Tissues, Organs and System Flashcards
define tissue
a collection of cells that are adapted to a specific function
define organ
two or more tissue combines to create a structural unit that has a particular function that is a sum of its parts.
List three tissues not in organ systems
the ovum, spermatozoa and corpuscles in the blood( red & white blood cells and platelets)
where are nerve cells derived from
ectoderm
where are epithelial cells derived from
all three layers of the germ layer. the endoderm, mesoderm, ectoderm.
where is mucosae derived from
endoderm
where are muscle and connective tissue derived from
mesoderm
describe how cells are held together at the molecular level
cell to cell adhesion molecules,
extrasolar matrix proteins(fibres)
internal-external scaffolding
close proximity ( pressure effects)
list the epithelial cell adherence systems in the lateral surface?
tight junctions, adherens junctions,
desmosomes( adhering spot), gap junctions , cell adhesion molecules
list the epithelial cell adherence systems in the basal surface
hemi- desmosome
focal adheasions
integrins
proteoglycans
cell adhesion molecules
what cells do not have gap junctions?
spermatozoa, red blood cells and other motile cells.
Difference between the major epithelial cell adherence systems in the basal surface,
hemi-desmosomes and focal adhesions attachment to basal lamina.
they both use integrins( that work as a alpha beta dimer)
however focal adhesion use intercellular actin filaments to attach to fibronectin through intern proteins. when attached there is conformational change that results in binding to collagen fibres
with hemi-desmosomes there is intracellular intermediate filaments of cytokeratin attached to laminin through integrins
how do epithelial cells adhere to other epithelial cells
through cell surface proteins
how do epithelial cells adhere to the basal lamina
through cellular adhesion molecules like the hemi desmosomes, focal adhesions, integrins protegylcans.
how do epithelial cells adhere to muscle cells
connective tissue fibres
what is the function of adherence proteins
to maintain the survival and structure of cells and therefore tissues.
to prevent pathogens from gaininng entry to the internal environment.
define the mucosal membrane and its functions
the mucosal membrane is the moist inner lining of some organs and body cavities.
it stops pathogens and dirt from entering the body, prevents bodily tissue from becoming dehydratin, lubricate the surface.
function of structure of the mucosa in the oesophagus
the oesophagus function is to provide passage from the oral cavity to the stomach.
its functional specialisations are
1- the epithelial cells are non keratinised stratified squamous cells.
2- scattered submucosal glands to provide lubrication
3- well developed muscularis external allows for organ return to original dimensions and peristaltic movement of food ( inner is circular, outer is longitudinal)
function of the mucosa and what layers do what
the mucosa has three main functions,
1- lubrication
2- preventing dehydration
3-preventing pathogen ingress
it is made of three layers
epithelial cells,
lamina propria - contains specialised cells ( macrophages, lymphocytes, plasma cells, mast cells). it provides nutrition to the epithelium and immune protection.
muscularis mucosa contains no specialised cells and it folds the mucosal to increase surface area.
what is the role of tight junctions
tight junctions prevent the movement of larger molecules through the outer layer/lumen into the deeper tissue layers of the organ.
located at the very top of the cell near the lumen/apical surface in the lateral border,
in the gut they can open to allow small molecules like sugar amino acids and water to cross to underlying tissues ( paracellular transport)
what are adhesion junctions
specific to epithelial and endothelial cells. 1/3 of the distance from the luminal surface they function as a tissue stabilising factor and additional transport barrier. they are attached to the actin filament network
what are the desmosome
the strongest of cell to cell adhesions, its tole is to provide mechanical strength and prevent tissue destruction. Intermediate filaments made of cyto-keratin fibres intracellularly and transmembrane inter cellularly.(between cells)
how to distinguish between the small intestine and large intestine.
In the large intestine there are more goblet cells and less villi
define epithelia
epithelia are sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line many internal surfaces.
function of the gastrointestinal mucosa and how the structure of the constituent tissue is related to this
the function of the gastorintestinal mucosa is to absorb nutrients, protect from pathogen ingress and move contents and expel waste. the microvilli on the epithelia allow effienient transport and absorption when a peristaltic movement is propagated form the muscularis external.
