Coelomic Cavity Origins and Formation Flashcards
What is the coelom?
The body cavity located between the alimentary canal and body wall.
What lines the coelom?
A layer of mesoderm
What is the coelom called in vertebrates?
The body cavity
Do acoelomates have an enclosed body cavity?
No
What are examples of parasitic acoelomates?
The liver fluke and cestodes.
What is the structure of the body cavity in acoelomates?
It has a layer of mesoderm derived muscle beneath the ectoderm layer and the space between the gut and body wall is filled with mesenchyme cells.
What is the structure of the body cavity in pseudocoelomates?
They have a fluid filled body cavity with a layer of mesoderm derived muscle around the body wall.
How are internal organs arranged in pseudocoelomates?
They are suspended in fluid with no attachment to the body wall. This is due to the absence of the mesodermal peritoneal membrane.
What are examples of parasitic pseudocoelomates?
Ascaris roundworm and hookworm
What is the structure of the body cavity in coelomates?
An enclosed body cavity develops as two layers of mesoderm. This is lined with mesodermal peritoneal membrane that surrounds the internal organs. Mesodermal derived muscle lines the body wall.
What separates the internal organs from the coelomic fluid in coelomates?
The peritoneum
What is the function of the coelom?
- Provides space for 3D growth of organs
- Provides protective environment for organs of the body cavity
- Allows some muscle groups to grow independently of the body wall
What is the function of coelomic fluid?
- Supports growth and movement of internal organs
- Provides medium for the movement of immune cells
- Acts as a hydroskeleton which supports movement in (invertebrates)
- Facilitates transport of gases, nutrients and waste in invertebrates
How is a spiral cleavage arranged?
The animal pole blastomeres are rotated with respect to those of the vegetal pole so the axis of cleavage is curved.
How is a radial cleavage arranged?
The animal pole blastomeres are symmetrically oriented with those of the vegetal pole so the axis of cleavage is straight.
What are examples of simple body plans?
monoblastic or diploblastic
What is an example of a complex body plan?
triploblastic
What are the two evolutionary paths of the triploblastic body plan?
Deuterostomes and protostomes
What is the process of coelom formation called in protostomes?
Schizocoely
What is the process of coelom formation called in deuterostomes?
Enterocoely
How does schizocoely form the coelomic cavity?
By splitting the mesoderm to create the coelomic cavity.
How does enterocoely form the coelomic cavity?
By differentiation of the endodermal placodes to mesoderm. The mesoderm then forms pockets that bud off from the endoderm and extend to form the coelomic cavity.
What are the divisions of the human coelomic cavity?
The thoracic cavity and abdominopelvic cavity
What are the areas of the thoracic cavity?
- The pericardial cavity that surrounds the heart
- The pleural cavities that surround the lungs
- The mediastinum that contains the oesophagus, major vessels and certain nerves
What are the areas of the abdominopelvic cavity?
- The abdominal cavity that contains the abdominal viscera
- The pelvic cavity that contains the pelvic viscera
What is the function of the transverse fold (septum)?
It separates the pericardial and pleuroperitoneal cavities.
What is the pericardial cavity?
The mesoderm lined cavity around the heart.
What us the pleuroperitoneal cavity?
The mesoderm lined cavity around all visceral organs except the heart.
What separates the pleural and peritoneal cavity?
The diaphragm
What is the peritoneal cavity?
The mesoderm lined cavity of the abdominal/pelvic region.
