bilaminar embryo
What events occurs during the Embryonic period?
- Further development of bilaminar embryo
- Gastrulation
- Transformation to trilaminar embryo
What events occurs during iImplantaiton?
Day 7: blastocyst implants on the uterine stroma
- A blastocyst is a bilaminar embryo
- Two cell layers (epiblast & hypoblast) with cavities either side (amnion & primitive yolk sac
What are the three layers of the Trilaminar Embryo?
Epiblast layer: forms the primitive streak
- Cells develop underneath it as the mesoderm
Ectoderm: formed from the epiblast
- Forms the neural tube & crest at 21 days
Endoderm: formed from the hypoblast
Ectodermal Germ Layer
- What are the deriviatives?
- Define Neuralation.
- What forms after neuralation ends?
4.
- Derivatives: nervous system, mucosa, skin epidermis & sensory epithelia of nose, ear & eye
-
Neuralation: folding process in embryos
- arising nervous system
- resulting in the formation of the neural tube & crest.
- Neural tube: brain & spinal cord
- Neural crest: peripheral nervous system
- Epidermis
What are the two divisions of the Mesodermal Germ Layer?
What does each division segmentate into?
What’s the differences between both divisions?
- Mesoderm of Trunk - 3 divisions
- Paraxial mesoderm
- Intermidiate mesoderm
- Lateral Plate mesoderm
- Mesoderm of Head - 2 divisions & 2 origins
- Paraxial mesoderm
- Lateral Plate mesoderm
Mesoderm of Trunk
What are the divisions of the Paraxial Mesoderm?
What anatomical structure does each segmented mesoderm form?
Paraxial mesoderm:
- Sclerotome: forms vertebrae
- Myotome: forms skeletal muscles
- Dermatome: forms dermis
Intermediate mesoderm: urogenital system
Lateral plate mesoderm: muscles, connective tissue & viscera
Mesoderm of Head
What are the 2 origins of the mesoderm of head cells?
What anatomical structure do the cells from each origin form?
Neural crest: facial skeleton & connective tissue lining the great vessels of the head & neck
Mesoderm: dermis, muscle, rest of skull & mesoderm lining the body cavity and viscera
Endodermal Germ Layer
What anatomical structure does it form?
What are the conditions required for it to form the derivative?
Forms GI tract
What are the Cranial Nerves & Muscular Derivatives of Pharyngeal Arches?
- V2 & V3 - Muscles of mastication, anterior digastric, mylohyoid, tensor veli palatini & tensor tympani
- VII - Muscles of facial expression, posterior digastric, stylohyoid & stapedius
- IX - Stylopharyngeus
4/6. X&XI - Muscles of pharynx, soft palate & larynx
What are the Skeletal Derivatives of Pharyngeal Arches?
- Meckel’s cartilages, maxillary & mandibular processes, malleus & incus
- Styloid process, Lesser cornu and upper part of the body of hyoid & stylohyoid ligament
- Greater cornu of hyoid & lower part of body of hyoid
4/6. Cartilages of laryngeal framework
