Digestive System - Cloud Object Storage | Store &...
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Digestive System
Objectives1. Identify the organs of the digestive system, list their major functions, describe the
functional histology of the digestive tract, and outline the mechanisms that regulate digestion.
2. Discuss the anatomy of the oral cavity, and list the functions its major structures and regions.
3. Describe the structure and functions of the pharynx.4. Describe the structure and functions of the esophagus.5. Describe the anatomy of the stomach, including its histologic features, and
discuss its roles in digestion and absorption.6. Describe the anatomical and histological characteristics of the small intestine,
explain the functions and regulation of intestinal secretions, and describe the structure, functions, and regulation of the accessory digestive organs.
7. Describe the gross and histological structure of the large intestine, including its regional specializations and role in nutrient absorption.
8. List the nutrients required by the body, describe the chemical events responsible for the digestion of organic nutrients, and describe the mechanisms involved in the absorption of organic and inorganic nutrients.
9. Summarize the effects of aging on the digestive system.10. Give examples of interactions between the digestive system and the other organ
systems.
GI Tract - Overview
Alimentary Canal
Oral Cavity
Pharynx
Esophagus
Stomach
Small intestine
Duodenum
Jejunum
Ileum
Large intestine
Cecum
Colon
Ascending colon
Transverse colon
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Descending colon
Sigmoid colon
Rectum
Anal canal
Support Organs
Teeth
Tongue
Salivary Glands
Parotid
Submandibular
Sublingual
Liver
Gallbladder
Pancreas
vermiform appendix
Terms
Ingestion: taking food in
Mechanical Processing: e.g., mastication (chewing)
Digestion: breakdown of food
Secretion: release to lumen
Absorption: across digestive epithelium and into interstitial fluid
Excretion: removal of waste products from body fluids
Defecation: waste discharge
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Layers of GI Tract
Mucosa
Simple columnar
Secretive/ absorptive layer
Submucosa
Vascularized/ lacteal
Muscularis
Peristaltic movement
Inner circular and outer longitudinal
layers of smooth muscle
Serosa (adventitia in thorax)
Visceral peritoneum
Movement of Digestive Materials
Peristalsis
Segmentation
Control of Digestive Function
Neural Mechanisms
Myenteric plexus
Local reflexes
Short reflexes
Long Reflexes
Hormonal Mechanisms
Enteroendocrine cells
Local Mechanisms
Physical stimulation, pH,
chemical stimulation
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Serous Membranes
Parietal peritoneum
Dorsal mesentery
Ventral mesentery
Visceral peritoneum
Retroperitoneal
Mesenteries
Falciform ligament
Lesser omentum
Greater omentum
Peritoneal cavity
Oral Cavity
Lips
Vestibule
Teeth
Tongue
Papillae
Filiform
Fungiform
Vallate
Taste buds
Palate
Hard
Soft
Uvula
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Salivary Glands
Parotid, submandibular, sublingual
Ducts
Produce saliva
Cleans teeth
IgA kills oral bacteria
Digest starch (salivary amylase)
Lubricates: mucins
1-1.5 L per day
Mumps
Viral disease
Teeth
Heterodont dentition
Incisors
Canines (cuspids)
Premolars (bicuspids)
Molars
Tooth Structure
Disorders of Mouth and Teeth
Pharynx and Esophagus
Heartburn or acid reflux
GERD
Gastroesophageal Reflux
Disease
Hiatal hernia
Drugs
Mild
Acid-blockers, H2-receptor antagonists
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Tagamet
Zantac
Pepcid
Moderate to severe
Proton-pump inhibitors
Prilosec
Prevacid
Promotility agents
Reglan
Pharynx and Esophagus
Heartburn or acid reflux
GERD
Gastro-esophageal Reflux Disease
Hiatal hernia
Surgical treatments
Stretta Procedure
Bard endoscopic suturing system
Swallowing Process
Oral or Buccal phase
Pharyngeal phase
Esophageal phase
Upper sphincter
Lower sphincter
Clinical concerns
Achalasia
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Stomach
Functions:
Churn food w/gastric juice
Initiate protein digestion
Limited absorption
Move chyme to small intestine
Histology of the Stomach
Parietal Cells
Intrinsic factor
H2CO3 and Cl
Chief Cells
pepsinogen
Enteroendocrine Cells
Regulation of Gastric Activity
Cephalic Phase
Parasympathetic
Minutes
Gastric Phase
Neural response
Hormonal response
Local response
3-4 hours
Intestinal Phase
Neural response
Hormonal response
Disorders of Stomach
Gastroenterology
Gastritis
Anorexia
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Nausea
Emesis
Ulcer
Helicobacter pylori
Triple therapy
Bismuth subsalicylate
Tetracycline
Flagyl or Biaxin
Stomach cancer
Alcohol
Chewing tobacco
Smoked or heavily processed foods
Infants
Pylorospasm
Pyloric stenosis
LOWER DIGESTIVE SYSTEM
Small Intestine
Functions:
Reception of secretions from liver and pancreas
Chemical and mechanical breakdown
Absorption of nutrients
Transportation of undigested material to large intestine
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Small Intestine
Regions:
Duodenum
~25 cm (10 in.)
receives common bile duct
Jejunum
~2.5 m (8ft.)
Bulk of chemical digestion
Ileum
~3.6 m (12 ft.)
Structures of Small Intestine
Histology of Small Intestine
Mucosa
Intestinal villi
Brush border
Lacteal
Submucosal glands
Muscularis mucosae
Submucosa
Submucosal glands
Muscularis externa
Serosa
Submucosal glands
Submucosal lymphoid
Peyer’s Patches
Plicae
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Movement into Small Intestine
Submucosal glands increase in activity to protect duodenal epithelium from
gastric secretions
Local reflexes
Hormonal release
Parasympathetic response
Vagus nerve
Prepares the duodenum before acidic gastric contents are added
Pancreas
Endo- and exocrine functions
Pancreatic islets (Islets of
Langerhans)
Endocrine - glucogon, insulin,
somatostatin
Acini
Exocrine – controlled by hormones
from duodenum
Alkaline mixture of water ions and
digestive enzymes (trypsin, chymotrypsin,
etc.)
Hormones and Enzymes
Hormones controlling pancreatic secretions
Secretin- watery buffer raising pH.
Cholecystokinin- opens the hepatopancreatic sphincter and stimulates the
contraction of the gallbladder
Enzymes releases by pancreas (Cystic Fibrosis)
Pancreatic alpha-amylase
Pancreatic lipase
Nucleases
Proteolytic enzymes
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Enterokinase
Trypsinogen
Chymotrypsenogen
Procarboxypeptidase
Proelastase
Liver
Falciform ligament
Left lobe
Right lobe
Round ligament
Caudate lobe
Quadrate lobe
Hilus
Liver
Hepatic Lobules
Hepatocytes
Hepatic triads
Hepatic portal branch
Hepatic artery
Bile duct branch
Kupffer cells (stellate
reticuloendothelial cells)
Liver
Functions:
Metabolic Regulation
Carbohydrate Metabolism
Lipid Metabolism
Amino Acid Metabolism
Removal of Wastes
Vitamin Storage
Mineral Storage
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Drug inactivation
Hematological Regulation
Phagocytosis and Antigen presentation
Synthesis of Plasma Proteins
Removal of Hormones, Antibodies and Toxins
Synthesis and secretion of Bile
Bile
Emulsifies fat
Lipases unable to break down large droplets
Form chylomicrons (micelles)
Diffuse across cell membranes and enter cytoplasm, then are secreted by
exocytosis and are eventually taken up by lacteals
Lacteals drain into lymphatic system and triglycerides enter blood stream at
subclavian vein via the thoracic duct.
Then reach liver for processing
Gallbladder
Stores and
concentrates bile
Gallstones
solid crystals of insoluble minerals and salts
Release of bile controlled by CCK
Coordination of Secretion
Neural Mechanisms
Preparing the digestive tract for activity
(parasympathetic) or inhibiting gastrointestinal activity (sympathetic)
Coordinating the movement of materials along the length of the digestive tract
(reflexes)
Hormonal Mechanisms
Secretin: increases the secretion of bile and buffers by the liver and pancreas
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Cholecystokinin (CCK): accelerates the production of digestive enzymes in
pancreas and relaxes the hepatopancreatic sphincter and contraction of the gallbladder
Gastric Inhibitory Peptide (GIP): stimulates lipid synthesis in adipose tissue and
increases glucose usage by skeletal muscles
Large Intestine
Regions:
Cecum--appendix--ascending colon
Hepatic flexure--transverse colon
Splenic flexure
Descending colon
Sigmoid colon
Rectum
Function:
Absorb water, electrolytes
Absorb vitamins released by
bacteria
Pass waste to rectum and storage
~1.5 m (5 ft.)
Large Intestine
Absorption in Large Intestine
Water
9000 mL ingested or secreted – 150mL lost in feces
Bile salts
Recycled in liver
Vitamins
Vitamin K – fat soluable – clotting factors
Biotin – water soluable – glucose metabolism
Vitamin B3 – water soluable – steroid hormone and neurotransmitter production
Histology of Large Intestine
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Mucosa
Columnar cells
Goblet cells
Intestinal gland
Muscularis mucosae
Submucosa
Muscularis externa
Serosa
Anal Canal
Rectal valve
Internal sphincter
External sphincter
Pectinate line
Keratinized
Disorders of GI Tract
Peptic ulcers
Diarrhea
Hiatal hernia
Diverticulitis
Stomach cancer
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Metabolism and Energetics
Objectives: 1. Define metabolism, and explain why cells must synthesize new organic
components.2. Describe the basic steps in glycolysis, the TCA cycle, and the electron transport
system, and summarize the energy yields of glycolysis and cellular respiration.3. Describe the pathways involved in lipid metabolism, and summarize the
mechanisms of lipid transport and distribution.4. Summarize the main processes of protein metabolism, and discuss the use of
proteins as an energy source.5. Differentiate between the absorptive and postabsorptive metabolic states, and
summarize the characteristics of each.6. Explain what constitutes a balanced diet and why such a diet is important.7. Define metabolic rate, discuss the factors involved in determining an individual’s
BMR, and discuss the homeostatic mechanisms that maintain a constant body temperature.
Terms to know
Anabolic reactions
Glycogenesis
Gluconeogenesis
Lipogenesis
Protein synthesis
Catabolic reactions
Glycogenolysis
Glycolysis
Lipolysis
Protein degradation
Deamination
Nutrient Use in Cellular Metabolism
Remember
Glycolysis, Kreb’s cycle (TCA-tricarboxylic cycle or citric acid cycle) and the
Electron Transport System: a series of reactions that convert one molecule of glucose to 6
molecules of water, 12 molecules of carbon dioxide and 38 molecules of ATP.
Fat-soluble vitamins: includes Vitamins A, D, E and K
Water-soluble vitamins: includes all the B vitamins and vitamin C
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BMR (basal metabolic rate)
Metabolism and Eating Disorders
Anorexia nervosa
Bulimia
Obesity
Protein-calorie malnutrition
Marasmus
Kwashiorkor
The New Food Pyramid
Basic Nutrients
Carbohydrates: sugars
Fats: lipids, fatty acids, glycerol
Proteins: amino acids
Mineral salts: inorganic ions released from disassociation of electrolytes
Vitamins: fat and water soluble
Water
Minerals
Functions
Determine Osmotic Concentration of body fluids
Major roles in important physiological processes
Membrane transport
Action potential generation
Maintain skeleton
Neurotransmitter and hormone production and release
Cofactors in a variety of enzymatic reactions
Glycolysis-ATP production
Gastric acid secretion
Minerals
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Bulk Minerals
Sodium
Potassium
Chloride
Calcium
Phosphorus
Magnesium
Trace Minerals
Iron
Zinc
Copper
Manganese
Cobalt
Selenium
Chromium
Vitamins
Fat-soluble
A: maintains epithelia, required to synthesize visual pigments, immunity, bone
health
D: bone growth, calcium and phosphorus absorption in intestine
E: prevents breakdown of vitamin A and fatty acids
K: essential for liver synthesis of prothrombin and clotting factors
Water-soluble
B1 (thiamine): coenzyme in decarboxylations
B2 (riboflavin): part of Kreb’s cycle
Niacin: part of Kreb’s cycle
B5 (pantothenic acid): parts of Kreb’s cycle
B6 (pyridoxine): coenzyme in amino acid and lipid metabolism
Folacin (folic acid): coenzyme in amino acid and nucleic acid metabolism
B12 (cobalamin): coenzyme in nucleic acid metabolism
Biotin: coenzyme in decarboxylations
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C9ascorbic acid): coenzyme, delivers hydrogen ions, antioxidant
Aging and The Digestive System
The rate of epithelial stem cell division decreases
Smooth muscle tone decreases
The effects of cumulative damage become apparent
Cancer rates increase
Changes in other systems have direct or indirect effects on the digestive system
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