Cells Into Tissues And Organs Flashcards
When do cells first coalesce?
What first cells form the baby and placenta?
During the Blastocyst stage of Embryogenesis.
The inner cell mass forms the baby
The trophoblast cels form the placenta
Where do all cells in the body come from?
All the bodies cells come from the epiblast stage
What is a hypoblast?
A yolk sac that feeds the epiblast
List the different ways cells are held together
Cell-cell adhesions
Extracellular Matrix Protiens (fibres)
Internal-External scaffolding
Close proximity (pressure effect, cells in middle pushed together)
Describe the structure of connective tissue.
Plentiful ECM (scaffold outside cell)
Sparse cell distribution
Matrix rich in fibrous polymers (collagen esp) and bears mechanical stres
Rare that cells directly attached to each other
Describe the structure of epithelial tissue layers.
Cells bound tightly together as sheets
ECM rare, mainly thin basal lamina (underlies epithelium)
Cell-cell adhesions bear the mechanical stress
Junctions tie adjacent cells to each other or basal lamina
Intracellular protein filaments cross cytoplasm of cell to join junction in plasma membrane
What are the 3 components of connective tissue layers?
Cells=mature fibroblasts, fixed adipocytes and reticular cells
Fibres=collagen, elastin and reticular fibres
Ground substance=glycosaminoglycans (attract H2O)
What is the function of connective tissue?
Bind + support Protect + insulate Reserve fuel + cells (marrow and fat) Transport Separate tissues
List the adherence systems in the lateral surface of epithelial cells
Tight junctions Adherens junctions Desmosomes Gap junctions Cell adhesion molecules
List the adherence systems of the basal surface of epithelial cells.
Hemi-demosomes Focal adhesions Integrins Proteoglycans Cell adhesion molecules
Describe key factors of tight junctions
Located at very top of cell, near lumen/apical surface in the lateral border
Long fusion length
Prevent movement of large molecules into copper tissues
Can open in the gut to allow small molecules in
Describe key functions in adhesion junctions
Location- 1/3 from luminal surface in the lateral surface
In pairs made from intracellular actin filaments
Linkkk to E-Catherine proteins across intercellular space
Belt of adhesion
Stabilise tissue and act as barrier to transport
Describe key functions in a gap junction
In base epithelial, cardiac and smooth muscle cells
Communicate changes in intracellular molecules
Allow free movement of small molecules
Not present in motile cells
Made from cylinders of Connexxion in hexagonal shapes (open+shut)
What is he basic function of a tight junction?
It seals neighbour cells in epithelial sheets to prevent molecule leakage
What is the basic function of an adherence junction?
To join actin bundles in neighbouring cells
What is the main function of a desomosme?
To join intermediate filaments in neighbour cells
What is the main function of a gap junction?
Allow the passage of water soluble molecules and ions between cells
What is the main function of a hemidesmosome?
To anchor intermediate filaments to the basal lamina
What is the main function of a focal adhesion?
To anchor actin to the basal lamina
What do all adhesion types require?
The presence of Ca2+ ions
Describe main structural characteristics of the mucosal membrane.
It lines all hollow moist internal organs
It’s continuous with the skin at body openings
What is the function of the mucosal membrane?
It secretes mucus and protective fluid to-
Stop pathogens and dirt
Maintain hydration
Lubricate surfaces
List the layers of the GI tract and briefly describe
Mucosa-lines lumen
Muscularis mucosa-thin discontinuous smooth muscle
Submucosa-connective tissue layer with aretery, veins and nerves
Muscularis externa-smooth muscle, inner is circular, outer is longitude
Serosa- connective tissue
What is the function of the mucosa in the GI tract? And where do these functions occur?
Absorption-in microvilli of mucosa
Pathogen protection-by lymphocytes of mucosa
Moving the contents- muscularis externa
Expelling waste- muscularis externa
