Embryology 2 Flashcards
Before the placenta is formed and can take over, what provides nutrition and gas exchange between the mother and the developing embryos the fetus to move freely within the walls of theuterus?
the yolk sac
What does the primitive streak consist of?
- groove- primitive groove
- depression- primitive pit
- mound- primitive node
What does the Ectoderm become?
Epidermis and CNS
What does Mesoderm become?
Musculoskeletal; Cardiovascular and Urogenital Systems
What does Endoderm become?
Lining of GI and Respiratory tract
What is theembryonicprecursor to thecentral nervous system, which is made up of thebrainandspinal cord?
The neural tube
What is Sclerotome?
results in bone or other skeletal tissue
What is Myotome?
group of muscles which a single spinal nerve innervates
What is dermatome?
area of skin mainly supplied by a single spinal nerve
The embryoblast differentiates into two layers called?
Epiblast and Hypoblast
What is the name of membrane inbetween the epiblast and hypoblast?
bilaminar germ disc
What is the epiblast?
cell layer of the embryonic disc that forms three primary germ layers, amniotic ectoderm and extraembryonic mesoderm.
What is the hypoblast?
second layer of the embryonic disc that forms the yolk sac
What does the epiblast become when the intraembryonic mesoderm and endoderm have formed?
Ectoderm
What does the hypoblast become as it matures?
Endoderm
What is the definition of mesoderm?
One of the three germ layers of bilaterally symmetrical animals, found in the early embryo between the ectoderm and endoderm
What is the definition of Mesenchyme?
Is an undifferentiated tissue found in embryonic true mesoderm.
What does the central neural tube become?
Spinal chord
As the mesoderm matures, they form cylindrical structures, what are they?
paraxial - will form axial skeleton, voluntary muscle and portion of the dermis
intermediate - forms urinary tract and parts of the genital system
lateral mesodermal condensations - these form into 2 portions on day 17
What is neurolation?
Formation of the neural tube
What does the neural crest differentiate into?
Cranial nerves
Somites lead to the segmental organisation of the body - true or false?
True
What do somites differentiate into?
Dermatome, Myotome, Scleratome
What do somites 1-4 differentiate into?
Occipital bone, bones around the eyes, nose and inner ears, extrinsic ocular muscles, muscles of the tongue
What do somites 2-12 differentiate into?
Cervical spine and upper limb
What do somites 13-15 differentiate into?
Thoracic spine and upper limb
What do somites 26-31 differentiate into?
lumbar spine, abdominal dermis and lower limb
What do somites 32-37 differentiate into?
sacral portion of the spine
If there are problems with maturation of the somites, what could happen?
Developmental abnormalities
Caudal regression- Abnormal folding in caudal region during gastrulation leads to a variety of abnormalities depending upon the degree. Possible problems include:
Lower limb malformation due to embryo flexion, rotation and inversion
Anomalies of the lumber and sacral vertebra
Imperforate anus
Agenesis of the kidneys, urinary tract and/or genital organs (except the gonads)
Extreme case-sirenomelia-fusion of the lower limbs
What condition could be caused from poor induction from one side?
structural scoliosis, faulty vertebral body formation
What condition could be caused from Poor induction of neural tube at cranial end?
anencephaly (survival unlikely)
What condition can be caused from poor induction of the neural tube?
Spina Bifida
What condition could be caused from faulty contact with the ectoderm?
Failure of fusion of vertebral arches
What condition can be caused from undifferentiated neural tube tissue-undifferentiated mass of tissue in the lower region of the neural tube?
Rachischisis/myeloschisis
