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Homeostasis wk7. Lecture 6. pt1

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winniesmith1's version from 2017-05-30 13:52

Section 1

Question Answer
What are the 6 functions of the digestive system1. ingestion. 2. Mechanical processing. 3. Digestion (chemical breakdown). 4.Secretion -GI tract epithelia and organs release water, acids, enzymes, buffers, salts. 5.Absorption- Of organic substrates, electrolytes, vitamins and water across digestive epithelia into intersitial fluid. 6. Excretion.
What is ingestionoccurs when materials enter digestive tract via the mouth.
What is mechanical processingcrushing and shearing, makes materials easier to propel along digestive tract.
What is digestionThe chemical breakdown of food into small organic fragments for absorption by digestive epithelium
What is secretionIs the release of water, acids, enzymes, buffers, and salts by epithelium of digestive tract & glandular organs
What is absorptionMovement of organic substrates, electrolytes, vitamins, and water Across digestive epithelium Into interstitial fluid of digestive tract
What is excretionRemoval of waste products from body fluids Process called defecation removes faeces
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Section 2

Question Answer
what are the major subdivisions of the digestive tract.(gastro-intestinal tract)(aka alimentary canal, muscular tube). -Oral cavity, teeth, tongue. -Pharynx. -Oesophagus. -Stomach. -Small intestine. -Large intestine,
What happens in the oral cavity (teeth, tongue)Mechanical processing, moistening, salivary secretions.
What happens in the pharynxPropulsion
What happens in the oesophagusTransport of materials to the stomach
What happens in the stomachChemical breakdown; mechanical processing
What happens in the small intestineEnzymatic digestion and absorption
What happens in the large intestineEnzymatic digestion and absorption.
What are the accessory organs of the digestive systemSalivary glands (secretion of saliva). Liver (secretion of bile / many other functions) Gall bladder (storage of bile) Pancreas (secretion of buffers and enzymes).
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Section 3

Question Answer
Peritoneum, Serous membrane lining abdominal cavity; describe+mesothelium covering areolar tissues -Visceral and parietal layers +Peritoneal fluid -7l/day produced; provides lubrication to allow sliding
Describe mesenteries-Suspend portions of digestive tract -Mesothelial surfaces surrounding areolar tissue allowing passage of blood vessels, nerves and lymphatic vessels
What does the lining of the digestive tract safeguard against:-Digestive acids and enzymes -Mechanical stresses -Bacteria
What are the 4 major layers of the digestive tract (histological organisation)1. Mucosa. (muscularis mucosae) 2. Submucosa. 3. Muscularis externa. 4. Serosa.
What is the mucosa made up ofMucosal epithelium and lamina propria
Describe the mucosal epithelium-Stratified squamous epithelium in oral cavity, pharynx & oesophagus -Simple columnar with mucous cells elsewhere
Describe the lamina propriaAreolar tissue with blood and lymphatic vessels and nerve endings
Describe the muscularis mucoaeHas -Inner circular layer -Outer longitudinal layer
Describe the digestive tract submucosa+Layer of dense, irregular connective tissue.
+Surrounds muscularis mucosae.
+Has large blood vessels and lymphatic vessels.
+May contain exocrine glands:
-Secrete buffers and enzymes into digestive tract.
+Submucosal Plexus (plexus of Meissner):
-Innervates the mucosa and submucosa.
Contains:
Sensory neurons, Parasympathetic ganglionic neurons, Sympathetic postganglionic fibers .
Describe the digestive tract muscularis externa+Smooth muscle cells: -Inner circular layer -Outer longitudinal layer +Movements coordinated by enteric nervous system (ENS) -Sensory neurons, Interneurons and Motor neurons -innervated primarily by parasympathetic division of ANS (Sympathetic postganglionic fibers The mucosa The myenteric plexus (plexus of Auerbach))
Describe the digestive tract Serosa-Serous membrane covering muscularis externa in most of digestve tract -Adventitia, (dense sheath of collagen fibers, firmly attaches the digestive tract to adjacent structures in oral cavity, pharynx, oesophagus, and rectum
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Section 4

Question Answer
Describe movement of digestive materials: Muscular layers of digestive tract-Smooth muscle tissue: Rhythmic cycles of activity controlled by pacesetter cells: Located in muscularis mucosae and muscularis externa. -Cells undergo spontaneous depolarization: Triggering wave of contraction through entire muscular sheet
Describe movement of digestive materials: Peristalsis-Waves of muscular contractions
Describe movement of digestive materials: Segmentation-Cycles of contraction, does not follow a set pattern.
Describe the stages of peristalsis1. contraction of circular muscles behind bolus. 2. Contraction of longitudinal muscles ahead of bolus. 3. Contrition in circular muscle layer forces bolus forward.
Regulation of digestion1. local factors. 2. Neural control mechanisms. 3. Hormonal control mechanisms.
Describe local factorsRespond to changes in pH, physical distortion or chemicals.Prostaglandins, histamine, and other chemicals released into interstitial fluid. May affect adjacent cells within small segment of digestive tract. Coordinate response to changing conditions. For example, variations in local pH, chemical, or physical stimuli. Affect only a portion of tract
Describe neural control mechanismsShort reflexes: triggered by chemoreceptors or stretch recepters. Long reflexes: involve CNS. May involve parasympathetic motor fibres
Describe short reflexestriggered by chemoreceptors or stretch receptors. Are responsible for local reflexes. Control small segments of digestive tract. Operate entirely outside of CNS control. Sensory neurons, Motor neurons, Interneurons.
Describe long reflexes: involve CNS. May involve parasympathetic motor fibres.
Higher level control of digestive and glandular activities.
Control large-scale peristaltic waves.
Involve interneurons and motor neurons in CNS.
May involve parasympathetic motor fibers that synapse in the myenteric plexus Glossopharyngeal, vagus, or pelvic nerves .
Describe hormonal control mechanisms18 peptides produced by enteroendocrine cells
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Section 5

Question Answer
Describe the functions of the oral cavity-Sensory analysis -Mechanical processing -Lubrication -Limited digestion of carbohydrates and lipids
Describe the functions of the tongue-Mechanical processing -Manipulation -Sensory analysis: touch, temperature, and taste receptors -Secretion of mucins and the enzyme lingual lipase
Describe the functions of saliva-Lubricating the mouth and contents -Dissolving chemicals -Initiating digestion of complex carbohydrates by salivary amylase
Describe the salivary glands -Parotid salivary glands: Serous secretion, contains salivary amylase. -Sublingual salivary glands: Mucous secretion, act as buffer and lubricant. -Submandibular salivary glands: Secrete buffers, glycoproteins, salivary amylase
How much saliva is produced per day-1.0–1.5 liters of saliva produced each day: 70% by submandibular, 25% by parotids, 5% by sublingual glands.
Describe saliva content-99.4% water -0.6% includes: Electrolytes (Na+, Cl, and HCO3), Buffers, Glycoproteins (mucins), Antibodies, Enzymes, Waste products.
Describe control of salivary secretions-Parasympathetic and sympathetic innervation -Salivatory nuclei in medulla oblongata
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