Term+3+Plant+Parts+and+Human+Digestive+System

= Human Digestive System = Check out this website for interesting info on the Digestive System: @http://www.neok12.com/Digestive-System.htm

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How our digestive system works(turn up volume) media type="youtube" key="Z7xKYNz9AS0" height="480" width="640" ellery

When food enters the mouth, its digestion starts by the action of mastication, a form of mechanical digestion, and the contact of saliva. Saliva, which is secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food. After undergoing mastication and starch digestion, the food will now be in the form of a small, round mass, called a bolus. It will then travel down the esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein digestion. Gastric juice mainly contains hydrochloric acid and pepsin. As these two chemicals may damage the stomach wall,mucus is secreted by the stomach, providing a slimy layer that acts as a shield against the damaging effects of the chemicals. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which are waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. After some time (typically an hour or two in humans, 4–6 hours in dogs, somewhat shorter duration in house cats), the resulting thick liquid is called chyme. When the pyloric sphincter valve opens, chyme enters the duodenum where it mixes with digestive enzymes from the pancreas, and then passes through the small intestine, in which digestion continues. When the chyme is fully digested, it is absorbed into the blood. 95% of absorption of nutrients occurs in the small intestine. Water and minerals are reabsorbed back into the blood in the colon (large intestine). Some vitamins, such as biotin and vitamin K (K2MK7) produced by bacteria in the colon are also absorbed into the blood in the colon. Waste material is eliminated during defecation. ~yoke ting~
 * Digestion** is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones.

Plant Parts
Xylem and Phloem

Xylem - The function of xylem vessels  is to transport water, minerals and inorganic ions in the plant, and to provide support for the plant. The xylem is adapted to this function by being hollow and elongated, so that they can carry as much water as possible. They are dead cells, so have no cell contents of their own, maximising space for water and dissolved substances to be transported. The xylem vessels are continuous and end-walls between cells break down, and this means that there is nothing to impede transport. The walls of the xylem vessels are lignified (coated with lignin) and lignin may be annular (ring form), spiral or reticulate. This strengthens the xylem and allows it to withstand the tension created by the transpiration pull. Pits are present in the cell walls to allow the lateral movement of water. Xylem vessels  also have narrow lumens, which allows water to be drawn to a greater height by cappilarity.

Phloem  - The function of phloem is to transport sucrose and other soluble assimilates and organic substances. Phloem is made up of sieve tube elements which are joined end-to-end to form long tubes. These are living, but have no mitochondria, nucleus or golgi apparatus and no ribosomes. This is an adaptation so that the lumen for transport of sucrose etc. is larger and there is less obstruction to the flow of liquid in the phloem. The end walls of the sieve tubes are perforated and these perforated end walls are called sieve plates. Pores in the sieve plats offer less resistance to flow of liquid. Sieve tubes are always associated with companion cells which are also living and have a dense cytoplasm with all the organelles and a thin cellulose cell wall, which means that materials made in the companion cell can easily pass out into the sieve tube. The sieve tube cannot survive without the companion cell. The companion cells have many mitochondria to make ATP for active transport - another adaptation. Cellulose in the cell walls provides strength to prevent the sieve tubes bursting when under pressure.