AP1 Module 3 Flashcards
Pepsinogen
stomach. roles throughout the gastrointestinal tract
Pepsinogen (a pro-enzyme) is secreted by the** chief cells** in the stomach. Hydrochloric acid converts the inactive pepsinogen (secreted by the chief cells) into the active enzyme pepsin, which begins the breakdown of proteins. Mucus protects the stomach lining from the hydrochloric acid and pepsinogens. The muscularis externa churns and mixes the food, breaking it into smaller pieces. The smaller pieces allow for more surface area of the food to be exposed to the enzymes in the stomach to form chyme.
ogen means that it is a pre-enzyme (not ready yet) can.t make any activi
Ingestion
digestive system
is when food enters the mouth.
Peptides
roles throughout the gastrointestinal tract
small intestine
which result from the first step in protein digestion, are digested by peptidases to amino acids
Pharynx
connects the mouth to the esophagus . made up of three parts: the nasopharynx , oropharynx, and laryngopharynx. The pharynx has two types of skeletal muscles: a circumferential outer layer and an inner longitudinal layer. These two layers of muscles contract alternatively causing peristalsis which squeezes food into the esophagus.
Cellular respiration
ATP reaction
Cellular respiration is an aerobic process (oxygen must be present) used by cells to produce energy. Respiration takes place inside and around the double membrane-enclosed organelle known as the mitochondria.
The stomach has two purposes
- it is a temporary storage area for food. Usually, the stomach stores up to two liters of partially digested food. The stomach wall contains rugae.
- mechanical food breakdown.
Esophageal Hiatus
The esophageal hiatus is the opening in the diaphragm through which the esophagus passes from the thoracic to the abdominal cavity. It is one of three apertures in the diaphragm and is located in the right crus.
ascending colon
large intestine parts
which runs along the right side of the abdomen superiorly. The right colic (hepatic) flexure connects the ascending colon to the transverse colon.
third
vitamins
Fat-soluble vitamins are stored in body fat. Ingestion of excessive amounts of fat-soluble vitamins can be problematic.
large intestine
Misc fun facts
The large intestine’s major function is to propel wastes from the body (see Figure 3.24). The large intestine also reabsorbs some water and electrolytes. About 1.5 liters of water enter the digestive tract daily because of eating and drinking, and an additional 8.5 liters enter the digestive tract each day carrying the various substances secreted by the digestive glands. About 95% of this water is absorbed by the small intestine, and much of the remaining portion is absorbed into cells in the wall of the colon. When materials pass through the colon too quickly, excess water is not reabsorbed, and diarrhea will result. Extreme or prolonged diarrhea can lead to serious dehydration and electrolyte loss. Vitamin K and certain B vitamins, all produced by intestinal bacteria, are also absorbed by the cells in the wall of the colon.
ingestion
roles throughout the gastrointestinal tract
starting with the mouth. occurs when food enters the mouth. The mouth is also where digestion begins, both mechanical and chemical. Chemically, saliva is released by the salivary glands (note the locations of the parotid, sublingual, and submandibular glands in Figure 3.27 below).
vitamins
Water-soluble vitamins are not able to be stored in the body and are excreted in urine.
digestive system
high level
The digestive system has four main roles that it performs: ingestion, digestion, absorption, and defecation.
Ascending, Transverse, Descending Colon
Digestion
digestive system
Digestion or food breakdown occurs when food is moved, mixed, and exposed to enzymes along the gastrointestinal tract. Digestion can be divided into two parts:
1. mechanical digestion
2. chemical digestion.
Hormones that cause satiety (decrease hunger)
Leptin, Serotonin, Cholecystokinin (CCK)
satiety
Basic physiological responses
satiety is the satisfied feeling of being full after eating
The GI tract itself contributes to the feeling of satiety.
Anus
Anus, terminal opening of the anal canal, the portion of the digestive tract through which fecal material is excreted.
chyme
stomach
The stomach contents are called chyme, which is a thick, soupy consistency.
Chyme stimulates the small intestine to secrete two hormones: cholecystokinin and secretin.
muscularis externa
esophagus
muscular tube, containing four layers of tissue of the same types found in the stomach, small intestine, and large intestine.
The third layer is the muscularis externa made of two layers of muscle: the outer longitudinal fibers and inner circumferential fibers.
ATP
In summary, cells require ATP to survive. Under aerobic conditions (in the presence of oxygen), the complete catabolism of glucose yields 2 ATP from glycolysis, 2 ATP from the TCA cycle and 34 ATP from the electron transport system, for a total of 38 ATP from a single glucose molecule. The summation of these metabolic processes is shown in Figure 3.32 below.
adenosine triphosphate or ATP
The most widely used form of energy in the cells is adenosine triphosphate or ATP
Mesentery
The mesentery is a fold of membrane that attaches the intestine to the wall around the stomach area and holds it in place
Ileum
section of the small intestine the ileum (see Figure 3.20) is the third section. The ileum is slightly longer than the jejunum. Goes to the ileocecal valve (controls the entrance to the large intestine).
lacteal
Each villus contains blood vessels and a lymphatic vessel
Sugars and amino acids enter villi cells, and then are absorbed through the capillary beds present inside the villi. ugars and amino acids enter villi cells, and then are absorbed through the capillary beds present inside the villi. The nutrients are carried into the hepatic portal circulation (of the liver) before entering general blood circulation. Molecules that are too large to enter blood capillaries, such as glycerol and fatty acids, are transported into lacteals. For example, fatty acids enter villi cells and are reassembled into fat molecules (triglycerides). The newly packaged fat molecule moves into the lacteals, eventually connecting to general blood circulation at the thoracic duct.
lacteal vessel. with vessels (atery in red, vein in blue) for nutrient a
Palate
Palate: The roof of the mouth. The front portion is bony (hard palate), and the back portion is muscular (soft palate).
tooth
crown
is the visible portion of the tooth and lies above the gum line.
body
stomach
which is the wider midportion located between the fundus and fourth part, which is the funnel-shaped pyloric region.
third part
stomach
roles throughout the gastrointestinal tract
Once in the stomach, mechanical and chemical breakdown of food continues with the secretion of digestive juices. Very little to no nutrient absorption occurs in the stomach. The stomach’s main function is for mechanical and chemical breakdown of food. The hormone gastrin stimulates the stomach to secrete gastric juices, which contains: pepsinogens, mucus, and hydrochloric acid.
tooth
neck
is located within the upper portion of the gums (gingiva)
Figure 3.28
parietal cells
stomach. roles throughout the gastrointestinal tract
The parietal cells (located in the wall of the stomach body) secrete hydrochloric acid, generating a pH of 1.3-3.5. This very acidic pH kills many of the bacteria ingested along with food. In addition, the low pH stops the activity of salivary amylase. The secretion of hydrochloric acid is essential in the activation of pepsin.
Anabolism
Anabolism is the set of reactions in which smaller molecules are combined to make larger, more complex molecules.
tongue
- is a muscle. it attaches to other structures so it can contract for movement. The tongue’s attachments are the hyoid bone, the mandible, and the lingual frenulum. grips the food and constantly repositions it between the teeth, forming it into a compact mass called a bolus.
- It contains papillae. three types of papillae that help to grip food on the tongue: circumvallate, fungiform, and filiform. Circumvallate and fungiform papillae both contain taste buds. Taste buds are chemical receptors that are stimulated by the chemical composition of food. They are found primarily on the tongue as well as on the surface of the mouth and the wall of the pharynx.
Lipid metabolism
**Lipid metabolism **occurs in the liver by a process known as beta-oxidation. Lipids are used by the body primarily during low energy activities. Lipid metabolism yields twice the amount of ATP than when a carbohydrate or protein is broken down. A fat molecule is broken down in the mitochondria to form acetic acid. Acetic acid is further catabolized by the TCA cycle to carbon dioxide forming some ATP molecules. The electron transport chain (as described above) then converts hydrogen atoms to water. This process releases energy, which is used to add phosphate to ADP to form ATP in the same way.
serosa
esophagus
muscular tube, containing four layers of tissue of the same types found in the stomach, small intestine, and large intestine.
Finally, the fourth and outermost layer is the serosa made up of cells that make serous fluid.
Electron transport system
ATP reaction
electron transport system also referred to as the electron transport chain, is a continuation of cellular respiration. In some organisms this process can proceed either aerobically (with oxygen) or anaerobically (without oxygen). In humans, this process is carried out under aerobic conditions. As electrons are transferred from NADH/FADH2 to terminal electron acceptors (O2; aerobic respiration), energy is released and captured by electron acceptor proteins located in the inner membrane of mitochondria. Electrons are then passed down a chain of electron acceptors (thus the name) causing protons (H+; positive charge) to be pumped out of the membrane. This causes a strong differential across the inner mitochondrial membrane, which forms the proton motive force. The proton motive force drives H+ back through the ATP synthase complex, also located in the membrane, resulting in the production of up to 34 molecules of ATP.
Peristalsis
stomach. roles throughout the gastrointestinal tract
Peristalsis moves the food toward the small intestine where the pyloric sphincter controls the slow release of chyme into the duodenum
Hormones
Hormones also influence our feelings of hunger or satiety. The human body produces a variety of hormones that work together to balance our hunger and satiety.
Hormones are compounds secreted into the bloodstream by one type of cell that acts to control the function of another type of cell. The list below outlines several types of hormones related to hunger and satiety.
stomach
is a backward C-shaped organ located along the left side of the abdomen below the diaphragm. Food enters the stomach from the esophagus via the cardiac sphincter, also known as the lower esophageal sphincter (LES) or the gastroesophageal sphincter. Food exits the stomach via the pyloric sphincter into the small intestine.
small intestine
Absorption continues along the small intestine until almost all products of digestion have been complete. The epithelial cells of the villi produce intestinal enzymes, which remain attached to the plasma membrane of microvilli. These enzymes complete the digestion of peptides and sugars.
When food reaches the end of the small intestine, digestion is complete
Bacteria, undigested food, and water remain by the time chyme reaches the end of the small intestine.
cecum
large intestine parts
is the entrance to the large intestine through the ileocecal valve.
first
liver
Accessory Organs
has numerous functions, including three that are important in digestion.
1. it produces bile. it is stored in the gallbladder
2. the liver stores glucose as glycogen
3. the liver produces** urea** from amino groups that are removed from excess amino acids.
Carbohydrates
Carbohydrates are classified as starches and sugars. Milk and fruits, such as apples or peaches, contain sugar. Grains such as wheat and vegetables such as potatoes contain starches.
major biochemical categories of food that the body needs in large amount
teeth
There are four different types
accommodate both a vegetable and meat diet. One-half of each jaw has two chisel-shaped incisors for biting; one pointed canine for tearing; two increasingly flat pre-molars for grinding; and three flat molars for crushing.
large intestine
As food continues to move along the gastrointestinal tract, it comes to the large intestine . This organ extends from the ileocecal valve to the anus. Muscular contractions move the food contents (chyme) through the large intestine (colon) to be excreted as feces. The large intestine has eight parts:
What remains of the food enters the large intestine by the ileocecal val
hypothalamus
The hypothalamus (see Figure 3.29) is a region of the brain that plays a role in hunger, satiety, and the feeling of “being full”.
The amount of nutrients in the blood begin to decline if a person has not eaten in a long period of time. This drop stimulates the feeding center in the hypothalamus and signals the body to feel “hungry” and desire to eat. When the nutrient level of the blood begins to rise, the satiety center is activated and the desire to continue to eat declines. The hypothalamus is constantly processing signals from a variety of nerves throughout the body that influence food intake. If a portion of the hypothalamus is damaged or destroyed, from certain chemicals, trauma, surgery, or cancers, the regulation of hunger and satiety can be lost. In such an instance, the body no longer receives signals to stop eating and weight gain is almost certain.
accessory digestive organs
teeth, tongue, gall bladder, salivary glands, liver, and pancreas
Fundus
The fundus is a dome-shaped part of the stomach that stores gas from digestion
The second part is the fundus, which is dome-shaped top of the stomach j
Absorption
digestive system
is the process of moving digested food into the bloodstream.
Dentin
tooth
Dentin or dentine is a layer of material that lies immediately underneath the enamel of the tooth. It is one of the four major components of the tooth which comprises: The outer hard enamel. The dentin underneath the enamel. The dental pulp that lies soft and encased within the dentin
Plicae Circulares
The small intestine is the site of terminal food digestion, nutrient absorption, and endocrine secretion. The lining of the small intestine consists of a series of permanent spiral or circular folds, termed the plicae circulares, which amplify the organ’s surface area, promoting efficient nutrient absorption.
amino acids
There are nine amino acids called **essential amino acids **required in an adult human diet (with ten required in an infant’s diet). They are called essential amino acids because the body is unable to make these amino acids. Complete proteins contain all nine essential amino acids but incomplete proteins do not.
mechanical digestion
Digestion - two parts
occurs when food is physically broken down into smaller pieces. This occurs when the teeth chew food, when the stomach churns and mixes food, and as food is moved and squeezed along the gastrointestinal tract
Epiglottis
a flap of elastic cartilage that covers the larynx when swallowing food or liquid
Esophagus
extends from the pharynx to the stomach, travelling through an opening in the diaphragm on its way to the stomach (see Figure 3.13). It is a muscular tube, containing four layers of tissue of the same types found in the stomach, small intestine, and large intestine.
chyme
enters the duodenum
proteins and carbohydrates are only partially digested, and fat digestion still needs to be carried out. Considerably more digestive activity is required before these nutrients can be absorbed through the intestinal wall.
Cardiac region/sphincter
The lower esophageal sphincter (LES), also known as the cardiac sphincter, is an involuntary sphincter located at the bottom of the esophagus, where it connects with the stomach.
mucus protects
stomach
As with the rest of the digestive tract, a thick layer of **mucus protects the wall of the stomach **and the first part of the duodenum. In a circumstance where gastric juice does penetrate the mucus, pepsin starts to digest the stomach or duodenal lining and an ulcer results
autonamic neurvos system
peristalsis. swallowing
controls contractions of alimentary canal that moves swallowed food down the esophogus, turns the stomach and move cyme down the small/large intestines
tongue
A freely movable muscular organ that lies partly in the floor of the mouth and partly in the pharynx. It is the organ of taste and contributes also to chewing, swallowing, and speech.
adenosine diphosphate or ADP
If a phosphate group is removed from ATP it becomes adenosine diphosphate or ADP. Thus, ATP has energy to donate, while ADP can accept energy (phosphate group) to become ATP.
amylase
an enzyme, or special protein, that helps you digest carbohydrates. Most of the amylase in your body is made by your pancreas and salivary glands.
which digest starch