BISV - IB Biology - Topic 6 Human Physiology

Terms in this set (46)

◾ Protein digestion begins and bacteria are killed by HCl
◾The stomach contains gastric glands which secrete digestive juices for chemical digestion- pepsinogen is changed to pepsin (protease) by HCl and begins chemical digestion
◾Acids create a low pH environment (pH~1-2) that begins to denature proteins, while proteases like pepsin hydrolyse large proteins
◾The stomach also releases a hormone (gastrin) that regulates stomach secretions
◾The mechanical action of the stomach (churning) also promotes digestion by mixing the food
Small Intestine
◾The small intestine is where usuable food substances (e.g. nutrients) are absorbed into the bloodstream by diffusion, active transport and facilitated diffusion
◾The pancreas and gall bladder (via the bile duct) both secrete substances into the small intestine to aid in digestion
◾The small intestine is lined with smooth muscle to allow for the mixing and moving of digested food products (via segmentation and peristalsis) ◾It also contains small pits (crypts of lieberkuhn) that secrete intestinal juices
◾The small intestine contain infoldings called villi, to increase surface area and optimise the rate of absorption. Microvilli on villi to further increase SA:Vol.
Large Intestine
◾The large intestine absorbs water and dissolved minerals (also helps make Vitamin K) from the indigestible food residues, and by doing so converts what remains from a fluid state into a semi-solid faeces
◾The faeces is stored in the rectum and eliminated out the anus