BISC 3221 Chapter Notes - Chapter 25: Sternocleidomastoid Muscle, Chyme, Vagus Nerve

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Chapter 25: The Digestive System

• Digestive system = digestive tract + accessory organs

o Tract: oral cavity + esophagus + stomach + small intestine + large intestine

o Accessory: teeth + tongue + salivary glands + liver + pancreas

• Functions

o Ingestion: food and liquids enter digestive tract at mouth

o Mechanical processing: squashing with tongue, crushing with teeth, movement in

stomach

o Digestion: chemical and enzymatic breakdown of sugars/lipids/proteins into smaller

molecules

o Secretion: secrete acids, enzymes, buffers by tract or accessory organs

o Absorption: movement of organic molecules, electrolytes, vitamins, water across

digestive epithelium and into interstitial fluid

o Excretion: waste products secreted into digestive tracts

o Compaction: dehydration of indigestible materials/wastes before defecation of feces

• Lining of tract protects against corrosive effects of acids/enzymes, mechanical stresses, pathogens

swallowed/living in digestive tract

25.1 An Overview of the Digestive System

Histological Organization of the Digestive Tract

• Major layers: mucosa, submucosa, muscularis externa, serosa

• Variations are related to specific organ/region

• The Mucosa

o Inner lining, example of mucous membrane; loose connective tissue covered by

epithelium moistened by secretions

o Mucosal epithelium can be stratified (mouth) or simple (small intestine) (depends on

location)

o Mucosa of tract is organized in folds (plicae) that increase surface area for absorption; in

some areas they are permanent, in others they disappear as lumen fills

o Lamina propria: areolar tissue under epithelium; contains blood vessels, sensory nerve

endings, lymphatic vessels, smooth muscle fibers, areas of lymphatic tissue (part of

MALT)

o Muscularis Mucosae

▪ Band of smooth muscle and elastic fibers external to lamina propria

▪ Inner circular layer, outer longitudinal layer

• The Submucosa

o Dense, irregular CT outside muscularis mucosae

o Contains large blood vessels and lymphatics, exocrine glands that secrete

enzymes/buffers

o Submucosal plexus: network of nerve fibers/neuron bodies along outer margin;

innervates mucosa; contains sensory neurons, parasymp. ganglia, symp. ganglia

• The Muscularis Externa

o Surround submucosa, dominated by smooth muscle; inner circular, outer longitudinal

o Plays important role in mechanical processing, moving material through tract

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o Myenteric plexus: network of parasymp. ganglia and symp. postganglionic fibers

between 2 muscle layers; coordinate movements of 2 layers

o Forms sphincters at certain points along tracts; thickened areas of circular smooth muscle

• The Serosa

o Outer serous membrane

o NONE at pharynx, esophagus, rectum; instead adventitia (thick, fibrous sheet)

Muscularis Layers and the Movement of Digestive Materials

• Smooth muscle, nonstriated, involuntary, surrounded by CT, most have no motor innervation,

arranged in sheets, gap junctions electrically connect adjacent cells; when on contracts, the

contraction spreads like a wave throughout tissue

• Can contract in response to neurons, chemicals, hormones, concentrations of O2 or CO2, physical

factors (stretching/irritation)

• Plasticity: ability for muscle cell to adapt to stretched length and retain ability to contract on

demand

• Pacemaker cells: undergo spontaneous depolarization, causing contractions that lead to peristalsis

and segmentation; maintains rhythmic cycles in smooth muscle

• Peristalsis

o Waves of muscular contractions that move a bolus along length of tract

o Peristaltic wave: circular muscles contract behind digestive contents, then longitudinal

muscles contract, shortening adjacent segments, then circular contraction pushes bolus

• Segmentation

o Occurs in small intestine and large intestine

o Movements churn and fragment digestive materials, don’t produce net movement in a

direction

• Segmentation and peristalsis can be triggered by pacemaker cells, hormones, chemicals, physical

stimulation

• Peristalsis can be triggered by afferent and efferent fibers in glossopharyngeal, vagus, pelvic

nerves

• Myenteric reflexes: short reflexes that don’t involve CNS; can control local contractions

• Long reflexes: involve CNS interneurons and motor neurons; control large scale peristaltic waves

that move stuff from one region of tract to another

The Peritoneum

• Visceral peritoneum (serosa) is continuous with parietal peritoneum (lines inner body wall)

• Intraperitoneal organs: in peritoneal cavity, covered on all sides by visceral peritoneum (stomach,

liver, ileum)

• Retroperitoneal organs: covered by visceral peritoneum on anterior surface, organ lies outside

peritoneal cavity (kidneys, ureters, abdominal aorta)

• Secondary retroperitoneal organs: form as intraperitoneal but become retroperitoneal (pancreas,

duodenum)

• Peritoneum produces peritoneal fluid that lubricate surfaces

• Mesenteries

o Fused double sheets of peritoneal membrane

o Stabilize relative positions of organs, prevent entanglement of intestines

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Document Summary

Chapter 25: the digestive system: digestive system = digestive tract + accessory organs, tract: oral cavity + esophagus + stomach + small intestine + large intestine, accessory: teeth + tongue + salivary glands + liver + pancreas, functions. Histological organization of the digestive tract: major layers: mucosa, submucosa, muscularis externa, serosa, variations are related to specific organ/region, the mucosa. Malt: muscularis mucosae, band of smooth muscle and elastic fibers external to lamina propria. The peritoneum: visceral peritoneum (serosa) is continuous with parietal peritoneum (lines inner body wall) Intrinsic tongue muscles + extrinsic tongue muscles are under control of hypoglossal nerve (xii: extrinsic = hyoglossus, styloglossus, genioglossus, palatoglossus; perform gross movements of tonue. Intrinsic muscles alter shape of tongue, help in precise movements. Regulation of the salivary glands: controlled by autonomic nervous system, salivary glands all have symp and parasymp innervation, para stimulation accelerations rate of secretion, symp results in less secretion.

Related Questions

The digestion process begins at the mouth. Food enters and then accessory digestive organs like the tongue, teeth, and salivary glands break down the substance. It then travels through the pharynx and esophagus into the stomach, where the stomach acid further breaks down the food (UXL Complete Health Resource). After that, the food travels through the small and large intestines where a majority of its nutrients are absorbed. The waste then exits through the end of the large intestine which is made up of the rectum and anus. After the teeth assist in chewing, food rolls over the tongue and reaches stomach through the esophagus within 8 seconds. General Tsoâs Chicken and Rice consist of carbohydrates, fats and proteins. However, carbohydrates are digested easily than the fats and proteins. After broken down in the stomach, most of the nutrients are absorbed from the small intestine, and it takes 6 to 8 hours to pass through small intestine. The remaining unabsorbed material, âmoves very slowly through the large intestine where the final absorption of water and other nutrients take placeâ (UXL Complete Health Resource). The parasympathetic nervous system encourages the food to move through the digestive tract and motivates digestion process. The sympathetic nervous system works against the parasympathetic nervous system by decreasing the contraction and relaxation of the digestive tract (Taylor). Mouth produces saliva, which contains amylase. Amylase is key in digesting carbohydrates. The stomach produces hydrochloric acid, pepsinogen, intrinsic factor, and mucus (Taylor). Hydrochloric acid kills the bacteria and other organisms that enter the stomach, and then continues to activate pepsinogen. Pepsinogen then changes into pepsin, which digests protein peptides. The pancreas produces trypsin, chymotrypsin, carboxypeptidases, lipases, and phospholipases. Trypsin, chymotrypsin, and carboxypeptidases digest proteins, whereas lipases, phospholipases digest lipid molecules. Small intestine produces lactase, sucrase, maltase, lipases, and peptidases. Lactase, sucrase, and maltase digest carbohydrates (UXL Complete Health Resource). Saliva glands, pancreas, liver, and gallbladder are the accessory organs of the digestive process. Saliva glands produce mucus and amylase which digests starch into simple sugars and binds food particles together, while lubricating the palette when one swallows. The pancreas produces amylase, lipases, and proteinases etc. These digestive juices are responsible for breaking down carbohydrates, proteins, and fats. The liver is the largest gland in the body, âIt produces bile salts to emulsify lipids. It detoxifies metabolic end products to protect the bodyâ (UXL Complete Health Resource). Gallbladder stores bile juice. The chicken in the General Tsoâs contains proteins. Proteins cannot be digested in mouth. However, the mouth can physically digest chicken into smaller pieces. These partially digested chicken pieces travel to stomach, where it is digested by pepsin. The pancreas produces trypsin, chymotrypsin, carboxypeptidases, lipases, and phospholipases (UXL Complete Health Resource). The chicken is then digested by trypsin, chymotrypsin, and carboxypeptidases in the duodenum of the small intestine. After the complete digestion, the chickenâs proteins change into amino acids, which are then absorbed into blood. The rice of the General Tsoâs is a carbohydrate. Carbohydrates are partially digested inside the mouth by amylase. The rest of the rice travels to the stomach where it is digested by pancreatic juices and enzymes that are produced by small intestine. The digestion of the rice produces monosaccharides that absorb into the blood stream. The left over, and undigested parts of the chicken and rice that are useless to the body are excreted by large intestine through rectum.

1) Based on your finding in the Module 3 Report, begin the Module 4 Report by identifying which metabolites are being absorbed and specifically which vessels of the cardiovascular or lymphatic system are the initial vessel of transport from the digestive system. 2) From the point that the specific metabolites are absorbed from the GI tract, trace the path of the resulting metabolites to the following locations in the body for incorporation into the body structure: Metabolites of protein for use in the Gastrocnemius muscle for muscle maintenance. Metabolites of the carbohydrates for energy to contract the cardiac muscle cells. Metabolites of fat to incorporate into the myelin sheaths of the Schwann cells of the Trigeminal nerve that innervates the Masseter muscle. Water for incorporation into the synovial fluid of the hip joint. Iron for incorporation into red blood cells in the bone marrow of the sternum.

maroonguinea-pig686

Food that we consume is composed of very complex molecules. During the digestive process these compounds are broken down into smaller and smaller subunits in preparation for use by the body as building blocks needed for the many components of the human body. The digestion process begins at the mouth. Food enters and then accessory digestive organs like the tongue, teeth, and salivary glands break down the substance. It then travels through the pharynx and esophagus into the stomach, where the stomach acid further breaks down the food (UXL Complete Health Resource). After that, the food travels through the small and large intestines where a majority of its nutrients are absorbed. The waste then exits through the end of the large intestine which is made up of the rectum and anus. After the teeth assist in chewing, food rolls over the tongue and reaches stomach through the esophagus within 8 seconds. General Tsoâs Chicken and Rice consist of carbohydrates, fats and proteins. However, carbohydrates are digested easily than the fats and proteins. After broken down in the stomach, most of the nutrients are absorbed from the small intestine, and it takes 6 to 8 hours to pass through small intestine. The remaining unabsorbed material, âmoves very slowly through the large intestine where the final absorption of water and other nutrients take placeâ (UXL Complete Health Resource). The parasympathetic nervous system encourages the food to move through the digestive tract and motivates digestion process. The sympathetic nervous system works against the parasympathetic nervous system by decreasing the contraction and relaxation of the digestive tract (Taylor). Mouth produces saliva, which contains amylase. Amylase is key in digesting carbohydrates. The stomach produces hydrochloric acid, pepsinogen, intrinsic factor, and mucus (Taylor). Hydrochloric acid kills the bacteria and other organisms that enter the stomach, and then continues to activate pepsinogen. Pepsinogen then changes into pepsin, which digests protein peptides. The pancreas produces trypsin, chymotrypsin, carboxypeptidases, lipases, and phospholipases. Trypsin, chymotrypsin, and carboxypeptidases digest proteins, whereas lipases, phospholipases digest lipid molecules. Small intestine produces lactase, sucrase, maltase, lipases, and peptidases. Lactase, sucrase, and maltase digest carbohydrates (UXL Complete Health Resource). Saliva glands, pancreas, liver, and gallbladder are the accessory organs of the digestive process. Saliva glands produce mucus and amylase which digests starch into simple sugars and binds food particles together, while lubricating the palette when one swallows. The pancreas produces amylase, lipases, and proteinases etc. These digestive juices are responsible for breaking down carbohydrates, proteins, and fats. The liver is the largest gland in the body, âIt produces bile salts to emulsify lipids. It detoxifies metabolic end products to protect the bodyâ (UXL Complete Health Resource). Gallbladder stores bile juice. The chicken in the General Tsoâs contains proteins. Proteins cannot be digested in mouth. However, the mouth can physically digest chicken into smaller pieces. These partially digested chicken pieces travel to stomach, where it is digested by pepsin. The pancreas produces trypsin, chymotrypsin, carboxypeptidases, lipases, and phospholipases (UXL Complete Health Resource). The chicken is then digested by trypsin, chymotrypsin, and carboxypeptidases in the duodenum of the small intestine. After the complete digestion, the chickenâs proteins change into amino acids, which are then absorbed into blood. The rice of the General Tsoâs is a carbohydrate. Carbohydrates are partially digested inside the mouth by amylase. The rest of the rice travels to the stomach where it is digested by pancreatic juices and enzymes that are produced by small intestine. The digestion of the rice produces monosaccharides that absorb into the blood stream. The left over, and undigested parts of the chicken and rice that are useless to the body are excreted by large intestine through rectum. 1) Based on your finding in the Module 3 Report, begin the Module 4 Report by identifying which metabolites are being absorbed and specifically which vessels of the cardiovascular or lymphatic system are the initial vessel of transport from the digestive system. 2) From the point that the specific metabolites are absorbed from the GI tract, trace the path of the resulting metabolites to the following locations in the body for incorporation into the body structure: Metabolites of protein for use in the Gastrocnemius muscle for muscle maintenance. Metabolites of the carbohydrates for energy to contract the cardiac muscle cells. Metabolites of fat to incorporate into the myelin sheaths of the Schwann cells of the Trigeminal nerve that innervates the Masseter muscle. Water for incorporation into the synovial fluid of the hip joint. Iron for incorporation into red blood cells in the bone marrow of the sternum.

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BISC 3221 Chapter Notes - Chapter 25: Sternocleidomastoid Muscle, Chyme, Vagus Nerve

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