Introduction to Embryology (Embryology) Flashcards
Describe chronological events of week 1: Ovulation to blastocyst
- Ovulation = oocyte released
- Fertilization = sperm penetrates oocyte
- Cleavage = cells divide
- Morula = cells divide but no change in cell size
- Blastocyst = Zygote hatches from zona pellucida; water drawn inside to form sphere
- (Implantation = Trophoblast implants on wall)
Describe chronological events of week 2: implantation to bilaminar
- Trophoblast implants into wall
- Inner cell mass forms bilayer: Epiblast and hypoblast
Describe chronological events of week 3: gastrulation
Gastrulation = epiblast differentiates and fills the cavity between the epiblast and hypoblast with mesoderm cells.
Three germ layers are created:
- Ectoderm: neural tissue and skin; teeth and teeth support
- Mesoderm: muscle (skeletal and heart), and bone
- Endoderm: digestive system, respiratory tract and endocrine glands
- Heart beats at end of week 3
Main event of Week 4: ventral folding, neuralation and caudal folding?
Three germ layers fold into a tube-like structure
Describe the stages of neurulation and neural tube formation (Week 4)
1) Neural groove forms as neural folds converge
2) Neural plate (part of ectoderm) forms walls of groove
3) Neural folds merge together to create neural tube
4) Epidermis forms over tube
(Week 4) What are ‘neural crest cells’ and what are their functions?
Cells from neural plate border after closure.
- Following neural tube closure, neural crest cells migrate
- Neural crest cells become mesenchymal cell type
- Give rise to oral facial structure:
1) Dentine
2) Taste buds
3) Teeth/tooth support
Describe ‘caudal folding’ (Week 4)
Ends of embryo fold toward yolk sac:
1) Allows frontal-nasal prominence to grow
2) Positions heart in chest and in front of digestive tract
3) Creates primitive oral cavity
Pharyngeal arches begin to form what and in which week?
Week 4, they begin to form.
- Form major parts of neck and face
- Contain ectoderm and mesoderm
Define ‘epibranchial placodes’ (Week 4)
Specialized regions on surface of ectoderm that invaginate to form sensory ganglia
Define ‘clefts’ (Week 4)
Indentations that separate pharyngeal arches on external surface
Describe ‘pharyngeal pouches’ (Week 4)
Indentations that separate pharyngeal arches on Internal surface
Describe 1st Pharyngeal Arch
Muscles:
- Muscles of mastication
- Mylohyoid
- Anterior belly of digastric
- Tensor tympani
- Tensor palati
Nerve:
- Trigeminal nerve, V2 and V3
Bones/cartilage:
- Maxilla
- Meckel’s cartilage
Arteries:
- Maxillary artery
- External carotid artery
Tissue:
- Anterior tongue
Describe 2nd pharyngeal arch
Muscles:
- Muscles of facial expression
- Posterior belly of digastric
Nerves:
- Facial nerve
Bones:
- Hyoid bone
- Temporal bone
Describe 3rd pharyngeal arch
Nerves:
- Glossopharyngeal nerve
Arteries:
- Common carotid artery
- Internal carotid artery
Describe 4th/5th pharyngeal arch
Nerve:
- Vagus nerve
Cartilage:
- superior parathyroid epiglottic cartilage
Tissue:
- Thyroid
