Digestive System (Digestive enzymes (Brush border enzymes- embedded within…
salivary amaylase- synthesized and released from the salivary glands, breaks down the chemical bond between glucose molecules within the starch molecule
trypsinogen, chymotrypsinogen, procarboxy- continue the digestion of proteins in the small intestine. they are synthesized and released from the pancreas into the small intestine in inactive form
pancreatic amylase- synthesized and released by the pancreas as a component of pancreatic juice into the small intestine, continues digestion of starch
- produced by the pancreas and released into the guodenum. digests each triglyceride into a monoglyceride and 2 free fatty acids
deoxyribonuclease and ribonuclease
- synthesized and released by the pancreas
Brush border enzymes
- embedded within the epithelial lining of the small intestine
Sucrase- digests lactose to glucose and galactose
Lactase- digests lactose to glucose and galactose
dextrinase and glucoamylase- break the bonds between glucose subunits of oligosaccharides
maltase- break the bond between the two glucose molecules that compose maltose
Dipeptidase- breaks final bond between the two amino acid of a dipeptide so that both may be absorbed
Aminopeptidase- generates free amino acides from the amino ends of peptides
- breaks bond between the sugar and the nitrogen base of a nucloside
- breaks the bond holding the phosphate to the rest of the nucleotide
- synthesized by the small ntestine and released into the lumen of the small intestine. activates trypsinogen into
- activates chymotrypsinogen ito
and procarboxypeptidase into
Trypsin and chymotrypsin break the bonds between specific amio acids into smaller ones called peptides
pepsin- synthesized by the chief cells in the stomach, denatures proteins to facilitate their chemical breakdown.
- limited digestion of triglycerides into diglyceride and fatty acid
- produced by salivary glands. activated once it reaches the stomach
- produced by chief cells of the stomach
- begins within the stomach lumen by pepsin and continues in the small intestine. the amino acids from proteins are absorbed through the intestinal villi walls of the small intestine.
- limited digestion in the stomach, majority of lipid digestion occurs in the small intestine. absorbed in the small intestine as well
- digestion of starch begins in the oral cavity, in the small intestine pancreatic amylase continues the starch breakdown. brush border enzymes continue the breakdown process. they are absorbed in the small intestine
- digestion occurs in the small intestine. Absorbed across the epithelium of the small intestine into the blood.
Tunics of the GI Tract
- mix and propel the contents within the GI tract
Outer longitudinal layer
- smooth muscle cells oriented lengthwise
Peristalsis- coordinated contraction and relaxation of the muscularis layer to propel materials through the lumen
Mixing- any type of muscular contraction that facilitates the blending of materials, lacks directional movement
Myenteric nerve plexus
- the axons and ganglia located between the inner and outer smooth muscle layers that control their contractions.
Enteric nervous system
- composed of both the submucosal nerve plexus and the myenteric nerve plexus. have both sensory and motor neurons of the autonomic nervous system
Inner circular layer
- smooth muscle cells oriented circumferentially around the GI tract.
- Thickened area that closes off the lumen to control the movement of materials into the next section of the GI tract
- composed of areolar and dense irregular connective tissue. contain many lymph vessels, large blood vessels, and nerves.
Submucosal nerve plexus/Meissner plexus
- Fine branches of the nerves extended into the mucosa along with their associated ganglia. They innervate both smooth muscle and glands of the mucosa and submucosa
Serosa or Adventitia
- outer most tunic.adventitiais composed of areolar connective tissue with dispersed collagen and elastic fibers. serosa is the same but its completely covered by visceral peritoneum
- inner-lining mucous membrane
- this layer contains areolar connective tissue. Substances are absorbed into the blood or lymphatic capillaries located within the lamina propria
- thin layer of smooth muscle deep to the lamina propria. contractions in this layer cause slight movements in the mucosa which can "shake things up" and activate secretions into the lumen
- in contact with the contents within the lumen. It is mostly simple columnar epithelium except for parts of the GI tract that must withstand abrasion, those parts are nonkeratinized stratified squamous epithelium. This tissues functions are for secretion and absorption.
Organs of the GI Tract
- 3 parts: duodenum, jejunum, and the ileum. function is to mix chime with accessory gland secretions and move contents toward the large intestine
- cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and the rectum.continues absorption, primarily of water, electrolytes, and vitamins. bacteria act on remaining undigested material.
- muscular J-shaped organ where mechanical and (mostly) chemical digestion continues on the bolus. release of gastric secretions and formation of chyme
- the digestive process is completed as feces is produced and eliminated through the anus
- involuntary phase of swallowing, 10 inch tubular passageway, superior and inferior esophageal sphincters relax to allow bolus to pass through, after bolus passes the inferior sphincter contracts to prevent reflux
- involuntary phase of swallowing, funnel shaped muscular passage way for both air and food.
- entrance to the GI tract, initial process of mechanical and chemical digestion, voluntary phase of swallowing
Accessory digestive organs
- moistens ingested food to help it become a bolus, initiates chemical breakdown of starch
- synthesizes bile to facilitate mechanical digestion of triglycerides
Teeth and Tongue
- participate in chewing/mastication and swallowing of food
- exocrine cells secrete pancreatic enzymes. Pancreatic juice assists with digestive activities
- concentrates and stores the secretions of the liver (bile)