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An elderly man has stomach cancer, he's had his gallbladder removed,…

- - - - For carbohydrate
    - - For proteins
      - Cleave proteins into smaller peptides
    - - For lipids
      - Break down fat (triglycerides) into free fatty acids and monoglycerides
    - - For nucleic acids
      - Hydrolyze nucleic acids to nucleotides monomers
  - - - Carbohydrates: further break them into lacrose, maltose, and sucrose, and then into monosaccharides
      - Proteins: break oligopeptides and dipeptides into amino acids
- - - - Only monosaccharides can be absorbed
      - Starch and disaccharides are broken down to oligosaccharides and disaccharides
      - Further broken down into lactose, maltose, and sucrose
      - Final breakdown into monosaccharides (glucose, fructose, and galactose)
      - Steps of starch digestion in intestines
        
        Pancreatic amylase
        
        Brush border enzyme
    - - Source of proteins is not only dietary, but also includes digestive enzyme and proteins from breakdown of mucosal cells
      - Proteins are broken down into:
        
        Small polypeptides and small peptides
        
        Large polypeptides
        
        Finally into amino acid monomers, with some dipeptides and tripeptides
      - Digestions begins in stomach when pepsinogen is converted to pepsin at pH 1.5-2.5
      - Steps of protein digestion in intestines
        
        Pancreatic protease
        
        Brush border enzyme
    - - Steps in lipid digestion in intestines
        
        Emulsification: triglycerides and their breakdown products are insoluble in water
        
        Digestion: pancreatic lipases break down fat into free fatty acids and monoglycerides
        
        Micelle formation: products from digestion become coated with bile salts
        
        Diffusion: lipid products leave the micelles and cross epithelial membrane via diffusion
        
        Lipid products are converted back into triglycerides and enter lymphatic lacteal
        
        Eventually emptied into varies blood at thoracic duct
      - Short-chain fatty acids can diffuse directly into blood
    - - Nuclei of ingested cells in food contain DNA and RNA
        
        Pancreatic nucleases
        
        Brush border enzymes: break nucleotides down into free nitrogenous bases, pentose sugars, and phosphate ions
  - - - In small intestines:
        
        In fat soluble vitamins (A, D, E, K) carried by micelles absorbed by diffusion
        
        Water soluble vitamins (B, C) are absorbed by active or passive transport
        
        Vitamin B12 binds with intrinsic factor and is absorbed by endocytosis
      - In large intestines: vitamin K and D from bacterial metabolism are absorbed
    - - Most ions are transported actively along small intestines
      - Usually amount in intestines is the amount absorbed
      - Iron and calcium are exceptions as absorptions is related to need
        
        Ionic iron is stored in muscle cells with protein ferritin
        
        When needed transported in blood by plasma protein transferrin
        
        Calcium absorption regulated by vitamin D and PTH
    - - ~ 9 L of water, most from GI tract, secretion enters small intestines
      - 95% absorbed in small intestines, and the rest in large intstines
      - Water uptake occurs via osmosis
- - - - Buccal phase: voluntary contraction of tongue
        
        Pushes food bolus into the oropharynx
      - Pharyngeal-esophageal phase: involuntary phase controlled by the swallowing center in brain stem
        
        Once food enters pharynx, respiration is momentarily inhibited
        
        Talking or inhaling while swallowing can short-circuit these protective mechanisms, and food may enter enter respiratory passageway instead
  - - - Serves as a holding area for food
      - Exhibits peristalsis (propulsion) to deliver chyme to small intestines
      - Carries out the mechanical breakdown of food thanks to churning action
      - Protein digestion begins in stomach
        
        Pepsin carries out enzyme digestion of proteins
        
        HCl denature (unfolds) proteins
      - Lipid-soluble alcohol, aspirin, and some other drugs are absorbed into blood
      - Only stomach function essential for life is secretion of intrinsic factor
        
        Required intestinal absorption of vitamin B12
        
        B12 needed for RBC to mature
        
        Lack of intrinsic factor cause pernicious anemia
        
        Treated with B12 injections or nasal gel
  - - - Bile: yellow-green, alkaline solution containing:
        
        Bile salts: cholesterol derivatives, functions in fat emulsification and absorption
        
        Bilirubin: pigment formed from heme, broken down by bacteria in intestine to stercobilin that gives brown color of feces
        
        Cholesterol, triglycerides, phospholipids, and electrolytes
      - Enterohepatic circulation: recycling mechanism that conserves bile salts
        
        Bile salts are reabsorbed into blood by ileum and returned to liver via hepatic portal blood
        
        ~ 95% of secreted bile salts are recycled each time
  - - - Acini: cluster of secretory cells that produce zymogen granules containing proenzyme (inactive digestive enzymes)
  - - - Takes 3-6 hours in small intestines to absorb all nutrients and water
    - - Brush border enzymes bound to plasma membrane perform final digestion of chyme
    - - Chyme entering duodenum is usually hypertonic; therefore, chyme delivery is slow to prevent osmotic loss of water from blood
      - Low pH chyme has to be adjusted upward
      - Chyme has to be mixed with bile and pancreatic juice to continue digestion
      - Enterogastric reflex and enterogastrones control movement of food into duodenum to prevent it from being overwhelmed
    - - After a meal, segmentation is most common motion
        
        Mixes chyme with pancreatic and brush border enzymes and bile
      - Between meals, peristaltic waves are initiated every 90-120 minutes
        
        Meal remnants, bacteria, and debris are moved to large intestines
        
        Complete trip from duodenum to ileum take ~ 2 hours
  - - - No food breakdown occurs except when enteric bacteria digests
      - Absorb vitamins made by bacterial flora, water, and electrolytes
      - Major functions of large intestines is propulsion of feces to anus and defecation
    - - Mass movements: slow powerful peristaltic waves activated 3-4 times per day
        
        Gastrocolic reflex (initiated by presence of food in stomach) and amount of fiber increases the strength of contractions
      - descending colon and sigmoid colon act as a storage reservoir
    - - Parasympathetic stimulate contraction of the sigmoid colon and rectum and relaxation of the internal anal sphincter
      - Conscious controls relaxation of external anal sphincter, and muscle of rectum contract to expel feces
      - Assisted by Valsalva's maneuver
      - Involuntary defecation occurs in infants because they have not yet gained control of their external anal sphincter
- - - - Palate: forms the roof of mouth and has 2 distinct parts
        
        Hard palate: formed by palatine bones and palatine process of maxillae
        
        Soft palate: formed by mostly skeletal muscle, closes off nasopharynx during swallowing with help of uvula
      - Tongue: composed of interlacing bundles of skeletal muscle
        
        Filiform papillae: gives tongue roughness to provide friction
    - - Produces saliva
      - Minor (intrinsic) salivary glands
        
        Scattered throughout oral cavity
        
        Enough to keep the mouth moist all day
      - Major (extrinsic) salivary glands: produces most of saliva, located outside of oral cavity
        
        Parotid: anterior to ear and external to masseter muscle
        
        Submandibular: medial to body of mandible
        
        Sublingual: anterior to submandibular glands under tongue
      - 2 types of secretory cells:
        
        Serous cell: produce watery secretions, enzymes, ions, and a bit of mucin
        
        Mucous cells: produce mucus which lubricates oral cavity and hydrates foodstuff
    - - Lie in sockets in gum covered margins of mandible and maxilla
      - Primary dentition consist of 20 deciduous teeth; and 32 deep lying permanent teeth are under them. When they enlarge and develop, it causes deciduous teeth to loosen and fall out
      - Classified according to shape
        
        Incisors: chisel shape for cutting
        
        Canines: fang like teeth that tear or pierce
        
        Premolars: broad crown with rounded cusps used to grind or crush
        
        Molars: broad crowns, rounded cusps: best grinders
      - Tooth structure
        
        2 major regions:
        
        Crown: exported part above gum, covered by enamel
        
        Root; portion embedded in jawbone
        
        Cement: calcified connective tissue that covers root
        
        Periodontal ligaments: forms a fibrous joint called gumphosis
        
        Dentin: bone like material under enamel
        
        Pulp cavity: surrounded by dentin; contains blood vessels and nerve
        
        Root canal: extension of pulp cavity into root
    - - a thin-walled muscular sac on ventral surface of liver
      - Contains many honeycomb folds that allow it to expand and fill
  - - - Food passes from mouth into oropharynx then into laryngopharynx
        
        Stratified squamous epithelium lining with mucus-producing glands
        
        External muscle layer consists of 2 skeletal muscle layers
        
        Inner layer of muscle runs longitudinally
        
        Outer pharyngeal constrictors encircle wall of pharynx
      - Esophagus: a flat muscular that runs from laryngopharynx to stomach
        
        Pierces diaphragm and joins stomach at cardial orifice
        
        Gastroesophageal sphincter: surrounds cardial orifice
        
        Keeps closed off when food isn't being swallowed
        
        4 Layers
        
        Esophageal mucosa contains stratified squamous epithelium
        
        Submucosa has mucus secreting esophageal glands that aid in food passage
        
        Muscularis: skeletal superiorly; mixed in middle; smooth inferiorly
        
        has adventitia instead of serosa
    - - A temporary storage that starts chemical breakdown of protein digestion
      - Empty stomach hads ~50 mL volume but can expand to 4 L
      - Major regions:
        
        Cardial region: surrounds cardial orifice
        
        Fundus: Dome-shaped region beneath diaphragm
        
        Body: the midportion
        
        Pyloric region: terminates in pylorus, which is continuous with duodenum through pyloric valve
        
        Greater curvature: convex lateral surface of stomach
        
        Lesser curvature: concave medial surface of stomach
      - Mesenteries extend from curvature and tether stomach to other digestive organs
        
        Lesser omentum: runs from lesser curvature to liver
        
        Greater omentum: drapes inferiorly from greater curvature over intestines,spleen, transverse colon
        
        Blends with mesocolon
        
        Contains fat deposits and lymph nodes
      - Stomach wall contains regular 4 tunics, however, muscularis and mucosa are modified
        
        Muscularis has extra third level, the oblique level
        
        Mucosa consists of simple columnar epithelium entirely composed of mucous cells
      - Mucosal barrier: protects stomach from harsh condition and is created by 3 factors:
        
        Thick layer of bicarbonate-rich mucus
        
        Tight junctions between epithelial cells prevent juice seeping underneath tissue
        
        Damaged epithelial cells are quickly replaced by diffusion of stem cells
    - - Gross anatomy of liver
        
        Largest gland in body ~ 3 lbs
        
        Consists of 4 primary lobes: left, right, caudate, and quadate
        
        Falciform ligament: separates larger right and smaller left lobes
        
        Round ligament; remnant of fetal umbilical vein along free edge of falciform ligament
        
        Blood enters through hepatic artery and hepatic portal veins, which enter liver at porta hepatis
        
        Ducts transporting bile include common hepatic duct leaving the liver which unties the cystic duct from the gallbladder to form the bile duct
      - Microscopic anatomy of liver
        
        Liver lobules: hexagonal structural and functional units
        
        Composed of plates of hepatocytes (liver cells) that filter and process nutrient-rich blood
        
        Central vein located in longitudinal axis
        
        Portal triad in each corner of lolube contains:
        
        Branch of hepatic artery, which supplies oxygen
        
        Branch of hepatic portal vein, which brings nutrient-rich blood from intestines
        
        Bile duct, which receives bile from bile canaliculi
        
        Liver sinusoid: leaky capillaries located between hepatic plates
        
        Has stellate macrophages: removes debris and old RBC
    - - Location: Mostly retroperitoneal deep to greater curvature of stomach with head encircled by C-shaped duodenum and tail next to spleen
      - Bile duct and pancreatic duct unite in wall of duodenum
        
        Fuse together in bulblike structure called hepatopancreatic ampulla
      - Ampulla opens into duodenum via major duodenal papilla
      - Hepatopancreatic sphincter controls entry of bile and pancreatic juice into duodenum
    - - Gross anatomy of small intestines
        
        7-13 ft from pyloric sphincter to ileocecal valve, point at which it joins to large intestines
        
        Subdivisions:
        
        Duodenum: mostly retroperitoneal, ~10 inches long; curves around head of pancreas
        
        Jejunum: ~ 8ft long; attached posteriorly by mesentery
        
        Ileum: ~ 12ft long; attached posteriorly by mesentery; joins large intestine at ileocecal valve
      - Microscopic anatomy of small intestines
        
        Structural modifications of small infection for absorption
        
        Its length and other modifications provide huge surface area for nutrient absorption
        
        Circular folds: permanent folds that force chyme to slowly spiral through lumen
        
        Villi: fingerlike projections of mucosa with a core that contains dense capillary beds and a lymphatic capillary called a lacteal for absorption
        
        Microvilli: cytoplasmic extensions of mucosal cells that give a fuzzy apperance called the brush border
        
        Histology of small intestine walls
        
        Intestinal crypts: tubular glands scattered between villi
        
        Mucosa associated lymphatic tissue (MALT) protects against microorganisms
        
        Peyer's patch: located in mucosa of ileum and extended into submucosa
        
        Submucosa consists of areolar tissue:
        
        Duodenal glands in the submucosa of the duodenum secrete alkaline mucus to neutralize acidic chyme
        
        Main type of cells found in villi and crypts:
        
        Enterocytes: make up bulk of epithelium
        
        In villi: absorb nutrients and electrolytes
        
        In crypts: produce intestinal juices
        
        Goblet cells: mucus-secreting cells
        
        Enteroendocrine cell: source of enterogastrones
        
        Panetin cells: secrete antimicrobial agents
    - - Gross anatomy of large intestines
        
        Unique features of large intestines
        
        Teniae coli: 3 bands of longitudinal smooth muscle in muscularis
        
        Haustra: pocketlike sacs caused by tone of teniae coli
        
        Subdivisions:
        
        Cecum: first part of large intestines
        
        Appendix: contains masses of lymphoid tissue, part of MALT, immune system
        
        Bacterial storehouse capable of recolonizing gut
        
        Twisted shape makes it susceptible to blockage
        
        Colon: several regions, most are retroperitoneal
        
        Ascending,transverse, and descending colon travels up the right side, across and down the left side of the abdominal cavity
        
        Sigmoid colon: S-shaped portion that travels through pelvis
        
        Rectum: 3 rectal valves stop feces from being pass with gas
        
        Anal cavity: last segment that opens to body exterior at anus; has 2 sphincter
        
        Internal (smooth muscle) and external anal sphincter (skeletal muscle)
        
        Relationship of large intestines to peritoneum
        
        Cecum and appendix, and rectum are all retroperitoneal
        
        Colon is also retroperitoneal, except for transverse and sigmoid part
        
        Intraperitoneal regions anchored to posterior abdominal wall by mesocolons
      - Microscopic anatomy of large intestines
        
        Large intestines contains thicker mucosa made up of simple columnar epithelium
        
        Except in anal canal, where it becomes stratified squamous epithelium
        
        Doesn't contain circular folds, villi, or digestive secretions
        
        Contains abundant deep crypts with many mucus-producing goblet cells