AnP Digestive System

Triglycerides

Circulate in the blood and are made up of three fatty acids attached to a glycerol.

The brush borders of intestinal absorptive cells contain numerous goblet cells (True/False)

False

Pancreas

The exocrine tissues secrete a clear, watery, alkaline juice into the small intestine that contains several enzymes that break down food into small molecules that can be absorbed by the intestines. Trypsin digests proteins, amylase breaks down carbohydrates, and lipase breaks down fats into fatty acids and cholesterol

Gallbladder

accessory organ that stores and concentrates bile by absorbing its water and ions.

Bile

alkaline solution that neutralizes the acidic chyme in the duodenum; works as the "soap" to coat the droplets of chyme so that the fats will be able to be broken down and accessible to the enzymes.

Glucose

converted from fructose and galatose by the liver to be used as an energy resource

______________ is a hormone, whereas ________________ is an enzyme. a. Intrinsic factor; pepsin b. Gastrin; secretin c. Gastrin; cholecystokinin (CCK) d. Gastric lipase; gastrin e. Secretin; pepsin

e. Secretin; pepsin

What are the components of gastric juice and which cells secrete those components?

gastric juice is made up of mucus, hydrochloric acid, and pepsinogen

What is the role of the intrinsic factor?

intrinsic factor acts as a mediator that allows vitamin B12 to be absorbed since it doesn't have a receptor

Gastric juice

made up of mucus, hydrochloric acid, and pepsinogen (which becomes pepsin), this is the substance that does the chemical breakdown of food (mostly proteins) in the stomach

Ingestion

taking food into the GI tract (eating and drinking)

What is the role of the Na/K pump during nutrients absorption?

to produce energy that creates a gradient for amino acids and monosaccharides to enter the intestinal lumen

In what way does regulation of gastric emptying similar to gastric secretion? What is the major effector (target cell) that is regulated during gastric emptying?

- We are going to tell the stomach to slow down (such as in the case of high acidity in the stomach), and release the amount of chyme going into the duodenum. -The main effector is the pyloric sphincter because it is a smooth muscle that once contracted, nothing will go out. Sent signal to slow down through CCK and secretin.

How does our body defend itself against microorganisms that come with the food? Think about at least 3 lines of defense we discussed in class.

- enzymes in saliva and bile help detoxify antigens and xenobiotics - the low pH of the stomach is fatal for many microorganisms that enter it - immunoglobulin A prevents attachment of microbes so they cannot penetrate the epithelium, and lysozyme kills bacteria

Understand in detail how and where digestion and absorption take place visa proteins, carbohydrates, and lipids.

Carbs- glucose and galactose are absorbed via cotransport with sodium ions; fructose passes via facilitated diffusion Proteins- Lipids- enter intestinal cells via diffusion, then packed into chylomicrons to enter lacteals of the villi and are transported to systemic circulation via the lymph in the thoracic duct

The enteric nervous system regulates much of the digestive activity but its action depends on the central nervous system (True/False)

False

Surface epithelial cells

Lining the walls of the stomach; Made up of the mucosa, submucosa, muscularis externa, and the serosa. These cells lining the stomach secrete mucin, which physically and chemically protects the cells of the stomach from the acidic environment. These cells also have gastric pits leading to gastric glands that contain secreting cells important for digestion in the stomach.

Digestion

Mechanical and chemical breakdown of the food

Propulsion

Moving through the GI tract (esophagus- peristalsis)

What are the major exocrine products of the pancreas?

Pancreatic juice: Proteolytic enzymes that break down proteins are released in an inactive form and activated in the duodenum, other enzymes (lipases, nucleases, amylases) that require bile to be present in the intestinal lumen.

How is secretion of bile salts regulated?

Release of secretin (stimulated by acidic chyme and increases output of bicarbonate ions in the pancreas) and CCK (stimulated by fatty chyme and increases the output of pancreatic juice and the release of bile) from the pancreas

Intestinal phase

The stomach chemical secretion ceases once this phase of digestion begins. This action is initiated by the stretching of the duodenum and the secretion of the hormone enterogastrone. Enterogastrone controls stomach acid secretion primarily when fat reaches the duodenum. When this process occurs, appetite decreases in order to stop food consumption.

RCT

These are studies designed that randomly assigns participants into experimental or control groups and conducted in a way that the only difference between these two groups is the ending variable studied, for example weight loss. They are beneficial because they are effective in eliminating population bias, masking observational studies, and analysis with well-known statistical tools. However, these types of studies can be pricey in both time and money, can develop a volunteer bias, and may only provide correlational results, not the desired causation.

What are the major functions of the liver?

This is the detoxifying facility that converts nutrients into usable resources fro the body through metabolism. Useful for bile production, storage (glycogen, vitamins, fats, iron, etc. for whole body), and conversion of nutrients into useful products (amino acids into ATP, lipids, and glucose), synthesis for plasma proteins (delivering steroids and creating osmotic pressure), and includes defense and detoxifying mechanisms (modifies toxic substances and holds phagocytes)

Lacteal

a lymph tubule located in the villus that absorbs fatty acids for transport into the veins to join circulation and recovers lost fluids from the leaky capillaries

Cells in the stomach wall are protected from proteolytic activity, as a. the proteolytic pepsin enzyme is active only after being secreted to the lumen b. the proteolytic trypsin enzyme is active only after being secreted to the lumen c. proteolytic enzymes require bile for their activity d. stem cells will give rise to other cells that will replace the cells that died as a result of proteolytic activity

a. the proteolytic pepsin enzyme is active only after being secreted to the lumen

Pancreatic juice

an aqueous component, primarily made of bicarbonate, that neutralizes acid chyme in the duodenum and provides optimal environment for pancreatic enzymes.

Assuming you are on a fat-free diet, is there a role for the liver in digestion? a. No role, as the bile secreted from the liver is needed only for fat digestion b. The liver will convert amino acids into glucose and fat c. The bile contains enzymes that process some charbohydrates d. None of the above

b. The liver will convert amino acids into glucose and fat - Explanation: This is the liver's mechanism to convert any materials into useful resources for energy or storage

19. Which of the following enzymes functions at the lowest pH? a. salivary amylase b. pancreatic amylase c. pepsin d. trypsin e. dipeptidase

c. pepsin

Bile salts

cholesterol derivatives that assist in emulsifying fats in the duodenum and in digestion and absorption of fat and cholesterol; if there aren't enough in the system, then cholesterol crystalizes forming gallstones

Hydrochloric acid

component of gastric juice that assists in pepsin synthesis and activity, breaking down cell walls of plant foods, and defense against pathogens getting into the stomach. Secreted from parietal cells

Fructose

converted into glucose by the liver to be used as energy resource

HbA1c

develops when the oxygenated red blood cell protein, hemoglobin, binds with glucose in the circulation. When measuring it, doctors can discover our average blood sugar levels during a period of weeks or months. As the average blood sugar levels increase or decrease, it is in direct relation to the risk factor of developing diabetes complications within the body. As blood glucose levels become regulated at a healthy level, the levels also decline in direct proportion, indicating a decreased risk.

Pancreatic amylase

enzyme released from the pancreas to the small intestine that is essential for the breakdown of carbohydrates from starches to oligosaccharides

Salivary amylase

enzyme released in the mouth that easily breaks down starch and disaccharides into oligosaccharides, but are not essential to the digestion

Brush border enzymes

enzymes that assist in digestion of carbohydrates and proteins in the small intestine; some just sit on walls of microvilli but most are secreted

Bicarbonate ions

important factors for neutralizing the acidic chyme.

Peristalsis

in the digestive system controlled by the longitudinal and circular muscles, it is the contraction of these muscles that move food and digested products down the line; in the stomach, waves move toward the pylorus region of the stomach at the rate of 3 times per minute. This process is controlled by basic electrical rhythm initiated by pacemaker cells through the enteric nervous system

Summarize all the mechanisms that are used to neutralize the acidic chyme entering the small intestine. Why is it important to neutralize this chyme?

pancreatic juice neutralizes chyme due to its aqueous component, which is largely bicarbonate. the sodium bicarbonate in the juice gives it a slightly alkaline (basic) pH that buffers acidic juice in chyme, stops the action of pepsin from the stomach, and creates the proper pH for the action of digestive enzymes in the small intestine

Absorption

passing the end products through the lumen and into the blood and lymph (lacteal)

Secretin

release of this hormone is stimulated by acidic chyme and increases output of bicarbonate ions in the pancreas to neutralize the acid (alkaline solution)

CCK

release of this hormone is stimulated by fatty chyme and increases both the output of pancreatic juice (ligase) and the release of bile (by controlling the sphincter and gallbladder)

Lipase

released from the pancreas into the small intestine for the digestion of lipids from unremulsified fats into glycerol, monoglycerides, and fatty acids. Breakdown of lipids allows them to passively diffuse through the enterocytes/intestinal cells for absorption, but when reaching the blood they are transported as lipoproteins

Villi

second order of folding in the walls of the small intestine; finger like extensions of the mucosa that hold enterocytes for absorption

Mucin

secreted from the goblet cells lining the stomach and is important for creating a physical and chemical barrier to the cells of the stomach walls to protect it from the acidic gastric juice and, later, chyme.

Intrinsic factor

secreted in the stomach during digestion, it's a protein that continues from the stomach to the small intestine, and then enables the body to absorb vitamin B-12.

Pyloric sphincter

separates the stomach from the duodenum. This valve keeps food and gastric juices in the stomach until liquefied enough to proceed into the duodenum. Peristaltic waves push the chyme (i.e., foodstuff) through it, a small spurt at a time.

Meta-analysis/es

subsets of systematic reviews that, when performed, create statistical significance with studies that have conflicting results, therefore if there are any issues with imbalances from a cohort study or bias in an RCT, meta analyses can be performed to develop a more correct estimate of effect of the factors studied in regards to its relation to diabetes.

Pepsin

the enzyme synthesized in the gastric juice in the stomach that works on breaking down proteins into smaller and smaller peptides

Gastrin

the hormone that stimulates mainly the parietal cells, but also chief cells, therefore stimulating the secretion of the gastric juice components

Liver

the largest internal organ that is composed of hepatocytes, arranged in plates radiating outward from a central vein, that produce and secrete bile that flows between the cells toward the bile ducts that sit at the periphery of the organ. This is the detoxifying facility that converts nutrients into usable resources fro the body through metabolism. Useful for bile production, storage (glycogen, vitamins, fats, iron, etc. for whole body), and conversion of nutrients into useful products (amino acids into ATP, lipids, and glucose), synthesis for plasma proteins (delivering steroids and creating osmotic pressure), and includes defense and detoxifying mechanisms (modifies toxic substances and holds phagocytes)

Cephalic phase

the phase of digestive regulation that occurs in the brain; the anticipation of food prepares the body for the digestion, absorption and use of nutrients in food. The sensory aspect of food, such as the sight and smell, influences eating behaviors. (For example, the smell of a favorite dish can set the stage for hunger). This occurs as a result of the activation of the medulla oblongata by food-related sensory input. The medulla oblongata controls autonomic functions like heartbeat and respiration. The feel of food in the mouth or thoughts related to food send signals to the medulla oblongata via the vagus nerve to stimulate the release of stomach chemicals, pepsin and hydrochloric acid, which play a role in the breakdown of food.

Pepsinogen

the precursor enzyme secreted from chief cells that does not function until HCl is added

Duodenum

the shortest part of the small intestine, only 10 to 12 inches (25 to 30 cm) long. It receives food from the stomach, and passes food on to the jejunum; The partially digested food arriving from the stomach stimulates this area to produce hormones. These hormones tell the pancreas to release digestive enzymes, and the gallbladder to release bile. Much of the food digestion takes place in the duodenum. Digestive enzymes from the pancreas break down fats, proteins, and carbohydrates. The bile helps in the digestion and absorption of fats.

What structural modification underlies the stomach's ability to mechanically digest food?

the stomach has an extra group of muscles called the oblique muscles that are responsible for the churning and mechanical digestion of food

Enteric nervous system

the system that controls the stimulation of actions in the digestive system based on excitatory and inhibitory signals from the parasympathetic and sympathetic systems (respectively); includes local reflexes and long reflexes (interacts with the brain)

Parietal cell

these cells of the gastric glands secrete intrinsic factor and hydrochloric acid

Chief cells

these cells of the gastric glands secrete pepsinogen

G cells

these cells of the gastric glands, also called enteroendocrine cells, secrete gastrin into the lumen

Microvilli

third order of folding in the walls of the small intestine; tiny projections of membranes of the absorptive mucosal cells that form brush border containing enzymes

Gastric phase

this phase of digestion begins when food enters the stomach, causing the stomach to extend. The stomach then continues to release the digestive chemicals hydrochloric acid and pepsin, first stimulated in the cephalic phase. This process helps to improve food intake and digestion

What happens eventually to the bile salts after they assist in digestion and absorption?

transporters in the ileum bring them from lumen of digestive tract to intestinal capillaries, where they are transported to the liver via hepatic portal duct to be secreted again. ~ 5% lost in the feces

Symport/Cotransport

type of active transport when molecules that need energy for transport but "take a ride" with sodium that had been pumped out by the sodium pump

Lipoproteins

vehicle for the lipid to travel to the lacteal and the into the circulation; often too large to fit directly into the capillaries

Facilitated diffusion

when molecules travel through proteins in the membranes in the lumen and intestinal cells; monosaccharides use this method for absorption into the absorptive cells