Gastrointestinal Diseases

The small intestine is indeed the main site of digestion and the principal site for nutrient absorption in the human body. It plays a crucial role in breaking down food into smaller molecules and absorbing nutrients such as carbohydrates, proteins, and fats. The small intestine has specialized structures called villi and microvilli, which increase its surface area for efficient absorption. This is where most of the nutrients are absorbed into the bloodstream and transported to the cells for various metabolic processes. Therefore, the statement "The small intestine is the main site of digestion and the principal site for nutrient absorption" is true.

The enteric nervous system is a division of the autonomic nervous system that is responsible for regulating the gastrointestinal system. It consists of a complex network of neurons that can function independently of the central nervous system. Reflex arcs are neural pathways that allow for rapid, automatic responses to stimuli. Since the enteric nervous system is capable of processing and responding to sensory information within the gastrointestinal system without input from the central nervous system, complete reflex arcs can indeed exist within it. Therefore, the statement is true.

The sympathetic nervous system has an inhibitory effect on the secretory and motor function in the gut. This means that it reduces the activity of the gut, including the secretion of digestive enzymes and the movement of food through the digestive tract. This is because the sympathetic nervous system is responsible for the "fight or flight" response, which prioritizes blood flow to the muscles and brain and reduces non-essential functions such as digestion.

The pharynx is not considered part of the mouth according to the notes. The mouth includes the teeth, palate, tongue, and salivary glands, but the pharynx is a separate structure located behind the mouth. It serves as a passage for both air and food, connecting the mouth to the esophagus and the nasal cavity to the larynx.

The main classes of macromolecules are carbohydrates, proteins, and lipids. Plastic is not considered a main class of macromolecule as it is not naturally occurring and does not fit into the traditional categories of biological macromolecules.

Fever is not one of the four common classes of symptoms and signs of GI disorders. The four common classes include abdominal or chest pain, altered ingestion of food, altered bowel movements, and GI tract bleeding. Fever is typically associated with infections or inflammation in the body, but it is not a specific symptom of GI disorders.

The parasympathetic nervous system has an excitatory effect on the motor function and secretion of the gut. This means that it stimulates and enhances the activity and movement of the digestive system, as well as promotes the secretion of digestive enzymes and fluids.

The vagus nerve is the key parasympathetic nerve that innervates the gut. It is responsible for regulating various functions of the gastrointestinal system, including digestion, motility, and secretion. The vagus nerve originates in the brainstem and travels down the neck, chest, and abdomen, sending branches to innervate different organs in the gut. Its parasympathetic fibers stimulate the release of digestive enzymes, increase blood flow to the gut, and promote peristalsis, helping to facilitate the digestive process. Therefore, the vagus nerve is crucial for maintaining optimal gut function.

The correct answer is True. The sequential and ordered process of digestion involves several steps. First, the food is lubricated and homogenized with fluids. Then, enzymes are secreted to break down the food into smaller molecules through hydrolysis. Electrolytes, hydrogen ions, and bicarbonate are also secreted to help with digestion. Bile acids are secreted to aid in the digestion and absorption of fats. Finally, the digested molecules are transported into enterocytes (cells in the small intestine) and then into the bloodstream and lymphatic system for distribution to the rest of the body.

The correct answer is "Mouth, Pharynx, Esophagus, Stomach, SI, LI, Rectum, Anal Canal and Sphincter". This is the correct progression of food along the alimentary canal. The food enters the mouth where it is chewed and mixed with saliva. It then passes through the pharynx and into the esophagus, which carries it to the stomach. In the stomach, the food is further broken down by stomach acid and enzymes. From the stomach, it moves into the small intestine (SI) where nutrients are absorbed. The remaining undigested material then enters the large intestine (LI), where water is absorbed and waste is formed. Finally, the waste passes through the rectum, anal canal, and sphincter before being eliminated from the body.

Increased secretion and decreased absorption causes diarrhea, which can be fatal due to fluid and electrolyte loss.

Pit/surface/foveolar cell and mucous neck cell both secrete mucus.

- The pyloric mucosa also does this and uses the same cells to do so.

Contraction of GI muscle cells depends on the amount of calcium that enters the cell. Calcium plays a crucial role in muscle contraction by binding to proteins and triggering the sliding of muscle fibers, leading to muscle contraction. When calcium enters the cell, it binds to specific proteins, causing the muscle cells to contract. Therefore, the amount of calcium entering the cell directly affects the contraction of GI muscle cells.

The enteric nervous system is a complex network of neurons that controls the functioning of the gastrointestinal tract. It is composed of numerous small ganglia, and within these ganglia, there are approximately 1,000,000 neurons. These neurons are responsible for regulating various digestive processes such as peristalsis, secretion, and absorption.

Pit/surface/foveolar cell secretes mucus
Parietal cells secerete acid and intrinsic factor
Zymogenic (cheif) cells secrete pepsinogen

They INCREASE surface area which increases the absorptive capacity of enterocytes by 5-fold

It is also called the Auerbach's plexus, not Meissner's plexus

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Peyer's patches are aggregates of lymphoid cells in the small intestine that play a crucial role in the immunologic defense of the gastrointestinal (GI) tract. They are responsible for monitoring and responding to pathogens and foreign substances that enter the GI tract. Peyer's patches contain specialized immune cells, such as B cells and T cells, which help in the production of antibodies and the activation of immune responses. These patches are essential for maintaining the integrity of the GI tract and protecting it from infections and diseases.

Interstitial cells of Cajal are involved in the generation of electrical pacemaker activity for GI motility. These cells are located in the muscular layer of the gastrointestinal tract and are responsible for initiating and coordinating the rhythmic contractions of the smooth muscles in the GI tract. They generate electrical signals that regulate the motility of the digestive system, allowing for the movement of food and waste through the digestive tract.

All of these symptoms are related to GI tract disorders, but only the correct answer lists all five of the symptoms of altered ingestion of food, which is one of the four main clinical manifestations of GI diseases.

The autonomic parasympathetic division is responsible for rest and digest activities in the body. Neurons of this division project from the medulla oblongata and sacral region. These neurons innervate various organs and glands in the body, promoting activities such as digestion, slowing heart rate, and increasing glandular secretions. The hypothalamus plays a role in regulating the autonomic nervous system but does not directly project neurons for the parasympathetic division. The thoracic and lumbar regions are associated with the sympathetic division of the autonomic nervous system. The basal ganglia is involved in motor control and does not directly project neurons for the parasympathetic division.

Dopamine is not one of the main stimulants for acid secretion. While histamine, acetylcholine, and gastrin are known to stimulate acid secretion, dopamine does not have this effect. Dopamine is primarily involved in regulating movement, mood, and the reward system in the brain. It does not play a significant role in acid secretion in the stomach.

Cephalic: anticipation (sight/smell of food) stimulates vagus
- 4 effects vagal stimulation has on acid secretion during this phase: increased pepsinogen release from chief cells, hydrogen release from parietal cells, histamine release from EC cells, gastrin release from G cells

Gastric phase: (about 70% of the response) When food hits the stomach. Vagal motor nerves release acetylcholine in the stomach to promote acid secretion. (Gastric release from G cells in the pylorus --> gastrin stimulates acid secretion --> acidification of pylorus stimulates somatostatin release --> inhibits acid secretion through neg feedback

Intestinal phase: (slowing down of release) Many substances (most noteably fat and acid) stimulate secretion of hormones that inhibit gastric acid secretion (ex: secretin and cholecystokinin)

Tonic contractions: sphincters that act as one-way valves to prevent retrograde movement of material from distal to more proximal regions and thus facilitate flow in an aboral direction. The proximal parts of the stomach and gallbaldder also exhibit tonic contractions

Peristatlic contractions: moving waves of contraction that propel digesta along the GI tract. Involves neurally mediated contraction of smooth muscle on the oral side of a bolus of digesta and a neurally mediated relaxation of muscle on the anal side of digesta. Occurs in pharynx, esophagus, gastric antrum, SI and LI

Segmental Contractions: Produce narrow contracted segments between relaxed segments. Allows mixing of lumincal contects with GI tract secretions and increase exposure to mucoasl surfaces where absorption occurs. occurs in stomach and intestine.

Pheromones do not modify the amplitude and duration of slow waves in the GI muscle contraction cycle. Pheromones are chemical substances released by animals that elicit a specific response from other individuals of the same species. While neurotransmitters, hormones, and other paracrine signaling molecules can influence the amplitude and duration of slow waves in the GI muscle contraction cycle, pheromones do not have this effect.

Top : 9000 mL/d
Middle: 3000 mL/d
Bottom: 1000 mL/d
Rectum: 100 mL/d

The first third is striated and the lower third is purely smooth

NO and vasoactive intestinal peptide allow for it to be relaxed during swallows.

The correct answer is sucrose and lactose. Sucrose is a disaccharide commonly found in table sugar and is composed of glucose and fructose molecules. Lactose is a disaccharide found in milk and is composed of glucose and galactose molecules. Both sucrose and lactose are commonly consumed in the human diet and can provide a source of energy.

It regulates mucosal functions

This is dependent on an intact enteric nervous system and originates in the antrum and goes to the terminal ileum.

During Phase III - period of regular, intense and repetitive contracts which is key to move the contents along and to prevent bacterial overgrowth. **associated with an increase in motilin levels

Serotonin is released into the small intestine to control the activity of the vagus nerve. Serotonin acts as a neurotransmitter in the gastrointestinal tract and plays a crucial role in regulating various functions, including the contraction and relaxation of smooth muscles, secretion of fluids, and control of pain sensation. It is involved in the regulation of gastrointestinal motility and helps to coordinate the movement of food through the digestive system. By controlling the activity of the vagus nerve, serotonin helps to regulate the overall digestive process in the small intestine.

The initial digestion of polysaccharides involves amylase, which occurs free in the lumen, while the final processes involve alpha-glucosidases and isomaltase, which are attached to the mucosal membrane of the enterocyte.

TAGs are degraded to fatty acids, which act as surfactants

The absorption of water is driven by the movement of sodium ions, while the secretion of water is driven by the movement of chloride ions. Sodium ions play a crucial role in the absorption of water by creating an osmotic gradient that draws water into the cells. On the other hand, chloride ions are involved in the secretion of water by creating an osmotic gradient that causes water to move out of the cells. Therefore, the correct answer is Sodium, Chloride.

Slow waves are rhythmic contractions of the smooth muscles in the intestines that help move food along the digestive tract. These waves occur at a frequency of around 12 per minute in the intestines. Therefore, the correct answer is 12.

They are tetrapotential stem cells

Can become: Enterocytes (absorb), Goblet cells (secrete mucus), Enteroendocrine cells (secrete hormones) Paneth cells (secrete antimicrobial peptides and growth factor)

Neurons of the autonomic sympathetic division project to the gut from the thoracic and first lumbar segments of the spinal cord. This means that the sympathetic nerves that innervate the gut originate from these specific regions of the spinal cord.

Muscarinic and nicotinic acetylcholine receptors are the two types of receptors in the gut that are sensitive to acetylcholine. These receptors play a crucial role in mediating the effects of acetylcholine on various physiological processes in the gut, such as smooth muscle contraction, secretion, and motility. Muscarinic receptors are G-protein coupled receptors, while nicotinic receptors are ligand-gated ion channels. Activation of these receptors by acetylcholine leads to the initiation of intracellular signaling pathways that ultimately regulate gut function.

Acts on alpha and beta adrenergic receptors

The outer longitudinal layer of the muscularis externa is thickened in the gastric antrum and forms sphincters. This layer of muscle controls the motility in the gastrointestinal (GI) tract. It helps in the movement of food through the digestive system and also aids in the regulation of the opening and closing of sphincters to control the flow of food and prevent backflow.

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The superficial muscular plexus is not an additional plexus of the GI system. The GI system has three main plexuses: the myenteric plexus (also known as the deep muscular plexus), the submucosal plexus, and the Meissner's plexus. These plexuses are responsible for coordinating the movement and function of the gastrointestinal tract. The superficial muscular plexus is not mentioned as one of the main plexuses and therefore is not an additional plexus of the GI system.

amylases and lingual lipases are produced by the salivary glands in the mouth to start the digestion of cards and lipids. The catolysis of proteins starts in the stomach with the secretion of HCl and proteases

The correct answer is "Diffuse populations of mucosal immune cells." According to the given options, all of them are examples of non-immunologic defenses except for diffuse populations of mucosal immune cells. This is because immune cells are part of the immune system and are involved in immunologic defense mechanisms, not non-immunologic defenses.

Norepinephrine binds to adrenergic receptors (either alpha or beta), this is the final step in the diagram

The correct answer is Substance P and Neurokinin A. Substance P and Neurokinin A are both excitatory nonadrenergic/noncholinergic neurotransmitters. These neurotransmitters are involved in various physiological processes, including pain transmission, neurogenic inflammation, and regulation of smooth muscle contraction. They are released by sensory neurons and play a role in the transmission of pain signals in the peripheral and central nervous systems.

The 7 L of secretions is made up of:
- 1.5 L saliva
- 2.5 L gastric juice
- .5 L bile
- 1.5 L pancreatic juice
- 1 L intestinal secretions

Of this total 9 L, approximately 100 mL ends up in stool daily, the balance in recycled.