Lecture 12 Flashcards
What are prominent features found in the small intestine?
Place circulars (valves of kercking).
What do the plicae serve as?
Increasing SA of small intestine.
What is on top of the plica?
Villi - fingerlike projections.
What is the part that ingavinates the lumen of the plica?
Villus.
What is the depression of the plica?
Intestinal glands (crypts of lieberkuhn).
What is the functional purpose of the glands and villus?
Increase SA for digestion and absorption.
What is in the core of the villus?
Support structures -
i. blood vessels - carry O2 rich blood toward the SI for metabolism. As capillaries become venous all the absorbed nutrients are carried away in the venous system towards the liver for processing and redistribution.
What is the middle vessel?
Lacteal. This is a lymphatic vessel.
What extends from muscular mucosa?
Smooth muscle fibres, which are found in the core of the villus (spindle tapered cells).
What is the key function of the smooth muscle fibres?
Contraction produces rhythmic beating of the villi, which is enhanced during digestion. This makes the contents are mixed to maximise exposure to epithelial cells. Smooth muscles help to squeeze the lacteals (milk) and the contents along.
What happens in elderly people?
Blood supply/circulation functions decrease. There will be decreased absorption (taking blood away from the gut). Lead to malabsorption and malnutrition.
What are microvilli?
Projections of membranes, filled with plasma membrane, into the luminal surface.
What is the primary function of microvilli?
Increase SA for absorption.
What is in the core of microvilli? and describe the function.
Actin filaments. These filaments are connected to cytoskeletal network within the cell. When the smooth muscle cells contract and move basement membrane of the epithelial cells, moves the cells on top of the basement membrane, mechanical movement transferred to cytoskeleton and transferred to actin filaments. Lots of micro whisks producing localised mixing of contents.
What is embedded within the lipid bilayer?
Digestive enzymes e.g. glycosidase. Helps to digest carbohydrates.
What coats the microvilli?
Glycocalyx. It is a slippery film, made up of glycoproteins, and acidic much polysaccharides.
What does the glycocalyx do?
Becomes a selective gate keeper. The desirable molecules are attracted by the glycocalyx, and unwanted molecules the glycocalyx becomes a physical barrier.
What can cause enterocyte disfunction?
Tumors, infection, surgery and certain drugs can aggregate and inflame enterocytes. Outcome can be diarrhoea (inadequate absorption), fatty poo, abdominal pain discomfort and weight loss.
What do goblet cells do?
Secrete mucus. Apical surface do not have microvilli and mucus serves to help lubricate the process.
Where are enteroendocrine cells found?
Deeper in the crypts. But they are spread out.