Lecture 23 Flashcards
What is important to remember about the tissues used in different areas of the GI system?
Different locations within the GI system have different functions, this means different tissues are used, though all will have epithelium cells of some description due to their contact with the outside environment.
What are the four basic tissue types and how do they apply to the GI system?
The epithelial cells are cohesive sheets of cells which cover/protect body surfaces, lines cavities, lines systems open to air and is involved in absorption and secretion. They can be sqamous (flat, in the peritoneum) cuboidal (square shape, salivary glands) or columnar (smaller width than length, found in small intestine villi). These can also be stratified (consisting of more than one layer, found as lining of oesophagus) or simple (one layer) Underneath them are connective tissue (cells plus ECM to increase strength adhesion of epithelia (this is always fibrous connective tissue under epithelial cells). There is muscle used in movement of the gut (smooth muscle) or as sphincters for control of flow. Nervous tissue controls all the actions.
What are unicellular glands
Unicellular glands are a single secreting cell found within epithelium, they typically have mucous granules on the apical (external) surface, a nucleus on the basal side, columnar and with a goblet shape.
What are multicellular glands?
Multicellular glands are being early in embryonic development underneath the epithelial layer (always from epithelium) which will secrete, the duct is the upper part and cells here can change the product but not make it, below this is the secretory cells. These can be tubular (a single tube) or compound (many branches within the gland).
What are the layers of the gut tube and what is the visceral peritoneum?
The gut tube has four layers, the visceral peritoneum is the outerlayer, it is serous epithelium and is a covering (not part of the wall). The four main layers are (from the innermost to outermost) the: mucosa (consists of epithelium, lamina propria (FCT), muscularis mucosae (smooth muscle), can also contain lymph nodes, ducts, blood vessels lymph vessels and nerve fibres), submucosa (FCT, gland and duct of gland) muscularis (circular muscle and longitudinal muscle) and then adventitia (FCT).
What role does the mouth play and what do saliva glands do?
The mouth is where digestion begins, it begins by mastocating of the food (chew), either large enough to be swallowed or for saliva (which helps protect the mouth from damage and digests well chewed carbohydrates), the saliva is produced in compound multicellular glands, the parotid glands only secrete the enzymes (serous), submandibular is mixed and sublingual secretes mucous only. Mucous cells are pale while serous ones are more red, they are both arranged into clusters (acinus), the actual secretory area (duct) is arranged into rows and secretory granules travel via very small lumens which fuse with the duct (granules are prevented from leaving due to epithelial cells and their tight junctions).
What role does the esophagus play and what is it like?
The mouth is where digestion begins, it begins by mastocating of the food (chew), either large enough to be swallowed or for saliva (which helps protect the mouth from damage and digests well chewed carbohydrates), the saliva is produced in compound multicellular glands, the parotid glands only secrete the enzymes (serous), submandibular is mixed and sublingual secretes mucous only. Mucous cells are pale while serous ones are more red, they are oth arranged into groups, the actual secretory area (duct) is arranged essentially into rows.
