Essay about human biology notes

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Organs are divided into alimentary canal and accessory digestive organs, which are connected to each other by ducts. Secretions help break down food. We have cephalic stimulation, which means that when we see a sign of in and out, we automatically associate it to a burger and due to classical conditioning, we have a conditioned reflex to ‘drool.’ It does not require any actual sight, smell or sense of the food. So from our cerebral cortex a message is sent to the salivary center in the medulla that causes us to drool. Salivary glands produce saliva. There are parotid glands, submandibular glands and sublingual glands. Saliva is 99.5% water, the remaining 0.5% are proteins. These proteins are enzymes. The pH of these are neutral (7). There are also mucus and lysozymes. Lysozymes break down bacteria in food. Chewing is both voluntary and involuntary. Incisors are for clipping.
Canines are for shearing. Shearing is for meat. Molars are for grinding. After your chew your food you have a bolus. Swallowing is both voluntary and involuntary, voluntary until it hits the pressure receptors in the pharynx. The inside of the alimentary canal is the lumen. Moving away from the lumen is lamina propria (connective tissue), then muscularis externa (mixing and propulsion).
Peristalsis is a sequential contraction of the circular muscles. One purpose of the stomach is storage, and a little bit of digestion. It adds hydrochloric acid from the fundus and turn the bolus into a liquid called chyme. It helps the mixing. The antrum has lots of mucus that lowers the pH to 2. The mucus gives protection from the hydrochloric acid that would otherwise cause an ulcer and neutralizes the pH. The hydrochloric acid breaks down the pepsinogen and the pepsin attacks the proteins in your stomach. The first part of the small intestine is the duodenum. There is a feedback loop between the stomach and duodenum. If there is liquid in the duodenum, it tells the stomach to slow down and not take in more food as it usually would. If not then the duodenum allows the stomach to accept more. The pancreas adds alkaline fluid, the pancreatic amylase, to neutralize the chyme that currently has the pH of 2 in order to allow the small intestine to function at the pH of 7. The pancreatic amylase breaks down carbohydrates. The pancreas also gives pancreatic lipase which breaks down fats, and proteolytic enzymes that break down proteins. Cystic fibrosis is a condition when the duct is blocked from the pancreas, you take the proteins. The secretion of the enzymes and fluids are called the exocrine function. The endocrine function is the regulation. It produces insulin and glycogen. It controls your sugar level. Diabetes is an endocrine malfunction. The gall bladder is a storage area
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