POST 1: Describe the composition and functions of saliva
Saliva accomplishes favorable tasks in a person’s good health but receives little if any credit. It is composed from a variety of fluids from various glands of the body. The chemical make-up includes substances like electrolytes, sodium, potassium, calcium, magnesium, bicarbonate, and phosphates (Humphrey & Williamson, 2001). Other compounds in saliva are immunoglobulins, proteins, enzymes, mucins, and nitrogenous products (Humphrey & Williamson, 2001).
Salivary function can be organized into 5 major categories that serve to maintain oral health and create an appropriate ecologic balance. These include (1) lubrication and protection, (2) buffering action and clearance, (3) maintenance of tooth integrity, (4) antibacterial activity, and (5) taste and digestion (Humphrey & Williamson, 2001). These functions are essential for good health.
The various substances that make up saliva preform different tasks. Salivary components work in concert in overlapping, multifunctioning roles, which can be simultaneously beneficial and detrimental (Humphrey & Williamson, 2001). Saliva contributes to the digestion of food and to the maintenance of oral hygiene. Without normal saliva function, a person is at risk for dental caries, gum disease, and gingivitis (Humphrey & Williamson, 2001). During digestion, saliva helps to moisten food and plays a role in taste (Humphrey & Williamson, 2001). Mucus binds and lubricates the food, while the salivary amylase, an enzyme, begins starch digestion in the mouth (Humphrey & Williamson, 2001). Lingual lipase, an enzyme, also begins fat digestion in the month (Humphrey & Williamson, 2001). Lysozyme, another enzyme, kills bacteria with the help of an antibacterial antibody called Immunoglobulin A (IgA) (Humphrey & Williamson, 2001).
Saliva also helps to lubricate and produce a coat of oral mucosa to protect the mouth from trauma during eating, swallowing, and speaking (Humphrey & Williamson, 2001). This protective role extends also to teeth. A tooth may lose enamel and calcium that is removed through the saliva, but the saliva also cuts down on the plaque that collects on the teeth. Plaque thickness and the amount of bacteria present control the efficiency of salivary buffers (Humphrey & Williamson, 2001).
In conclusion, saliva does not get the credit it deserves. It provides a variety of important functions that focus on digestion, protection, and bacteria control. It is an essential component to good oral health.
Post2: Factors that regulate hunger and satiety
With obesity being one of the biggest health problems we face today, a special interest has been taken in the study of appetite. When our body is fasting, it will use its own fat stores as a source of energy, however, in order to ensure survival our body will send signals to let us know that we must eat to avoid starvation. The ventromedial portion of the hypothalamus is the portion of the brain that regulates appetite and weight, whereas the lateral hypothalamus controls satiety (Ahima & Antwi, 2009). These two areas of the hypothalamus must send and receive signals from different parts of the body for us to know whether we are hungry or satisfied.
One such area of the body that secrete hormones which control hunger and satiety is our gastrointestinal tract. Ghrelin is produced and secreted by the stomach and will increase in times of fasting to produce the feeling of hunger. After ghrelin is secreted, it will cause the hypothalamus to produce growth hormone releasing hormone in order to prepare the body to receive the nutrients we are about to ingest (Saladin, 2018, p.992). The level of ghrelin will begin to diminish about an hour after eating.
While ghrelin stimulates hunger, there are a variety of hormones which will signal the end of a meal, “Cholecystokinin (CCK) is secreted by enteroendocrine cells in the duodenum and jejunum” (Saladin, 2018, p.993). This peptide was the first to be found to be a factor in suppressing the appetite and it is achieved by stimulating the vagal CCK1 receptors and the brain (Ahima & Antwi, 2009). CCK also helps bile and pancreatic enzyme secretion. Much like CCK, another hormone that signals satiety is Peptide YY (PYY). PYY is secreted by the enteroendocrine cells within the ilium and the colon. These cells can sense when food enters the stomach and will begin to secrete PYY before the food reaches the ileum and will be there long after a meal is completed (Saladin, 2018, p.992). In doing this, one feels full for a longer amount of time because it prevents the stomach from emptying out too fast (Saladin, 2018, p.992). Much like PYY and CCK, Amylin helps to produce the feeling of satiety, but it is produced in the beta cells of the pancreatic islets (Saladin, 2018, p.993).
While the aforementioned regulators are considered short termed because they work over a short period of time (within minutes to hours of food consumption), there are peptides within the body which will work over a period of weeks to years called long term appetite regulators (Saladin, 2018, p.993). These regulators are charged with controlling caloric intake and energy expenditure via “adiposity signals” (Saladin, 2018 p.993). Leptin is secreted by fat cells in the body tells our brain how much fat we have stored within our body. Insulin, which is secreted by pancreatic cells in response to a meal are produced to increase glycogen, fat and protein storage (Ahima & Antwi, 2009). Much like leptin, insulin will also alert the brain to the available fat stores within the body. In allowing the brain to know how much fat the body has available for energy and hormone production, the brain can send the appropriate signals to “activate the mechanisms for adding and reducing fat (Saladin, 2018, p.993).