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An elderly patient suffering from stomach cancer (Background Information…
An elderly patient suffering from stomach cancer
Background Information
Anatomy of digestive tract
Organs of digestive tract
Alimentary canal (GI tract)
Stomach
Temporary storage tank that starts chemical breakdown
Has 50ml volume and can reach up to 4L
Regions of stomach
Body
Mid portion
Pyloric region
Terminates in pylorus
Fundus
Beneath diaphragm a dome shaped region
Greater curvature
Convex lateral surface of stomach
Cardinal region
Encircles cardial orifice
Lesser curvature
Concave medial surface of stomach
Gross anatomy of stomach
Microscopic anatomy of stomach
Composed of gastric glands
Chief cells
Secrete pepsinogen
Enteroendocrine cells
Secrete chemical messengers
Parietal cells
Secrete hydrochloric acid
Mucosal barrier
Protection of stomach from harsh conditions
Three factors
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Small intestine
Major organ of digestion and absorption
Subdivisons
Jejunum
8ft long, attached posteriorly by mesentery
Ileum
12ft long, joins large intestine at ileocecal valve
Duodenum
10.0 in long, retroperitoneal
Microscopic anatomy
Provide huge surface area for absorption of nutrients
Structural modifications for absorption
Surface area can be increased upto 600x to ~200m2
Villi
Fingerlike projections of mucosa(~1mm high)
Circular folds
Permanent folds (~1cm deep)
Microvilli
Cytoplasmic extensions of mucosal cells that gives fuzzy appearance called
brush border
Histology of small Intestine
"
Digestion" reflects modifications of mucosa and submucosa
Intestinal crypts
:tubular glands between villi
Goblet cells
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Enteroendocrine
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Enterocytes
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Paneth cells
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Esophagus
Esophagus is a flat tube that runs from laryngopharynx to stomach
Has all four layers unlike mouth and pharynx
Submucosa
Muscularis
Mucosa
Serosa
Large intestine
Gross anatomy
Large intestine has unique features
Teniae coli
3 bands of longitudinal smooth muscle
Haustra
Pocket like sacs caused by teniae coli
Subdivisions
Colon
Retroperitoneal regions(except for its transverse and sigmoid regions)
Rectum
Three rectal valves that stop feces from passing with gas
Appendix
Masses of lymphoid tissue
Anal canal
Last segment that opens to body exterior at anus
Cecum
First part of large intestine
Microscopic anatomy
Large intestine contains thicker mucus(simple columnar epithelium) except in anal canal it changes into stratified squamous epithelium
Has no circular folds, villi and digestive secretions
Has deep crypts with mucus-producing goblet cells
Pharynx
External muscle layer
Internal layer runs longitudinally
Outer layer encircles walls of pharynx
Startified squamous epithelium
Allow food, fluids and air to pass
Mouth
Digestion of polysaccharides
Begin impulse by swallowing
Starts breakdown of chewing
Ingests
Also known as oral cavity
Surrounded by lips, palate, cheeks and tongue
Palate:
Roof of the mouth
Soft palate
Formed by skeletal muscle
Hard palate
Formed by palatine bones and processes
Tongue
Interweaving bundles of skeletal muscle
Functions
Repositioning
Mixing of food during chewing
Gripping
Filiform papillae
Roughness to tongue, no taste buds and gives whitish appearance
Histology of Ailmentary canal
Submucosa
Areolar connective tissue
Contains blood and lymphatic vessels
Abundant elastic tissues that help organs to regain shape
Serosa
Outermost layer made of visceral peritoneum
Retroperitoneal organs have both an adventitia and a serosa
Replaced by adventitia in esophagus
Adventitia
Dense connective tissue, hold esophagus
Mucosa
Contains lymphoid follicles that defend against microorganisms
Simple columnar epithelium
Innermost layer that lines the lumen
Functions
Absorption
Protection
Secretion
Muscularis
Inner circular muscle layer and outer longitudinal layer
Spinchters
Thick circular areas acting as valves
Smooth muscle layer responsible for segmentation and peristalsis
Accessory digestive organs
Tongue
Interlacing bundles of skeletal muscles
Functions
Repositioning
Chewing
Gripping
Bolus
Mixture of food and saliva
Filiform papillae
Provide friction
Gall bladder
Ventral surface of liver
Functions
Store and concentrate bile by absorbing water and ions
Release bile through cystic duct(flows into bile duct)
Contain many honeycombs
Teeth
Gum covered margins of mandible and maxilla
Classification of teeth
Canines
Fanglike teeth that tear
Premolars
For grinding and crushing
Incisors
Chisel shape for cutting
Molars
Broad crowns and best grinders
Nutrients in human body
Proteins
Amino acid
Lipids
Fatty acid
Carbohydrates
Monosaccharides
Nucleic acid
DNA and RNA
Enzymes for nutrient digestion
Proteins
Brush border enzymes
Break oligopeptides and dipeptides into amino acids
Pancreatic amylase
Cleave protein into smaller peptides
Lipids
Pancreatic lipases
Breaks down fat into fatty acid and monoglycerides
Carbohydrates
Brush border enzymes
Further break these into lactose, maltose, and sucrose; and then into monosaccharides (glucose, fructose, galactose)
Pancreatic amylase
Breaks down starch or glycogen that escaped salivary amylase into oligosaccharides and disaccharides
Nucleic acid
Pancreatic amylase
Hydrolyze nucleic acid to nucleotide monomers
Brush border enzymes
Break nucleotides down into free nitrogenous bases, pentose sugars, and phosphate ions
Physiology of each organ
Digestive process of stomach
Mechanical breakdown
Protein digestion
Exhibits peristalsis
Absorption of Lipid soluble alcohol, drugs and aspirin in blood**
Holding area of food
Secretion of intrinsic factor
Digestive processes in small intestine
Chyme from stomach contains partially digested carbohydrates and proteins and undigested fats
Enzymes for digestion:bile, bicarbonate, digestive enzymes(imported from liver and pancreas)
Regulates chyme entry
Ileocecal valve control opens and admits chyme into large intestine
Motility of small intestine
After meal
Segmentation
Before meal
Propulsion
Digestive tract of large intestine
Residue in large intestine
Absorbs vitamin
Propulsion of feces to anus and defecation
No digestion
Defecation reflex
Mass movements making feces move towards rectum
Motility of large intestine
Mass movements
Activation of Slow, powerful peristaltic waves
Gastrocolic reflex and amount of fiber increase the strength of contractions
Descending colon and sigmoid colon act as storage reservoir
Digestive process of Mouth
Pharynx and esophagus are conduits to pass food from mouth to stomach
Propulsion(starts with deglutition)
Involves 22 muscle groups and two phases
Buccal phase
Voluntary contraction of tongue
Pharyngeal-esophageal phase
Involuntary phase controlled by the swallowing center in the brain stem
Downstream effects
The nutrients digested and absorbed by these organs will impact the food he will be given because he will not have these nutrients
He need to be provided with proteins, carbohydrates and fatty acids in his feeding tube to get adequately nutrients
Digestive processes of stomach, esophagus and small intestine did not occur
Causes
All bypassed organs are not able to participate in digestive processes
Glucogen, aminoacids, fattyacids are the enzymes not added to the food
The stomach, esophagus and duodenum are being bypassed
Gross anatomy