Embryology Flashcards
Embryonic period
From fertilization to end of the 8th week of development.
All essential structures for speech and hearing form during this period.
Embryo
Organism in the early stages of growth and differentiation.
Zygote
A new cell formed from the union of the two gametes (egg and sperm). This is a newly fertilized egg. Continues to travel along the filopian tube as it starts to divide (cellular division called mytosis)
Mitosis
The process of the division of the chromosomes and then the division of the cytoplasm to form two new identical cells. Then the 2 cells divide into 4 cells, the 4 cells divide into 8 cells etc…
Morula
About the third day after fertilization. This is when the cell divides into 12 to 16 cells
Blastocyst
(changes from morula to…)When the cells will begin to separate into two masses.around the 5-7 day after fertilization. Implantation is completed after the 10th day.
Outer cell mass (trophoblast)- will become the placenta
Inner cell mass will become the embryo Attaches to the uterine lining
Etopic pregnancy
Egg implants in out of place area- not in uterus . Etopic means out of place…
Week 1
Egg released into filopian tubes, becomes fertilized-occurs in uterine tube 12-24 hrs after ovulation, Zygote, Mitotic cell division, Morula, and Blastocyst.
Week 2
Cell differentiation, Primary germ layers ( ectoderm:upper, Mesoderm: between:, Endoderm cells: lower)
Cell differentiation- what week does it begin?
Begins week 2, cells begin to become different than the one that created it by division.
Primary Germ Layers
Ectoderm: upper
Mesoderm:between
Endoderm:lower
Ectoderm Cells
Upper surface of primary germ layers. Will eventually develop into: Epidermis of the skin Teeth Nervous system Hair Nails Epithelial tissue
Mesoderm cells
Between layer of Primary germ layers.
Will eventually become:
Connective tissue: bones, muscles, blood vessels, cartilage
Endoderm cells
Lower layer of Primary Germ layers.
Eventually becomes:
Epithelial lining of digestive tract “Inner skin”
Epithelial lining of respiratory tract. “inner skin”
Week 3
Will begin to change from a round disk shape to a long tube or pear shape
Primitive Streak
Also referred to as the primitive line. Establishes a structural foundation for change along the longitudinal axis.
Hensen’s Node
Found along the primitive streak. Small area of proliferating cells. (in the bottom area on the diagram)
Neural Plate
Beginning of the nervous system.
Cells grow an thicken to form the neural folds.
Will give rise to all of the neurons and neuroglial cells (supporting cells of the entire nervous system. Then grows upward to form the neural folds.
Notochord
Along the midline of the neural plate- a strip of cells. Will eventually become the primitive axial skeleton.
Neural folds
Thickening along the lateral margins of the neural plate. Meet and fuse in the midline to form a tube.
Neural Tube
Formed when the neural folds meet a the midline and fuse.
WIll give rise to the entire central nervous system.
- brain and spinal chord.
Neural Crest
Ridge of ectodermal cells on either side of the neural tube.
- will become spinal and cranial nerve ganglia and ganglia of the sympathetic and automatic nervous system.
- also known as neural crest of the ganglion ridge.
Somites
Develop as the neural tube is formed. Blocks of tissue that resemble the vertebral column. Appears about the 16th day of development. Three groups: Sclerotome Myotome Dermotome
Sclerotome
Innermost part of a somite.
Will become individual vertebrae, intervertebral discs, and ribs.
Myotome
Lateral to the sclerotome- will become the musculature of the trunk.
also known as (myomere)
Dermatome
Most lateral portion of a somite.
Will become dermis.
Week 3 continued…
Flexion of the embryo begins at the end of the 3rd week.
Rapid growth causes the embryo to buckle, resulting in a series of folds.
Flexion of the Embryo
Begins at the end of the 3rd week. Rapid growth causes the embryo to buckle, resulting in a series of folds. Start of development of head, mouth and face.
Development of primitive mouth
Located between the forebrain and heart prominence.
Also known as (Stomoduem or oral groove).
Branchial Arches
Other grooves formed by flexation of the embryo
6 arches are formed but only 4 are visible externally. (2 can be seen on each side.)
Series of transverse elevations and depressions, grow together and meet at midline for for facial structures.
1st brachial Arch
Called the mandibular arch-grows together at midline of face and forms: lower lip muscles of mastication mandible Anterior portion of the tongue Some structures of the middle ear
2nd Brachial Arch
Also called Hyoid Arch. Develops as:
- Upper body and lesser horns of the hyoid bone
- Stapes
- muscles of facial expression
3rd Brachial Arch
no name given
Develops into:
lower body of the hyoid bone
Posterior portion of the tongue
4th and 5th Brachial arches
No special names
Develops into:
Cricoid and arytenoid cartilages of the larynx
Cartilages of the trachae
6th Branchial Arch
Sometimes called Caudal Arch
Forms:
Palatine muscles
Pharyngeal constrictors
Week 4 developments
Nasal pits
Arm and leg buds
Optic pit (start of ear)
Umbilical cord
4 weeks Brain Development
Brain is made up of 3 sections:
Prosencephalon: forebrain
Mesencephalon:midbrain
Rhombencephalon: hind brain
Prosensephalon
Prosencephalon: forebrain
4th week
Telencephalon->Cerebral hemisphere->lat ventricles
Prosencephalon
Thalamus
Diencephalon—–> 3rd vertical
Hypothalamus
Mesencephalon
Mesencephalon:midbrain
4th week
Mesencephalon-> Mesencephalon->midbrain-> Aqueduct
Rhombencephalon
Rhombencephalon: hind brain
4th week
Pons Upper portion Mentencephalon-> Celebellum pf 4th vent.
Rhombencephalon Myelencephalon-> medulla oblongata-lower portion of 4th vent
Progress of Prosencephalon from Three primary vesicles to 5 secondary vesicles
Telencephalon->Cerebral hemisphere->lat ventricles
Prosencephalon
Thalamus
Diencephalon—–> 3rd vertical
Hypothalamus
Mesencephalon from 3 primary vesicles stage to 5 secondary vesicle stage
Mesencephalon-> Mesencephalon->midbrain-> Aqueduct
Rhombencephalon from 3 primary vesicles stage to 5 secondary vesicle stage.
Pons Upper portion
Mentencephalon-> Celebellum pf 4th vent.
Rhombencephalon Myelencephalon-> medulla oblongata-lower portion of 4th vent
