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Biology IB HL - D2 Digestion Part 3
This deck covers the structural features and roles of the villi in the digestive system, including the functions of microvilli, blood supply, epithelium, lacteals, and more.
What are 6 structural features of the villi?
Microvilli; Rich blood supply; Single layer epithelium; Lacteals; Intestinal glands; Membrane proteins; MR SLIM
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Key Terms
Term
Definition
What are 6 structural features of the villi?
Microvilli; Rich blood supply; Single layer epithelium; Lacteals; Intestinal glands; Membrane proteins; MR SLIM
What is the role of microvilli?
Ruffling of epithelial membrane further increases surface area
What is the role of rich blood supply?
Dense capillary network rapidly transports absorbed products
What is the role of single layer epithelium?
Minimises diffusion distance between lumen and blood
What is the role of lacteals?
Absorbs lipids from the intestine into the lymphatic system
What is the role of intestinal glands?
Exocrine pits (crypts of Lieberkuhn) release digestive juices
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| Term | Definition |
|---|---|
What are 6 structural features of the villi? | Microvilli; Rich blood supply; Single layer epithelium; Lacteals; Intestinal glands; Membrane proteins; MR SLIM |
What is the role of microvilli? | Ruffling of epithelial membrane further increases surface area |
What is the role of rich blood supply? | Dense capillary network rapidly transports absorbed products |
What is the role of single layer epithelium? | Minimises diffusion distance between lumen and blood |
What is the role of lacteals? | Absorbs lipids from the intestine into the lymphatic system |
What is the role of intestinal glands? | Exocrine pits (crypts of Lieberkuhn) release digestive juices |
What is the role of membrane proteins? | Facilitates transport of digested materials into epithelial cells |
What 4 features does the epithelial lining of villi contain ? | The epithelial lining of villi contains several structural features which optimise its capacity to absorb digested materials: tight junctions; microvilli; mitochondria; pinocytotic vesicles |
What are tight junctions? | Occluding associations between the plasma membrane of two adjacent cells, creating an impermeable barrier |
What is the role of tight junctions? | They keep digestive fluids separated from tissues and maintain a concentration gradient by ensuring one-way movement |
What is the role of microvilli? | Microvilli borders significantly increase surface area of the plasma membrane (>100×), allowing for more absorption to occur |
What is the membrane of microvilli embedded with? | The membrane will be embedded with immobilised digestive enzymes and channel proteins to assist in material uptake |
Why do epithelial cells have large volumes of mitochondria? | Epithelial cells of intestinal villi will possess large numbers of mitochondria to provide ATP for active transport mechanisms |
What may ATP be used for in villi? | ATP may be required for primary active transport (against gradient), secondary active transport (co-transport) or pinocytosis |
What is pinocytosis? | Pinocytosis (‘cell-drinking’) is the non-specific uptake of fluids and dissolved solutes (a quick way to translocate in bulk) |
How are materials ingested via pinocytosis? | These materials will be ingested via the breaking and reforming of the membrane and hence contained within a vesicle |
What is the role of human intestines? | The human intestines function to complete the process of digestion and absorb digested products into the bloodstream |
What is the role of the small intestine? | The small intestine absorbs usable food substances (i.e. nutrients – monosaccharides, amino acids, fatty acids, vitamins, etc.) |
What is the role of the large intestine? | The large intestine absorbs water and dissolved minerals (i.e. ions) from the indigestible food residues |
What is dietary fibre? | Dietary fibre, or roughage, is the indigestible portion of food derived principally from plants and fungi (cellulose, chitin, etc.) |