Digestive
Digestive System
Anatomy
Physiology
Alimentary Canal (Gastrointestinal (GI) tract)
Accessory
Teeth
Tongue
Gallbladder
Digestive Glands
Salivary Glands
Liver
Pancreas
Digestive
Ingestion
Propulsion
Mechanical Breakdown
Digestion
Absorption
Defecation
Eating
Moving of food through alimentary canal
Swallowing
Peristalsis
Propulsion of food involving alternating waves of contraction and relaxation
Chewing, mixing foods with saliva by the tongue, churning of food in stomach, segmentation.
Segmentation
rhythmic local contractions of the small intestine that mixes food with digestive juices; also efficient absorption
series of catabolic steps that involves enzymes breaking down complex food molecules into chemical building blocks
Passage of digested end products from lumen of GI tract into blood or lymph
vitamins, minerals, and water
elimination. of indigestible substances via anus in. form. of feces
Abdominal Cavity
Peritoneum
Visceral
Parietal
membrane on external surface of most digestive organs
membrane that lines body wall
Peritoneal Cavity
contains serous fluid which allows mobility of digestive organs to glide across each other against body wall
Mesentary
Intraperitoneal Organs
Stomach, most of small intestine and parts of large intestine
Retroperitoneal Organs
Pancreas, Duodenum, and parts of large intestine
Functions
holds organs in place and also stores fat
provides routes for blood vessels, lymphatic and nerves
double layer of peritoneum
extends from body wall to digestive organs
Mesentaries
Greater Omentum
Lesser Omentum
Falciform Ligament
Mesentary Proper
Mesocolon
Secures parts of large intestine to posterior abdominal wall
Suspends most of small intestine from posterior abdominal wall
drapes inferiorly. from the greater curvature of the stomach
liver to the lesser curvature of the stomach
suspends liver from diaphragm and anterior abdominal wall
Organs
Small Intestine
Esophagus
Mouth (Oral (Buccal) Cavity)
Pharynx
Stomach
Anus
Histology of Alimentary Canal
Layers
Mucosa
Submucosa
Muscularis
Serosa
Characteristics
Functions
Secretion, Absorption, Protect against infection
innermost layer of lumen
Simple Columnar Epithelium
In mouth, esophagus, and anus
stratified squamous epithelium
MALT
Characterisics
consists of areolar connective tissue
contains blood and lymphatic vessels
Abundant elastic tissues that help organs to regain shape after storing large meal
Characteristics
smooth muscle layer for segmentation and peristalsis
inner circular muscle layer and outer longitudinal layers
contains sphincters
Characteristics
outermost layer
replaced by adventitia in esophagus
dense. connective tissue
Functions
Ingests
mechanical breakdown by chewing
initiates propulsion by swallowing
starts the digestion of polysaccharides
Characteristics
Palate
Tongue
Filiform Papillae
Forms roof of mouth
Hard Palate
Soft Palate
mucosa is to help create friction against tongue
closes off nasopharynx during swallowing with help of downward projecting uvula
Functions
Gripping, repositioning, and mixing food during chewing
Forms Bolus: mixture of food and saliva
initiates swallowing and aids in speech and sense of taste
Gives tongue roughness to provide friction: only one that does not contain taste buds, gives tongue a whitish appearance
Saliva
Minor (Intrinsic) Glands
Major (extrinsic) Glands
Secretory Cells
Parotid
Submandibular
Sublingual
Serous Cells
Mucous Cells
Functions
initiates swallowing and aids in speech and sense of taste
Gripping, repositioning, and mixing food during chewing
Forms Bolus: mixture of food and saliva
Functions
Allows passage of food, fluids and air
Stratified squamous epithelium lining with mucus-producing glands
functions
is flat muscular tube that runs from laryngopharynx to stomach.
is collapsed when not involved in food propulsion
temporary storage tank that starts chemical breakdown of protein digestion.
converts bolus of food to paste-like chyme
Anatomy
Gastric Gland Cells
Parietal Cells
Chief Cells
Enteroendocrine
Secrete Hydrochloric acid
denatures protein, activates pepsin, breaks down plant cell walls & kills many bacteria
secrete pepsinogen
inactive enzyme that is activated by pepsin by hydrochloric acid & by pepsin itself
secrete chemical messengers some paracrines while others are hormones
Mucosal Barrier
protects stomach from harsh conditions & is created by 3 factors
Thick layer of bicarbonate- rich mucus
Digestive Process
Serves as holding area for food
Propulsion
mechanical breakdown
digestion
absorption
intrinsic factor
required intestial absorption of vitamin b12
B12 needed for RBC to mature
Lack of intrinsic factor causes pernicious anemia
treated with B12 injections or nasal gel
Gastric Secretion
Cephalic (reflex) phase
Gastric Phase
Triggered by aroma, taste, sight and thought
stimulate gastric glands
inhibited by loss of appetite and depression
stimulated by distension, peptides, and low acidity
activates stretch receptors, initiating both long. and short reflexes
Partially digested proteins activate enteroendocrine G cells to secrete gastrin
Release of gastrin initiates HCL release from parietal cells
binds to receptors on parietal cells
stimulates eneteroendocrine cells to release histamine
inhibited by excessive acidity in stomach & emotional stress
Low pH inhibits gastrin secretion
stress, fear, etc
Intestinal Phase
stimulated by partially digested food in small intestine
causes small release of intestinal gastrin
inhibited by duodenum of
distension or presence of acidic, fatty , or hypertonic chyme
enterogastric reflex
duodenum inhibits. acid secretion in stomach by short and long reflexes
enterogastrones
duodenal enteroendocrine cells release 2 important hormones that inhibit gastric secretion
secretin
cholecystokinin
Regulation of Gastric Motility & Emptying
Filling
Stretches to accommodate incoming food
Gastric contractile activity (gastric mixing)
Gastric Emptying
enteric pacemaker cells
distension and gastrin increase force of contraction
duodenum can prevent overfilling by. controlling the amount of chyme enters
digestive function is production of bile
Anatomy
4 primary lobes
Falciform ligament
round ligament
blood enters through hepatic artery and hepatic portal vein and enter liver at porta hepatis
Liver Lobules
Portal Triad
Liver Sinusoids
Stellate macrophages
Hepatocytes filter and process nutrient- rich blood
Central vein
hepatic artery supplies oxygen
hepatic portal vein brings nutrient rich blood from intestines
Bile duct receives bile from bile canaliculi
blood from hepatic portal vein & hepatic artery proper goes through sinusoids and empties into central vein
in liver sinusoids and remove debris and old RBC's
Bile
Bile salts
Bilirubin
cholestrol
function in fat emulsification and absorption
pigment from heme
broken down by bacteria in intestine to stercobilin
Functions
store and concentrate bile by absorbing water & ions
contractions of muscle release bile through cystic duct then flows into bile duct
Functions
Exocrine
Endocrine
secrete pancreatic juice through duct
Acini contains secretory cells that produce zymogen granules that contain proenzymes
secretion of insulin and glucagon by pancreatic islet cells
Composed of watery alkaline solution
elcetrolytes
Proteases (trypsin)
Amylase (carbohydrates)
Lipases (lipids)
Nucleases (nucleic acids)
Large Intestine
Characteristics
Major organ of digestion and absorption
Duodenum
Jejunum
Ileum
circular folds
villi
microvilli
Histology
Function
modifications of mucosa and submucosa reflect function in digestion
Intestinal crypts
Cells
Enterocytes
Tubular glands scattered between villi
Goblet Cells
Enteroendocrine
Paneth
absorb nutrients and elctrocytes and produce intestinal juice
mucus-secreting cells
source of enterogastrones
secrete antimicrobial agents
Peyers patches
Duodenal glands
Characteristics
Teniae Coli
Haustra
Cecum
Appendix
Colon
Rectum
Anal Canal
MALT
Ascending, Transverse, Descending
Sigmoid
Rectal valves
Contains thicker mucosa
Simple Columnar epithelium, except anal canal carries stratified squamous epithelium
Digestive Process
Residue remains in large intestine 12-24 hrs
Motility of large intestine
Mass movements
Defecation Reflex
Digestive Process
Chyme from stomach has partially digested carbohydrates, proteins and undigested fats 3-6 hrs
Sources of enzymes fro digestion such as bile, bicarbonate, digestive enzymes
Regulating chyme entry has to be slow to prevent osmotic loss of water from blood
Motility of small intestine mechanical breakdown, propulsion
Ileocecal valve control opens and enter chyme to large intestine
Intrinsic & accessory gland enzymes are involved in digestion
enzymes carry out hydrolysis
tight junctions ensure molecules pass through epithelial cell and not pass through between
most nutrients are absorbed by active transport processes driven by ATP
Carbohydrates
only monosaccharides can be absorbed
starch and disaccharides are broken down to oligosaccharides & disaccharides through salivary amylase
broken down into lactose, maltose and sucrose
final broken into glucose, fructose, galactose
Proteins
Large polypeptides
Small polypeptides & small peptides
Amino acid monomers
pepsinogen converted to pepsin
pancreatic proteases
brush border enzymes
cleave protein into smaller peptides
break oligopeptides & dipeptides into amino acids
Lipids
Emulsification
Digestion
Pancreatic lipases
fatty acids
monoglycerides
Micelle formation
Diffusion
Nucleic Acids
pancreatic nucleases
nucleotide monomers
brush border enzymes
Vitamins
Small intestine
Large intestine
Fat soluble vitamins A, D, E, K
Water soluble vitamins C, B
Vitamins K and B
removal of gall bladder also known as cholecystectomy.
when using of a feeding tube solids need to be blended to liquid to enter into the tube
Gallbladder stores bile and removal of gallbladder would be due to gallstones or other problems associated with the gallbladder such as infection , etc
stomach cancer in most causes develop mutation of DNA and grows rapidly and spreads which eventually will lead to cancer cells and then formation of a tumor
symptoms of stomach cancer
fatugue
heartburn
stomach pain
continuously vomiting
severe indigestant
Inmost stomach cancers patients do get a feeding tube inserted for the purpose of maintaining their diet and health,
the feeding tube also does help bypass any other implications that may worsen with the cancer
treatments for cancer include radiotherapy and chemotherapy which target cancer cells
this also targets rapidly dividing GI tract epithelium
lack of motility of intestines is common in elderly patients this affects the movement of bile and other items to move in the gastrointestinal tract
elderly patients most likely would need to be monitored frequently especially when taking their meal.
most preparations need to be recommended through the doctor such as food that might cause acid reflex or stomach pains such as spicy food may not be allowed.
even medications and vitamins are taken through the tube in liquid form in order to stay healthy
most foods, liquids will be in tube feeding formula. but not medications.
it is important to keep the tube clean as it may cause bacteria to stay inside the tube which can cause the patient to become sick.
to efficiently keep the tube clean is to ensure before and after meals to insert warm water to get rid of any bacteria or leftover liquids.
in some cases the tube can get blocked if formula or liquid is too thick but this can be easily taken care of by using warm water or calling the patients doctor.
without the gallbladder there will be no storage for the bile it passes on to the liver which will then release into small intestine, making it possible for food to be received and flow towards the rectum
Nervous system Control
Intrinsic controls
Extrinsic Controls
Short Reflexes
Long reflexes
occur entirely within the gastrointestinal wall
involve the CNS