Flashcards in Development 1 Deck (42)
What is a congenital disorder?
a structural disorder or functional disorder present at birth due to a problem with genes, chromosomes, intrauterine environment, teratogens or metabolic requirement
What is the frequency of birth defects?
What is the most common birth defect?
heart defect - 1/200
What is a morula?
A 16 cell ball at around 3 days
What is a blastocyst?
A cell mass with a cavity (blastocoele) at 4 days
What are trophoblasts?
The cells around the outside of the blastocyst that will make up the extra embryonic structures
What is the inner cell mass?
The cells at one pole of the blastocyst that will end up making the embryo
When does the blastocyst implant on the wall of the uterus?
What happens at the two germ layer stage?
The inner cell mass splits into the epiblast and the hypoblast - the epiblast will form the embryo and the hypoblast is extra embryonic
What is the cavity formed by the epiblast?
The amniotic cavity
What is the cavity formed by the hypoblast?
The yolk sac
What happens at the three germ layer stage?
The epiblast forms 3 layers by gastrulation - endoderm, mesoderm and ectoderm
What does the ectoderm give rise to?
The nervous system and the epidermis
What does the mesoderm give rise to?
Blood cells, heart, kidneys, gonads, connective tissue (bone and muscle)
What does the endoderm give rise to?
The epithelial lining of hollow organs (gut, lungs, liver)
What is the notochord?
The first identifiable structure - a stiffened rod that runs down the midline and organises tissues around it
What happens to the ectoderm above the notochord?
It forms the neural plate which will form a neural tube to form the CNS
What is the neural crest?
The cells at the top of the neural tube which will form parts of the nervous system that aren’t part of the CNS e.g. enteric ganglia, sympathetic ganglia etc but will also form non neuronal cells like the muscle, cartilage and bone of the skull, jaws, face and pharynx and melanocytes and dentine
What causes a cleft lip and palate?
failure of the neural crest to migrate forward and meet at the midline
What are the derivatives of the mesoderm?
dermis, muscles, skeleton, urogenital tract, heart and blood vessels, wall of gut and respiratory tract, hemopoietic tissue, pleura, peritoneum, pericardium
What are the 3 separate zones of the mesoderm?
paraxial mesoderm (closest to the notochord), lateral mesoderm (further from the notochord), intermediate mesoderm (in between)
What does the intermediate mesoderm become?
The urogenital system
What does the paraxial mesoderm become?
the axial skeleton, muscles attached to the axial skeleton and limbs, the dermis of the skin
What does the lateral mesoderm become?
The muscle of the body wall, the skeleton of the limb, the pleural and peritoneum, blood, heart, walls of gut and respiratory tissues
What are somitomeres?
swellings down the length of the paraxial mesoderm
What are somites?
A somitomere that has broken free
Where does the first somite appear?
At the 8th somitomere and then progressively down
What does the somite split into?
sclerotome and dermomyotome
What does the dermomyotime slit into?
The dermatome and myotome
What does the sclerotome become?
the bones of the axial skeleton
What does the dermatome become?
The dermis of the skin
What does the myotome become?
back muscle and limb muscle
What are pharyngeal arches?
When does limb development begin?
At the end of the 4th week
What is limb growth initiated by?
What is the limb field?
a patch of mesoderm - the central region gives rise to the limb and the peripheral region gives rise to the shoulder girdle and flank tissue
What is limb growth continued by?
What causes diplopodia?
splitting of the ectodermal ridge controlling limb growth
What causes the sculpting of digits?
What causes syndactyly?
failure of apoptosis
What is the commonest limb abnormality?
congenital hip dislocation caused by malformation of the acetabulum