Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Embryonic folding
Organisation of the Body
| Question | Answer |
|---|---|
| Early embryology processes | Axis formation Gastrulation Neurulation Segmentation Embryonic folding |
| Presence of erythrocytes and primordial germ cells | Can sequence transcriptome - investigate proteins in a cell to see cell type Can map out each individual cell based on its proteins and their similarity Shows presence of germ cells and erythrocytes of fetal origin |
| Organising the primary body axis | The primitive streak regressed in a cranial to caudal direction, laying down the notochord cranially The node, situated at the cranial end of the streak organises the primary body axis in a cranial to caudal sequence and controls left right asymmetry |
| Nodal cilia responsible for L-R asymmetry | Cells of the node have prominent cilia These rotate, producing flow The cilia are tilted, so flow is linear not a vortex Fluid flows from one side to the other generating asymmetry Fluid moves leftwards |
| Evidence for nodal cilia controlling L-R asymmetry | By artificially determining the direction of flow you can change situs Normal flow = normal symmetry Reversed flow = situs inversus |
| Nodal flow causes asymmetric gene expression | Cilia at the apex to dot move - they detect flow direction Elevated calcium on left side influences gene expression E.g. Pitx2 is a left specific gene Heart folding is due to asymmetric proliferation etc due to this asymmetrical gene expression |
| Situs inversus | Caused by a single point mutation in dynein axonemal heavy chain 11 Results in defective nodal cilia Model for primary ciliary dyskinesia - Kartagener syndrome |
| Embryonic folding | Converts the flat trilaminar germ disc into a 3D cylindrical structure Folds caudally, rostrally and laterally Three layers meet at the belly button |
| Process of folding | Vigorous growth of the embryonic disc and amnion, and very little growth in the yolk sac Rostral and caudal folding is due to the expansion of the neural tube Dorsal axis is stiffened by axial structures Lateral folding as amnion surrounds embryo |
| Rostral folding | Moves structures ventrally Ventral movement of septum transversum Buccopharyngeal membrane Cardiogenic region Primitive pericardial cavity |
| Caudal folding | Caused primarily by growth of the developing spinal cord The cloacal membrane (urogenital opening and anus) and the allantois (part of the bladder) move ventrally Leads to formation of the hindgut tube |
| Lateral folding | Results in ventral movement of lateral plate mesoderm Leads to formation of intraembryonic coelom (splitting of LPM) Gut tube forms as a result of the change of shape of the yolk sac The amnion id filled with amniotic fluid and collapses around embryo |
| Ectodermal gut tube | The yolk sac starts to look like a goldfish bowl but as the gut tube forms the neck narrows to form the vitelline duct At the rostral end the tube forms the foregut and at the caudal end the hindgut These end in the buccopharyngeal and cloacal membranes |
| Gut tube suspended in the coelomic cavity | The gut tube is surrounded by splanchnic mesoderm The body wall is lined internally by somatic mesoderm The gut tube is suspended from the dorsal body wall by the dorsal mesentery |
| Congenital defects in ventral body wall | Defects in folding can lead to failure of the ventral body wall to form properly Can lead to abdominal contents herniating beyond ventral body wall Omphalocele - organs are membrane covered Gastroschisis - organs not covered |
| Formation of the amniotic cavity | As the gut tube forms the two sides of the amnion can now meet in the midline and fuse to form the ventral body wall The amnion now surrounds the entire embryo - it is continuous with embryonic ectoderm |
| Formation of the umbilical cord | Embryonic folding and expansion of the amniotic cavity leads to the formation of the umbilical cord The chorionic cavity is eventually filled by the expanding amniotic cavity |
| The end point of folding | Ventral body wall is complete Heart is in the correct thoracic position The gut is a tube with the yolk sac attached via the vitelline duct, a buccopharyngeal membrane at the rostral end and a cloacal membrane at the caudal end |
| Divisions of intraembryonic coelom | Divided into two regions by the diaphragm Pericardial cavity - thoracic region Peritoneal cavity - abdominal |
| Septum transversum | Appears at day 22 Bar of mesoderm lying rostral to the cardiogenic region Rostral folding carries it ventrally so it wedges between the cardiogenic region and neck of yolk sac Causal translocation of phrenic nerve Forms initial partition in body |
| Role of septum transversum | Separates developing thorax and abdomen Attaches to anterior body wall lateral body wall and oesophageal mesentery |
| Pericardioperitoneal canals | Two spaces at dorsolateral edge of the septum transversum Left larger than right due to asymmetry |
| The pleural cavity | The pericardial cavity is partitioned into the pericardial and pleural cavities by outgrowth of the pleuropericardial folds from the body wall |
| Formation of the pericardium | Pleuropericardial folds grow and fuse medially subdividing the primitive pericardial cavity into a definitive pericardial cavity and two pleural cavities The root of the pleuropericardial folds then migrate around to the anterior body wall |
| Formation of the diaphragm | Septum transversum - amuscular central tendon Periocardioperitoneal canal closed by pleuroperitoneal membranes - posterior musculature Dorsal oesophageal mesentery give rise to diphragmatic crura Body wall-circumfrential muscular rim |
| Location of vessels | Aorta - behind main diaphragm at T12 Oesophagus - through muscular part at T10 IVC - through central tendon at T8 |
| Innervation of diaphragm | Phrenic nerve - C3,4,5 This is due to rostral origin and subsequent caudal displacement of septum transversum during development |
| Congenital diaphragmatic hernias | Failure to close pleuroperitoneal canals causes congenital diaphragmatic hernias Herniation of abdominal contents into thoracic cavity - more common on left side as canal is larger so fails to close more often |
| Endodermal origin of lungs | Form in 4th week - small diverticulus of foregut at level of oesophagus Grow into pleural cavities Shows L-R asymmetry Primary branching - 28 days forms left and right brinchi Secondary branching - 3o days 3 branches on right and 2 on left |
| Formation of terminal bronchioles | By 6th week branching has formed 10 bronchopulmonary segments By 16th week respiratory tree produces terminal bronchioles |
| Tracheoesophageal Fistula | Defects in separation of the traches and oesophagus can leas to congenital abnormalities |
Created by:
12345678987654321000000
Popular Medical sets